fix: scan-root error propagation, link_target leak, delta guard, meta leak (review)

- Transport I/O vtable over TCP/TLS; TLS multithreaded sendfile fixed
- Symlink-xattr wire block (protocol 2.29.0; config frame unchanged)
- No-wire parity burn-down: --inc-recursive, in-root --temp-dir,
  --delete-before phase-0, rsync-interoperable --fake-super, --devices
  per-entry failure, rsyncd.conf key subset (read-only default)
- Protocol version: 2.29.0
- Tested: unit, integration, ASan, UBSan, valgrind, differential parity

.gitignore

@@ -12,3 +12,12 @@ build_docker2/
 # Test/run artifacts
 root/
 test_partial_install_tmp/
+
+# Editor/tooling + test caches/artifacts
+.pytest_cache/
+*.gcda
+*.gcno
+*.gcov
+di/
+test_data-manual/
+*.log

.opencode/skills/release/SKILL.md

@@ -16,7 +16,7 @@ Ask the user or determine from context:
 - **Minor** (x.Y.0) — new features, backward compatible
 - **Patch** (x.y.Z) — bug fixes, no protocol changes
 
-Current version: `PROTOCOL_VERSION "2.26.0"` in `src/shared/config.h`
+Current version: `PROTOCOL_VERSION "2.29.0"` in `src/shared/config.h`
 
 ### Step 2: Check Protocol Version
 

AGENTS.md

@@ -4,9 +4,9 @@ FastSync is a high-performance file synchronization system written in C11. It su
 
 ## Dependency installation
 
-**CI rule:** never add `apt-get install` / `pip install` steps to CI workflows — use the custom Docker image instead. The image is built from the repo-root `Dockerfile` and is the same image CI uses: `gitea.tap-tap.win/taptap/fastsync-ci:v11`. It contains the full toolchain: gcc/g++, CMake, libzstd-dev, libssl-dev, make, git, cppcheck, clang-format, python3 + pytest + pytest-xdist, openssh-client, Node.js, plus `rsync` 3.4.1 (with zstd/xxhash/lz4), `acl` and `attr` (setfacl/getfacl, setfattr/getfattr) for drop-in parity tests.
+**CI rule:** never add `apt-get install` / `pip install` steps to CI workflows — use the custom Docker image instead. The image is built from the repo-root `Dockerfile` and is the same image CI uses: `gitea.tap-tap.win/taptap/fastsync-ci:v11`. It contains the full toolchain: gcc/g++, CMake, libzstd-dev, zlib1g-dev, liblz4-dev, libxxhash-dev, libssl-dev, make, git, cppcheck, clang-format, python3 + pytest + pytest-xdist, openssh-client, Node.js, plus `rsync` 3.4.1 (with zstd/xxhash/lz4), `acl` and `attr` (setfacl/getfacl, setfattr/getfattr) for drop-in parity tests. (CMake hard-requires zstd, zlib, and lz4; xxHash is fetched via `FetchContent`.)
 
-**Host rule:** for local development, use `nix-shell` (see `README.md`) which provides zstd, OpenSSL, CMake, and gcc. The Docker image can also be used locally for CI parity.
+**Host rule:** for local development, use `nix-shell` (see `README.md`) which provides zstd, zlib, lz4, OpenSSL, CMake, and gcc. The Docker image can also be used locally for CI parity.
 
 ```bash
 # Use the prebuilt CI image directly (faster, guaranteed CI parity)
@@ -38,11 +38,12 @@ If a dependency is missing from the CI image, add it to the `Dockerfile` (and re
 When configuring for CI parity, use:
 ```bash
 cmake -B build -S . -DSTRICT_WARNINGS=ON        # -Wextra -Wpedantic -Werror
-cmake -B build -S . -DSANITIZER=address           # AddressSanitizer (ASan)
-cmake -B build -S . -DSANITIZER=thread            # ThreadSanitizer (TSan)
+cmake -B build -S . -DSANITIZER=address           # AddressSanitizer (ASan); in the CI matrix
+cmake -B build -S . -DSANITIZER=undefined         # UndefinedBehaviorSanitizer (UBSan); in the CI matrix
+cmake -B build -S . -DSANITIZER=thread            # ThreadSanitizer (TSan); local-only, NOT in CI
 ```
 
-The CI workflow (`.gitea/workflows/ci.yaml`) runs lint (clang-format, cppcheck), then a **fast PR gate** — build + unit + a representative subset of integration tests marked `@pytest.mark.ci`, parallelized with pytest-xdist (`-n 4 --dist=load`). The full coverage jobs (full integration suite as `-m "not setpriv"`, sanitizer, fuzz, coverage, valgrind) run **only on push to `dev`/`main`**; pull requests skip them to keep PR CI under ~3 minutes. The two `setpriv` privilege tests are excluded from CI via a marker because their result depends on the runner/container uid and host mount permissions.
+The CI workflow (`.gitea/workflows/ci.yaml`) runs lint (clang-format, cppcheck), then a **fast PR gate** — build + unit + a representative subset of integration tests marked `@pytest.mark.ci`, parallelized with pytest-xdist (`-n 4 --dist=load`). The full coverage jobs (full integration suite as `-m "not setpriv"`, the `address`+`undefined` sanitizer matrix, fuzz, coverage, valgrind) run **only on push to `dev`/`main`**; pull requests skip them to keep PR CI under ~3 minutes. TSan is not part of the CI matrix and is a local-only configuration. The `setpriv`-marked privilege tests (four decorated functions, collecting to eight instances because two are parametrized) are excluded from CI via a marker because their result depends on the runner/container uid and host mount permissions.
 
 ## Build
 
@@ -105,7 +106,7 @@ Two main branches: `dev` (integration) and `main` (stable releases).
 
 ### Rules
 - **All PRs target `dev`** — never target `main` directly
-- **`dev` is the default branch** in Gitea repo settings
+- **`dev` is intended to be the default branch** in Gitea repo settings — verify in the repo settings, since this clone's `origin/HEAD` still points at `main`
 - **`main` is protected** — only merged from `dev` via PR with 2 approvals + full CI pass
 - **Feature/bug branches** branch from `dev`, PR back to `dev`
 - **`dev` → `main` merges** happen on-demand or weekly, requiring full CI + review

CHANGELOG.md

@@ -4,6 +4,238 @@ All notable changes to FastSync are documented here. Versions match
 `PROTOCOL_VERSION` (printed by `fastsync --version`); the client and server must
 run the same version because the handshake is strict.
 
+## [Unreleased]
+
+Wire backlog cycle (protocol 2.29.0 → 2.30.0; config-frame layout unchanged).
+
+- **`--stderr=client` client-message channel (#313):** the client now accepts
+  `--stderr=client` (and maps the deprecated `--no-msgs2stderr` to it), routing
+  its own diagnostics over the new bounded `STATUS_CLIENT_MSG` client->server
+  frame instead of writing them locally; the server writes each received
+  message to its stderr (respecting the server log destination).  `errors`/`all`
+  behavior is unchanged.
+- **Receiver partial failures exit 23 (#320):** a per-entry receiver failure
+  that does not abort the stream (e.g. an unprivileged `--devices` mknod) now
+  sends the terminal `STATUS_PARTIAL`; the client exits 23 like rsync and, under
+  `--remove-source-files`, still removes the sources it successfully
+  transferred.  A clean run stays 0 and a fatal/connection error stays non-23.
+- **Directory/symlink destination-state itemize (#314):** when `report_dest_info`
+  is negotiated (now also for `--progress`), the receiver answers `STATUS_MKDIR`
+  and `STATUS_SYMLINK` with the entry's pre-transfer destination snapshot
+  (existence, type, perms/owner/group/time, and whether an existing symlink's
+  target already matches), and the sender probes every ancestor directory before
+  the receiver creates it implicitly.  A re-run over an unchanged tree no longer
+  emits per-directory `cd+++++++++` or unchanged-symlink lines, a changed
+  directory renders rsync's `.d..t......`, and a changed symlink renders
+  `cLc........` / `.L..t......`.  Directory/symlink time comparison uses whole
+  seconds (rsync's `cmp_time`).  The `STATUS_MKDIR` body gains a probe flag and
+  the `STATUS_DEST_INFO` record gains a symlink-target-match field; the
+  config-frame layout is unchanged.  Differential-tested against rsync 3.4.1.
+- **`--stats` deleted per-type breakdown (#316):** `STATUS_STATS` gains
+  `deleted_reg/dir/link/special`, tallied by the delete observers and rendered
+  as rsync's `Number of deleted files: X (reg: A, dir: B, link: C, special: D)`.
+  Differential-tested against rsync 3.4.1 for a mixed-type `--delete` tree.
+
+## [2.29.0] - 2026-09-23
+
+The rsync-parity cycle 2.29 (no wire change; `PROTOCOL_VERSION` stays 2.28.0).
+`RSYNC_COMPAT.md` moves from **116 ✅ / 14 ⚠️ / 27 ❌** to
+**120 ✅ / 10 ⚠️ / 27 ❌** of 157 rows.
+
+An audit cycle follows on the same wire version (`PROTOCOL_VERSION` stays
+2.28.0): a security-and-correctness pass over the parity-2.29 baseline, plus a
+set of audit follow-ups (filter merge modifiers, the `--inplace`/`--partial-dir`
+conflict, credential-file hardening, and small leak/log/test fixes). It fixes
+a `--temp-dir` symlink escape, gates client-controlled special permission bits,
+corrects `--partial-dir`/`--bwlimit`/`-z` behavior, handles unsupported filter
+modifiers, and tightens client and wire validation. The only parity
+reclassification is `--filter=RULE` moving ✅ → ⚠️, because its merge-only
+`e`/`n`/`w`/`-` modifiers are now accepted and consumed but their semantics
+remain unimplemented (accepted-but-ignored); the matrix is therefore **119 ✅ /
+11 ⚠️ / 27 ❌** of 157 rows. The affected rows' notes and the summary tally in
+`RSYNC_COMPAT.md` were updated. A following triage-fix cycle (see **Triage
+fixes** below) moves `-F` and `-i` to ⚠️, for a final **117 ✅ / 13 ⚠️ / 27 ❌**
+of 157 rows.
+
+A no-wire parity burn-down cycle follows on 2.28.0: it accepts
+`--inc-recursive`/`--no-inc-recursive` as inert no-ops, accepts an absolute
+`--temp-dir` that canonicalizes inside the receive root, closes the
+`--delete-before` phase-0 divergence (both the single-threaded and `--threads`
+data passes replay the pre-scan list), makes `--fake-super` interoperable with
+rsync's `user.rsync.%stat` key/grammar (regular files and char/block devices
+faked as regular files), turns a failed device `mknod` into a continuing
+per-entry failure, and accepts a practical subset of rsync's `rsyncd.conf`
+grammar (modules are read-only by default, and accepted-but-unenforced
+access-control keys emit a startup warning). The matrix moves to **119 ✅ /
+14 ⚠️ / 24 ❌** of 157 rows.
+
+A structural cycle then lands a transport I/O vtable over TCP/TLS (fixing the
+TLS-multithreaded sendfile path and making the per-thread SSL resolution
+explicit) and bumps the wire to **2.29.0**: the `STATUS_SYMLINK` frame grows an
+optional symlink-xattr block (captured no-follow with `llistxattr`/`lgetxattr`,
+applied no-follow with `lsetxattr`). Because the handshake is strict, 2.28.0 and
+2.29.0 peers are incompatible. Note: Linux refuses to associate xattrs with a
+symlink at all, so the symlink-xattr block is a no-op on Linux and is carried
+for correctness on platforms/filesystems that do support it; the config-frame
+layout is unchanged (golden length still 886).
+
+### Changed
+
+- **rsync-exact traversal order.** The sequential scanner now walks each
+  directory's entries in rsync 3.4.1's flist order (non-directories ascending,
+  then directories ascending, depth-first), so `--info=name`, the
+  `--delete-during`/`--delete-delay`/`-n` would-delete order and the partial
+  `--max-delete` survivor set match rsync byte-for-byte. `--threads` has no
+  rsync analogue and stays unordered.
+- **Delete timing.** The complete `--delete-during`/`--delete-delay`
+  per-directory plan set is transmitted before the first data frame, so a
+  mid-transfer abort has already removed every planned extra like rsync's
+  generator; `-d/--dirs` uses per-directory plans (shielded untraversed
+  subdirectories) instead of the end-of-transfer commit. `-n`, `--delete`,
+  `--del`/`--delete-during` and `--delete-delay` are now ✅ Parity.
+- **Basis directories.** A relative `--compare-dest`/`--copy-dest`/`--link-dest`
+  DIR resolves against the destination directory with the transfer-relative
+  name appended, exactly like rsync 3.4.1.
+- **`-y`/`--fuzzy`.** The candidate search no longer inherits the ordinary delta
+  engine's 16 KiB minimum or 10× size-ratio bound, so an oversized or
+  sub-16-KiB sibling is reused exactly as rsync reuses it.
+- `--info=mount` prints rsync's mount-point skip line (repeated `-xx` drops the
+  mount-point directory); `--info=stats` enables the `--stats` block; `-x` is
+  repeatable. `--stats` counts traversed directories for the `Number of files`
+  breakdown under a plain `-r` scan. `--debug` emits real output for
+  `flist`/`del`/`hash`/`deltasum`/`recv`/`filter`/`send`.
+
+### Known residuals
+
+- `--progress` and `--info` still need a receiver→sender event channel for the
+  root `./` line, ancestor-directory suppression, receiver-side `skip`/`backup`
+  wording, and symlink/empty-directory quick-checks.
+- `--delete-before`'s phase-0 late-file divergence remains (rsync's pre-scan
+  fixes the file list before the data pass).
+- A whole-file sender that cannot stream its codec (lz4's one-shot block
+  format) or a `--append`/delta source above the bound still buffers; the
+  default zstd/zlib and the uncompressed paths stream (see #318).
+- `--stats` byte totals and `--msgs2stderr` stay documented divergences.
+
+### Security
+
+- **`--temp-dir` symlink escape fixed.** The receiver's scratch directory was
+  opened with a bare `open()`, so a symlink planted under the receive root could
+  redirect receiver scratch files outside the authorized root. The opened
+  directory is now judged by the real path of its fd (`/proc/self/fd` via
+  `realpath`) and an escaping target is refused (`EACCES`, logged); an in-root
+  link to another filesystem (the `EXDEV` fallback case) still works.
+- **Client-controlled special bits masked when super-user activities are not
+  permitted.** Setuid/setgid/sticky bits (`--perms`, `--chmod`, the symlink and
+  special-node paths, and deferred directory modes) are now stripped when the
+  connection forbids super activities (`--no-super`, a non-opted daemon module,
+  a privileged listener without `--allow-super`); exact rsync semantics are
+  preserved wherever super activities are permitted.
+- **Daemon umask no longer forced to `0`.** `daemonize()` now sets the
+  conventional `022`, so implied parent directories created without `-p` are no
+  longer world-writable `0777`.
+- **Daemon modules are read-only by default.** A `--daemon` module is now
+  served read-only unless it sets `read only = no` (or rsync's `write only =
+  yes`), matching rsync: a real `rsyncd.conf` that omits `read only` is no
+  longer silently writable. A global `read only` still sets the default for
+  later modules, and an explicit module value wins. This is a behavior change
+  for existing FastSync-native configs that relied on the old writable default;
+  add `read only = no` to keep them writable. An rsync `write only = yes` is
+  mapped to writability (FastSync is push-only, so a module can never be read
+  from the network).
+- **Accepted-but-unenforced rsync security keys now warn at startup.** The
+  rsync keys FastSync recognizes but does not implement — `secrets file`,
+  `refuse options`, `exclude`/`include`/`filter`, `max size`/`min size`,
+  `pre-xfer exec`/`post-xfer exec`, `incoming chmod`/`outgoing chmod`,
+  `name converter`, `use chroot`, `uid`/`gid`, and the rest of the
+  access-control set — load for migration compatibility but now emit a
+  `WARN` naming the key (and module) so an operator does not believe the
+  restriction is enforced. `auth users`/`secrets file` stay fail-closed: a
+  module declaring `auth users` still requires a FastSync credential store.
+- **Credentials and signal handling hardened.** Secret files are opened with
+  `O_NOFOLLOW|O_NONBLOCK` (while allowing fd-backed store paths and bound-waiting
+  a FIFO read for ~3 s so a slow process substitution works but a connected-but-
+  silent FIFO cannot hang), and signal handlers use `sigaction` with
+  async-signal-safe bodies.
+
+### Fixed
+
+- **`-z` on 100–256 MiB files.** The decompressor's internal ceiling was 100 MiB
+  while the receiver advertises and the sender compresses whole files up to
+  `MAX_RECEIVE_WHOLE_FILE_SIZE` (256 MiB), so `-z` on a 100–256 MiB regular file
+  failed with `Declared decompressed size exceeds 104857600 bytes`. The ceiling
+  is now defined in terms of the protocol whole-file bound (still an
+  allocation-clamped bomb guard).
+- **`--bwlimit` now paces `--sendfile`.** The plaintext-TCP `--sendfile` fast
+  path bypassed the protocol's token bucket, so the limit was ignored there. It
+  now throttles through the same per-session leaky bucket as the TLS path.
+- **`--partial-dir` implies `--partial`.** Matching rsync 3.4.1 (which sets
+  `keep_partial` after option parsing), `--partial-dir=DIR` alone retains an
+  interrupted transfer's partial and wins over an explicit `--no-partial`;
+  `--inplace` still bypasses the partial machinery, and combining `--inplace`
+  with `--partial-dir` is now rejected up front with rsync's message
+  (`--inplace cannot be used with --partial-dir`).
+- **Filter modifiers handled.** The `x` xattr-name modifier is rejected with a
+  clear error everywhere. The merge-only `e`/`n`/`w` and `-` modifiers are now
+  accepted and consumed on `merge`/`dir-merge` rules (so they no longer leak
+  into the merge filename) while still being rejected on non-merge rules,
+  matching rsync; their semantics remain unimplemented (accepted-but-ignored).
+  Glued patterns (`-newfile`, `-e2e`) and mixed tokens (`H,!secret`) keep their
+  historical parsing.
+- **Credential-file reads hardened.** Secret files (`--password-file`/
+  `--early-input`/`--hash-credentials` input) are opened with `O_NOFOLLOW`, so a
+  symlinked credential path now fails closed (`ELOOP`) instead of being followed
+  before the owner/mode gate; literal fd-backed paths (`/dev/fd/<digits>`,
+  `/proc/self/fd/<digits>`) are exempt so process substitution still works. A
+  FIFO/process-substitution read now waits under a bounded ~3 s deadline for its
+  writer, so a slow producer works while a connected-but-silent FIFO fails
+  instead of hanging.
+- **Miscellaneous correctness fixes:** `--filter` rule count is checked
+  client-side against `MAX_FILTER_RULES` before any network I/O (the receiver
+  still re-checks the expanded count); unknown wire `Status` values are rejected
+  as protocol errors; a mutex leak on an init-failure path, an `errno` read
+  after `free()` in deferred delete application, `log_perror` misuse for
+  non-`errno` conditions, and a `NULL` `server_host`/`ssh_destination`
+  allocation path were fixed (the `config_create` failure now releases through
+  `config_delete`); the decompression-limit log now prints the effective bound
+  rather than the compile-time ceiling; the daemon umask and root test fixtures
+  were hardened; `SSL_read` length is clamped and `sendfile` `poll()` retries on
+  `EINTR`.
+
+### Refactored / Docs
+
+- Dropped dead `filter_rules_apply` and dead `--old-args` plumbing, unified
+  `set_error`, deduplicated `path_is_within` and shared constants, and added
+  printf format attributes (fixing format mismatches). `RSYNC_COMPAT.md`,
+  `CHANGELOG.md` and `HANDOFF.md` were updated for the audit cycle; the
+  `RSYNC_COMPAT.md` summary tally was corrected to match the rows.
+
+### Triage fixes
+
+- **`--dirs` directory xattrs applied inline.** A `-d/--dirs` transfer now
+  applies captured directory `-X`/`-A` xattrs fd-relative on the directory entry
+  instead of dropping them, so directory xattrs survive the non-recursive path
+  (`src/shared/file_save.c`, `tests/test_xattr.c`).
+- **Directory/root itemize and `--out-format` lines.** `-i`/`--itemize-changes`
+  and `--out-format` now emit the transfer-root `./` line and per-directory
+  `cd...`/`.d..t...` lines, rendered by the shared itemize code. This matches
+  rsync's fresh-transfer output; because the root line is unconditional and an
+  incremental re-run may itemize directories/symlinks that rsync's quick-check
+  leaves silent, `-i` is now a ⚠️ Caveat row.
+- **FROM name globs for identity maps.** `--usermap`/`--groupmap` `FROM` tokens
+  now accept `*`/`?`/`[...]` globs, expanded sender-side against the passwd/group
+  database and collapsed into bounded numeric ranges (`MAX_IDENTITY_MAP`),
+  matching rsync.
+- **Transport fallback unit tests.** Added unit coverage for the TCP/TLS
+  transport fallback paths (`tests/test_transport_tcp.c`,
+  `tests/test_transport_tls.c`).
+- **Docs corrections.** `RSYNC_COMPAT.md`/`README.md` corrected stale parity
+  claims for issues #286–#297: the `-F` and `-i` reclassifications, the
+  `--munge-links` direction, the accepted checksum/compression name sets,
+  `--bwlimit` parsing, `--stop-at` grammar, `--trust-sender`, symlink xattrs, and
+  the native/non-interoperable batch and credential notes. The summary tally is
+  now **117 ✅ / 13 ⚠️ / 27 ❌** of 157 rows.
+
 ## [2.28.0] - 2026-09-20
 
 The rsync-parity cycle. `PROTOCOL_VERSION` moves `2.26.0 → 2.27.0 → 2.28.0`;

CMakeLists.txt

@@ -1,6 +1,6 @@
 cmake_minimum_required(VERSION 3.22)
 
-project(FastFileTransfer VERSION 2.28.0)
+project(FastFileTransfer VERSION 2.30.0)
 
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 set(CMAKE_C_STANDARD 11)
@@ -26,9 +26,9 @@ elseif(NOT SANITIZER STREQUAL "none")
 endif()
 
 # --- Strict warnings option ---
-option(STRICT_WARNINGS "Enable strict warnings (Wextra, Wpedantic, Werror)" OFF)
+option(STRICT_WARNINGS "Enable strict warnings (Wextra, Wpedantic, Wformat-signedness, Werror)" OFF)
 if(STRICT_WARNINGS)
-	add_compile_options(-Wextra -Wpedantic -Werror)
+	add_compile_options(-Wextra -Wpedantic -Wformat-signedness -Werror)
 endif()
 
 # --- Coverage option ---
@@ -99,17 +99,21 @@ set(SHARED_SRCS
 	src/shared/daemon_limits.c
 	src/shared/data.c
 	src/shared/delay_updates.c
+	src/shared/delete.c
+	src/shared/delete_commit.c
 	src/shared/delete_plan.c
 	src/shared/delta.c
 	src/shared/file.c
 	src/shared/file_list.c
 	src/shared/file_receive.c
+	src/shared/file_save.c
 	src/shared/file_send.c
 	src/shared/file_store.c
 	src/shared/filter.c
 	src/shared/format.c
 	src/shared/hardlink.c
 	src/shared/identity.c
+	src/shared/incremental_check.c
 	src/shared/log.c
 	src/shared/metadata.c
 	src/shared/motd.c
@@ -136,9 +140,14 @@ set(SERVER_MAIN_SRCS src/server/server.c)
 # Client implementation (no main): everything except the CLI entry point.
 set(CLIENT_CORE_SRCS
 	src/client/change_list.c
+	src/client/client_manifest.c
+	src/client/client_report.c
+	src/client/client_scan.c
 	src/client/client_send.c
 	src/client/client_validation.c
 	src/client/scanner.c
+	src/client/scanner_filter.c
+	src/client/scanner_parallel.c
 	src/client/usage.c
 )
 set(CLIENT_MAIN_SRCS src/client/client_cli.c)
@@ -226,6 +235,7 @@ set(TEST_SRCS
 	tests/test_file.c
 	tests/test_file_list.c
 	tests/test_file_sendfile.c
+	tests/test_filter.c
 	tests/test_format.c
 	tests/test_fuzz_smoke.c
 	tests/test_glob.c

HANDOFF.md

@@ -1,18 +1,30 @@
-# FastSync — Session Handoff (2026-09-19)
+# FastSync — Session Handoff (2026-09-21)
 
 ## Current status
-- **rsync-parity tracks 1-6 landed on `dev`** via **PR #303** (`10159dc`,
-  "feat(parity): rsync parity tracks 1-6 (protocol 2.28.0)"). Dev push CI run
-  **581** fully green: lint, build-and-test, parity-full, ASan, UBSan,
-  fuzz-build, coverage, valgrind.
+- **Release `v2.28.0`** is tagged and merged to `main`: tag `v2.28.0` points at
+  `ee6523a`, and the PR #304 merge commit `b4d54504` is on `main`.
+- **`dev` is at `0fbb9de`** — the merge of parity cycle 2.29 (PR #305). The old
+  `558782d` (incremental-check flake fix) is an ancestor.
 - **`PROTOCOL_VERSION` = `"2.28.0"`** (`src/shared/config.h`); CMake
-  `project(FastFileTransfer VERSION 2.28.0)`. The cycle batched all wire
-  changes (stats counters, filter-rule block, `--verify-basis`) under the one
-  bump.
-- **`main` = `ef76c90`** (tag `v2.26.0`); the 2.27.0/2.28.0 work is on `dev`
-  and not yet released. A `dev -> main` v2.28.0 release PR is the next step.
-- Parity matrix: **116 ✅ / 14 ⚠️ / 27 ❌ = 157** (was 111/13/33 at cycle start).
-- Working tree clean; feature branch deleted; no scratch trees or worktrees.
+  `project(FastFileTransfer VERSION 2.28.0)`.
+- **Parity cycle 2.29 is merged to `dev`** (PR #305), no wire change. It closed
+  the scanner-order, delete-timing, relative-basis and fuzzy-eligibility
+  residuals and improved the `--info`/`--stats`/`--debug` partials. Parity
+  matrix: **120 ✅ / 10 ⚠️ / 27 ❌ = 157**. Remaining ⚠️ rows: `--info`,
+  `--debug`, `--msgs2stderr`, `--stats`, `--progress`, `--delete-before`, the
+  three basis-dir options, and `-y`/`--fuzzy`.
+- **Audit cycle complete on branch `fix/audit-cycle`** (branched from `dev` @
+  `0fbb9de`), integration PR to `dev` pending. No wire change
+  (`PROTOCOL_VERSION` stays 2.28.0). It lands the receiver/client security and
+  correctness fixes — `--temp-dir` symlink-escape confinement, special-bit
+  masking under a super-off policy, daemon `umask(022)`, the `-z` decompression
+  ceiling raised to the 256 MiB whole-file bound, `--bwlimit` pacing the
+  plaintext `--sendfile` path, `--partial-dir` implying `--partial`, rejection
+  of unsupported filter modifiers (`x`/`e`/`n`/`w`), client-side
+  `MAX_FILTER_RULES` enforcement, unknown wire `Status` rejection, and the
+  accompanying refactors/docs. The parity matrix is unchanged at
+  **120 ✅ / 10 ⚠️ / 27 ❌ = 157**; this docs pass (worktree `fix/audit-docs2`)
+  corrects the `RSYNC_COMPAT.md` summary tally to match the rows.
 
 
 ## What landed this session
@@ -98,7 +110,8 @@
     uptodate` plus the leading `./` root name line for `--info=name` (only the
     root-line trigger condition and receiver-side `skip` wording remain). Matrix
     now **111 ✅ / 14 ⚠️ / 32 ❌ = 157**; differential + unit tests added in
-    `test_features.py`, `test_option_parity.py`, `test_delete_plan.c`,
+    `test_features.py`, `test_option_parity.py`, the unit test
+    `tests/test_delete_plan.c`,
     `test_delete_delay_budget_parity.py`, `test_delete_timing_parity.py`.
 12. **No-wire parity track 2b** on `feat/parity-2.28` (no protocol change):
     `--progress`/`-P`/`--info=progress` (when not `--quiet`) now run an opt-in
@@ -195,17 +208,45 @@
     **116 ✅ / 14 ⚠️ / 27 ❌ = 157** (the `--delete`/`--delete-during` rows stay
     ⚠️ for the abort boundary; `--delete-after` stays ✅).
 
+17. **Audit cycle** on `fix/audit-cycle` (from `dev` @ `0fbb9de`;
+    `PROTOCOL_VERSION` stays `2.28.0`): a security/correctness pass over the
+    parity-2.29 baseline. It raises the decompression ceiling to the 256 MiB
+    protocol whole-file bound (`-z` on 100–256 MiB files now works), paces the
+    plaintext-TCP `--sendfile` path with `--bwlimit`, confines the `--temp-dir`
+    scratch dir by the fd's real path (symlink escape refused), masks
+    client-controlled setuid/setgid/sticky bits when super activities are not
+    permitted, sets the daemon umask to `022`, makes `--partial-dir` imply
+    `--partial`, rejects the unsupported filter modifiers (`x`/`e`/`n`/`w`),
+    enforces `MAX_FILTER_RULES` client-side, rejects unknown wire `Status`
+    values, and hardens credentials/signal handling (with the accompanying
+    refactors and docs). No row changes classification, so the matrix stays
+    **120 ✅ / 10 ⚠️ / 27 ❌ = 157**. This docs pass is on `fix/audit-docs2`.
+
 ## Next steps
-1. **Merge PR #284** (`dev` -> `main`) once reviewed (protected branch).
-2. **Deferred security items** (documented, not implemented):
-   - Pre-auth config/daemon-auth handshake has no aggregate wall-clock deadline
-     (per-message timeout only) — slowloris holds connection slots.
-   - Per-source registry fails open when the shared table is full (per-module/global
-     caps and host ACLs still apply); consider fail-closed or larger/evicting table.
-   - SCRAM-like daemon auth has no TLS channel binding (and is not RFC 5802).
-   - `cleanup()` signal handler calls non-async-signal-safe teardown; daemon `umask(0)`.
-   - Wire protocol assumes homogeneous word size/endianness (lengths are native
-     `size_t`) — document or move to fixed-width framing.
+1. **Open and merge the audit-cycle PR** (`fix/audit-cycle`, including this
+   `fix/audit-docs2` docs pass) into `dev` once reviewed. `dev` is the default
+   branch; all PRs target `dev`, never `main` directly.
+2. **Remaining deferred items:**
+   - **Large structural refactors:** delete-engine consolidation
+     (`delete_extras_fd`/`manifest_delete_extras`/the delete-plan path),
+     god-function splits, and translation-unit splits.
+   - **`--progress`/`--info` receiver→sender event channel:** the root `./`
+     line, ancestor-directory suppression, receiver-side `skip`/`backup` echo,
+     and symlink/empty-dir quick-check feedback.
+   - **`--delete-before` phase-0 keep-set** (rsync fixes the file list before
+     the data pass; FastSync keeps its pre-scan snapshot race).
+   - ~~**>256 MiB single-file streaming** (B4, the general whole-file limit).~~
+     Closed by #318: the whole-file payload, the basis read/verify and the fuzzy
+     basis are streamed through bounded buffers (lz4/append remain buffered).
+   - **Wire native-size framing:** lengths are native `size_t` and the protocol
+     assumes homogeneous word size/endianness — document or move to fixed-width
+     framing.
+   - **SCRAM-like daemon auth channel binding:** no TLS channel binding today
+     (and it is not RFC 5802).
+   - Still-open security nits: the pre-auth config/daemon-auth handshake has no
+     aggregate wall-clock deadline (per-message timeout only — slowloris holds
+     connection slots); the per-source registry fails open when the shared table
+     is full (per-module/global caps and host ACLs still apply).
 3. **Out of scope / intentional:** pull (remote source) mode is **not** planned —
    FastSync is push-only; see `RSYNC_COMPAT.md#direction`.
 

README.md

@@ -75,8 +75,9 @@ matrix is classified as parity, caveat, or divergent in
   owner, group, devices, and special files — and does not imply compression or
   multithreading (see [Client](#client)). Ownership application is still
   privilege-gated: a receiver that cannot `chown` logs a warning and skips it.
-  Under `-p` the source mode is copied exactly, including setuid/setgid/sticky
-  and group/other-write bits (strict rsync parity; see
+  Under `-p` the source mode is copied exactly, including group/other-write
+  bits; setuid/setgid/sticky bits are copied only when super-user activities are
+  permitted, and are masked under `SUPER_MODE_OFF`/`--no-super` (see
   [`RSYNC_COMPAT.md`](RSYNC_COMPAT.md)).
 - Symlink transfer stores targets **verbatim** (`-l`/`--links`), including
   absolute and `..`-bearing targets, matching rsync. The receiver does not
@@ -172,7 +173,7 @@ This produces `./build/client` and `./build/server`. `compile_commands.json` is
 | `--preserve` | Preserve mode and mtime (`-p` + `-t`; add `-o`/`-g` for owner/group or `-U`/`--atimes` for atime; `-N`/`--crtimes` captures birth time but cannot apply it) |
 | `-U, --atimes` | Preserve access times. Captured with the metadata payload; does not enable ownership. |
 | `-N, --crtimes` | Capture birth time; cannot be applied (documented divergence) |
-| `-p, --perms` | Preserve permission bits. Strict rsync parity: the source mode is copied exactly, including setuid/setgid/sticky and group/other-write bits |
+| `-p, --perms` | Preserve permission bits. The source mode is copied exactly, including group/other-write bits; setuid/setgid/sticky are copied only when super-user activities are permitted (`SUPER_MODE_OFF`/`--no-super` masks them) |
 | `-t, --times` | Preserve modification times |
 | `-o, --owner` | Preserve the source owner (privilege-gated; mapped by name on the receiver with a numeric fallback) |
 | `-g, --group` | Preserve the source group (privilege-gated; mapped by name on the receiver with a numeric fallback) |
@@ -186,7 +187,7 @@ This produces `./build/client` and `./build/server`. `compile_commands.json` is
 | `--groupmap=MAP` | Map group names when applying ownership |
 | `--numeric-ids` | Apply source numeric uid/gid directly instead of mapping by name |
 | `--copy-as=USER[:GROUP]` | Force every written entry to USER[:GROUP] (requires a privileged receiver) |
-| `--fake-super` | Record the resolved owner plus mode/time in a reserved `user.fastsync.stat` xattr and replay mode/time; never performs a real chown |
+| `--fake-super` | Record the resolved owner plus full mode/rdev in rsync's reserved `user.rsync.%stat` xattr (rsync 3.4.1 grammar) and replay the permission bits; never performs a real chown |
 | `--super` | Permit the receiver to attempt confined super-user activities (device nodes) |
 | `-D` | Preserve device and special files (implies `--devices --specials`) |
 | `--devices` | Recreate device nodes on the destination (privileged; skipped without `CAP_MKNOD`) |
@@ -204,9 +205,10 @@ This produces `./build/client` and `./build/server`. `compile_commands.json` is
 | `-u, --update` | Skip files newer than the source on the receiver |
 | `--incremental` | Skip files unchanged since last transfer (size + mtime). Auto-enables `--preserve`. Incompatible with `--chunk-serialization`. |
 | `--existing` | Skip files not already present at the destination; update existing files normally. |
-| `--compare-dest <dir>` | Extra comparison basis: unchanged files are not transferred (requires/implies `--incremental`) |
-| `--copy-dest <dir>` | Like `--compare-dest`, but copies the unchanged file from DIR into the destination |
-| `--link-dest <dir>` | Like `--copy-dest`, but hard-links the unchanged file from DIR (repeatable; earlier DIRs win) |
+| `--ignore-existing` | Skip files that already exist on the receiver; like rsync it does not apply to directories or symlinks. |
+| `--compare-dest <dir>` | Extra comparison basis: unchanged files are not transferred (requires/implies `--incremental`; a basis of any size is supported, streamed in bounded chunks — see [`RSYNC_COMPAT.md`](RSYNC_COMPAT.md)) |
+| `--copy-dest <dir>` | Like `--compare-dest`, but copies the unchanged file from DIR into the destination (the copy is streamed, so a basis of any size works; see [`RSYNC_COMPAT.md`](RSYNC_COMPAT.md)) |
+| `--link-dest <dir>` | Like `--copy-dest`, but hard-links the unchanged file from DIR (repeatable; earlier DIRs win; a basis of any size works; see [`RSYNC_COMPAT.md`](RSYNC_COMPAT.md)) |
 | `--verify-basis` | FastSync-only: require a basis hit (`--compare-dest`/`--copy-dest`/`--link-dest`) to match the source by whole-file digest instead of trusting the size+mtime quick-check (default matches rsync) |
 | `--delete` | Delete files on receiver not present in source (default timing: delete-during, matching rsync, so destination space is freed progressively). Scoped to the synchronized directories, so `--files-from` subsets are safe |
 | `--delete-before` | Delete extras before the transfer starts (implies `--delete`) |
@@ -216,24 +218,24 @@ This produces `./build/client` and `./build/server`. `compile_commands.json` is
 | `--delete-commit` | FastSync-only: keep the pre-2.28 atomic timing — delete only after the whole transfer succeeded (identical timing to `--delete-after`) |
 | `--delete-excluded` | Also delete filter-excluded destination mirrors (size-pruned mirrors stay protected) |
 | `--max-delete <n>` | Delete at most n destination entries; the rest are skipped and the run exits 25 (partial), matching rsync |
-| `--delay-updates` | Put updated files into place only at the end of the transfer (`--force` is honored at publication) |
-| `-T, --temp-dir <dir>` | Scratch directory for temp files before the atomic install; confined to the receive root (relative only), with an `EXDEV` non-atomic copy fallback |
+| `--delay-updates` | Put updated files into place only at the end of the transfer (`--force` is honored at publication; the fixed `.fastsync-stage` staging name diverges from rsync — see [`RSYNC_COMPAT.md`](RSYNC_COMPAT.md)) |
+| `-T, --temp-dir <dir>` | Scratch directory for temp files before the atomic install; confined to the receive root (a relative path resolves below it; an absolute path is accepted only when it canonicalizes inside it), with an `EXDEV` non-atomic copy fallback |
 | `-n, --dry-run` | Report what would be transferred without mutating the destination. Since protocol 2.21.0 a server-routed target contacts the receiver and reports would-transfer based on receiver state; a plain local destination keeps the client-side scan. Never mutates or deletes. |
 | `-v, --verbose` | Enable debug logging |
 | `-q, --quiet` | Suppress non-error output |
-| `--progress` | Show rsync-style per-file progress blocks from the receiver's wire counters (FastSync does not print rsync's leading `./` line) |
+| `--progress` | Show rsync-style per-file progress blocks from the receiver's wire counters; the root `./` line is printed whenever progress is active (rsync prints it only when the transfer root is created) |
 | `-P` | Enables partial-transfer mode + progress output; interrupted writes retain the already-written temp for resumption |
-| `--stats` | Print transfer statistics at end (bytes, files, timing), including the receiver-only counters reported over the wire; rsync's per-type `Number of files` breakdown is not reproduced |
+| `--stats` | Print transfer statistics at end (bytes, files, timing), including the receiver-only counters reported over the wire; `Number of files` and `Number of created files` carry rsync's per-type breakdown (deleted files are reported as a single total) |
 | `-i, --itemize-changes` | Print an rsync-style per-file change line |
-| `--out-format=FORMAT` | Output format for changed files (`%f %n %l %b %M %%`) |
+| `--out-format=FORMAT` | Output format for changed files (`%f %n %l %b %c %C %i %M %%`) |
 | `--list-only` | List source files instead of transferring |
 | `--fsync` | Fsync every written file before publication |
 | `-h, --human-readable` | Format transfer byte/rate counts with rsync's decimal (base-1000) units |
 | `--max-depth <n>` | Maximum directory depth to recurse (0 = unlimited, default: 0) |
 | `--log-file <path>` | Write log messages to file instead of stderr |
-| `--write-batch=FILE` | Run the normal live transfer and also emit a self-contained batch file of the source tree |
-| `--only-write-batch=FILE` | Emit the batch file only (no destination, no server) |
-| `--read-batch=FILE` | Apply a batch file to the destination (no source, no server) |
+| `--write-batch=FILE` | Run the normal live transfer and also emit a self-contained batch file of the source tree (FastSync-native format, not rsync-interoperable) |
+| `--only-write-batch=FILE` | Emit the batch file only (no destination, no server); FastSync-native format, not rsync-interoperable |
+| `--read-batch=FILE` | Apply a batch file to the destination (no source, no server); FastSync-native format, not rsync-interoperable |
 | `--source-dir <path>` | Source directory (overrides `FASTSYNC_SOURCE_DIR`) |
 | `--dest-dir <path>` | Server destination directory (overrides `FASTSYNC_DEST_DIR`) |
 | `--save-to-disk` | Write received files to disk |
@@ -246,12 +248,12 @@ This produces `./build/client` and `./build/server`. `compile_commands.json` is
 | `-4, --ipv4` | Force IPv4 for destination resolution |
 | `-6, --ipv6` | Force IPv6 for destination resolution |
 | `--sockopts=OPTS` | Comma-separated OPT=VAL socket options applied before connect (`TCP_NODELAY`, `SO_KEEPALIVE`, `SO_RCVBUF`, `SO_SNDBUF`, `SO_REUSEADDR`) |
-| `--bwlimit <KB/s>` | Bandwidth limit in kilobytes per second |
+| `--bwlimit <RATE>` | Bandwidth limit, using rsync's exact `parse_size_arg` grammar: a bare value is KiB/s; `K`/`M`/`G`/`T`/`P` are binary suffixes; `KB`/`MB` are decimal and `KiB`/`MiB` binary; decimals are accepted and quantized to whole KiB; `0` (or empty) means no limit. Also paces `--sendfile` transfers |
 | `--chunk-size <n>` | Chunk size in bytes (default: 10485760) |
 | `--timeout <sec>` | I/O timeout in seconds, applied to both the socket (`SO_RCVTIMEO`/`SO_SNDTIMEO`) and the per-message protocol poll deadline. Default `0` = disabled (matching rsync); `0` disables it. `--no-timeout` is the negation. The value is not sent on the wire; the server side keeps its own safe floor. |
 | `--contimeout <sec>` | Connection timeout in seconds (default: 60, matching rsync); `0` disables it (`--no-contimeout` is the negation) |
 | `--stop-after=MINS` | Stop the transfer after MINS minutes (a positive integer); whatever was already transferred is kept |
-| `--stop-at=TIME` | Stop at an absolute time (`HH:MM`, `HH:MM:SS`, or `now+N[smhd]`); an early stop skips the late `--delete` keep-set |
+| `--stop-at=TIME` | Stop at an absolute time. Accepts rsync's `parse_time` forms (`Y-M-DTh:m`, `Y/M/DTh:m`, `Y-M-D`, `M-D`, `D`, `h:m`, `:m`, `T h:m`; omitted fields resolve to the next matching point in the local timezone), plus `now+N[smhd]` and FastSync's `HH:MM`/`HH:MM:SS` clock-time spelling. An early stop skips the late `--delete` keep-set |
 | `-b, --backup` | Backup existing destination files before overwriting |
 | `--backup-dir <dir>` | Target directory for backups (requires `--backup`) |
 | `--tls` | Enable TLS encryption |
@@ -298,6 +300,7 @@ transfer is never aborted.
 | `FASTSYNC_SOURCE_DIR` | — | Source directory fallback |
 | `FASTSYNC_DEST_DIR` | — | Destination directory fallback |
 | `FASTSYNC_SAVE_TO_DISK` | `false` | Disk persistence fallback |
+| `FASTSYNC_MAX_WHOLE_FILE_SIZE` | `268435456` | Receiver-only test hook: a byte count that lowers the whole-file streaming bound. Payloads above it are streamed through a bounded buffer. Values are clamped to the 256 MiB protocol ceiling, so it can only lower, never raise, the bound. |
 
 ## Implementation Details
 
@@ -314,17 +317,22 @@ transfer is never aborted.
    `timeout`, `contimeout`, `quiet`, `stats`, `max_depth`, and `log_file` are
    client-only.
 5. **Queue** — thread-safe bounded queue with condition variables.
-6. **DirectoryScanner** — recursive BFS traversal with exclude and include
-   pattern support, max-depth enforcement.
+6. **DirectoryScanner** — recursive traversal that buffers and sorts each
+   directory (non-directories ascending, then directories ascending) and walks
+   depth-first in rsync flist order, with exclude and include pattern support and
+   max-depth enforcement.
 
 ### Key Algorithms
 
-1. **File scanning** — BFS directory traversal; entries matched against exclude
-   and include patterns, with max-depth enforced.
+1. **File scanning** — sorted depth-first traversal in rsync flist order (each
+   directory's non-directories ascending, then its directories ascending);
+   entries matched against exclude and include patterns, with max-depth
+   enforced. The `--threads` parallel scanner remains unordered.
 2. **Chunking** — files accumulated until the `chunk_size` threshold (default
    10 MiB) is reached, then flushed.
 3. **Compression** — streaming zstd via `ZSTD_compressStream2()` /
-   `ZSTD_decompressStream()`.
+   `ZSTD_decompressStream()`, with lz4 and zlib/zlibx codecs also supported
+   (selectable with `--compress-choice`).
 4. **Network protocol** — status-code-driven exchange with metadata packing,
    keep-alive, and abort support.
 5. **Incremental check** — the client sends `STATUS_CHECK` + path + size +
@@ -379,6 +387,8 @@ Received files are written to a temporary path (suffixed with `.tmp`) and then a
 - C11 compiler
 - CMake >= 3.22
 - zstd library
+- zlib library
+- lz4 library
 - OpenSSL (development headers and libraries)
 - pthreads
 - SSH client (for SSH transport mode only)
@@ -387,12 +397,12 @@ Received files are written to a temporary path (suffixed with `.tmp`) and then a
 
 **Ubuntu/Debian:**
 ```bash
-sudo apt install cmake build-essential libzstd-dev libssl-dev openssh-client
+sudo apt install cmake build-essential libzstd-dev zlib1g-dev liblz4-dev libssl-dev openssh-client
 ```
 
 **Nix:**
 ```bash
-nix-shell  # provides zstd, openssl, cmake, gcc
+nix-shell  # provides zstd, zlib, lz4, openssl, cmake, gcc
 ```
 
 ## Building
@@ -526,9 +536,9 @@ features without changing the meaning of ordinary compatibility options.
 | `--server-host <host>` | Select the TCP server host. |
 | `--server-port <port>` | Select the TCP server port (`--port <port>` and `--port=<port>` are rsync-friendly aliases). |
 | `--tls` | Enable TLS for TCP transport. |
-| `--bwlimit <KB/s>` | Apply token-bucket bandwidth limiting. |
-| `--progress` | Show rsync-style per-file progress blocks from the receiver's wire counters (FastSync omits rsync's leading `./` line). |
-| `--stats` | Print transfer statistics, including the receiver-only counters reported over the wire; rsync's per-type `Number of files` breakdown is not reproduced. |
+| `--bwlimit <RATE>` | Apply token-bucket bandwidth limiting with rsync's exact `parse_size_arg` grammar (bare = KiB/s, `K`/`M`/`G`/`T`/`P` binary, `KB`/`MB` decimal, `KiB`/`MiB` binary, decimals quantized to whole KiB, `0`/empty = no limit; also paces `--sendfile` transfers). |
+| `--progress` | Show rsync-style per-file progress blocks from the receiver's wire counters; the root `./` line is printed whenever progress is active (rsync prints it only when the transfer root is created). |
+| `--stats` | Print transfer statistics, including the receiver-only counters reported over the wire; `Number of files`/`Number of created files` carry rsync's per-type breakdown (deleted files are a single total). |
 | `--timeout <seconds>` | Set the socket **and** per-message protocol I/O timeout. Default `0` = disabled (matching rsync); `0` disables it. |
 | `--contimeout <seconds>` | Connection timeout (default 60, matching rsync); `0` disables it. |
 
@@ -562,23 +572,26 @@ remote SSH argv is already built injection-safe.
 | `--size-only` | Skip incremental files matching in size, ignoring mtime. |
 | `-I, --ignore-times` | Transfer files even when size and mtime match. |
 | `-u, --update` | Skip files newer than the source on the receiver. |
+| `--ignore-existing` | Skip files that already exist on the receiver; like rsync it does not apply to directories or symlinks. |
+| `-@, --modify-window <sec>` | Modification-time tolerance (seconds) for the incremental/basis quick-check; `0` requires an exact mtime match. |
 | `-W, --whole-file` | Transfer changed files without delta processing (`--no-whole-file` clears it). |
 | `-B <n>, --block-size <n>` | Delta block size in bytes (alias `--delta-block`). |
 | `-d, --dirs` | Transfer the named directory entries without recursing into their contents (aliases `--old-dirs`/`--old-d`). |
 | `-R, --relative` | Use rsync's relative path semantics (including the `/./` cut); with `--files-from`, preserve each listed entry's relative path below the destination root. |
 | `--files-from <file>` | Read the source file list from FILE (paths relative to the source root). |
-| `--delay-updates` | Put updated files into place only at the end of the transfer. |
-| `--compare-dest <dir>` | Extra comparison basis: unchanged files are not transferred (requires/implies `--incremental`). |
-| `--copy-dest <dir>` | Like `--compare-dest`, but copies the unchanged file from DIR into the destination. |
-| `--link-dest <dir>` | Like `--copy-dest`, but hard-links the unchanged file from DIR (repeatable; earlier DIRs win). |
+| `-0, --from0` | Treat entries in `--files-from` files as NUL-delimited instead of newline-delimited. |
+| `--delay-updates` | Put updated files into place only at the end of the transfer (the fixed `.fastsync-stage` staging name diverges from rsync; see [`RSYNC_COMPAT.md`](RSYNC_COMPAT.md)). |
+| `--compare-dest <dir>` | Extra comparison basis: unchanged files are not transferred (requires/implies `--incremental`; a basis of any size is supported, streamed in bounded chunks — see [`RSYNC_COMPAT.md`](RSYNC_COMPAT.md)). |
+| `--copy-dest <dir>` | Like `--compare-dest`, but copies the unchanged file from DIR into the destination (the copy is streamed, so a basis of any size works; see [`RSYNC_COMPAT.md`](RSYNC_COMPAT.md)). |
+| `--link-dest <dir>` | Like `--copy-dest`, but hard-links the unchanged file from DIR (repeatable; earlier DIRs win; a basis of any size works; see [`RSYNC_COMPAT.md`](RSYNC_COMPAT.md)). |
 | `--verify-basis` | FastSync-only: require a basis hit to match the source by whole-file digest instead of trusting the size+mtime quick-check (default matches rsync). |
 | `--preallocate` | Allocate destination file space up front (fail-fast on a full disk). |
 | `--append` | Resume a shorter destination by appending only its tail (prefix not verified; requires `--incremental`). |
 | `--append-verify` | Like `--append`, but verifies the retained prefix checksum first (falls back to a full transfer on mismatch). |
-| `--delete` | Request removal of destination entries absent from the source. The server must allow deletion. Default timing is delete-after: extras are removed only after the whole transfer succeeded. Scoped to the synchronized directories, so `--files-from` subsets are safe. |
+| `--delete` | Request removal of destination entries absent from the source. The server must allow deletion. Default timing is delete-during (matching rsync's `--del`): extras are removed per directory as the transfer proceeds, so destination space is freed progressively. Scoped to the synchronized directories, so `--files-from` subsets are safe. |
 | `--delete-before` | Delete extras before the transfer starts (implies `--delete`). |
-| `--delete-during`, `--del` | Delete extras once the keep-set manifest is known, before data is applied (implies `--delete`; early mode, same engine behaviour as `--delete-before`). |
-| `--delete-delay` | Delete extras only after a successful transfer (implies `--delete`; commit mode, same behaviour as `--delete-after`). |
+| `--delete-during`, `--del` | Delete each directory's extras as that directory is processed (implies `--delete`). Since protocol 2.24.0 the sender streams a per-directory `STATUS_DELETE_PLAN` frame as it reaches each source directory; this is also the default timing of a plain `--delete`. |
+| `--delete-delay` | Record extras per directory during the scan but remove them only after a successful transfer (implies `--delete`). Uses the same per-directory `STATUS_DELETE_PLAN` frames as `--delete-during`, applied late. |
 | `--delete-commit` | FastSync-only: atomic delete-after timing (only after the whole transfer succeeded). |
 | `--delete-after` | Explicit delete-after timing: delete only after the transfer succeeded (implies `--delete`). |
 | `--delete-excluded` | Also delete filter-excluded destination mirrors (size-pruned mirrors stay protected). |
@@ -594,18 +607,18 @@ remote SSH argv is already built injection-safe.
 | `--max-alloc <SIZE>` | Maximum single allocation (binary units; default 1G; `0` = no local limit). |
 | `--max-depth <n>` | Limit recursive scanning depth; zero means unlimited. |
 | `-b, --backup` | Back up overwritten files. |
-| `-T, --temp-dir <dir>` | Scratch directory for temp files before the atomic install (confined to the receive root; `EXDEV` falls back to a non-atomic copy). |
+| `-T, --temp-dir <dir>` | Scratch directory for temp files before the atomic install (confined to the receive root: relative resolves below it, absolute must canonicalize inside it; `EXDEV` falls back to a non-atomic copy). |
 | `--backup-dir <dir>` | Store backups under a separate directory (requires `--backup`). |
 | `--suffix <suffix>` | Set the backup filename suffix (default: `~`). |
 | `--partial` | Select partial-transfer handling. On failed/interrupted writes the already-written temp file is retained (best-effort) for resumption. With `--partial --partial-dir <dir>`, completed files are written under the partial directory and installed atomically. |
-| `--partial-dir <dir>` | Set a relative partial-transfer directory below the server destination root. Use with `--partial`. |
-| `--inplace` | Write directly to the destination instead of using a temporary file. |
+| `--partial-dir <dir>` | Set a relative partial-transfer directory below the server destination root. Implies `--partial`. Rejected together with `--inplace` (`--inplace cannot be used with --partial-dir`, matching rsync), because the inplace path bypasses partial/temp staging. |
+| `--inplace` | Write directly to the destination instead of using a temporary file. Cannot be combined with `--partial-dir`. |
 | `--fsync` | Fsync every written file before publication. |
-| `--write-batch=FILE` | Run the normal live transfer and also emit a self-contained batch file of the source tree. |
-| `--only-write-batch=FILE` | Emit the batch file only (no destination, no server). |
-| `--read-batch=FILE` | Apply a batch file to the destination (no source, no server). |
+| `--write-batch=FILE` | Run the normal live transfer and also emit a self-contained batch file of the source tree (FastSync-native format, not rsync-interoperable). |
+| `--only-write-batch=FILE` | Emit the batch file only (no destination, no server); FastSync-native format, not rsync-interoperable. |
+| `--read-batch=FILE` | Apply a batch file to the destination (no source, no server); FastSync-native format, not rsync-interoperable. |
 | `--stop-after=MINS` | Stop the transfer after MINS minutes; whatever was already transferred is kept. |
-| `--stop-at=TIME` | Stop at an absolute time (`HH:MM`, `HH:MM:SS`, or `now+N[smhd]`). An early stop skips the late `--delete` keep-set. |
+| `--stop-at=TIME` | Stop at an absolute time. Accepts rsync's `parse_time` forms (`Y-M-DTh:m`, `Y/M/DTh:m`, `Y-M-D`, `M-D`, `D`, `h:m`, `:m`, `T h:m`; omitted fields resolve to the next matching point in the local timezone), plus `now+N[smhd]` and FastSync's `HH:MM`/`HH:MM:SS` clock-time spelling. An early stop skips the late `--delete` keep-set. |
 
 ### Metadata and links
 
@@ -614,8 +627,11 @@ remote SSH argv is already built injection-safe.
 | `--preserve` | Preserve mode and mtime (long form only; equivalent to `-p` + `-t`). Add `-o`/`-g` for owner/group, `-U`/`--atimes` for atime, or an identity flag (`--chown`/`--usermap`/`--groupmap`/`--numeric-ids`/`--copy-as`) for mapped ownership. |
 | `-U`, `--atimes` | Preserve access times. Captured with the metadata payload; does not enable ownership. |
 | `-N`, `--crtimes` | Capture birth time and transmit it; it cannot be applied because no portable filesystem call can set a birth time (documented divergence). |
-| `-p`, `--perms` | Preserve permission bits. One of the four per-attribute preserve flags (with `-t`/`-o`/`-g`); under `-p` the source mode is copied exactly (setuid/setgid/sticky and group/other-write included), matching rsync. |
+| `-p`, `--perms` | Preserve permission bits. One of the four per-attribute preserve flags (with `-t`/`-o`/`-g`); under `-p` the source mode is copied exactly (group/other-write included; setuid/setgid/sticky included only when super-user activities are permitted, masked under `SUPER_MODE_OFF`/`--no-super`), matching rsync otherwise. |
 | `-t`, `--times` | Preserve modification times. Independent of the other attributes; `-O`/`--omit-dir-times` suppresses directories only. |
+| `-O`, `--omit-dir-times` | Do not apply modification times to directories. |
+| `-J`, `--omit-link-times` | Do not apply times to symlinks. |
+| `--open-noatime` | Open source files with `O_NOATIME` so reading for a transfer does not update their access time (client-only). |
 | `-o`, `--owner` | Preserve the source owner (uid). Mapped by name on the receiver with a raw-numeric fallback (only numeric ids cross the wire); application is privilege-gated. |
 | `-g`, `--group` | Preserve the source group (gid). Same name-mapping/numeric-fallback and privilege gating as `-o`. |
 | `--no-perms`, `--no-times`, `--no-owner`, `--no-group` | Negate each per-attribute flag (also `--no-p`/`--no-t`/`--no-o`/`--no-g`); `--no-preserve` clears all four. |
@@ -628,7 +644,7 @@ remote SSH argv is already built injection-safe.
 | `--groupmap=MAP` | Map group names when applying ownership (same syntax as `--usermap`). |
 | `--numeric-ids` | Mapping modifier: apply the source numeric uid/gid directly instead of mapping by name (combine with `-o`/`-g`, `-a`, or a map). |
 | `--copy-as=USER[:GROUP]` | Force every written entry to USER[:GROUP]; requires a privileged receiver. |
-| `--fake-super` | Record the resolved owner plus mode/time in a reserved `user.fastsync.stat` xattr and replay mode/time; never performs a real chown. |
+| `--fake-super` | Record the resolved owner plus full mode/rdev in rsync's reserved `user.rsync.%stat` xattr (rsync 3.4.1 grammar) and replay the permission bits; never performs a real chown. |
 | `--super` | Permit the receiver to attempt confined super-user activities (device nodes). |
 | `--no-super` | Forbid those super-user activities even when the receiver is root. |
 | `-l`, `--links` | Copy symlinks as symlinks; the target is stored verbatim (absolute and `..`-bearing targets included), matching rsync. |
@@ -642,6 +658,7 @@ remote SSH argv is already built injection-safe.
 | `-D` | Preserve device and special files (implies `--devices --specials`). |
 | `--devices` | Recreate device nodes on the destination (privileged; skipped without `CAP_MKNOD`). |
 | `--specials` | Recreate special files: FIFOs and unix sockets. |
+| `--copy-devices` | Copy a source device's content as an ordinary regular file on the destination (rsync's non-privileged safe mode) instead of recreating the device node. |
 | `-S`, `--sparse` | Sparse-file handling: receiver preserves holes (zero runs are written as holes; no wire change). |
 
 ### Output and logging
@@ -650,12 +667,17 @@ remote SSH argv is already built injection-safe.
 |---|---|
 | `-v`, `--verbose` | Enable debug logging. |
 | `-q`, `--quiet` | Suppress non-error output. |
-| `--progress` | Show rsync-style per-file progress blocks (not rsync's leading `./` line). |
-| `--stats` | Print transfer statistics, including the receiver-only counters reported over the wire. |
-| `-i`, `--itemize-changes` | Print an rsync-style per-file change line. |
-| `--out-format=FORMAT` | Output format for changed files (`%f %n %l %b %M %%`). |
+| `--progress` | Show rsync-style per-file progress blocks; the root `./` line is printed whenever progress is active (rsync prints it only when the transfer root is created). |
+| `--stats` | Print transfer statistics, including the receiver-only counters reported over the wire; `Number of files`/`Number of created files` carry rsync's per-type breakdown (deleted files are a single total). |
+| `-i, --itemize-changes` | Print an rsync-style per-file change line. |
+| `--out-format=FORMAT` | Output format for changed files (`%f %n %l %b %c %C %i %M %%`). |
 | `--list-only` | List source files instead of transferring. |
+| `--outbuf=MODE` | stdout/stderr buffering: `N` (none/unbuffered), `L` (line-buffered), or `B` (block-buffered, default). |
 | `--log-file <path>` | Write log output to a file. |
+| `--log-file-format=FORMAT` | Per-file log-line format (requires `--log-file`). |
+| `--stderr=MODE` | Route logging: `errors` (default), `all`, or `client` (forward the client's diagnostics to the server's stderr over the client-message channel). |
+| `--msgs2stderr` | Route all messages to stderr (deprecated spelling of `--stderr=all`). |
+| `--no-msgs2stderr` | Forward the client's diagnostics to the server (deprecated spelling of `--stderr=client`). |
 | `-V`, `--version` | Print the FastSync protocol version. |
 | `--help` | Print command usage. |
 
@@ -668,7 +690,7 @@ remote SSH argv is already built injection-safe.
 | `--fastsync-server-path <path>` | Remote FastSync server path for SSH mode (client-only; never crosses the wire). |
 | `--rsync-path <path>` | Alias for `--fastsync-server-path`. |
 | `-M`, `--remote-option=OPT` | Append OPT to the remote server invocation over SSH (repeatable; rejected for daemon/TCP destinations). |
-| `--trust-sender` | Receiver-local: trust the remote sender's file list and skip path re-validation (does not affect symlink targets). |
+| `--trust-sender` | Receiver-local: trust the remote sender's file list and skip path re-validation (does not affect symlink targets). **On the client this flag alone is inert** — it is never sent on the wire; the server must be started with its own `--trust-sender`, or the client must forward it with `-M--trust-sender` (SSH only). |
 | `--timeout <sec>` | Socket + per-message I/O timeout; default `0` = disabled. |
 | `--contimeout <sec>` | Connection timeout; default 60; `0` disables. |
 | `--source-dir <path>` | Set the source directory explicitly. |
@@ -680,6 +702,11 @@ remote SSH argv is already built injection-safe.
 | `-4`, `--ipv4` | Force IPv4 for destination resolution. |
 | `-6`, `--ipv6` | Force IPv6 for destination resolution. |
 | `--sockopts=OPTS` | Comma-separated OPT=VAL socket options applied before connect. |
+| `--blocking-io` | SSH transport only: leave the socket without read/write timeouts so it blocks naturally (no effect on TCP). |
+| `--protocol=NUM` | Force the wire protocol version; must equal the current `PROTOCOL_VERSION` (FastSync cannot speak older/virtual wire formats). |
+| `--old-args` | Accepted for rsync CLI compatibility; no effect (the remote server path is always safely quoted). |
+| `--iconv=LOCAL[,REMOTE]` | Convert file-name charsets at the wire boundary (`LOCAL` is our names' charset, `REMOTE` the peer's, defaulting to `LOCAL`). |
+| `--no-iconv` | Disable `--iconv` charset conversion (same as `--iconv=-`). |
 | `--tls` | Enable TLS. Requires `--cert`, `--key`, and `--ca`. |
 | `--cert <path>` | TLS certificate file. |
 | `--key <path>` | TLS private key file. |
@@ -706,14 +733,14 @@ remote SSH argv is already built injection-safe.
 | `-6`, `--ipv6` | Bind an IPv6 socket. |
 | `--allow-delete` | Permit client delete manifests. Deletion is refused by default. This also gates `--force` (which can recursively replace/remove a destination directory tree). |
 | `--allow-super` | Standalone TCP listener only: keep super-user activities enabled for a **root** receiver. Without it a root standalone server forces `SUPER_MODE_OFF`, so client `--devices`/`--write-devices`/`--super` and client-chosen ownership requests are skipped/refused. Rejected with `--stdio` (the SSH remote argv is client-composed; use a forced command if the default must hold). No effect when not root. Daemon modules opt in per module with `client owner = yes`. |
-| `--trust-sender` | Trust the remote sender's file list: skip the receiver's up-front path-traversal re-validation (fewer checks, faster, potentially unsafe; off by default). It does not affect symlink targets, which are stored verbatim either way. |
+| `--trust-sender` | Trust the remote sender's file list: skip the receiver's up-front path-traversal re-validation (fewer checks, faster, potentially unsafe; off by default). It does not affect symlink targets, which are stored verbatim either way. A client `--trust-sender` is never sent over the wire — the server must set this flag itself, or the client must forward it via `-M--trust-sender`. |
 | `--no-super` | Operator veto: never attempt super-user activities (ownership, device nodes) even as root, and refuse any client `--copy-as`/`--super` request. |
 | `--allow-unauthenticated` | Permit plaintext/anonymous network clients; an auth-required module still accepts only opted-in loopback plaintext. |
 | `--iconv=LOCAL[,REMOTE]` | Declare this server's LOCAL charset for file-name conversion. |
-| `--password-file=FILE` | Credential store for modules that declare `auth users`. Requires `--daemon`. |
-| `--early-input=FILE` | Second credential store layered over `--password-file`. Requires `--daemon`. |
-| `--hash-credentials <file>` | Read `<file>`'s `user:password` lines and print PBKDF2 credential-store lines to stdout, then exit. Cannot be combined with `--daemon` or `--stdio`. |
-| `--iterations N` | PBKDF2 iteration count for `--hash-credentials` (default 600000, range 100000–10000000). Requires `--hash-credentials`. |
+| `--password-file=FILE` | Credential store for modules that declare `auth users`. Requires `--daemon`. FastSync-native SCRAM/PBKDF2 format, not rsync-interoperable. |
+| `--early-input=FILE` | Second credential store layered over `--password-file`. Requires `--daemon`. FastSync-native format, not rsync-interoperable. |
+| `--hash-credentials <file>` | Read `<file>`'s `user:password` lines and print PBKDF2 credential-store lines to stdout, then exit. Cannot be combined with `--daemon` or `--stdio`. FastSync-native, not rsync-interoperable. |
+| `--iterations N` | PBKDF2 iteration count for `--hash-credentials` (default 600000, range 100000–10000000). Requires `--hash-credentials`. FastSync-native, not rsync-interoperable. |
 | `-v`, `--verbose` | Enable debug logging. |
 | `--help` | Print server usage. |
 
@@ -742,9 +769,17 @@ and `address`, the global section accepts:
 - `hosts allow` / `hosts deny` — comma- and/or whitespace-separated host access
   patterns.
 
-A `[module]` requires `path`, and may also set `read only`, `client owner`,
-`auth users`, `max connections` (0 = unlimited; enforced per module across all
-connection children), and its own `hosts allow`/`hosts deny`.
+A `[module]` requires `path`, and may also set `read only`, `write only`,
+`client owner`, `auth users`, `max connections` (0 = unlimited; enforced per
+module across all connection children), and its own `hosts allow`/`hosts deny`.
+
+Like rsync, a module is **read-only by default**: a bare `[module]` with only a
+`path` refuses a write transfer. Opt a module into writability explicitly with
+`read only = no` or `write only = yes`; a global `read only` value in the
+section before the first `[module]` sets the default for later modules, and a
+module's own `read only`/`write only = yes` always wins over it. An
+rsync-style `write only = yes` is mapped to writability because FastSync is
+push-only (a module can never be read from the network).
 
 The per-host cap and the shared auth lockout identify a source by its numeric
 peer IP. **Loopback peers (127.0.0.0/8, IPv6 `::1`) are exempt**: every local
@@ -798,7 +833,7 @@ before the module list, before authentication, and the connecting peer address
 
 ## Protocol and Security
 
-FastSync protocol version `2.28.0` is shared by the client and server. The
+FastSync protocol version `2.30.0` is shared by the client and server. The
 current protocol is sender-driven and includes configuration negotiation,
 including the maximum allocation limit, incremental checks, checksums,
 manifests, keep-alives, abort handling, per-file remove-source results, and
@@ -871,8 +906,10 @@ The project will reach the drop-in replacement goal in stages:
    completion wave's scope; the tests live in `tests/integration/` and skip
    cleanly when rsync is unavailable.
 3. `-a` implements full rsync `-rlptgoD`; under `-p` the source mode is copied
-   exactly (no masking). Ownership application stays privilege-gated, as in
-   rsync.
+   exactly, including group/other-write bits, with setuid/setgid/sticky copied
+   only when super-user activities are permitted (masked under
+   `SUPER_MODE_OFF`/`--no-super`). Ownership application stays privilege-gated,
+   as in rsync.
 4. Symlink (verbatim storage), sparse-file, metadata, delete-policy (including
    `--max-delete` partial + exit 25, per-directory `--delete-during`/
    `--delete-delay`), codecs, and resumable-write semantics are implemented;

rc/a.txt

@@ -0,0 +1 @@
+top

rc/link

@@ -0,0 +1 @@
+b.txt

rc/sub/b.txt

@@ -0,0 +1 @@
+nested

rd/a.txt

@@ -0,0 +1 @@
+top

rd/link

@@ -0,0 +1 @@
+b.txt

rd/sub/b.txt

@@ -0,0 +1 @@
+nested

src/client/change_list.c

@@ -123,8 +123,15 @@ static char itemize_type_char(const ChangeEvent* event) {
 static bool times_match(const Config* config, const ChangeEvent* event) {
   if (!event->dest.known || !event->dest.existed)
     return false;
-  if (event->mtime_sec == event->dest.mtime_sec)
+  if (event->mtime_sec == event->dest.mtime_sec) {
+    /* A regular file's sub-second mtime IS preserved by the receiver, so an nsec
+       difference is a real change.  A directory or symlink has no preserved
+       sub-second mtime (rsync's quick-check compares whole seconds there), so a
+       nanosecond-only difference must not render a spurious `.d..t` / `.L..t`. */
+    if (event->is_directory || event->is_symlink || event->is_special)
+      return true;
     return event->mtime_nsec == event->dest.mtime_nsec;
+  }
   long long delta = (long long)event->mtime_sec - (long long)event->dest.mtime_sec;
   if (delta < 0)
     delta = -delta;
@@ -141,6 +148,14 @@ static void itemize_code(const Config* config, const ChangeEvent* event, char co
     update = 'h';
   else if (created)
     update = (event->is_directory || event->is_symlink || event->is_special) ? 'c' : '>';
+  else if (event->is_directory)
+    /* rsync: an existing directory that only has attribute changes carries no
+       transfer, so the update column is `.` rather than `>`. */
+    update = '.';
+  else if (event->is_symlink)
+    /* rsync: an existing symlink whose target is unchanged is a `.` update
+       (attributes only); a changed target is `c` (the link value changed). */
+    update = event->dest.target_matches ? '.' : 'c';
   else
     update = '>';
   code[0] = update;
@@ -151,12 +166,20 @@ static void itemize_code(const Config* config, const ChangeEvent* event, char co
     code[11] = '\0';
     return;
   }
-  bool size_diff = event->size != event->dest.size;
-  bool time_diff = !times_match(config, event);
+  /* rsync's value/checksum column: `c` for a symlink whose target changed (the
+     link value is the compared content); no destination digest is available for
+     a regular file. */
+  bool value_diff = event->is_symlink && !event->dest.target_matches;
+  /* rsync itemizes size only for regular files: a directory's st_size and a
+     symlink's target length are not compared. */
+  bool size_diff = !event->is_directory && !event->is_symlink && !event->is_special &&
+                   event->size != event->dest.size;
+  /* rsync itemizes the time column only when -t/--times is in effect. */
+  bool time_diff = config->preserve_times && !times_match(config, event);
   bool perms_diff = (event->mode & 07777) != (event->dest.mode & 07777);
   bool owner_diff = event->uid != (uid_t)event->dest.uid;
   bool group_diff = event->gid != (gid_t)event->dest.gid;
-  code[2] = '.'; /* checksum: no destination digest available */
+  code[2] = value_diff ? 'c' : '.';
   code[3] = size_diff ? 's' : '.';
   code[4] = time_diff ? 't' : '.';
   code[5] = (config->preserve_perms && perms_diff) ? 'p' : '.';
@@ -168,12 +191,33 @@ static void itemize_code(const Config* config, const ChangeEvent* event, char co
   code[11] = '\0';
 }
 
-/* rsync %n: the transfer-relative name, with a trailing slash for directories. */
-static bool append_name(StrBuf* buf, const ChangeEvent* event) {
-  if (!strbuf_append(buf, event->name != NULL ? event->name : ""))
+/* True when the itemized destination entry is unchanged, i.e. rsync would print
+ * no line at all.  Reuses itemize_code so suppression is exactly consistent
+ * with what would have been rendered: the update column must be `.` and every
+ * attribute column must be `.`. */
+static bool itemize_is_unchanged(const Config* config, const ChangeEvent* event) {
+  if (!event->dest.known || !event->dest.existed)
     return false;
-  if (event->is_directory && (event->name == NULL || event->name[0] == '\0' ||
-                              event->name[strlen(event->name) - 1] != '/'))
+  char code[12];
+  itemize_code(config, event, code);
+  if (code[0] != '.')
+    return false;
+  for (int i = 2; i < 11; i++) {
+    if (code[i] != '.')
+      return false;
+  }
+  return true;
+}
+
+/* rsync %n: the transfer-relative name, with a trailing slash for directories.
+ * The transfer root is `.` (so `%n` renders `./`), matching rsync's root entry. */
+static bool append_name(StrBuf* buf, const ChangeEvent* event) {
+  const char* name = event->name != NULL ? event->name : "";
+  if (event->is_directory && name[0] == '\0')
+    return strbuf_append(buf, "./");
+  if (!strbuf_append(buf, name))
+    return false;
+  if (event->is_directory && name[strlen(name) - 1] != '/')
     return strbuf_append_char(buf, '/');
   return true;
 }
@@ -245,7 +289,7 @@ static char* change_render_name_uptodate(const ChangeEvent* event) {
  * resolves to xxh128, so an explicit selection and the default both render the
  * selected algorithm's digest. */
 static ChecksumAlgo out_format_checksum_algo(const Config* config) {
-  return (ChecksumAlgo)config->checksum_transfer_algo;
+  return (ChecksumAlgo)config->cli.checksum_transfer_algo;
 }
 
 /* Render a digest as rsync's sum_as_hex: xxh128 prints the HIGH 64-bit half
@@ -671,6 +715,19 @@ void change_emit_file_sent_bytes(const Config* config, const File* file,
   char* name = NULL;
   char* path = NULL;
   fill_event_from_file(config, file, &event, &name, &path);
+  if (file->is_symlink) {
+    /* Output parity (protocol 2.30.0): an unchanged symlink is silent, like
+       rsync's quick check.  The itemize/log stream suppresses it only when every
+       attribute matches; the name stream suppresses it whenever the link target
+       is unchanged (rsync names a symlink only when it relinks or creates it). */
+    bool itemize_output = config->itemize_changes || config->out_format != NULL ||
+                          (config->log_file != NULL && config->log_file_format != NULL);
+    bool suppress = itemize_output
+                        ? itemize_is_unchanged(config, &event)
+                        : (event.dest.known && event.dest.existed && event.dest.target_matches);
+    if (suppress)
+      event.decision = CHANGE_UP_TO_DATE;
+  }
   if (name != NULL && path != NULL) {
     fill_event_checksum(config, file, &event);
     change_emit(config, &event);
@@ -722,6 +779,19 @@ void change_emit_dir_sent(const Config* config, const File* file) {
   char* name = NULL;
   char* path = NULL;
   fill_event_from_file(config, file, &event, &name, &path);
+  /* Output parity (protocol 2.30.0): suppress a directory rsync would leave
+     silent.  The itemize/log stream suppresses it only when every attribute
+     matches (`.d.........`); the name stream suppresses any pre-existing
+     directory (rsync names a directory only when it is created). */
+  bool itemize_output = config->itemize_changes || config->out_format != NULL ||
+                        (config->log_file != NULL && config->log_file_format != NULL);
+  bool suppress = itemize_output ? itemize_is_unchanged(config, &event)
+                                 : (event.dest.known && event.dest.existed);
+  /* The transfer root's line is an unconditional FastSync residual (rsync keys
+     it off the root's own attribute change); keep emitting it. */
+  bool is_root = event.name != NULL && event.name[0] == '\0';
+  if (suppress && !is_root)
+    event.decision = CHANGE_UP_TO_DATE;
   if (name != NULL && path != NULL)
     change_emit(config, &event);
   free(name);

src/client/client_cli.c

@@ -54,13 +54,26 @@ bool client_abort_pending(void) {
 }
 
 #ifndef FASTSYNC_TEST_BUILD
+/* SIG_DFL disposition used by the handler's "not armed" fallback.  It is built
+ * once at load time so the handler can restore the default action with
+ * sigaction(2) -- which is async-signal-safe -- instead of signal(3), which is
+ * not.  The zero-initialized sa_mask is the empty set. */
+static const struct sigaction client_default_action = {
+    .sa_handler = SIG_DFL,
+    .sa_flags = 0,
+};
+
 /* Signal handler: perform NO work beyond storing the flag.  Logging, protocol
  * I/O and the STATUS_ABORT frame are all done later on the normal send path,
- * which is not async-signal-safe.  When no transfer is armed, fall back to the
- * default action so local-only modes remain interruptible. */
+ * which is not async-signal-safe.  When no transfer is armed, restore the
+ * default disposition (async-signal-safe sigaction) and re-raise so local-only
+ * modes remain interruptible.  The handler deliberately stays installed while a
+ * transfer is armed -- rather than using SA_RESETHAND -- so a second Ctrl-C
+ * during the graceful abort keeps setting the flag instead of hard-killing the
+ * process mid-cleanup. */
 static void client_signal_handler(int signo) {
   if (!client_abort_armed) {
-    signal(signo, SIG_DFL);
+    sigaction(signo, &client_default_action, NULL);
     raise(signo);
     return;
   }
@@ -157,7 +170,7 @@ static int set_positive_int_option(int* dest, const char* value, const char* opt
  * name is a hard error with rsync's exit code 4, never a silent no-op. */
 static int set_compression_choice(Config* config, const char* value) {
   if (!value) {
-    config->cli_exit_code = 4;
+    config->cli.cli_exit_code = 4;
     return -1;
   }
   int algo;
@@ -165,7 +178,7 @@ static int set_compression_choice(Config* config, const char* value) {
     algo = compression_choice_resolve();
     if (algo < 0) {
       log_message(LOG_LEVEL_ERROR, "RSYNC_COMPRESS_LIST names no supported compression algorithm");
-      config->cli_exit_code = 4;
+      config->cli.cli_exit_code = 4;
       return -1;
     }
   } else {
@@ -176,7 +189,7 @@ static int set_compression_choice(Config* config, const char* value) {
                 "--compress-choice '%s' is not a supported algorithm; FastSync supports zstd, "
                 "lz4, zlib, zlibx, none or auto",
                 value);
-    config->cli_exit_code = 4;
+    config->cli.cli_exit_code = 4;
     return -1;
   }
   const char* canonical = compression_algo_name((CompressionAlgo)algo);
@@ -213,7 +226,7 @@ static int resolve_checksum_name(const char* name, size_t len, int* out) {
  * resolves to FastSync's negotiated default (xxh128). */
 static int set_checksum_choice(Config* config, const char* value) {
   if (!value) {
-    config->cli_exit_code = 4;
+    config->cli.cli_exit_code = 4;
     return -1;
   }
   const char* comma = strchr(value, ',');
@@ -231,7 +244,7 @@ static int set_checksum_choice(Config* config, const char* value) {
                 "--checksum-choice '%s' is invalid; FastSync supports xxh64 (or xxhash), xxh128, "
                 "xxh3, md5, md4, sha1, none or auto, optionally as 'transfer,pre-transfer'",
                 value);
-    config->cli_exit_code = 4;
+    config->cli.cli_exit_code = 4;
     return -1;
   }
   int negotiated = -1;
@@ -239,7 +252,7 @@ static int set_checksum_choice(Config* config, const char* value) {
     negotiated = checksum_choice_resolve();
     if (negotiated < 0) {
       log_message(LOG_LEVEL_ERROR, "RSYNC_CHECKSUM_LIST names no supported checksum algorithm");
-      config->cli_exit_code = 4;
+      config->cli.cli_exit_code = 4;
       return -1;
     }
   }
@@ -251,8 +264,8 @@ static int set_checksum_choice(Config* config, const char* value) {
     pre = negotiated;
 
   config->checksum_algo = pre;
-  config->checksum_transfer_algo = transfer;
-  config->checksum_choice_set = true;
+  config->cli.checksum_transfer_algo = transfer;
+  config->cli.checksum_choice_set = true;
   /* rsync: "none" for the transfer checksum forces --whole-file. */
   if (transfer == (int)CHECKSUM_ALGO_NONE)
     config->whole_file = true;
@@ -420,12 +433,10 @@ static int set_stderr_mode(const char* value) {
     log_set_stderr_mode(LOG_STDERR_ERRORS);
   else if (strcmp(value, "all") == 0 || strcmp(value, "a") == 0)
     log_set_stderr_mode(LOG_STDERR_ALL);
-  else if (strcmp(value, "client") == 0 || strcmp(value, "c") == 0) {
-    log_message(LOG_LEVEL_ERROR,
-                "--stderr=client is not supported: FastSync has no client message channel");
-    return -1;
-  } else {
-    log_message(LOG_LEVEL_ERROR, "--stderr must be errors or all");
+  else if (strcmp(value, "client") == 0 || strcmp(value, "c") == 0)
+    log_set_stderr_mode(LOG_STDERR_CLIENT);
+  else {
+    log_message(LOG_LEVEL_ERROR, "--stderr must be errors, all, or client");
     return -1;
   }
   return 0;
@@ -504,9 +515,8 @@ static bool split_flag_level(const char* token, char* name, size_t name_size, in
  * of rsync's `symsafe`, `hlink`, and `own`. */
 static bool is_accepted_debug_category(const char* name) {
   static const char* const categories[] = {
-      "acl",   "backup", "bind",   "chdir", "cmd",   "connect", "del",  "deltasum",
-      "dup",   "exit",   "filter", "flist", "fuzzy", "genr",    "hash", "hl",
-      "hlink", "iconv",  "nstr",   "own",   "owner", "recv",    "send", "time",
+      "acl",  "backup", "bind",  "chdir", "cmd",  "connect", "dup",   "exit", "fuzzy",
+      "genr", "hl",     "hlink", "iconv", "nstr", "own",     "owner", "time",
   };
   for (size_t i = 0; i < sizeof(categories) / sizeof(categories[0]); i++) {
     if (strcmp(name, categories[i]) == 0)
@@ -518,7 +528,6 @@ static bool is_accepted_debug_category(const char* name) {
 static bool is_accepted_info_category(const char* name) {
   static const char* const categories[] = {
       "backup",
-      "mount",
       "syms",
       "symsafe",
   };
@@ -571,6 +580,18 @@ static int parse_debug_flags(const char* value, Config* config) {
       flag = LOG_DEBUG_PACK;
     } else if (strcmp(name, "util") == 0) {
       flag = LOG_DEBUG_UTIL;
+    } else if (strcmp(name, "flist") == 0) {
+      flag = LOG_DEBUG_FLIST;
+    } else if (strcmp(name, "del") == 0) {
+      flag = LOG_DEBUG_DEL;
+    } else if (strcmp(name, "hash") == 0 || strcmp(name, "deltasum") == 0) {
+      flag = LOG_DEBUG_HASH;
+    } else if (strcmp(name, "recv") == 0) {
+      flag = LOG_DEBUG_RECV;
+    } else if (strcmp(name, "filter") == 0) {
+      flag = LOG_DEBUG_FILTER;
+    } else if (strcmp(name, "send") == 0) {
+      flag = LOG_DEBUG_SEND;
     } else if (is_accepted_debug_category(name)) {
       continue;
     } else {
@@ -645,9 +666,12 @@ static int parse_info_flags(const char* value, Config* config) {
       flag = LOG_INFO_MISC;
     else if (strcmp(name, "skip") == 0)
       flag = LOG_INFO_SKIP;
-    else if (strcmp(name, "stats") == 0)
+    else if (strcmp(name, "stats") == 0) {
       flag = LOG_INFO_STATS;
-    else if (strcmp(name, "del") == 0)
+      /* `--info=stats` requests the same transfer-statistics block as
+         `--stats`; `--info=stats0` turns it back off. */
+      config->stats = level > 0;
+    } else if (strcmp(name, "del") == 0)
       flag = LOG_INFO_DEL;
     else if (strcmp(name, "remove") == 0)
       flag = LOG_INFO_REMOVE;
@@ -655,6 +679,8 @@ static int parse_info_flags(const char* value, Config* config) {
       flag = LOG_INFO_FLIST;
     else if (strcmp(name, "nonreg") == 0)
       flag = LOG_INFO_NONREG;
+    else if (strcmp(name, "mount") == 0)
+      flag = LOG_INFO_MOUNT;
     else if (strcmp(name, "progress") == 0)
       flag = LOG_INFO_PROGRESS;
     else if (is_accepted_info_category(name))
@@ -934,8 +960,18 @@ static const OptionEntry OPTION_TABLE[] = {
     /* rsync -r/--recursive: FastSync is always recursive, so this is a
      * faithful no-op (accepted silently, never consumes an argument). */
     {"--recursive", "-r", OPT_NOOP, 0},
+    /* rsync's incremental-recursion scan-mode switch.  FastSync always performs
+     * a single full recursive scan, so both spellings are accepted as no-ops:
+     * the destination is identical whichever mode the caller requests.
+     * --no-inc-recursive is handled before the generic --no-* negation branch
+     * (see cli_handle_pre_negation) but is registered here for discoverability. */
+    {"--inc-recursive", NULL, OPT_NOOP, 0},
+    {"--no-inc-recursive", NULL, OPT_NOOP, 0},
     {"--update", "-u", OPT_FLAG, offsetof(Config, update)},
-    {"--old-args", NULL, OPT_FLAG, offsetof(Config, old_args)},
+    /* rsync's --old-args: accepted for CLI compatibility as a documented no-op
+     * (the remote server path is always safely quoted; see usage.c).  It is
+     * recognized but stores no Config field. */
+    {"--old-args", NULL, OPT_NOOP, 0},
     {"--rsh", "-e", OPT_STRING, offsetof(Config, rsh_command)},
     {"--blocking-io", NULL, OPT_FLAG, offsetof(Config, blocking_io)},
     {"--links", "-l", OPT_FLAG, offsetof(Config, follow_symlinks)},
@@ -1168,12 +1204,12 @@ static int apply_negation(Config* config, const char* arg) {
     config->preserve_times = false;
     config->preserve_owner = false;
     config->preserve_group = false;
-    config->metadata_explicitly_disabled = true;
+    config->cli.metadata_explicitly_disabled = true;
     /* --no-preserve is an explicit opt-out of the whole bundle: record it so
      * the --incremental/--delta auto-preserve in cli_finalize_config does not
      * silently re-enable perms/times. */
-    config->preserve_perms_explicit_off = true;
-    config->preserve_times_explicit_off = true;
+    config->cli.preserve_perms_explicit_off = true;
+    config->cli.preserve_times_explicit_off = true;
     return 0;
   }
   *(bool*)((char*)config + entry->offset) = false;
@@ -1181,9 +1217,9 @@ static int apply_negation(Config* config, const char* arg) {
    * auto-preserve the OTHER attribute without undoing this one.  A later
    * -p/-t sets the attribute directly; this flag only gates the implication. */
   if (entry->offset == offsetof(Config, preserve_perms))
-    config->preserve_perms_explicit_off = true;
+    config->cli.preserve_perms_explicit_off = true;
   else if (entry->offset == offsetof(Config, preserve_times))
-    config->preserve_times_explicit_off = true;
+    config->cli.preserve_times_explicit_off = true;
   return 0;
 }
 
@@ -1213,7 +1249,13 @@ static int apply_table_option(Config* config, const OptionEntry* entry, const ch
   void* field = (char*)config + entry->offset;
   switch (entry->kind) {
   case OPT_FLAG:
-    *(bool*)field = true;
+    /* -x/--one-file-system is repeatable in rsync: `-xx` increments the level so
+       the scanner drops mount-point directories instead of recreating them
+       empty.  Everything else is a plain boolean. */
+    if (entry->offset == offsetof(Config, one_file_system))
+      (*(int*)field)++;
+    else
+      *(bool*)field = true;
     return 0;
   case OPT_NOOP:
     return 0;
@@ -1309,10 +1351,9 @@ static bool cli_handle_pre_negation(CliParseCtx* ctx) {
     return true;
   }
   /* "--no-msgs2stderr" is the deprecated spelling of --stderr=client (rsync
-   * 3.4.1).  FastSync has no separate client message channel, so the closest
-   * supported mode is the errors-only default. */
+   * 3.4.1); the client-message channel now exists, so it maps to `client`. */
   if (strcmp(arg, "--no-msgs2stderr") == 0)
-    return set_stderr_mode("errors") == 0;
+    return set_stderr_mode("client") == 0;
   /* "--no-motd" is a real rsync option name (client-side daemon MOTD display
    * suppression), not a negation of a "--motd" flag, so it is handled before
    * the generic --no-* negation branch. */
@@ -1350,6 +1391,12 @@ static bool cli_handle_pre_negation(CliParseCtx* ctx) {
       ctx->no_delta = true;
     else if (strcmp(arg, "--no-incremental") == 0)
       ctx->no_incremental = true;
+    /* Real rsync option names that merely start with "--no-" and are inert
+     * no-ops (e.g. --no-inc-recursive) are registered as OPT_NOOP entries;
+     * accept them before the generic negation table would reject the name. */
+    const OptionEntry* noop = find_table_option(arg);
+    if (noop && noop->kind == OPT_NOOP)
+      return true;
     if (apply_negation(config, arg) != 0) {
       ctx->exit_code = -1;
       return true;
@@ -1406,7 +1453,7 @@ static bool cli_handle_range_time_options(CliParseCtx* ctx) {
       ctx->exit_code = -1;
       return true;
     }
-    config->stop_at_set = true;
+    config->cli.stop_at_set = true;
     return true;
   }
   if (strcmp(arg, "--stop-at") == 0) {
@@ -1421,7 +1468,7 @@ static bool cli_handle_range_time_options(CliParseCtx* ctx) {
       ctx->exit_code = -1;
       return true;
     }
-    config->stop_at_set = true;
+    config->cli.stop_at_set = true;
     return true;
   }
   const char* threads_prefix = "--compress-threads=";
@@ -1492,7 +1539,7 @@ static bool cli_handle_table_option(CliParseCtx* ctx) {
         return true;
       }
       if (entry->offset == offsetof(Config, compression_level))
-        config->compression_level_set = true;
+        config->cli.compression_level_set = true;
       if (entry->offset == offsetof(Config, chmod_spec)) {
         mode_t ignored;
         if (!chmod_apply(0, config->chmod_spec, &ignored)) {
@@ -1505,7 +1552,7 @@ static bool cli_handle_table_option(CliParseCtx* ctx) {
          defaults to 127.0.0.1, so a value check cannot distinguish it).  Used
          by --dry-run to route an explicit remote target to the server. */
       if (entry->offset == offsetof(Config, server_host))
-        config->server_host_set = true;
+        config->cli.server_host_set = true;
     }
   } else if (apply_table_option(config, entry, NULL) != 0) {
     ctx->exit_code = -1;
@@ -1779,7 +1826,7 @@ static bool cli_handle_transfer_flags(CliParseCtx* ctx) {
           return true;
         }
         config->compression_level = (int)level;
-        config->compression_level_set = true;
+        config->cli.compression_level_set = true;
         log_info_message(LOG_INFO_MISC, "Set Compression level to %ld", level);
         ctx->i++;
       }
@@ -1843,7 +1890,7 @@ static int set_server_port_option(Config* config, const char* value, const char*
     return -1;
   }
   config->server_port = port;
-  config->server_port_set = true;
+  config->cli.server_port_set = true;
   return 0;
 }
 
@@ -2574,7 +2621,22 @@ static bool cli_handle_outbuf_option(CliParseCtx* ctx) {
  * load --files-from once every argument has been seen.  Returns 0 on success,
  * -1 on error. */
 static int cli_finalize_config(Config* config, bool verbose, bool no_delta, bool no_incremental) {
-  set_log_level(config->quiet ? LOG_LEVEL_ERROR : (verbose ? LOG_LEVEL_DEBUG : LOG_LEVEL_WARNING));
+  /* An explicit --debug=FLAGS enables the debug log level by itself (rsync
+     behaviour); -v enables every other INFO-level message. */
+  bool debug_enabled = verbose || config->debug_level != 0;
+  set_log_level(config->quiet ? LOG_LEVEL_ERROR
+                              : (debug_enabled ? LOG_LEVEL_DEBUG : LOG_LEVEL_WARNING));
+  /* rsync parity: --delay-updates implies --delete-after.  Every staged file is
+     published first and only then are extras removed.  Normalize onto the
+     existing delete_after wire bool (no new wire field), overriding any other
+     explicit timing exactly as rsync does; without --delete there is no
+     deletion, so no timing is set (and the wire config stays valid). */
+  if (config->delay_updates && config->use_delete) {
+    config->delete_before = false;
+    config->delete_during = false;
+    config->delete_delay = false;
+    config->delete_after = true;
+  }
   /* rsync's plain --delete defaults to delete-during (--del): each directory's
      extras are removed as that directory is processed, so space is freed
      progressively and a tight destination never has to hold the whole old+new
@@ -2587,6 +2649,15 @@ static int cli_finalize_config(Config* config, bool verbose, bool no_delta, bool
   if (config->use_delete && !config->delete_before && !config->delete_during &&
       !config->delete_delay && !config->delete_after)
     config->delete_during = true;
+  /* rsync parity: --partial-dir=DIR chooses where an interrupted transfer's
+     partial file is kept, so it implies --partial.  rsync applies the
+     implication after option parsing, so it wins over an explicit --no-partial
+     regardless of the order the two options appear in (verified on rsync
+     3.4.1).  --inplace is the exception: the destination file is written in
+     place with no partial/temp staging, so the partial machinery is bypassed
+     and the implication is skipped to leave --inplace behavior untouched. */
+  if (config->partial_dir && !config->inplace)
+    config->partial = true;
   if (config->compress_choice) {
     int algo = compression_algo_from_name(config->compress_choice);
     if (algo >= 0) {
@@ -2601,7 +2672,7 @@ static int cli_finalize_config(Config* config, bool verbose, bool no_delta, bool
     int resolved = compression_choice_resolve();
     if (resolved < 0) {
       log_message(LOG_LEVEL_ERROR, "RSYNC_COMPRESS_LIST names no supported compression algorithm");
-      config->cli_exit_code = 4;
+      config->cli.cli_exit_code = 4;
       return -1;
     }
     config->compression_algo = resolved;
@@ -2612,7 +2683,7 @@ static int cli_finalize_config(Config* config, bool verbose, bool no_delta, bool
    * clamped to the codec's range, otherwise the codec's own default is used. */
   if (config->use_compression) {
     CompressionAlgo algo = (CompressionAlgo)config->compression_algo;
-    config->compression_level = config->compression_level_set
+    config->compression_level = config->cli.compression_level_set
                                     ? compression_clamp_level(algo, config->compression_level)
                                     : compression_default_level(algo);
     log_debug_message(LOG_DEBUG_UTIL, "Client compression: %s (level %d)",
@@ -2621,22 +2692,22 @@ static int cli_finalize_config(Config* config, bool verbose, bool no_delta, bool
   /* The negotiated checksum is always resolved (rsync negotiates one for the
    * delta strong sum even without --checksum): RSYNC_CHECKSUM_LIST first, then
    * the compiled-in order.  An explicit --checksum-choice already set it. */
-  if (!config->checksum_choice_set) {
+  if (!config->cli.checksum_choice_set) {
     int resolved = checksum_choice_resolve();
     if (resolved < 0) {
       log_message(LOG_LEVEL_ERROR, "RSYNC_CHECKSUM_LIST names no supported checksum algorithm");
-      config->cli_exit_code = 4;
+      config->cli.cli_exit_code = 4;
       return -1;
     }
     config->checksum_algo = resolved;
-    config->checksum_transfer_algo = resolved;
+    config->cli.checksum_transfer_algo = resolved;
   }
   /* rsync parity: "none" as the pre-transfer checksum cannot be combined with
    * --checksum (exit 4).  The check runs here because --checksum may appear on
    * either side of --checksum-choice. */
   if (config->checksum && config->checksum_algo == (int)CHECKSUM_ALGO_NONE) {
     log_message(LOG_LEVEL_ERROR, "Invalid checksum-choice for --checksum: none");
-    config->cli_exit_code = 4;
+    config->cli.cli_exit_code = 4;
     return -1;
   }
 
@@ -2715,11 +2786,11 @@ static int cli_finalize_config(Config* config, bool verbose, bool no_delta, bool
    * explicitly negated them (--no-perms/--no-times/--no-preserve).  This runs
    * BEFORE the derived use_metadata bit so the transport frame is still sent
    * for the incremental/delta handshake even when both attributes were negated
-   * via --no-preserve (metadata_explicitly_disabled handles that opt-out). */
-  if (preserve_implied && !config->metadata_explicitly_disabled) {
-    if (!config->preserve_perms_explicit_off)
+   * via --no-preserve (cli.metadata_explicitly_disabled handles that opt-out). */
+  if (preserve_implied && !config->cli.metadata_explicitly_disabled) {
+    if (!config->cli.preserve_perms_explicit_off)
       config->preserve_perms = true;
-    if (!config->preserve_times_explicit_off)
+    if (!config->cli.preserve_times_explicit_off)
       config->preserve_times = true;
   }
 
@@ -2747,8 +2818,11 @@ static int cli_finalize_config(Config* config, bool verbose, bool no_delta, bool
    * need the pre-transfer destination snapshot (new vs modified and which
    * attributes differ), so ask the receiver to report it on every per-file
    * check.  This is a wire field. */
+  bool progress_active =
+      !config->quiet && (config->show_progress || (config->info_level & LOG_INFO_PROGRESS) != 0);
   config->report_dest_info = config->itemize_changes || config->out_format != NULL ||
-                             (config->log_file != NULL && config->log_file_format != NULL);
+                             (config->log_file != NULL && config->log_file_format != NULL) ||
+                             progress_active;
   /* Wire-stats parity: --stats, --progress/-P, an --out-format token that needs
    * a wire counter (%b/%c), or a dry-run --delete need the receiver's
    * end-of-transfer STATUS_STATS report.  This is a wire field (protocol
@@ -2764,10 +2838,12 @@ static int cli_finalize_config(Config* config, bool verbose, bool no_delta, bool
   }
   /* --info=del on a real --delete run asks the receiver to report the paths it
      actually removed; the report rides the STATUS_STATS path list, so the wire
-     stats frame must be negotiated too. */
-  config->report_deletes = config->use_delete && !config->dry_run &&
-                           ((config->info_level & LOG_INFO_DEL) != 0 || config->itemize_changes ||
-                            config->out_format != NULL);
+     stats frame must be negotiated too.  --debug=del needs the same paths, so
+     it opts into the existing report (no new wire field). */
+  config->report_deletes =
+      config->use_delete && !config->dry_run &&
+      ((config->info_level & LOG_INFO_DEL) != 0 || config->itemize_changes ||
+       config->out_format != NULL || (config->debug_level & LOG_DEBUG_DEL) != 0);
   config->report_stats = config->stats || config->show_progress ||
                          (config->info_level & LOG_INFO_PROGRESS) || format_needs_wire ||
                          config->report_deletes || (config->dry_run && config->use_delete);
@@ -3104,7 +3180,7 @@ int main(int argc, char* argv[]) {
   int parse_ret = parse_args(config, argc, argv, positional_args, &positional_count);
   if (parse_ret != 0) {
     if (parse_ret < 0)
-      exit_code = config->cli_exit_code ? config->cli_exit_code : 1;
+      exit_code = config->cli.cli_exit_code ? config->cli.cli_exit_code : 1;
     goto cleanup;
   }
 
@@ -3247,7 +3323,7 @@ int main(int argc, char* argv[]) {
       exit_code = 1;
     }
   } else if (config->use_multithreading) {
-    exit_code = send_files_multithreaded(&config);
+    exit_code = send_files_multithreaded(config);
   } else {
     exit_code = send_files(config);
   }

src/client/client_manifest.c

@@ -0,0 +1,679 @@
+#include "client_send_internal.h"
+#include "array_list.h"
+#include "change_list.h"
+#include "charset.h"
+#include "config.h"
+#include "data.h"
+#include "delta.h"
+#include "file.h"
+#include "format.h"
+#include "log.h"
+#include "protocol.h"
+#include "scanner.h"
+#include "transport_tls.h"
+#include "utils.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <time.h>
+
+/* True when --dry-run should contact a receiver rather than running the
+ * client-side local manifest.  Any target a real run would reach over the wire
+ * selects the server-contacting path: a remote (SSH host:path), a daemon
+ * (host::module/path), an explicit --server-host, --server-port/--port, TLS, or
+ * a source-bind --address.  A plain local destination (none of these) keeps the
+ * original client-side behavior, which never dials the default 127.0.0.1:8080. */
+bool dry_run_targets_server(const Config* config) {
+  if (!config)
+    return false;
+  if (config->transport == TRANSPORT_SSH)
+    return true;
+  if (config->module && config->module[0] != '\0')
+    return true;
+  if (config->cli.server_host_set || config->cli.server_port_set)
+    return true;
+  if (config->use_tls)
+    return true;
+  if (config->address != NULL)
+    return true;
+  return false;
+}
+
+bool add_chunk_to_manifest(ArrayList* manifest, const Chunk* chunk) {
+  if (!manifest)
+    return true;
+  for (int i = 0; i < chunk->element_count; i++) {
+    const char* path = file_wire_path(chunk->items[i]);
+    if (*path == '/')
+      path++;
+    char* entry = str_dup(path);
+    if (!entry) {
+      log_message(LOG_LEVEL_ERROR, "Failed to allocate manifest entry");
+      return false;
+    }
+    if (!array_list_add(manifest, entry)) {
+      free(entry);
+      return false;
+    }
+  }
+  return true;
+}
+
+/* Print dry-run manifest showing files that would be transferred. Returns 0 on success. */
+int send_dry_run_manifest(const Config* config) {
+  int skipped = 0;
+  ArrayList* missing_dest = NULL;
+  if (!client_prepare_files_from(config, &missing_dest, &skipped))
+    return -1;
+  PreparedScanner prepared;
+  if (!prepare_scanner(config, 0, &prepared)) {
+    if (missing_dest)
+      array_list_delete(missing_dest);
+    return -1;
+  }
+  DirectoryScanner* scanner =
+      directory_scanner_create_with_options(config->send_directory, &prepared.options);
+  if (!scanner) {
+    prepared_scanner_destroy(&prepared);
+    if (missing_dest)
+      array_list_delete(missing_dest);
+    return -1;
+  }
+  Chunk* chunk;
+  int file_count = 0;
+  unsigned long long total_bytes = 0;
+  char size_buffer[32];
+  if (!config->quiet)
+    printf("Dry run: files to be transferred\n");
+  while ((chunk = directory_scanner_next(scanner)) != NULL) {
+    for (int i = 0; i < chunk->element_count; i++) {
+      if (!config->quiet) {
+        char* escaped_path =
+            output_escape(file_wire_path(chunk->items[i]), config->eight_bit_output);
+        if (!escaped_path) {
+          chunk_destroy(chunk);
+          directory_scanner_destroy(scanner);
+          prepared_scanner_destroy(&prepared);
+          if (missing_dest)
+            array_list_delete(missing_dest);
+          return -1;
+        }
+        if (config->human_readable)
+          printf(
+              "  %s (%s)\n", escaped_path,
+              display_bytes(chunk->items[i]->data->size, true, size_buffer, sizeof(size_buffer)));
+        else
+          printf("  %s (%zu bytes)\n", escaped_path, chunk->items[i]->data->size);
+        free(escaped_path);
+      }
+      total_bytes += chunk->items[i]->data->size;
+      file_count++;
+    }
+    chunk_destroy(chunk);
+  }
+  directory_scanner_destroy(scanner);
+  prepared_scanner_destroy(&prepared);
+  /* --delete-missing-args: the missing entries' destination mirrors render as
+     would-be deletions (rsync's dry-run also lists its *deleting lines). */
+  if (missing_dest && !config->quiet) {
+    for (int i = 0; i < missing_dest->size; i++) {
+      char* escaped = output_escape((char*)missing_dest->items[i], config->eight_bit_output);
+      printf("  %s (missing; would be deleted)\n", escaped ? escaped : "<allocation failed>");
+      free(escaped);
+    }
+  }
+  if (missing_dest)
+    array_list_delete(missing_dest);
+  if (!config->quiet) {
+    if (config->human_readable)
+      printf("Total: %d files, %s\n", file_count,
+             display_bytes(total_bytes, true, size_buffer, sizeof(size_buffer)));
+    else
+      printf("Total: %d files, %.1f MB\n", file_count, (double)total_bytes / (double)BYTES_PER_MIB);
+  }
+  return 0;
+}
+
+typedef struct {
+  char* name; /* transfer-relative name ("" == the source root) */
+  mode_t mode;
+  unsigned long long size;
+  time_t mtime;
+  long mtime_nsec;
+  bool is_dir;
+  bool is_symlink;
+  char* link_target;
+} ListEntry;
+
+static void list_entries_destroy(ListEntry* entries, size_t count) {
+  if (entries == NULL)
+    return;
+  for (size_t i = 0; i < count; i++) {
+    free(entries[i].name);
+    free(entries[i].link_target);
+  }
+  free(entries);
+}
+
+static int compare_list_entries(const void* left, const void* right) {
+  const ListEntry* a = (const ListEntry*)left;
+  const ListEntry* b = (const ListEntry*)right;
+  return strcmp(a->name, b->name);
+}
+
+/* Relative path of an entry below `root` ("" for the root itself).  Mirrors
+ * change_list's relative_name for list-only rendering. */
+static char* list_relative_name(const char* root, const char* full) {
+  if (root == NULL || full == NULL)
+    return str_dup(full != NULL ? full : "");
+  size_t root_len = strlen(root);
+  while (root_len > 1 && root[root_len - 1] == '/')
+    root_len--;
+  if (strncmp(root, full, root_len) == 0) {
+    if (full[root_len] == '\0')
+      return str_dup("");
+    if (full[root_len] == '/')
+      return str_dup(full + root_len + 1);
+  }
+  return str_dup(full);
+}
+
+/* --list-only: print an ls-style listing of the entries that WOULD be
+ * transferred and exit without contacting the server or writing anything.
+ * Names are transfer-relative (rsync prints `a.txt`, `sub/b.txt`, `.`) and
+ * directory entries are included.  Returns 0 on success, 1 on error. */
+int send_list_only(const Config* config) {
+  int skipped = 0;
+  if (!files_from_list_check(config, NULL, &skipped))
+    return 1;
+  PreparedScanner prepared;
+  if (!prepare_scanner(config, 0, &prepared))
+    return 1;
+  prepared.options.use_metadata = true; /* capture mode + mtime for the listing */
+  prepared.options.list_dirs = true;
+  DirectoryScanner* scanner =
+      directory_scanner_create_with_options(config->send_directory, &prepared.options);
+  if (!scanner) {
+    prepared_scanner_destroy(&prepared);
+    return 1;
+  }
+  ListEntry* entries = NULL;
+  size_t count = 0;
+  size_t capacity = 0;
+  bool oom = false;
+
+  /* rsync lists the source root itself (as ".").  Only when the source is a
+   * directory and no --files-from subset is in effect. */
+  if (config->files_from_set == NULL && config->send_directory != NULL) {
+    struct stat st;
+    if (stat(config->send_directory, &st) == 0 && S_ISDIR(st.st_mode)) {
+      capacity = 64;
+      entries = calloc(capacity, sizeof(ListEntry));
+      if (entries == NULL) {
+        oom = true;
+      } else if ((entries[0].name = str_dup("")) == NULL) {
+        /* A NULL name would be dereferenced by qsort/render: fail the listing. */
+        oom = true;
+      } else {
+        entries[0].mode = st.st_mode;
+        entries[0].mtime = st.st_mtime;
+        entries[0].mtime_nsec = st.st_mtim.tv_nsec;
+        entries[0].size = (unsigned long long)st.st_size;
+        entries[0].is_dir = true;
+        count = 1;
+      }
+    }
+  }
+
+  Chunk* chunk;
+  while (!oom && (chunk = directory_scanner_next(scanner)) != NULL) {
+    for (int i = 0; i < chunk->element_count; i++) {
+      File* f = chunk->items[i];
+      if (f == NULL)
+        continue;
+      if (count == capacity) {
+        size_t new_capacity = capacity > 0 ? capacity * 2 : 64;
+        if (new_capacity <= capacity) {
+          oom = true;
+          break;
+        }
+        ListEntry* grown = realloc(entries, new_capacity * sizeof(ListEntry));
+        if (!grown) {
+          oom = true;
+          break;
+        }
+        entries = grown;
+        memset(entries + capacity, 0, (new_capacity - capacity) * sizeof(ListEntry));
+        capacity = new_capacity;
+      }
+      char* name = list_relative_name(config->send_directory, file_wire_path(f));
+      if (!name) {
+        oom = true;
+        break;
+      }
+      mode_t mode = 0;
+      time_t mtime = 0;
+      long mtime_nsec = 0;
+      if (f->metadata != NULL) {
+        mode = f->metadata->mode;
+        mtime = f->metadata->mtime_sec;
+        mtime_nsec = f->metadata->mtime_nsec;
+      } else {
+        struct stat st;
+        if (lstat(f->path, &st) == 0) {
+          mode = st.st_mode;
+          mtime = st.st_mtime;
+          mtime_nsec = st.st_mtim.tv_nsec;
+        }
+      }
+      entries[count].name = name;
+      entries[count].mode = mode;
+      entries[count].mtime = mtime;
+      entries[count].mtime_nsec = mtime_nsec;
+      if (f->is_symlink)
+        entries[count].size = f->symlink_target != NULL ? strlen(f->symlink_target) : 0;
+      else if (f->is_dir) {
+        struct stat dir_st;
+        entries[count].size = stat(f->path, &dir_st) == 0 ? (unsigned long long)dir_st.st_size : 0;
+      } else
+        entries[count].size = f->data != NULL ? f->data->size : 0;
+      entries[count].is_dir = f->is_dir;
+      entries[count].is_symlink = f->is_symlink;
+      entries[count].link_target =
+          f->is_symlink && f->symlink_target ? str_dup(f->symlink_target) : NULL;
+      count++;
+    }
+    chunk_destroy(chunk);
+  }
+  bool failed = oom || directory_scanner_failed(scanner) || directory_scanner_had_io_error(scanner);
+  directory_scanner_destroy(scanner);
+  prepared_scanner_destroy(&prepared);
+  if (failed) {
+    list_entries_destroy(entries, count);
+    if (oom)
+      log_message(LOG_LEVEL_ERROR, "memory allocation failed while listing");
+    return 1;
+  }
+  if (count > 1)
+    qsort(entries, count, sizeof(ListEntry), compare_list_entries);
+  for (size_t i = 0; i < count; i++) {
+    ChangeEvent event;
+    memset(&event, 0, sizeof(event));
+    event.name = entries[i].name;
+    event.path = entries[i].name;
+    event.mode = entries[i].mode;
+    event.size = entries[i].size;
+    event.mtime_sec = entries[i].mtime;
+    event.mtime_nsec = entries[i].mtime_nsec;
+    event.is_directory = entries[i].is_dir;
+    event.is_symlink = entries[i].is_symlink;
+    event.symlink_target = entries[i].link_target;
+    char* line = change_render_list_line(config, &event);
+    if (line != NULL) {
+      char* escaped = output_escape(line, config->eight_bit_output);
+      printf("%s\n", escaped != NULL ? escaped : line);
+      free(escaped);
+      free(line);
+    }
+  }
+  list_entries_destroy(entries, count);
+  return 0;
+}
+
+/* Send the delete manifest to the server.  Returns 0 on success, -1 on
+   failure.  It carries FOUR path sections (keep-set paths, protected excluded
+   prefixes, --delete-missing-args exact-delete paths, and the destination-
+   relative directories the sender synchronized this run) followed by the
+   protocol-2.30.0 per-directory filter-rule block (`per_dir_rules`, the rules
+   the scan compiled from each directory's merge files).
+   When --delete-excluded is given `protected` is empty: excluded destination
+   mirrors are then ordinary extras and are removed.  When
+   --delete-missing-args is active `missing_args` holds the destination mirrors
+   of missing --files-from entries: each is an explicit receiver-side deletion
+   request, independent of the extras walk.  `synced_dirs` confines the extras
+   walk to entries directly inside a synchronized directory.  A NULL
+   keep-set / protected / missing / dirs list transmits an empty section.  All
+   four sections are unbounded on the sender; the receiver enforces
+   MAX_MANIFEST_ENTRIES per section and a single MAX_MANIFEST_BYTES budget
+   shared across the sections, rejecting (with STATUS_ERROR) an over-budget
+   frame.  A heavily filtered source whose exclusion list is large therefore
+   fails the run cleanly on the receiver rather than being truncated. */
+int send_delete_manifest(int fd, ArrayList* manifest, ArrayList* protected_prefixes,
+                         ArrayList* size_skipped, ArrayList* missing_args, ArrayList* synced_dirs,
+                         const FilterRuleList* per_dir_rules) {
+  if (!send_status(fd, STATUS_MANIFEST))
+    return -1;
+  int keep_count = manifest ? manifest->size : 0;
+  if (!send_int(fd, keep_count))
+    return -1;
+  for (int i = 0; i < keep_count; i++) {
+    if (!send_wire_str(fd, (char*)manifest->items[i]))
+      return -1;
+  }
+  /* The receiver has ONE protected-prefix section; filter-excluded prefixes
+     (dropped under --delete-excluded) and size-pruned prefixes (always
+     protected) are concatenated into it. */
+  int protected_count =
+      (protected_prefixes ? protected_prefixes->size : 0) + (size_skipped ? size_skipped->size : 0);
+  if (!send_int(fd, protected_count))
+    return -1;
+  if (protected_prefixes) {
+    for (int i = 0; i < protected_prefixes->size; i++) {
+      if (!send_wire_str(fd, (char*)protected_prefixes->items[i]))
+        return -1;
+    }
+  }
+  if (size_skipped) {
+    for (int i = 0; i < size_skipped->size; i++) {
+      if (!send_wire_str(fd, (char*)size_skipped->items[i]))
+        return -1;
+    }
+  }
+  int missing_count = missing_args ? missing_args->size : 0;
+  if (!send_int(fd, missing_count))
+    return -1;
+  for (int i = 0; i < missing_count; i++) {
+    if (!send_wire_str(fd, (char*)missing_args->items[i]))
+      return -1;
+  }
+  int dirs_count = synced_dirs ? synced_dirs->size : 0;
+  if (!send_int(fd, dirs_count))
+    return -1;
+  for (int i = 0; i < dirs_count; i++) {
+    if (!send_wire_str(fd, (char*)synced_dirs->items[i]))
+      return -1;
+  }
+  /* Protocol 2.30.0: the receiver-side per-directory filter rules discovered by
+     the sender's scan, so the whole-tree commit walker can shield a
+     destination-only entry that matches only a per-directory merge rule. */
+  if (!delete_filter_dir_rules_send(fd, per_dir_rules))
+    return -1;
+  return 0;
+}
+
+/* Transmit the keep-set manifest and wait for the receiver's verdict.  Used by
+   --delete-before/--delete-during, where the extras are removed on the receiver
+   BEFORE the first byte of file data is sent: the receiver acknowledges with
+   STATUS_OK once the bounded delete committed, or STATUS_ERROR if it could not
+   (in which case the sender aborts without streaming any data).  The ACK may
+   take much longer than an ordinary per-message round trip because the receiver
+   performs the whole bounded deletion walk (up to MAX_SERVER_DELETE_COUNT
+   unlinks) before replying, so the wait uses a generous explicit deadline
+   instead of the default 60 s receive window. */
+#define DELETE_ACK_TIMEOUT_SEC 3600
+/* While waiting for the (potentially slow) receiver-side deletion, send a
+ * STATUS_KEEPALIVE at most this often so the connection is demonstrably alive
+ * and neither side's per-message timeout trips. */
+#define DELETE_ACK_KEEPALIVE_SEC 10
+
+bool send_delete_manifest_early(Client* client, ArrayList* manifest, ArrayList* protected_prefixes,
+                                ArrayList* size_skipped, ArrayList* missing_args,
+                                ArrayList* synced_dirs, const FilterRuleList* per_dir_rules) {
+  if (!client || !manifest)
+    return false;
+  if (send_delete_manifest(client->file_descriptor, manifest, protected_prefixes, size_skipped,
+                           missing_args, synced_dirs, per_dir_rules) != 0)
+    return false;
+  Status ack;
+  /* The wait is long (up to an hour) and runs inline on this thread: a helper
+   * thread would race the non-thread-safe protocol send path, so keepalives are
+   * emitted from this wait loop itself.  A Ctrl-C/SIGTERM abort flag also ends
+   * the wait; the caller then best-effort sends STATUS_ABORT. */
+  if (!receive_status_keepalive(client->file_descriptor, &ack, DELETE_ACK_TIMEOUT_SEC,
+                                DELETE_ACK_KEEPALIVE_SEC, client_abort_pending)) {
+    /* A Ctrl-C/SIGTERM abort ends the wait above; tell the receiver before the
+       caller tears the connection down (best-effort). */
+    if (client_abort_pending()) {
+      log_info_message(LOG_INFO_MISC,
+                       "Abort requested while awaiting delete ack; sending STATUS_ABORT");
+      send_status(client->file_descriptor, STATUS_ABORT);
+    }
+    return false;
+  }
+  if (ack != STATUS_OK) {
+    log_server_rejection("Server failed to delete files before the transfer");
+    return false;
+  }
+  return true;
+}
+
+/* Server-contacting --dry-run.  Connects to the configured remote/daemon and
+ * runs the normal per-file incremental decision WITHOUT transmitting any file
+ * data: the receiver (which also sees dry_run=true on the wire) answers
+ * STATUS_OK for an up-to-date file and STATUS_DRY_RUN_TRANSFER for a file it
+ * would otherwise write, mutating nothing on either side.  The would-transfer
+ * set and the same trailer as the local dry-run are printed.  A
+ * --compare-dest exact basis hit with no destination copy is reported as a
+ * skip by the receiver.
+ *
+ * Only regular files take the receiver-consulted check; directory / symlink /
+ * special / hard-link-sibling entries have no per-file content check, so they
+ * are reported conservatively as would-transfer and their frames are never
+ * sent (which is what keeps the receiver mutation-free).  --delete* is
+ * deliberately NOT transmitted in dry-run, so no deletion can occur; the
+ * would-delete manifest report is a documented follow-up.
+ *
+ * Returns 0 on success, 1 on error. */
+int send_dry_run_remote(Config* config) {
+  int from_skipped = 0;
+  ArrayList* missing_args = NULL;
+  if (!client_prepare_files_from(config, &missing_args, &from_skipped))
+    return 1;
+  if (missing_args)
+    array_list_delete(missing_args);
+  /* A live session may follow, so arm graceful abort handling. */
+  client_set_abort_armed(true);
+  ProtocolSession session;
+  Client* client = client_connect_and_bind_session(config, &session);
+  if (!client) {
+    client_set_abort_armed(false);
+    return 1;
+  }
+
+  int ret = 1;
+  bool partial = false;
+  time_t dry_start = time(NULL);
+  ReceiverStats dry_stats;
+  memset(&dry_stats, 0, sizeof(dry_stats));
+  PreparedScanner prepared;
+  memset(&prepared, 0, sizeof(prepared));
+  DirectoryScanner* scanner = NULL;
+  ArrayList* dry_manifest = NULL;
+  ArrayList* dry_dirs = NULL;
+  ArrayList* dry_excluded = NULL;
+  ArrayList* dry_size_skipped = NULL;
+  FilterRuleList* dry_per_dir = NULL;
+  if (!config_send(client->file_descriptor, config))
+    goto dry_fail;
+  receive_daemon_motd(client, config);
+  if (!prepare_scanner(config, 0, &prepared))
+    goto dry_fail;
+  /* -n --delete: build the same keep-set manifest, protected prefixes, and
+     synchronized-directory scope a real run would send, so the receiver's
+     read-only extras walk enumerates exactly the deletions a real run makes. */
+  if (config->use_delete) {
+    dry_manifest = array_list_create(free);
+    dry_dirs = array_list_create(free);
+    dry_size_skipped = array_list_create(free);
+    dry_per_dir = filter_rule_list_create();
+    if (!dry_manifest || !dry_dirs || !dry_size_skipped || !dry_per_dir)
+      goto dry_fail;
+    prepared.options.per_dir_rules = dry_per_dir;
+    if (!config->delete_excluded) {
+      dry_excluded = array_list_create(free);
+      if (!dry_excluded)
+        goto dry_fail;
+      prepared.options.excluded_paths = dry_excluded;
+    }
+    prepared.options.size_skipped_paths = dry_size_skipped;
+    /* A --files-from subset confines the extras walk to the directories the
+       scan synchronized; a full recursive transfer marks the root itself. */
+    if (config->files_from_set == NULL) {
+      char* root_marker = delete_scope_root_marker(config);
+      if (!root_marker || !array_list_add(dry_dirs, root_marker)) {
+        free(root_marker);
+        goto dry_fail;
+      }
+    } else {
+      prepared.options.synced_dirs = dry_dirs;
+    }
+  }
+  scanner = directory_scanner_create_with_options(config->send_directory, &prepared.options);
+  if (!scanner)
+    goto dry_fail;
+
+  int file_count = 0;
+  unsigned long long total_bytes = 0;
+  char size_buffer[32];
+  if (!config->quiet)
+    printf("Dry run: files to be transferred\n");
+  Chunk* chunk;
+  while ((chunk = directory_scanner_next(scanner)) != NULL) {
+    if (dry_manifest && !add_chunk_to_manifest(dry_manifest, chunk)) {
+      chunk_destroy(chunk);
+      goto dry_fail;
+    }
+    for (int i = 0; i < chunk->element_count; i++) {
+      File* f = chunk->items[i];
+      if (!f)
+        continue;
+      unsigned long long fsize = f->data ? f->data->size : 0;
+      bool would;
+      if (f->is_dir || f->is_symlink || f->is_special ||
+          (f->link_group != 0 && !f->link_first && f->hardlink_target != NULL)) {
+        /* No receiver-side content check exists for these frame types; a real
+           run would (re)create them, so report would-transfer and send no
+           frame (the receiver must stay mutation-free). */
+        would = true;
+      } else if (fsize > MAX_RECEIVE_WHOLE_FILE_SIZE && !config->use_incremental &&
+                 !config_has_basis(config)) {
+        /* A non-incremental run streams a >whole-file-limit source without the
+           STATUS_CHECK handshake, so no read-only receiver decision is possible
+           (and none is needed: a real run would transfer it). */
+        would = true;
+      } else {
+        DeltaSignature* sig = NULL;
+        unsigned long long resume_offset = 0;
+        int rc = incremental_check(client, f, config, &sig, &resume_offset);
+        delta_signature_destroy(sig);
+        if (rc < 0) {
+          chunk_destroy(chunk);
+          goto dry_fail;
+        }
+        if (rc == 1)
+          continue; /* up to date; nothing to report */
+        if (rc != 4) {
+          log_message(LOG_LEVEL_ERROR, "Unexpected receiver reply during dry-run");
+          chunk_destroy(chunk);
+          goto dry_fail;
+        }
+        would = true;
+      }
+      if (would) {
+        if (!config->quiet) {
+          char* escaped_path = output_escape(file_wire_path(f), config->eight_bit_output);
+          if (!escaped_path) {
+            chunk_destroy(chunk);
+            goto dry_fail;
+          }
+          if (config->human_readable)
+            printf("  %s (%s)\n", escaped_path,
+                   display_bytes(fsize, true, size_buffer, sizeof(size_buffer)));
+          else
+            printf("  %s (%llu bytes)\n", escaped_path, fsize);
+          free(escaped_path);
+        }
+        total_bytes += fsize;
+        file_count++;
+      }
+    }
+    chunk_destroy(chunk);
+  }
+  bool io_error = directory_scanner_had_io_error(scanner);
+  if (directory_scanner_failed(scanner))
+    goto dry_fail;
+  if (io_error)
+    log_message(LOG_LEVEL_WARNING, "source scan hit an unreadable directory");
+  /* Send the keep-set manifest (no data frames) so the receiver can enumerate
+     the destination extras; an early-timing delete ACKs before it will accept
+     the terminal FINISHED. */
+  bool early_delete = config->use_delete && config_delete_timing_early(config);
+  if (dry_manifest) {
+    if (send_delete_manifest(client->file_descriptor, dry_manifest, dry_excluded, dry_size_skipped,
+                             NULL, dry_dirs, dry_per_dir) != 0)
+      goto dry_fail;
+    if (early_delete) {
+      Status ack;
+      if (!receive_status_keepalive(client->file_descriptor, &ack, DELETE_ACK_TIMEOUT_SEC,
+                                    DELETE_ACK_KEEPALIVE_SEC, client_abort_pending) ||
+          ack != STATUS_OK)
+        goto dry_fail;
+    }
+  }
+  /* Terminate the stream so the receiver emits its success frame; no data frame
+     is ever sent in dry-run. */
+  if (!send_status(client->file_descriptor, STATUS_FINISHED))
+    goto dry_fail;
+  Status status;
+  if (!receive_status(client->file_descriptor, &status))
+    goto dry_fail;
+  if (status == STATUS_STATS) {
+    ArrayList* would_delete = array_list_create(free);
+    if (!would_delete)
+      goto dry_fail;
+    if (!receive_stats_record(client->file_descriptor, &dry_stats, would_delete)) {
+      array_list_delete(would_delete);
+      goto dry_fail;
+    }
+    print_delete_reports(config, would_delete);
+    array_list_delete(would_delete);
+    if (!receive_status(client->file_descriptor, &status))
+      goto dry_fail;
+  }
+  /* A per-entry receiver failure is rsync's PARTIAL transfer (exit 23), not a
+     hard failure: a dry run transfers nothing, but keep the verdict consistent
+     with the normal path instead of treating it as a protocol error. */
+  if (status == STATUS_PARTIAL) {
+    partial = true;
+  } else if (status != STATUS_OK) {
+    goto dry_fail;
+  }
+  if (!config->quiet) {
+    if (config->human_readable)
+      printf("Total: %d files, %s\n", file_count,
+             display_bytes(total_bytes, true, size_buffer, sizeof(size_buffer)));
+    else
+      printf("Total: %d files, %.1f MB\n", file_count, (double)total_bytes / (double)BYTES_PER_MIB);
+  }
+  {
+    TransferStats dry_transfer;
+    memset(&dry_transfer, 0, sizeof(dry_transfer));
+    dry_transfer.flist_reg = (unsigned long long)file_count;
+    dry_transfer.total_file_size = total_bytes;
+    dry_transfer.transferred_regular = (unsigned long long)file_count;
+    dry_transfer.transferred_file_size = total_bytes;
+    dry_transfer.literal_data = total_bytes;
+    report_transfer_stats(config, &dry_transfer, dry_start, &dry_stats);
+  }
+  ret = io_error ? 1 : (partial ? 23 : 0);
+
+dry_fail:
+  if (dry_manifest)
+    array_list_delete(dry_manifest);
+  if (dry_dirs)
+    array_list_delete(dry_dirs);
+  if (dry_excluded)
+    array_list_delete(dry_excluded);
+  if (dry_size_skipped)
+    array_list_delete(dry_size_skipped);
+  if (dry_per_dir)
+    filter_rule_list_free(dry_per_dir);
+  if (scanner)
+    directory_scanner_destroy(scanner);
+  prepared_scanner_destroy(&prepared);
+  disconnect_transfer_client(client);
+  protocol_session_unbind();
+  client_set_abort_armed(false);
+  return ret;
+}

src/client/client_scan.c

@@ -0,0 +1,470 @@
+#include "client_send_internal.h"
+#include "array_list.h"
+#include "charset.h"
+#include "config.h"
+#include "delete_plan.h"
+#include "file.h"
+#include "file_list.h"
+#include "filter.h"
+#include "hardlink.h"
+#include "log.h"
+#include "scanner.h"
+#include "utils.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+
+/* Build the scanner options for one scan. Returns false and logs on failure. */
+bool prepare_scanner(const Config* config, int num_threads, PreparedScanner* out) {
+  if (!out)
+    return false;
+  out->base_filters = NULL;
+  out->hardlinks = NULL;
+  out->relative_prefix = NULL;
+  memset(&out->options, 0, sizeof(out->options));
+
+  int rule_count = config->filters ? config->filters->size : 0;
+  const char** texts = NULL;
+  if (rule_count > 0) {
+    texts = malloc((size_t)rule_count * sizeof(char*));
+    if (!texts) {
+      log_message(LOG_LEVEL_ERROR, "memory allocation failed for filter rules");
+      return false;
+    }
+    for (int i = 0; i < rule_count; i++)
+      texts[i] = (const char*)config->filters->items[i];
+  }
+  if (rule_count > 0 || config->cvs_exclude) {
+    char err[160];
+    out->base_filters = filter_base_build(texts, rule_count, config->cvs_exclude,
+                                          config->delete_excluded, err, sizeof(err));
+    free(texts);
+    if (!out->base_filters) {
+      log_message(LOG_LEVEL_ERROR, "invalid filter rule: %s", err);
+      return false;
+    }
+  } else {
+    free(texts);
+  }
+
+  ScannerOptions* options = &out->options;
+  options->use_metadata = config->use_metadata;
+  options->preserve_atimes = config->preserve_atimes;
+  options->preserve_crtimes = config->preserve_crtimes;
+  options->preserve_xattrs = config->preserve_xattrs;
+  options->preserve_acls = config->preserve_acls;
+  options->chunk_size = config->chunk_size;
+  /* --exclude/--include are compiled, in command-line order, into the SAME
+   * ordered filter rule list as --filter/-f (see config_add_selection_rule), so
+   * the legacy per-kind arrays are deliberately NOT passed to the scanner:
+   * doing so would re-apply them with the old "excludes first, then includes as
+   * a mandatory whitelist" precedence and defeat rsync's first-match-wins
+   * ordering.  The arrays remain populated purely for the Config API surface. */
+  options->exclude_patterns = NULL;
+  options->exclude_count = 0;
+  options->include_patterns = NULL;
+  options->include_count = 0;
+  options->max_size = config->max_size;
+  options->min_size = config->min_size;
+  options->max_depth = config->max_depth;
+  options->num_threads = num_threads;
+  options->follow_symlinks = config->follow_symlinks;
+  options->copy_links = config->copy_links;
+  options->safe_links = config->safe_links;
+  options->copy_unsafe_links = config->copy_unsafe_links;
+  options->copy_dirlinks = config->copy_dirlinks;
+  options->munge_links = config->munge_links;
+  options->checksum = config->checksum;
+  options->one_file_system = config->one_file_system;
+  options->preserve_devices = config->preserve_devices;
+  options->preserve_specials = config->preserve_specials;
+  options->copy_devices = config->copy_devices;
+  options->file_list = (const FileListSet*)config->files_from_set;
+  options->base_filters = out->base_filters;
+  options->per_dir_filters = config->per_dir_filter;
+  options->delete_excluded = config->delete_excluded;
+  options->exclude_per_dir_filter_files = config->per_dir_filter_count >= 2;
+  options->dirs = config->dirs;
+  options->relative = config->relative;
+  /* A real recursive transfer recreates empty source directories (rsync
+     parity); low-level scanner users leave this off. */
+  options->emit_empty_dirs = true;
+  /* --no-implied-dirs only has meaning with -R (rsync): without it the option
+     is a documented no-op, so the scanner must not suppress directory
+     metadata. */
+  options->no_implied_dirs = config->no_implied_dirs && config->relative;
+  /* -R/--relative outside --files-from reconstructs every destination path from
+   * the source spec (rsync's '/./' cut point).  With --files-from the listed
+   * entry already supplies the bare relative path, so no prefix is built. */
+  if (config->relative && config->files_from_set == NULL && config->send_directory) {
+    out->relative_prefix = scanner_relative_prefix(config->send_directory);
+    if (!out->relative_prefix) {
+      log_message(LOG_LEVEL_ERROR, "memory allocation failed building --relative path prefix");
+      filter_rule_list_free(out->base_filters);
+      out->base_filters = NULL;
+      return false;
+    }
+    options->relative_prefix = out->relative_prefix;
+  }
+  options->prune_empty_dirs = config->prune_empty_dirs;
+  options->ignore_io_errors = config->ignore_errors;
+  options->ignore_missing_args = config->ignore_missing_args || config->delete_missing_args;
+  options->note_nonreg = (config->info_level & LOG_INFO_NONREG) != 0 && !config->quiet;
+  options->note_mount = (config->info_level & LOG_INFO_MOUNT) != 0 && !config->quiet;
+  options->send_directory = config->send_directory;
+  options->eight_bit_output = config->eight_bit_output;
+  options->excluded_paths = NULL;
+  options->excluded_mutex = NULL;
+  options->size_skipped_paths = NULL;
+  options->synced_dirs = NULL;
+  options->hardlinks = NULL;
+  /* Set by the real send paths; NULL for the metadata-only scans (progress
+     pre-count, batch) that must not perturb the sender's --stats counter. */
+  options->dir_count = NULL;
+  /* P7 Wave D: capture source directory metadata when a directory attribute is
+     requested (-p for modes, -t for times unless -O omits them).  Whether they
+     are APPLIED is decided receiver-side. */
+  options->capture_dir_times = dir_metadata_should_capture(config);
+  options->dir_entries = NULL;
+  options->dir_entries_mutex = NULL;
+  if (config->preserve_hard_links) {
+    out->hardlinks = hardlink_table_create();
+    if (!out->hardlinks) {
+      filter_rule_list_free(out->base_filters);
+      out->base_filters = NULL;
+      return false;
+    }
+    options->hardlinks = out->hardlinks;
+  }
+  return true;
+}
+
+void prepared_scanner_destroy(PreparedScanner* prepared) {
+  if (!prepared)
+    return;
+  filter_rule_list_free(prepared->base_filters);
+  prepared->base_filters = NULL;
+  hardlink_table_destroy(prepared->hardlinks);
+  prepared->hardlinks = NULL;
+  free(prepared->relative_prefix);
+  prepared->relative_prefix = NULL;
+}
+
+/* -R/--relative implied directories: rsync transmits the metadata of the
+ * parent directories implied by the source path (every prefix component above
+ * the source root) so the receiver applies their attributes to the created
+ * parents.  FastSync's scan only covers the source root and below, so append
+ * one metadata-only directory entry per implied ancestor.  --no-implied-dirs
+ * suppresses this exactly like rsync.  A missing ancestor is never fatal. */
+bool append_implied_dir_times(const Config* config, ArrayList* dir_entries) {
+  if (!dir_entries || !config->relative || config->files_from_set != NULL ||
+      config->no_implied_dirs || !config->send_directory)
+    return true;
+  char* prefix = scanner_relative_prefix(config->send_directory);
+  if (!prefix)
+    return true;
+  int ncomp = 0;
+  for (const char* s = prefix; *s;) {
+    while (*s == '/')
+      s++;
+    if (!*s)
+      break;
+    while (*s && *s != '/')
+      s++;
+    ncomp++;
+  }
+  if (ncomp <= 1) {
+    free(prefix);
+    return true;
+  }
+  char* fs = str_dup(config->send_directory);
+  if (!fs) {
+    free(prefix);
+    return true;
+  }
+  size_t flen = strlen(fs);
+  while (flen > 1 && fs[flen - 1] == '/')
+    fs[--flen] = '\0';
+  bool ok = true;
+  /* Walk the source path upwards one component at a time (fs is truncated in
+     place, so each step targets the next implied ancestor). */
+  for (int depth = ncomp - 2; depth >= 0 && ok; depth--) {
+    char* slash = strrchr(fs, '/');
+    if (!slash || slash == fs)
+      break;
+    *slash = '\0';
+    char* p = prefix;
+    int c = 0;
+    while (c <= depth) {
+      while (*p == '/')
+        p++;
+      while (*p && *p != '/')
+        p++;
+      c++;
+    }
+    char saved = *p;
+    *p = '\0';
+    struct stat st;
+    if (stat(fs, &st) == 0 && S_ISDIR(st.st_mode)) {
+      File* file = file_create(fs);
+      if (!file) {
+        ok = false;
+      } else {
+        file->is_dir = true;
+        file->metadata =
+            file_metadata_create(fs, &st, config->preserve_atimes, config->preserve_crtimes);
+        file->send_path = str_dup(prefix);
+        if (!file->metadata || !file->send_path || !array_list_add(dir_entries, file)) {
+          file_destroy(file);
+          ok = false;
+        }
+      }
+    }
+    *p = saved;
+  }
+  free(fs);
+  free(prefix);
+  return ok;
+}
+
+/* The delete-walk root scope for a full (non---files-from) transfer: rsync
+ * confines --delete to the directories it actually transferred.  A plain
+ * recursive run mirrors the source under the receive root, so "." (the whole
+ * tree) is correct; an -R run transfers only the reconstructed prefix subtree,
+ * so the walk is scoped to that prefix instead.  Returns a malloc'd wire path
+ * (or "."), or NULL on allocation failure. */
+char* delete_scope_root_marker(const Config* config) {
+  if (config->relative && config->files_from_set == NULL && config->send_directory) {
+    char* prefix = scanner_relative_prefix(config->send_directory);
+    if (!prefix)
+      return NULL;
+    if (prefix[0] != '\0')
+      return prefix;
+    free(prefix);
+  }
+  return str_dup(".");
+}
+
+/* The -R destination prefix that confines a per-directory delete walk, or NULL
+ * when the whole receive root is in scope.  The marker was installed into
+ * `synced_dirs` by delete_scope_root_marker(); for a plain recursive transfer
+ * it is "." (whole root) and for --files-from the list is not a single prefix. */
+const char* delete_plan_walk_root(const Config* config, const ArrayList* synced_dirs) {
+  if (!config || config->files_from_set != NULL || !config->relative || !config->send_directory)
+    return NULL;
+  if (!synced_dirs || synced_dirs->size != 1)
+    return NULL;
+  const char* marker = (const char*)synced_dirs->items[0];
+  if (marker[0] == '\0' || strcmp(marker, ".") == 0)
+    return NULL;
+  return marker;
+}
+
+/* The destination-relative mirror path for a missing --files-from entry: where
+   a PRESENT entry with the same name would have been written.  With -R that is
+   the entry's bare relative path (the bare wire path the receiver uses);
+   otherwise it is the full source mirror below the destination root
+   (`send_directory` joined to the entry, leading '/' stripped), exactly the
+   path the manifest records for a present sibling.  Returns an owned string, or
+   NULL on allocation failure. */
+static char* files_from_missing_dest_path(const Config* config, const char* entry) {
+  if (config->relative)
+    return str_dup(entry);
+  char* joined = path_cat(config->send_directory, entry);
+  if (!joined)
+    return NULL;
+  const char* rel = *joined == '/' ? joined + 1 : joined;
+  char* dup = str_dup(rel);
+  free(joined);
+  return dup;
+}
+
+/* --files-from semantics: every listed entry must resolve under the source
+ * root, otherwise rsync reports a hard error instead of silently transferring
+ * nothing. An entry of "." (the whole tree) and listed-but-empty directories
+ * are valid.  An empty list is valid too: rsync transfers nothing and exits 0.
+ * With --ignore-missing-args
+ * (implied by --delete-missing-args) a listed-but-missing entry is instead
+ * skipped: nothing is transferred for it, it never enters the keep-set and the
+ * run succeeds for the rest (an all-missing non-empty list succeeds
+ * transferring nothing, matching rsync).  With --delete-missing-args
+ * `missing_dest` (when non-NULL) collects the entry's destination-relative
+ * mirror for the receiver's exact-deletion request.  Runs before any
+ * transfer so the failure/skip is surfaced uniformly in the single-threaded,
+ * -m, dry-run and --list-only paths. */
+bool files_from_list_check(const Config* config, ArrayList* missing_dest, int* skipped_out) {
+  *skipped_out = 0;
+  const FileListSet* set = (const FileListSet*)config->files_from_set;
+  if (!set)
+    return true;
+  if (!config->send_directory) {
+    log_message(LOG_LEVEL_ERROR, "--files-from requires a source directory");
+    return false;
+  }
+  if (set->count == 0) {
+    /* rsync treats an empty --files-from list as "nothing to transfer" and
+       exits 0 (the source directory is still a valid source arg), so this is
+       not an error.  Nothing passes the (empty) allow-set, so no file is sent
+       and no keep-set entry is produced. */
+    return true;
+  }
+  bool ignore = config->ignore_missing_args || config->delete_missing_args;
+  for (int i = 0; i < set->count; i++) {
+    const char* entry = set->entries[i];
+    if (entry[0] == '\0')
+      continue; /* "." == list the whole tree */
+    char* full = path_cat(config->send_directory, entry);
+    if (!full) {
+      log_message(LOG_LEVEL_ERROR, "memory allocation failed while validating --files-from");
+      return false;
+    }
+    struct stat st;
+    if (lstat(full, &st) != 0) {
+      free(full);
+      if (ignore) {
+        (*skipped_out)++;
+        char* escaped_entry = output_escape(entry, log_get_8_bit_output());
+        log_info_message(LOG_INFO_MISC, "skipping missing --files-from entry '%s'",
+                         escaped_entry ? escaped_entry : "<allocation failed>");
+        free(escaped_entry);
+        if (config->delete_missing_args && missing_dest) {
+          char* mirror = files_from_missing_dest_path(config, entry);
+          if (!mirror || !array_list_add(missing_dest, mirror)) {
+            free(mirror);
+            log_message(LOG_LEVEL_ERROR, "memory allocation failed while validating --files-from");
+            return false;
+          }
+        }
+        continue;
+      }
+      char* escaped_entry = output_escape(entry, log_get_8_bit_output());
+      char* escaped_src = output_escape(config->send_directory, log_get_8_bit_output());
+      log_message(LOG_LEVEL_ERROR, "--files-from entry '%s' not found in source '%s'",
+                  escaped_entry ? escaped_entry : "<allocation failed>",
+                  escaped_src ? escaped_src : "<allocation failed>");
+      free(escaped_entry);
+      free(escaped_src);
+      return false;
+    }
+    free(full);
+  }
+  if (*skipped_out > 0) {
+    if (config->delete_missing_args) {
+      /* --list-only never deletes and a --dry-run only shows intent, so the
+         summary must not claim a real deletion happened in those modes. */
+      if (config->list_only)
+        log_message(LOG_LEVEL_WARNING,
+                    "--delete-missing-args: %d missing --files-from entr%s skipped (--list-only "
+                    "never deletes)",
+                    *skipped_out, *skipped_out == 1 ? "y" : "ies");
+      else if (config->dry_run)
+        log_message(LOG_LEVEL_WARNING,
+                    "--delete-missing-args: %d missing --files-from entr%s would be deleted from "
+                    "the destination (dry run)",
+                    *skipped_out, *skipped_out == 1 ? "y" : "ies");
+      else
+        log_message(
+            LOG_LEVEL_WARNING,
+            "--delete-missing-args: %d missing --files-from entr%s will be deleted from the "
+            "destination",
+            *skipped_out, *skipped_out == 1 ? "y" : "ies");
+    } else if (config->ignore_missing_args)
+      log_message(LOG_LEVEL_WARNING,
+                  "--ignore-missing-args: ignored %d missing --files-from entr%s", *skipped_out,
+                  *skipped_out == 1 ? "y" : "ies");
+  }
+  return true;
+}
+
+/* Walk the whole source tree once collecting only destination-relative wire
+   paths, loading and sending nothing.  --delete-before/--delete-during need the
+   complete keep-set manifest before the first data byte, so it is built by a
+   dedicated pre-scan pass and transmitted early; the data pass then re-scans
+   with a fresh scanner.  --delete-before additionally replays this very scan as
+   its data pass (rsync's single file list), so `chunks_out` (optional) retains
+   the scanned Chunk objects for the caller to send instead of destroying them;
+   the caller owns the list and must give it a chunk_destroy destructor.  A
+   source I/O error is fatal unless the options carry --ignore-errors, in which
+   case the scan continues past the unreadable directory and *io_error_out
+   reports it (the caller still performs the deletion but reports the run as
+   errored). */
+bool scan_paths_only(const Config* config, const ScannerOptions* options, ArrayList* manifest,
+                     DeletePlanSender* plans, bool* io_error_out,
+                     unsigned long long* non_dir_count_out, ArrayList* chunks_out,
+                     bool emit_nonreg) {
+  if (io_error_out)
+    *io_error_out = false;
+  if (non_dir_count_out)
+    *non_dir_count_out = 0;
+  ScannerOptions local = *options;
+  /* The pre-scan is normally a paths-only pass with no client output: it must
+     not emit --info=nonreg lines because the data pass re-scans and emits them
+     once.  When the caller replays this scan as the data pass (--delete-before)
+     there is no later scan, so it opts in and the lines are emitted here. */
+  local.note_nonreg = emit_nonreg && options->note_nonreg;
+  DirectoryScanner* scanner = directory_scanner_create_with_options(config->send_directory, &local);
+  if (!scanner)
+    return false;
+  bool ok = true;
+  Chunk* chunk;
+  while ((chunk = directory_scanner_next(scanner)) != NULL) {
+    if (non_dir_count_out) {
+      for (int i = 0; i < chunk->element_count; i++) {
+        const File* f = chunk->items[i];
+        if (f && !f->is_dir)
+          (*non_dir_count_out)++;
+      }
+    }
+    if (manifest && !add_chunk_to_manifest(manifest, chunk)) {
+      ok = false;
+      chunk_destroy(chunk);
+      break;
+    }
+    if (plans) {
+      for (int i = 0; i < chunk->element_count; i++) {
+        File* f = chunk->items[i];
+        if (!f)
+          continue;
+        const char* path = file_wire_path(f);
+        if (!delete_plan_sender_add(plans, path, f->is_dir)) {
+          ok = false;
+          break;
+        }
+      }
+      if (!ok) {
+        chunk_destroy(chunk);
+        break;
+      }
+    }
+    if (chunks_out) {
+      /* Retain the chunk for the caller's data pass; ownership moves with it. */
+      if (!array_list_add(chunks_out, chunk)) {
+        ok = false;
+        chunk_destroy(chunk);
+        break;
+      }
+    } else {
+      chunk_destroy(chunk);
+    }
+  }
+  if (ok) {
+    /* Keep every traversed source directory, including empty ones, so a plan
+       no longer removes the destination directory itself.  Their own plans are
+       emitted after the data stream (no file frame triggers them). */
+    if (plans && options->plan_dirs) {
+      for (int i = 0; i < options->plan_dirs->size; i++) {
+        if (!delete_plan_sender_add(plans, (const char*)options->plan_dirs->items[i], true)) {
+          ok = false;
+          break;
+        }
+      }
+    }
+  }
+  if (ok && directory_scanner_failed(scanner))
+    ok = false;
+  if (io_error_out)
+    *io_error_out = directory_scanner_had_io_error(scanner);
+  directory_scanner_destroy(scanner);
+  return ok;
+}

src/client/client_send.h

@@ -22,7 +22,7 @@ void client_set_abort_armed(bool armed);
  * never free it, and the caller retains ownership (freeing it with
  * config_delete() once the call returns). */
 int send_files(Config* config);
-int send_files_multithreaded(Config** config);
+int send_files_multithreaded(Config* config);
 /* rsync's --ignore-errors deletion gate: with no I/O error during the scan the
  * deletion phase always proceeds; with one it is suppressed unless
  * `--ignore-errors` was given.  Exposed so the decision can be unit-tested

src/client/client_send_internal.h

@@ -0,0 +1,126 @@
+#ifndef CLIENT_SEND_INTERNAL_H
+#define CLIENT_SEND_INTERNAL_H
+
+/* Declarations shared between the client_send.c transfer orchestration and the
+ * reporting (client_report.c), scanner-preparation (client_scan.c) and
+ * manifest/list/dry-run (client_manifest.c) translation units that were split
+ * out of it.  Nothing here is part of the public client_send.h facade. */
+
+#include "array_list.h"
+#include "client_send.h"
+#include "config.h"
+#include "delete_plan.h"
+#include "delta.h"
+#include "format.h"
+#include "log.h"
+#include "protocol.h"
+#include "scanner.h"
+#include <stdatomic.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <time.h>
+
+/* One mebibyte in bytes; the unit used by the --stats/--progress lines.
+   Always cast to double when dividing so the output stays fractional. */
+#define BYTES_PER_MIB (1024ULL * 1024ULL)
+
+/* Compiled scanner inputs that are shared read-only across scanner instances
+ * and, in -m mode, across worker threads. `base_filters` owns the compiled
+ * command-line + -C rules; the FileListSet allow-set lives in the Config.
+ * `hardlinks` owns the --hard-links/-H link-group detection table (NULL when
+ * off) and is shared (mutex-guarded) across every scanner/worker of one scan. */
+typedef struct {
+  ScannerOptions options;
+  FilterRuleList* base_filters; /* owned; may be NULL */
+  HardLinkTable* hardlinks;     /* owned; may be NULL */
+  char* relative_prefix;        /* owned -R prefix; may be NULL */
+} PreparedScanner;
+
+/* client_scan.c */
+bool prepare_scanner(const Config* config, int num_threads, PreparedScanner* out);
+void prepared_scanner_destroy(PreparedScanner* prepared);
+bool append_implied_dir_times(const Config* config, ArrayList* dir_entries);
+char* delete_scope_root_marker(const Config* config);
+const char* delete_plan_walk_root(const Config* config, const ArrayList* synced_dirs);
+bool files_from_list_check(const Config* config, ArrayList* missing_dest, int* skipped_out);
+bool scan_paths_only(const Config* config, const ScannerOptions* options, ArrayList* manifest,
+                     DeletePlanSender* plans, bool* io_error_out,
+                     unsigned long long* non_dir_count_out, ArrayList* chunks_out,
+                     bool emit_nonreg);
+
+/* client_report.c */
+void log_server_rejection(const char* context);
+const char* display_bytes(unsigned long long bytes, bool human_readable, char* buffer,
+                          size_t buffer_size);
+unsigned long long dir_count_for_stats(const Config* config, const ArrayList* dir_entries,
+                                       atomic_ullong* counter);
+void report_transfer_stats(const Config* config, const TransferStats* stats, time_t start,
+                           const ReceiverStats* recv);
+void transfer_stats_note_entry(TransferStats* stats, const File* file);
+void transfer_stats_note_transferred(TransferStats* stats, const File* file);
+bool info_flag_enabled(const Config* config, LogInfoFlag flag);
+void print_delete_reports(const Config* config, const ArrayList* paths);
+const char* delete_display_path(const Config* config, const char* path);
+bool progress_requested(const Config* config);
+void client_progress_cleanup(void);
+void client_progress_begin(const Config* config);
+void client_progress_file(const Config* config, const File* file);
+void client_progress_name(const Config* config, const File* file);
+/* Emit a transferred entry's ancestor directories (as -i/--out-format change
+ * lines or --progress name lines) before the entry's own line. */
+void client_change_emit_ancestors(const Config* config, const File* file);
+/* Output parity (protocol 2.30.0): probe each not-yet-known ancestor directory's
+ * pre-transfer destination state before the entry that first triggers it is
+ * sent.  Returns false on a protocol/transport error. */
+bool client_change_probe_ancestors(const Config* config, const File* file, int fd);
+/* Mark a transferred directory entry as already reported, and flush the
+ * itemize lines for changed directories that had no transferred child. */
+void client_change_mark_dir(const Config* config, const File* file);
+void client_change_emit_pending_dirs(const Config* config, int fd);
+void client_progress_uptodate(const Config* config, const File* file);
+void client_progress_prepare(const Config* config, const ArrayList* plan_dirs,
+                             unsigned long long plan_non_dir_count);
+bool receive_stats_record(int fd, ReceiverStats* stats, ArrayList* would_delete);
+/* --stderr=client diagnostic channel (client_report.c): install the queueing
+ * log sink for a transfer, mark the session live, flush queued diagnostics over
+ * the wire at a frame boundary, and tear the sink down. */
+void client_messages_install(void);
+void client_messages_activate(bool active);
+void client_flush_client_messages(int fd);
+void client_messages_end(void);
+
+/* client_send.c */
+void receive_daemon_motd(Client* client, const Config* config);
+Client* connect_transfer_client(const Config* config);
+/* Connect the configured transport and install `session` on it: init with the
+ * socket fd pair, apply the I/O timeout and (when negotiated) the TLS object,
+ * then bind the session to this thread.  Returns the connected client, or NULL
+ * after logging the connect failure.  The caller owns the client and must keep
+ * `session` alive until it calls protocol_session_unbind(). */
+Client* client_connect_and_bind_session(const Config* config, ProtocolSession* session);
+/* Shared --files-from/--delete-missing-args preamble for the send entry points:
+ * when --delete-missing-args is set, allocate the list that
+ * files_from_list_check fills with the destination mirrors of missing entries;
+ * then validate the --files-from list.  On success returns true and stores the
+ * (possibly NULL) owned list in *missing_args_out plus the skipped count; on
+ * failure returns false after freeing the list. */
+bool client_prepare_files_from(const Config* config, ArrayList** missing_args_out,
+                               int* skipped_out);
+void disconnect_transfer_client(Client* client);
+int incremental_check(Client* client, File* file, const Config* config, DeltaSignature** out_sig,
+                      unsigned long long* resume_offset);
+
+/* client_manifest.c */
+bool dry_run_targets_server(const Config* config);
+bool add_chunk_to_manifest(ArrayList* manifest, const Chunk* chunk);
+int send_dry_run_manifest(const Config* config);
+int send_list_only(const Config* config);
+int send_dry_run_remote(Config* config);
+int send_delete_manifest(int fd, ArrayList* manifest, ArrayList* protected_prefixes,
+                         ArrayList* size_skipped, ArrayList* missing_args, ArrayList* synced_dirs,
+                         const FilterRuleList* per_dir_rules);
+bool send_delete_manifest_early(Client* client, ArrayList* manifest, ArrayList* protected_prefixes,
+                                ArrayList* size_skipped, ArrayList* missing_args,
+                                ArrayList* synced_dirs, const FilterRuleList* per_dir_rules);
+
+#endif

src/client/client_validation.c

@@ -53,7 +53,7 @@ bool validate_config(const Config* config) {
     return false;
   }
   if (config->compression_threads > 0 && !config->use_compression) {
-    log_message(LOG_LEVEL_ERROR, "--compress-threads requires compression (-c or -z)");
+    log_message(LOG_LEVEL_ERROR, "--compress-threads requires compression (-z/--compress)");
     return false;
   }
   if (config->transport == TRANSPORT_SSH && config->use_sendfile) {
@@ -75,6 +75,13 @@ bool validate_config(const Config* config) {
     log_message(LOG_LEVEL_ERROR, "-4/--ipv4 and -6/--ipv6 are mutually exclusive");
     return false;
   }
+  /* rsync 3.4.1 rejects --inplace together with --partial-dir (exit 1): the
+     inplace write path bypasses partial staging, so a partial-dir name would be
+     silently ignored.  Match rsync's message and refuse before any I/O. */
+  if (config->inplace && config->partial_dir) {
+    log_message(LOG_LEVEL_ERROR, "--inplace cannot be used with --partial-dir");
+    return false;
+  }
   if (config->log_file_format && !config->log_file) {
     log_message(LOG_LEVEL_ERROR, "--log-file-format requires --log-file");
     return false;
@@ -102,6 +109,16 @@ bool validate_config(const Config* config) {
     log_message(LOG_LEVEL_ERROR, "%s", invariants_error);
     return false;
   }
+  /* The receiver rejects a protect-rule block with more than MAX_FILTER_RULES
+     entries as an opaque protocol error; reject an over-limit --filter set here,
+     before any network I/O, with an actionable message.  send_protect_entries()
+     re-checks the final built count because cvs-exclude / merge rules can
+     expand it beyond config->filters->size. */
+  if (config->filters && config->filters->size > MAX_FILTER_RULES) {
+    log_message(LOG_LEVEL_ERROR, "too many filter rules: %d (maximum %d)", config->filters->size,
+                MAX_FILTER_RULES);
+    return false;
+  }
   /* --protocol: FastSync has exactly one wire format, so the forced version
      must equal the current PROTOCOL_VERSION exactly.  Rejected here, before any
      network I/O, rather than letting the server hit its own mismatch check. */

src/client/scanner.h

@@ -10,6 +10,7 @@
 #include "stop_condition.h"
 #include <dirent.h>
 #include <stdbool.h>
+#include <stddef.h>
 #include <stdatomic.h>
 #include <sys/types.h>
 #include <threads.h>
@@ -18,6 +19,11 @@
  * keeps one transfer from spawning an unbounded pool on a very large machine. */
 #define MAX_SCANNER_THREADS 256
 
+/* Depth of the scanner's work queues: the sequential scanner's pending-directory
+ * stack and the parallel scanner's result queue.  Bounds memory for a very wide
+ * or very deep tree while leaving ample headroom for normal scans. */
+#define SCANNER_RESULT_QUEUE_CAP 100
+
 typedef struct {
   bool use_metadata;
   /* Phase 4 metadata capture: -U/--atimes and -N/--crtimes tell the scanner to
@@ -50,7 +56,7 @@ typedef struct {
   bool copy_dirlinks;
   bool munge_links;
   bool checksum;
-  bool one_file_system;
+  int one_file_system;
   /* Phase 4 special/devices: whether device nodes (--devices) and special files
    * (--specials) are preserved via recreation, and whether --copy-devices
    * copies a device's content as an ordinary regular file. */
@@ -114,6 +120,13 @@ typedef struct {
    * directories, exactly like rsync; the receive root is the "." sentinel.
    * Guarded by `excluded_mutex`. */
   ArrayList* synced_dirs;
+  /* Per-directory filter-rule sink (optional): when non-NULL the scanner appends
+   * a deep copy of every rule it reads from a per-directory merge file, each
+   * carrying its owner directory and no-inherit flag (see filter.h).  The delete
+   * carriers transmit them so the receiver re-derives the per-directory
+   * protect/risk set for destination-only entries.  Guarded by `excluded_mutex`
+   * like the other sinks. */
+  FilterRuleList* per_dir_rules;
   /* Delete-plan directory sink (optional): when non-NULL the scanner appends
    * the destination-relative path of every directory it traverses (except the
    * receive root).  The per-directory --delete-during/--delete-delay plan
@@ -129,6 +142,17 @@ typedef struct {
   /* --info=nonreg: print rsync's `skipping non-regular file "NAME"` line for a
    * non-regular entry that is not being preserved.  Client-only. */
   bool note_nonreg;
+  /* --info=mount: print rsync's `[sender] skipping mount-point dir NAME` when
+   * -xx drops a mount-point directory.  Client-only. */
+  bool note_mount;
+  /* --stats directory accounting for a `-r` run (no -t/-p): a shared counter of
+   * traversed directories that are NOT otherwise represented by an inline
+   * directory entry (rsync still counts every directory in `Number of files`).
+   * Incremented when a directory is opened and decremented when an empty
+   * directory is emitted inline (so it is counted exactly once).  Atomic
+   * because the parallel scanner's workers share it; NULL disables the
+   * accounting.  Client-only. */
+  atomic_ullong* dir_count;
   /* Source root and 8-bit-output policy used to render a `--info=nonreg` name
    * relative to the transfer root.  Borrowed read-only. */
   const char* send_directory;
@@ -188,6 +212,17 @@ typedef struct {
   int current_depth;
   dev_t root_dev;
   bool failed;
+  /* rsync-order traversal: each opened directory's entries are inspected once
+     and buffered (an internal SortedEntry[] owned here) sorted as rsync's flist
+     orders them -- non-directories ascending, then directories ascending.  The
+     entries are walked in order and child directories are collected in
+     `pending_dirs` (an ArrayList of DirEntry*, owned here) and pushed onto the
+     LIFO `directories` stack in reverse at directory exhaustion, so the emitted
+     stream is depth-first like rsync.  `sorted_*` are reset per directory. */
+  void* sorted_entries;
+  size_t sorted_count;
+  size_t sorted_index;
+  void* pending_dirs;
   /* Recursive scan: whether the open directory yielded any transferred or
      descended entry.  When it did not, closing it emits a directory entry so
      the empty source directory is recreated at the destination (rsync
@@ -254,7 +289,7 @@ void directory_scanner_destroy(DirectoryScanner* scanner);
 /* --one-file-system (-x) decision: a directory entry may be descended into
  * only when the option is disabled or the entry lives on the same device as
  * the transfer root. Exposed so tests can exercise the rule directly. */
-bool scanner_same_filesystem(bool one_file_system, dev_t root_device, dev_t entry_device);
+bool scanner_same_filesystem(int one_file_system, dev_t root_device, dev_t entry_device);
 
 /* Relative path of an on-disk path below `root` ("" == the root itself, NULL
  * when `fs_path` is not under `root`). Handles trailing slashes and a root of

src/client/scanner_filter.c

@@ -0,0 +1,793 @@
+#include "log.h"
+#include "scanner.h"
+#include "scanner_internal.h"
+#include "array_list.h"
+#include "chunk.h"
+#include "file.h"
+#include "queue.h"
+#include "utils.h"
+#include <dirent.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/sysmacros.h>
+#include <threads.h>
+#include <unistd.h>
+#include <limits.h>
+
+#include "xattr.h"
+
+/* A chain node: `own` holds the .rsync-filter rules of one directory, `parent`
+ * the context that directory inherited (nearest ancestor with a filter file).
+ * The chain for a directory's contents runs from that directory's own node up
+ * to the root; the command-line base rules are evaluated after the whole
+ * chain. */
+struct FilterNode {
+  FilterNode* parent;
+  FilterRuleList* own;
+};
+
+void filter_node_destroy(void* item) {
+  if (item) {
+    FilterNode* node = (FilterNode*)item;
+    if (node->own)
+      filter_rule_list_free(node->own);
+    free(node);
+  }
+}
+
+FilterNode* filter_node_alloc(FilterNode* parent, FilterRuleList* own) {
+  FilterNode* node = malloc(sizeof(FilterNode));
+  if (!node)
+    return NULL;
+  node->parent = parent;
+  node->own = own;
+  return node;
+}
+
+/* Evaluate a rule chain for one entry.  rsync precedence, highest first: the
+ * innermost (current) directory's .rsync-filter rules, then each ancestor's,
+ * then the root's, and finally the command-line base rules (--filter/-C).  The
+ * sender-side verdict decides whether the entry is hidden from the transfer;
+ * the receiver-side verdict decides whether its destination mirror is protected
+ * from --delete.  Each side takes the FIRST matching rule independently. */
+typedef struct {
+  bool hide;    /* sender-side exclude matched */
+  bool protect; /* receiver-side exclude matched */
+} FilterOutcome;
+
+static void chain_rules_outcome(const FilterRuleList* base, const FilterNode* node, const char* rel,
+                                const char* leaf, bool is_dir, FilterOutcome* out) {
+  memset(out, 0, sizeof(*out));
+  bool sender_decided = false;
+  bool receiver_decided = false;
+  const FilterNode* n = node;
+  while (!sender_decided || !receiver_decided) {
+    const FilterRuleList* list = n ? n->own : base;
+    if (list) {
+      if (!sender_decided) {
+        FilterAction action = filter_rules_apply_side(list, rel, leaf, is_dir, FILTER_SIDE_SENDER);
+        if (action != FILTER_ACTION_NONE) {
+          out->hide = action == FILTER_ACTION_EXCLUDE;
+          sender_decided = true;
+        }
+      }
+      if (!receiver_decided) {
+        FilterAction action =
+            filter_rules_apply_side(list, rel, leaf, is_dir, FILTER_SIDE_RECEIVER);
+        if (action != FILTER_ACTION_NONE) {
+          out->protect = action == FILTER_ACTION_PROTECT;
+          receiver_decided = true;
+        }
+      }
+    }
+    if (!n)
+      break;
+    n = n->parent;
+  }
+}
+
+static bool entry_allowed(const FilterRuleList* base, const FilterNode* node, const char* rel,
+                          const char* leaf, bool is_dir, bool exclude_filter_files,
+                          bool* protect_out) {
+  /* -FF: per-directory .rsync-filter files are never transferred (single -F
+     transfers them, matching rsync). */
+  if (exclude_filter_files && !is_dir && strcmp(leaf, ".rsync-filter") == 0) {
+    if (protect_out)
+      *protect_out = false;
+    return false;
+  }
+  FilterOutcome outcome;
+  chain_rules_outcome(base, node, rel, leaf, is_dir, &outcome);
+  if (protect_out)
+    *protect_out = outcome.protect;
+  return !outcome.hide;
+}
+
+void dir_entry_destroy(void* item) {
+  if (item) {
+    DirEntry* de = (DirEntry*)item;
+    free(de->path);
+    free(de);
+  }
+}
+
+DirEntry* dir_entry_create(const char* path, int depth, FilterNode* context) {
+  DirEntry* de = malloc(sizeof(DirEntry));
+  if (!de)
+    return NULL;
+  de->path = str_dup(path);
+  if (!de->path) {
+    free(de);
+    return NULL;
+  }
+  de->depth = depth;
+  de->context = context;
+  return de;
+}
+
+/* Apply rsync's symlink-resolution precedence to one S_ISLNK entry:
+ *   --copy-links  dereferences every symlink;
+ *   --copy-unsafe-links  dereferences only targets unsafe_symlink() flags;
+ *   -k/--copy-dirlinks  dereferences only a symlink whose referent is a dir;
+ *   --safe-links  (receiver-side in rsync; modelled here) ignores an unsafe
+ *                 target that would otherwise be carried; with --munge-links
+ *                 every stored target becomes absolute, so --safe-links then
+ *                 ignores every symlink, exactly as rsync documents;
+ *   -l/--links  carries the link.
+ * `link_rel` is the symlink's transfer-relative path (incl. name) and is used
+ * only for the lexical unsafe test.  `target` receives the raw link value. */
+LinkAction scanner_link_action(const ScannerOptions* options, const char* path,
+                               const char* link_rel, char* target, size_t target_size) {
+  if (!options->follow_symlinks && !options->copy_links && !options->safe_links &&
+      !options->copy_unsafe_links && !options->copy_dirlinks)
+    return LINK_ACTION_SKIP;
+  ssize_t length = readlink(path, target, target_size - 1);
+  if (length < 0)
+    return LINK_ACTION_SKIP;
+  target[length] = '\0';
+
+  bool unsafe = file_symlink_unsafe(target, link_rel);
+  if (options->copy_links || (options->copy_unsafe_links && unsafe))
+    return LINK_ACTION_DEREF;
+  if (options->copy_dirlinks) {
+    struct stat ref;
+    if (stat(path, &ref) == 0 && S_ISDIR(ref.st_mode))
+      return LINK_ACTION_DEREF;
+  }
+  if (options->safe_links && (unsafe || options->munge_links))
+    return LINK_ACTION_SKIP_PROTECTED;
+  if (!options->follow_symlinks || target[0] == '\0')
+    return LINK_ACTION_SKIP;
+  return LINK_ACTION_CARRY;
+}
+
+/* --one-file-system (-x) decision. Only directories can carry a different
+ * device than their parent (mount points), so this is checked when a child
+ * directory is about to be descended into. */
+bool scanner_same_filesystem(int one_file_system, dev_t root_device, dev_t entry_device) {
+  return one_file_system <= 0 || entry_device == root_device;
+}
+
+/* Build a payload-less directory File carrying the captured metadata (when
+ * requested).  Used by -x mount-point emission and --list-only directory
+ * entries.  Returns NULL on allocation failure. */
+File* scanner_build_dir_file(const char* path, const struct stat* stats,
+                             const ScannerOptions* options) {
+  File* dir = file_create(path);
+  if (dir == NULL)
+    return NULL;
+  dir->is_dir = true;
+  if (options->use_metadata) {
+    dir->metadata =
+        file_metadata_create(dir->path, stats, options->preserve_atimes, options->preserve_crtimes);
+    if (!dir->metadata) {
+      file_destroy(dir);
+      return NULL;
+    }
+  }
+  return dir;
+}
+
+/* Relative path of an on-disk path below `root`. The transfer root may be
+ * given with a trailing slash; the returned rel path never has one and is ""
+ * for the root itself. A root of "/" is handled (its children start at "/").
+ * Exposed so tests can exercise the mapping directly. */
+char* scanner_path_relative(const char* root, const char* fs_path) {
+  size_t root_len = strlen(root);
+  while (root_len > 1 && root[root_len - 1] == '/')
+    root_len--;
+  if (strncmp(root, fs_path, root_len) != 0)
+    return NULL;
+  if (root_len == 1 && root[0] == '/') {
+    if (fs_path[1] == '\0')
+      return str_dup("");
+    return str_dup(fs_path + 1);
+  }
+  if (fs_path[root_len] == '\0')
+    return str_dup("");
+  if (fs_path[root_len] != '/')
+    return NULL;
+  return str_dup(fs_path + root_len + 1);
+}
+
+/* -R/--relative destination-relative prefix reconstructed from a source spec:
+ * everything after the first '.' path component (rsync's '/./' cut point),
+ * with leading/trailing slashes removed; or the whole spec (normalized) when
+ * there is no cut.  Returns "" for the receive root.  Exposed for tests. */
+char* scanner_relative_prefix(const char* spec) {
+  if (!spec || spec[0] == '\0')
+    return NULL;
+  const char* after = spec;
+  if (spec[0] == '.' && spec[1] == '/') {
+    after = spec + 2;
+  } else {
+    const char* cut = strstr(spec, "/./");
+    if (cut)
+      after = cut + 3;
+  }
+  size_t cap = strlen(spec) + 1;
+  char* out = malloc(cap);
+  if (!out)
+    return NULL;
+  size_t len = 0;
+  for (const char* s = after; *s;) {
+    while (*s == '/')
+      s++;
+    const char* comp = s;
+    while (*s && *s != '/')
+      s++;
+    size_t clen = (size_t)(s - comp);
+    if (clen == 0 || (clen == 1 && comp[0] == '.'))
+      continue;
+    if (len)
+      out[len++] = '/';
+    memcpy(out + len, comp, clen);
+    len += clen;
+  }
+  out[len] = '\0';
+  return out;
+}
+
+/* Relative path of a child entry below the current directory. */
+char* child_rel_path(const char* parent_rel, const char* name) {
+  if (!parent_rel || parent_rel[0] == '\0')
+    return str_dup(name);
+  return path_cat(parent_rel, name);
+}
+
+/* Destination-relative wire path for an entry under an -R prefix. */
+char* scanner_prefix_send_path(const char* prefix, const char* rel) {
+  if (prefix[0] == '\0')
+    return str_dup(rel);
+  if (rel[0] == '\0')
+    return str_dup(prefix);
+  return path_cat(prefix, rel);
+}
+
+/* Apply the --files-from allow-set and the filter layer to one entry.  On
+ * return `*protect_out` is true when a receiver-side rule protects the entry's
+ * destination mirror from deletion. */
+bool entry_passes_selection(const FileListSet* file_list, const FilterRuleList* base,
+                            const FilterNode* node, const char* rel, const char* leaf, bool is_dir,
+                            bool per_dir_filters, bool exclude_filter_files, bool* protect_out) {
+  if (protect_out)
+    *protect_out = false;
+  if (file_list && !file_list_affects(file_list, rel))
+    return false;
+  if (base || per_dir_filters)
+    return entry_allowed(base, node, rel, leaf, is_dir, exclude_filter_files, protect_out);
+  return true;
+}
+
+/* Best-effort capture of the file's whitelisted xattrs (-X/-A).  A failure to
+ * read xattrs is non-fatal: the file is transferred without them.  A symlink
+ * entry reads the LINK's own xattrs (never the referent's) with the no-follow
+ * variant; on Linux the VFS refuses xattrs on symlinks, so that yields NULL. */
+void scanner_capture_xattrs_opts(const ScannerOptions* options, File* file) {
+  if (!options || !file || !(options->preserve_xattrs || options->preserve_acls))
+    return;
+  file->xattrs = file->is_symlink ? xattr_capture_path_nofollow(file->path, options->preserve_acls)
+                                  : xattr_capture_path(file->path, options->preserve_acls);
+}
+
+void scanner_capture_xattrs(const DirectoryScanner* scanner, File* file) {
+  if (!scanner)
+    return;
+  scanner_capture_xattrs_opts(&scanner->options, file);
+}
+
+/* Apply --hard-links (-H) detection to one regular File.  On a sibling (a
+ * later member of an already-seen source inode) the File keeps the group id
+ * and the first member's wire path but carries NO data payload (size 0); the
+ * first member is left untouched (data present, link_first).  Returns false on
+ * allocation failure (the caller marks the scan failed); the File stays usable
+ * either way. */
+bool scanner_assign_hardlink(HardLinkTable* table, File* file, const struct stat* stats) {
+  if (!table || !file || !stats)
+    return true;
+  int gid;
+  bool is_first;
+  char* first_path = NULL;
+  if (!hardlink_table_assign(table, file_wire_path(file), stats->st_dev, stats->st_ino, &gid,
+                             &is_first, &first_path))
+    return false;
+  file->link_group = gid;
+  file->link_first = is_first;
+  if (!is_first) {
+    file->hardlink_target = first_path;
+    file->data->size = 0;
+  } else {
+    free(first_path);
+  }
+  return true;
+}
+
+/* Phase 4 special/devices decision for one non-regular entry, matching rsync:
+   - a char/block device is RECREATED as a node under -D/--devices, unless
+     --copy-devices asks for its content to be copied into a regular file;
+   - a FIFO/socket is RECREATED under --specials;
+   - when the matching flag is absent the entry is SKIPPED ("skipping
+     non-regular file"), exactly like rsync's default, instead of being
+     silently copied as a zero-length regular file;
+   - anything else (regular/directory) is left to the normal data path. */
+ScannerSpecial scanner_prepare_special(bool preserve_devices, bool preserve_specials,
+                                       bool copy_devices, File* file, const struct stat* stats) {
+  if (!file || !stats)
+    return SCANNER_SPECIAL_REGULAR;
+  bool is_device = S_ISCHR(stats->st_mode) || S_ISBLK(stats->st_mode);
+  bool is_fifo = S_ISFIFO(stats->st_mode);
+  bool is_socket = S_ISSOCK(stats->st_mode);
+  if (!is_device && !is_fifo && !is_socket)
+    return SCANNER_SPECIAL_REGULAR;
+  if (is_device && copy_devices)
+    return SCANNER_SPECIAL_REGULAR; /* copy device content as a regular file */
+  bool preserve = is_device ? preserve_devices : preserve_specials;
+  if (!preserve)
+    return SCANNER_SPECIAL_SKIP;
+  file->is_special = true;
+  file->data->size = 0;
+  file->data->data = NULL;
+  if (is_device) {
+    file->rdev_major = (int32_t)major(stats->st_rdev);
+    file->rdev_minor = (int32_t)minor(stats->st_rdev);
+  }
+  return SCANNER_SPECIAL_RECREATE;
+}
+
+/* Append `rel` to the caller's exclusion sink, taking `mtx` when shared across
+   parallel worker threads.  Returns false on allocation failure (list left
+   unchanged). */
+bool excluded_sink_append(ArrayList* list, mtx_t* mtx, const char* rel) {
+  if (!list)
+    return true;
+  char* dup = str_dup(rel);
+  if (!dup)
+    return false;
+  if (mtx)
+    mtx_lock(mtx);
+  bool ok = array_list_add(list, dup);
+  if (mtx)
+    mtx_unlock(mtx);
+  if (!ok)
+    free(dup);
+  return ok;
+}
+
+/* Record one pruned filesystem path in a delete-protection sink.  The stored
+   form is the entry's wire/destination-relative path (a single leading '/'
+   removed, exactly how manifest keep entries are stored), so the receiver's
+   walker prefixes match the destination layout.  An allocation failure is a
+   fatal scan error. */
+static void scanner_record_protected(DirectoryScanner* scanner, const char* fs_path,
+                                     ArrayList* sink) {
+  if (!sink || !fs_path)
+    return;
+  const char* rel = *fs_path == '/' ? fs_path + 1 : fs_path;
+  if (!excluded_sink_append(sink, scanner->options.excluded_mutex, rel))
+    scanner->failed = true;
+}
+
+/* rsync's `--info=nonreg` line for a non-regular entry that is not being
+ * preserved: `skipping non-regular file "NAME"`.  The name is the path relative
+ * to the transfer root, so it matches rsync's displayed name. */
+void scanner_note_nonreg(const ScannerOptions* options, const char* fs_path) {
+  if (!options || !options->note_nonreg || !fs_path)
+    return;
+  const char* rel = utils_strip_transfer_root(fs_path, options->send_directory);
+  char* escaped = output_escape(rel, options->eight_bit_output);
+  printf("skipping non-regular file \"%s\"\n", escaped ? escaped : rel);
+  free(escaped);
+  fflush(stdout);
+}
+
+/* Construct one non-directory File from an inspected entry.  Shared by the
+ * sequential and parallel scanners so entry construction has a single
+ * implementation: data size (or carried symlink), -R wire path, special/devices
+ * classification, hardlink group, metadata and xattr capture all happen here in
+ * the same order for both.  See the declaration for the ownership contract. */
+ScannerBuildStatus scanner_build_file_entry(const ScannerOptions* options, ScannerEntry* inspected,
+                                            const char* rel, File** out_file, bool* failed) {
+  *out_file = NULL;
+  if (failed)
+    *failed = false;
+  File* file = file_create(inspected->path);
+  if (!file) {
+    /* The File never existed, so drop the not-yet-transferred symlink target
+       here; the caller's entry teardown would otherwise double-free it. */
+    free(inspected->link_target);
+    inspected->link_target = NULL;
+    return SCANNER_BUILD_FAIL_CONTINUE;
+  }
+  if (inspected->is_symlink) {
+    file->is_symlink = true;
+    file->symlink_target = inspected->link_target;
+    inspected->link_target = NULL;
+  } else {
+    file->data->size = inspected->stats.st_size;
+  }
+  /* -R + --files-from uses the bare transfer-relative path; -R without
+     --files-from prefixes it.  Plain scans keep the source path. */
+  bool relative_mode = options->relative && options->file_list != NULL;
+  if (relative_mode) {
+    file->send_path = str_dup(rel);
+  } else if (options->relative_prefix) {
+    file->send_path = scanner_prefix_send_path(options->relative_prefix, rel);
+  }
+  if ((relative_mode || options->relative_prefix) && !file->send_path) {
+    file_destroy(file);
+    return SCANNER_BUILD_FAIL_BREAK;
+  }
+  /* --devices/--specials: a device/FIFO/socket entry marked for preservation
+     becomes a node to recreate (is_special, no data, rdev captured); an
+     unrequested non-regular entry is skipped (rsync default). */
+  ScannerSpecial special =
+      scanner_prepare_special(options->preserve_devices, options->preserve_specials,
+                              options->copy_devices, file, &inspected->stats);
+  if (special == SCANNER_SPECIAL_SKIP) {
+    scanner_note_nonreg(options, file->path);
+    file_destroy(file);
+    return SCANNER_BUILD_SKIP;
+  }
+  if (options->hardlinks && S_ISREG(inspected->stats.st_mode) &&
+      !scanner_assign_hardlink(options->hardlinks, file, &inspected->stats)) {
+    /* Allocation failure is non-fatal to this entry (it is still emitted) but
+       marks the scan failed, matching the historical inlined behaviour. */
+    if (failed)
+      *failed = true;
+  }
+  if (options->use_metadata) {
+    file->metadata = file_metadata_create(file->path, &inspected->stats, options->preserve_atimes,
+                                          options->preserve_crtimes);
+    if (!file->metadata) {
+      file_destroy(file);
+      return SCANNER_BUILD_FAIL_BREAK;
+    }
+  }
+  /* A hardlink sibling carries no data, so it carries no xattrs. */
+  if (!(file->link_group != 0 && !file->link_first))
+    scanner_capture_xattrs_opts(options, file);
+  *out_file = file;
+  return SCANNER_BUILD_OK;
+}
+
+/* rsync 3.4.1's `--info=mount` line, emitted when `-xx` drops a mount-point
+ * directory: `[sender] skipping mount-point dir NAME` (the client is the
+ * sender).  Plain `-x` keeps the empty directory and prints nothing, matching
+ * rsync. */
+void scanner_note_mount(const ScannerOptions* options, const char* fs_path) {
+  if (!options || !options->note_mount || !fs_path)
+    return;
+  const char* rel = utils_strip_transfer_root(fs_path, options->send_directory);
+  char* escaped = output_escape(rel, options->eight_bit_output);
+  printf("[sender] skipping mount-point dir %s\n", escaped ? escaped : rel);
+  free(escaped);
+  fflush(stdout);
+}
+
+/* --debug=filter: a selection/filter decision dropped an entry. */
+void scanner_note_filter(const ScannerOptions* options, const char* name) {
+  if (!options || !log_debug_enabled(LOG_DEBUG_FILTER) || !name)
+    return;
+  log_debug_message(LOG_DEBUG_FILTER, "filter: excluded %s", name);
+}
+
+/* Account for a directory that will not be represented by an inline directory
+ * entry.  Paired with scanner_dir_count_uncount for empty directories that are
+ * emitted inline, so every traversed directory is counted exactly once. */
+void scanner_dir_count_count(const ScannerOptions* options) {
+  if (options && options->dir_count)
+    atomic_fetch_add(options->dir_count, 1);
+}
+
+void scanner_dir_count_uncount(const ScannerOptions* options) {
+  if (options && options->dir_count)
+    atomic_fetch_sub(options->dir_count, 1);
+}
+
+/* A user-selection exclusion (--filter/-C/per-dir or --exclude/--include). */
+void scanner_record_excluded(DirectoryScanner* scanner, const char* fs_path) {
+  scanner_record_protected(scanner, fs_path, scanner->options.excluded_paths);
+}
+
+/* A --max-size/--min-size prune (always protected, even under --delete-excluded). */
+void scanner_record_size_skipped(DirectoryScanner* scanner, const char* fs_path) {
+  scanner_record_protected(scanner, fs_path, scanner->options.size_skipped_paths);
+}
+
+/* The destination-relative coordinate the receiver's delete walkers match
+   against for an entry at `fs_path` (with `rel` its path relative to the
+   transfer root, "" for the root): `relative_prefix + rel` under -R+--relative,
+   the bare relative path under -R+--files-from, else the source path with a
+   leading '/' removed, with "." for the receive root.  Shared by the
+   synchronized-directory sink and the mirrored per-directory rule owners so
+   both live in the same coordinate system.  Returns an owned string, or NULL on
+   allocation failure. */
+char* scanner_dest_rel_path(const ScannerOptions* options, const char* fs_path, const char* rel,
+                            bool relative_mode) {
+  char* prefixed = NULL;
+  const char* dest;
+  if (relative_mode) {
+    dest = rel;
+  } else if (options->relative_prefix) {
+    prefixed = scanner_prefix_send_path(options->relative_prefix, rel);
+    if (!prefixed)
+      return NULL;
+    dest = prefixed;
+  } else {
+    dest = fs_path;
+  }
+  if (dest[0] == '/')
+    dest++;
+  if (dest[0] == '\0')
+    dest = ".";
+  char* out = str_dup(dest);
+  free(prefixed);
+  return out;
+}
+
+/* Record a directory the scan synchronized.  `fs_path` is its absolute path and
+   `rel` its path relative to the transfer root ("" for the root); the stored
+   form matches the wire layout (see scanner_dest_rel_path).  Returns false on
+   allocation failure. */
+bool scanner_record_synced_dir(const ScannerOptions* options, const char* fs_path, const char* rel,
+                               bool relative_mode) {
+  if (!options->synced_dirs && !options->plan_dirs)
+    return true;
+  if (!file_list_dir_in_scope(options->file_list, rel))
+    return true;
+  char* dest = scanner_dest_rel_path(options, fs_path, rel, relative_mode);
+  if (!dest)
+    return false;
+  bool ok = true;
+  if (options->synced_dirs)
+    ok = excluded_sink_append(options->synced_dirs, options->excluded_mutex, dest);
+  /* The delete-plan keep set needs an entry for every traversed source
+     directory, including empty ones, so its destination mirror is kept rather
+     than deleted as an extra; the receive root (".") is implicit. */
+  if (ok && options->plan_dirs && strcmp(dest, ".") != 0)
+    ok = excluded_sink_append(options->plan_dirs, options->excluded_mutex, dest);
+  free(dest);
+  return ok;
+}
+
+/* Read every per-directory filter file that applies to `dir_path` (its
+ * .rsync-filter when -F is active, plus each registered "dir-merge NAME") into a
+ * fresh list.  Returns NULL on allocation/parse failure (message in `err`);
+ * returns an empty list (and *any_exists=false) when no file exists. */
+FilterRuleList* read_dir_filters(const ScannerOptions* options, const char* dir_path,
+                                 const char* rel, bool relative_mode, bool* any_exists, char* err,
+                                 size_t err_size) {
+  if (err && err_size > 0)
+    err[0] = '\0';
+  const FilterRuleList* base = options->base_filters;
+  bool have_names = options->per_dir_filters || (base && base->dir_merge_count > 0);
+  if (any_exists)
+    *any_exists = false;
+  if (!have_names)
+    return NULL;
+  FilterRuleList* own = filter_rule_list_create();
+  if (!own) {
+    snprintf(err, err_size, "memory allocation failed");
+    return NULL;
+  }
+  FilterParseOptions opts = {.delete_excluded = options->delete_excluded, .cvs_exclude = false};
+  bool exists = false;
+  if (options->per_dir_filters) {
+    if (!filter_file_append(own, dir_path, ".rsync-filter", rel, &opts, &exists, err, err_size))
+      goto fail;
+    if (exists && any_exists)
+      *any_exists = true;
+  }
+  if (base) {
+    for (int i = 0; i < base->dir_merge_count; i++) {
+      if (!filter_dir_merge_append(own, dir_path, &base->dir_merges[i], rel, &opts, &exists, err,
+                                   err_size))
+        goto fail;
+      if (exists && any_exists)
+        *any_exists = true;
+    }
+  }
+  /* Mirror the directory's rules into the delete-carrier sink so the receiver
+   * can reconstruct its per-directory protect/risk set.  The mirrored rules
+   * carry the destination-relative owner coordinate (not the transfer-root-
+   * relative one the sender's own evaluation uses) so the receiver's delete
+   * walkers, which match against receive-root-relative paths, find them. */
+  if (options->per_dir_rules && own->count > 0) {
+    char* owner = scanner_dest_rel_path(options, dir_path, rel, relative_mode);
+    if (!owner)
+      goto fail;
+    mtx_t* mtx = options->excluded_mutex;
+    if (mtx)
+      mtx_lock(mtx);
+    for (int i = 0; i < own->count; i++) {
+      FilterRule* copy = filter_rule_clone(own->items[i]);
+      if (!copy || !filter_rule_set_owner(copy, owner) ||
+          !filter_rule_list_add(options->per_dir_rules, copy)) {
+        filter_rule_free(copy);
+        if (mtx)
+          mtx_unlock(mtx);
+        free(owner);
+        goto fail;
+      }
+    }
+    if (mtx)
+      mtx_unlock(mtx);
+    free(owner);
+  }
+  return own;
+fail:
+  filter_rule_list_free(own);
+  return NULL;
+}
+
+/* Merge the open directory's own per-directory filter files (the default
+ * .rsync-filter when -F is active, plus every "dir-merge NAME" registered on the
+ * base rule list) into the inherited context, returning the context used for
+ * this directory's entries. On a parse error the scanner is marked failed.
+ * Returns 0 on success, -1 on failure. */
+int open_directory_filter_context(DirectoryScanner* scanner, const FilterNode* inherited) {
+  char err[256];
+  bool any_exists = false;
+  FilterRuleList* own = read_dir_filters(&scanner->options, scanner->current_path,
+                                         scanner->current_rel ? scanner->current_rel : "",
+                                         scanner->relative_mode, &any_exists, err, sizeof(err));
+  if (!own) {
+    /* read_dir_filters() leaves `err` set on a parse/allocation failure even
+       when an earlier merge file in the same directory existed (any_exists true);
+       key off the error text rather than any_exists so an invalid per-directory
+       filter file can never be silently ignored. */
+    if (err[0] == '\0') {
+      scanner->current_node = (FilterNode*)inherited;
+      return 0;
+    }
+    char* escaped_path = output_escape(scanner->current_path, log_get_8_bit_output());
+    log_message(LOG_LEVEL_ERROR, "invalid per-directory filter in %s: %s",
+                escaped_path ? escaped_path : "<allocation failed>", err);
+    free(escaped_path);
+    scanner->failed = true;
+    return -1;
+  }
+  if (any_exists && (own->count > 0 || own->dir_merge_count > 0)) {
+    FilterNode* node = filter_node_alloc((FilterNode*)inherited, own);
+    if (!node || !array_list_add(scanner->filter_nodes, node)) {
+      filter_node_destroy(node);
+      scanner->failed = true;
+      return -1;
+    }
+    scanner->current_node = node;
+  } else {
+    filter_rule_list_free(own);
+    scanner->current_node = (FilterNode*)inherited;
+  }
+  return 0;
+}
+
+/* Inspect symlinks, resolve the entry type, and apply file filters once for both scanners.
+ * `link_rel` is the entry's path relative to the transfer root (including its
+ * name), used for the lexical rsync unsafe-symlink test. */
+int scanner_inspect_entry(const ScannerOptions* options, const char* containing_dir,
+                          const char* link_rel, const char* name, ScannerEntry* entry) {
+  entry->excluded = false;
+  entry->size_excluded = false;
+  entry->referent_error = false;
+  entry->is_symlink = false;
+  entry->link_target = NULL;
+  entry->path = path_cat(containing_dir, name);
+  if (!entry->path)
+    return -1;
+
+  struct stat link_stats;
+  if (lstat(entry->path, &link_stats) != 0) {
+    free(entry->path);
+    return 0;
+  }
+  if (!S_ISLNK(link_stats.st_mode))
+    goto regular;
+
+  char link_target[4096];
+  switch (scanner_link_action(options, entry->path, link_rel, link_target, sizeof(link_target))) {
+  case LINK_ACTION_SKIP:
+    goto skip;
+  case LINK_ACTION_SKIP_PROTECTED:
+    /* --safe-links ignored the link, but rsync still counts it as present in
+       the transfer, so its destination mirror survives --delete.  Record it as
+       an excluded path (the same delete-protection channel as a filter prune). */
+    entry->excluded = true;
+    goto skip;
+  case LINK_ACTION_DEREF:
+    if (stat(entry->path, &entry->stats) != 0) {
+      /* rsync reports "symlink has no referent" and continues with a partial
+         transfer (exit 23); record the error so the run exits 23 too. */
+      char* escaped = output_escape(entry->path, log_get_8_bit_output());
+      log_message(LOG_LEVEL_WARNING, "symlink has no referent: %s",
+                  escaped ? escaped : "<allocation failed>");
+      free(escaped);
+      entry->referent_error = true;
+      goto skip;
+    }
+    entry->is_directory = S_ISDIR(entry->stats.st_mode);
+    if (entry->is_directory)
+      return 1;
+    goto apply_filters;
+  case LINK_ACTION_CARRY:
+    break;
+  }
+
+  /* Carry the link as a symlink.  --munge-links is applied by the RECEIVER (it
+     prefixes every stored target with /rsyncd-munged/); when the SOURCE already
+     holds a munged value the sender strips it so the receiver re-munges a clean
+     target, round-tripping a munged tree exactly like rsync. */
+  entry->is_symlink = true;
+  entry->stats = link_stats;
+  entry->is_directory = false;
+  entry->link_target = str_dup(link_target);
+  if (!entry->link_target)
+    goto skip;
+  if (options->munge_links)
+    file_symlink_unmunge(entry->link_target);
+  goto apply_filters;
+
+regular:
+  /* Not a symlink: the lstat() above already described this entry, and lstat
+     and stat are identical for every non-symlink, so reuse that result instead
+     of issuing a redundant stat() on the scanner hot path.  stat() is still
+     used on the dereference paths above/below for actual symlinks (copy-links,
+     safe/copy-unsafe links, and -k symlinks-to-directories). */
+  entry->stats = link_stats;
+  entry->is_directory = S_ISDIR(link_stats.st_mode);
+  if (entry->is_directory)
+    return 1;
+
+apply_filters:
+  for (int i = 0; i < options->exclude_count; i++)
+    if (glob_match(options->exclude_patterns[i], name)) {
+      entry->excluded = true;
+      goto skip;
+    }
+  if (options->include_count > 0) {
+    bool included = false;
+    for (int i = 0; i < options->include_count; i++)
+      if (glob_match(options->include_patterns[i], name))
+        included = true;
+    if (!included) {
+      entry->excluded = true;
+      goto skip;
+    }
+  }
+  if ((options->max_size > 0 && (unsigned long long)entry->stats.st_size > options->max_size) ||
+      (options->min_size > 0 && (unsigned long long)entry->stats.st_size < options->min_size)) {
+    entry->excluded = true;
+    entry->size_excluded = true;
+    goto skip;
+  }
+  return 1;
+
+skip:
+  free(entry->path);
+  entry->path = NULL;
+  free(entry->link_target);
+  entry->link_target = NULL;
+  return 0;
+}

src/client/scanner_internal.h

@@ -0,0 +1,132 @@
+#ifndef SCANNER_INTERNAL_H
+#define SCANNER_INTERNAL_H
+
+/* Internal declarations shared between the scanner translation units
+ * (scanner_filter.c, scanner.c, scanner_parallel.c).  Nothing here is part of
+ * the public scanner façade (scanner.h); every symbol stays internal to the
+ * client module. */
+
+#include "array_list.h"
+#include "file.h"
+#include "scanner.h"
+#include <stdbool.h>
+#include <stddef.h>
+#include <sys/stat.h>
+
+typedef struct {
+  char* path;
+  int depth;
+  FilterNode* context; /* inherited per-directory filter context */
+} DirEntry;
+
+/* How rsync's readlink_stat()/generator resolves one source symlink. */
+typedef enum {
+  LINK_ACTION_SKIP,           /* not transferred (no link option) */
+  LINK_ACTION_SKIP_PROTECTED, /* ignored as unsafe by --safe-links; rsync keeps
+                                 it in the transfer, so its destination mirror
+                                 must be protected from --delete */
+  LINK_ACTION_DEREF,          /* follow the referent (--copy-links, an unsafe
+                                 target under --copy-unsafe-links, or -k dir) */
+  LINK_ACTION_CARRY,          /* transmit the link itself (-l) */
+} LinkAction;
+
+typedef struct {
+  char* path;
+  struct stat stats;
+  bool is_directory;
+  /* True when the entry should be carried through as a SYMLINK (is_symlink)
+     rather than a dereferenced file/directory.  When true, `link_target` holds
+     the owned target string to transmit (sender-munged under --munge-links);
+     ownership transfers to the File built from this entry. */
+  bool is_symlink;
+  char* link_target;
+  /* True when the entry was pruned by a user selection rule (--filter/-C/per-dir
+     rules or the --exclude/--include layer) rather than skipped for another
+     reason (unreadable, symlink policy, not applicable). */
+  bool excluded;
+  /* True when the entry was skipped specifically by --max-size/--min-size.
+     Size pruning protects the destination mirror even under --delete-excluded,
+     so it is recorded into a separate sink from `excluded`. */
+  bool size_excluded;
+  /* True when a symlink selected for dereferencing (-L/--copy-links or an
+     unsafe target under --copy-unsafe-links) had no usable referent (a broken
+     link or a stat() failure).  rsync still reports this as a partial transfer
+     (exit 23) even though the entry is skipped, so the scanner records it as a
+     non-fatal I/O error. */
+  bool referent_error;
+} ScannerEntry;
+
+typedef enum {
+  SCANNER_SPECIAL_REGULAR,  /* ordinary file: transfer content */
+  SCANNER_SPECIAL_RECREATE, /* is_special node to recreate on the receiver */
+  SCANNER_SPECIAL_SKIP,     /* non-regular entry not requested: skip */
+} ScannerSpecial;
+
+/* Result of scanner_build_file_entry().  The two failure variants preserve the
+ * sequential scanner's historical distinction between a failure before the
+ * File existed (which kept walking the directory) and one afterwards (which cut
+ * the chunk short); both mark the scan failed. */
+typedef enum {
+  SCANNER_BUILD_OK,            /* File built; caller owns it */
+  SCANNER_BUILD_SKIP,          /* non-regular entry not preserved; no File */
+  SCANNER_BUILD_FAIL_CONTINUE, /* failed before the File existed */
+  SCANNER_BUILD_FAIL_BREAK,    /* failed after the File existed */
+} ScannerBuildStatus;
+
+/* scanner_filter.c */
+void filter_node_destroy(void* item);
+FilterNode* filter_node_alloc(FilterNode* parent, FilterRuleList* own);
+void dir_entry_destroy(void* item);
+DirEntry* dir_entry_create(const char* path, int depth, FilterNode* context);
+LinkAction scanner_link_action(const ScannerOptions* options, const char* path,
+                               const char* link_rel, char* target, size_t target_size);
+File* scanner_build_dir_file(const char* path, const struct stat* stats,
+                             const ScannerOptions* options);
+char* child_rel_path(const char* parent_rel, const char* name);
+char* scanner_prefix_send_path(const char* prefix, const char* rel);
+char* scanner_dest_rel_path(const ScannerOptions* options, const char* fs_path, const char* rel,
+                            bool relative_mode);
+bool entry_passes_selection(const FileListSet* file_list, const FilterRuleList* base,
+                            const FilterNode* node, const char* rel, const char* leaf, bool is_dir,
+                            bool per_dir_filters, bool exclude_filter_files, bool* protect_out);
+void scanner_capture_xattrs(const DirectoryScanner* scanner, File* file);
+void scanner_capture_xattrs_opts(const ScannerOptions* options, File* file);
+bool scanner_assign_hardlink(HardLinkTable* table, File* file, const struct stat* stats);
+ScannerSpecial scanner_prepare_special(bool preserve_devices, bool preserve_specials,
+                                       bool copy_devices, File* file, const struct stat* stats);
+/* Build one non-directory transfer File from an inspected entry.  `rel` is the
+ * entry's transfer-root-relative path (used for the -R wire path); `inspected`
+ * supplies the on-disk path, stats and (for a carried symlink) the target whose
+ * ownership transfers to the File.  Populates data size, send_path, special-node
+ * state, hardlink group, metadata and xattrs.  On SCANNER_BUILD_OK the caller
+ * owns *out_file; on SCANNER_BUILD_SKIP it is NULL and the entry is dropped; on
+ * either failure it is NULL and the caller must mark the scan failed.  `*failed`
+ * additionally reports a non-fatal hardlink-table allocation failure, in which
+ * case a usable File is still returned. */
+ScannerBuildStatus scanner_build_file_entry(const ScannerOptions* options, ScannerEntry* inspected,
+                                            const char* rel, File** out_file, bool* failed);
+bool excluded_sink_append(ArrayList* list, mtx_t* mtx, const char* rel);
+void scanner_note_nonreg(const ScannerOptions* options, const char* fs_path);
+void scanner_note_mount(const ScannerOptions* options, const char* fs_path);
+void scanner_note_filter(const ScannerOptions* options, const char* name);
+void scanner_dir_count_count(const ScannerOptions* options);
+void scanner_dir_count_uncount(const ScannerOptions* options);
+void scanner_record_excluded(DirectoryScanner* scanner, const char* fs_path);
+void scanner_record_size_skipped(DirectoryScanner* scanner, const char* fs_path);
+bool scanner_record_synced_dir(const ScannerOptions* options, const char* fs_path, const char* rel,
+                               bool relative_mode);
+FilterRuleList* read_dir_filters(const ScannerOptions* options, const char* dir_path,
+                                 const char* rel, bool relative_mode, bool* any_exists, char* err,
+                                 size_t err_size);
+int open_directory_filter_context(DirectoryScanner* scanner, const FilterNode* inherited);
+int scanner_inspect_entry(const ScannerOptions* options, const char* containing_dir,
+                          const char* link_rel, const char* name, ScannerEntry* entry);
+
+/* scanner.c */
+bool scanner_capture_dir_time(ArrayList* dir_entries, mtx_t* mutex, const char* root_path,
+                              const char* fs_path, bool relative_mode, const char* relative_prefix,
+                              bool preserve_atimes, bool preserve_crtimes, bool preserve_xattrs,
+                              bool preserve_acls, bool no_implied_dirs,
+                              const FileListSet* file_list);
+
+#endif

src/client/scanner_parallel.c

@@ -0,0 +1,681 @@
+#include "log.h"
+#include "scanner.h"
+#include "scanner_internal.h"
+#include "array_list.h"
+#include "chunk.h"
+#include "file.h"
+#include "queue.h"
+#include "utils.h"
+#include <dirent.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/sysmacros.h>
+#include <threads.h>
+#include <unistd.h>
+#include <limits.h>
+
+#include "xattr.h"
+
+typedef struct {
+  ParallelScanner* ps;
+  char** dirs;
+  int dir_count;
+  char* root_dir; /* the transfer root, for relative-path computation */
+  ScannerOptions options;
+  ProtocolSession* allocation_session;
+} ParallelWorkerArg;
+
+static int parallel_worker_thread(void* arg) {
+  ParallelWorkerArg* wa = (ParallelWorkerArg*)arg;
+  ProtocolSession* allocation_session = wa->allocation_session;
+  if (allocation_session)
+    protocol_session_bind(allocation_session);
+  for (int i = 0; i < wa->dir_count; i++) {
+    DirectoryScanner* ds = directory_scanner_create_with_options(wa->dirs[i], &wa->options);
+    if (!ds) {
+      mtx_lock(&wa->ps->result_mutex);
+      wa->ps->failed = true;
+      atomic_store(&wa->ps->cancelled, true);
+      cnd_broadcast(&wa->ps->result_not_empty);
+      cnd_broadcast(&wa->ps->result_not_full);
+      mtx_unlock(&wa->ps->result_mutex);
+      for (int j = i; j < wa->dir_count; j++)
+        free(wa->dirs[j]);
+      break;
+    }
+    /* Root .rsync-filter rules (parsed by the parallel scanner) apply to the
+     * contents of every assigned subdirectory. Relative paths (used by the
+     * allow-set and per-directory rules) are computed against the transfer
+     * root, not the subdirectory the worker is seeded with.  Exclusion
+     * recording shares one caller-owned list across the workers. */
+    free(ds->root_path);
+    ds->root_path = str_dup(wa->root_dir);
+    ds->seed_node = wa->ps->root_filter_node;
+    ds->options.excluded_mutex = &wa->ps->result_mutex;
+    Chunk* chunk;
+    while ((chunk = directory_scanner_next(ds)) != NULL) {
+      if (!queue_enqueue_multithreaded_cancel(wa->ps->result_queue, chunk, &wa->ps->result_mutex,
+                                              &wa->ps->result_not_empty, &wa->ps->result_not_full,
+                                              &wa->ps->cancelled)) {
+        chunk_destroy(chunk);
+        break;
+      }
+    }
+    if (directory_scanner_failed(ds)) {
+      mtx_lock(&wa->ps->result_mutex);
+      wa->ps->failed = true;
+      atomic_store(&wa->ps->cancelled, true);
+      cnd_broadcast(&wa->ps->result_not_empty);
+      cnd_broadcast(&wa->ps->result_not_full);
+      mtx_unlock(&wa->ps->result_mutex);
+    } else if (directory_scanner_had_io_error(ds)) {
+      /* --ignore-errors path: an unreadable directory was skipped, not fatal. */
+      mtx_lock(&wa->ps->result_mutex);
+      wa->ps->io_error = true;
+      mtx_unlock(&wa->ps->result_mutex);
+    }
+    directory_scanner_destroy(ds);
+    free(wa->dirs[i]);
+  }
+  ParallelScanner* ps = wa->ps;
+  free(wa->root_dir);
+  free(wa->dirs);
+  free(wa);
+  mtx_lock(&ps->result_mutex);
+  ps->completed++;
+  if (ps->completed >= ps->expected_threads) {
+    ps->done = true;
+    cnd_signal(&ps->result_not_empty);
+  }
+  mtx_unlock(&ps->result_mutex);
+  if (allocation_session)
+    protocol_session_unbind();
+  return thrd_success;
+}
+
+static void parallel_scanner_creation_failed(ParallelScanner* ps) {
+  mtx_lock(&ps->result_mutex);
+  ps->failed = true;
+  atomic_store(&ps->cancelled, true);
+  ps->expected_threads = ps->created_threads;
+  if (ps->completed >= ps->expected_threads)
+    ps->done = true;
+  cnd_broadcast(&ps->result_not_empty);
+  cnd_broadcast(&ps->result_not_full);
+  mtx_unlock(&ps->result_mutex);
+}
+
+/* Initialize result queue and synchronization primitives. Returns true on success. */
+static bool parallel_scanner_init(ParallelScanner* ps) {
+  ps->result_queue = queue_create(SCANNER_RESULT_QUEUE_CAP, chunk_destroy);
+  if (!ps->result_queue)
+    return false;
+  atomic_init(&ps->cancelled, false);
+  int init = 0;
+  bool ok = true;
+  if (mtx_init(&ps->result_mutex, mtx_plain) != thrd_success)
+    ok = false;
+  if (ok) {
+    init++;
+    if (cnd_init(&ps->result_not_empty) != thrd_success)
+      ok = false;
+  }
+  if (ok) {
+    // cppcheck-suppress unreadVariable
+    init++;
+    if (cnd_init(&ps->result_not_full) != thrd_success)
+      ok = false;
+  }
+  if (!ok) {
+    if (init >= 3)
+      cnd_destroy(&ps->result_not_full);
+    if (init >= 2)
+      cnd_destroy(&ps->result_not_empty);
+    if (init >= 1)
+      mtx_destroy(&ps->result_mutex);
+    queue_destroy(ps->result_queue);
+    ps->result_queue = NULL;
+    return false;
+  }
+  return true;
+}
+
+/* Split files into chunks of roughly chunk_size bytes. Returns the first chunk (also stored
+ * chunks beyond the first are enqueued on `queue`). Nulls out consumed entries in `files`.
+ * Sets *failed on allocation/enqueue errors. */
+static Chunk* batch_files(ArrayList* files, unsigned long long chunk_size, Queue* queue,
+                          bool* failed) {
+  Chunk* first = NULL;
+  if (files->size <= 0)
+    return NULL;
+  ArrayList* batch = array_list_create(NULL);
+  if (!batch) {
+    *failed = true;
+    return NULL;
+  }
+  unsigned long long batch_size = 0;
+  for (int i = 0; i < files->size; i++) {
+    File* f = (File*)files->items[i];
+    if (!array_list_add(batch, f)) {
+      *failed = true;
+      break;
+    }
+    batch_size += f->data->size;
+    if (batch_size >= chunk_size || i == files->size - 1) {
+      void** items = array_list_to_array(batch);
+      if (!items) {
+        *failed = true;
+        array_list_delete(batch);
+        batch = NULL;
+        break;
+      }
+      Chunk* c = chunk_create((File**)items, batch->size);
+      free(items);
+      if (!c) {
+        *failed = true;
+        array_list_delete(batch);
+        batch = NULL;
+        break;
+      }
+      int batch_start = i - batch->size + 1;
+      for (int j = batch_start; j <= i; j++)
+        files->items[j] = NULL;
+      batch->item_destroyer = NULL;
+      array_list_delete(batch);
+      batch = NULL;
+      if (!first) {
+        first = c;
+      } else {
+        if (!queue_enqueue(queue, c)) {
+          chunk_destroy(c);
+          *failed = true;
+        }
+      }
+      if (i < files->size - 1) {
+        batch = array_list_create(NULL);
+        if (!batch) {
+          *failed = true;
+          break;
+        }
+        batch_size = 0;
+      }
+    }
+  }
+  if (batch) {
+    batch->item_destroyer = NULL;
+    array_list_delete(batch);
+  }
+  return first;
+}
+
+/* Record the delete-protection mirror of a root entry that
+ * scanner_inspect_entry() skipped (inspection == 0): a dereferenced symlink
+ * with no referent is a partial-transfer I/O error and a user-selection or size
+ * prune protects the entry's destination mirror. */
+static void scan_root_record_skipped(const ScannerOptions* options, const char* root_directory,
+                                     const char* name, const ScannerEntry* inspected,
+                                     ParallelScanner* ps) {
+  if (inspected->referent_error)
+    ps->io_error = true;
+  ArrayList* sink = NULL;
+  if (inspected->excluded)
+    sink = inspected->size_excluded ? options->size_skipped_paths : options->excluded_paths;
+  if (!sink)
+    return;
+  /* A root-level prune protects the destination mirror of the entry's wire
+     path: under -R + --files-from that is the bare relative name, otherwise it
+     is the full source path with a leading '/' removed (matching the
+     send_path/file_wire_path the scanner hands the sender). */
+  if (options->relative && options->file_list != NULL) {
+    if (!excluded_sink_append(sink, options->excluded_mutex, name))
+      ps->failed = true;
+  } else if (options->relative_prefix) {
+    char* wrel = scanner_prefix_send_path(options->relative_prefix, name);
+    if (!wrel) {
+      ps->failed = true;
+    } else {
+      if (!excluded_sink_append(sink, options->excluded_mutex, wrel))
+        ps->failed = true;
+      free(wrel);
+    }
+  } else {
+    char* abs_path = path_cat(root_directory, name);
+    if (!abs_path) {
+      ps->failed = true;
+    } else {
+      const char* rel = *abs_path == '/' ? abs_path + 1 : abs_path;
+      if (!excluded_sink_append(sink, options->excluded_mutex, rel))
+        ps->failed = true;
+      free(abs_path);
+    }
+  }
+}
+
+/* Record the delete-protection mirror of a root entry dropped by the
+ * --files-from allow-set or a filter rule.  Returns false only when the -R
+ * prefix could not be built (the caller must abandon the entry immediately);
+ * other allocation failures mark the scan failed but let the caller continue to
+ * the filter-notice step, matching the historical inlined flow. */
+static bool scan_root_record_protection(const ScannerOptions* options, const char* rel,
+                                        const char* name, const char* cur_path, bool protect,
+                                        bool passes, bool use_rel, ParallelScanner* ps) {
+  if (passes && !protect)
+    return true;
+  /* --files-from subset pruning is not a filter exclusion; -R bare-wire-path
+     exclusions are never recorded (see ScannerOptions.excluded_paths). */
+  bool files_from_prune = options->file_list && !file_list_affects(options->file_list, rel);
+  if ((!files_from_prune && !use_rel) || protect) {
+    const char* rel_path;
+    char* prefixed = NULL;
+    if (use_rel) {
+      /* -R + --files-from: the destination/wire path is the bare relative
+         name, not the source path. */
+      rel_path = rel;
+    } else if (options->relative_prefix) {
+      prefixed = scanner_prefix_send_path(options->relative_prefix, name);
+      if (!prefixed)
+        return false;
+      rel_path = prefixed;
+    } else {
+      rel_path = *cur_path == '/' ? cur_path + 1 : cur_path;
+    }
+    if (options->excluded_paths &&
+        !excluded_sink_append(options->excluded_paths, options->excluded_mutex, rel_path))
+      ps->failed = true;
+    free(prefixed);
+  }
+  return true;
+}
+
+/* Root-level directory node: apply -x/--one-file-system and either emit the
+ * mount-point directory (plain -x) or queue the directory for a worker. */
+static void scan_root_dir(const ScannerOptions* options, const char* cur_path, const char* rel,
+                          const struct stat* st, ArrayList* root_files, ArrayList* subdirs,
+                          dev_t root_dev, ParallelScanner* ps) {
+  if (!scanner_same_filesystem(options->one_file_system, root_dev, st->st_dev)) {
+    if (options->one_file_system > 1) {
+      /* -xx: drop the mount-point directory entirely (rsync) and print the
+         --info=mount line when enabled. */
+      scanner_note_mount(options, cur_path);
+      return;
+    }
+    /* -x/--one-file-system: emit the mount-point directory entry (empty) but do
+       not descend into it (see the sequential scanner for the same rule). */
+    File* mount = scanner_build_dir_file(cur_path, st, options);
+    if (!mount) {
+      ps->failed = true;
+      return;
+    }
+    if (options->relative_prefix) {
+      mount->send_path = scanner_prefix_send_path(options->relative_prefix, rel);
+      if (!mount->send_path) {
+        file_destroy(mount);
+        ps->failed = true;
+        return;
+      }
+    }
+    if (!array_list_add(root_files, mount)) {
+      file_destroy(mount);
+      ps->failed = true;
+    }
+    return;
+  }
+  char* dir = str_dup(cur_path);
+  if (!dir || !array_list_add(subdirs, dir)) {
+    free(dir);
+    ps->failed = true;
+  }
+}
+
+/* Build a non-directory root entry through the shared construction path and add
+ * it to `root_files`.  A non-regular entry the options do not preserve is
+ * dropped by the builder (which prints rsync's nonreg line); an allocation
+ * failure marks the scan failed. */
+static void scan_root_add_non_dir(const ScannerOptions* options, ScannerEntry* inspected,
+                                  const char* rel, ArrayList* root_files, ParallelScanner* ps) {
+  File* file = NULL;
+  bool failed = false;
+  ScannerBuildStatus status = scanner_build_file_entry(options, inspected, rel, &file, &failed);
+  if (failed || status == SCANNER_BUILD_FAIL_CONTINUE || status == SCANNER_BUILD_FAIL_BREAK)
+    ps->failed = true;
+  if (status != SCANNER_BUILD_OK)
+    return;
+  if (!array_list_add(root_files, file)) {
+    file_destroy(file);
+    ps->failed = true;
+  }
+}
+
+/* Regular file or carried symlink at the transfer root. */
+static void scan_root_file(const ScannerOptions* options, ScannerEntry* inspected, const char* rel,
+                           ArrayList* root_files, ParallelScanner* ps) {
+  scan_root_add_non_dir(options, inspected, rel, root_files, ps);
+}
+
+/* Device/FIFO/socket at the transfer root: recreated under --devices/--specials,
+ * otherwise dropped by the shared builder. */
+static void scan_root_special(const ScannerOptions* options, ScannerEntry* inspected,
+                              const char* rel, ArrayList* root_files, ParallelScanner* ps) {
+  scan_root_add_non_dir(options, inspected, rel, root_files, ps);
+}
+
+/* Scan one root-directory entry into either the subdirs or files list. */
+static void scan_root_entry(const ScannerOptions* options, const FilterNode* root_node,
+                            const char* root_directory, const struct dirent* entry,
+                            ArrayList* root_files, ArrayList* subdirs, dev_t root_dev,
+                            ParallelScanner* ps) {
+  ScannerEntry inspected;
+  int inspection =
+      scanner_inspect_entry(options, root_directory, entry->d_name, entry->d_name, &inspected);
+  if (inspection < 0) {
+    ps->failed = true;
+    return;
+  }
+  if (inspection == 0) {
+    scan_root_record_skipped(options, root_directory, entry->d_name, &inspected, ps);
+    return;
+  }
+  char* cur_path = inspected.path;
+  char* rel = str_dup(entry->d_name);
+  if (!rel) {
+    ps->failed = true;
+    goto done;
+  }
+  bool is_dir = inspected.is_directory;
+  bool protect = false;
+  bool passes = entry_passes_selection(options->file_list, options->base_filters, root_node, rel,
+                                       entry->d_name, is_dir, options->per_dir_filters,
+                                       options->exclude_per_dir_filter_files, &protect);
+  /* -R + --files-from: root-level files keep their bare relative send path. */
+  bool use_rel = options->relative && options->file_list != NULL;
+  if (!passes || protect) {
+    if (!scan_root_record_protection(options, rel, entry->d_name, cur_path, protect, passes,
+                                     use_rel, ps)) {
+      ps->failed = true;
+      goto done;
+    }
+    if (!passes) {
+      scanner_note_filter(options, entry->d_name);
+      goto done;
+    }
+  }
+  if (is_dir) {
+    scan_root_dir(options, cur_path, rel, &inspected.stats, root_files, subdirs, root_dev, ps);
+  } else if (S_ISCHR(inspected.stats.st_mode) || S_ISBLK(inspected.stats.st_mode) ||
+             S_ISFIFO(inspected.stats.st_mode) || S_ISSOCK(inspected.stats.st_mode)) {
+    scan_root_special(options, &inspected, rel, root_files, ps);
+  } else {
+    scan_root_file(options, &inspected, rel, root_files, ps);
+  }
+done:
+  free(rel);
+  free(cur_path);
+  free(inspected.link_target);
+}
+
+/* Scan the root directory itself, collecting root files and subdirectories.
+ * Returns false if the root directory could not be opened. */
+static bool scan_root_directory(ParallelScanner* ps, const char* root_directory,
+                                const ScannerOptions* options, const FilterNode* root_node,
+                                dev_t root_dev, ArrayList* root_files, ArrayList* subdirs) {
+  DIR* dir = opendir(root_directory);
+  if (!dir) {
+    log_perror("Could not open root directory for parallel scan");
+    return false;
+  }
+  /* The parallel scanner opens the transfer root directly (not through
+     open_next_directory), so record it as synchronized here. */
+  if (!scanner_record_synced_dir(options, root_directory, "",
+                                 options->relative && options->file_list != NULL)) {
+    closedir(dir);
+    ps->failed = true;
+    return false;
+  }
+  log_debug_message(LOG_DEBUG_FLIST, "flist: scanning %s", root_directory);
+  const struct dirent* entry;
+  while ((entry = readdir(dir)) != NULL) {
+    if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
+      continue;
+    scan_root_entry(options, root_node, root_directory, entry, root_files, subdirs, root_dev, ps);
+  }
+  closedir(dir);
+  return true;
+}
+
+/* Spawn worker threads, one per group of subdirectories. */
+static void spawn_parallel_workers(ParallelScanner* ps, ArrayList* subdirs,
+                                   const ScannerOptions* options, const char* root_directory,
+                                   unsigned long long cs) {
+  if (subdirs->size <= 0)
+    return;
+  int n = options->num_threads > 0 ? options->num_threads : 4;
+  if (n > subdirs->size)
+    n = subdirs->size;
+
+  ps->num_threads = n;
+  ps->expected_threads = n;
+  ps->threads = calloc(n, sizeof(thrd_t));
+  if (!ps->threads) {
+    ps->num_threads = 0;
+    ps->expected_threads = 0;
+    ps->failed = true;
+    return;
+  }
+  int dirs_per_thread = subdirs->size / n;
+  int remainder = subdirs->size % n;
+  int start = 0;
+  ps->num_threads = 0;
+  for (int t = 0; t < n; t++) {
+    int count = dirs_per_thread + (t < remainder ? 1 : 0);
+    if (count == 0)
+      break;
+    ParallelWorkerArg* wa = calloc(1, sizeof(ParallelWorkerArg));
+    if (!wa) {
+      parallel_scanner_creation_failed(ps);
+      break;
+    }
+    wa->ps = ps;
+    wa->dirs = calloc(count, sizeof(char*));
+    wa->root_dir = str_dup(root_directory);
+    if (!wa->dirs || !wa->root_dir) {
+      free(wa->root_dir);
+      free(wa->dirs);
+      free(wa);
+      parallel_scanner_creation_failed(ps);
+      break;
+    }
+    bool dup_ok = true;
+    for (int j = 0; j < count; j++) {
+      wa->dirs[j] = str_dup((char*)subdirs->items[start + j]);
+      if (!wa->dirs[j])
+        dup_ok = false;
+    }
+    if (!dup_ok) {
+      for (int j = 0; j < count; j++)
+        free(wa->dirs[j]);
+      free(wa->root_dir);
+      free(wa->dirs);
+      free(wa);
+      parallel_scanner_creation_failed(ps);
+      break;
+    }
+    wa->dir_count = count;
+    wa->options = *options;
+    wa->options.chunk_size = cs;
+    wa->allocation_session = ps->allocation_session;
+    start += count;
+    if (thrd_create(&ps->threads[t], parallel_worker_thread, wa) != thrd_success) {
+      for (int j = 0; j < count; j++)
+        free(wa->dirs[j]);
+      free(wa->root_dir);
+      free(wa->dirs);
+      free(wa);
+      parallel_scanner_creation_failed(ps);
+      break;
+    }
+    ps->num_threads++;
+    ps->created_threads++;
+  }
+}
+
+ParallelScanner* parallel_scanner_create_with_options(const char* root_directory,
+                                                      const ScannerOptions* options,
+                                                      ProtocolSession* allocation_session) {
+  if (!root_directory || !options)
+    return NULL;
+  ParallelScanner* ps = calloc(1, sizeof(ParallelScanner));
+  if (!ps)
+    return NULL;
+  if (!parallel_scanner_init(ps)) {
+    free(ps);
+    return NULL;
+  }
+  ps->allocation_session = allocation_session;
+  ps->options = options;
+
+  ArrayList* root_files = array_list_create(file_destroy);
+  ArrayList* subdirs = array_list_create(free);
+  if (!root_files || !subdirs) {
+    array_list_delete(root_files);
+    array_list_delete(subdirs);
+    parallel_scanner_destroy(ps);
+    return NULL;
+  }
+
+  dev_t root_dev = 0;
+  if (options->one_file_system) {
+    struct stat root_stats;
+    if (stat(root_directory, &root_stats) != 0) {
+      log_perror("Could not stat source directory");
+      array_list_delete(root_files);
+      array_list_delete(subdirs);
+      parallel_scanner_destroy(ps);
+      return NULL;
+    }
+    root_dev = root_stats.st_dev;
+  }
+
+  /* Build the root directory's per-directory filter context once; workers seed
+   * their scanners with it so per-dir rules behave identically to the sequential
+   * scanner. */
+  FilterNode* root_node = NULL;
+  {
+    char err[256];
+    bool any_exists = false;
+    FilterRuleList* own = read_dir_filters(options, root_directory, "",
+                                           options->relative && options->file_list != NULL,
+                                           &any_exists, err, sizeof(err));
+    if (!own) {
+      /* A parse/allocation failure must fail the scan even when an earlier
+         merge file in the same directory existed (see the sequential scanner). */
+      if (err[0] != '\0') {
+        log_message(LOG_LEVEL_ERROR, "invalid per-directory filter in %s: %s", root_directory, err);
+        array_list_delete(root_files);
+        array_list_delete(subdirs);
+        parallel_scanner_destroy(ps);
+        return NULL;
+      }
+      /* no files exist: leave root_node NULL */
+    } else if (any_exists && (own->count > 0 || own->dir_merge_count > 0)) {
+      root_node = filter_node_alloc(NULL, own);
+      if (!root_node) {
+        filter_rule_list_free(own);
+        array_list_delete(root_files);
+        array_list_delete(subdirs);
+        parallel_scanner_destroy(ps);
+        return NULL;
+      }
+    } else {
+      filter_rule_list_free(own);
+    }
+  }
+  ps->root_filter_node = root_node;
+
+  if (!scan_root_directory(ps, root_directory, options, root_node, root_dev, root_files, subdirs)) {
+    array_list_delete(root_files);
+    array_list_delete(subdirs);
+    parallel_scanner_destroy(ps);
+    return NULL;
+  }
+  /* The root itself is a traversed directory (rsync counts it in
+     `Number of files`); the worker DirectoryScanners account for every
+     subdirectory below it. */
+  scanner_dir_count_count(options);
+  /* P7 Wave D: the parallel scanner never runs a DirectoryScanner over the
+     transfer root itself (it hands the root's immediate subdirectories to
+     workers), so capture the root's directory time here. */
+  if (options->capture_dir_times &&
+      !scanner_capture_dir_time(
+          options->dir_entries, options->dir_entries_mutex, root_directory, root_directory,
+          options->relative && options->file_list != NULL, options->relative_prefix,
+          options->preserve_atimes, options->preserve_crtimes, options->preserve_xattrs,
+          options->preserve_acls, options->no_implied_dirs, options->file_list)) {
+    array_list_delete(root_files);
+    array_list_delete(subdirs);
+    parallel_scanner_destroy(ps);
+    return NULL;
+  }
+
+  unsigned long long cs = options->chunk_size > 0 ? options->chunk_size : DESIRED_CHUNK_SIZE;
+  ps->initial_chunk = batch_files(root_files, cs, ps->result_queue, &ps->failed);
+  array_list_delete(root_files);
+
+  spawn_parallel_workers(ps, subdirs, options, root_directory, cs);
+  array_list_delete(subdirs);
+  return ps;
+}
+
+Chunk* parallel_scanner_next(ParallelScanner* ps) {
+  if (ps->initial_chunk) {
+    Chunk* c = ps->initial_chunk;
+    ps->initial_chunk = NULL;
+    return c;
+  }
+  if (ps->num_threads == 0) {
+    mtx_lock(&ps->result_mutex);
+    if (!queue_is_empty(ps->result_queue)) {
+      Chunk* chunk = queue_dequeue(ps->result_queue);
+      mtx_unlock(&ps->result_mutex);
+      return chunk;
+    }
+    ps->done = true;
+    mtx_unlock(&ps->result_mutex);
+    return NULL;
+  }
+  Chunk* chunk = queue_dequeue_multithreaded(
+      ps->result_queue, &ps->result_mutex, &ps->result_not_empty, &ps->result_not_full, &ps->done);
+  return chunk;
+}
+
+bool parallel_scanner_failed(const ParallelScanner* ps) {
+  return ps == NULL || ps->failed;
+}
+
+bool parallel_scanner_had_io_error(const ParallelScanner* ps) {
+  return ps != NULL && ps->io_error;
+}
+
+void parallel_scanner_destroy(ParallelScanner* ps) {
+  if (!ps)
+    return;
+  mtx_lock(&ps->result_mutex);
+  ps->done = true;
+  atomic_store(&ps->cancelled, true);
+  cnd_broadcast(&ps->result_not_empty);
+  cnd_broadcast(&ps->result_not_full);
+  mtx_unlock(&ps->result_mutex);
+  for (int i = 0; i < ps->num_threads; i++)
+    thrd_join(ps->threads[i], NULL);
+  free(ps->threads);
+  if (ps->root_filter_node)
+    filter_node_destroy(ps->root_filter_node);
+  if (ps->initial_chunk)
+    chunk_destroy(ps->initial_chunk);
+  queue_destroy(ps->result_queue);
+  mtx_destroy(&ps->result_mutex);
+  cnd_destroy(&ps->result_not_empty);
+  cnd_destroy(&ps->result_not_full);
+  free(ps);
+}

src/client/usage.c

@@ -19,11 +19,16 @@ void print_usage(void) {
   printf("\n");
   printf("Options:\n");
   printf("  -c, --checksum      Verify content by checksum instead of size+mtime\n");
-  printf("  -z, --compress [level]  Enable compression (level 1-22, default 5)\n");
+  printf("  -z, --compress [level]  Enable compression.  The default level is\n");
+  printf("                      per-codec: zstd 3 (range 1-22), zlib/zlibx 6, lz4\n");
+  printf("                      ignores the level\n");
   printf("  -a, --archive       rsync archive mode (-rlptgoD): links, perms, times,\n");
   printf("                      owner, group, devices and specials; not\n");
   printf("                      compression/multithreading\n");
   printf("  -r, --recursive     Recurse into directories (FastSync is always recursive)\n");
+  printf("  --inc-recursive     Accepted for rsync CLI compatibility; no effect (FastSync\n");
+  printf("                      always performs a full scan, so the destination is identical)\n");
+  printf("  --no-inc-recursive  Accepted for rsync CLI compatibility; no effect\n");
   printf("  -n, --dry-run       Show what would be transferred\n");
   printf("  --remove-source-files  Remove regular source files after successful transfer\n");
   printf("  -p, --perms         Preserve permission bits\n");
@@ -36,8 +41,8 @@ void print_usage(void) {
   printf("                      arguments, e.g. -e \"ssh -p 2222\"\n");
   printf("  --rsync-path <path>  Alias for --fastsync-server-path (path to the\n");
   printf("                      fastsync server binary on the remote side)\n");
-  printf("  --blocking-io        Leave the SSH transport socket without read/write\n");
-  printf("                      timeouts so it blocks naturally\n");
+  printf("  --blocking-io        SSH transport only: leave the socket without read/write\n");
+  printf("                      timeouts so it blocks naturally (no effect on TCP)\n");
   printf("  --outbuf=MODE        stdout/stderr buffering: N (none/unbuffered),\n");
   printf("                      L (line-buffered), or B (block-buffered, default)\n");
   printf("  --progress          Show transfer progress\n");
@@ -49,6 +54,7 @@ void print_usage(void) {
   printf("                      converted before transmission and back on receipt; a\n");
   printf("                      name that cannot be represented in the target charset\n");
   printf("                      fails that transfer cleanly (rsync-compatible)\n");
+  printf("  --no-iconv          Disable --iconv charset conversion (same as --iconv=-)\n");
   printf("  --protocol=NUM       Force the wire protocol version (must equal the current\n");
   printf("                       PROTOCOL_VERSION; FastSync cannot speak older/virtual\n");
   printf("                       wire formats)\n");
@@ -162,7 +168,7 @@ void print_usage(void) {
   printf("                    --no-delta, or --no-incremental)\n");
   printf("  --no-fuzzy          Disable --fuzzy\n");
   printf("  -B <n>, --block-size <n>, --delta-block <n>\n");
-  printf("                    Delta block size in bytes (default: %d)\n", DELTA_BLOCK_SIZE_DEFAULT);
+  printf("                    Delta block size in bytes (default: %u)\n", DELTA_BLOCK_SIZE_DEFAULT);
   printf("  --delta-max <n>     Max file size for delta transfer (default: %llu)\n",
          DELTA_MAX_FILE_SIZE);
   printf("  -j, --threads[=N]   Enable the multithreaded scanner/loader/sender\n");
@@ -192,16 +198,21 @@ void print_usage(void) {
   printf("  -U, --atimes        Preserve access times\n");
   printf("  -N, --crtimes       Capture birth time; cannot be applied (documented\n");
   printf("                      divergence)\n");
+  printf("  -O, --omit-dir-times  Do not apply modification times to directories\n");
+  printf("  -J, --omit-link-times Do not apply times to symlinks\n");
+  printf("  --open-noatime      Open source files with O_NOATIME so reading for a\n");
+  printf("                      transfer does not update their access time\n");
   printf("  -X, --xattrs        Preserve user extended attributes (user.* only;\n");
   printf("                      privileged security.*/trusted.* namespaces are\n");
   printf("                      never captured or applied)\n");
   printf("  -A, --acls          Preserve POSIX ACLs (the system.posix_acl_* xattrs;\n");
   printf("                      setting an ACL the receiver is not permitted to\n");
   printf("                      set is warned and skipped, never fatal)\n");
-  printf("  --fake-super        Store the source uid/gid/mode/mtime in a reserved\n");
-  printf("                      user.fastsync.stat xattr on each written file and\n");
-  printf("                      re-apply it (fd-relative) on a privileged run; the\n");
-  printf("                      recording format diverges from rsync's user.rsync.%%stat%%\n");
+  printf("  --fake-super        Store the source mode/rdev/uid/gid in rsync's\n");
+  printf("                      reserved user.rsync.%%stat xattr on each written\n");
+  printf("                      file (interoperable with rsync); it never performs a\n");
+  printf("                      real chown, so an unprivileged receiver records the\n");
+  printf("                      privileged stat for a later restore\n");
   printf("  --super             Permit the receiver to attempt super-user activities\n");
   printf("                      (char/block device-node creation, --write-devices)\n");
   printf("                      within the confined receive root.  Never elevates\n");
@@ -286,9 +297,15 @@ void print_usage(void) {
   printf("  --max-depth <n>     Maximum directory depth (0=unlimited)\n");
   printf("  -x, --one-file-system  Do not cross filesystem boundaries\n");
   printf("  --log-file <path>, --log-file=<path>  Write log messages to file\n");
-  printf("  --stderr=MODE       Route logging to stderr: errors or all\n");
+  printf("  --stderr=MODE       Route logging: errors (default), all, or client\n");
+  printf("                      (forward the client's diagnostics to the server's\n");
+  printf("                      stderr)\n");
+  printf("  --msgs2stderr       Route all messages to stderr (deprecated spelling of\n");
+  printf("                      --stderr=all)\n");
+  printf("  --no-msgs2stderr    Forward the client's diagnostics to the server\n");
+  printf("                      (deprecated spelling of --stderr=client)\n");
   printf("  --partial           Keep partial files on interrupted transfer\n");
-  printf("  --partial-dir <dir> Directory for partial files\n");
+  printf("  --partial-dir <dir> Directory for partial files (implies --partial)\n");
   printf("  -T, --temp-dir <dir>  Scratch dir for temp files before atomic install.\n");
   printf("                      Confined to the receive root: a relative dir resolves below\n");
   printf("                      it and an absolute/traversal dir is rejected.  The dir must\n");
@@ -337,7 +354,8 @@ void print_usage(void) {
   printf("  --append-verify     Like --append, but verifies the retained prefix checksum\n");
   printf("                    before appending (falls back to a full transfer on mismatch)\n");
   printf("  --fsync             Fsync every written file before publication\n");
-  printf("  --compress-level <n>    Compression level (default: 5)\n");
+  printf("  --compress-level <n>    Compression level (per-codec default: zstd 3,\n");
+  printf("                      zlib/zlibx 6, lz4 ignores it)\n");
   printf("  --zl <n>             Alias for --compress-level\n");
   printf("  --skip-compress=LIST    Skip compression for suffixes in LIST (separated by\n");
   printf("                      '/' as in rsync, or ','); a leading dot is optional.  The\n");
@@ -349,19 +367,19 @@ void print_usage(void) {
 }
 
 void print_debug_usage(void) {
-  printf("Emitting debug flags: IO,PROTO,PACK,UTIL,ALL,NONE\n");
+  printf("Emitting debug flags: IO,PROTO,PACK,UTIL,FLIST,DEL,HASH,DELTASUM,\n");
+  printf("RECV,FILTER,SEND,ALL,NONE\n");
   printf("Also accepted for rsync CLI parity (silent): ACL,BACKUP,BIND,CHDIR,\n");
-  printf("CONNECT,CMD,DEL,DELTASUM,DUP,EXIT,FILTER,FLIST,FUZZY,GENR,HASH,HLINK,\n");
-  printf("ICONV,NSTR,OWN,RECV,SEND,TIME.\n");
+  printf("CONNECT,CMD,DUP,EXIT,FUZZY,GENR,HLINK,ICONV,NSTR,OWN,TIME.\n");
   printf("Flags may be comma-separated, for example: --debug=io,proto\n");
   printf("An optional level suffix is accepted (e.g. --debug=io2); level 0\n");
   printf("silences that item.  Unknown names are rejected.\n");
 }
 
 void print_info_usage(void) {
-  printf("Emitting info flags: COPY,NAME,MISC,SKIP,STATS,ALL,NONE\n");
-  printf("Also accepted for rsync CLI parity (silent): BACKUP,DEL,FLIST,MOUNT,\n");
-  printf("NONREG,PROGRESS,REMOVE,SYMSAFE.\n");
+  printf("Emitting info flags: COPY,MISC,SKIP,STATS,DEL,REMOVE,NAME,FLIST,\n");
+  printf("NONREG,PROGRESS,MOUNT,ALL,NONE\n");
+  printf("Also accepted for rsync CLI parity (silent): BACKUP,SYMS,SYMSAFE.\n");
   printf("Flags may be comma-separated, for example: --info=name,stats\n");
   printf("An optional level suffix is accepted (e.g. --info=stats2); level 0\n");
   printf("silences that item.  Unknown names are rejected.\n");

src/server/receiver.c

@@ -11,10 +11,13 @@
 #include "metadata.h"
 #include "protocol.h"
 #include "utils.h"
+#include <fcntl.h>
+#include <limits.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/stat.h>
 #include <time.h>
+#include <unistd.h>
 
 bool receiver_outcomes_append(ReceiverOutcomes* outcomes, unsigned char code) {
   if (!outcomes)
@@ -53,7 +56,13 @@ bool receiver_send_final_success(int fd, const Config* config, const ReceiverOut
     return send_status(fd, final_status);
   size_t count = outcomes ? outcomes->count : 0;
   for (size_t i = 0; i < count; i++) {
-    Status per_file = outcomes->entries[i] == FILE_SAVE_WRITTEN ? STATUS_NEXT : STATUS_OK;
+    Status per_file;
+    if (outcomes->entries[i] == FILE_SAVE_WRITTEN)
+      per_file = STATUS_NEXT;
+    else if (outcomes->entries[i] == FILE_SAVE_FAILED)
+      per_file = STATUS_ERROR;
+    else
+      per_file = STATUS_OK;
     if (!send_status(fd, per_file))
       return false;
   }
@@ -95,14 +104,35 @@ static void receiver_tally_deleted(const ReceiverSink* sink, size_t deleted) {
     sink->stats->deleted_files += deleted;
 }
 
-/* Observer for --info=del: record each truly-removed destination-relative path
-   in the ArrayList passed as the observer context, so the terminal STATUS_STATS
-   frame can list it.  A failed append is best-effort (the deletion already
-   happened; output is cosmetic).  Shared by the single-threaded receiver and
-   the -m pipeline's deferred commit. */
-void receiver_record_deleted_path(void* context, const char* rel_path) {
-  ArrayList* paths = context;
-  if (!paths || !rel_path)
+/* Observer for --info=del/--stats: record each truly-removed destination-
+   relative path (when the context carries a path list) and tally it by type
+   (when it carries a stats record), so the terminal STATUS_STATS frame can list
+   the paths and render rsync's per-type `Number of deleted files` breakdown.  A
+   failed append is best-effort (the deletion already happened; output is
+   cosmetic).  Shared by the single-threaded receiver and the -m pipeline's
+   deferred commit. */
+void receiver_record_deleted_path(void* context, const char* rel_path, DeleteEntryType type) {
+  ReceiverDeleteContext* del = context;
+  if (!del || !rel_path)
+    return;
+  if (del->stats) {
+    switch (type) {
+    case DELETE_ENTRY_DIR:
+      del->stats->deleted_dir++;
+      break;
+    case DELETE_ENTRY_LINK:
+      del->stats->deleted_link++;
+      break;
+    case DELETE_ENTRY_SPECIAL:
+      del->stats->deleted_special++;
+      break;
+    default:
+      del->stats->deleted_reg++;
+      break;
+    }
+  }
+  ArrayList* paths = del->deleted_paths;
+  if (!paths)
     return;
   /* Bound the retained list like the keep-set manifest: only MAX_MANIFEST_ENTRIES
      paths are ever transmitted in the terminal STATUS_STATS frame, so recording
@@ -114,6 +144,16 @@ void receiver_record_deleted_path(void* context, const char* rel_path) {
     free(copy);
 }
 
+/* Install the delete observer (and its context) for one commit when the sink
+   carries a stats record or a path list.  Returns NULL when neither is needed,
+   so the delete engines skip the observer entirely. */
+static DeletePathObserver receiver_delete_observer(const ReceiverSink* sink,
+                                                   ReceiverDeleteContext* del) {
+  del->stats = sink ? sink->stats : NULL;
+  del->deleted_paths = sink ? sink->deleted_paths : NULL;
+  return (del->stats || del->deleted_paths) ? receiver_record_deleted_path : NULL;
+}
+
 static bool receiver_process_chunk(Chunk* chunk, const ReceiverSink* sink) {
   if (!chunk || !sink || !sink->store_file)
     return false;
@@ -271,6 +311,7 @@ static bool status_counts_as_progress(Status status) {
   case STATUS_ABORT:
   case STATUS_CHECK_BATCH:
   case STATUS_DIR_TIMES:
+  case STATUS_CLIENT_MSG:
     return false;
   default:
     return true;
@@ -300,7 +341,392 @@ static bool receiver_note_status(const struct timespec* session_start,
 }
 
 int receiver_process(Config* config, int file_descriptor, const ReceiverSink* sink) {
-  return receiver_process_pending(config, file_descriptor, sink, NULL, NULL);
+  return receiver_process_pending_ctx(config, file_descriptor, sink, NULL, NULL, NULL);
+}
+
+int receiver_process_pending(Config* config, int file_descriptor, const ReceiverSink* sink,
+                             DeleteManifest** pending_manifest, DeletePlanSession** pending_plans) {
+  return receiver_process_pending_ctx(config, file_descriptor, sink, pending_manifest,
+                                      pending_plans, NULL);
+}
+
+/* Per-connection state threaded through the status handlers below.  The parked
+   keep-set / per-directory session live here so one teardown helper can release
+   them on every exit path. */
+typedef struct {
+  Config* config;
+  int fd;
+  const ReceiverSink* sink;
+  DeleteManifest** pending_manifest;
+  DeletePlanSession** pending_plans;
+  /* Parked keep-set for the late/commit timing.  Every exit path frees it
+     exactly once; the only exception is the successful FINISHED handoff, which
+     transfers ownership to *pending_manifest (used by the -m receiver). */
+  DeleteManifest* deferred_manifest;
+  /* Per-directory delete session for --delete-during/--delete-delay.  During the
+     loop it applies plans inline (during) or snapshots their extras (delay); on
+     a successful FINISHED it is either committed here or handed to
+     *pending_plans so the -m caller commits after its disk writer drained. */
+  DeletePlanSession* plan_session;
+  /* Observer context for the per-directory delete session, which outlives the
+     frame handler; must stay alive until the session commits.  For a session
+     handed to the caller (pending_plans) this points at a caller-owned
+     long-lived context; otherwise it points at an internal stack context. */
+  ReceiverDeleteContext* delete_ctx;
+  bool early_delete;
+  bool per_dir_delete;
+  bool delete_limit_noted;
+} ReceiverPendingState;
+
+/* Outcome of one frame handler.  NEXT reads the following status frame; FAIL
+   tears the connection down without a peer STATUS_ERROR; ERROR tears it down
+   and (when the sink owns error reporting) emits STATUS_ERROR. */
+typedef enum {
+  RECEIVER_STEP_NEXT,
+  RECEIVER_STEP_FAIL,
+  RECEIVER_STEP_ERROR,
+} ReceiverStep;
+
+static ReceiverStep receiver_handle_keepalive(ReceiverPendingState* state) {
+  if (!send_status(state->fd, STATUS_KEEPALIVE))
+    return RECEIVER_STEP_FAIL;
+  return RECEIVER_STEP_NEXT;
+}
+
+/* rsync --stderr=client: a client diagnostic forwarded over the wire.  Read the
+ * bounded string and log it through the normal destination/level gate.  The
+ * body is peer-controlled text: log_client_message() escapes every
+ * non-printable byte (newlines, CR, ANSI ESC, ...) before writing, so a hostile
+ * client cannot forge log lines or inject terminal control sequences.  A
+ * malformed string (over-long or embedded NUL) is a framing error and tears the
+ * connection down. */
+static ReceiverStep receiver_handle_client_msg(ReceiverPendingState* state) {
+  char* message = receive_str(state->fd);
+  if (!message)
+    return RECEIVER_STEP_FAIL;
+  if (message[0] != '\0')
+    log_client_message(message);
+  free(message);
+  return RECEIVER_STEP_NEXT;
+}
+
+static ReceiverStep receiver_handle_abort(ReceiverPendingState* state) {
+  (void)state;
+  log_message(LOG_LEVEL_INFO, "Received abort from client, cleaning up");
+  return RECEIVER_STEP_FAIL;
+}
+
+static ReceiverStep receiver_handle_check(ReceiverPendingState* state) {
+  bool skipped = false;
+  bool would_transfer = false;
+  File* file = receive_incremental_check_ex(state->fd, state->config, &skipped, &would_transfer);
+  if (state->config->dry_run) {
+    /* Server-contacting --dry-run: the reply has already been sent
+       (STATUS_OK = up to date, STATUS_DRY_RUN_TRANSFER = would transfer) and
+       nothing may be stored.  Both flags false means a genuine protocol
+       error (STATUS_ERROR already sent or sent by receive_error below). */
+    if (!skipped && !would_transfer)
+      return RECEIVER_STEP_ERROR;
+  } else if (!skipped && (!file || !state->sink->store_file(file, state->sink->context))) {
+    return RECEIVER_STEP_ERROR;
+  }
+  return RECEIVER_STEP_NEXT;
+}
+
+static ReceiverStep receiver_handle_chunk(ReceiverPendingState* state) {
+  Chunk* chunk = receive_chunk_data(state->fd, state->config);
+  if (!chunk || !receiver_process_chunk(chunk, state->sink))
+    return RECEIVER_STEP_ERROR;
+  return RECEIVER_STEP_NEXT;
+}
+
+static ReceiverStep receiver_handle_check_batch(ReceiverPendingState* state) {
+  if (!receiver_process_batch(state->config, state->fd))
+    return RECEIVER_STEP_FAIL;
+  return RECEIVER_STEP_NEXT;
+}
+
+/* Probe a destination entry's pre-transfer state for the output-parity
+   dest-info report (protocol 2.30.0).  `wire_path` is the destination-relative
+   path; `incoming_target` is non-NULL only for a symlink probe, in which case
+   the on-disk link target is compared with the target the receiver is about to
+   store (after --munge-links).  The final component is never followed and the
+   parent walk is confined below the receive root.  Returns false only on an
+   allocation/secure-walk failure; a missing entry is reported as existed=false. */
+static bool receiver_probe_dest_state(const Config* config, const char* wire_path,
+                                      const char* incoming_target, OutputDestState* out) {
+  memset(out, 0, sizeof(*out));
+  out->known = true;
+  if (!config || !wire_path || wire_path[0] == '\0')
+    return false;
+  char* full = path_cat(config->receive_root_directory, wire_path);
+  if (!full)
+    return false;
+  char* leaf = NULL;
+  int parent_fd = file_open_secure_parent(full, &leaf, false);
+  free(full);
+  if (parent_fd < 0) {
+    /* A missing/unreachable parent means the entry cannot exist yet. */
+    free(leaf);
+    return true;
+  }
+  struct stat st;
+  if (fstatat(parent_fd, leaf, &st, AT_SYMLINK_NOFOLLOW) == 0) {
+    out->existed = true;
+    out->size = (unsigned long long)st.st_size;
+    out->mtime_sec = (long long)st.st_mtime;
+#ifdef __linux__
+    out->mtime_nsec = st.st_mtim.tv_nsec;
+#endif
+    out->mode = (uint32_t)st.st_mode;
+    out->uid = (int32_t)st.st_uid;
+    out->gid = (int32_t)st.st_gid;
+    if (incoming_target && S_ISLNK(st.st_mode)) {
+      char target_buf[PATH_MAX];
+      ssize_t n = readlinkat(parent_fd, leaf, target_buf, sizeof(target_buf) - 1);
+      if (n >= 0) {
+        target_buf[n] = '\0';
+        char* expected =
+            config->munge_links ? file_symlink_munge(incoming_target) : str_dup(incoming_target);
+        if (expected) {
+          out->target_matches = strcmp(target_buf, expected) == 0;
+          free(expected);
+        }
+      }
+    }
+  }
+  close(parent_fd);
+  free(leaf);
+  return true;
+}
+
+static ReceiverStep receiver_handle_mkdir(ReceiverPendingState* state) {
+  const Config* config = state->config;
+  int fd = state->fd;
+  if (config->report_dest_info) {
+    int probe = 0;
+    if (!receive_int(fd, &probe) || (probe != 0 && probe != 1))
+      return RECEIVER_STEP_FAIL;
+    if (probe) {
+      /* Probe-only frame: report the destination state and create nothing. */
+      char* path = receive_wire_str(fd);
+      if (!path || path[0] == '\0' || (!file_get_trust_sender() && has_path_traversal(path))) {
+        free(path);
+        send_status(fd, STATUS_ERROR);
+        return RECEIVER_STEP_FAIL;
+      }
+      OutputDestState info;
+      bool ok = receiver_probe_dest_state(config, path, NULL, &info);
+      free(path);
+      if (!ok || !send_status(fd, STATUS_DEST_INFO) || !format_dest_state_send(fd, &info))
+        return RECEIVER_STEP_FAIL;
+      return RECEIVER_STEP_NEXT;
+    }
+  }
+  File* dir = file_receive_directory(fd, config);
+  if (!dir)
+    return RECEIVER_STEP_ERROR;
+  if (config->report_dest_info) {
+    OutputDestState info;
+    bool ok = receiver_probe_dest_state(config, file_wire_path(dir), NULL, &info);
+    if (!ok || !send_status(fd, STATUS_DEST_INFO) || !format_dest_state_send(fd, &info)) {
+      file_destroy(dir);
+      return RECEIVER_STEP_FAIL;
+    }
+  }
+  if (!state->sink->store_file(dir, state->sink->context))
+    return RECEIVER_STEP_ERROR;
+  return RECEIVER_STEP_NEXT;
+}
+
+static ReceiverStep receiver_handle_dir_times(const ReceiverPendingState* state) {
+  if (!receiver_process_dir_times(state->fd, state->config, state->sink))
+    return RECEIVER_STEP_ERROR;
+  return RECEIVER_STEP_NEXT;
+}
+
+static ReceiverStep receiver_handle_hardlink(ReceiverPendingState* state) {
+  File* file = file_receive_hardlink(state->fd);
+  if (!file || !state->sink->store_file(file, state->sink->context))
+    return RECEIVER_STEP_ERROR;
+  return RECEIVER_STEP_NEXT;
+}
+
+static ReceiverStep receiver_handle_symlink(ReceiverPendingState* state) {
+  const Config* config = state->config;
+  File* sym = file_receive_symlink(state->fd, config);
+  if (!sym)
+    return RECEIVER_STEP_ERROR;
+  if (config->report_dest_info) {
+    OutputDestState info;
+    bool ok = receiver_probe_dest_state(config, file_wire_path(sym), sym->symlink_target, &info);
+    if (!ok || !send_status(state->fd, STATUS_DEST_INFO) ||
+        !format_dest_state_send(state->fd, &info)) {
+      file_destroy(sym);
+      return RECEIVER_STEP_FAIL;
+    }
+  }
+  if (!state->sink->store_file(sym, state->sink->context))
+    return RECEIVER_STEP_ERROR;
+  return RECEIVER_STEP_NEXT;
+}
+
+static ReceiverStep receiver_handle_special(ReceiverPendingState* state) {
+  File* file = file_receive_special(state->fd);
+  if (!file || !state->sink->store_file(file, state->sink->context))
+    return RECEIVER_STEP_ERROR;
+  return RECEIVER_STEP_NEXT;
+}
+
+static ReceiverStep receiver_handle_manifest(ReceiverPendingState* state) {
+  Config* config = state->config;
+  int fd = state->fd;
+  const ReceiverSink* sink = state->sink;
+  DeleteManifest* manifest = receive_manifest_entries(fd);
+  if (!manifest)
+    return RECEIVER_STEP_FAIL; /* receive_manifest_entries already sent STATUS_ERROR */
+  if (config->dry_run) {
+    /* Server-contacting --dry-run mutates nothing, so a keep-set manifest
+       is consumed and discarded.  The early-delete mode still needs its ACK
+       so a sender blocked on the delete handshake is not left hanging.
+       When would-delete reporting is armed, enumerate (read-only) the
+       destination extras so the terminal STATUS_STATS frame can list them. */
+    if (config->use_delete && sink->would_delete) {
+      size_t count = 0;
+      if (!manifest_would_delete_list(config, manifest, sink->would_delete, &count))
+        log_message(LOG_LEVEL_WARNING, "dry-run: could not enumerate would-delete paths");
+    }
+    delete_manifest_free(manifest);
+    if (state->early_delete && !send_status(fd, STATUS_OK))
+      return RECEIVER_STEP_FAIL;
+    return RECEIVER_STEP_NEXT;
+  }
+  if (state->early_delete) {
+    /* --delete-before: the whole-tree manifest is authoritative the moment
+       it arrives, before any file data.  Delete now and acknowledge so the
+       sender only starts streaming once the deletion committed (or failed).
+       A later transfer failure does not restore these deletions.  A
+       --max-delete-capped commit still succeeds and the transfer proceeds;
+       the terminal success frame reports the cap. */
+    size_t deleted = 0;
+    ReceiverDeleteContext delctx;
+    DeletePathObserver observer = receiver_delete_observer(sink, &delctx);
+    DeleteCommitResult deletion =
+        (config->use_delete || config->delete_missing_args)
+            ? manifest_delete_all_observed(config, manifest, &deleted, observer, &delctx)
+            : DELETE_COMMIT_OK;
+    receiver_tally_deleted(sink, deleted);
+    delete_manifest_free(manifest);
+    if (deletion == DELETE_COMMIT_ERROR) {
+      send_status(fd, STATUS_ERROR);
+      return RECEIVER_STEP_FAIL;
+    }
+    if (deletion == DELETE_COMMIT_LIMIT_REACHED && sink->note_delete_limit)
+      sink->note_delete_limit(sink->context);
+    if (!send_status(fd, STATUS_OK))
+      return RECEIVER_STEP_FAIL;
+  } else if (config->use_delete || config->delete_missing_args) {
+    /* Plain --delete / --delete-after and the --delete-missing-args
+       exact-path deletions: hold the manifest and commit it only after
+       STATUS_FINISHED.  The per-directory modes never send this frame. */
+    if (state->deferred_manifest) {
+      log_message(LOG_LEVEL_ERROR, "Received a second delete manifest");
+      delete_manifest_free(state->deferred_manifest);
+      state->deferred_manifest = NULL;
+      delete_manifest_free(manifest);
+      send_status(fd, STATUS_ERROR);
+      return RECEIVER_STEP_FAIL;
+    }
+    state->deferred_manifest = manifest;
+  } else {
+    delete_manifest_free(manifest);
+  }
+  return RECEIVER_STEP_NEXT;
+}
+
+static ReceiverStep receiver_handle_delete_plan(ReceiverPendingState* state) {
+  Config* config = state->config;
+  int fd = state->fd;
+  const ReceiverSink* sink = state->sink;
+  if (!state->per_dir_delete) {
+    log_message(LOG_LEVEL_ERROR, "Received a per-directory delete plan without a per-dir "
+                                 "delete timing");
+    send_status(fd, STATUS_ERROR);
+    return RECEIVER_STEP_FAIL;
+  }
+  if (!state->plan_session) {
+    state->plan_session = delete_plan_session_create(config);
+    if (state->plan_session && (sink->stats || sink->deleted_paths))
+      delete_plan_session_set_delete_observer(state->plan_session, receiver_record_deleted_path,
+                                              state->delete_ctx);
+  }
+  if (!state->plan_session || delete_plan_session_receive(state->plan_session, config, fd) != 0)
+    return RECEIVER_STEP_FAIL;
+  if (delete_plan_session_limit_reached(state->plan_session) && !state->delete_limit_noted &&
+      sink->note_delete_limit) {
+    sink->note_delete_limit(sink->context);
+    state->delete_limit_noted = true;
+  }
+  return RECEIVER_STEP_NEXT;
+}
+
+static ReceiverStep receiver_handle_file(ReceiverPendingState* state) {
+  File* file = file_receive(state->config, state->fd);
+  if (!file) {
+    log_message(LOG_LEVEL_ERROR, "Failed to receive file");
+    return RECEIVER_STEP_ERROR;
+  }
+  if (!state->sink->store_file(file, state->sink->context))
+    return RECEIVER_STEP_ERROR;
+  return RECEIVER_STEP_NEXT;
+}
+
+/* One dispatch per admitted frame type; STATUS_NEXT (and any other
+   data-bearing status) falls through to the regular file receiver. */
+static ReceiverStep receiver_dispatch_status(ReceiverPendingState* state, Status status) {
+  switch (status) {
+  case STATUS_KEEPALIVE:
+    return receiver_handle_keepalive(state);
+  case STATUS_CLIENT_MSG:
+    return receiver_handle_client_msg(state);
+  case STATUS_ABORT:
+    return receiver_handle_abort(state);
+  case STATUS_CHECK:
+    return receiver_handle_check(state);
+  case STATUS_CHUNK:
+    return receiver_handle_chunk(state);
+  case STATUS_CHECK_BATCH:
+    return receiver_handle_check_batch(state);
+  case STATUS_MKDIR:
+    return receiver_handle_mkdir(state);
+  case STATUS_DIR_TIMES:
+    return receiver_handle_dir_times(state);
+  case STATUS_HARDLINK:
+    return receiver_handle_hardlink(state);
+  case STATUS_SYMLINK:
+    return receiver_handle_symlink(state);
+  case STATUS_SPECIAL:
+    return receiver_handle_special(state);
+  case STATUS_MANIFEST:
+    return receiver_handle_manifest(state);
+  case STATUS_DELETE_PLAN:
+    return receiver_handle_delete_plan(state);
+  default:
+    return receiver_handle_file(state);
+  }
+}
+
+/* Release the parked keep-set / per-directory session exactly once on every
+   failure exit.  Never commit a deletion for a failed stream. */
+static void receiver_drop_pending(ReceiverPendingState* state) {
+  if (state->deferred_manifest) {
+    delete_manifest_free(state->deferred_manifest);
+    state->deferred_manifest = NULL;
+  }
+  if (state->plan_session) {
+    delete_plan_session_destroy(state->plan_session);
+    state->plan_session = NULL;
+  }
 }
 
 /* Runs the whole receive loop.  The delete manifest may legitimately arrive
@@ -312,11 +738,13 @@ int receiver_process(Config* config, int file_descriptor, const ReceiverSink* si
    deletion has committed (or failed); in the late modes the manifest is held
    and the deletion is committed only after the terminal STATUS_FINISHED proves
    the whole transfer succeeded.  A plain --delete defaults to the per-directory
-   delete-during plan mode (no manifest at all).  See
-   receiver_process_pending() for how the -m receiver defers that commit until
-   its disk writer has drained. */
-int receiver_process_pending(Config* config, int file_descriptor, const ReceiverSink* sink,
-                             DeleteManifest** pending_manifest, DeletePlanSession** pending_plans) {
+   delete-during plan mode (no manifest at all).  See the per-frame handlers
+   above for how the -m receiver defers that commit until its disk writer has
+   drained. */
+int receiver_process_pending_ctx(Config* config, int file_descriptor, const ReceiverSink* sink,
+                                 DeleteManifest** pending_manifest,
+                                 DeletePlanSession** pending_plans,
+                                 ReceiverDeleteContext* observer_ctx) {
   Status status;
   if (!receive_status(file_descriptor, &status))
     return -1;
@@ -329,166 +757,37 @@ int receiver_process_pending(Config* config, int file_descriptor, const Receiver
   last_progress = session_start;
   if (!receiver_note_status(&session_start, &last_progress, status, file_descriptor, sink))
     return -1;
-  bool early_delete = config_delete_timing_early(config);
-  bool per_dir_delete = config_delete_timing_per_dir(config);
-  /* Parked keep-set for the late/commit timing.  Every exit path below frees it
-     exactly once; the only exception is the successful FINISHED handoff, which
-     transfers ownership to *pending_manifest (used by the -m receiver). */
-  DeleteManifest* deferred_manifest = NULL;
-  /* Per-directory delete session for --delete-during/--delete-delay.  During the
-     loop it applies plans inline (during) or snapshots their extras (delay); on
-     a successful FINISHED it is either committed here or handed to
-     *pending_plans so the -m caller commits after its disk writer drained. */
-  DeletePlanSession* plan_session = NULL;
-  bool delete_limit_noted = false;
+  /* A per-directory delete session handed to the caller outlives this stack
+     frame, so its observer context must be caller-owned (observer_ctx); only
+     the default inline-commit case may use the stack context. */
+  ReceiverDeleteContext local_ctx;
+  ReceiverDeleteContext* delete_ctx = observer_ctx ? observer_ctx : &local_ctx;
+  delete_ctx->stats = sink ? sink->stats : NULL;
+  delete_ctx->deleted_paths = sink ? sink->deleted_paths : NULL;
+  ReceiverPendingState state = {
+      .config = config,
+      .fd = file_descriptor,
+      .sink = sink,
+      .pending_manifest = pending_manifest,
+      .pending_plans = pending_plans,
+      .deferred_manifest = NULL,
+      .plan_session = NULL,
+      .delete_ctx = delete_ctx,
+      .early_delete = config_delete_timing_early(config),
+      .per_dir_delete = config_delete_timing_per_dir(config),
+      .delete_limit_noted = false,
+  };
+  bool notify_peer = false;
   while (status == STATUS_NEXT || status == STATUS_CHUNK || status == STATUS_CHECK ||
          status == STATUS_KEEPALIVE || status == STATUS_ABORT || status == STATUS_CHECK_BATCH ||
          status == STATUS_MKDIR || status == STATUS_MANIFEST || status == STATUS_HARDLINK ||
          status == STATUS_SYMLINK || status == STATUS_SPECIAL || status == STATUS_DIR_TIMES ||
-         status == STATUS_DELETE_PLAN) {
-    if (status == STATUS_KEEPALIVE) {
-      if (!send_status(file_descriptor, STATUS_KEEPALIVE))
-        goto fail;
-      goto next_status;
-    }
-    if (status == STATUS_ABORT) {
-      log_message(LOG_LEVEL_INFO, "Received abort from client, cleaning up");
+         status == STATUS_DELETE_PLAN || status == STATUS_CLIENT_MSG) {
+    ReceiverStep step = receiver_dispatch_status(&state, status);
+    if (step == RECEIVER_STEP_FAIL)
       goto fail;
-    }
-    if (status == STATUS_CHECK) {
-      bool skipped = false;
-      bool would_transfer = false;
-      File* file = receive_incremental_check_ex(file_descriptor, config, &skipped, &would_transfer);
-      if (config->dry_run) {
-        /* Server-contacting --dry-run: the reply has already been sent
-           (STATUS_OK = up to date, STATUS_DRY_RUN_TRANSFER = would transfer) and
-           nothing may be stored.  Both flags false means a genuine protocol
-           error (STATUS_ERROR already sent or sent by receive_error below). */
-        if (!skipped && !would_transfer)
-          goto receive_error;
-      } else if (!skipped && (!file || !sink->store_file(file, sink->context))) {
-        goto receive_error;
-      }
-    } else if (status == STATUS_CHUNK) {
-      Chunk* chunk = receive_chunk_data(file_descriptor, config);
-      if (!chunk || !receiver_process_chunk(chunk, sink))
-        goto receive_error;
-    } else if (status == STATUS_CHECK_BATCH) {
-      if (!receiver_process_batch(config, file_descriptor))
-        goto fail;
-      goto next_status;
-    } else if (status == STATUS_MKDIR) {
-      File* dir = file_receive_directory(file_descriptor, config);
-      if (!dir || !sink->store_file(dir, sink->context))
-        goto receive_error;
-    } else if (status == STATUS_DIR_TIMES) {
-      if (!receiver_process_dir_times(file_descriptor, config, sink))
-        goto receive_error;
-    } else if (status == STATUS_HARDLINK) {
-      File* file = file_receive_hardlink(file_descriptor);
-      if (!file || !sink->store_file(file, sink->context))
-        goto receive_error;
-    } else if (status == STATUS_SYMLINK) {
-      File* sym = file_receive_symlink(file_descriptor, config);
-      if (!sym || !sink->store_file(sym, sink->context))
-        goto receive_error;
-    } else if (status == STATUS_SPECIAL) {
-      File* file = file_receive_special(file_descriptor);
-      if (!file || !sink->store_file(file, sink->context))
-        goto receive_error;
-    } else if (status == STATUS_MANIFEST) {
-      DeleteManifest* manifest = receive_manifest_entries(file_descriptor);
-      if (!manifest)
-        goto fail; /* receive_manifest_entries already sent STATUS_ERROR */
-      if (config->dry_run) {
-        /* Server-contacting --dry-run mutates nothing, so a keep-set manifest
-           is consumed and discarded.  The early-delete mode still needs its ACK
-           so a sender blocked on the delete handshake is not left hanging.
-           When would-delete reporting is armed, enumerate (read-only) the
-           destination extras so the terminal STATUS_STATS frame can list them. */
-        if (config->use_delete && sink->would_delete) {
-          size_t count = 0;
-          if (!manifest_would_delete_list(config, manifest, sink->would_delete, &count))
-            log_message(LOG_LEVEL_WARNING, "dry-run: could not enumerate would-delete paths");
-        }
-        delete_manifest_free(manifest);
-        if (early_delete && !send_status(file_descriptor, STATUS_OK))
-          goto fail;
-        goto next_status;
-      }
-      if (early_delete) {
-        /* --delete-before: the whole-tree manifest is authoritative the moment
-           it arrives, before any file data.  Delete now and acknowledge so the
-           sender only starts streaming once the deletion committed (or failed).
-           A later transfer failure does not restore these deletions.  A
-           --max-delete-capped commit still succeeds and the transfer proceeds;
-           the terminal success frame reports the cap. */
-        size_t deleted = 0;
-        DeletePathObserver observer =
-            (config->report_deletes && sink->deleted_paths) ? receiver_record_deleted_path : NULL;
-        DeleteCommitResult deletion =
-            (config->use_delete || config->delete_missing_args)
-                ? manifest_delete_all_observed(config, manifest, &deleted, observer,
-                                               (void*)sink->deleted_paths)
-                : DELETE_COMMIT_OK;
-        receiver_tally_deleted(sink, deleted);
-        delete_manifest_free(manifest);
-        if (deletion == DELETE_COMMIT_ERROR) {
-          send_status(file_descriptor, STATUS_ERROR);
-          goto fail;
-        }
-        if (deletion == DELETE_COMMIT_LIMIT_REACHED && sink->note_delete_limit)
-          sink->note_delete_limit(sink->context);
-        if (!send_status(file_descriptor, STATUS_OK))
-          goto fail;
-      } else if (config->use_delete || config->delete_missing_args) {
-        /* Plain --delete / --delete-after and the --delete-missing-args
-           exact-path deletions: hold the manifest and commit it only after
-           STATUS_FINISHED.  The per-directory modes never send this frame. */
-        if (deferred_manifest) {
-          log_message(LOG_LEVEL_ERROR, "Received a second delete manifest");
-          delete_manifest_free(deferred_manifest);
-          deferred_manifest = NULL;
-          delete_manifest_free(manifest);
-          send_status(file_descriptor, STATUS_ERROR);
-          goto fail;
-        }
-        deferred_manifest = manifest;
-      } else {
-        delete_manifest_free(manifest);
-      }
-      goto next_status;
-    } else if (status == STATUS_DELETE_PLAN) {
-      if (!per_dir_delete) {
-        log_message(LOG_LEVEL_ERROR, "Received a per-directory delete plan without a per-dir "
-                                     "delete timing");
-        send_status(file_descriptor, STATUS_ERROR);
-        goto fail;
-      }
-      if (!plan_session) {
-        plan_session = delete_plan_session_create(config);
-        if (plan_session && config->report_deletes && sink->deleted_paths)
-          delete_plan_session_set_delete_observer(plan_session, receiver_record_deleted_path,
-                                                  (void*)sink->deleted_paths);
-      }
-      if (!plan_session || delete_plan_session_receive(plan_session, config, file_descriptor) != 0)
-        goto fail;
-      if (delete_plan_session_limit_reached(plan_session) && !delete_limit_noted &&
-          sink->note_delete_limit) {
-        sink->note_delete_limit(sink->context);
-        delete_limit_noted = true;
-      }
-      goto next_status;
-    } else {
-      File* file = file_receive(config, file_descriptor);
-      if (!file) {
-        log_message(LOG_LEVEL_ERROR, "Failed to receive file");
-        goto receive_error;
-      }
-      if (!sink->store_file(file, sink->context))
-        goto receive_error;
-    }
-  next_status:
+    if (step == RECEIVER_STEP_ERROR)
+      goto receive_error;
     if (!receive_status(file_descriptor, &status))
       goto receive_error;
     if (!receiver_note_status(&session_start, &last_progress, status, file_descriptor, sink))
@@ -498,28 +797,39 @@ int receiver_process_pending(Config* config, int file_descriptor, const Receiver
     log_message(LOG_LEVEL_ERROR, "Did not receive FINISHED Status");
     goto receive_error;
   }
+  /* --delay-updates: publish every staged file BEFORE the deferred delete
+     commit, matching rsync's --delete-after ordering (all updates land first,
+     then extras are removed).  The single-threaded receiver stores files
+     synchronously, so every staged file is complete here.  The -m receiver
+     hands both publication and deletion to its caller via
+     pending_manifest/pending_plans; that caller publishes first, after its disk
+     writer has drained. */
+  bool handoff = state.pending_manifest != NULL || state.pending_plans != NULL;
+  if (!handoff && !config->dry_run && config->delay_updates && config->delay_context) {
+    if (!delay_updates_publish(config->delay_context, config)) {
+      send_status(file_descriptor, STATUS_ERROR);
+      goto fail;
+    }
+  }
   /* Commit-style (late) deletion: every data frame has been received and the
      sender proved the whole tree with STATUS_FINISHED.  The single-threaded
-     receiver stores files synchronously, so everything is on disk here and the
-     deletion can be committed before the --delay-updates publication in
-     send_success (the walker skips the staging dir, so staged files are never
-     treated as extras).  The -m receiver passes `pending_manifest` because its
-     disk writer may still be draining; the caller commits after the writer has
-     joined so no extra file is removed unless the transfer is known to have
-     succeeded. */
-  if (deferred_manifest) {
-    if (pending_manifest) {
-      *pending_manifest = deferred_manifest;
-      deferred_manifest = NULL;
+     receiver stores files synchronously, so everything is on disk here (and a
+     --delay-updates run has already published above).  The -m receiver passes
+     `pending_manifest` because its disk writer may still be draining; the
+     caller commits after the writer has joined so no extra file is removed
+     unless the transfer is known to have succeeded. */
+  if (state.deferred_manifest) {
+    if (state.pending_manifest) {
+      *state.pending_manifest = state.deferred_manifest;
+      state.deferred_manifest = NULL;
     } else {
       size_t deleted = 0;
-      DeletePathObserver observer =
-          (config->report_deletes && sink->deleted_paths) ? receiver_record_deleted_path : NULL;
+      DeletePathObserver observer = receiver_delete_observer(sink, state.delete_ctx);
       DeleteCommitResult deletion = manifest_delete_all_observed(
-          config, deferred_manifest, &deleted, observer, (void*)sink->deleted_paths);
+          config, state.deferred_manifest, &deleted, observer, state.delete_ctx);
       receiver_tally_deleted(sink, deleted);
-      delete_manifest_free(deferred_manifest);
-      deferred_manifest = NULL;
+      delete_manifest_free(state.deferred_manifest);
+      state.deferred_manifest = NULL;
       if (deletion == DELETE_COMMIT_ERROR) {
         send_status(file_descriptor, STATUS_ERROR);
         goto fail;
@@ -533,28 +843,28 @@ int receiver_process_pending(Config* config, int file_descriptor, const Receiver
      nothing yet and applies its decompressed snapshot here.  The -m receiver
      hands the session to its caller instead, which commits after the disk
      writer drained. */
-  if (plan_session) {
-    if (config->report_deletes && sink->deleted_paths)
-      delete_plan_session_set_delete_observer(plan_session, receiver_record_deleted_path,
-                                              (void*)sink->deleted_paths);
-    if (pending_plans) {
-      *pending_plans = plan_session;
-      plan_session = NULL;
+  if (state.plan_session) {
+    if (sink->stats || sink->deleted_paths)
+      delete_plan_session_set_delete_observer(state.plan_session, receiver_record_deleted_path,
+                                              state.delete_ctx);
+    if (state.pending_plans) {
+      *state.pending_plans = state.plan_session;
+      state.plan_session = NULL;
     } else if (config->dry_run) {
       /* Central dry-run no-op: never commit a deletion for a -n run. */
-      delete_plan_session_destroy(plan_session);
-      plan_session = NULL;
+      delete_plan_session_destroy(state.plan_session);
+      state.plan_session = NULL;
     } else {
-      DeleteCommitResult deletion = delete_plan_session_commit(plan_session, config);
-      bool limit = delete_plan_session_limit_reached(plan_session);
-      receiver_tally_deleted(sink, delete_plan_session_deleted(plan_session));
-      delete_plan_session_destroy(plan_session);
-      plan_session = NULL;
+      DeleteCommitResult deletion = delete_plan_session_commit(state.plan_session, config);
+      bool limit = delete_plan_session_limit_reached(state.plan_session);
+      receiver_tally_deleted(sink, delete_plan_session_deleted(state.plan_session));
+      delete_plan_session_destroy(state.plan_session);
+      state.plan_session = NULL;
       if (deletion == DELETE_COMMIT_ERROR) {
         send_status(file_descriptor, STATUS_ERROR);
         goto fail;
       }
-      if (limit && !delete_limit_noted && sink->note_delete_limit)
+      if (limit && !state.delete_limit_noted && sink->note_delete_limit)
         sink->note_delete_limit(sink->context);
     }
   }
@@ -568,26 +878,14 @@ int receiver_process_pending(Config* config, int file_descriptor, const Receiver
   }
   return 0;
 
+receive_error:
+  notify_peer = true;
 fail:
   /* Failure exits that must not (or already did) report a STATUS_ERROR.  The
      parked keep-set/session is dropped: never commit a deletion for a failed
      stream. */
-  if (deferred_manifest) {
-    delete_manifest_free(deferred_manifest);
-    deferred_manifest = NULL;
-  }
-  if (plan_session)
-    delete_plan_session_destroy(plan_session);
-  return -1;
-
-receive_error:
-  if (deferred_manifest) {
-    delete_manifest_free(deferred_manifest);
-    deferred_manifest = NULL;
-  }
-  if (plan_session)
-    delete_plan_session_destroy(plan_session);
-  if (sink->send_error)
+  receiver_drop_pending(&state);
+  if (notify_peer && sink->send_error)
     send_status(file_descriptor, STATUS_ERROR);
   return -1;
 }
@@ -610,6 +908,11 @@ typedef struct {
   ArrayList* would_delete;
   /* --info=del: actually-removed paths collected during the delete commit. */
   ArrayList* deleted_paths;
+  /* Per-run count of entries that failed to materialize without aborting the
+     stream (currently ONLY a --devices mknod EPERM/EACCES).  A nonzero count
+     makes the terminal frame carry a non-OK status so the client exits
+     non-zero, matching rsync's continue-and-exit-partial behavior. */
+  size_t failed_entries;
 } ReceiverSaveContext;
 
 static bool receiver_save_file(File* file, void* context_pointer) {
@@ -633,6 +936,11 @@ static bool receiver_save_file(File* file, void* context_pointer) {
      count as matched data in the end-of-transfer report. */
   if (result != FILE_SAVE_ERROR && file->matched_bytes > 0)
     context->stats.matched_data += file->matched_bytes;
+  /* --devices parity: a device node the receiver could not mknod (EPERM/EACCES)
+     is counted per-run but does not abort the transfer.  The terminal frame
+     turns a nonzero count into a non-OK status so the client exits non-zero. */
+  if (result == FILE_SAVE_FAILED)
+    context->failed_entries++;
   /* Protocol 2.28.0: receiver-observed literal bytes and the created-entry
      breakdown (regular/dir/link/special) for the `--stats` report. */
   if (result == FILE_SAVE_WRITTEN)
@@ -666,9 +974,26 @@ static void receiver_note_delete_limit(void* context_pointer) {
   context->delete_limit_reached = true;
 }
 
+/* Terminal status for a run.  A capped --delete limit wins (rsync exit 25);
+   otherwise any per-entry failure (for example an unprivileged --devices
+   mknod) makes the terminal frame STATUS_PARTIAL so the client exits 23
+   (rsync's "partial transfer due to error") while still removing the sources
+   it successfully transferred under --remove-source-files.  A fatal stream
+   error keeps STATUS_ERROR (a non-23 exit).  A clean run keeps STATUS_OK. */
+static Status receiver_final_status(bool delete_limit_reached, size_t failed_entries) {
+  if (delete_limit_reached)
+    return STATUS_DELETE_LIMIT;
+  return failed_entries > 0 ? STATUS_PARTIAL : STATUS_OK;
+}
+
 static bool receiver_send_success_frame(int fd, void* context_pointer) {
   ReceiverSaveContext* context = context_pointer;
-  Status final_status = context->delete_limit_reached ? STATUS_DELETE_LIMIT : STATUS_OK;
+  if (context->failed_entries > 0)
+    log_message(LOG_LEVEL_WARNING,
+                "%zu entr%s failed to materialize; continuing (partial transfer)",
+                context->failed_entries, context->failed_entries == 1 ? "y" : "ies");
+  Status final_status =
+      receiver_final_status(context->delete_limit_reached, context->failed_entries);
   if (!receiver_send_stats_frame(fd, context->config, &context->stats, context->would_delete,
                                  context->deleted_paths))
     return false;
@@ -676,21 +1001,10 @@ static bool receiver_send_success_frame(int fd, void* context_pointer) {
      nothing to publish and no directory times to stamp. */
   if (context->config->dry_run)
     return receiver_send_final_success(fd, context->config, &context->outcomes, final_status);
-  /* --delay-updates: the whole protocol stream (including manifest/delete
-     handling, which ran inside receiver_process) has succeeded and every
-     staged file was fully written.  Publish them atomically now, before the
-     success/outcome frame tells a --remove-source-files sender it may delete
-     its sources. */
-  if (context->config->delay_updates && context->config->delay_context) {
-    if (!delay_updates_publish(context->config->delay_context, context->config)) {
-      send_status(fd, STATUS_ERROR);
-      return false;
-    }
-  }
-  /* P7 Wave D: every child is now written and the delete / --delay-updates
-     phases have committed, so it is finally safe to stamp directory times.
-     This runs after the deferred deletion because receiver_process commits it
-     before calling this success frame. */
+  /* P7 Wave D: every child is now written and the --delay-updates publication
+     (done in receiver_process before the delete commit) plus the deferred
+     deletion have both committed, so it is finally safe to stamp directory
+     times. */
   dir_metadata_list_apply(&context->dir_times, context->config->receive_root_directory,
                           context->config);
   return receiver_send_final_success(fd, context->config, &context->outcomes, final_status);

src/server/receiver.h

@@ -55,10 +55,20 @@ typedef struct {
 bool receiver_outcomes_append(ReceiverOutcomes* outcomes, unsigned char code);
 void receiver_outcomes_destroy(ReceiverOutcomes* outcomes);
 
-/* DeletePathObserver implementation for --info=del: `context` is an ArrayList*
-   that receives owned copies of every truly-removed destination-relative path.
-   Shared by the single-threaded receiver and the -m pipeline's deferred commit. */
-void receiver_record_deleted_path(void* context, const char* rel_path);
+/* Delete observer context: `deleted_paths` (optional) receives owned copies of
+   every truly-removed destination-relative path for --info=del; `stats`
+   (optional) receives the per-type `Number of deleted files` tallies for
+   --stats.  Both may be NULL, in which case the observer is a no-op. */
+typedef struct {
+  ReceiverStats* stats;
+  struct ArrayList* deleted_paths;
+} ReceiverDeleteContext;
+
+/* DeletePathObserver implementation: records each truly-removed path (when the
+   context carries a path list) and tallies it by type (when it carries a stats
+   record).  Shared by the single-threaded receiver and the -m pipeline's
+   deferred commit. */
+void receiver_record_deleted_path(void* context, const char* rel_path, DeleteEntryType type);
 
 /* Send the terminal success frame.  `final_status` is usually STATUS_OK, or
    STATUS_DELETE_LIMIT when a --max-delete commit was capped. */
@@ -83,6 +93,17 @@ int receiver_process(Config* config, int file_descriptor, const ReceiverSink* si
    for either to keep the default behaviour (delete before the success frame). */
 int receiver_process_pending(Config* config, int file_descriptor, const ReceiverSink* sink,
                              DeleteManifest** pending_manifest, DeletePlanSession** pending_plans);
+/* receiver_process_pending() with an explicit observer context for a
+   per-directory delete session that is handed to the caller via
+   `pending_plans`.  The session outlives this call (the -m pipeline commits it
+   after joining its disk writer), so its observer context must too: pass a
+   long-lived object such as PipelineContextReceiver.delete_ctx.  When
+   `delete_ctx` is NULL an internal stack context is used, which is only safe
+   when the session is committed before returning (the default behaviour). */
+int receiver_process_pending_ctx(Config* config, int file_descriptor, const ReceiverSink* sink,
+                                 DeleteManifest** pending_manifest,
+                                 DeletePlanSession** pending_plans,
+                                 ReceiverDeleteContext* delete_ctx);
 int receiver_receive_files(Config* config, int file_descriptor);
 
 /* ---- Connection time bounds (anti-slowloris) ----

src/server/receiver_pipeline.c

@@ -28,7 +28,10 @@ PipelineContextReceiver* pipeline_context_receiver_create(Config* config, Queue*
   context->max_queue_bytes = 0;
   context->deferred_manifest = NULL;
   context->deferred_plans = NULL;
+  context->delete_ctx.stats = NULL;
+  context->delete_ctx.deleted_paths = NULL;
   context->delete_limit_reached = false;
+  context->failed_entries = 0;
   memset(&context->stats, 0, sizeof(context->stats));
   context->would_delete = NULL;
   context->deleted_paths = NULL;
@@ -204,8 +207,9 @@ int receive_thread(void* pipeline_context) {
                        &context->stats,
                        context->would_delete,
                        context->deleted_paths};
-  if (receiver_process_pending((Config*)config, file_descriptor, &sink, &context->deferred_manifest,
-                               &context->deferred_plans) != 0) {
+  if (receiver_process_pending_ctx((Config*)config, file_descriptor, &sink,
+                                   &context->deferred_manifest, &context->deferred_plans,
+                                   &context->delete_ctx) != 0) {
     receiver_thread_fail(context);
     protocol_session_unbind();
     return thrd_error;
@@ -264,6 +268,13 @@ int write_thread(void* pipeline_context) {
         receiver_stats_note_saved(&context->stats, file, created, created_dirs);
         mtx_unlock(&context->mutex);
       }
+      /* --devices parity: a device node that could not be mknod'ed is counted
+         per-run but does NOT abort the transfer. */
+      if (result == FILE_SAVE_FAILED) {
+        mtx_lock(&context->mutex);
+        context->failed_entries++;
+        mtx_unlock(&context->mutex);
+      }
       if (result == FILE_SAVE_ERROR) {
         file_destroy(file);
         pipeline_context_receiver_note_bytes_released(context, file_bytes);

src/server/receiver_pipeline.h

@@ -46,6 +46,11 @@ typedef struct PipelineContextReceiver {
      committing while the disk writer may still be draining; server.c commits it
      after both threads joined.  NULL for every other timing. */
   DeletePlanSession* deferred_plans;
+  /* Observer context for `deferred_plans`.  It must outlive the receive thread
+     (the session is committed by server.c after both threads join), so it lives
+     here rather than on receiver_process_pending()'s stack; receive_thread
+     installs it on the session. */
+  ReceiverDeleteContext delete_ctx;
   /* Set by server.c when the deferred delete commit hit the --max-delete
      budget; the terminal success frame then carries STATUS_DELETE_LIMIT
      (rsync exit 25) while the transfer itself still succeeds. */
@@ -64,6 +69,11 @@ typedef struct PipelineContextReceiver {
   /* --info=del actually-removed path list, collected by the deferred delete
      commit in server.c and reported in the STATUS_STATS frame. */
   struct ArrayList* deleted_paths;
+  /* Per-run count of entries that failed to materialize without aborting the
+     stream (currently ONLY a --devices mknod EPERM/EACCES).  write_thread
+     increments it under `mutex`; server.c turns a nonzero count into a non-OK
+     terminal status so the client exits non-zero. */
+  size_t failed_entries;
 } PipelineContextReceiver;
 
 PipelineContextReceiver* pipeline_context_receiver_create(Config* config, Queue* queue_receiver,

src/server/server_cli.c

@@ -3,20 +3,12 @@
 #include "credentials.h"
 #include "utils.h"
 #include <limits.h>
-#include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/socket.h>
 
-static void set_error(char* err, size_t err_size, const char* fmt, ...) {
-  if (!err || err_size == 0)
-    return;
-  va_list args;
-  va_start(args, fmt);
-  vsnprintf(err, err_size, fmt, args);
-  va_end(args);
-}
+#define set_error utils_set_error
 
 void server_cli_options_default(ServerCliOptions* opts) {
   if (!opts)

src/shared/array_list.c

@@ -9,7 +9,7 @@
 ArrayList* array_list_create(void (*item_destroyer)(void* item)) {
   ArrayList* list = (ArrayList*)protocol_alloc(sizeof(ArrayList));
   if (list == NULL) {
-    log_perror("ERROR: Could not allocate memory for array list struct");
+    log_message(LOG_LEVEL_ERROR, "%s", "ERROR: Could not allocate memory for array list struct");
     return NULL;
   }
 
@@ -47,7 +47,7 @@ static bool array_list_extend(ArrayList* array_list) {
     new_capacity = INITIAL_ARRAY_SIZE;
   void* new_items = protocol_realloc(array_list->items, new_capacity * sizeof(void*));
   if (new_items == NULL) {
-    log_perror("ERROR: Could not reallocate memory for array list items");
+    log_message(LOG_LEVEL_ERROR, "%s", "ERROR: Could not reallocate memory for array list items");
     return false;
   }
   array_list->items = new_items;
@@ -73,7 +73,7 @@ void** array_list_to_array(const ArrayList* array_list) {
   }
   void** array = protocol_alloc(array_list->size * sizeof(void*));
   if (array == NULL) {
-    log_perror("Could not malloc space for array from array list!");
+    log_message(LOG_LEVEL_ERROR, "%s", "Could not malloc space for array from array list!");
     return NULL;
   }
   memcpy(array, array_list->items, array_list->size * sizeof(void*));

src/shared/chunk.c

@@ -17,8 +17,9 @@
 #include "protocol.h"
 #include "utils.h"
 
-/* Maximum individual file data size within a chunk (64 MB) */
-#define MAX_FILE_DATA_SIZE (64ULL * 1024 * 1024)
+/* Maximum individual file data size within a chunk (64 MB).  Distinct from the
+ * receiver's whole-file MAX_FILE_DATA_SIZE (256 MB) in file_receive.c. */
+#define MAX_CHUNK_FILE_DATA_SIZE (64ULL * 1024 * 1024)
 #define MAX_FILES_PER_CHUNK 65536U
 
 /* Reserve `charge` against `session`'s connection budget.  This mirrors the
@@ -382,9 +383,9 @@ Chunk* chunk_deserialize(Data* data, bool use_metadata) {
     }
 
     // Reject individual file data larger than the maximum allowed size.
-    if (file_data_size > MAX_FILE_DATA_SIZE) {
+    if (file_data_size > MAX_CHUNK_FILE_DATA_SIZE) {
       log_message(LOG_LEVEL_ERROR, "File data size %zu exceeds maximum %llu", file_data_size,
-                  (unsigned long long)MAX_FILE_DATA_SIZE);
+                  (unsigned long long)MAX_CHUNK_FILE_DATA_SIZE);
       goto error;
     }
 

src/shared/compression.c

@@ -3,6 +3,7 @@
 #include "log.h"
 #include "protocol.h"
 #include "utils.h"
+#include <errno.h>
 #include <limits.h>
 #include <lz4.h>
 #include <stdatomic.h>
@@ -16,7 +17,14 @@
 #include <zstd.h>
 
 #define INITIAL_DECOMPRESS_BUF_SIZE (1024 * 1024)
-#define MAX_DECOMPRESSED_SIZE (100ULL * 1024 * 1024) /* 100 MB hard ceiling */
+
+/* Hard ceiling for a single decompression.  The sender compresses whole files
+ * up to the protocol's whole-file receive bound, so the decompressor must
+ * accept payloads that large; referencing the protocol constant keeps the two
+ * bounds from drifting apart (they previously did: a 100 MB ceiling rejected
+ * 100-256 MB files).  This remains a real bomb guard -- every allocation in the
+ * paths below is clamped to it -- so it must not exceed the protocol bound. */
+#define MAX_DECOMPRESSED_SIZE MAX_RECEIVE_WHOLE_FILE_SIZE
 
 /* rsync 3.4.1's built-in skip-compress suffix list (the `--skip-compress`
  * defaults, in the man page's order).  rsync stores it as space-separated
@@ -637,8 +645,7 @@ static Data* zstd_decompress(Data* compressed_data, size_t maximum_size) {
     }
     if (ret > 0 && output.pos == output.size) {
       if (buf_size >= hard_limit || buf_size > SIZE_MAX / 2) {
-        log_message(LOG_LEVEL_ERROR, "Decompressed data exceeds %llu bytes",
-                    (unsigned long long)MAX_DECOMPRESSED_SIZE);
+        log_message(LOG_LEVEL_ERROR, "Decompressed data exceeds %llu bytes", hard_limit);
         data_destroy(uncompressed_data);
         uncompressed_data = NULL;
         goto cleanup;
@@ -710,3 +717,379 @@ Data* data_decompress_limited(Data* compressed_data, size_t maximum_size) {
 Data* data_decompress(Data* compressed_data) {
   return data_decompress_limited(compressed_data, MAX_DECOMPRESSED_SIZE);
 }
+
+/* ---- streaming decompression ---- */
+
+#define STREAM_DECOMPRESS_OUT_CHUNK (256 * 1024)
+
+struct CompressionStreamDecompressor {
+  CompressionAlgo algo;
+  unsigned long long expected_out;
+  unsigned long long total;
+  int out_fd;
+  unsigned char* out_buf;
+  ZSTD_DCtx* dctx;
+  z_stream zs;
+  bool zs_initialized;
+  bool failed;
+};
+
+static bool stream_write_all(int fd, const void* data, size_t size) {
+  const unsigned char* p = data;
+  size_t done = 0;
+  while (done < size) {
+    ssize_t n = write(fd, p + done, size - done);
+    if (n < 0 && errno == EINTR)
+      continue;
+    if (n <= 0)
+      return false;
+    done += (size_t)n;
+  }
+  return true;
+}
+
+CompressionStreamDecompressor*
+compression_stream_decompressor_create(CompressionAlgo algo, unsigned long long expected_out) {
+  CompressionStreamDecompressor* d = calloc(1, sizeof(*d));
+  if (!d)
+    return NULL;
+  d->algo = algo;
+  d->expected_out = expected_out;
+  d->out_fd = -1;
+  d->out_buf = malloc(STREAM_DECOMPRESS_OUT_CHUNK);
+  if (!d->out_buf) {
+    free(d);
+    return NULL;
+  }
+  if (algo == COMPRESSION_ALGO_ZSTD) {
+    d->dctx = ZSTD_createDCtx();
+    if (!d->dctx) {
+      free(d->out_buf);
+      free(d);
+      return NULL;
+    }
+  } else if (algo == COMPRESSION_ALGO_ZLIB || algo == COMPRESSION_ALGO_ZLIBX) {
+    if (inflateInit(&d->zs) != Z_OK) {
+      free(d->out_buf);
+      free(d);
+      return NULL;
+    }
+    d->zs_initialized = true;
+  } else if (algo != COMPRESSION_ALGO_NONE) {
+    /* lz4's block format cannot be decompressed incrementally. */
+    free(d->out_buf);
+    free(d);
+    return NULL;
+  }
+  return d;
+}
+
+static bool stream_emit(CompressionStreamDecompressor* d, const void* buf, size_t len) {
+  if (len == 0)
+    return true;
+  if (d->expected_out != 0 && (d->total > d->expected_out || len > d->expected_out - d->total)) {
+    d->failed = true;
+    return false;
+  }
+  if (!stream_write_all(d->out_fd, buf, len)) {
+    d->failed = true;
+    return false;
+  }
+  d->total += len;
+  return true;
+}
+
+static bool stream_feed_none(CompressionStreamDecompressor* d, const void* in, size_t in_len,
+                             bool* done) {
+  if (!stream_emit(d, in, in_len))
+    return false;
+  /* NONE has no end marker; the caller knows the frame length. */
+  *done = true;
+  return true;
+}
+
+static bool stream_feed_zstd(CompressionStreamDecompressor* d, const void* in, size_t in_len,
+                             bool* done) {
+  ZSTD_inBuffer input = {in, in_len, 0};
+  while (input.pos < input.size) {
+    ZSTD_outBuffer output = {d->out_buf, STREAM_DECOMPRESS_OUT_CHUNK, 0};
+    size_t ret = ZSTD_decompressStream(d->dctx, &output, &input);
+    if (ZSTD_isError(ret)) {
+      d->failed = true;
+      return false;
+    }
+    if (!stream_emit(d, d->out_buf, output.pos))
+      return false;
+    if (ret == 0) {
+      *done = true;
+      /* Trailing bytes after a complete frame are malformed; stop consuming. */
+      if (input.pos < input.size) {
+        d->failed = true;
+        return false;
+      }
+      return true;
+    }
+  }
+  return true;
+}
+
+static bool stream_feed_zlib(CompressionStreamDecompressor* d, const void* in, size_t in_len,
+                             bool* done) {
+  d->zs.next_in = (Bytef*)in;
+  d->zs.avail_in = (uInt)in_len;
+  while (d->zs.avail_in > 0) {
+    d->zs.next_out = d->out_buf;
+    d->zs.avail_out = STREAM_DECOMPRESS_OUT_CHUNK;
+    int rc = inflate(&d->zs, Z_NO_FLUSH);
+    if (rc != Z_OK && rc != Z_STREAM_END && rc != Z_BUF_ERROR) {
+      d->failed = true;
+      return false;
+    }
+    size_t produced = STREAM_DECOMPRESS_OUT_CHUNK - d->zs.avail_out;
+    if (!stream_emit(d, d->out_buf, produced))
+      return false;
+    if (rc == Z_STREAM_END) {
+      *done = true;
+      return d->zs.avail_in == 0;
+    }
+    if (rc == Z_BUF_ERROR && produced == 0) {
+      /* Need more input. */
+      break;
+    }
+  }
+  return true;
+}
+
+bool compression_stream_decompressor_feed(CompressionStreamDecompressor* d, const void* in,
+                                          size_t in_len, int out_fd, bool* done) {
+  if (!d || d->failed)
+    return false;
+  d->out_fd = out_fd;
+  if (done)
+    *done = false;
+  switch (d->algo) {
+  case COMPRESSION_ALGO_NONE:
+    return stream_feed_none(d, in, in_len, done);
+  case COMPRESSION_ALGO_ZSTD:
+    return stream_feed_zstd(d, in, in_len, done);
+  case COMPRESSION_ALGO_ZLIB:
+  case COMPRESSION_ALGO_ZLIBX:
+    return stream_feed_zlib(d, in, in_len, done);
+  case COMPRESSION_ALGO_LZ4:
+    break;
+  }
+  d->failed = true;
+  return false;
+}
+
+unsigned long long compression_stream_decompressor_total(const CompressionStreamDecompressor* d) {
+  return d ? d->total : 0;
+}
+
+void compression_stream_decompressor_destroy(CompressionStreamDecompressor* d) {
+  if (!d)
+    return;
+  if (d->dctx)
+    ZSTD_freeDCtx(d->dctx);
+  if (d->zs_initialized)
+    inflateEnd(&d->zs);
+  free(d->out_buf);
+  free(d);
+}
+
+/* ---- streaming compression ---- */
+
+struct CompressionStreamCompressor {
+  CompressionAlgo algo;
+  int level;
+  ZSTD_CCtx* cctx;
+  z_stream zs;
+  bool zs_initialized;
+  unsigned char* out_buf;
+  bool failed;
+};
+
+bool compression_stream_compress_supported(CompressionAlgo algo) {
+  return algo == COMPRESSION_ALGO_ZSTD || algo == COMPRESSION_ALGO_ZLIB ||
+         algo == COMPRESSION_ALGO_ZLIBX;
+}
+
+CompressionStreamCompressor* compression_stream_compressor_create(CompressionAlgo algo, int level,
+                                                                  int threads) {
+  (void)threads;
+  if (!compression_algo_valid((int)algo) || algo == COMPRESSION_ALGO_LZ4)
+    return NULL;
+  CompressionStreamCompressor* c = calloc(1, sizeof(*c));
+  if (!c)
+    return NULL;
+  c->algo = algo;
+  c->level = level;
+  c->out_buf = malloc(STREAM_DECOMPRESS_OUT_CHUNK);
+  if (!c->out_buf) {
+    free(c);
+    return NULL;
+  }
+  if (algo == COMPRESSION_ALGO_ZSTD) {
+    c->cctx = ZSTD_createCCtx();
+    if (!c->cctx) {
+      free(c->out_buf);
+      free(c);
+      return NULL;
+    }
+  } else if (algo == COMPRESSION_ALGO_ZLIB || algo == COMPRESSION_ALGO_ZLIBX) {
+    if (deflateInit(&c->zs, level < 1 ? Z_DEFAULT_COMPRESSION : level) != Z_OK) {
+      free(c->out_buf);
+      free(c);
+      return NULL;
+    }
+    c->zs_initialized = true;
+  }
+  return c;
+}
+
+bool compression_stream_compressor_begin(CompressionStreamCompressor* c,
+                                         unsigned long long raw_size, int out_fd) {
+  if (!c || c->failed)
+    return false;
+  unsigned char hdr[1 + 4];
+  size_t hdr_len = 1;
+  hdr[0] = (unsigned char)c->algo;
+  if (c->algo == COMPRESSION_ALGO_ZLIB || c->algo == COMPRESSION_ALGO_ZLIBX) {
+    uint32_t size32 = raw_size > UINT32_MAX ? UINT32_MAX : (uint32_t)raw_size;
+    for (int i = 0; i < 4; i++)
+      hdr[1 + i] = (uint8_t)((size32 >> (8 * i)) & 0xff);
+    hdr_len = 5;
+  }
+  if (c->algo == COMPRESSION_ALGO_ZSTD) {
+    /* Pledge the source size and force the frame content-size field so the
+       receiver can decide whether to stream from the frame header alone. */
+    if (ZSTD_isError(ZSTD_CCtx_setPledgedSrcSize(c->cctx, raw_size)) ||
+        ZSTD_isError(ZSTD_CCtx_setParameter(c->cctx, ZSTD_c_compressionLevel, c->level)) ||
+        ZSTD_isError(ZSTD_CCtx_setParameter(c->cctx, ZSTD_c_contentSizeFlag, 1))) {
+      c->failed = true;
+      return false;
+    }
+    if (ZSTD_isError(ZSTD_CCtx_setParameter(c->cctx, ZSTD_c_checksumFlag, 0))) {
+      c->failed = true;
+      return false;
+    }
+  }
+  if (!stream_write_all(out_fd, hdr, hdr_len)) {
+    c->failed = true;
+    return false;
+  }
+  return true;
+}
+
+static bool stream_compress_zlib(CompressionStreamCompressor* c, const void* in, size_t in_len,
+                                 int out_fd, int flush) {
+  c->zs.next_in = (Bytef*)in;
+  c->zs.avail_in = (uInt)in_len;
+  do {
+    c->zs.next_out = c->out_buf;
+    c->zs.avail_out = STREAM_DECOMPRESS_OUT_CHUNK;
+    int rc = deflate(&c->zs, flush);
+    if (rc != Z_OK && rc != Z_STREAM_END && rc != Z_BUF_ERROR) {
+      c->failed = true;
+      return false;
+    }
+    size_t produced = STREAM_DECOMPRESS_OUT_CHUNK - c->zs.avail_out;
+    if (!stream_write_all(out_fd, c->out_buf, produced)) {
+      c->failed = true;
+      return false;
+    }
+    if (rc == Z_STREAM_END)
+      return true;
+    if (rc == Z_BUF_ERROR && produced == 0)
+      break;
+  } while (c->zs.avail_in > 0 || flush == Z_FINISH);
+  return true;
+}
+
+bool compression_stream_compressor_feed(CompressionStreamCompressor* c, const void* in,
+                                        size_t in_len, int out_fd) {
+  if (!c || c->failed)
+    return false;
+  if (c->algo == COMPRESSION_ALGO_NONE)
+    return stream_write_all(out_fd, in, in_len);
+  if (c->algo == COMPRESSION_ALGO_ZSTD) {
+    ZSTD_inBuffer input = {in, in_len, 0};
+    while (input.pos < input.size) {
+      ZSTD_outBuffer output = {c->out_buf, STREAM_DECOMPRESS_OUT_CHUNK, 0};
+      size_t ret = ZSTD_compressStream2(c->cctx, &output, &input, ZSTD_e_continue);
+      if (ZSTD_isError(ret)) {
+        c->failed = true;
+        return false;
+      }
+      if (!stream_write_all(out_fd, c->out_buf, output.pos)) {
+        c->failed = true;
+        return false;
+      }
+      if (output.pos == 0 && input.pos < input.size)
+        break; /* avoid spinning; zstd buffers the rest internally */
+    }
+    return true;
+  }
+  return stream_compress_zlib(c, in, in_len, out_fd, Z_NO_FLUSH);
+}
+
+bool compression_stream_compressor_finish(CompressionStreamCompressor* c, int out_fd) {
+  if (!c || c->failed)
+    return false;
+  if (c->algo == COMPRESSION_ALGO_NONE)
+    return true;
+  if (c->algo == COMPRESSION_ALGO_ZSTD) {
+    size_t ret;
+    do {
+      ZSTD_inBuffer input = {NULL, 0, 0};
+      ZSTD_outBuffer output = {c->out_buf, STREAM_DECOMPRESS_OUT_CHUNK, 0};
+      ret = ZSTD_compressStream2(c->cctx, &output, &input, ZSTD_e_end);
+      if (ZSTD_isError(ret)) {
+        c->failed = true;
+        return false;
+      }
+      if (!stream_write_all(out_fd, c->out_buf, output.pos)) {
+        c->failed = true;
+        return false;
+      }
+    } while (ret > 0);
+    return true;
+  }
+  return stream_compress_zlib(c, NULL, 0, out_fd, Z_FINISH);
+}
+
+void compression_stream_compressor_destroy(CompressionStreamCompressor* c) {
+  if (!c)
+    return;
+  if (c->cctx)
+    ZSTD_freeCCtx(c->cctx);
+  if (c->zs_initialized)
+    deflateEnd(&c->zs);
+  free(c->out_buf);
+  free(c);
+}
+
+unsigned long long compression_peek_frame_content_size(const void* buf, size_t len) {
+  if (!buf || len < 1)
+    return 0;
+  const uint8_t* p = buf;
+  uint8_t codec = p[0];
+  if (!compression_algo_valid(codec))
+    return 0;
+  if (codec == (uint8_t)COMPRESSION_ALGO_NONE)
+    return len - 1;
+  if (codec == (uint8_t)COMPRESSION_ALGO_ZSTD) {
+    if (len < 2)
+      return 0;
+    unsigned long long size = ZSTD_getFrameContentSize(p + 1, len - 1);
+    if (size == ZSTD_CONTENTSIZE_ERROR || size == ZSTD_CONTENTSIZE_UNKNOWN)
+      return 0;
+    return size;
+  }
+  if (len < 1 + LZ4_SIZE_PREFIX_LEN)
+    return 0;
+  uint32_t raw = 0;
+  for (int i = 0; i < LZ4_SIZE_PREFIX_LEN; i++)
+    raw |= (uint32_t)p[1 + i] << (8 * i);
+  return raw;
+}

src/shared/compression.h

@@ -81,6 +81,54 @@ Data* data_compress_with_threads(Data* data_to_compress, int compression_level,
 Data* data_decompress(Data* compressed_data);
 bool compression_should_skip_with_suffixes(const char* path, char* const* suffixes, int count);
 
+/* Streaming decompression for a payload too large to hold in memory.  The
+ * caller consumes the frame's leading codec byte (and, for lz4/zlib/zlibx, the
+ * 4-byte little-endian raw-size prefix) and then feeds the remaining frame
+ * bytes in bounded chunks; decompressed output is written straight to `out_fd`
+ * so neither the compressed nor the decompressed image is ever materialized.
+ * Only zstd (the default), zlib/zlibx and none support streaming; lz4's block
+ * format is one-shot, so its stream decompressor reports failure and the caller
+ * falls back (the whole-buffer path keeps its existing bound). */
+typedef struct CompressionStreamDecompressor CompressionStreamDecompressor;
+
+CompressionStreamDecompressor*
+compression_stream_decompressor_create(CompressionAlgo algo, unsigned long long expected_out);
+/* Feed one chunk.  Returns false on a malformed frame, an I/O error, or when the
+ * total output would exceed `expected_out` (when non-zero).  *done is set once
+ * the frame end has been reached. */
+bool compression_stream_decompressor_feed(CompressionStreamDecompressor* d, const void* in,
+                                          size_t in_len, int out_fd, bool* done);
+unsigned long long compression_stream_decompressor_total(const CompressionStreamDecompressor* d);
+void compression_stream_decompressor_destroy(CompressionStreamDecompressor* d);
+
+/* Peek the logical (decompressed) size from the leading bytes of a compressed
+ * frame (codec byte + header), returning 0 when it cannot be determined from
+ * the supplied prefix.  Used to decide whether a frame must take the streaming
+ * path before its body is read. */
+unsigned long long compression_peek_frame_content_size(const void* buf, size_t len);
+
+/* Streaming compression (sender side).  Compresses a source in bounded chunks
+ * into `out_fd` as one self-describing frame (codec byte, the lz4/zlib raw-size
+ * prefix, then the codec stream), so a whole file can be compressed without
+ * materializing it in memory.  zstd/zlib/zlibx/none are supported; lz4's block
+ * format is one-shot, so its create() returns NULL and the caller keeps the
+ * buffered path.  `raw_size` is the known source length (used for the zlib
+ * prefix and, for zstd, the frame content-size field). */
+typedef struct CompressionStreamCompressor CompressionStreamCompressor;
+
+/* True when `algo` can be stream-compressed (zstd/zlib/zlibx; lz4's block format
+ * is one-shot).  Used by the sender to decide whether an over-threshold source
+ * may stay unloaded. */
+bool compression_stream_compress_supported(CompressionAlgo algo);
+CompressionStreamCompressor* compression_stream_compressor_create(CompressionAlgo algo, int level,
+                                                                  int threads);
+bool compression_stream_compressor_begin(CompressionStreamCompressor* c,
+                                         unsigned long long raw_size, int out_fd);
+bool compression_stream_compressor_feed(CompressionStreamCompressor* c, const void* in,
+                                        size_t in_len, int out_fd);
+bool compression_stream_compressor_finish(CompressionStreamCompressor* c, int out_fd);
+void compression_stream_compressor_destroy(CompressionStreamCompressor* c);
+
 /* Release the calling thread's cached zstd contexts (compressor, decompressor
  * and scratch buffer).  The cache is thread-local and is also released
  * automatically when a worker thread exits (via a C11 tss destructor) and for

src/shared/config.c

@@ -20,9 +20,9 @@
 
 static void config_set_defaults(Config* config) {
   config->scanner_threads = 0;
-  config->metadata_explicitly_disabled = false;
-  config->preserve_perms_explicit_off = false;
-  config->preserve_times_explicit_off = false;
+  config->cli.preserve_perms_explicit_off = false;
+  config->cli.preserve_times_explicit_off = false;
+  config->cli.metadata_explicitly_disabled = false;
   config->show_progress = false;
   config->compression_threads = 0;
   config->ssh_port = 22;
@@ -44,8 +44,8 @@ static void config_set_defaults(Config* config) {
   config->tls_ca = NULL;
   config->server_host = str_dup("127.0.0.1");
   config->server_port = 8080;
-  config->server_port_set = false;
-  config->server_host_set = false;
+  config->cli.server_port_set = false;
+  config->cli.server_host_set = false;
   /* rsync defaults: --timeout=0 (I/O timeouts disabled) and --contimeout=60.
    * A value of 0 disables the client's own deadline on both the socket layer
    * (tcp_set_timeouts) and the protocol layer
@@ -68,10 +68,10 @@ static void config_set_defaults(Config* config) {
   config->human_readable = false;
   config->ignore_errors = false;
   config->ignore_missing_args = false;
-  config->checksum_transfer_algo = CHECKSUM_ALGO_DEFAULT;
-  config->cli_exit_code = 0;
-  config->compression_level_set = false;
-  config->checksum_choice_set = false;
+  config->cli.checksum_transfer_algo = CHECKSUM_ALGO_DEFAULT;
+  config->cli.cli_exit_code = 0;
+  config->cli.compression_level_set = false;
+  config->cli.checksum_choice_set = false;
   config->filters = NULL;
   config->files_from = NULL;
   config->files_from_set = NULL;
@@ -79,13 +79,12 @@ static void config_set_defaults(Config* config) {
   config->cvs_exclude = false;
   config->per_dir_filter = false;
   config->per_dir_filter_count = 0;
-  config->one_file_system = false;
+  config->one_file_system = 0;
   config->no_implied_dirs = false;
   config->dirs = false;
   config->rsh_command = NULL;
   config->blocking_io = false;
   config->outbuf = OUTBUF_BLOCK;
-  config->old_args = false;
   config->remote_options = NULL;
   config->remote_option_count = 0;
   config->address = NULL;
@@ -101,7 +100,7 @@ static void config_set_defaults(Config* config) {
   config->trust_sender = false;
   config->stop_after_mins = 0;
   config->stop_at = 0;
-  config->stop_at_set = false;
+  config->cli.stop_at_set = false;
   config->write_batch = NULL;
   config->only_write_batch = NULL;
   config->read_batch = NULL;
@@ -230,6 +229,13 @@ Config* config_create(void) {
   if (!config)
     return NULL;
   config_set_defaults(config);
+  /* config_set_defaults() dups the default server host; a failure there leaves
+   * server_host NULL and would crash later consumers, so fail the whole create
+   * (every caller already handles a NULL return). */
+  if (!config->server_host) {
+    config_delete(config);
+    return NULL;
+  }
   return config;
 }
 
@@ -335,7 +341,8 @@ bool config_derived_use_metadata(const Config* config) {
       config->chown_uid_set || config->chown_gid_set || config->usermap_count > 0 ||
       config->groupmap_count > 0 || config->update)
     return true;
-  return (config->use_incremental || config->use_delta) && !config->metadata_explicitly_disabled;
+  return (config->use_incremental || config->use_delta) &&
+         !config->cli.metadata_explicitly_disabled;
 }
 
 bool config_has_basis(const Config* config) {
@@ -686,9 +693,15 @@ int config_parse_ssh_dest(Config* config) {
     return daemon_dest_parse_error("invalid remote destination user@host (must not be empty or "
                                    "start with '-')",
                                    dest);
-  config->transport = TRANSPORT_SSH;
-  config->ssh_destination = str_dup(dest);
+  char* ssh_destination = str_dup(dest);
   char* path = str_dup(colon + 1);
+  if (!ssh_destination || !path) {
+    free(ssh_destination);
+    free(path);
+    return daemon_dest_parse_error("out of memory parsing remote destination", dest);
+  }
+  config->transport = TRANSPORT_SSH;
+  config->ssh_destination = ssh_destination;
   free(config->receive_root_directory);
   config->receive_root_directory = path;
   return 0;
@@ -1052,6 +1065,16 @@ static bool send_protect_entries(int fd, const Config* c) {
     log_message(LOG_LEVEL_ERROR, "invalid filter rule: %s", err);
     return false;
   }
+  /* The receiver rejects any block with more than MAX_FILTER_RULES entries as a
+   * protocol error; refuse to emit such a frame at all.  filter_base_build()
+   * can expand the client rule set (cvs-exclude, merge files), so this is the
+   * authoritative bound, not config->filters->size. */
+  if (rules->count < 0 || rules->count > MAX_FILTER_RULES) {
+    log_message(LOG_LEVEL_ERROR, "too many filter rules: %d (maximum %d)", rules->count,
+                MAX_FILTER_RULES);
+    filter_rule_list_free(rules);
+    return false;
+  }
   bool ok = send_int(fd, rules->count);
   for (int i = 0; ok && i < rules->count; i++) {
     const FilterRule* r = rules->items[i];

src/shared/config.h

@@ -83,7 +83,7 @@ typedef struct {
 typedef enum SuperMode { SUPER_MODE_AUTO = 0, SUPER_MODE_ON = 1, SUPER_MODE_OFF = 2 } SuperMode;
 
 /* ===========================================================================
- * Config wire-field table (single source of truth for protocol 2.28.0).
+ * Config wire-field table (single source of truth for protocol 2.30.0).
  *
  * Every field below crosses the wire.  The table is the ONLY place a
  * serialized field is named: config.h expands CONFIG_WIRE_FIELDS() to declare
@@ -342,22 +342,60 @@ typedef enum SuperMode { SUPER_MODE_AUTO = 0, SUPER_MODE_ON = 1, SUPER_MODE_OFF
   CONFIG_WIRE_CODEC_FIELDS(X)                                                                      \
   CONFIG_WIRE_PROTECT_FIELDS(X)
 
+/* Client-only, CLI-parse bookkeeping (never serialized).  These members exist
+ * only so the client command-line parser can record HOW an option was
+ * specified (explicitly set, explicitly negated, or a parser-requested exit
+ * code); no other module and no wire peer ever needs them.  Grouping them in
+ * one nested member keeps the public Config free of client-CLI-only state. */
+typedef struct {
+  /* Set when the user explicitly turned an attribute off with --no-perms /
+   * --no-times (long or short form).  --incremental/--delta historically
+   * auto-enabled mode and mtime preservation; these flags let
+   * cli_finalize_config restore that behavior while still honoring the
+   * explicit per-attribute negation.  A later -p/-t re-enables the attribute
+   * directly, so the flag only prevents the incremental/delta implication,
+   * never a POSITIVE request. */
+  bool preserve_perms_explicit_off;
+  bool preserve_times_explicit_off;
+  /* Set by --no-preserve, the explicit opt-out of the whole preservation
+   * bundle, so the --incremental/--delta auto-preserve implication stays off. */
+  bool metadata_explicitly_disabled;
+  /* True when --server-port/--port was explicitly given.  --dry-run uses it to
+   * decide whether a real server handshake was requested, so a plain local
+   * destination (no explicit port) keeps the existing client-side dry-run
+   * behavior instead of dialing the default 127.0.0.1:8080. */
+  bool server_port_set;
+  /* True when --server-host was explicitly given, and distinct from the
+   * "127.0.0.1" default: --dry-run uses it to route an explicit remote target
+   * to the server so it reports receiver state exactly like a real run,
+   * instead of silently running the client-side manifest. */
+  bool server_host_set;
+  /* Codec-negotiation CLI state.  The effective pre-transfer checksum is
+   * Config->checksum_algo (serialized); checksum_transfer_algo is the rsync
+   * "transfer" half of a two-name --checksum-choice form (validated and used
+   * only to mirror rsync's whole-file forcing, since FastSync's per-block
+   * strong hash is fixed).  cli_exit_code carries a parser-requested process
+   * exit status (rsync uses 4 for an unsupported checksum/compress algorithm)
+   * so main() can mirror it. */
+  int checksum_transfer_algo;
+  int cli_exit_code;
+  /* "The user explicitly chose" bits.  They let the per-codec default level /
+   * checksum list be applied only when the corresponding rsync option was
+   * omitted (an explicit --compress-level / --checksum-choice always wins). */
+  bool compression_level_set;
+  bool checksum_choice_set;
+  /* True when --stop-at was given. */
+  bool stop_at_set;
+} ConfigCliParse;
+
 typedef struct Config {
   /* -j/--threads=N: number of parallel scanner worker threads for the -m
    * pipeline.  0 (the default, also set by bare -j/--threads) means "use the
    * scanner's built-in default" (4).  CLIENT-ONLY: it is a local scheduling
    * concern and is NEVER serialized into the wire config frame. */
   int scanner_threads;
-  bool metadata_explicitly_disabled;
-  /* CLIENT-ONLY (never serialized; not in CONFIG_WIRE_FIELDS).  Set when the
-   * user explicitly turned an attribute off with --no-perms / --no-times (long
-   * or short form).  --incremental/--delta historically auto-enabled mode and
-   * mtime preservation; these flags let cli_finalize_config restore that
-   * behavior while still honoring the explicit per-attribute negation.  A
-   * later -p/-t re-enables the attribute directly, so the flag only prevents
-   * the incremental/delta implication, never a POSITIVE request. */
-  bool preserve_perms_explicit_off;
-  bool preserve_times_explicit_off;
+  /* Client-only CLI-parse bookkeeping (never serialized).  See ConfigCliParse. */
+  ConfigCliParse cli;
   bool show_progress;
   int compression_threads;
   int ssh_port;
@@ -378,18 +416,6 @@ typedef struct Config {
   bool use_tls;
   char* server_host;
   int server_port;
-  /* True when --server-port/--port was explicitly given.  CLIENT-ONLY (never
-   * serialized): --dry-run uses it to decide whether a real server handshake
-   * was requested, so a plain local destination (no explicit port) keeps the
-   * existing client-side dry-run behavior instead of dialing the default
-   * 127.0.0.1:8080. */
-  bool server_port_set;
-  /* True when --server-host was explicitly given.  CLIENT-ONLY (never
-   * serialized), and distinct from the "127.0.0.1" default: --dry-run uses it
-   * to route an explicit remote target to the server so it reports receiver
-   * state exactly like a real run, instead of silently running the client-side
-   * manifest. */
-  bool server_host_set;
   char* tls_cert;
   char* tls_key;
   char* tls_ca;
@@ -435,22 +461,6 @@ typedef struct Config {
    * enters the keep-set.  Implied by --delete-missing-args. */
   bool ignore_missing_args;
 
-  /* Codec-negotiation CLI state (all client-only, never serialized).  The
-   * effective pre-transfer checksum is Config->checksum_algo (serialized);
-   * checksum_transfer_algo is the rsync "transfer" half of a two-name
-   * --checksum-choice form (validated and used only to mirror rsync's
-   * whole-file forcing, since FastSync's per-block strong hash is fixed).
-   * cli_exit_code carries a parser-requested process exit status (rsync uses 4
-   * for an unsupported checksum/compress algorithm) so main() can mirror it. */
-  int checksum_transfer_algo;
-  int cli_exit_code;
-  /* Client-only "the user explicitly chose" bits.  They let the per-codec
-   * default level / checksum list be applied only when the corresponding
-   * rsync option was omitted (an explicit --compress-level / --checksum-choice
-   * always wins).  Never serialized. */
-  bool compression_level_set;
-  bool checksum_choice_set;
-
   // Issue #129: Advanced file selection. These fields are CLIENT-ONLY: they are
   // never serialized to the wire (the receiver must not learn them).
   ArrayList* filters;   /* --filter=RULE rule strings, in order */
@@ -463,7 +473,9 @@ typedef struct Config {
    * /.rsync-filter' (the .rsync-filter files themselves are transferred); a
    * repeated -F adds --filter='- .rsync-filter' so they are excluded too. */
   int per_dir_filter_count;
-  bool one_file_system; /* -x/--one-file-system: do not cross filesystem boundaries */
+  int one_file_system; /* -x/--one-file-system: do not cross filesystem boundaries.
+                          Repeated -x (rsync's -xx) drops the mount-point
+                          directory entirely instead of recreating it empty. */
   /* --no-implied-dirs: client-only.  With -R, do not transfer the source
    * metadata of the parent directories implied by a listed path; an unlisted
    * implied parent is still created (with default attributes) so the listed
@@ -484,7 +496,6 @@ typedef struct Config {
   /* --outbuf mode (OutbufMode): stdout/stderr buffering.  Client-only launch
    * concern: NEVER crosses the wire. */
   int outbuf;
-  bool old_args;
   /* --remote-option=OPT (Phase 5, long form only): one or more extra command-line
    * options to append to the REMOTE server invocation over SSH.  CLIENT-ONLY:
    * they are composed into the remote command line by ssh_build_remote_command()
@@ -554,7 +565,6 @@ typedef struct Config {
    * process and are NEVER serialized into the config frame. */
   int stop_after_mins; /* --stop-after=MINS minutes; 0 when unset */
   time_t stop_at;      /* --stop-at=... absolute wall-clock deadline */
-  bool stop_at_set;    /* true when --stop-at was given */
 
   /* Client-only residual-batch paths.  A residual batch is a self-contained
    * single-file record of the whole source tree (full file images using the
@@ -725,11 +735,13 @@ typedef struct Config {
    * --copy-as) imply it. */
   /* fake_super */
   /* --fake-super: receiver-only.  When set, each written file additionally gets
-   * a reserved user.fastsync.stat xattr recording the RESOLVED uid/gid (the
+   * rsync's reserved user.rsync.%stat xattr recording the RESOLVED uid/gid (the
    * source's own when no ownership request is active, else the --chown/--usermap
-   * result) plus mode/mtime so a later privileged restore could re-apply them.
-   * It NEVER real-chowns: the point is to record the source ownership on an
-   * unprivileged receiver.  Crosses the wire. */
+   * result) plus the full mode and rdev, in rsync 3.4.1's grammar, so the tree is
+   * interoperable and a later privileged restore could re-apply them.  mtime is
+   * carried by the file's own timestamp, exactly as rsync does it.  It NEVER
+   * real-chowns: the point is to record the source ownership on an unprivileged
+   * receiver.  Crosses the wire. */
   /* module */
   /* Daemon module selection (Wave A, protocol 2.15.0).  Client-composed from a
    * host::module/path destination; NULL or "" means "no module" (the ordinary
@@ -1059,7 +1071,33 @@ typedef struct Config {
  * filter rules so the receiver can protect DESTINATION-ONLY entries from
  * --delete with `protect`/`risk` rules (rsync parity).  The block appends after
  * compression_algo; see CONFIG_WIRE_PROTECT_FIELDS. */
-#define PROTOCOL_VERSION "2.28.0"
+/* (10) Symlink xattrs/ACLs (protocol 2.29.0): the config-frame LAYOUT is
+ * unchanged (the derived use_xattrs bit already crosses the wire), but the
+ * STATUS_SYMLINK frame BODY grows a trailing bounded xattr block when -X/-A is
+ * negotiated -- exactly the block STATUS_MKDIR, STATUS_DIR_TIMES and regular
+ * files already carry.  The sender captures the symlink's OWN xattrs with
+ * llistxattr/lgetxattr (so it can never attach the REFERENT's attributes to the
+ * link) and the receiver re-applies them to the link itself with lsetxattr on a
+ * confined /proc/self/fd/<parent>/<leaf> path (there is no *at xattr syscall and
+ * fsetxattr cannot target a symlink).  A 2.28 peer that does not consume the new
+ * trailing block would desynchronize after every symlink, so the protocol
+ * version must bump; the strict same-version handshake (config_receive rejects a
+ * mismatched version before parsing anything else) keeps a 2.29 client and a
+ * 2.28 server from ever reaching that state. */
+/* (11) Client-message channel + partial exit (protocol 2.30.0): the
+ * config-frame LAYOUT is unchanged (no new config field), but the frame stream
+ * gains two statuses.  STATUS_CLIENT_MSG (client->server) carries a bounded,
+ * length-prefixed diagnostic string so a client running with --stderr=client
+ * (rsync's --no-msgs2stderr spelling) can forward its own diagnostics to the
+ * server's stderr.  STATUS_PARTIAL (receiver->client) is the terminal status
+ * sent instead of STATUS_OK when a per-entry receiver failure (e.g. an
+ * unprivileged --devices mknod) did not abort the stream; the sender exits 23
+ * (rsync's partial transfer) and still removes successfully transferred
+ * --remove-source-files sources.  A 2.29 peer that does not know these status
+ * values would reject them as an unknown status and tear the connection down,
+ * so the protocol version must bump; the strict same-version handshake keeps a
+ * 2.30 client and a 2.29 server from ever reaching that state. */
+#define PROTOCOL_VERSION "2.30.0"
 #define DEFAULT_CHUNK_SIZE (10 * 1024 * 1024)
 /* Upper bound on total basis-dir entries (rsync caps --link-dest at 20). */
 #define MAX_BASIS_DIRS 64

src/shared/credentials.c

@@ -8,12 +8,13 @@
 #include <openssl/evp.h>
 #include <openssl/params.h>
 #include <openssl/rand.h>
-#include <stdarg.h>
+#include <poll.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/stat.h>
+#include <time.h>
 #include <unistd.h>
 
 /* One store entry: a username and its salted PBKDF2 verifier.  The plaintext
@@ -58,19 +59,37 @@ struct CredentialStore {
 static const uint8_t k_dummy_stored_key[CREDENTIAL_KEY_LEN] = {0};
 static const uint8_t k_dummy_server_key[CREDENTIAL_KEY_LEN] = {0};
 
-static void set_error(char* err, size_t err_size, const char* fmt, ...) {
-  if (!err || err_size == 0)
-    return;
-  va_list args;
-  va_start(args, fmt);
-  vsnprintf(err, err_size, fmt, args);
-  va_end(args);
-}
+#define set_error utils_set_error
 
 static bool is_comment_char(char c) {
   return c == '#' || c == ';';
 }
 
+/* True for a literal fd-backed store path: exactly "/dev/fd/<digits>" or
+ * "/proc/self/fd/<digits>", with no trailing component and no "..".  These name
+ * the calling process's own open descriptors (e.g. a bash process substitution
+ * `<(...)`, which passes /dev/fd/N), and both prefixes are symlinks by
+ * construction. */
+static bool is_fd_backed_path(const char* path) {
+  static const char* const prefixes[] = {"/dev/fd/", "/proc/self/fd/"};
+  if (!path)
+    return false;
+  for (size_t i = 0; i < sizeof(prefixes) / sizeof(prefixes[0]); i++) {
+    const char* prefix = prefixes[i];
+    size_t prefix_len = strlen(prefix);
+    if (strncmp(path, prefix, prefix_len) != 0)
+      continue;
+    const char* digits = path + prefix_len;
+    if (*digits < '0' || *digits > '9')
+      return false;
+    const char* p = digits;
+    while (*p >= '0' && *p <= '9')
+      p++;
+    return *p == '\0';
+  }
+  return false;
+}
+
 /* Open a --password-file / --early-input after verifying the EXACT inode we
  * will read: it must be owned by the effective user and grant no group/other
  * permission bit (so 0600 and stricter modes such as 0400 are accepted),
@@ -80,12 +99,31 @@ static bool is_comment_char(char c) {
  * path and then fstat the resulting fd (rather than stat()ing the path first
  * and reopening it), so the permission decision is made on the same inode that
  * is read and cannot be raced by swapping the path between check and open.
- * The path may be a process-substitution pipe (`<(...)` -> /dev/fd/N), so
- * regular files and FIFOs are accepted when the ownership/mode checks pass.
+ * O_NOFOLLOW refuses a symlinked path outright (ELOOP fails closed) instead of
+ * following it before the owner/mode gate can run.  The one exception is a
+ * literal fd-backed path (/dev/fd/N or /proc/self/fd/N, see
+ * is_fd_backed_path): those entries are symlinks to the CALLING process's own
+ * descriptors, so following them is not the untrusted-symlink hazard
+ * O_NOFOLLOW guards against, and requiring O_NOFOLLOW would break the
+ * documented process-substitution/FIFO usage.  For them only, O_NOFOLLOW is
+ * omitted; the same fstat owner/mode gate still applies to the resolved inode.
+ * O_NONBLOCK keeps the OPEN itself from
+ * blocking forever on a writer-less FIFO (a blocking O_RDONLY open would wait
+ * for a writer).  The fd is left nonblocking for FIFOs so a read never blocks
+ * either; the read loop (secret_read_line) absorbs the resulting EAGAIN by
+ * waiting, under a bounded deadline, for the writer -- this is what makes a
+ * slow process substitution (`--password-file <(sleep 1; ...)`) work while a
+ * writer-less FIFO still fails after the deadline instead of hanging.  Only
+ * regular files and FIFOs pass the ownership/mode checks; O_NONBLOCK is
+ * cleared for regular files, where it is a no-op anyway and no EAGAIN can
+ * occur, so their stdio read path is byte-for-byte unchanged.
  *
  * Returns a FILE* the caller must fclose, or NULL with `err` filled. */
 static FILE* secret_file_open(const char* path, char* err, size_t err_size) {
-  int fd = open(path, O_RDONLY | O_CLOEXEC);
+  int flags = O_RDONLY | O_NONBLOCK | O_CLOEXEC;
+  if (!is_fd_backed_path(path))
+    flags |= O_NOFOLLOW;
+  int fd = open(path, flags);
   if (fd < 0) {
     set_error(err, err_size, "cannot open secret file '%s': %s", path, strerror(errno));
     return NULL;
@@ -105,6 +143,15 @@ static FILE* secret_file_open(const char* path, char* err, size_t err_size) {
     close(fd);
     return NULL;
   }
+  /* O_NONBLOCK is only meaningful for the FIFO allowance.  Restore blocking
+   * mode on a regular file so its read path is exactly as before; a no-op on
+   * most systems, but explicit.  Failures here are ignored: O_NONBLOCK on a
+   * regular file does not affect reads either way. */
+  if (S_ISREG(st.st_mode)) {
+    int status_flags = fcntl(fd, F_GETFL);
+    if (status_flags >= 0)
+      (void)fcntl(fd, F_SETFL, status_flags & ~O_NONBLOCK);
+  }
   FILE* fp = fdopen(fd, "r");
   if (!fp) {
     set_error(err, err_size, "cannot read secret file '%s': %s", path, strerror(errno));
@@ -114,6 +161,123 @@ static FILE* secret_file_open(const char* path, char* err, size_t err_size) {
   return fp;
 }
 
+/* Overall bound on how long the reader waits for a process-substitution/FIFO
+ * writer to produce data before giving up.  It must comfortably exceed a
+ * producer's startup delay (e.g. `--password-file <(sleep 1; ...)`) while still
+ * bounding a writer-less FIFO, so a stray or hostile FIFO cannot stall the
+ * daemon or client indefinitely. */
+#define CREDENTIAL_FIFO_READ_TIMEOUT_MS 3000
+
+/* Monotonic milliseconds, used only for the read deadline (wall-clock changes
+ * must not extend or shorten the wait). */
+static int64_t credential_monotonic_ms(void) {
+  struct timespec ts;
+  if (clock_gettime(CLOCK_MONOTONIC, &ts) != 0)
+    return 0;
+  return (int64_t)ts.tv_sec * 1000 + (int64_t)(ts.tv_nsec / 1000000);
+}
+
+/* Wait until `fd` is readable or the deadline passes.  Returns true when it is
+ * readable, false on timeout or a poll error (err filled).  EINTR is retried
+ * against the same deadline, so signals cannot extend the wait. */
+static bool credential_wait_readable(int fd, int64_t deadline, const char* label, const char* path,
+                                     char* err, size_t err_size) {
+  for (;;) {
+    int64_t remaining = deadline - credential_monotonic_ms();
+    if (remaining <= 0)
+      break;
+    if (remaining > INT_MAX)
+      remaining = INT_MAX;
+    struct pollfd pfd = {.fd = fd, .events = POLLIN, .revents = 0};
+    int rc = poll(&pfd, 1, (int)remaining);
+    if (rc > 0)
+      return true;
+    if (rc == 0)
+      break;
+    if (errno != EINTR) {
+      set_error(err, err_size, "error waiting for %s '%s': %s", label, path, strerror(errno));
+      return false;
+    }
+  }
+  set_error(err, err_size, "timed out after %d ms waiting for %s '%s'",
+            CREDENTIAL_FIFO_READ_TIMEOUT_MS, label, path);
+  return false;
+}
+
+typedef enum {
+  SECRET_READ_LINE,
+  SECRET_READ_EOF,
+  SECRET_READ_ERROR,
+} SecretReadResult;
+
+/* Read one complete line from `fp` into `line` (capacity `cap`), including the
+ * trailing newline when present and always NUL-terminating.  `*out_len`
+ * receives strlen(line).
+ *
+ * A regular file is read exactly as before: secret_file_open leaves it
+ * blocking, so fgets never sees EAGAIN.  A FIFO stays nonblocking, so fgets
+ * returns NULL (or a partial line) with EAGAIN while the writer is still
+ * starting up; instead of treating that as a fatal error the loop clearerr()s
+ * and polls for readability against one overall deadline.  The `used`
+ * accumulator reassembles a line that arrived in several write()s into a single
+ * line, so a split write is not misparsed as two entries.
+ *
+ * Returns SECRET_READ_LINE, SECRET_READ_EOF, or SECRET_READ_ERROR (err filled)
+ * on timeout or a genuine read error. */
+static SecretReadResult secret_read_line(char* line, size_t cap, FILE* fp, const char* label,
+                                         const char* path, size_t* out_len, char* err,
+                                         size_t err_size) {
+  int fd = fileno(fp);
+  int64_t deadline = credential_monotonic_ms() + CREDENTIAL_FIFO_READ_TIMEOUT_MS;
+  size_t used = 0;
+  line[0] = '\0';
+  for (;;) {
+    errno = 0;
+    if (fgets(line + used, (int)(cap - used), fp)) {
+      used += strlen(line + used);
+      if (used > 0 && line[used - 1] == '\n') {
+        *out_len = used;
+        return SECRET_READ_LINE;
+      }
+      if (feof(fp)) {
+        *out_len = used; /* final unterminated line */
+        return SECRET_READ_LINE;
+      }
+      /* No newline and not EOF.  A full buffer is the caller's over-long-line
+       * case; otherwise the line is only partially available (a nonblocking
+       * FIFO under a slow writer), so any genuine read error fails and anything
+       * else waits for the rest. */
+      if (used >= cap - 1) {
+        *out_len = used;
+        return SECRET_READ_LINE;
+      }
+      int e = ferror(fp) ? errno : 0;
+      if (e != 0 && e != EAGAIN && e != EWOULDBLOCK) {
+        set_error(err, err_size, "error reading %s '%s': %s", label, path, strerror(e));
+        return SECRET_READ_ERROR;
+      }
+      clearerr(fp);
+      if (!credential_wait_readable(fd, deadline, label, path, err, err_size))
+        return SECRET_READ_ERROR;
+      continue;
+    }
+    /* fgets returned NULL: EOF, a not-yet-readable FIFO, or a real error. */
+    if (feof(fp)) {
+      *out_len = used;
+      return used > 0 ? SECRET_READ_LINE : SECRET_READ_EOF;
+    }
+    if (errno == EAGAIN || errno == EWOULDBLOCK) {
+      clearerr(fp);
+      if (!credential_wait_readable(fd, deadline, label, path, err, err_size))
+        return SECRET_READ_ERROR;
+      continue;
+    }
+    set_error(err, err_size, "error reading %s '%s': %s", label, path,
+              errno != 0 ? strerror(errno) : "read failed");
+    return SECRET_READ_ERROR;
+  }
+}
+
 /* Trim leading/trailing ASCII space and tab in place; returns the new start. */
 static char* trim_space(char* s) {
   while (*s == ' ' || *s == '\t')
@@ -509,9 +673,17 @@ static CredentialStore* load_store_file(const char* path, char* err, size_t err_
   char line[CREDENTIAL_MAX_LINE + 2];
   bool ok = true;
 
-  while (fgets(line, sizeof(line), fp)) {
+  for (;;) {
+    size_t len = 0;
+    SecretReadResult rr =
+        secret_read_line(line, sizeof(line), fp, "credential file", path, &len, err, err_size);
+    if (rr == SECRET_READ_EOF)
+      break;
+    if (rr == SECRET_READ_ERROR) {
+      ok = false;
+      break;
+    }
     line_no++;
-    size_t len = strlen(line);
     if (len == CREDENTIAL_MAX_LINE + 1 && line[len - 1] != '\n' && !feof(fp)) {
       set_error(err, err_size, "credential file '%s' line %d exceeds the %d-byte limit", path,
                 line_no, CREDENTIAL_MAX_LINE);
@@ -1148,9 +1320,17 @@ int credentials_hash_file(const char* path, uint32_t iters, FILE* out, char* err
   int line_no = 0;
   int result = 0;
   char line[CREDENTIAL_MAX_LINE + 2];
-  while (fgets(line, sizeof(line), fp)) {
+  for (;;) {
+    size_t len = 0;
+    SecretReadResult rr =
+        secret_read_line(line, sizeof(line), fp, "plaintext file", path, &len, err, err_size);
+    if (rr == SECRET_READ_EOF)
+      break;
+    if (rr == SECRET_READ_ERROR) {
+      result = -1;
+      break;
+    }
     line_no++;
-    size_t len = strlen(line);
     if (len == CREDENTIAL_MAX_LINE + 1 && line[len - 1] != '\n' && !feof(fp)) {
       set_error(err, err_size, "plaintext file '%s' line %d exceeds the %d-byte limit", path,
                 line_no, CREDENTIAL_MAX_LINE);
@@ -1228,9 +1408,15 @@ int credentials_read_secret_file(const char* path, char** user_out, char** passw
   char line[CREDENTIAL_MAX_LINE + 2];
   int result = -1;
 
-  while (fgets(line, sizeof(line), fp)) {
+  for (;;) {
+    size_t len = 0;
+    SecretReadResult rr =
+        secret_read_line(line, sizeof(line), fp, "password file", path, &len, err, err_size);
+    if (rr == SECRET_READ_EOF)
+      break;
+    if (rr == SECRET_READ_ERROR)
+      goto done;
     line_no++;
-    size_t len = strlen(line);
     if (len == CREDENTIAL_MAX_LINE + 1 && line[len - 1] != '\n' && !feof(fp)) {
       set_error(err, err_size, "password file '%s' line %d exceeds the %d-byte limit", path,
                 line_no, CREDENTIAL_MAX_LINE);

src/shared/daemon_conf.c

@@ -1,12 +1,12 @@
 #include "daemon_conf.h"
 #include "credentials.h"
+#include "log.h"
 #include "utils.h"
 #include <arpa/inet.h>
 #include <ctype.h>
 #include <errno.h>
 #include <limits.h>
 #include <netinet/in.h>
-#include <stdarg.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -17,14 +17,7 @@
 /* helpers                                                             */
 /* ------------------------------------------------------------------ */
 
-static void set_error(char* err, size_t err_size, const char* fmt, ...) {
-  if (!err || err_size == 0)
-    return;
-  va_list args;
-  va_start(args, fmt);
-  vsnprintf(err, err_size, fmt, args);
-  va_end(args);
-}
+#define set_error utils_set_error
 
 /* Trim leading and trailing ASCII space/tab in place; returns the new start. */
 static char* trim_ws(char* s) {
@@ -41,6 +34,158 @@ static bool key_equals(const char* key, const char* canonical) {
   return strcasecmp(key, canonical) == 0;
 }
 
+/* True when `key` matches one of the NUL-terminated names in `list`. */
+static bool key_in_list(const char* key, const char* const* list, size_t count) {
+  for (size_t i = 0; i < count; i++) {
+    if (strcasecmp(key, list[i]) == 0)
+      return true;
+  }
+  return false;
+}
+
+/* rsync 3.4.1 rsyncd.conf GLOBAL keys accepted in the pre-module section that
+ * have no FastSync equivalent.  They are recognized and documented as inert:
+ * accepting a real rsync config must not fail on a logging/process key, but a
+ * silently-reinterpreted key is never invented.  `pidfile`/`logfile` are the
+ * compact --dparam spellings rsync documents.  The same list is used by the
+ * `--dparam` dispatch (apply_global_key), so there is a single impl. */
+static const char* const kRsyncInertGlobalKeys[] = {
+    "pid file",
+    "pidfile",
+    "log file",
+    "logfile",
+    "socket options",
+    "sockopts",
+    "listen backlog",
+    "syslog facility",
+    "syslog tag",
+    "log format",
+    "use chroot",
+    "uid",
+    "gid",
+    "timeout",
+    "max verbosity",
+    "min verbosity",
+    "lock file",
+    "transfer logging",
+    "strict modes",
+    "reverse lookup",
+    "forward lookup",
+    "ignore errors",
+    "ignore nonreadable",
+    "dont compress",
+};
+
+/* rsync 3.4.1 rsyncd.conf MODULE keys accepted in a [module] section that have
+ * no FastSync equivalent (accepted-and-documented inert).  Keys with a FastSync
+ * meaning (`path`, `read only`, `write only`, `auth users`, `max connections`,
+ * `hosts allow`/`hosts deny`, `client owner`) are handled by apply_module_key
+ * before this list is consulted.  Security-relevant keys (`exclude`, `filter`,
+ * `secrets file`, `refuse options`, ...) are inert, so a daemon-side filter or
+ * rsync secrets file is NOT enforced: each is loudly warned about at load time
+ * (see kRsyncUnenforcedModuleSecurityKeys) and documented as a residual in
+ * RSYNC_COMPAT.md. */
+static const char* const kRsyncInertModuleKeys[] = {
+    "comment",
+    "use chroot",
+    "daemon chroot",
+    "uid",
+    "gid",
+    "daemon uid",
+    "daemon gid",
+    "exclude",
+    "include",
+    "exclude from",
+    "include from",
+    "filter",
+    "max verbosity",
+    "min verbosity",
+    "lock file",
+    "transfer logging",
+    "log file",
+    "log format",
+    "syslog facility",
+    "syslog tag",
+    "timeout",
+    "secrets file",
+    "auth digest",
+    "strict modes",
+    "numeric ids",
+    "fake super",
+    "munge symlinks",
+    "list",
+    "dont compress",
+    "charset",
+    "refuse options",
+    "incoming chmod",
+    "outgoing chmod",
+    "open noatime",
+    "max size",
+    "min size",
+    "temp dir",
+    "pre-xfer exec",
+    "post-xfer exec",
+    "name converter",
+    "proxy protocol",
+    "proxy protocol hosts",
+    "reverse lookup",
+    "forward lookup",
+    "ignore errors",
+    "ignore nonreadable",
+};
+
+/* Subset of the inert rsync keys whose intent is access control (data
+ * visibility, credential source, transfer hooks, daemon privilege), plus the
+ * global keys that shape the daemon's privilege/identity.  These load for
+ * rsync-config compatibility, but because FastSync ignores them an operator
+ * migrating a hardened rsyncd.conf must not believe the restriction applies.
+ * The loader emits one LOG_LEVEL_WARNING per occurrence naming the key (and the
+ * module, for a module key).  `write only` is deliberately absent: it is mapped
+ * onto writability instead (FastSync is push-only, so a write-only module is
+ * simply writable). */
+static const char* const kRsyncUnenforcedModuleSecurityKeys[] = {
+    "secrets file",
+    "auth digest",
+    "refuse options",
+    "exclude",
+    "include",
+    "exclude from",
+    "include from",
+    "filter",
+    "max size",
+    "min size",
+    "pre-xfer exec",
+    "post-xfer exec",
+    "incoming chmod",
+    "outgoing chmod",
+    "name converter",
+    "use chroot",
+    "daemon chroot",
+    "uid",
+    "gid",
+    "daemon uid",
+    "daemon gid",
+    "munge symlinks",
+    "fake super",
+    "strict modes",
+    "proxy protocol",
+    "proxy protocol hosts",
+};
+
+static const char* const kRsyncUnenforcedGlobalSecurityKeys[] = {
+    "use chroot",
+    "uid",
+    "gid",
+    "strict modes",
+};
+
+#define kRsyncInertGlobalCount (sizeof(kRsyncInertGlobalKeys) / sizeof(kRsyncInertGlobalKeys[0]))
+#define kRsyncInertModuleCount (sizeof(kRsyncInertModuleKeys) / sizeof(kRsyncInertModuleKeys[0]))
+#define kRsyncUnenforcedModuleSecurityCount                                                        \
+  (sizeof(kRsyncUnenforcedModuleSecurityKeys) / sizeof(kRsyncUnenforcedModuleSecurityKeys[0]))
+#define kRsyncUnenforcedGlobalSecurityCount                                                        \
+  (sizeof(kRsyncUnenforcedGlobalSecurityKeys) / sizeof(kRsyncUnenforcedGlobalSecurityKeys[0]))
+
 static bool parse_bool_value(const char* value, bool* out) {
   if (strcasecmp(value, "yes") == 0 || strcasecmp(value, "true") == 0 || strcmp(value, "1") == 0) {
     *out = true;
@@ -258,6 +403,10 @@ DaemonConf* daemon_conf_create(void) {
   if (!conf)
     return NULL;
   conf->global.port = DAEMON_CONF_DEFAULT_PORT;
+  /* rsync modules are READ-ONLY unless `read only = no` (or `write only = yes`)
+   * is set, so FastSync must default the same way: a migrated rsyncd.conf that
+   * omits `read only` is served read-only, never writable. */
+  conf->global.read_only_default = true;
   conf->global.max_connections = DAEMON_CONF_DEFAULT_MAX_CONNECTIONS;
   conf->global.auth_failure_delay_ms = DAEMON_CONF_DEFAULT_AUTH_FAILURE_DELAY_MS;
   conf->global.max_connections_per_host = DAEMON_CONF_DEFAULT_MAX_CONNECTIONS_PER_HOST;
@@ -332,7 +481,7 @@ static bool apply_global_key(DaemonConf* conf, char* key, const char* value, boo
                              char* err, size_t err_size) {
   if (key_equals(key, "port"))
     return store_port(&conf->global.port, value, err, err_size);
-  if (key_equals(key, "motd file")) {
+  if (key_equals(key, "motd file") || key_equals(key, "motdfile")) {
     if (!store_string(&conf->global.motd_file, value)) {
       set_error(err, err_size, "out of memory parsing 'motd file'");
       return false;
@@ -346,6 +495,25 @@ static bool apply_global_key(DaemonConf* conf, char* key, const char* value, boo
     }
     return true;
   }
+  /* rsync allows the `read only` module key in the global section as the
+   * default for modules defined after it.  Map it to that default (a later
+   * --dparam re-applies it to modules that did not set their own value) so a
+   * global `read only = yes` cannot be silently dropped into a writable
+   * default. */
+  if (key_equals(key, "read only")) {
+    bool parsed;
+    if (!parse_bool_value(value, &parsed)) {
+      set_error(err, err_size, "global 'read only' must be yes/no (or true/false/1/0), got '%s'",
+                value);
+      return false;
+    }
+    conf->global.read_only_default = parsed;
+    for (int i = 0; i < conf->module_count; i++) {
+      if (!conf->modules[i].read_only_explicit)
+        conf->modules[i].read_only = parsed;
+    }
+    return true;
+  }
   if (key_equals(key, "max connections"))
     return store_max_connections(&conf->global.max_connections, value, NULL, err, err_size);
   if (key_equals(key, "max connections per host"))
@@ -368,6 +536,15 @@ static bool apply_global_key(DaemonConf* conf, char* key, const char* value, boo
   if (key_equals(key, "hosts deny"))
     return store_host_list(&conf->global.hosts_deny, &conf->global.hosts_deny_count, value,
                            "hosts deny", NULL, replace_hosts, err, err_size);
+  /* A recognized rsync global key with no FastSync equivalent loads inert. */
+  if (key_in_list(key, kRsyncInertGlobalKeys, kRsyncInertGlobalCount)) {
+    if (key_in_list(key, kRsyncUnenforcedGlobalSecurityKeys, kRsyncUnenforcedGlobalSecurityCount))
+      log_message(LOG_LEVEL_WARNING,
+                  "daemon config: global key '%s' is accepted for rsync compatibility but is NOT "
+                  "enforced by FastSync; the restriction it expresses will not be applied",
+                  key);
+    return true;
+  }
   set_error(err, err_size, "unknown global key '%s'", key);
   return false;
 }
@@ -396,6 +573,26 @@ static bool apply_module_key(DaemonModule* module, char* key, char* value, char*
       return false;
     }
     module->read_only = parsed;
+    module->read_only_explicit = true;
+    return true;
+  }
+  /* rsync's `write only = yes` makes the module client-writable.  FastSync has
+   * no read/pull path, so mapping it to writability is the exact
+   * security-relevant effect; set `read_only_explicit` so a global default
+   * cannot override the module's explicit choice.  `write only = no` is the
+   * rsync default and leaves the module's read-only state untouched. */
+  if (key_equals(key, "write only")) {
+    bool parsed;
+    if (!parse_bool_value(value, &parsed)) {
+      set_error(err, err_size,
+                "module '%s': 'write only' must be yes/no (or true/false/1/0), got '%s'",
+                module->name, value);
+      return false;
+    }
+    if (parsed) {
+      module->read_only = false;
+      module->read_only_explicit = true;
+    }
     return true;
   }
   if (key_equals(key, "client owner")) {
@@ -465,6 +662,15 @@ static bool apply_module_key(DaemonModule* module, char* key, char* value, char*
   if (key_equals(key, "hosts deny"))
     return store_host_list(&module->hosts_deny, &module->hosts_deny_count, value, "hosts deny",
                            module->name, false, err, err_size);
+  /* A recognized rsync module key with no FastSync equivalent loads inert. */
+  if (key_in_list(key, kRsyncInertModuleKeys, kRsyncInertModuleCount)) {
+    if (key_in_list(key, kRsyncUnenforcedModuleSecurityKeys, kRsyncUnenforcedModuleSecurityCount))
+      log_message(LOG_LEVEL_WARNING,
+                  "daemon config: module '%s' key '%s' is accepted for rsync compatibility but is "
+                  "NOT enforced by FastSync; the restriction it expresses will not be applied",
+                  module->name, key);
+    return true;
+  }
   set_error(err, err_size, "unknown key '%s' in module '%s'", key, module->name);
   return false;
 }
@@ -515,6 +721,7 @@ static int open_module(DaemonConf* conf, int* current_module, const char* name,
   }
   conf->modules = grown;
   memset(&conf->modules[conf->module_count], 0, sizeof(DaemonModule));
+  conf->modules[conf->module_count].read_only = conf->global.read_only_default;
   conf->modules[conf->module_count].name = str_dup(name);
   if (!conf->modules[conf->module_count].name) {
     set_error(err, err_size, "out of memory adding module '%s'", name);

src/shared/daemon_conf.h

@@ -17,7 +17,20 @@
  * DAEMON_CONF_MAX_LINE all fail the whole load with a clear, line-numbered
  * error instead of being silently ignored.  This keeps a typo from silently
  * changing what a module serves.
- */
+ *
+ * rsync compatibility: to reduce the divergence from rsync 3.4.1's rsyncd.conf
+ * grammar, the parser also ACCEPTS the common rsync GLOBAL and MODULE keys.
+ * Keys with a FastSync equivalent are mapped onto it (the native spellings are
+ * unchanged; `read only` defaults to yes like rsync, and `write only = yes`
+ * opts a module into writability).  Keys with no FastSync equivalent are
+ * accepted and documented as inert (they load successfully but have no effect)
+ * rather than failing the whole config; the accepted inert set is listed in
+ * kRsyncInertGlobalKeys / kRsyncInertModuleKeys in daemon_conf.c and in
+ * RSYNC_COMPAT.md.  Every inert key whose intent is access control is loudly
+ * warned about at load time (kRsyncUnenforced*SecurityKeys) so an operator
+ * migrating a hardened rsyncd.conf is never misled into believing the
+ * restriction is enforced.  A key outside both the FastSync-native grammar and
+ * the recognized rsync subset is still rejected as unknown. */
 
 /* A daemon module's configured root is used exactly like the standalone
  * server's --destination-root: the daemon confines every connection that
@@ -42,15 +55,21 @@
  * store refuses (fail closed) rather than falling open; see server.c.  Auth is
  * never bypassed by ignoring the list. */
 typedef struct DaemonModule {
-  char* name;        /* module name, as the client requests it */
-  char* path;        /* module root (daemon-side authorized root) */
-  bool read_only;    /* `read only = yes/no`; default no */
-  bool client_owner; /* `client owner = yes/no`; default no.  Per-module opt-in
-                        that lets this module's clients choose ownership
-                        (--numeric-ids/--chown/--usermap/--groupmap/--fake-super/
-                        --copy-as) and request explicit --super super-user
-                        activities.  Without it the daemon refuses all of them. */
-  char** auth_users; /* `auth users = a,b`; Wave B credential list */
+  char* name;              /* module name, as the client requests it */
+  char* path;              /* module root (daemon-side authorized root) */
+  bool read_only;          /* `read only = yes/no`; defaults to the global `read only`
+                              default (rsync allows it in the global section), which is
+                              itself default YES (rsync modules are read-only unless
+                              `read only = no` / `write only = yes` opts in) */
+  bool read_only_explicit; /* set when this module set its own `read only` or
+                              `write only = yes`, so a later global default (from a
+                              `--dparam read only=`) does not override it */
+  bool client_owner;       /* `client owner = yes/no`; default no.  Per-module opt-in
+                              that lets this module's clients choose ownership
+                              (--numeric-ids/--chown/--usermap/--groupmap/--fake-super/
+                              --copy-as) and request explicit --super super-user
+                              activities.  Without it the daemon refuses all of them. */
+  char** auth_users;       /* `auth users = a,b`; Wave B credential list */
   int auth_user_count;
   /* `max connections = N` (optional per-module cap).  0 means unlimited.  The
    * per-connection child records the selected module in the shared registry
@@ -69,6 +88,10 @@ typedef struct DaemonConfGlobals {
   int port;                      /* `port`, default DAEMON_CONF_DEFAULT_PORT (873) */
   char* motd_file;               /* `motd file`, may be NULL */
   char* address;                 /* `address` (optional bind address), may be NULL */
+  bool read_only_default;        /* global `read only` default for modules defined
+                                    after it (rsync allows the module key in the
+                                    global section); default YES to match rsync's
+                                    read-only modules */
   int max_connections;           /* `max connections`, default
                                     DAEMON_CONF_DEFAULT_MAX_CONNECTIONS (100) */
   int auth_failure_delay_ms;     /* `auth failure delay`, milliseconds; default
@@ -152,10 +175,13 @@ const DaemonModule* daemon_conf_find_module(const DaemonConf* conf, const char*
 bool daemon_module_name_valid(const char* name);
 
 /* Parse one --dparam=KEY=VALUE (or "--dparam KEY=VALUE") override string and
- * apply it to the global keys only.  Keys are case-insensitive and limited to
- * the global keys defined by the grammar (port, motd file, address,
+ * apply it to the global keys only.  Keys are case-insensitive and cover the
+ * global keys defined by the grammar (port, motd file, address, read only,
  * max connections, max connections per host, auth failure delay,
- * auth lockout threshold, auth lockout duration, hosts allow, hosts deny).
+ * auth lockout threshold, auth lockout duration, hosts allow, hosts deny) plus
+ * the recognized inert rsync global keys and the compact rsync spellings
+ * (`motdfile`, `pidfile`, `logfile`).  Applying `read only` sets the global
+ * default and re-applies it to every module that did not set its own value.
  * Returns 0 on success, -1 on error (err filled). */
 int daemon_conf_apply_dparam(DaemonConf* conf, const char* assignment, char* err, size_t err_size);
 

src/shared/delay_updates.c

@@ -8,13 +8,49 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <libgen.h>
+#include <stdatomic.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/file.h>
 #include <sys/stat.h>
+#include <time.h>
 #include <unistd.h>
 
+/* Process-wide counter so two staging contexts created in the same process (or
+   within the same clock tick) can never pick the same name. */
+static unsigned long long delay_updates_next_sequence(void) {
+  static atomic_ullong sequence;
+  return atomic_fetch_add_explicit(&sequence, 1, memory_order_relaxed);
+}
+
+/* Build the per-run staging directory basename: the reserved prefix plus the
+   pid and an entropy token.  A fixed name could collide with a genuine
+   destination entry; the token makes such a collision vanishingly unlikely and,
+   if it ever happens, prepare() refuses to touch the existing directory. */
+static char* delay_updates_make_staging_name(void) {
+  unsigned long long entropy = 0;
+  int fd = open("/dev/urandom", O_RDONLY | O_CLOEXEC);
+  if (fd >= 0) {
+    ssize_t got = read(fd, &entropy, sizeof(entropy));
+    close(fd);
+    if (got != (ssize_t)sizeof(entropy))
+      entropy = 0;
+  }
+  if (entropy == 0)
+    entropy = ((unsigned long long)time(NULL) << 20) ^ ((unsigned long long)getpid() << 8) ^
+              delay_updates_next_sequence();
+  int length = snprintf(NULL, 0, DELAY_UPDATES_STAGING_DIR ".%ld.%llx", (long)getpid(), entropy);
+  if (length < 0)
+    return NULL;
+  char* name = malloc((size_t)length + 1);
+  if (!name)
+    return NULL;
+  snprintf(name, (size_t)length + 1, DELAY_UPDATES_STAGING_DIR ".%ld.%llx", (long)getpid(),
+           entropy);
+  return name;
+}
+
 DelayUpdatesContext* delay_updates_context_create(const char* root_directory) {
   if (!root_directory)
     return NULL;
@@ -26,8 +62,15 @@ DelayUpdatesContext* delay_updates_context_create(const char* root_directory) {
     free(context);
     return NULL;
   }
-  context->staging_root = path_cat(root_directory, DELAY_UPDATES_STAGING_DIR);
+  context->staging_name = delay_updates_make_staging_name();
+  if (!context->staging_name) {
+    free(context->root_directory);
+    free(context);
+    return NULL;
+  }
+  context->staging_root = path_cat(root_directory, context->staging_name);
   if (!context->staging_root) {
+    free(context->staging_name);
     free(context->root_directory);
     free(context);
     return NULL;
@@ -39,6 +82,7 @@ DelayUpdatesContext* delay_updates_context_create(const char* root_directory) {
   context->lock_fd = -1;
   if (mtx_init(&context->mutex, mtx_plain) != thrd_success) {
     free(context->staging_root);
+    free(context->staging_name);
     free(context->root_directory);
     free(context);
     return NULL;
@@ -54,6 +98,7 @@ void delay_updates_context_destroy(DelayUpdatesContext* context) {
     close(context->lock_fd);
   context->lock_fd = -1;
   free(context->staging_root);
+  free(context->staging_name);
   free(context->root_directory);
   for (size_t i = 0; i < context->count; i++) {
     free(context->entries[i].staged_path);
@@ -125,48 +170,81 @@ bool delay_updates_prepare(DelayUpdatesContext* context) {
     return false;
   if (context->prepared)
     return true;
-  int fd = file_open_private_dir(context->staging_root);
-  if (fd < 0) {
+  /* Create the per-run staging directory with O_EXCL semantics.  The name is
+     unique to this transfer, so if the path already exists it is NOT ours:
+     either a genuine destination entry that happens to share the name or a
+     leftover from another session.  Refuse rather than wipe it -- the old
+     fixed-name design could destroy a real destination entry.  A crash
+     leftover is never reused (the next run picks a fresh name). */
+  char* leaf = NULL;
+  int parent_fd = file_open_secure_parent(context->staging_root, &leaf, true);
+  if (parent_fd < 0) {
     int saved_errno = errno;
     char* escaped = output_escape(context->staging_root, false);
     log_message(LOG_LEVEL_ERROR, "could not create --delay-updates staging directory '%s': %s",
                 escaped ? escaped : "<allocation failed>", strerror(saved_errno));
     free(escaped);
+    free(leaf);
     return false;
   }
-  /* Hold an exclusive advisory lock on the staging directory for the whole
-     transfer.  The staging directory name is fixed, so two simultaneous
-     delayed transfers to the same destination root would otherwise share it
-     and destroy each other's staged files.  The lock makes the second session
-     fail cleanly instead of corrupting the first.  The lock is released when
-     the context (and its file descriptor) is destroyed. */
+  int fd = openat(parent_fd, leaf, O_RDONLY | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
+  if (fd >= 0) {
+    close(fd);
+    close(parent_fd);
+    char* escaped = output_escape(context->staging_root, false);
+    log_message(LOG_LEVEL_ERROR,
+                "--delay-updates staging directory '%s' already exists and is not owned by this "
+                "transfer; refusing to overwrite it",
+                escaped ? escaped : "<allocation failed>");
+    free(escaped);
+    free(leaf);
+    return false;
+  }
+  if (errno != ENOENT) {
+    int saved_errno = errno;
+    close(parent_fd);
+    char* escaped = output_escape(context->staging_root, false);
+    log_message(LOG_LEVEL_ERROR, "could not open --delay-updates staging directory '%s': %s",
+                escaped ? escaped : "<allocation failed>", strerror(saved_errno));
+    free(escaped);
+    free(leaf);
+    return false;
+  }
+  if (mkdirat(parent_fd, leaf, 0700) != 0) {
+    int saved_errno = errno;
+    close(parent_fd);
+    char* escaped = output_escape(context->staging_root, false);
+    log_message(LOG_LEVEL_ERROR, "could not create --delay-updates staging directory '%s': %s",
+                escaped ? escaped : "<allocation failed>", strerror(saved_errno));
+    free(escaped);
+    free(leaf);
+    return false;
+  }
+  fd = openat(parent_fd, leaf, O_RDONLY | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
+  close(parent_fd);
+  free(leaf);
+  if (fd < 0) {
+    int saved_errno = errno;
+    char* escaped = output_escape(context->staging_root, false);
+    log_message(LOG_LEVEL_ERROR, "could not open --delay-updates staging directory '%s': %s",
+                escaped ? escaped : "<allocation failed>", strerror(saved_errno));
+    free(escaped);
+    return false;
+  }
+  /* Keep the exclusive advisory lock as defense in depth: the unique name
+     already prevents two sessions from sharing a staging directory, but the
+     lock also catches an improbable same-name collision that raced between the
+     existence check above and the open. */
   if (flock(fd, LOCK_EX | LOCK_NB) != 0) {
     int saved_errno = errno;
     close(fd);
-    if (saved_errno == EWOULDBLOCK || saved_errno == EAGAIN) {
-      char* escaped = output_escape(context->staging_root, false);
-      log_message(LOG_LEVEL_ERROR,
-                  "another --delay-updates transfer to '%s' is already in progress; refusing to "
-                  "share the staging directory",
-                  escaped ? escaped : "<allocation failed>");
-      free(escaped);
-    } else {
-      log_message(LOG_LEVEL_ERROR, "could not lock --delay-updates staging directory '%s': %s",
-                  context->staging_root, strerror(saved_errno));
-    }
+    char* escaped = output_escape(context->staging_root, false);
+    log_message(LOG_LEVEL_ERROR, "could not lock --delay-updates staging directory '%s': %s",
+                escaped ? escaped : "<allocation failed>", strerror(saved_errno));
+    free(escaped);
     return false;
   }
   context->lock_fd = fd;
-  /* Only now, with exclusive ownership, wipe leftovers from an interrupted
-     earlier transfer; this can never race with a live session. */
-  bool ok = delay_wipe_dir_fd(fd);
-  if (!ok) {
-    log_message(LOG_LEVEL_ERROR, "could not clear stale --delay-updates staging files under '%s'",
-                context->staging_root);
-    close(context->lock_fd);
-    context->lock_fd = -1;
-    return false;
-  }
   context->prepared = true;
   return true;
 }
@@ -264,12 +342,16 @@ static bool delay_publish_entry(DelayUpdatesContext* context, const Config* conf
                                 const StagedFileEntry* entry) {
   if (!delay_publish_backup(context, config, entry))
     return false;
-  /* --force: an incoming regular file/symlink may replace a destination
-     DIRECTORY (possibly non-empty).  The immediate-install path handles this in
-     file_receive; a --delay-updates run stages elsewhere and only discovers the
-     blocking directory here, so clear it before the rename (rsync's
-     "could not make way for new regular file" without --force). */
-  if (config && config->force_delete && file_directory_exists_secure(entry->final_path)) {
+  /* An incoming regular file/symlink may replace a destination DIRECTORY that
+     blocks it.  rsync removes the blocker recursively when --delete or --force
+     is active (its generator's "make way" deletion), and a --delay-updates run
+     stages elsewhere so it only discovers the blocker here.  FastSync's
+     immediate-install path clears it too; without --delete/--force a non-empty
+     blocker fails the run (rsync's "could not make way for new regular file").
+     use_delete is gated by the server --allow-delete policy, so a client can
+     never use this to bypass deletion authorization. */
+  if (config && (config->force_delete || config->use_delete) &&
+      file_directory_exists_secure(entry->final_path)) {
     if (!file_remove_tree_secure(entry->final_path)) {
       char* escaped = output_escape(entry->final_path, false);
       log_message(LOG_LEVEL_ERROR, "could not remove destination directory blocking '%s': %s",

src/shared/delay_updates.h

@@ -24,6 +24,7 @@ typedef struct {
    shared with the publish/cleanup phase that runs after the threads join. */
 typedef struct DelayUpdatesContext {
   char* root_directory; /* receive root the staging dir lives under */
+  char* staging_name;   /* per-run unique staging dir basename */
   char* staging_root;   /* root_directory/<staging dir name> */
   mtx_t mutex;
   StagedFileEntry* entries;
@@ -33,7 +34,11 @@ typedef struct DelayUpdatesContext {
   int lock_fd;   /* advisory exclusive flock held on the staging dir, or -1 */
 } DelayUpdatesContext;
 
-/* Name of the private staging subdirectory created under the receive root. */
+/* Reserved prefix for the private staging subdirectory created under the
+   receive root.  The actual directory name is per-run unique (the prefix plus a
+   pid/entropy token) so it can never clobber a genuine destination entry that
+   happens to share the name; the bare prefix is still what a --backup-dir must
+   not collide with. */
 #define DELAY_UPDATES_STAGING_DIR ".fastsync-stage"
 
 /* True when `dir` (ignoring a trailing "/") is the reserved staging directory

src/shared/delete.c

@@ -0,0 +1,777 @@
+#include "delete.h"
+
+#include "delay_updates.h"
+#include "filter.h"
+#include "log.h"
+#include "utils.h"
+#include <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+/* Build the keep-set index from the exact manifest entries only.  A lookup of
+   `rel` succeeds iff `rel` is a kept entry, a kept directory, or an ancestor
+   directory of kept content (the old is_dir_in_manifest predicate); the sorted
+   view answers "is an ancestor of kept content" without materializing any
+   per-component prefix copy, so the index is O(manifest size) memory. */
+static bool build_keep_index(const ArrayList* manifest, PathIndex* index) {
+  if (!manifest || manifest->size <= 0)
+    return path_index_build(index, NULL, 0);
+  return path_index_build(index, (const char* const*)manifest->items, (size_t)manifest->size);
+}
+
+static bool keep_is_dir(const PathIndex* index, const char* rel_path) {
+  return path_index_contains(index, rel_path) || path_index_has_descendant(index, rel_path);
+}
+
+static bool keep_is_file(const PathIndex* index, const char* rel_path) {
+  return path_index_contains(index, rel_path);
+}
+
+/* rsync's receiver-side verdict for one candidate extra: the per-directory
+ * chain first (deepest directory before ancestors), then the command-line base
+ * rules.  Either rule set may be absent. */
+FilterAction delete_protect_verdict(const DeleteProtectRules* protect, const char* rel_path,
+                                    const char* leaf, bool is_dir) {
+  if (!protect)
+    return FILTER_ACTION_NONE;
+  /* rsync protects its own --backup files from the delete pass: a name ending
+     in the backup suffix is never an extra.  Checked before the filter rules so
+     an explicit exclude cannot be bypassed (the suffix is always a shield). */
+  if (protect->backup_suffix && protect->backup_suffix[0] != '\0') {
+    size_t name_len = strlen(leaf);
+    size_t suffix_len = strlen(protect->backup_suffix);
+    if (name_len > suffix_len &&
+        strcmp(leaf + (name_len - suffix_len), protect->backup_suffix) == 0)
+      return FILTER_ACTION_PROTECT;
+  }
+  FilterAction action = filter_dir_rules_apply_side(protect->dir_rules, rel_path, leaf, is_dir);
+  if (action != FILTER_ACTION_NONE)
+    return action;
+  return filter_rules_apply_side(protect->base_rules, rel_path, leaf, is_dir, FILTER_SIDE_RECEIVER);
+}
+
+const char* delete_backup_suffix(const Config* config) {
+  if (!config || !config->backup || config->ignore_existing)
+    return NULL;
+  const char* suffix = config->suffix ? config->suffix : "~";
+  if (!suffix[0] || strchr(suffix, '/'))
+    return NULL;
+  return suffix;
+}
+
+/* Classify a removed entry from its st_mode for the per-type delete counters. */
+DeleteEntryType delete_entry_type_of_mode(mode_t mode) {
+  if (S_ISDIR(mode))
+    return DELETE_ENTRY_DIR;
+  if (S_ISLNK(mode))
+    return DELETE_ENTRY_LINK;
+  if (S_ISREG(mode))
+    return DELETE_ENTRY_REG;
+  return DELETE_ENTRY_SPECIAL;
+}
+
+/* True when child_rel is, or lies below, a protected entry.  A prefix "a"
+   therefore protects "a" and "a/b/c" but not "ab".  Entries with top_level_only
+   set only protect DIRECT children of the receive root (at_root); nested
+   directories that share such a name stay ordinary destination content. */
+bool path_under_skip_prefix(const char* child_rel, bool at_root, const DeleteSkipEntry* skips,
+                            int skip_count) {
+  for (int i = 0; i < skip_count; i++) {
+    if (skips[i].top_level_only && !at_root)
+      continue;
+    size_t prefix_len = strlen(skips[i].prefix);
+    if (strncmp(child_rel, skips[i].prefix, prefix_len) == 0 &&
+        (child_rel[prefix_len] == '\0' || child_rel[prefix_len] == '/'))
+      return true;
+  }
+  return false;
+}
+
+/* Per-run deletion budget and tallies.  `max_delete` is the cap on the number
+   of entries the walker may remove (SIZE_MAX = unlimited); once it is reached
+   the remaining extras are counted in `skipped` and left in place, matching
+   rsync's partial --max-delete behavior. */
+typedef struct {
+  size_t max_delete;
+  size_t deleted;
+  size_t skipped;
+  bool limit_hit;
+} DeleteBudget;
+
+/* True when direct children of the directory named by `rel` may be removed.
+   With no synchronization info (dirs == NULL) the whole tree is deletable; when
+   a dirs index is supplied only its exact entries are (the receive root is the
+   "." sentinel). */
+static bool is_synced_dir(const PathIndex* dirs, const char* rel) {
+  if (!dirs)
+    return true;
+  return path_index_contains(dirs, rel[0] == '\0' ? "." : rel);
+}
+
+/* Unsigned byte-wise string compare, matching rsync's u_strcmp (a signed
+   strcmp would order bytes >= 0x80 differently). */
+static int delete_name_cmp(const char* a, const char* b) {
+  const unsigned char* pa = (const unsigned char*)a;
+  const unsigned char* pb = (const unsigned char*)b;
+  while (*pa != '\0' && *pa == *pb) {
+    pa++;
+    pb++;
+  }
+  return (int)*pa - (int)*pb;
+}
+
+bool delete_dir_entries_collect(int dirfd, DeleteDirEntry** out, size_t* count,
+                                bool* operation_ok) {
+  *out = NULL;
+  *count = 0;
+  if (operation_ok)
+    *operation_ok = true;
+  int scanfd = openat(dirfd, ".", O_RDONLY | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
+  if (scanfd < 0)
+    return false;
+  DIR* dir = fdopendir(scanfd);
+  if (!dir) {
+    close(scanfd);
+    return false;
+  }
+  DeleteDirEntry* entries = NULL;
+  size_t used = 0;
+  size_t capacity = 0;
+  bool ok = true;
+  const struct dirent* entry;
+  while ((entry = readdir(dir)) != NULL) {
+    if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
+      continue;
+    struct stat st;
+    if (fstatat(dirfd, entry->d_name, &st, AT_SYMLINK_NOFOLLOW) != 0) {
+      if (errno != ENOENT && operation_ok)
+        *operation_ok = false;
+      continue;
+    }
+    if (used == capacity) {
+      size_t next = capacity == 0 ? 16 : capacity * 2;
+      DeleteDirEntry* grown = realloc(entries, next * sizeof(*grown));
+      if (!grown) {
+        ok = false;
+        break;
+      }
+      entries = grown;
+      capacity = next;
+    }
+    entries[used].name = str_dup(entry->d_name);
+    if (!entries[used].name) {
+      ok = false;
+      break;
+    }
+    entries[used].is_dir = S_ISDIR(st.st_mode);
+    entries[used].mode = st.st_mode;
+    used++;
+  }
+  closedir(dir);
+  if (!ok) {
+    delete_dir_entries_free(entries, used);
+    return false;
+  }
+  *out = entries;
+  *count = used;
+  return true;
+}
+
+void delete_dir_entries_free(DeleteDirEntry* entries, size_t count) {
+  if (!entries)
+    return;
+  for (size_t i = 0; i < count; i++)
+    free(entries[i].name);
+  free(entries);
+}
+
+/* rsync's extraneous-entry order: subdirectories before files, each group in
+   descending name order. */
+int delete_dir_entry_cmp_desc(const void* a, const void* b) {
+  const DeleteDirEntry* ea = a;
+  const DeleteDirEntry* eb = b;
+  if (ea->is_dir != eb->is_dir)
+    return ea->is_dir ? -1 : 1;
+  return -delete_name_cmp(ea->name, eb->name);
+}
+
+/* rsync's kept-subdirectory order: plain ascending name. */
+int delete_dir_entry_cmp_asc(const void* a, const void* b) {
+  const DeleteDirEntry* ea = a;
+  const DeleteDirEntry* eb = b;
+  return delete_name_cmp(ea->name, eb->name);
+}
+
+/* How the shared classification/descent walk disposes of an extra it has
+   identified.  LIST records the destination-relative path without touching disk
+   (the -n/--dry-run would-delete enumeration); DELETE unlinks/rmdirs it, charges
+   the shared --max-delete budget and notifies the observer.  Both modes classify
+   and traverse identically, so the dry-run enumeration and the real deletion
+   cannot drift. */
+typedef enum { DELETE_WALK_MODE_DELETE, DELETE_WALK_MODE_LIST } DeleteWalkMode;
+
+typedef struct {
+  DeleteWalkMode mode;
+  DeleteBudget* budget;        /* DELETE mode */
+  ArrayList* out;              /* LIST mode: receives strdup'd relative paths */
+  size_t* recorded;            /* LIST mode */
+  DeletePathObserver observer; /* DELETE mode */
+  void* observer_context;      /* DELETE mode */
+} DeleteWalkState;
+
+/* The per-walk invariants threaded unchanged through every recursive descent:
+   the keep/synchronized-dir indexes, the destination mode and the protection
+   rules.  Bundling them keeps the recursive helpers below to a handful of
+   positional arguments. */
+typedef struct {
+  const PathIndex* keep;
+  const PathIndex* dirs;
+  DeleteWalkState* state;
+  const DeleteSkipEntry* skips;
+  int skip_count;
+  const DeleteProtectRules* protect;
+} DeleteWalkContext;
+
+/* Duplicate `path` with rsync's trailing-slash convention, used to report a
+   removed (or would-be-removed) directory.  Returns NULL on allocation
+   failure. */
+static char* with_trailing_slash(const char* path) {
+  size_t len = strlen(path);
+  char* copy = malloc(len + 2);
+  if (!copy)
+    return NULL;
+  memcpy(copy, path, len);
+  copy[len] = '/';
+  copy[len + 1] = '\0';
+  return copy;
+}
+
+/* Forward declaration: the ordered passes below recurse through the driver. */
+static bool delete_walk_fd(int dirfd, const char* rel_path, const DeleteWalkContext* ctx,
+                           bool parent_deletable, bool* all_removed);
+
+/* Descend into the child directory `name` of `dirfd`, walking it as part of the
+   current operation.  Returns false on a genuine open/walk failure; on success
+   *child_all_removed reports whether the child removed everything it held (so
+   the caller may rmdir it). */
+static bool delete_walk_child(int dirfd, const char* name, const char* child_rel,
+                              const DeleteWalkContext* ctx, bool deletable,
+                              bool* child_all_removed) {
+  *child_all_removed = false;
+  int childfd = openat(dirfd, name, O_RDONLY | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
+  if (childfd < 0)
+    return errno == ENOENT;
+  bool ok = delete_walk_fd(childfd, child_rel, ctx, deletable, child_all_removed);
+  close(childfd);
+  return ok;
+}
+
+/* Classify every entry up front (the verdict does not depend on processing
+   order) so the ordered passes below can act on it.  Sets shielded[]/is_extra[]
+   and reports through *local_survives whether anything in this directory stays
+   in place.  Returns false on a path-construction failure. */
+static bool delete_walk_classify(const char* rel_path, const DeleteDirEntry* entries, size_t count,
+                                 const DeleteWalkContext* ctx, bool deletable, bool at_root,
+                                 bool* shielded, bool* is_extra, bool* local_survives) {
+  bool ok = true;
+  for (size_t i = 0; i < count; i++) {
+    char* child_rel = path_cat((char*)rel_path, entries[i].name);
+    if (!child_rel) {
+      ok = false;
+      continue;
+    }
+    /* A --delay-updates run keeps its staging directory as a direct child of
+       the receive root, and basis-dir snapshots live below it too.  Their
+       contents are not manifest entries, so descending into them would delete
+       every staged / basis file as an "extra".  Only the staging name (a
+       top-level-only prefix) and the basis prefixes are protected: a nested
+       destination directory that happens to be called .fastsync-stage is
+       ordinary content. */
+    if (path_under_skip_prefix(child_rel, at_root, ctx->skips, ctx->skip_count)) {
+      shielded[i] = true;
+      *local_survives = true;
+    } else if (delete_protect_verdict(ctx->protect, child_rel, entries[i].name,
+                                      entries[i].is_dir) == FILTER_ACTION_PROTECT) {
+      /* A first-match protect rule shields the extra; for a directory the whole
+         subtree is shielded (rsync prunes an excluded directory), so do not
+         descend. */
+      shielded[i] = true;
+      *local_survives = true;
+    } else if (entries[i].is_dir) {
+      bool child_synced = ctx->dirs && path_index_contains(ctx->dirs, child_rel);
+      is_extra[i] = deletable && !child_synced && !keep_is_dir(ctx->keep, child_rel);
+      if (!is_extra[i])
+        *local_survives = true;
+    } else {
+      is_extra[i] = deletable && !keep_is_file(ctx->keep, child_rel);
+      if (!is_extra[i])
+        *local_survives = true;
+    }
+    free(child_rel);
+  }
+  return ok;
+}
+
+/* Pass 1: extraneous subdirectories, descending.  Recurses into each and, when
+   the child removed everything it held, records or removes it and charges the
+   budget. */
+static bool delete_walk_extra_dirs(int dirfd, const char* rel_path, const DeleteDirEntry* entries,
+                                   size_t dir_count, const DeleteWalkContext* ctx, bool deletable,
+                                   const bool* is_extra, bool* local_survives) {
+  bool ok = true;
+  for (size_t i = 0; i < dir_count; i++) {
+    if (!is_extra[i])
+      continue;
+    char* child_rel = path_cat((char*)rel_path, entries[i].name);
+    if (!child_rel) {
+      ok = false;
+      continue;
+    }
+    bool child_all_removed = false;
+    if (!delete_walk_child(dirfd, entries[i].name, child_rel, ctx, deletable, &child_all_removed))
+      ok = false;
+    if (child_all_removed && deletable) {
+      if (ctx->state->mode == DELETE_WALK_MODE_LIST) {
+        /* Record the directory with rsync's trailing slash. */
+        char* copy = with_trailing_slash(child_rel);
+        if (!copy) {
+          ok = false;
+        } else if (!array_list_add(ctx->state->out, copy)) {
+          free(copy);
+          ok = false;
+        } else {
+          (*ctx->state->recorded)++;
+        }
+      } else if (ctx->state->budget->deleted >= ctx->state->budget->max_delete) {
+        ctx->state->budget->limit_hit = true;
+        ctx->state->budget->skipped++;
+        *local_survives = true;
+      } else if (unlinkat(dirfd, entries[i].name, AT_REMOVEDIR) != 0) {
+        /* ENOENT: already gone (fine).  ENOTEMPTY/EEXIST: the directory still
+           holds entries the walker leaves in place (a protected excluded
+           prefix, a kept file the manifest protects, a symlink); rsync leaves
+           such a directory behind, so this is not an error.  Only genuine I/O
+           failures abort the deletion. */
+        if (errno != ENOENT && errno != ENOTEMPTY && errno != EEXIST)
+          ok = false;
+        *local_survives = true;
+      } else {
+        ctx->state->budget->deleted++;
+        /* rsync reports a removed directory with a trailing slash. */
+        if (ctx->state->observer) {
+          char* with_slash = with_trailing_slash(child_rel);
+          if (with_slash) {
+            ctx->state->observer(ctx->state->observer_context, with_slash, DELETE_ENTRY_DIR);
+            free(with_slash);
+          } else {
+            ctx->state->observer(ctx->state->observer_context, child_rel, DELETE_ENTRY_DIR);
+          }
+        }
+      }
+    } else {
+      *local_survives = true;
+    }
+    free(child_rel);
+  }
+  return ok;
+}
+
+/* Pass 2: extraneous files, descending. */
+static bool delete_walk_extra_files(int dirfd, const char* rel_path, const DeleteDirEntry* entries,
+                                    size_t dir_count, size_t count, const DeleteWalkContext* ctx,
+                                    const bool* is_extra, bool* local_survives) {
+  bool ok = true;
+  for (size_t i = dir_count; i < count; i++) {
+    if (!is_extra[i])
+      continue;
+    if (ctx->state->mode == DELETE_WALK_MODE_LIST) {
+      char* child_rel = path_cat((char*)rel_path, entries[i].name);
+      if (!child_rel) {
+        ok = false;
+        continue;
+      }
+      char* copy = str_dup(child_rel);
+      if (!copy || !array_list_add(ctx->state->out, copy)) {
+        free(copy);
+        ok = false;
+      } else {
+        (*ctx->state->recorded)++;
+      }
+      free(child_rel);
+    } else if (ctx->state->budget->deleted >= ctx->state->budget->max_delete) {
+      ctx->state->budget->limit_hit = true;
+      ctx->state->budget->skipped++;
+      *local_survives = true;
+    } else if (unlinkat(dirfd, entries[i].name, 0) != 0) {
+      if (errno != ENOENT)
+        ok = false;
+      *local_survives = true;
+    } else {
+      ctx->state->budget->deleted++;
+      char* child_rel = path_cat((char*)rel_path, entries[i].name);
+      if (child_rel) {
+        if (ctx->state->observer)
+          ctx->state->observer(ctx->state->observer_context, child_rel,
+                               delete_entry_type_of_mode(entries[i].mode));
+        char* escaped_path = output_escape(child_rel, log_get_8_bit_output());
+        fprintf(stderr, "  Deleted: %s\n", escaped_path ? escaped_path : "<allocation failed>");
+        free(escaped_path);
+      }
+      free(child_rel);
+    }
+  }
+  return ok;
+}
+
+/* Pass 3: kept subdirectories, ascending (rsync descends into these only after
+   the parent's own extras have been handled). */
+static bool delete_walk_kept_dirs(int dirfd, const char* rel_path, const DeleteDirEntry* entries,
+                                  size_t dir_count, const DeleteWalkContext* ctx, bool deletable,
+                                  const bool* is_extra, const bool* shielded,
+                                  bool* local_survives) {
+  bool ok = true;
+  for (size_t i = dir_count; i-- > 0;) {
+    if (is_extra[i] || shielded[i])
+      continue;
+    char* child_rel = path_cat((char*)rel_path, entries[i].name);
+    if (!child_rel) {
+      ok = false;
+      continue;
+    }
+    bool child_all_removed = false;
+    if (!delete_walk_child(dirfd, entries[i].name, child_rel, ctx, deletable, &child_all_removed))
+      ok = false;
+    /* A kept/synchronized directory is never removed. */
+    *local_survives = true;
+    free(child_rel);
+  }
+  return ok;
+}
+
+/* Remove the extras directly inside the directory open on `dirfd` (DELETE mode)
+   or record the paths that WOULD be removed (LIST mode), recursing into every
+   child directory so kept content below a synchronized prefix is reached.
+   `all_removed` reports whether every child entry was removed (so the caller may
+   rmdir this directory).  A child directory is never removed when it is itself a
+   synchronized directory or holds kept content; with a dirs index supplied,
+   direct children of a non-synchronized directory are never extras at all (they
+   are left in place but still descended into).  Symlinks are unlinked like any
+   other non-directory extra (never followed).
+
+   Entries are processed in rsync's order (extraneous subdirectories in
+   descending name order, then extraneous files, then kept subdirectories in
+   ascending order) rather than readdir() order, so `--max-delete` leaves the
+   same survivors and the `--info=del`/dry-run line order matches rsync. */
+static bool delete_walk_fd(int dirfd, const char* rel_path, const DeleteWalkContext* ctx,
+                           bool parent_deletable, bool* all_removed) {
+  DeleteDirEntry* entries = NULL;
+  size_t count = 0;
+  bool collect_ok = true;
+  if (!delete_dir_entries_collect(dirfd, &entries, &count, &collect_ok))
+    return false;
+  bool operation_ok = collect_ok;
+  bool local_survives = false;
+  bool* shielded = calloc(count ? count : 1, sizeof(bool));
+  bool* is_extra = calloc(count ? count : 1, sizeof(bool));
+  if (!shielded || !is_extra) {
+    free(shielded);
+    free(is_extra);
+    delete_dir_entries_free(entries, count);
+    return false;
+  }
+  /* A directory is deletable when it or ANY ancestor is synchronized; the
+     `parent_deletable` flag carries that down the recursion so dest-only
+     directories below a synchronized root are removed wholesale. */
+  bool deletable = parent_deletable || is_synced_dir(ctx->dirs, rel_path);
+  bool at_root = rel_path[0] == '\0';
+
+  /* Reproduce rsync's traversal order: extraneous subdirectories in descending
+     name order, then extraneous files in descending name order, and kept
+     subdirectories only afterwards (ascending).  Sorting up front also fixes the
+     identity of the survivors under a partial --max-delete. */
+  if (count > 1)
+    qsort(entries, count, sizeof(*entries), delete_dir_entry_cmp_desc);
+  size_t dir_count = 0;
+  while (dir_count < count && entries[dir_count].is_dir)
+    dir_count++;
+
+  if (!delete_walk_classify(rel_path, entries, count, ctx, deletable, at_root, shielded, is_extra,
+                            &local_survives))
+    operation_ok = false;
+  if (!delete_walk_extra_dirs(dirfd, rel_path, entries, dir_count, ctx, deletable, is_extra,
+                              &local_survives))
+    operation_ok = false;
+  if (!delete_walk_extra_files(dirfd, rel_path, entries, dir_count, count, ctx, is_extra,
+                               &local_survives))
+    operation_ok = false;
+  if (!delete_walk_kept_dirs(dirfd, rel_path, entries, dir_count, ctx, deletable, is_extra,
+                             shielded, &local_survives))
+    operation_ok = false;
+
+  free(shielded);
+  free(is_extra);
+  delete_dir_entries_free(entries, count);
+  *all_removed = !local_survives;
+  return operation_ok;
+}
+
+/* Open the receive root following the same authorized-root confinement the
+   walker uses, or dest_root directly when no authorized root is installed. */
+static int open_destination_root(const char* dest_root) {
+  int root_fd = utils_get_authorized_root_fd();
+  if (root_fd >= 0) {
+    if (utils_get_authorized_root_path())
+      return utils_open_authorized_destination(dest_root);
+    if (dest_root == NULL)
+      return dup(root_fd);
+    return -1;
+  }
+  return open(dest_root, O_RDONLY | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
+}
+
+bool delete_extras_list(const char* dest_root, const ArrayList* manifest,
+                        const ArrayList* synced_dirs, const DeleteSkipEntry* skips, int skip_count,
+                        const DeleteProtectRules* protect, ArrayList* out, size_t* count_out) {
+  if (count_out)
+    *count_out = 0;
+  if (!manifest || !out)
+    return false;
+  PathIndex keep;
+  if (!build_keep_index(manifest, &keep))
+    return false;
+  PathIndex dirs;
+  bool have_dirs = synced_dirs != NULL;
+  if (have_dirs &&
+      !path_index_build(&dirs, (const char* const*)synced_dirs->items, (size_t)synced_dirs->size)) {
+    path_index_free(&keep);
+    return false;
+  }
+  int rootfd = open_destination_root(dest_root);
+  if (rootfd < 0) {
+    path_index_free(&keep);
+    if (have_dirs)
+      path_index_free(&dirs);
+    return false;
+  }
+  bool all_removed = false;
+  size_t recorded = 0;
+  DeleteWalkState state = {.mode = DELETE_WALK_MODE_LIST,
+                           .budget = NULL,
+                           .out = out,
+                           .recorded = &recorded,
+                           .observer = NULL,
+                           .observer_context = NULL};
+  DeleteWalkContext ctx = {.keep = &keep,
+                           .dirs = have_dirs ? &dirs : NULL,
+                           .state = &state,
+                           .skips = skips,
+                           .skip_count = skip_count,
+                           .protect = protect};
+  bool ok = delete_walk_fd(rootfd, "", &ctx, false, &all_removed);
+  if (close(rootfd) != 0)
+    ok = false;
+  path_index_free(&keep);
+  if (have_dirs)
+    path_index_free(&dirs);
+  if (count_out)
+    *count_out = recorded;
+  return ok;
+}
+
+DeleteWalkResult delete_extras_limited_observed(const char* dest_root, const ArrayList* manifest,
+                                                const ArrayList* synced_dirs, size_t max_delete,
+                                                const DeleteSkipEntry* skips, int skip_count,
+                                                const DeleteProtectRules* protect,
+                                                size_t* deleted_out, size_t* skipped_out,
+                                                DeletePathObserver observer,
+                                                void* observer_context) {
+  if (deleted_out)
+    *deleted_out = 0;
+  if (skipped_out)
+    *skipped_out = 0;
+  if (!manifest)
+    return DELETE_WALK_ERROR;
+  /* Index the keep-set (and the synchronized-dir set, when supplied) once so
+     membership is answered in O(path length) instead of scanning every entry
+     for every destination entry. */
+  PathIndex keep;
+  if (!build_keep_index(manifest, &keep))
+    return DELETE_WALK_ERROR;
+  PathIndex dirs;
+  bool have_dirs = synced_dirs != NULL;
+  if (have_dirs &&
+      !path_index_build(&dirs, (const char* const*)synced_dirs->items, (size_t)synced_dirs->size)) {
+    path_index_free(&keep);
+    return DELETE_WALK_ERROR;
+  }
+  int rootfd = open_destination_root(dest_root);
+  if (rootfd < 0) {
+    path_index_free(&keep);
+    if (have_dirs)
+      path_index_free(&dirs);
+    return DELETE_WALK_ERROR;
+  }
+  DeleteBudget budget = {.max_delete = max_delete, .deleted = 0, .skipped = 0, .limit_hit = false};
+  bool all_removed = false;
+  DeleteWalkState state = {.mode = DELETE_WALK_MODE_DELETE,
+                           .budget = &budget,
+                           .out = NULL,
+                           .recorded = NULL,
+                           .observer = observer,
+                           .observer_context = observer_context};
+  DeleteWalkContext ctx = {.keep = &keep,
+                           .dirs = have_dirs ? &dirs : NULL,
+                           .state = &state,
+                           .skips = skips,
+                           .skip_count = skip_count,
+                           .protect = protect};
+  bool ok = delete_walk_fd(rootfd, "", &ctx, false, &all_removed);
+  if (close(rootfd) != 0)
+    ok = false;
+  path_index_free(&keep);
+  if (have_dirs)
+    path_index_free(&dirs);
+  if (deleted_out)
+    *deleted_out = budget.deleted;
+  if (skipped_out)
+    *skipped_out = budget.skipped;
+  if (!ok)
+    return DELETE_WALK_ERROR;
+  return budget.limit_hit ? DELETE_WALK_LIMIT_REACHED : DELETE_WALK_OK;
+}
+
+DeleteWalkResult delete_extras_limited(const char* dest_root, const ArrayList* manifest,
+                                       const ArrayList* synced_dirs, size_t max_delete,
+                                       const DeleteSkipEntry* skips, int skip_count,
+                                       const DeleteProtectRules* protect, size_t* deleted_out,
+                                       size_t* skipped_out) {
+  return delete_extras_limited_observed(dest_root, manifest, synced_dirs, max_delete, skips,
+                                        skip_count, protect, deleted_out, skipped_out, NULL, NULL);
+}
+
+bool delete_extras(const char* dest_root, const ArrayList* manifest) {
+  return delete_extras_limited(dest_root, manifest, NULL, SIZE_MAX, NULL, 0, NULL, NULL, NULL) ==
+         DELETE_WALK_OK;
+}
+
+/* Build the delete-walk protection prefix for one basis directory.  The walker
+   compares paths relative to the receive root, so a relative entry is already
+   in the right form; an absolute entry that lies below the root is converted to
+   its root-relative form, and one outside the root returns NULL (the walk
+   cannot reach it, and it is not protected data beneath the root).  Exposed so
+   tests can exercise the root-of-"/" child mapping directly. */
+char* delete_basis_relative(const Config* config, const char* path) {
+  if (!path)
+    return NULL;
+  if (path[0] != '/')
+    return str_dup(path);
+  const char* root = config->receive_root_directory;
+  if (!root || root[0] != '/')
+    return NULL;
+  size_t root_len = strlen(root);
+  while (root_len > 1 && root[root_len - 1] == '/')
+    root_len--;
+  if (strncmp(path, root, root_len) != 0)
+    return NULL;
+  if (root_len == 1) {
+    /* `root` is "/" (the only single-character absolute root): every absolute
+       path is below it, and the child relative form is everything after the
+       leading '/'. */
+    if (path[1] == '\0')
+      return NULL; /* identical to the root, not a child */
+    return str_dup(path + 1);
+  }
+  if (path[root_len] != '/')
+    return NULL; /* identical or a sibling sharing a name prefix */
+  return str_dup(path + root_len + 1);
+}
+
+bool delete_skips_build(const Config* config, const ArrayList* protected_paths,
+                        const ArrayList* size_skipped, bool basis_root_relative,
+                        DeleteSkipSet* out) {
+  if (!out)
+    return false;
+  out->entries = NULL;
+  out->owned_prefixes = NULL;
+  out->count = 0;
+  out->owned_count = 0;
+  if (!config)
+    return false;
+  int protected_count = protected_paths ? protected_paths->size : 0;
+  int size_skipped_count = size_skipped ? size_skipped->size : 0;
+  int count =
+      (config->delay_updates ? 1 : 0) + config->basis_count + protected_count + size_skipped_count;
+  if (count == 0)
+    return true;
+  out->entries = calloc((size_t)count, sizeof(DeleteSkipEntry));
+  if (!out->entries)
+    return false;
+  if (basis_root_relative && config->basis_count > 0) {
+    out->owned_prefixes = calloc((size_t)config->basis_count, sizeof(char*));
+    if (!out->owned_prefixes) {
+      free(out->entries);
+      out->entries = NULL;
+      return false;
+    }
+    out->owned_count = config->basis_count;
+  }
+  int idx = 0;
+  if (config->delay_updates) {
+    /* Protect this transfer's actual (per-run unique) staging directory.  The
+       runtime name is only known to the receiver-side context; fall back to the
+       reserved prefix for a context that was never created (e.g. a dry run). */
+    const char* staging_name = (config->delay_context && config->delay_context->staging_name)
+                                   ? config->delay_context->staging_name
+                                   : DELAY_UPDATES_STAGING_DIR;
+    out->entries[idx].prefix = staging_name;
+    out->entries[idx].top_level_only = true;
+    idx++;
+  }
+  for (int i = 0; i < config->basis_count; i++) {
+    const char* prefix = config->basis_dirs[i].path;
+    if (basis_root_relative) {
+      /* An absolute basis outside the receive root is unreachable by this walk,
+         so it contributes no protection prefix (and no slot). */
+      char* relative = delete_basis_relative(config, config->basis_dirs[i].path);
+      if (!relative)
+        continue;
+      out->owned_prefixes[i] = relative;
+      prefix = relative;
+    }
+    out->entries[idx].prefix = prefix;
+    out->entries[idx].top_level_only = false;
+    idx++;
+  }
+  for (int i = 0; i < protected_count; i++) {
+    out->entries[idx].prefix = (const char*)protected_paths->items[i];
+    out->entries[idx].top_level_only = false;
+    idx++;
+  }
+  for (int i = 0; i < size_skipped_count; i++) {
+    out->entries[idx].prefix = (const char*)size_skipped->items[i];
+    out->entries[idx].top_level_only = false;
+    idx++;
+  }
+  out->count = idx;
+  return true;
+}
+
+void delete_skips_free(DeleteSkipSet* set) {
+  if (!set)
+    return;
+  if (set->owned_prefixes) {
+    for (int i = 0; i < set->owned_count; i++)
+      free(set->owned_prefixes[i]);
+  }
+  free(set->owned_prefixes);
+  free(set->entries);
+  set->entries = NULL;
+  set->owned_prefixes = NULL;
+  set->count = 0;
+  set->owned_count = 0;
+}

src/shared/delete.h

@@ -0,0 +1,198 @@
+#ifndef DELETE_H
+#define DELETE_H
+
+#include "array_list.h"
+#include "config.h"
+#include "filter.h"
+#include <stdbool.h>
+#include <stddef.h>
+#include <sys/stat.h>
+
+/* Delete engine.
+ *
+ * This module owns destination-relative delete traversal: the ordered directory
+ * walker that reproduces rsync's extraneous-entry order, the skip-prefix
+ * protection set shared by every delete pass, and the read-only enumeration
+ * that mirrors the walker for -n/--dry-run.  The budgeted manifest commit
+ * (delete_commit.c) and the per-directory delete plans (delete_plan.c) are
+ * built on the primitives exported here. */
+
+/* Result of a bounded extra-file deletion run. */
+typedef enum {
+  /* Every extra entry was removed (or there were none). */
+  DELETE_WALK_OK = 0,
+  /* The numeric cap for this run was reached before every extra was removed.
+     The walker removed exactly the entries the cap allowed and skipped (without
+     removing) the rest, matching rsync's partial --max-delete behavior. */
+  DELETE_WALK_LIMIT_REACHED,
+  /* A traversal or unlink failure aborted the deletion (partial removal is
+     possible, mirroring the delete pass). */
+  DELETE_WALK_ERROR
+} DeleteWalkResult;
+
+/* Receiver-side delete-protection rules for one walk.  `base_rules` is the
+ * command-line rule set the config frame carried (owner "" rules); `dir_rules`
+ * is the received per-directory rule set (rules carrying their owner directory
+ * and no-inherit flag).  Either may be NULL. */
+typedef struct {
+  const FilterRuleList* base_rules;
+  const FilterRuleList* dir_rules;
+  /* When non-NULL and non-empty, a destination entry whose name ends with this
+     suffix is protected from deletion.  rsync never treats a --backup file as
+     an extra, so a backup created at --delay-updates publication (or a
+     pre-existing one) survives the delete-after pass. */
+  const char* backup_suffix;
+} DeleteProtectRules;
+
+/* rsync's first-match-wins receiver verdict for one candidate extra: the
+ * per-directory chain is evaluated first (the containing directory's rules,
+ * then each ancestor's, then the receive root's), then the base rules.  Returns
+ * FILTER_ACTION_PROTECT when the entry is shielded by a receiver-side exclude,
+ * FILTER_ACTION_RISK when an include explicitly leaves it at risk, or
+ * FILTER_ACTION_NONE when no rule matched. */
+FilterAction delete_protect_verdict(const DeleteProtectRules* protect, const char* rel_path,
+                                    const char* leaf, bool is_dir);
+
+/* The backup suffix the delete walker must shield from deletion, or NULL when
+   --backup is inactive or the configured suffix is unusable (empty, or holding
+   a path separator).  Matches the suffix file_save uses for backups. */
+const char* delete_backup_suffix(const Config* config);
+
+/* One protected entry for the delete walker.  When top_level_only is true the
+   prefix is skipped only as a DIRECT child of dest_root (the --delay-updates
+   staging directory, which must not hide genuine extras inside a nested
+   destination directory that happens to share the staging name); otherwise the
+   prefix is skipped at any depth (the --compare-dest/--copy-dest/--link-dest
+   basis trees, and the sender-side protected filter-excluded prefixes, which
+   are never destination content). */
+typedef struct {
+  const char* prefix;
+  bool top_level_only;
+} DeleteSkipEntry;
+
+/* A built skip-prefix set.  `entries`/`count` are what path_under_skip_prefix()
+   consumes.  `owned_prefixes` holds any prefix strings the builder had to
+   allocate (root-relative basis-dir conversions); it is NULL when every prefix
+   is borrowed from the config or the caller's lists.  Release with
+   delete_skips_free(). */
+typedef struct {
+  DeleteSkipEntry* entries;
+  char** owned_prefixes;
+  int count;
+  int owned_count;
+} DeleteSkipSet;
+
+/* True when child_rel is, or lies below, one of the protected entries (a prefix
+   "a" protects "a" and "a/b/c" but not "ab"; top_level_only entries protect
+   only DIRECT children of the destination root, i.e. child_rel has no '/'). */
+bool path_under_skip_prefix(const char* child_rel, bool at_root, const DeleteSkipEntry* skips,
+                            int skip_count);
+
+/* One destination-directory entry collected up front so the delete walkers can
+   reproduce rsync's traversal order instead of readdir() order.  rsync processes
+   a directory's extraneous subdirectories first (descending name, depth-first),
+   then its extraneous files (descending name), and only afterwards descends into
+   its kept subdirectories (ascending name). */
+typedef struct {
+  char* name;
+  bool is_dir;
+  /* The entry's full st_mode from the AT_SYMLINK_NOFOLLOW stat, so a delete
+     observer can classify a removed non-directory as reg/link/special. */
+  mode_t mode;
+} DeleteDirEntry;
+/* Collect the entries of the directory open on `dirfd` (excluding "." and ".."),
+   stat'ing each with AT_SYMLINK_NOFOLLOW.  On success *out is a malloc'd array of
+   *count entries whose names the caller frees with delete_dir_entries_free().
+   Returns false on an allocation/readdir failure; a vanished entry (ENOENT) is
+   skipped, any other stat failure is reported through *operation_ok while the
+   walk continues. */
+bool delete_dir_entries_collect(int dirfd, DeleteDirEntry** out, size_t* count, bool* operation_ok);
+void delete_dir_entries_free(DeleteDirEntry* entries, size_t count);
+/* Sort comparators: `_desc` orders subdirectories before files and each group by
+   descending name (rsync's extraneous-entry order); `_asc` orders plain ascending
+   name (rsync's kept-subdirectory order). */
+int delete_dir_entry_cmp_desc(const void* a, const void* b);
+int delete_dir_entry_cmp_asc(const void* a, const void* b);
+
+/* Remove files/dirs/symlinks under dest_root that are not listed in manifest
+   without ever descending into a protected prefix (see DeleteSkipEntry).  When
+   `synced_dirs` is non-NULL, extras are only removed directly inside a directory
+   whose destination-relative path is an exact entry in that list (the receive
+   root is the "." sentinel); directories outside the synchronized set are still
+   descended into so kept content below a listed directory is preserved, but
+   nothing in them is removed.  A NULL `synced_dirs` keeps the legacy behavior of
+   treating the whole destination tree as deletable.  `max_delete` caps the
+   number of removed entries (SIZE_MAX = unlimited): the walker removes up to the
+   cap and returns DELETE_WALK_LIMIT_REACHED when more extras remained.
+   `deleted_out`/`skipped_out` optionally receive the number of entries removed
+   and the number skipped because of the cap. */
+DeleteWalkResult delete_extras_limited(const char* dest_root, const ArrayList* manifest,
+                                       const ArrayList* synced_dirs, size_t max_delete,
+                                       const DeleteSkipEntry* skips, int skip_count,
+                                       const DeleteProtectRules* protect, size_t* deleted_out,
+                                       size_t* skipped_out);
+
+/* Entry kind of a removed path, reported to the delete observer so the receiver
+   can build rsync's `--stats` `Number of deleted files` per-type breakdown.  The
+   four categories are a strict partition of every removed entry. */
+typedef enum {
+  DELETE_ENTRY_REG = 0,
+  DELETE_ENTRY_DIR,
+  DELETE_ENTRY_LINK,
+  DELETE_ENTRY_SPECIAL
+} DeleteEntryType;
+
+/* Optional per-deletion observer: called for each destination-relative path
+   actually removed (a file, symlink, or directory) with its entry kind, in
+   removal order, so the receiver can stream rsync's `--info=del`/`--info=remove`
+   lines and tally the per-type `--stats` counters. */
+typedef void (*DeletePathObserver)(void* context, const char* rel_path, DeleteEntryType type);
+
+/* Classify a removed entry from its st_mode for the per-type delete counters. */
+DeleteEntryType delete_entry_type_of_mode(mode_t mode);
+
+/* `delete_extras_limited_observed` is delete_extras_limited with an optional
+ * observer; the observer is invoked only for entries truly removed.  When
+ * `protect` is non-NULL its receiver-side verdict is evaluated for every
+ * candidate extra: a first-match PROTECT leaves the entry (and, for a
+ * directory, its whole subtree) in place, while RISK/NONE fall through to the
+ * ordinary skip-prefix/keep-set logic. */
+DeleteWalkResult delete_extras_limited_observed(const char* dest_root, const ArrayList* manifest,
+                                                const ArrayList* synced_dirs, size_t max_delete,
+                                                const DeleteSkipEntry* skips, int skip_count,
+                                                const DeleteProtectRules* protect,
+                                                size_t* deleted_out, size_t* skipped_out,
+                                                DeletePathObserver observer,
+                                                void* observer_context);
+/* Read-only companion to delete_extras_limited: walk the destination exactly as
+   the delete pass would and APPEND (strdup'd) destination-relative paths that
+   WOULD be removed, without touching disk.  Used for -n/--dry-run --delete
+   would-delete reporting.  Returns true on a clean walk; the caller owns the
+   strings appended to `out` and receives their count in *count_out. */
+bool delete_extras_list(const char* dest_root, const ArrayList* manifest,
+                        const ArrayList* synced_dirs, const DeleteSkipEntry* skips, int skip_count,
+                        const DeleteProtectRules* protect, ArrayList* out, size_t* count_out);
+bool delete_extras(const char* dest_root, const ArrayList* manifest);
+
+/* Build the delete walk's skip-prefix set from the config's --delay-updates
+   staging directory, its --compare-dest/--copy-dest/--link-dest basis dirs, and
+   the caller-supplied protection lists, in that order.  `protected_paths` and
+   `size_skipped` are borrowed (may be NULL); every entry in them is protected at
+   any depth.  The staging directory is protected only as a DIRECT child of the
+   receive root.  `basis_root_relative` selects how a basis path becomes a
+   prefix: true converts an absolute path under the receive root to its
+   root-relative form (the whole-tree commit walk; an unreachable path
+   contributes no slot), false keeps the configured path verbatim (the
+   per-directory plan walk).  On success the caller releases `*out` with
+   delete_skips_free(); returns false on allocation failure. */
+bool delete_skips_build(const Config* config, const ArrayList* protected_paths,
+                        const ArrayList* size_skipped, bool basis_root_relative,
+                        DeleteSkipSet* out);
+void delete_skips_free(DeleteSkipSet* set);
+
+/* Convert one basis-directory path to the receive-root-relative protection
+   prefix the delete walker uses (NULL when it lies outside the root).  Exposed
+   for unit tests of the root-of-"/" and normalization edge cases. */
+char* delete_basis_relative(const Config* config, const char* path);
+
+#endif

src/shared/delete_commit.c

@@ -0,0 +1,530 @@
+#include <errno.h>
+#include <ctype.h>
+#include <dirent.h>
+#include <fcntl.h>
+#include <libgen.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/sysmacros.h>
+#include <unistd.h>
+
+#include "array_list.h"
+#include "charset.h"
+#include "chmod.h"
+#include "chunk.h"
+#include "compression.h"
+#include "config.h"
+#include "data.h"
+#include "delay_updates.h"
+#include "delete_commit.h"
+#include "delete_plan.h"
+#include "delta.h"
+#include "file.h"
+#include "format.h"
+#include "identity.h"
+#include "log.h"
+#include "metadata.h"
+#include "protocol.h"
+#include "utils.h"
+#include "xattr.h"
+
+#define MAX_SERVER_DELETE_COUNT 100000U
+/* Retained cost of one delete-manifest entry beyond its path bytes: the
+   ArrayList pointer slot plus an approximate malloc header/rounding for the
+   heap copy.  Charged against MAX_MANIFEST_BYTES so a frame full of tiny paths
+   cannot retain far more than the byte budget (B5). */
+#define MANIFEST_ENTRY_OVERHEAD (sizeof(char*) + 16)
+
+/* Read a delete-manifest frame (the STATUS_MANIFEST leading code has already
+   been consumed): a keep-set entry count followed by that many
+   destination-relative paths, then a protected-prefix count followed by that
+   many destination-relative prefixes, then a missing-args count followed by that
+   many destination-relative delete paths, then (protocol 2.23.0) a
+   synchronized-directory count followed by that many destination-relative
+   directory paths (the receive root is the "." sentinel).  The frame is
+   self-delimiting (the counts are authoritative), so the caller decides what to
+   do next and continues reading the following STATUS_* frame.  Every section is
+   validated identically: an entry must be non-empty, relative and traversal-free
+   and the aggregate length across ALL sections is capped by MAX_MANIFEST_BYTES
+   (so the missing-args deletion requests are confined like the rest of the
+   manifest).  Returns an owned DeleteManifest, or NULL after sending STATUS_ERROR
+   when the frame is malformed (bad count, empty/absolute path, path traversal,
+   or an aggregate size beyond MAX_MANIFEST_BYTES). */
+static bool receive_manifest_section(int fd, ArrayList* list, size_t* manifest_bytes,
+                                     size_t* manifest_entries) {
+  int count;
+  if (!receive_int(fd, &count)) {
+    send_status(fd, STATUS_ERROR);
+    return false;
+  }
+  if (count < 0 || count > MAX_MANIFEST_ENTRIES ||
+      (size_t)count > MAX_MANIFEST_ENTRIES - *manifest_entries) {
+    send_status(fd, STATUS_ERROR);
+    return false;
+  }
+  for (int i = 0; i < count; i++) {
+    char* s = receive_wire_str(fd);
+    size_t entry_size = s ? strlen(s) + MANIFEST_ENTRY_OVERHEAD : 0;
+    if (!s || s[0] == '\0' || s[0] == '/' || has_path_traversal(s) ||
+        entry_size > MAX_MANIFEST_BYTES - *manifest_bytes ||
+        (*manifest_bytes += entry_size) > MAX_MANIFEST_BYTES || !array_list_add(list, s)) {
+      free(s);
+      send_status(fd, STATUS_ERROR);
+      return false;
+    }
+  }
+  *manifest_entries += (size_t)count;
+  return true;
+}
+
+DeleteManifest* receive_manifest_entries(int fd) {
+  DeleteManifest* manifest = calloc(1, sizeof(DeleteManifest));
+  if (!manifest) {
+    send_status(fd, STATUS_ERROR);
+    return NULL;
+  }
+  manifest->keeps = array_list_create(free);
+  manifest->protected = array_list_create(free);
+  manifest->missing = array_list_create(free);
+  manifest->dirs = array_list_create(free);
+  if (!manifest->keeps || !manifest->protected || !manifest->missing || !manifest->dirs) {
+    delete_manifest_free(manifest);
+    send_status(fd, STATUS_ERROR);
+    return NULL;
+  }
+  size_t manifest_bytes = 0;
+  size_t manifest_entries = 0;
+  if (!receive_manifest_section(fd, manifest->keeps, &manifest_bytes, &manifest_entries) ||
+      !receive_manifest_section(fd, manifest->protected, &manifest_bytes, &manifest_entries) ||
+      !receive_manifest_section(fd, manifest->missing, &manifest_bytes, &manifest_entries) ||
+      !receive_manifest_section(fd, manifest->dirs, &manifest_bytes, &manifest_entries)) {
+    delete_manifest_free(manifest);
+    return NULL;
+  }
+  /* Per-directory filter rules (protocol 2.30.0) follow the manifest sections
+   * with their own bounded self-describing format. */
+  if (!delete_filter_dir_rules_receive(fd, &manifest->per_dir_rules)) {
+    delete_manifest_free(manifest);
+    send_status(fd, STATUS_ERROR);
+    return NULL;
+  }
+  return manifest;
+}
+
+void delete_manifest_free(DeleteManifest* manifest) {
+  if (!manifest)
+    return;
+  array_list_delete(manifest->keeps);
+  array_list_delete(manifest->protected);
+  array_list_delete(manifest->missing);
+  array_list_delete(manifest->dirs);
+  filter_rule_list_free(manifest->per_dir_rules);
+  free(manifest);
+}
+
+/* Shared --max-delete budget for one receiver-side deletion commit.  Both the
+   --delete-missing-args exact-path removals and the ordinary extras walk draw
+   from the same tally, matching rsync (whose --max-delete counts every deleted
+   file or directory).  `max_delete` is SIZE_MAX for an unlimited budget. */
+typedef struct {
+  size_t max_delete;
+  size_t deleted;
+  size_t skipped;
+  bool limit_hit;
+} DeleteBudgetState;
+
+/* Remove every destination entry under the receive root that is not in the
+   keep-set, bounded by the shared budget (a smaller client --max-delete=NUM
+   replaces the server hard bound; rsync deletes up to the bound and skips the
+   rest).  With --delay-updates the not-yet-published staging directory is a
+   direct child of the receive root and must not be treated as a set of extras;
+   the manifest's protected prefixes (paths excluded on the source), the
+   size-pruned prefixes (--max-size/--min-size, always protected) and the
+   alternate basis directories are never destination content and are skipped at
+   any depth.  Returns true unless a traversal/unlink error aborted the walk;
+   the budget's limit_hit/skipped fields report a cap-stopped run. */
+static bool delete_extras_budgeted_observed(const Config* config, const DeleteManifest* manifest,
+                                            DeleteBudgetState* budget, DeletePathObserver observer,
+                                            void* observer_context) {
+  if (!config || !manifest || !manifest->keeps)
+    return false;
+  fprintf(stderr, "Deleting files not in manifest...\n");
+  /* Protected entries: the --delay-updates staging name (only as a DIRECT child
+     of the receive root), the alternate basis directories and the sender-side
+     protected prefixes (filter-excluded and size-pruned source mirrors), all at
+     any depth.  See delete_skips_build(). */
+  DeleteSkipSet skips;
+  if (!delete_skips_build(config, manifest->protected, NULL, true, &skips))
+    return false;
+  /* Clamp rather than subtract: an accounting bug where deleted already exceeds
+     max_delete must never underflow into an effectively unlimited budget. */
+  size_t remaining;
+  if (budget->max_delete == SIZE_MAX)
+    remaining = SIZE_MAX;
+  else if (budget->deleted >= budget->max_delete)
+    remaining = 0;
+  else
+    remaining = budget->max_delete - budget->deleted;
+  size_t deleted = 0;
+  size_t skipped = 0;
+  DeleteProtectRules protect = {.base_rules = config->protect_rules,
+                                .dir_rules = manifest->per_dir_rules,
+                                .backup_suffix = delete_backup_suffix(config)};
+  DeleteWalkResult result = delete_extras_limited_observed(
+      config->receive_root_directory, manifest->keeps, manifest->dirs, remaining, skips.entries,
+      skips.count, &protect, &deleted, &skipped, observer, observer_context);
+  delete_skips_free(&skips);
+  budget->deleted += deleted;
+  budget->skipped += skipped;
+  if (result == DELETE_WALK_LIMIT_REACHED) {
+    budget->limit_hit = true;
+    return true;
+  }
+  if (result != DELETE_WALK_OK) {
+    log_message(LOG_LEVEL_ERROR, "deletion failed while removing extraneous files");
+    return false;
+  }
+  return true;
+}
+
+static bool delete_extras_budgeted(const Config* config, const DeleteManifest* manifest,
+                                   DeleteBudgetState* budget) {
+  return delete_extras_budgeted_observed(config, manifest, budget, NULL, NULL);
+}
+
+/* Prefixes every observed path with a fixed subtree root, so a nested walk
+   (a recursively removed missing-arg directory) reports receive-root-relative
+   names like the rest of the delete output. */
+typedef struct {
+  DeletePathObserver inner;
+  void* inner_context;
+  const char* prefix;
+} PrefixedDeleteObserver;
+
+static void prefixed_delete_observer(void* context, const char* rel, DeleteEntryType type) {
+  PrefixedDeleteObserver* prefixed = context;
+  if (!prefixed->inner || !rel)
+    return;
+  char* joined = path_cat((char*)prefixed->prefix, rel);
+  if (joined) {
+    prefixed->inner(prefixed->inner_context, joined, type);
+    free(joined);
+  }
+}
+
+/* --delete-missing-args exact-path deletions: each destination mirror in
+   manifest->missing is an explicit user request, so it is removed even when the
+   ordinary extras walk (with its protected prefixes) would leave it alone.  The
+   --delay-updates staging directory and basis snapshots are receiver artifacts
+   and stay protected exactly as in the extras walker.  A regular file or
+   symlink is unlinked, an empty directory removed, and a NON-empty directory is
+   removed recursively only when --delete or --force is in effect (rsync parity:
+   the man page says a non-empty directory mirror is only deleted with --force
+   or --delete); otherwise it is left with a warning and the run continues.  A
+   mirror that does not exist is a no-op.  Each removal draws from the shared
+   --max-delete budget: once it is exhausted the remaining requests are skipped
+   and counted.  Returns false only on a genuine error (a confinement failure on
+   a validated path or an I/O error), which fails the run. */
+
+/* How one missing-args request leaves the driver loop.  The original walker
+   `continue`s past an invalid/protected/absent/budget-skipped request (without
+   breaking) but stops after a request that ran to completion while an error is
+   pending; NEXT/STOP preserve that control flow exactly. */
+typedef enum { MISSING_ARG_NEXT, MISSING_ARG_STOP } MissingArgStep;
+
+/* Remove a NON-empty missing-args directory recursively (--delete/--force in
+   effect): walk its contents through the budgeted extras walker so every removed
+   file/dir counts toward --max-delete (rsync parity), then remove the now-empty
+   directory itself, which costs one more budget unit.  A run that hits the cap
+   leaves the remaining entries in place.  The observer is wrapped so the nested
+   walk reports receive-root-relative paths.  Sets the *removed and *ok outputs. */
+static void delete_nonempty_missing_dir(const char* full, const char* rel,
+                                        DeleteBudgetState* budget, DeletePathObserver observer,
+                                        void* observer_context, bool* removed, bool* ok) {
+  ArrayList* no_keeps = array_list_create(free);
+  /* Never let an accounting slip (deleted > max_delete) underflow the remaining
+     budget into SIZE_MAX, which would grant unlimited deletions. */
+  size_t remaining =
+      budget->deleted >= budget->max_delete ? 0 : budget->max_delete - budget->deleted;
+  size_t contents_deleted = 0;
+  size_t contents_skipped = 0;
+  PrefixedDeleteObserver nested = {observer, observer_context, rel};
+  DeleteWalkResult walk =
+      no_keeps ? delete_extras_limited_observed(full, no_keeps, NULL, remaining, NULL, 0, NULL,
+                                                &contents_deleted, &contents_skipped,
+                                                observer ? prefixed_delete_observer : NULL,
+                                                observer ? &nested : NULL)
+               : DELETE_WALK_ERROR;
+  if (no_keeps)
+    array_list_delete(no_keeps);
+  budget->deleted += contents_deleted;
+  budget->skipped += contents_skipped;
+  if (walk == DELETE_WALK_LIMIT_REACHED) {
+    budget->limit_hit = true;
+  } else if (walk != DELETE_WALK_OK) {
+    *ok = false;
+  } else if (budget->deleted >= budget->max_delete) {
+    budget->limit_hit = true;
+    budget->skipped++;
+  } else if (file_remove_tree_secure(full)) {
+    /* The shared `if (removed)` tail charges this directory exactly once;
+       counting it here too would consume two budget units. */
+    *removed = true;
+  } else {
+    *ok = false;
+  }
+}
+
+/* Remove one missing-args destination mirror.  `skips` holds the receiver
+   artifacts (staging directory, basis snapshots) that stay protected.  Returns
+   MISSING_ARG_STOP when the driver loop must stop (a completed removal left a
+   genuine error pending) and MISSING_ARG_NEXT otherwise; *ok accumulates the
+   overall success across the whole run. */
+static MissingArgStep delete_one_missing_arg(const Config* config, const char* rel,
+                                             const DeleteSkipSet* skips, DeleteBudgetState* budget,
+                                             DeletePathObserver observer, void* observer_context,
+                                             bool* ok) {
+  if (!rel || *rel == '\0' || *rel == '/' || has_path_traversal(rel)) {
+    /* Defensive only: receive_manifest_entries already validated every
+       section identically, so a controlled peer never reaches this branch. */
+    log_message(LOG_LEVEL_ERROR, "invalid missing-args delete path");
+    *ok = false;
+    return MISSING_ARG_NEXT;
+  }
+  bool at_root = strchr(rel, '/') == NULL;
+  if (path_under_skip_prefix(rel, at_root, skips->entries, skips->count)) {
+    char* escaped = output_escape(rel, log_get_8_bit_output());
+    log_message(LOG_LEVEL_WARNING,
+                "missing-args path '%s' is protected (staging directory or basis snapshot); "
+                "not deleting",
+                escaped ? escaped : "<allocation failed>");
+    free(escaped);
+    return MISSING_ARG_NEXT;
+  }
+  char* full = path_cat(config->receive_root_directory, rel);
+  if (!full) {
+    *ok = false;
+    return MISSING_ARG_NEXT;
+  }
+  char* leaf = NULL;
+  int parent_fd = file_open_secure_parent(full, &leaf, false);
+  if (parent_fd < 0) {
+    /* The mirror's parent directory may itself not exist on the destination
+       (a deeper missing entry whose leading directories were never created).
+       That is a no-op -- there is nothing to delete -- matching
+       file_remove_tree_secure's absent-path handling; only a genuine I/O
+       error (EACCES, a symlink loop, ...) fails the run. */
+    bool absent = errno == ENOENT || errno == ENOTDIR;
+    free(full);
+    free(leaf);
+    if (!absent)
+      *ok = false;
+    return MISSING_ARG_NEXT;
+  }
+  struct stat st;
+  if (fstatat(parent_fd, leaf, &st, AT_SYMLINK_NOFOLLOW) != 0) {
+    /* Already absent: nothing to delete (a no-op, not a deletion). */
+    if (errno != ENOENT)
+      *ok = false;
+    close(parent_fd);
+    free(leaf);
+    free(full);
+    return MISSING_ARG_NEXT;
+  }
+  /* An entry that exists is one deletion: skip it (and count it) when the
+     shared --max-delete budget is already exhausted. */
+  if (budget->deleted >= budget->max_delete) {
+    budget->limit_hit = true;
+    budget->skipped++;
+    close(parent_fd);
+    free(leaf);
+    free(full);
+    return MISSING_ARG_NEXT;
+  }
+  bool removed = false;
+  if (S_ISDIR(st.st_mode)) {
+    if (unlinkat(parent_fd, leaf, AT_REMOVEDIR) == 0) {
+      removed = true;
+    } else if (errno == ENOTEMPTY || errno == EEXIST) {
+      close(parent_fd);
+      parent_fd = -1;
+      free(leaf);
+      leaf = NULL;
+      if (config->use_delete || config->force_delete) {
+        delete_nonempty_missing_dir(full, rel, budget, observer, observer_context, &removed, ok);
+      } else {
+        char* escaped = output_escape(rel, log_get_8_bit_output());
+        log_message(LOG_LEVEL_WARNING,
+                    "missing-args destination '%s' is a non-empty directory; use --force or "
+                    "--delete to remove it",
+                    escaped ? escaped : "<allocation failed>");
+        free(escaped);
+      }
+    } else if (errno != ENOENT) {
+      *ok = false;
+    }
+  } else {
+    if (unlinkat(parent_fd, leaf, 0) == 0) {
+      removed = true;
+    } else if (errno != ENOENT) {
+      *ok = false;
+    }
+  }
+  if (removed) {
+    budget->deleted++;
+    if (observer)
+      observer(observer_context, rel, delete_entry_type_of_mode(st.st_mode));
+    char* escaped = output_escape(rel, log_get_8_bit_output());
+    fprintf(stderr, "  Deleted: %s\n", escaped ? escaped : "<allocation failed>");
+    free(escaped);
+  }
+  if (parent_fd >= 0)
+    close(parent_fd);
+  free(leaf);
+  free(full);
+  return *ok ? MISSING_ARG_NEXT : MISSING_ARG_STOP;
+}
+
+static bool delete_missing_args_budgeted_observed(const Config* config,
+                                                  const DeleteManifest* manifest,
+                                                  DeleteBudgetState* budget,
+                                                  DeletePathObserver observer,
+                                                  void* observer_context) {
+  if (!config || !manifest)
+    return false;
+  if (!manifest->missing || manifest->missing->size == 0)
+    return true;
+  fprintf(stderr, "Deleting destination mirrors of missing source arguments...\n");
+  /* The staging directory and basis snapshots stay protected exactly as in the
+     extras walker (the missing-args path overrides the ordinary protected
+     prefixes, so those are not passed here). */
+  DeleteSkipSet skips;
+  if (!delete_skips_build(config, NULL, NULL, true, &skips))
+    return false;
+  bool ok = true;
+  for (int i = 0; i < manifest->missing->size; i++) {
+    const char* rel = (const char*)manifest->missing->items[i];
+    if (delete_one_missing_arg(config, rel, &skips, budget, observer, observer_context, &ok) ==
+        MISSING_ARG_STOP)
+      break;
+  }
+  delete_skips_free(&skips);
+  return ok;
+}
+
+/* Public wrappers used outside the commit path (and by unit tests): no
+   --max-delete budget. */
+bool manifest_would_delete_list(const Config* config, const DeleteManifest* manifest,
+                                ArrayList* out, size_t* count_out) {
+  if (count_out)
+    *count_out = 0;
+  if (!config || !manifest || !manifest->keeps || !out)
+    return false;
+  DeleteSkipSet skips;
+  if (!delete_skips_build(config, manifest->protected, NULL, true, &skips))
+    return false;
+  DeleteProtectRules protect = {.base_rules = config->protect_rules,
+                                .dir_rules = manifest->per_dir_rules,
+                                .backup_suffix = delete_backup_suffix(config)};
+  bool ok = delete_extras_list(config->receive_root_directory, manifest->keeps, manifest->dirs,
+                               skips.entries, skips.count, &protect, out, count_out);
+  delete_skips_free(&skips);
+  return ok;
+}
+
+bool manifest_delete_extras(const Config* config, const DeleteManifest* manifest) {
+  DeleteBudgetState budget = {
+      .max_delete = SIZE_MAX, .deleted = 0, .skipped = 0, .limit_hit = false};
+  return delete_extras_budgeted(config, manifest, &budget);
+}
+
+bool manifest_delete_missing_args(const Config* config, const DeleteManifest* manifest) {
+  DeleteBudgetState budget = {
+      .max_delete = SIZE_MAX, .deleted = 0, .skipped = 0, .limit_hit = false};
+  return delete_missing_args_budgeted_observed(config, manifest, &budget, NULL, NULL);
+}
+
+bool manifest_delete_missing_args_limited(const Config* config, const DeleteManifest* manifest,
+                                          size_t max_delete, size_t* deleted, size_t* skipped,
+                                          bool* limit_hit) {
+  return manifest_delete_missing_args_limited_observed(config, manifest, max_delete, deleted,
+                                                       skipped, limit_hit, NULL, NULL);
+}
+
+bool manifest_delete_missing_args_limited_observed(
+    const Config* config, const DeleteManifest* manifest, size_t max_delete, size_t* deleted,
+    size_t* skipped, bool* limit_hit, DeletePathObserver observer, void* observer_context) {
+  DeleteBudgetState budget = {
+      .max_delete = max_delete, .deleted = 0, .skipped = 0, .limit_hit = false};
+  bool ok =
+      delete_missing_args_budgeted_observed(config, manifest, &budget, observer, observer_context);
+  if (deleted)
+    *deleted = budget.deleted;
+  if (skipped)
+    *skipped = budget.skipped;
+  if (limit_hit)
+    *limit_hit = budget.limit_hit;
+  return ok;
+}
+
+/* Commit every deletion family the manifest carries.  The --delete-missing-args
+   exact-path deletions run FIRST: they are explicit user requests and must not
+   be blocked by the extras walker's filter-exclusion protection (a protected
+   leftover inside a missing-argument directory must not make that user-requested
+   removal fail).  The ordinary extras walk then runs when --delete is active.
+   Both draw from one --max-delete budget; the result reports a cap-stopped
+   (partial) commit distinctly so the client can exit 25 like rsync. */
+DeleteCommitResult manifest_delete_all(const Config* config, const DeleteManifest* manifest) {
+  return manifest_delete_all_counted(config, manifest, NULL);
+}
+
+DeleteCommitResult manifest_delete_all_counted(const Config* config, const DeleteManifest* manifest,
+                                               size_t* deleted) {
+  return manifest_delete_all_observed(config, manifest, deleted, NULL, NULL);
+}
+
+DeleteCommitResult manifest_delete_all_observed(const Config* config,
+                                                const DeleteManifest* manifest, size_t* deleted,
+                                                DeletePathObserver observer,
+                                                void* observer_context) {
+  if (deleted)
+    *deleted = 0;
+  if (!config || !manifest)
+    return DELETE_COMMIT_ERROR;
+  /* Central no-mutation guard: a dry-run never deletes.  No manifest is sent on
+     the dry-run path, but a hostile/buggy peer could; treat it as a no-op so
+     the receiver can never remove anything. */
+  if (config->dry_run)
+    return DELETE_COMMIT_OK;
+  /* A client --max-delete=NUM smaller than the server's hard bound replaces it
+     for this run; both still bound the commit. */
+  bool user_limited =
+      config->max_delete >= 0 && (size_t)config->max_delete < MAX_SERVER_DELETE_COUNT;
+  DeleteBudgetState budget = {.max_delete = user_limited ? (size_t)config->max_delete
+                                                         : MAX_SERVER_DELETE_COUNT,
+                              .deleted = 0,
+                              .skipped = 0,
+                              .limit_hit = false};
+  if (config->delete_missing_args &&
+      !delete_missing_args_budgeted_observed(config, manifest, &budget, observer, observer_context))
+    return DELETE_COMMIT_ERROR;
+  if (config->use_delete &&
+      !delete_extras_budgeted_observed(config, manifest, &budget, observer, observer_context))
+    return DELETE_COMMIT_ERROR;
+  if (deleted)
+    *deleted = budget.deleted;
+  if (budget.limit_hit) {
+    if (user_limited) {
+      log_message(LOG_LEVEL_ERROR, "Deletions stopped due to --max-delete limit (%zu skipped)",
+                  budget.skipped);
+    } else {
+      log_message(LOG_LEVEL_ERROR,
+                  "Deletions stopped due to the server deletion limit of %u (%zu skipped)",
+                  (unsigned)MAX_SERVER_DELETE_COUNT, budget.skipped);
+    }
+    return DELETE_COMMIT_LIMIT_REACHED;
+  }
+  return DELETE_COMMIT_OK;
+}

src/shared/delete_commit.h

@@ -0,0 +1,113 @@
+#ifndef DELETE_COMMIT_H
+#define DELETE_COMMIT_H
+
+#include "array_list.h"
+#include "config.h"
+#include "delete.h"
+#include "filter.h"
+#include <stdbool.h>
+
+/* Delete-commit module: delete-manifest receive plus the budgeted extras and
+ * --delete-missing-args walkers.  These declarations are re-exported by the
+ * file_receive.h facade. */
+
+/* A received delete-manifest frame: the keep-set (`keeps`, destination-relative
+   paths the sender transferred/keeps) plus `protected`, destination-relative
+   prefixes the sender asks the receiver never to delete (paths excluded on the
+   source, protected at any depth).  When --delete-excluded is given the sender
+   transmits an empty protected list so excluded destination mirrors are treated
+   as ordinary extras.  With --delete-missing-args a third section (`missing`)
+   carries the destination mirrors of explicitly-listed source entries that do
+   not exist: each is an exact deletion request, independent of the ordinary
+   extras walk (never blocked by the protected prefixes) and processed when the
+   manifest is committed. */
+typedef struct DeleteManifest {
+  ArrayList* keeps;
+  ArrayList* protected;
+  ArrayList* missing;
+  /* Destination-relative paths of the directories the sender synchronized for
+     this run.  The extras walker only removes entries directly inside one of
+     these (the receive root is the "." sentinel); `--files-from` runs therefore
+     leave untransmitted directories and the unlisted parts of listed ones
+     alone, matching rsync's "delete only in synchronized directories". */
+  ArrayList* dirs;
+  /* Per-directory filter rules the sender compiled while scanning (protocol
+     2.30.0), each carrying its owner directory and no-inherit flag.  The
+     receiver evaluates them (deepest before ancestors, then the command-line
+     base rules) against every candidate extra so a destination-only entry that
+     matches ONLY a per-directory `.rsync-filter`/dir-merge rule is shielded.
+     NULL when the sender transmitted none. */
+  FilterRuleList* per_dir_rules;
+} DeleteManifest;
+
+void delete_manifest_free(DeleteManifest* manifest);
+/* Read a delete-manifest frame (protocol 2.23.0): keep count + keeps, then
+   protected count + protected prefixes, then missing count + missing paths,
+   then synchronized-directory count + directory paths (self-delimiting; the
+   leading STATUS_MANIFEST code has been consumed).  Returns an owned
+   DeleteManifest, or NULL after signalling STATUS_ERROR on a malformed frame. */
+DeleteManifest* receive_manifest_entries(int fd);
+/* Remove destination entries under config->receive_root_directory that are not
+   in `manifest` (bounded, all-or-nothing walk; staging-dir, basis-dir and
+   protected-prefix skips).  `--max-delete` and `--force` are honored here.  The
+   caller decides WHEN to run it based on the negotiated delete timing.  Returns
+   false (and the transfer fails) when the deletion cannot be committed. */
+bool manifest_delete_extras(const Config* config, const DeleteManifest* manifest);
+/* --delete-missing-args exact-path deletions: remove each destination mirror
+   in `manifest->missing` (never blocked by the protected prefixes, staging dir
+   and basis dirs excluded).  A regular file/symlink is unlinked; an empty
+   directory is removed; a NON-empty directory is removed recursively only when
+   --delete or --force is in effect, otherwise it is left with a warning (rsync
+   parity).  A missing path is a no-op.  Returns false only on a genuine
+   confinement or I/O error (the run then fails); tolerated per-path cases are
+   reported and skipped. */
+bool manifest_delete_missing_args(const Config* config, const DeleteManifest* manifest);
+/* Budgeted form of manifest_delete_missing_args for the per-directory delete
+   session: each removed mirror draws from `max_delete` (SIZE_MAX = unlimited)
+   and the tallies are accumulated into `*deleted`/`*skipped`.  `*limit_hit` is set
+   when the budget stopped the pass with entries left over.  Returns false only
+   on a genuine deletion error. */
+bool manifest_delete_missing_args_limited(const Config* config, const DeleteManifest* manifest,
+                                          size_t max_delete, size_t* deleted, size_t* skipped,
+                                          bool* limit_hit);
+/* Observer-aware form of manifest_delete_missing_args_limited: `observer` (may
+   be NULL) is invoked for every destination-relative path truly removed. */
+bool manifest_delete_missing_args_limited_observed(
+    const Config* config, const DeleteManifest* manifest, size_t max_delete, size_t* deleted,
+    size_t* skipped, bool* limit_hit, DeletePathObserver observer, void* observer_context);
+/* Outcome of committing a delete manifest.  LIMIT_REACHED reports rsync's
+   partial --max-delete result: the budget allowed some deletions and the rest
+   were skipped (the run still stores all file data but the client exits 25). */
+typedef enum {
+  DELETE_COMMIT_OK = 0,
+  DELETE_COMMIT_LIMIT_REACHED,
+  DELETE_COMMIT_ERROR
+} DeleteCommitResult;
+
+/* Run every deletion family the manifest carries: the --delete-missing-args
+   exact-path deletions first (user requests are not blocked by exclusion
+   protection), then the ordinary extras walk when --delete is active.  Both
+   share one --max-delete budget.  Returns DELETE_COMMIT_OK when nothing was to
+   do or everything committed, DELETE_COMMIT_LIMIT_REACHED when the budget
+   stopped part of the work, or DELETE_COMMIT_ERROR on a genuine failure. */
+DeleteCommitResult manifest_delete_all(const Config* config, const DeleteManifest* manifest);
+/* Like manifest_delete_all, but reports how many destination entries the commit
+   removed (for the end-of-transfer wire stats).  `deleted` may be NULL. */
+DeleteCommitResult manifest_delete_all_counted(const Config* config, const DeleteManifest* manifest,
+                                               size_t* deleted);
+/* Observer-aware form of manifest_delete_all_counted: `observer` (may be NULL)
+   is invoked for every destination-relative path truly removed. */
+DeleteCommitResult manifest_delete_all_observed(const Config* config,
+                                                const DeleteManifest* manifest, size_t* deleted,
+                                                DeletePathObserver observer,
+                                                void* observer_context);
+
+/* -n/--dry-run --delete would-delete reporting: walk the destination exactly as
+   the delete pass would and append (strdup'd) destination-relative paths that
+   WOULD be removed to `out`, without touching disk.  Uses the same staging-dir,
+   basis-dir and protected-prefix skips as the real commit.  Returns true on a
+   clean walk; `*count_out` receives the number of paths appended. */
+bool manifest_would_delete_list(const Config* config, const DeleteManifest* manifest,
+                                ArrayList* out, size_t* count_out);
+
+#endif

src/shared/delete_plan.c

@@ -2,6 +2,7 @@
 
 #include "charset.h"
 #include "delay_updates.h"
+#include "delete.h"
 #include "file.h"
 #include "log.h"
 #include "utils.h"
@@ -47,6 +48,7 @@ struct DeletePlanSender {
   const ArrayList* protected_prefixes;
   const ArrayList* size_skipped;
   const ArrayList* missing_args;
+  const FilterRuleList* per_dir_rules;
   size_t entries;
   /* Transmitted FILE entries only.  The caller's "empty scan" safety guard keys
      off this (an I/O error that hid every file must refuse to delete even when
@@ -283,12 +285,14 @@ bool delete_plan_sender_empty(const DeletePlanSender* sender) {
 }
 
 void delete_plan_sender_set_config(DeletePlanSender* sender, const ArrayList* protected_prefixes,
-                                   const ArrayList* size_skipped, const ArrayList* missing_args) {
+                                   const ArrayList* size_skipped, const ArrayList* missing_args,
+                                   const FilterRuleList* per_dir_rules) {
   if (!sender)
     return;
   sender->protected_prefixes = protected_prefixes;
   sender->size_skipped = size_skipped;
   sender->missing_args = missing_args;
+  sender->per_dir_rules = per_dir_rules;
 }
 
 /* True when `dir` is `root` itself or a descendant of it (path-component
@@ -319,6 +323,181 @@ static int send_str_section(int fd, const ArrayList* list) {
   return 0;
 }
 
+/* The directory a rule belongs to (its owner, or the transfer root for ""). */
+static const char* filter_dir_rule_owner(const FilterRule* rule) {
+  return (rule && rule->owner) ? rule->owner : "";
+}
+
+/* Transmit the received-side per-directory filter rules (protocol 2.30.0) as a
+ * self-describing list of directory groups: a group count, then for each group
+ * the relative owner directory followed by that directory's rule records (run
+ * order = the sender's traversal/rule order).  Rules of one directory are
+ * appended to the sink contiguously, so runs reproduce the compilation order.
+ * Bounded by MAX_FILTER_RULES / MAX_FILTER_BYTES and MAX_PROTECT_PATTERN_LEN so
+ * the peer never sees a frame it would reject.  The sender enforces exactly the
+ * receiver's limits (including the cumulative owner+pattern byte budget) and
+ * fails with a clear local error instead of emitting a frame that would abort
+ * the transfer with STATUS_ERROR. */
+bool delete_filter_dir_rules_send(int fd, const FilterRuleList* rules) {
+  int count = rules ? rules->count : 0;
+  if (count < 0 || count > MAX_FILTER_RULES) {
+    log_message(LOG_LEVEL_ERROR, "too many per-directory filter rules: %d (maximum %d)", count,
+                MAX_FILTER_RULES);
+    return false;
+  }
+  size_t bytes = 0;
+  for (int i = 0; i < count; i++) {
+    const FilterRule* rule = rules->items[i];
+    const char* owner = filter_dir_rule_owner(rule);
+    size_t owner_len = strlen(owner);
+    size_t pattern_len = rule && rule->pattern ? strlen(rule->pattern) : 0;
+    if (!rule || !rule->pattern || pattern_len == 0) {
+      log_message(LOG_LEVEL_ERROR, "invalid per-directory filter pattern");
+      return false;
+    }
+    if (pattern_len > MAX_PROTECT_PATTERN_LEN) {
+      log_message(LOG_LEVEL_ERROR,
+                  "per-directory filter pattern exceeds %d bytes (use a shorter pattern)",
+                  MAX_PROTECT_PATTERN_LEN);
+      return false;
+    }
+    if (!(owner_len == 0 || (owner[0] != '/' && !has_path_traversal(owner)))) {
+      log_message(LOG_LEVEL_ERROR, "invalid per-directory filter owner directory");
+      return false;
+    }
+    if (owner_len + pattern_len > MAX_FILTER_BYTES - bytes) {
+      log_message(LOG_LEVEL_ERROR, "per-directory filter rules exceed %d bytes", MAX_FILTER_BYTES);
+      return false;
+    }
+    bytes += owner_len + pattern_len;
+  }
+  int groups = 0;
+  for (int i = 0; i < count;) {
+    const char* owner = filter_dir_rule_owner(rules->items[i]);
+    groups++;
+    i++;
+    while (i < count && strcmp(filter_dir_rule_owner(rules->items[i]), owner) == 0)
+      i++;
+  }
+  if (!send_int(fd, groups))
+    return false;
+  for (int i = 0; i < count;) {
+    const char* owner = filter_dir_rule_owner(rules->items[i]);
+    int start = i;
+    i++;
+    while (i < count && strcmp(filter_dir_rule_owner(rules->items[i]), owner) == 0)
+      i++;
+    if (!send_wire_str(fd, owner) || !send_int(fd, i - start))
+      return false;
+    for (int j = start; j < i; j++) {
+      const FilterRule* rule = rules->items[j];
+      if (!send_int(fd, (int)rule->action) || !send_int(fd, (int)rule->sides) ||
+          !send_int(fd, rule->anchored ? 1 : 0) || !send_int(fd, rule->dir_only ? 1 : 0) ||
+          !send_int(fd, rule->negate ? 1 : 0) || !send_int(fd, rule->no_inherit ? 1 : 0) ||
+          !send_wire_str(fd, rule->pattern))
+        return false;
+    }
+  }
+  return true;
+}
+
+/* Read one wire flag (an int restricted to 0/1). */
+static bool receive_flag(int fd, bool* value) {
+  int raw;
+  if (!receive_int(fd, &raw) || (raw != 0 && raw != 1))
+    return false;
+  *value = raw != 0;
+  return true;
+}
+
+/* Read the per-directory filter block emitted by delete_filter_dir_rules_send.
+ * Reconstructs a flat FilterRuleList whose rules carry their owner directory;
+ * `*out` is NULL when the sender transmitted no rules.  Every bound is enforced
+ * (group/rule counts, owner/pattern bytes, pattern length, action/sides domain)
+ * so a malicious peer can neither overread nor allocate unboundedly.  Returns
+ * false on a malformed frame (the caller signals STATUS_ERROR). */
+bool delete_filter_dir_rules_receive(int fd, FilterRuleList** out) {
+  if (!out)
+    return false;
+  *out = NULL;
+  int groups;
+  if (!receive_int(fd, &groups) || groups < 0 || groups > MAX_FILTER_RULES)
+    return false;
+  if (groups == 0)
+    return true;
+  FilterRuleList* list = filter_rule_list_create();
+  if (!list)
+    return false;
+  int total_rules = 0;
+  size_t bytes = 0;
+  for (int g = 0; g < groups; g++) {
+    char* dir = receive_wire_str(fd);
+    if (!dir)
+      goto fail;
+    size_t dir_bytes = strlen(dir);
+    if (!(dir[0] == '\0' || (dir[0] != '/' && !has_path_traversal(dir))) ||
+        dir_bytes > MAX_FILTER_BYTES - bytes) {
+      free(dir);
+      goto fail;
+    }
+    bytes += dir_bytes;
+    int rule_count;
+    if (!receive_int(fd, &rule_count) || rule_count < 0 || rule_count > MAX_FILTER_RULES ||
+        rule_count > MAX_FILTER_RULES - total_rules) {
+      free(dir);
+      goto fail;
+    }
+    for (int r = 0; r < rule_count; r++) {
+      int action, sides;
+      bool anchored, dir_only, negate, no_inherit;
+      if (!receive_int(fd, &action) ||
+          (action != FILTER_ACTION_EXCLUDE && action != FILTER_ACTION_INCLUDE) ||
+          !receive_int(fd, &sides) || sides < (int)FILTER_SIDE_SENDER ||
+          sides > (int)(FILTER_SIDE_SENDER | FILTER_SIDE_RECEIVER) ||
+          !receive_flag(fd, &anchored) || !receive_flag(fd, &dir_only) ||
+          !receive_flag(fd, &negate) || !receive_flag(fd, &no_inherit)) {
+        free(dir);
+        goto fail;
+      }
+      char* pattern = receive_wire_str(fd);
+      size_t pattern_bytes = pattern ? strlen(pattern) : 0;
+      if (!pattern || pattern_bytes == 0 || pattern_bytes > MAX_PROTECT_PATTERN_LEN ||
+          pattern_bytes > MAX_FILTER_BYTES - bytes) {
+        free(pattern);
+        free(dir);
+        goto fail;
+      }
+      bytes += pattern_bytes;
+      FilterRule* rule = calloc(1, sizeof(FilterRule));
+      if (!rule) {
+        free(pattern);
+        free(dir);
+        goto fail;
+      }
+      rule->action = (FilterAction)action;
+      rule->sides = (unsigned)sides;
+      rule->anchored = anchored;
+      rule->dir_only = dir_only;
+      rule->negate = negate;
+      rule->no_inherit = no_inherit;
+      rule->owner = str_dup(dir);
+      rule->pattern = pattern;
+      if (!rule->owner || !filter_rule_list_add(list, rule)) {
+        filter_rule_free(rule);
+        free(dir);
+        goto fail;
+      }
+      total_rules++;
+    }
+    free(dir);
+  }
+  *out = list;
+  return true;
+fail:
+  filter_rule_list_free(list);
+  return false;
+}
+
 static int send_plan_node(int fd, DeletePlanSender* sender, PlanNode* node) {
   if (!send_status(fd, STATUS_DELETE_PLAN))
     return -1;
@@ -327,7 +506,8 @@ static int send_plan_node(int fd, DeletePlanSender* sender, PlanNode* node) {
   if (!sender->config_sent) {
     if (send_str_section(fd, sender->protected_prefixes) != 0 ||
         send_str_section(fd, sender->size_skipped) != 0 ||
-        send_str_section(fd, sender->missing_args) != 0)
+        send_str_section(fd, sender->missing_args) != 0 ||
+        !delete_filter_dir_rules_send(fd, sender->per_dir_rules))
       return -1;
     sender->config_sent = true;
   }
@@ -354,7 +534,8 @@ static int send_config_only(int fd, DeletePlanSender* sender) {
     return -1;
   if (send_str_section(fd, sender->protected_prefixes) != 0 ||
       send_str_section(fd, sender->size_skipped) != 0 ||
-      send_str_section(fd, sender->missing_args) != 0)
+      send_str_section(fd, sender->missing_args) != 0 ||
+      !delete_filter_dir_rules_send(fd, sender->per_dir_rules))
     return -1;
   sender->config_sent = true;
   if (!send_int(fd, 0)) /* apply = false */
@@ -432,6 +613,17 @@ int delete_plan_send_remaining(int fd, DeletePlanSender* sender, const ArrayList
   return 0;
 }
 
+int delete_plan_send_all(int fd, DeletePlanSender* sender, const ArrayList* dirs) {
+  if (!sender)
+    return -1;
+  /* Root first: this also transmits the one-shot per-run config block on its
+     own carrier frame (see send_config_only), so it reaches the receiver even
+     when the scope permits no directory plan at all. */
+  if (delete_plan_send_root(fd, sender) != 0)
+    return -1;
+  return delete_plan_send_remaining(fd, sender, dirs);
+}
+
 /* ------------------------------------------------------------------ */
 /* Receiver: delete session                                           */
 /* ------------------------------------------------------------------ */
@@ -460,15 +652,37 @@ struct DeletePlanSession {
   ArrayList* protected_prefixes;
   ArrayList* size_skipped;
   ArrayList* missing;
+  /* Received per-directory filter rules (protocol 2.30.0), or NULL.  Evaluated
+     deepest-directory-first for every candidate extra so a destination-only
+     entry matching only a per-directory rule is protected. */
+  FilterRuleList* per_dir_rules;
   ArrayList* deferred;
   DeletePathObserver observer;
   void* observer_context;
 };
 
 /* Report one path the session truly removed (no-op without an observer). */
-static void notify_deleted(DeletePlanSession* session, const char* rel) {
+static void notify_deleted(DeletePlanSession* session, const char* rel, DeleteEntryType type) {
   if (session && session->observer && rel)
-    session->observer(session->observer_context, rel);
+    session->observer(session->observer_context, rel, type);
+}
+
+/* A removed directory is reported with rsync's trailing slash (`deleting dir/`)
+   while files keep their bare path. */
+static void notify_deleted_dir(DeletePlanSession* session, const char* rel) {
+  if (!session || !session->observer || !rel)
+    return;
+  size_t len = strlen(rel);
+  char* with_slash = malloc(len + 2);
+  if (!with_slash) {
+    session->observer(session->observer_context, rel, DELETE_ENTRY_DIR);
+    return;
+  }
+  memcpy(with_slash, rel, len);
+  with_slash[len] = '/';
+  with_slash[len + 1] = '\0';
+  session->observer(session->observer_context, with_slash, DELETE_ENTRY_DIR);
+  free(with_slash);
 }
 
 DeletePlanSession* delete_plan_session_create(const Config* config) {
@@ -502,6 +716,7 @@ void delete_plan_session_destroy(DeletePlanSession* session) {
   array_list_delete(session->protected_prefixes);
   array_list_delete(session->size_skipped);
   array_list_delete(session->missing);
+  filter_rule_list_free(session->per_dir_rules);
   array_list_delete(session->deferred);
   free(session);
 }
@@ -572,51 +787,26 @@ static int open_plan_dir(const Config* config, const char* dir) {
   return fd;
 }
 
-typedef struct PlanSkips {
-  DeleteSkipEntry* entries;
-  int count;
-  /* Receiver-side delete-protection rules received on the config frame (NULL
-     when the sender sent none).  Evaluated per extra so a protect/risk rule is
+typedef struct {
+  DeleteSkipSet set;
+  /* Receiver-side delete-protection rules.  `base` is the config-frame
+     command-line set and `dir` the received per-directory set (both NULL when
+     the sender sent none).  Evaluated per extra so a protect/risk rule is
      honored under --delete-during/--delete-delay exactly like the whole-tree
      commit walker. */
-  const FilterRuleList* protect_rules;
+  DeleteProtectRules protect;
 } PlanSkips;
 
 static bool build_plan_skips(const Config* config, const DeletePlanSession* session,
                              PlanSkips* out) {
-  out->entries = NULL;
-  out->count = 0;
-  out->protect_rules = config->protect_rules;
-  int count = (config->delay_updates ? 1 : 0) + config->basis_count +
-              session->protected_prefixes->size + session->size_skipped->size;
-  if (count == 0)
-    return true;
-  out->entries = calloc((size_t)count, sizeof(DeleteSkipEntry));
-  if (!out->entries)
-    return false;
-  int idx = 0;
-  if (config->delay_updates) {
-    out->entries[idx].prefix = DELAY_UPDATES_STAGING_DIR;
-    out->entries[idx].top_level_only = true;
-    idx++;
-  }
-  for (int i = 0; i < config->basis_count; i++) {
-    out->entries[idx].prefix = config->basis_dirs[i].path;
-    out->entries[idx].top_level_only = false;
-    idx++;
-  }
-  for (int i = 0; i < session->protected_prefixes->size; i++) {
-    out->entries[idx].prefix = (const char*)session->protected_prefixes->items[i];
-    out->entries[idx].top_level_only = false;
-    idx++;
-  }
-  for (int i = 0; i < session->size_skipped->size; i++) {
-    out->entries[idx].prefix = (const char*)session->size_skipped->items[i];
-    out->entries[idx].top_level_only = false;
-    idx++;
-  }
-  out->count = idx;
-  return true;
+  out->protect.base_rules = config->protect_rules;
+  out->protect.dir_rules = session->per_dir_rules;
+  out->protect.backup_suffix = delete_backup_suffix(config);
+  /* The per-directory plan walk keeps each basis path verbatim (it does not
+     convert an absolute under-root path to its root-relative form, unlike the
+     whole-tree commit walk). */
+  return delete_skips_build(config, session->protected_prefixes, session->size_skipped, false,
+                            &out->set);
 }
 
 static bool budget_available(const DeletePlanSession* session) {
@@ -696,7 +886,7 @@ static bool process_extra_dir(int dirfd, const char* name, const char* child_rel
     session->deleted++;
     session->planned++;
     log_deleted(child_rel);
-    notify_deleted(session, child_rel);
+    notify_deleted_dir(session, child_rel);
     *removed = true;
     return true;
   }
@@ -709,8 +899,8 @@ static bool process_extra_dir(int dirfd, const char* name, const char* child_rel
   return errno == ENOTEMPTY || errno == EEXIST;
 }
 
-static bool process_extra_file(int dirfd, const char* name, const char* child_rel, bool force_now,
-                               DeletePlanSession* session) {
+static bool process_extra_file(int dirfd, const char* name, const char* child_rel, mode_t mode,
+                               bool force_now, DeletePlanSession* session) {
   if (session->defer && !force_now) {
     return defer_add(session, child_rel);
   }
@@ -722,7 +912,7 @@ static bool process_extra_file(int dirfd, const char* name, const char* child_re
     session->deleted++;
     session->planned++;
     log_deleted(child_rel);
-    notify_deleted(session, child_rel);
+    notify_deleted(session, child_rel, delete_entry_type_of_mode(mode));
   } else if (errno != ENOENT) {
     return false;
   }
@@ -733,81 +923,107 @@ static bool process_children(int dirfd, const char* dir_rel, const ArrayList* ke
                              const ArrayList* keep_files, bool at_root, bool force_now,
                              const PlanSkips* skips, DeletePlanSession* session, bool* survives) {
   *survives = false;
-  int scanfd = openat(dirfd, ".", O_RDONLY | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
-  if (scanfd < 0)
+  DeleteDirEntry* entries = NULL;
+  size_t count = 0;
+  bool collect_ok = true;
+  if (!delete_dir_entries_collect(dirfd, &entries, &count, &collect_ok))
     return false;
-  DIR* dir = fdopendir(scanfd);
-  if (!dir) {
-    close(scanfd);
+  bool operation_ok = collect_ok;
+  bool local_survives = false;
+  bool* shielded = calloc(count ? count : 1, sizeof(bool));
+  bool* is_extra = calloc(count ? count : 1, sizeof(bool));
+  bool* force = calloc(count ? count : 1, sizeof(bool));
+  if (!shielded || !is_extra || !force) {
+    free(shielded);
+    free(is_extra);
+    free(force);
+    delete_dir_entries_free(entries, count);
     return false;
   }
-  bool operation_ok = true;
-  bool local_survives = false;
-  const struct dirent* entry;
-  while ((entry = readdir(dir)) != NULL) {
-    if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
-      continue;
+
+  /* rsync's order: extraneous subdirectories in descending name order, then
+     extraneous files in descending name order (kept entries survive and are not
+     touched here — a kept subdirectory gets its own per-directory plan). */
+  if (count > 1)
+    qsort(entries, count, sizeof(*entries), delete_dir_entry_cmp_desc);
+  size_t dir_count = 0;
+  while (dir_count < count && entries[dir_count].is_dir)
+    dir_count++;
+
+  for (size_t i = 0; i < count; i++) {
     char* child_rel =
-        (strcmp(dir_rel, ".") == 0) ? str_dup(entry->d_name) : path_cat(dir_rel, entry->d_name);
+        (strcmp(dir_rel, ".") == 0) ? str_dup(entries[i].name) : path_cat(dir_rel, entries[i].name);
     if (!child_rel) {
       operation_ok = false;
       continue;
     }
-    if (path_under_skip_prefix(child_rel, at_root, skips->entries, skips->count)) {
+    if (path_under_skip_prefix(child_rel, at_root, skips->set.entries, skips->set.count)) {
+      shielded[i] = true;
       local_survives = true;
       free(child_rel);
       continue;
     }
-    struct stat st;
-    if (fstatat(dirfd, entry->d_name, &st, AT_SYMLINK_NOFOLLOW) != 0) {
-      if (errno != ENOENT)
-        operation_ok = false;
-      free(child_rel);
-      continue;
-    }
-    bool is_dir = S_ISDIR(st.st_mode);
-    bool in_keep_dirs = is_dir && list_contains_str(keep_dirs, entry->d_name);
-    bool in_keep_files = !is_dir && list_contains_str(keep_files, entry->d_name);
-    bool rule_protected =
-        skips->protect_rules &&
-        filter_rules_apply_side(skips->protect_rules, child_rel, entry->d_name, is_dir,
-                                FILTER_SIDE_RECEIVER) == FILTER_ACTION_PROTECT;
-    if (in_keep_dirs) {
+    bool is_dir = entries[i].is_dir;
+    bool in_keep_dirs = is_dir && list_contains_str(keep_dirs, entries[i].name);
+    bool in_keep_files = !is_dir && list_contains_str(keep_files, entries[i].name);
+    bool rule_protected = delete_protect_verdict(&skips->protect, child_rel, entries[i].name,
+                                                 is_dir) == FILTER_ACTION_PROTECT;
+    if (in_keep_dirs || in_keep_files || rule_protected) {
+      shielded[i] = true;
       local_survives = true;
-    } else if (keep_dirs && !is_dir && list_contains_str(keep_dirs, entry->d_name)) {
-      /* Destination file blocks a source directory: clear it now, whatever the
-         delete timing, so the directory can be created. */
-      if (!process_extra_file(dirfd, entry->d_name, child_rel, true, session))
-        operation_ok = false;
-    } else if (in_keep_files) {
-      local_survives = true;
-    } else if (keep_files && is_dir && list_contains_str(keep_files, entry->d_name)) {
-      /* Destination directory blocks a source file: remove it now. */
-      bool removed = false;
-      if (!process_extra_dir(dirfd, entry->d_name, child_rel, true, skips, session, &removed))
-        operation_ok = false;
-      else if (!removed)
-        local_survives = true;
     } else if (is_dir) {
-      if (rule_protected) {
-        local_survives = true;
-      } else {
-        bool removed = false;
-        if (!process_extra_dir(dirfd, entry->d_name, child_rel, force_now, skips, session,
-                               &removed))
-          operation_ok = false;
-        else if (!removed)
-          local_survives = true;
-      }
-    } else if (rule_protected) {
-      local_survives = true;
+      /* A destination directory blocks a source file of the same name: remove
+         it now, whatever the delete timing, so the file can be created. */
+      is_extra[i] = true;
+      force[i] = keep_files && list_contains_str(keep_files, entries[i].name);
     } else {
-      if (!process_extra_file(dirfd, entry->d_name, child_rel, force_now, session))
-        operation_ok = false;
+      /* A destination file blocks a source directory of the same name: clear it
+         now so the directory can be created. */
+      is_extra[i] = true;
+      force[i] = keep_dirs && list_contains_str(keep_dirs, entries[i].name);
     }
     free(child_rel);
   }
-  closedir(dir);
+
+  /* Pass 1: extraneous subdirectories, descending. */
+  for (size_t i = 0; i < dir_count; i++) {
+    if (!is_extra[i])
+      continue;
+    char* child_rel =
+        (strcmp(dir_rel, ".") == 0) ? str_dup(entries[i].name) : path_cat(dir_rel, entries[i].name);
+    if (!child_rel) {
+      operation_ok = false;
+      continue;
+    }
+    bool removed = false;
+    if (!process_extra_dir(dirfd, entries[i].name, child_rel, force[i] || force_now, skips, session,
+                           &removed))
+      operation_ok = false;
+    else if (!removed)
+      local_survives = true;
+    free(child_rel);
+  }
+
+  /* Pass 2: extraneous files, descending. */
+  for (size_t i = dir_count; i < count; i++) {
+    if (!is_extra[i])
+      continue;
+    char* child_rel =
+        (strcmp(dir_rel, ".") == 0) ? str_dup(entries[i].name) : path_cat(dir_rel, entries[i].name);
+    if (!child_rel) {
+      operation_ok = false;
+      continue;
+    }
+    if (!process_extra_file(dirfd, entries[i].name, child_rel, entries[i].mode,
+                            force[i] || force_now, session))
+      operation_ok = false;
+    free(child_rel);
+  }
+
+  free(shielded);
+  free(is_extra);
+  free(force);
+  delete_dir_entries_free(entries, count);
   *survives = local_survives;
   return operation_ok;
 }
@@ -827,7 +1043,7 @@ static bool apply_plan_dir(DeletePlanSession* session, const Config* config, con
   bool survives = false;
   bool ok = process_children(dirfd, dir, dirs, files, strcmp(dir, ".") == 0, false, &skips, session,
                              &survives);
-  free(skips.entries);
+  delete_skips_free(&skips.set);
   close(dirfd);
   if (!ok)
     log_message(LOG_LEVEL_ERROR, "deletion failed while removing extraneous files");
@@ -873,7 +1089,8 @@ int delete_plan_session_receive(DeletePlanSession* session, const Config* config
   if (has_config) {
     if (session->config_seen || !read_section(fd, session->protected_prefixes, true, &bytes) ||
         !read_section(fd, session->size_skipped, true, &bytes) ||
-        !read_section(fd, session->missing, true, &bytes)) {
+        !read_section(fd, session->missing, true, &bytes) ||
+        !delete_filter_dir_rules_receive(fd, &session->per_dir_rules)) {
       send_status(fd, STATUS_ERROR);
       return -1;
     }
@@ -932,10 +1149,11 @@ static bool apply_deferred_path(DeletePlanSession* session, const Config* config
     return false;
   char* leaf = NULL;
   int parent_fd = file_open_secure_parent(full, &leaf, false);
+  int open_errno = errno;
   free(full);
   if (parent_fd < 0) {
     free(leaf);
-    return errno == ENOENT || errno == ENOTDIR;
+    return open_errno == ENOENT || open_errno == ENOTDIR;
   }
   struct stat st;
   if (fstatat(parent_fd, leaf, &st, AT_SYMLINK_NOFOLLOW) != 0) {
@@ -967,7 +1185,7 @@ static bool apply_deferred_path(DeletePlanSession* session, const Config* config
     }
     bool survives = false;
     bool ok = process_children(dirfd, rel, NULL, NULL, false, true, &skips, session, &survives);
-    free(skips.entries);
+    delete_skips_free(&skips.set);
     close(dirfd);
     if (!ok) {
       close(parent_fd);
@@ -981,7 +1199,7 @@ static bool apply_deferred_path(DeletePlanSession* session, const Config* config
         session->deleted++;
         session->planned++;
         log_deleted(rel);
-        notify_deleted(session, rel);
+        notify_deleted_dir(session, rel);
       } else if (errno != ENOENT && errno != ENOTEMPTY && errno != EEXIST) {
         close(parent_fd);
         free(leaf);
@@ -1002,7 +1220,7 @@ static bool apply_deferred_path(DeletePlanSession* session, const Config* config
     session->deleted++;
     session->planned++;
     log_deleted(rel);
-    notify_deleted(session, rel);
+    notify_deleted(session, rel, delete_entry_type_of_mode(st.st_mode));
   } else if (errno != ENOENT) {
     close(parent_fd);
     free(leaf);

src/shared/delete_plan.h

@@ -3,6 +3,7 @@
 
 #include "array_list.h"
 #include "config.h"
+#include "delete.h"
 #include "file_receive.h"
 #include "protocol.h"
 #include "utils.h"
@@ -24,6 +25,19 @@
  * --delete-missing-args exact deletions, the shared --max-delete budget and,
  * for --delete-delay, the snapshotted extras. */
 
+/* Per-directory filter-rule block (protocol 2.30.0).  The sender compiles the
+ * source's per-directory merge rules as it scans and streams them so the
+ * receiver can re-derive the receiver-side protect/risk verdicts for
+ * destination-only entries.  The wire format is a group count, then for each
+ * directory group its relative owner path followed by that directory's rule
+ * records (action, sides, anchored, dir-only, negate, no-inherit, pattern).
+ * All bounds (MAX_FILTER_RULES, MAX_FILTER_BYTES, MAX_PROTECT_PATTERN_LEN) are
+ * enforced on both sides; a malformed receive frame signals STATUS_ERROR and
+ * returns false.  Receive yields a flat FilterRuleList whose rules carry their
+ * owner, or NULL when no rules were sent. */
+bool delete_filter_dir_rules_send(int fd, const FilterRuleList* rules);
+bool delete_filter_dir_rules_receive(int fd, FilterRuleList** out);
+
 /* ---- Sender: plan builder ---- */
 
 typedef struct DeletePlanSender DeletePlanSender;
@@ -52,7 +66,8 @@ bool delete_plan_sender_empty(const DeletePlanSender* sender);
  * block is always transmitted by delete_plan_send_root(), on a config-only
  * carrier frame when the scope allows no directory plan. */
 void delete_plan_sender_set_config(DeletePlanSender* sender, const ArrayList* protected_prefixes,
-                                   const ArrayList* size_skipped, const ArrayList* missing_args);
+                                   const ArrayList* size_skipped, const ArrayList* missing_args,
+                                   const FilterRuleList* per_dir_rules);
 /* Send the root plan (even before any data, so root extras are handled like
  * rsync's first generator directory), after transmitting the per-run config
  * block on its own carrier frame.  Returns -1 on I/O error. */
@@ -61,9 +76,19 @@ int delete_plan_send_root(int fd, DeletePlanSender* sender);
  * for `path` itself; already-sent plans are skipped. */
 int delete_plan_send_for_path(int fd, DeletePlanSender* sender, const char* path, bool is_dir);
 /* Send the plan for every directory in `dirs` that has not been transmitted
- * yet.  Called after the data stream so an empty source directory's plan still
- * clears its destination extras even though no file frame triggered it. */
+ * yet. */
 int delete_plan_send_remaining(int fd, DeletePlanSender* sender, const ArrayList* dirs);
+/* Transmit the COMPLETE per-directory plan set in one pass, before any data
+ * frame: the root plan (with the one-shot per-run config block on its carrier
+ * frame) followed by every directory in `dirs`.  Because the whole plan set is
+ * known from the path-only pre-scan, sending it all up front means a
+ * mid-transfer abort has already applied every planned removal, matching
+ * rsync's generator (which runs ahead of its throttled sender).  A completed
+ * run is unaffected.  `dirs` is the set of directories whose direct children
+ * were enumerated (the scanner's plan_dirs sink), so a merely listed but
+ * untraversed directory never gets a plan and its mirror is left intact.
+ * Returns -1 on I/O error. */
+int delete_plan_send_all(int fd, DeletePlanSender* sender, const ArrayList* dirs);
 
 /* ---- Receiver: delete session ---- */
 

src/shared/delta.c

@@ -1,10 +1,12 @@
 #include "delta.h"
 #include "log.h"
 #include "protocol.h"
+#include <errno.h>
 #include <stdint.h>
 #include <limits.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 
 #define XXH_STATIC_LINKING_ONLY
 #define XXH_IMPLEMENTATION
@@ -82,6 +84,64 @@ DeltaSignature* delta_signature_create_seeded(const void* old_file_data, uint64_
   return sig;
 }
 
+/* Bounded read of exactly `len` bytes at `off`; retries on EINTR. */
+static bool pread_all(int fd, void* buf, size_t len, uint64_t off) {
+  uint8_t* p = buf;
+  size_t done = 0;
+  while (done < len) {
+    ssize_t n = pread(fd, p + done, len - done, (off_t)(off + done));
+    if (n < 0 && errno == EINTR)
+      continue;
+    if (n <= 0)
+      return false;
+    done += (size_t)n;
+  }
+  return true;
+}
+
+DeltaSignature* delta_signature_create_fd_seeded(int fd, uint64_t old_file_size,
+                                                 uint32_t block_size, uint32_t seed) {
+  if (fd < 0 || old_file_size == 0 || block_size == 0 || block_size > DELTA_BLOCK_SIZE_MAX ||
+      old_file_size > UINT32_MAX * (uint64_t)block_size)
+    return NULL;
+  uint32_t block_count = (uint32_t)((old_file_size + block_size - 1) / block_size);
+  /* Bound the signature's own memory (block_count * sizeof(DeltaBlockSig)). */
+  if (block_count == 0 || block_count > MAX_DELTA_BLOCKS)
+    return NULL;
+  DeltaSignature* sig = protocol_alloc(sizeof(DeltaSignature));
+  if (!sig)
+    return NULL;
+  sig->file_size = old_file_size;
+  sig->block_size = block_size;
+  sig->block_count = block_count;
+  sig->blocks = protocol_alloc((size_t)block_count * sizeof(DeltaBlockSig));
+  if (!sig->blocks) {
+    free(sig);
+    return NULL;
+  }
+  uint8_t* block = malloc(block_size);
+  if (!block) {
+    free(sig->blocks);
+    free(sig);
+    return NULL;
+  }
+  for (uint32_t i = 0; i < block_count; i++) {
+    uint64_t offset = (uint64_t)i * block_size;
+    uint32_t len =
+        (uint32_t)((old_file_size - offset < block_size) ? (old_file_size - offset) : block_size);
+    if (!pread_all(fd, block, len, offset)) {
+      free(block);
+      free(sig->blocks);
+      free(sig);
+      return NULL;
+    }
+    sig->blocks[i].adler32 = delta_adler32(block, len);
+    sig->blocks[i].xxhash = delta_xxhash32_seeded(block, len, seed);
+  }
+  free(block);
+  return sig;
+}
+
 Data* delta_signature_serialize(const DeltaSignature* sig) {
   if (!sig)
     return NULL;
@@ -687,6 +747,130 @@ void* delta_apply(const void* old_data, uint64_t old_size, const Delta* delta,
   return output;
 }
 
+void* delta_apply_fd(int src_fd, uint64_t old_size, const Delta* delta, uint32_t block_size) {
+  if (!delta || block_size == 0 || block_size > DELTA_BLOCK_SIZE_MAX ||
+      (delta->instruction_count > 0 && !delta->instructions) || delta->new_file_size == 0 ||
+      delta->new_file_size > SIZE_MAX)
+    return NULL;
+
+  void* output = protocol_alloc((size_t)delta->new_file_size);
+  if (!output)
+    return NULL;
+
+  uint8_t* out = (uint8_t*)output;
+  uint64_t out_pos = 0;
+
+  for (uint32_t i = 0; i < delta->instruction_count; i++) {
+    if (delta->instructions[i].type == DELTA_INSTR_BLOCK_MATCH) {
+      uint64_t src_offset = (uint64_t)delta->instructions[i].match.block_index * block_size;
+      if (src_offset > UINT64_MAX - delta->instructions[i].match.block_offset) {
+        free(output);
+        return NULL;
+      }
+      src_offset += delta->instructions[i].match.block_offset;
+      uint32_t len = delta->instructions[i].match.length;
+
+      if (src_offset > old_size || (uint64_t)len > old_size - src_offset ||
+          out_pos > delta->new_file_size || (uint64_t)len > delta->new_file_size - out_pos) {
+        free(output);
+        return NULL;
+      }
+      if (!pread_all(src_fd, out + out_pos, len, src_offset)) {
+        free(output);
+        return NULL;
+      }
+      out_pos += len;
+    } else if (delta->instructions[i].type == DELTA_INSTR_LITERAL) {
+      uint32_t len = delta->instructions[i].literal.length;
+      if (out_pos > delta->new_file_size || (uint64_t)len > delta->new_file_size - out_pos) {
+        free(output);
+        return NULL;
+      }
+      memcpy(out + out_pos, delta->instructions[i].literal.data, len);
+      out_pos += len;
+    } else {
+      free(output);
+      return NULL;
+    }
+  }
+
+  if (out_pos != delta->new_file_size) {
+    free(output);
+    return NULL;
+  }
+  return output;
+}
+
+bool delta_apply_to_fd(const void* old_data, int src_fd, uint64_t old_size, const Delta* delta,
+                       uint32_t block_size, int dst_fd) {
+  if (!delta || (old_data == NULL && src_fd < 0) || block_size == 0 ||
+      block_size > DELTA_BLOCK_SIZE_MAX || (delta->instruction_count > 0 && !delta->instructions))
+    return false;
+  const int chunk = 1 << 20;
+  uint8_t* buf = malloc((size_t)chunk);
+  if (!buf)
+    return false;
+  uint64_t out_pos = 0;
+  bool ok = true;
+  for (uint32_t i = 0; i < delta->instruction_count && ok; i++) {
+    uint64_t src_offset = 0;
+    uint64_t len = 0;
+    const uint8_t* lit = NULL;
+    if (delta->instructions[i].type == DELTA_INSTR_BLOCK_MATCH) {
+      src_offset = (uint64_t)delta->instructions[i].match.block_index * block_size;
+      if (src_offset > UINT64_MAX - delta->instructions[i].match.block_offset ||
+          src_offset + delta->instructions[i].match.block_offset > old_size) {
+        ok = false;
+        break;
+      }
+      src_offset += delta->instructions[i].match.block_offset;
+      len = delta->instructions[i].match.length;
+      if (len > old_size - src_offset) {
+        ok = false;
+        break;
+      }
+    } else if (delta->instructions[i].type == DELTA_INSTR_LITERAL) {
+      lit = delta->instructions[i].literal.data;
+      len = delta->instructions[i].literal.length;
+    } else {
+      ok = false;
+      break;
+    }
+    if (out_pos > delta->new_file_size || len > delta->new_file_size - out_pos) {
+      ok = false;
+      break;
+    }
+    uint64_t done = 0;
+    while (ok && done < len) {
+      size_t want = (len - done) < (uint64_t)chunk ? (size_t)(len - done) : (size_t)chunk;
+      if (lit) {
+        memcpy(buf, lit + done, want);
+      } else if (old_data) {
+        memcpy(buf, (const uint8_t*)old_data + src_offset + done, want);
+      } else if (!pread_all(src_fd, buf, want, src_offset + done)) {
+        ok = false;
+        break;
+      }
+      const uint8_t* p = buf;
+      size_t written = 0;
+      while (written < want) {
+        ssize_t n = write(dst_fd, p + written, want - written);
+        if (n < 0 && errno == EINTR)
+          continue;
+        if (n <= 0) {
+          ok = false;
+          break;
+        }
+        written += (size_t)n;
+      }
+      done += want;
+    }
+    out_pos += len;
+  }
+  free(buf);
+  return ok && out_pos == delta->new_file_size;
+}
+
 void delta_destroy(Delta* delta) {
   if (!delta)
     return;

src/shared/delta.h

@@ -61,6 +61,13 @@ DeltaSignature* delta_signature_create(const void* old_file_data, uint64_t old_f
  * identical to the unseeded function. */
 DeltaSignature* delta_signature_create_seeded(const void* old_file_data, uint64_t old_file_size,
                                               uint32_t block_size, uint32_t seed);
+/* Streaming equivalent of delta_signature_create_seeded: reads the basis blocks
+ * from `fd` in bounded chunks, so an arbitrarily large basis can be signed
+ * without materializing it.  The signature itself is bounded (MAX_DELTA_BLOCKS
+ * entries); an over-large basis returns NULL and the caller falls back to a
+ * whole-file transfer. */
+DeltaSignature* delta_signature_create_fd_seeded(int fd, uint64_t old_file_size,
+                                                 uint32_t block_size, uint32_t seed);
 Data* delta_signature_serialize(const DeltaSignature* sig);
 DeltaSignature* delta_signature_deserialize(const Data* data);
 void delta_signature_destroy(DeltaSignature* sig);
@@ -75,6 +82,15 @@ Delta* delta_compute_seeded(const void* new_file_data, uint64_t new_file_size,
 Data* delta_serialize(const Delta* delta);
 Delta* delta_deserialize(const Data* data);
 void* delta_apply(const void* old_data, uint64_t old_size, const Delta* delta, uint32_t block_size);
+/* Streaming equivalent of delta_apply: matched blocks are read from `src_fd` as
+ * they are emitted, so the basis never has to be resident. */
+void* delta_apply_fd(int src_fd, uint64_t old_size, const Delta* delta, uint32_t block_size);
+/* Fully streamed reconstruction: matched blocks come from `old_data` (when
+ * non-NULL) or are read from `src_fd`, and the reconstructed bytes are written
+ * straight to `dst_fd` in bounded chunks, so a reconstructed file larger than
+ * memory is never materialized. */
+bool delta_apply_to_fd(const void* old_data, int src_fd, uint64_t old_size, const Delta* delta,
+                       uint32_t block_size, int dst_fd);
 void delta_destroy(Delta* delta);
 
 bool delta_should_attempt(uint64_t old_size, uint64_t new_size, uint64_t max_file_size);

src/shared/file.c

@@ -16,6 +16,8 @@
 
 #include "data.h"
 #include "checksum.h"
+#include "chunk.h"
+#include "compression.h"
 #include "delta.h"
 #include "file.h"
 #include "file_store.h"
@@ -25,13 +27,6 @@
 #include "utils.h"
 #include "protocol.h"
 #include "xattr.h"
-#include <fcntl.h>
-#include <unistd.h>
-
-/* Files larger than this are not loaded whole for transfer (the sender streams
- * them); a whole-file digest is computed from the path instead.  Kept in sync
- * with the sender's streaming threshold. */
-#define STREAM_THRESHOLD (64ULL * 1024 * 1024)
 
 static bool write_all(int fd, const void* data, unsigned long long size) {
   const unsigned char* p = data;
@@ -216,6 +211,7 @@ File* file_create(const char* path) {
   file->dir_time_only = false;
   file->basis_link = NULL;
   file->basis_copy = NULL;
+  file->data_spool = false;
   file->link_group = 0;
   file->link_first = false;
   file->hardlink_target = NULL;
@@ -245,8 +241,11 @@ void file_destroy(void* item) {
   file->send_path = NULL;
   free(file->basis_link);
   file->basis_link = NULL;
+  if (file->data_spool && file->basis_copy)
+    unlink(file->basis_copy);
   free(file->basis_copy);
   file->basis_copy = NULL;
+  file->data_spool = false;
   free(file->hardlink_target);
   file->hardlink_target = NULL;
   free(file->symlink_target);
@@ -388,6 +387,261 @@ size_t file_content_to_buffer(File* file) {
   return bytes_read;
 }
 
+/* ---- Streamed whole-file payload receive ----
+ *
+ * A whole-file data frame is a uint64 length followed by that many bytes.  When
+ * the logical payload is at or below the receiver's streaming bound the
+ * historical charged whole-buffer path is kept (decompressing in one shot for
+ * `-z`).  Above the bound the frame is read in bounded chunks and written into
+ * a spool temp file next to the destination, decompressing incrementally for
+ * zstd/zlib (lz4's block format cannot be streamed and keeps the buffered path).
+ * The spool is then installed by the existing bounded-buffer basis-copy path
+ * (file_copy_basis_stream_attrs), so the atomic temp+rename store, --partial/
+ * --partial-dir, --delay-updates, --preallocate and metadata/xattr application
+ * are all reused unchanged.  Only bounded buffers (64 KiB read chunk + the
+ * decompressor's 256 KiB output window) are ever live. */
+
+#define FILE_PAYLOAD_READ_CHUNK (64 * 1024)
+#define FILE_PAYLOAD_PEEK_MAX 32
+
+/* Create a confined spool temp file in the destination's directory.  Returns an
+ * open write fd and an owned absolute path, or -1 (errno set).  The parent walk
+ * creates missing directories exactly as a normal store would. */
+static int file_spool_create(const char* dest_path, char** out_spool_path) {
+  *out_spool_path = NULL;
+  char* leaf = NULL;
+  int dirfd = file_open_secure_parent(dest_path, &leaf, true);
+  free(leaf);
+  if (dirfd < 0)
+    return -1;
+  char name[64];
+  for (unsigned int i = 0; i < 100; i++) {
+    snprintf(name, sizeof(name), ".fastsync-spool.%ld.%llu", (long)getpid(), next_temp_sequence());
+    int fd = openat(dirfd, name, O_WRONLY | O_CREAT | O_EXCL | O_CLOEXEC | O_NOFOLLOW, 0600);
+    if (fd < 0) {
+      if (errno != EEXIST)
+        break;
+      continue;
+    }
+    char* copy = str_dup(dest_path);
+    const char* dir = copy ? dirname(copy) : NULL;
+    size_t need = dir ? strlen(dir) + 1 + strlen(name) + 1 : 0;
+    char* full = need ? malloc(need) : NULL;
+    if (!full) {
+      free(copy);
+      close(fd);
+      unlinkat(dirfd, name, 0);
+      close(dirfd);
+      return -1;
+    }
+    snprintf(full, need, "%s/%s", dir, name);
+    free(copy);
+    close(dirfd);
+    *out_spool_path = full;
+    return fd;
+  }
+  close(dirfd);
+  return -1;
+}
+
+int file_spool_for_payload(const char* dest_path, char** out_spool_path) {
+  return file_spool_create(dest_path, out_spool_path);
+}
+
+bool file_receive_payload(int fd, bool compress, unsigned long long expected_size,
+                          const char* dest_path, unsigned long long stream_limit, Data** out_buffer,
+                          char** out_spool, unsigned long long* out_size) {
+  if (out_buffer)
+    *out_buffer = NULL;
+  if (out_spool)
+    *out_spool = NULL;
+  if (out_size)
+    *out_size = 0;
+  if (!out_buffer || !out_spool || !out_size || !dest_path)
+    return false;
+
+  unsigned long long frame_size = 0;
+  if (!receive_n_data(fd, &frame_size, sizeof(frame_size)))
+    return false;
+  /* A frame larger than MAX_DATA_PAYLOAD_SIZE is allowed only on the streamed
+     path, which never materializes it; the buffered path's
+     receive_data_alloc/body enforces the historical bound itself.  Only a size
+     unrepresentable on this platform is rejected here. */
+  if (frame_size > SIZE_MAX) {
+    log_message(LOG_LEVEL_ERROR, "Data size %llu is not representable", frame_size);
+    return false;
+  }
+
+  unsigned char prefix[FILE_PAYLOAD_PEEK_MAX];
+  size_t prefix_len = 0;
+  bool stream;
+  if (expected_size != 0) {
+    /* The check frame already told us the logical size: no need to peek. */
+    stream = expected_size > stream_limit;
+  } else if (!compress) {
+    stream = frame_size > stream_limit;
+  } else {
+    /* Non-incremental compressed frame with unknown logical size: peek the
+       header to decide, so a small compressed frame that expands past the bound
+       still streams instead of allocating the whole logical image. */
+    size_t want = frame_size < sizeof(prefix) ? (size_t)frame_size : sizeof(prefix);
+    if (want > 0 && !receive_n_data(fd, prefix, want))
+      return false;
+    prefix_len = want;
+    unsigned long long logical = compression_peek_frame_content_size(prefix, prefix_len);
+    stream = logical != 0 ? logical > stream_limit : frame_size > stream_limit;
+  }
+
+  if (!stream) {
+    Data* frame;
+    if (prefix_len > 0) {
+      frame = receive_data_alloc(fd, frame_size);
+      if (!frame)
+        return false;
+      memcpy(frame->data, prefix, prefix_len);
+      if (frame_size > prefix_len &&
+          !receive_n_data(fd, (char*)frame->data + prefix_len, (size_t)(frame_size - prefix_len))) {
+        data_destroy(frame);
+        return false;
+      }
+    } else {
+      frame = receive_data_body(fd, frame_size);
+      if (!frame)
+        return false;
+    }
+    if (compress) {
+      unsigned long long bound =
+          expected_size != 0 ? expected_size : (unsigned long long)MAX_RECEIVE_WHOLE_FILE_SIZE;
+      Data* uncompressed = data_decompress_limited(frame, (size_t)bound);
+      ProtocolSession* owner = frame->owner;
+      data_destroy(frame);
+      if (!uncompressed)
+        return false;
+      if (expected_size != 0 && uncompressed->size != expected_size) {
+        data_destroy(uncompressed);
+        return false;
+      }
+      if (!data_charge_session(uncompressed, owner, uncompressed->size)) {
+        data_destroy(uncompressed);
+        return false;
+      }
+      *out_buffer = uncompressed;
+      *out_size = uncompressed->size;
+      return true;
+    }
+    *out_buffer = frame;
+    *out_size = frame->size;
+    return true;
+  }
+
+  /* Streamed path. */
+  int spool_fd = file_spool_create(dest_path, out_spool);
+  if (spool_fd < 0)
+    return false;
+
+  CompressionStreamDecompressor* dec = NULL;
+  size_t header_len = 0;
+  unsigned long long learned_size = expected_size;
+  if (compress) {
+    unsigned char hdr[1 + 4];
+    size_t hdr_have = 0;
+    if (prefix_len >= 1) {
+      hdr[0] = prefix[0];
+      hdr_have = 1;
+    } else {
+      if (!receive_n_data(fd, hdr, 1))
+        goto stream_fail;
+      hdr_have = 1;
+    }
+    CompressionAlgo algo = (CompressionAlgo)hdr[0];
+    if (!compression_algo_valid((int)algo) || algo == COMPRESSION_ALGO_LZ4)
+      goto stream_fail;
+    header_len = (algo == COMPRESSION_ALGO_ZLIB || algo == COMPRESSION_ALGO_ZLIBX) ? 5 : 1;
+    while (hdr_have < header_len) {
+      size_t need = header_len - hdr_have;
+      if (prefix_len > hdr_have) {
+        size_t avail = prefix_len - hdr_have;
+        size_t take = avail < need ? avail : need;
+        memcpy(hdr + hdr_have, prefix + hdr_have, take);
+        hdr_have += take;
+      } else {
+        if (!receive_n_data(fd, hdr + hdr_have, need))
+          goto stream_fail;
+        hdr_have = header_len;
+      }
+    }
+    if (header_len == 5) {
+      uint32_t raw = 0;
+      for (int i = 0; i < 4; i++)
+        raw |= (uint32_t)hdr[1 + i] << (8 * i);
+      if (expected_size != 0 && raw != expected_size)
+        goto stream_fail;
+      if (learned_size == 0)
+        learned_size = raw;
+    }
+    dec = compression_stream_decompressor_create(algo, learned_size);
+    if (!dec)
+      goto stream_fail;
+  }
+
+  if (frame_size < header_len)
+    goto stream_fail;
+  {
+    unsigned long long body_remaining = frame_size - header_len;
+    if (prefix_len > header_len) {
+      size_t avail = prefix_len - header_len;
+      if (compress) {
+        bool done = false;
+        if (!compression_stream_decompressor_feed(dec, prefix + header_len, avail, spool_fd, &done))
+          goto stream_fail;
+      } else if (!write_all(spool_fd, prefix + header_len, avail)) {
+        goto stream_fail;
+      }
+      body_remaining -= avail;
+    }
+    unsigned char buf[FILE_PAYLOAD_READ_CHUNK];
+    while (body_remaining > 0) {
+      size_t want = body_remaining < sizeof(buf) ? (size_t)body_remaining : (size_t)sizeof(buf);
+      if (!receive_n_data(fd, buf, want))
+        goto stream_fail;
+      if (compress) {
+        bool done = false;
+        if (!compression_stream_decompressor_feed(dec, buf, want, spool_fd, &done))
+          goto stream_fail;
+      } else if (!write_all(spool_fd, buf, want)) {
+        goto stream_fail;
+      }
+      body_remaining -= want;
+    }
+  }
+
+  {
+    unsigned long long total = compress ? compression_stream_decompressor_total(dec) : frame_size;
+    if (learned_size != 0 && total != learned_size)
+      goto stream_fail;
+    *out_size = total;
+  }
+  if (dec)
+    compression_stream_decompressor_destroy(dec);
+  if (close(spool_fd) != 0) {
+    spool_fd = -1;
+    goto stream_fail;
+  }
+  return true;
+
+stream_fail:
+  if (dec)
+    compression_stream_decompressor_destroy(dec);
+  if (spool_fd >= 0)
+    close(spool_fd);
+  if (*out_spool) {
+    unlink(*out_spool);
+    free(*out_spool);
+    *out_spool = NULL;
+  }
+  return false;
+}
+
 /* ---- Secure filesystem primitives ---- */
 
 bool file_path_exists_secure(const char* path) {
@@ -1136,17 +1390,51 @@ int file_open_private_dir(const char* dir_path) {
   return fd;
 }
 
-/* Open a --temp-dir scratch directory exactly as rsync does: the directory must
- * already exist and is used as given (an absolute path is used verbatim, a
- * relative one was already resolved against the destination root by the
- * caller).  Unlike file_open_private_dir this neither creates it nor confines
- * it below the receive root, because rsync accepts any temp dir -- including
- * one outside the destination tree or on another filesystem.  Returns an
- * O_DIRECTORY|O_CLOEXEC fd, or -1 on error. */
+/* Open a --temp-dir scratch directory.  The directory must already exist (rsync
+ * never creates it); a relative path was already resolved against the
+ * destination root by the caller.  Unlike file_open_private_dir this neither
+ * creates it nor requires it to be a direct child of the receive root, because
+ * rsync permits a scratch dir that (via a symlink) lands on another filesystem
+ * -- but it MUST resolve inside the authorized receive root.  The directory is
+ * opened following symlinks and then judged by the REAL path of the opened fd
+ * (through /proc/self/fd), so a client-planted symlink under the receive root
+ * can never redirect receiver scratch files outside the sandbox while an
+ * in-root link to another filesystem (the EXDEV fallback case) still works.
+ * Returns an O_DIRECTORY|O_CLOEXEC fd, or -1 on error (errno set; an escaping
+ * target is reported as EACCES with a logged reason). */
 int file_open_temp_dir(const char* dir_path) {
   if (!dir_path)
     return -1;
-  return open(dir_path, O_RDONLY | O_DIRECTORY | O_CLOEXEC);
+  int fd = open(dir_path, O_RDONLY | O_DIRECTORY | O_CLOEXEC);
+  if (fd < 0)
+    return -1;
+  const char* root = utils_get_authorized_root_path();
+  if (!root) {
+    /* No authorized root (e.g. a local batch apply): nothing to confine
+       against, so preserve the historical open-as-given behavior. */
+    return fd;
+  }
+  char fd_path[64];
+  int fd_path_length = snprintf(fd_path, sizeof(fd_path), "/proc/self/fd/%d", fd);
+  char resolved[PATH_MAX];
+  if (fd_path_length < 0 || (size_t)fd_path_length >= sizeof(fd_path) ||
+      !realpath(fd_path, resolved)) {
+    int saved_errno = errno;
+    close(fd);
+    errno = saved_errno;
+    return -1;
+  }
+  if (!path_is_within_root(root, resolved)) {
+    char* escaped = output_escape(dir_path, log_get_8_bit_output());
+    log_message(LOG_LEVEL_ERROR,
+                "--temp-dir '%s' resolves outside the authorized receive root; refusing",
+                escaped ? escaped : "<allocation failed>");
+    free(escaped);
+    close(fd);
+    errno = EACCES;
+    return -1;
+  }
+  return fd;
 }
 
 /* After the content and mode/times are restored on the just-written file, apply
@@ -1155,21 +1443,24 @@ int file_open_temp_dir(const char* dir_path) {
  * destination file) and best-effort: a per-attribute or privilege failure is
  * logged and skipped, never fatal. */
 static void restore_extra_fd(int fd, const FileMetadata* metadata, const FileXattrList* xattrs,
-                             bool fake_super, FileAttrPolicy policy) {
+                             bool fake_super, FileAttrPolicy policy, uint32_t fake_super_rdev_major,
+                             uint32_t fake_super_rdev_minor) {
   xattr_apply_fd(fd, xattrs);
   if (fake_super && metadata) {
     /* Record the ownership that WOULD have been applied: when an explicit
        ownership request (--chown/--usermap/--groupmap/--copy-as or -o/-g) is
        active, the resolved mapping; otherwise the source's own id.  The real
        chown is suppressed (identity_apply_ownership early-returns under
-       --fake-super) so recording never defeats the flag.  Mode/mtime are still
-       replayed (policy-gated) so unprivileged --fake-super keeps working. */
+       --fake-super) so recording never defeats the flag.  The recorded stat is
+       rsync's format; the permission bits are replayed (policy-gated) so
+       unprivileged --fake-super keeps working while mtime comes from the
+       normal metadata path above. */
     uint32_t store_uid;
     uint32_t store_gid;
     identity_resolve_storage_ids((int32_t)metadata->uid, (int32_t)metadata->gid, &store_uid,
                                  &store_gid);
-    fake_super_store_fd(fd, store_uid, store_gid, (uint32_t)metadata->mode, metadata->mtime_sec,
-                        metadata->mtime_nsec);
+    fake_super_store_fd(fd, store_uid, store_gid, (uint32_t)metadata->mode, fake_super_rdev_major,
+                        fake_super_rdev_minor);
     fake_super_restore_fd(fd, policy);
   }
 }
@@ -1179,7 +1470,8 @@ file_to_disk_secure_impl(const char* path, const void* data, unsigned long long
                          bool inplace, bool sparse, bool preallocate, const FileMetadata* metadata,
                          FileAttrPolicy policy, bool update, bool no_replace, bool use_fsync,
                          const char* temp_dir, const FileXattrList* xattrs, bool fake_super,
-                         bool keep_partial, unsigned* dirs_created, const char* count_floor) {
+                         bool keep_partial, unsigned* dirs_created, const char* count_floor,
+                         uint32_t fake_super_rdev_major, uint32_t fake_super_rdev_minor) {
   char* leaf = NULL;
   int dirfd = file_open_secure_parent_counted(path, &leaf, true, dirs_created, count_floor);
   if (dirfd < 0)
@@ -1286,7 +1578,8 @@ file_to_disk_secure_impl(const char* path, const void* data, unsigned long long
             }
           }
           if (ok)
-            restore_extra_fd(fd, metadata, xattrs, fake_super, policy);
+            restore_extra_fd(fd, metadata, xattrs, fake_super, policy, fake_super_rdev_major,
+                             fake_super_rdev_minor);
           if (ok && use_fsync)
             ok = fsync(fd) == 0;
         }
@@ -1404,7 +1697,8 @@ file_to_disk_secure_impl(const char* path, const void* data, unsigned long long
           }
         }
         if (ok)
-          restore_extra_fd(fd, metadata, xattrs, fake_super, policy);
+          restore_extra_fd(fd, metadata, xattrs, fake_super, policy, fake_super_rdev_major,
+                           fake_super_rdev_minor);
         if (ok && use_fsync)
           ok = fsync(fd) == 0;
       }
@@ -1472,7 +1766,8 @@ file_to_disk_secure_impl(const char* path, const void* data, unsigned long long
                 "non-atomic copy into the destination directory");
     return file_to_disk_secure_impl(path, data, data_size, inplace, sparse, preallocate, metadata,
                                     policy, update, no_replace, use_fsync, NULL, xattrs, fake_super,
-                                    keep_partial, dirs_created, count_floor);
+                                    keep_partial, dirs_created, count_floor, fake_super_rdev_major,
+                                    fake_super_rdev_minor);
   }
   return ok;
 }
@@ -1482,7 +1777,7 @@ bool file_to_disk_secure(const char* path, const void* data, unsigned long long
                          FileAttrPolicy policy, const char* temp_dir) {
   return file_to_disk_secure_impl(path, data, data_size, inplace, sparse, preallocate, metadata,
                                   policy, false, false, false, temp_dir, NULL, false, false, NULL,
-                                  NULL);
+                                  NULL, 0, 0);
 }
 
 bool file_to_disk_secure_update(const char* path, const void* data, unsigned long long data_size,
@@ -1491,7 +1786,7 @@ bool file_to_disk_secure_update(const char* path, const void* data, unsigned lon
                                 const char* temp_dir) {
   return file_to_disk_secure_impl(path, data, data_size, inplace, sparse, preallocate, metadata,
                                   policy, true, false, false, temp_dir, NULL, false, false, NULL,
-                                  NULL);
+                                  NULL, 0, 0);
 }
 
 bool file_to_disk_secure_with_fsync(const char* path, const void* data,
@@ -1500,7 +1795,7 @@ bool file_to_disk_secure_with_fsync(const char* path, const void* data,
                                     FileAttrPolicy policy, bool use_fsync, const char* temp_dir) {
   return file_to_disk_secure_impl(path, data, data_size, inplace, sparse, preallocate, metadata,
                                   policy, false, false, use_fsync, temp_dir, NULL, false, false,
-                                  NULL, NULL);
+                                  NULL, NULL, 0, 0);
 }
 
 bool file_to_disk_secure_no_replace(const char* path, const void* data,
@@ -1509,7 +1804,7 @@ bool file_to_disk_secure_no_replace(const char* path, const void* data,
                                     const char* temp_dir) {
   return file_to_disk_secure_impl(path, data, data_size, false, sparse, preallocate, metadata,
                                   policy, false, true, false, temp_dir, NULL, false, false, NULL,
-                                  NULL);
+                                  NULL, 0, 0);
 }
 
 /* Receiver write-path variant that also applies the per-file xattrs (-X/-A)
@@ -1524,19 +1819,19 @@ bool file_to_disk_secure_attrs(const char* path, const void* data, unsigned long
                                bool fake_super, bool keep_partial, const char* temp_dir) {
   return file_to_disk_secure_attrs_counted(path, data, data_size, inplace, sparse, preallocate,
                                            metadata, policy, update, no_replace, use_fsync, xattrs,
-                                           fake_super, keep_partial, temp_dir, NULL, NULL);
+                                           fake_super, keep_partial, temp_dir, NULL, NULL, 0, 0);
 }
 
-bool file_to_disk_secure_attrs_counted(const char* path, const void* data,
-                                       unsigned long long data_size, bool inplace, bool sparse,
-                                       bool preallocate, const FileMetadata* metadata,
-                                       FileAttrPolicy policy, bool update, bool no_replace,
-                                       bool use_fsync, const FileXattrList* xattrs, bool fake_super,
-                                       bool keep_partial, const char* temp_dir,
-                                       unsigned* dirs_created, const char* count_floor) {
+bool file_to_disk_secure_attrs_counted(
+    const char* path, const void* data, unsigned long long data_size, bool inplace, bool sparse,
+    bool preallocate, const FileMetadata* metadata, FileAttrPolicy policy, bool update,
+    bool no_replace, bool use_fsync, const FileXattrList* xattrs, bool fake_super,
+    bool keep_partial, const char* temp_dir, unsigned* dirs_created, const char* count_floor,
+    uint32_t fake_super_rdev_major, uint32_t fake_super_rdev_minor) {
   return file_to_disk_secure_impl(path, data, data_size, inplace, sparse, preallocate, metadata,
                                   policy, update, no_replace, use_fsync, temp_dir, xattrs,
-                                  fake_super, keep_partial, dirs_created, count_floor);
+                                  fake_super, keep_partial, dirs_created, count_floor,
+                                  fake_super_rdev_major, fake_super_rdev_minor);
 }
 
 /* Atomic --link-dest install.  The destination is replaced (via a temporary
@@ -1666,7 +1961,7 @@ static bool file_copy_basis_stream_impl(const char* path, const char* basis_path
         wrote = false;
       }
       if (wrote)
-        restore_extra_fd(fd, metadata, xattrs, fake_super, policy);
+        restore_extra_fd(fd, metadata, xattrs, fake_super, policy, 0, 0);
       if (wrote && use_fsync)
         wrote = fsync(fd) == 0;
       if (close(fd) != 0)
@@ -1815,7 +2110,7 @@ static bool file_to_disk_secure_link_impl(const char* path, const char* basis_pa
       return true;
     return file_to_disk_secure_attrs_counted(
         path, data, data_size, false, false, preallocate, metadata, policy, false, false, use_fsync,
-        xattrs, fake_super, false, temp_dir, dirs_created, count_floor);
+        xattrs, fake_super, false, temp_dir, dirs_created, count_floor, 0, 0);
   }
 
   if (scratch_dirfd >= 0)
@@ -1859,6 +2154,6 @@ bool file_write_to_disk(const char* path, const void* data, unsigned long long d
                         bool inplace, bool sparse) {
   if (!path || (!data && data_size != 0) || has_path_traversal(path))
     return false;
-  FileAttrPolicy policy = {false, false, false, false};
+  FileAttrPolicy policy = {0};
   return file_to_disk_secure(path, data, data_size, inplace, sparse, false, NULL, policy, NULL);
 }

src/shared/file.h

@@ -103,8 +103,12 @@ bool file_remove_tree_secure(const char* path);
    the authorized root.  Used for the --delay-updates staging directory. */
 int file_open_private_dir(const char* dir_path);
 
-/* Open an existing --temp-dir scratch directory as-is (absolute or relative;
-   no creation, no root confinement), matching rsync's --temp-dir handling. */
+/* Open an existing --temp-dir scratch directory (relative or absolute; no
+   creation).  When an authorized receive root is configured the directory's
+   REAL path (symlinks resolved) must lie within it, so a client-planted
+   symlink cannot redirect receiver scratch files outside the sandbox; an
+   in-root symlink to another filesystem is still allowed for rsync's EXDEV
+   fallback. */
 int file_open_temp_dir(const char* dir_path);
 
 /* The file_to_disk_secure* variants write a temporary copy in the destination
@@ -173,18 +177,35 @@ bool file_copy_basis_stream_attrs(const char* path, const char* basis_path,
                                   const FileMetadata* metadata, FileAttrPolicy policy, bool update,
                                   bool use_fsync, const FileXattrList* xattrs, bool fake_super,
                                   const char* temp_dir);
+/* Receive one length-prefixed whole-file data frame, streaming the payload
+ * through a bounded buffer when it (or its known logical size) exceeds
+ * `stream_limit`.  On success exactly one of *out_buffer / *out_spool is set:
+ *   - *out_buffer: the historical charged whole-buffer Data (caller destroys);
+ *   - *out_spool: an owned temp path holding the payload, installed through the
+ *     File's basis_copy field with File.data_spool set so file_destroy unlinks
+ *     it.  The destination policy/metadata/atomic-store handling is then the
+ *     existing bounded-buffer basis install (file_copy_basis_stream_attrs).
+ * `expected_size` (0 = unknown) is the logical size from the check frame;
+ * `dest_path` locates the spool next to the destination; `compress` selects
+ * incremental decompression.  Returns false on any framing/I/O/size error. */
+bool file_receive_payload(int fd, bool compress, unsigned long long expected_size,
+                          const char* dest_path, unsigned long long stream_limit, Data** out_buffer,
+                          char** out_spool, unsigned long long* out_size);
+/* Create a confined spool temp file next to `dest_path`; returns an open write
+ * fd and an owned absolute path (to be installed via File.basis_copy with
+ * File.data_spool set, and unlinked by file_destroy). */
+int file_spool_for_payload(const char* dest_path, char** out_spool_path);
 /* Protocol 2.28.0 receiver-stat variants: like the two above but additionally
  * report through `dirs_created` (when non-NULL) how many parent directories the
  * confined secure walk had to create that lie strictly below `count_floor` (a
  * receive-root-relative prefix, or NULL for all).  Used to reproduce rsync's
  * `Number of created files` directory count on a fresh destination. */
-bool file_to_disk_secure_attrs_counted(const char* path, const void* data,
-                                       unsigned long long data_size, bool inplace, bool sparse,
-                                       bool preallocate, const FileMetadata* metadata,
-                                       FileAttrPolicy policy, bool update, bool no_replace,
-                                       bool use_fsync, const FileXattrList* xattrs, bool fake_super,
-                                       bool keep_partial, const char* temp_dir,
-                                       unsigned* dirs_created, const char* count_floor);
+bool file_to_disk_secure_attrs_counted(
+    const char* path, const void* data, unsigned long long data_size, bool inplace, bool sparse,
+    bool preallocate, const FileMetadata* metadata, FileAttrPolicy policy, bool update,
+    bool no_replace, bool use_fsync, const FileXattrList* xattrs, bool fake_super,
+    bool keep_partial, const char* temp_dir, unsigned* dirs_created, const char* count_floor,
+    uint32_t fake_super_rdev_major, uint32_t fake_super_rdev_minor);
 bool file_to_disk_secure_link_attrs_counted(const char* path, const char* basis_path,
                                             const void* data, unsigned long long data_size,
                                             bool preallocate, const FileMetadata* metadata,

src/shared/file_attr.h

@@ -29,6 +29,12 @@ typedef struct FileAttrPolicy {
   bool times;         /* config->preserve_times: apply the source mtime */
   bool atimes;        /* config->preserve_atimes (-U): apply the source atime */
   bool executability; /* config->use_executability (-E): exec-bits-only mode */
+  /* privilege_super_mode_permitted(): when false (SUPER_MODE_OFF / --no-super,
+     or a daemon that did not grant `client owner = yes`), the setuid/setgid/
+     sticky bits are stripped from every applied mode (source mode and any
+     --chmod result) even under --perms.  When true, rsync's exact semantics are
+     preserved: -p copies the special bits and the kernel decides. */
+  bool super_permitted;
 } FileAttrPolicy;
 
 /* Build the per-attribute policy from a connection's Config.  A NULL config

src/shared/file_receive.h

@@ -2,11 +2,19 @@
 #define FILE_RECEIVE_H
 
 #include "config.h"
+#include "delete_commit.h"
+#include "file_save.h"
 #include "file_types.h"
+#include "incremental_check.h"
 #include "utils.h"
 #include <stdbool.h>
 
-/* Server-side file receive/save path. */
+/* Server-side file receive/save path.
+ *
+ * This header is the public facade for the file_receive module family: the
+ * wire receive dispatch (this file) plus the save-to-disk (file_save.h), the
+ * incremental check (incremental_check.h) and the delete-commit
+ * (delete_commit.h) modules. */
 
 /* Cumulative caps for the deferred directory-time accumulator.  The sender may
  * legitimately split a large tree across repeated STATUS_DIR_TIMES frames, so a
@@ -23,25 +31,6 @@ File* file_receive_dir_time(int file_descriptor, const Config* config);
 File* file_receive_hardlink(int file_descriptor);
 File* file_receive_symlink(int file_descriptor, const Config* config);
 File* file_receive_special(int file_descriptor);
-bool file_special_rdev_valid(int32_t major, int32_t minor, mode_t mode);
-/* Testable basis quick-check / verification policy.  file_basis_quick_match is
- * rsync's metadata quick-check for a basis candidate (equal size is required
- * separately by the caller; this adds the --size-only / mtime / --modify-window
- * leg).  file_basis_content_required reports whether a hit must ALSO be
- * confirmed by a whole-file content digest (--verify-basis; false is the
- * default rsync-parity behavior). */
-bool file_basis_quick_match(const Config* config, const struct stat* st, time_t check_mtime,
-                            long check_mtime_nsec);
-bool file_basis_content_required(const Config* config);
-
-File* receive_incremental_check(int fd, const Config* config, bool* skipped);
-/* Extended variant used by the receiver.  `would_transfer` (may be NULL) is set
- * true only on the server-contacting --dry-run path when the file is not up to
- * date: the receiver has already sent STATUS_DRY_RUN_TRANSFER and returns NULL
- * without storing anything.  On that path `*skipped` is true for an up-to-date
- * (STATUS_OK) file and both flags are false for a genuine error. */
-File* receive_incremental_check_ex(int fd, const Config* config, bool* skipped,
-                                   bool* would_transfer);
 
 /* P7 Wave D directory-time accumulator.  The receiver collects the metadata of
  * every directory it creates/receives (STATUS_MKDIR with metadata and/or the
@@ -85,126 +74,4 @@ bool dir_time_list_add(DirTimeList* list, const char* wire_path, const FileMetad
 void dir_metadata_list_apply(const DirTimeList* list, const char* root_directory,
                              const Config* config);
 
-/* A received delete-manifest frame: the keep-set (`keeps`, destination-relative
-   paths the sender transferred/keeps) plus `protected`, destination-relative
-   prefixes the sender asks the receiver never to delete (paths excluded on the
-   source, protected at any depth).  When --delete-excluded is given the sender
-   transmits an empty protected list so excluded destination mirrors are treated
-   as ordinary extras.  With --delete-missing-args a third section (`missing`)
-   carries the destination mirrors of explicitly-listed source entries that do
-   not exist: each is an exact deletion request, independent of the ordinary
-   extras walk (never blocked by the protected prefixes) and processed when the
-   manifest is committed. */
-typedef struct DeleteManifest {
-  ArrayList* keeps;
-  ArrayList* protected;
-  ArrayList* missing;
-  /* Destination-relative paths of the directories the sender synchronized for
-     this run.  The extras walker only removes entries directly inside one of
-     these (the receive root is the "." sentinel); `--files-from` runs therefore
-     leave untransmitted directories and the unlisted parts of listed ones
-     alone, matching rsync's "delete only in synchronized directories". */
-  ArrayList* dirs;
-} DeleteManifest;
-
-void delete_manifest_free(DeleteManifest* manifest);
-/* Read a delete-manifest frame (protocol 2.23.0): keep count + keeps, then
-   protected count + protected prefixes, then missing count + missing paths,
-   then synchronized-directory count + directory paths (self-delimiting; the
-   leading STATUS_MANIFEST code has been consumed).  Returns an owned
-   DeleteManifest, or NULL after signalling STATUS_ERROR on a malformed frame. */
-DeleteManifest* receive_manifest_entries(int fd);
-/* Remove destination entries under config->receive_root_directory that are not
-   in `manifest` (bounded, all-or-nothing walk; staging-dir, basis-dir and
-   protected-prefix skips).  `--max-delete` and `--force` are honored here.  The
-   caller decides WHEN to run it based on the negotiated delete timing.  Returns
-   false (and the transfer fails) when the deletion cannot be committed. */
-bool manifest_delete_extras(const Config* config, DeleteManifest* manifest);
-/* --delete-missing-args exact-path deletions: remove each destination mirror
-   in `manifest->missing` (never blocked by the protected prefixes, staging dir
-   and basis dirs excluded).  A regular file/symlink is unlinked; an empty
-   directory is removed; a NON-empty directory is removed recursively only when
-   --delete or --force is in effect, otherwise it is left with a warning (rsync
-   parity).  A missing path is a no-op.  Returns false only on a genuine
-   confinement or I/O error (the run then fails); tolerated per-path cases are
-   reported and skipped. */
-bool manifest_delete_missing_args(const Config* config, DeleteManifest* manifest);
-/* Budgeted form of manifest_delete_missing_args for the per-directory delete
-   session: each removed mirror draws from `max_delete` (SIZE_MAX = unlimited)
-   and the tallies are accumulated into `*deleted`/`*skipped`.  `*limit_hit` is set
-   when the budget stopped the pass with entries left over.  Returns false only
-   on a genuine deletion error. */
-bool manifest_delete_missing_args_limited(const Config* config, DeleteManifest* manifest,
-                                          size_t max_delete, size_t* deleted, size_t* skipped,
-                                          bool* limit_hit);
-/* Observer-aware form of manifest_delete_missing_args_limited: `observer` (may
-   be NULL) is invoked for every destination-relative path truly removed. */
-bool manifest_delete_missing_args_limited_observed(const Config* config, DeleteManifest* manifest,
-                                                   size_t max_delete, size_t* deleted,
-                                                   size_t* skipped, bool* limit_hit,
-                                                   DeletePathObserver observer,
-                                                   void* observer_context);
-/* Outcome of committing a delete manifest.  LIMIT_REACHED reports rsync's
-   partial --max-delete result: the budget allowed some deletions and the rest
-   were skipped (the run still stores all file data but the client exits 25). */
-typedef enum {
-  DELETE_COMMIT_OK = 0,
-  DELETE_COMMIT_LIMIT_REACHED,
-  DELETE_COMMIT_ERROR
-} DeleteCommitResult;
-
-/* Run every deletion family the manifest carries: the --delete-missing-args
-   exact-path deletions first (user requests are not blocked by exclusion
-   protection), then the ordinary extras walk when --delete is active.  Both
-   share one --max-delete budget.  Returns DELETE_COMMIT_OK when nothing was to
-   do or everything committed, DELETE_COMMIT_LIMIT_REACHED when the budget
-   stopped part of the work, or DELETE_COMMIT_ERROR on a genuine failure. */
-DeleteCommitResult manifest_delete_all(const Config* config, DeleteManifest* manifest);
-/* Like manifest_delete_all, but reports how many destination entries the commit
-   removed (for the end-of-transfer wire stats).  `deleted` may be NULL. */
-DeleteCommitResult manifest_delete_all_counted(const Config* config, DeleteManifest* manifest,
-                                               size_t* deleted);
-/* Observer-aware form of manifest_delete_all_counted: `observer` (may be NULL)
-   is invoked for every destination-relative path truly removed. */
-DeleteCommitResult manifest_delete_all_observed(const Config* config, DeleteManifest* manifest,
-                                                size_t* deleted, DeletePathObserver observer,
-                                                void* observer_context);
-
-/* -n/--dry-run --delete would-delete reporting: walk the destination exactly as
-   the delete pass would and append (strdup'd) destination-relative paths that
-   WOULD be removed to `out`, without touching disk.  Uses the same staging-dir,
-   basis-dir and protected-prefix skips as the real commit.  Returns true on a
-   clean walk; `*count_out` receives the number of paths appended. */
-bool manifest_would_delete_list(const Config* config, DeleteManifest* manifest, ArrayList* out,
-                                size_t* count_out);
-/* Convert one basis-directory path to the receive-root-relative protection
-   prefix the delete walker uses (NULL when it lies outside the root).  Exposed
-   for unit tests of the root-of-"/" and normalization edge cases. */
-char* file_receive_basis_delete_relative(const Config* config, const char* path);
-
-/* Outcome of a single file_save_to_disk operation.  The receiver needs to
-   distinguish "written" from "skipped" so --remove-source-files can be told
-   which sources were actually stored. */
-typedef enum { FILE_SAVE_ERROR = 0, FILE_SAVE_WRITTEN = 1, FILE_SAVE_SKIPPED = 2 } FileSaveResult;
-
-FileSaveResult file_save_to_disk_full(const char* root_directory, const File* file,
-                                      const Config* config);
-/* Protocol 2.28.0 variant: also reports through `created` (when non-NULL)
- * whether the destination entry did not exist before this save, and through
- * `created_dirs` how many parent directories the confined walk created, so the
- * receiver can build rsync's `Number of created files` breakdown.  The plain
- * file_save_to_disk_full() is this with both out-params NULL. */
-FileSaveResult file_save_to_disk_full_ex(const char* root_directory, const File* file,
-                                         const Config* config, bool* created,
-                                         unsigned* created_dirs);
-bool file_save_to_disk(const char* root_directory, const File* file, const Config* config);
-
-/* Protocol 2.28.0 receiver counter accumulator: fold one successfully saved
- * entry into `stats`, adding its receiver-observed literal bytes and, when
- * `created`, the matching created-by-type counter (regular file / symlink /
- * special) plus `created_dirs` implicitly-created parent directories.
- * Non-first hardlink siblings contribute no literal bytes. */
-void receiver_stats_note_saved(ReceiverStats* stats, const File* file, bool created,
-                               unsigned created_dirs);
-
 #endif

src/shared/file_save.h

@@ -0,0 +1,48 @@
+#ifndef FILE_SAVE_H
+#define FILE_SAVE_H
+
+#include "config.h"
+#include "file_types.h"
+#include "format.h"
+#include <stdbool.h>
+
+/* Save-to-disk module: regular-file/symlink/hardlink/special install, xattr
+ * application, --fake-super and the --delay-updates staging path.  These
+ * declarations are re-exported by the file_receive.h facade. */
+
+/* Outcome of a single file_save_to_disk operation.  The receiver needs to
+   distinguish "written" from "skipped" so --remove-source-files can be told
+   which sources were actually stored.  FILE_SAVE_FAILED is a per-entry failure
+   (for example a device node that mknodat() refused with EPERM/EACCES): it is
+   logged and counted by the receiver but does NOT abort the transfer, matching
+   rsync's continue-and-exit-partial behavior. */
+typedef enum {
+  FILE_SAVE_ERROR = 0,
+  FILE_SAVE_WRITTEN = 1,
+  FILE_SAVE_SKIPPED = 2,
+  FILE_SAVE_FAILED = 3
+} FileSaveResult;
+
+bool file_special_rdev_valid(int32_t major, int32_t minor, mode_t mode);
+
+FileSaveResult file_save_to_disk_full(const char* root_directory, const File* file,
+                                      const Config* config);
+/* Protocol 2.28.0 variant: also reports through `created` (when non-NULL)
+ * whether the destination entry did not exist before this save, and through
+ * `created_dirs` how many parent directories the confined walk created, so the
+ * receiver can build rsync's `Number of created files` breakdown.  The plain
+ * file_save_to_disk_full() is this with both out-params NULL. */
+FileSaveResult file_save_to_disk_full_ex(const char* root_directory, const File* file,
+                                         const Config* config, bool* created,
+                                         unsigned* created_dirs);
+bool file_save_to_disk(const char* root_directory, const File* file, const Config* config);
+
+/* Protocol 2.28.0 receiver counter accumulator: fold one successfully saved
+ * entry into `stats`, adding its receiver-observed literal bytes and, when
+ * `created`, the matching created-by-type counter (regular file / symlink /
+ * special) plus `created_dirs` implicitly-created parent directories.
+ * Non-first hardlink siblings contribute no literal bytes. */
+void receiver_stats_note_saved(ReceiverStats* stats, const File* file, bool created,
+                               unsigned created_dirs);
+
+#endif

src/shared/file_send.c

@@ -44,12 +44,138 @@ bool file_send_single_calls(File* file, int file_descriptor, bool use_metadata,
                                           send_path, NULL, -1, 0, false);
 }
 
+/* Stream-compress a whole source file into a temp file, then transmit it as the
+ * normal length-prefixed data frame.  Used when the source was too large to
+ * load (File.data.data == NULL): the source is read in bounded chunks through a
+ * streaming codec, so neither the raw nor the compressed image is held in
+ * memory.  The compressed length must be known before the frame is sent (the
+ * wire is length-prefixed), so the stream lands in a private temp file first. */
+bool file_send_compressed_stream_with_skip(File* file, int file_descriptor, bool use_metadata,
+                                           int compression_level, bool send_path,
+                                           char* const* skip_suffixes, int skip_count,
+                                           int compression_threads, bool send_xattrs) {
+  /* The caller has already decided this file compresses; the skip list is part
+     of the public signature for symmetry with the buffered path. */
+  (void)skip_suffixes;
+  (void)skip_count;
+  if (!file || !file->path || !file->data || file->data->size == 0 || file->data->data != NULL)
+    return false;
+  CompressionAlgo algo = compression_get_algo();
+  CompressionStreamCompressor* compressor =
+      compression_stream_compressor_create(algo, compression_level, compression_threads);
+  if (!compressor) {
+    log_message(LOG_LEVEL_ERROR, "streaming compression is not available for this codec; "
+                                 "the source was not loaded for the buffered path");
+    return false;
+  }
+
+  int src = file_open_for_read(file->path);
+  if (src < 0) {
+    compression_stream_compressor_destroy(compressor);
+    return false;
+  }
+  struct stat src_st;
+  if (fstat(src, &src_st) != 0 || !S_ISREG(src_st.st_mode) ||
+      (unsigned long long)src_st.st_size < file->data->size) {
+    close(src);
+    compression_stream_compressor_destroy(compressor);
+    return false;
+  }
+
+  const char* tmpdir = getenv("TMPDIR");
+  if (!tmpdir || tmpdir[0] == '\0')
+    tmpdir = "/tmp";
+  size_t tmplen = strlen(tmpdir) + strlen("/fastsync-z-XXXXXX") + 1;
+  char* tmpl = malloc(tmplen);
+  if (!tmpl) {
+    close(src);
+    compression_stream_compressor_destroy(compressor);
+    return false;
+  }
+  snprintf(tmpl, tmplen, "%s/fastsync-z-XXXXXX", tmpdir);
+  int tmp_fd = mkstemp(tmpl);
+  if (tmp_fd < 0) {
+    log_perror("Could not create compression temp file");
+    free(tmpl);
+    close(src);
+    compression_stream_compressor_destroy(compressor);
+    return false;
+  }
+  unlink(tmpl);
+  free(tmpl);
+
+  bool ok = compression_stream_compressor_begin(compressor, file->data->size, tmp_fd);
+  unsigned char buf[64 * 1024];
+  unsigned long long remaining = file->data->size;
+  while (ok && remaining > 0) {
+    size_t want = remaining < sizeof(buf) ? (size_t)remaining : sizeof(buf);
+    ssize_t got = read(src, buf, want);
+    if (got <= 0) {
+      ok = false;
+      break;
+    }
+    if (!compression_stream_compressor_feed(compressor, buf, (size_t)got, tmp_fd))
+      ok = false;
+    remaining -= (unsigned long long)got;
+  }
+  if (ok)
+    ok = compression_stream_compressor_finish(compressor, tmp_fd);
+  close(src);
+  compression_stream_compressor_destroy(compressor);
+  if (!ok) {
+    close(tmp_fd);
+    return false;
+  }
+  struct stat tmp_st;
+  if (fstat(tmp_fd, &tmp_st) != 0 || tmp_st.st_size < 0) {
+    close(tmp_fd);
+    return false;
+  }
+  unsigned long long compressed_size = (unsigned long long)tmp_st.st_size;
+  if (lseek(tmp_fd, 0, SEEK_SET) == (off_t)-1) {
+    close(tmp_fd);
+    return false;
+  }
+
+  ok = true;
+  if (send_path && !send_wire_str(file_descriptor, file_wire_path(file)))
+    ok = false;
+  if (ok && use_metadata && !metadata_send(file_descriptor, file->metadata))
+    ok = false;
+  if (ok && send_xattrs && !xattr_send(file_descriptor, file ? file->xattrs : NULL))
+    ok = false;
+  if (ok && !send_n_data(file_descriptor, &compressed_size, sizeof(compressed_size)))
+    ok = false;
+  unsigned long long left = compressed_size;
+  while (ok && left > 0) {
+    size_t want = left < sizeof(buf) ? (size_t)left : sizeof(buf);
+    ssize_t got = read(tmp_fd, buf, want);
+    if (got <= 0 || !send_n_data(file_descriptor, buf, (size_t)got)) {
+      ok = false;
+      break;
+    }
+    left -= (unsigned long long)got;
+  }
+  close(tmp_fd);
+  return ok;
+}
+
 bool file_send_single_calls_with_skip(File* file, int file_descriptor, bool use_metadata,
                                       int compression_level, bool send_path,
                                       char* const* skip_suffixes, int skip_count,
                                       int compression_threads, bool send_xattrs) {
-  if (!file || !file->path || !file->data || (file->data->size != 0 && !file->data->data))
+  if (!file || !file->path || !file->data)
     return false;
+  /* A source too large to load is streamed: compression streams through a
+   * temp file, no compression must have taken the sendfile path instead. */
+  if (file->data->size != 0 && file->data->data == NULL) {
+    if (compression_level <= 0 ||
+        compression_should_skip_with_suffixes(file->path, skip_suffixes, skip_count))
+      return false;
+    return file_send_compressed_stream_with_skip(file, file_descriptor, use_metadata,
+                                                 compression_level, send_path, skip_suffixes,
+                                                 skip_count, compression_threads, send_xattrs);
+  }
   const Data* data_to_send = file->data;
   Data* compressed_data = NULL;
   if (compression_level > 0 &&
@@ -124,8 +250,12 @@ bool file_send_sendfile_with_skip(File* file, int file_descriptor, bool use_meta
   }
 
   /* sendfile cannot encrypt TLS records.  Keep the framing identical but
-     route encrypted transfers through the deadline-aware IO layer. */
-  if (io_get_ssl() != NULL) {
+     route encrypted transfers through the deadline-aware IO layer.  Resolve
+     the transport from the bound session, not the thread-local io_ssl: a
+     worker thread running a TLS transfer has its SSL only on the session it
+     bound, so io_get_ssl() would be NULL there and the raw sendfile() path
+     would be taken on an encrypted socket. */
+  if (protocol_current_ssl() != NULL) {
     unsigned char buffer[64 * 1024];
     unsigned long long remaining = file_size;
     bool ok = true;
@@ -166,6 +296,8 @@ bool file_send_sendfile_with_skip(File* file, int file_descriptor, bool use_meta
     }
     struct pollfd pfd = {.fd = file_descriptor, .events = POLLOUT};
     int polled = poll(&pfd, 1, timeout);
+    if (polled < 0 && errno == EINTR)
+      continue;
     if (polled <= 0 || (pfd.revents & (POLLERR | POLLHUP | POLLNVAL))) {
       close(fd);
       return false;
@@ -183,6 +315,7 @@ bool file_send_sendfile_with_skip(File* file, int file_descriptor, bool use_meta
       return false;
     }
     protocol_note_bytes_written((unsigned long long)sent);
+    protocol_throttle_bytes(file_descriptor, (size_t)sent);
   }
 
   close(fd);

src/shared/file_send.h

@@ -13,6 +13,12 @@ bool file_send_single_calls_with_skip(File* file, int file_descriptor, bool use_
                                       int compression_level, bool send_path,
                                       char* const* skip_suffixes, int skip_count,
                                       int compression_threads, bool send_xattrs);
+/* Stream-compress an unloaded whole source file into a temp file and send it as
+ * the usual data frame (see file_send.c). */
+bool file_send_compressed_stream_with_skip(File* file, int file_descriptor, bool use_metadata,
+                                           int compression_level, bool send_path,
+                                           char* const* skip_suffixes, int skip_count,
+                                           int compression_threads, bool send_xattrs);
 bool file_send_sendfile(File* file, int file_descriptor, bool use_metadata, int compression_level,
                         bool send_path);
 bool file_send_sendfile_with_skip(File* file, int file_descriptor, bool use_metadata,

src/shared/file_types.h

@@ -62,6 +62,11 @@ typedef struct {
    * This lets a basis larger than any whole-file bound materialize without
    * buffering it; the source metadata on `metadata` is applied afterwards. */
   char* basis_copy;
+  /* Receiver-only.  When set, `basis_copy` points at a receiver-created spool
+   * temp file holding a STREAMED whole-file payload (rather than a --copy-dest
+   * basis).  file_destroy unlinks it after the install consumes it, so an
+   * over-limit file leaves no scratch behind. */
+  bool data_spool;
   /* --hard-links (-H), sender + receiver wire state.  link_group is a run-local
    * id shared by every member of one source inode (0 = not part of a group).
    * The FIRST member (link_first == true) carries its data on the wire and is

src/shared/filter.c

@@ -4,22 +4,12 @@
 #include <ctype.h>
 #include <errno.h>
 #include <limits.h>
-#include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
-/* Write a diagnostic message into the caller's optional buffer.  A NULL `err`
- * (or a zero size) is a no-op, so a caller that only needs the boolean status
- * may pass NULL without the snprintf-on-NULL undefined behaviour. */
-static void filter_set_error(char* err, size_t err_size, const char* fmt, ...) {
-  if (!err || err_size == 0)
-    return;
-  va_list ap;
-  va_start(ap, fmt);
-  vsnprintf(err, err_size, fmt, ap);
-  va_end(ap);
-}
+/* Write a diagnostic message into the caller's optional buffer. */
+#define filter_set_error utils_set_error
 
 /* ---- Ordered rule lists ---- */
 
@@ -31,6 +21,28 @@ void filter_rule_free(FilterRule* rule) {
   free(rule);
 }
 
+FilterRule* filter_rule_clone(const FilterRule* rule) {
+  if (!rule)
+    return NULL;
+  FilterRule* copy = calloc(1, sizeof(FilterRule));
+  if (!copy)
+    return NULL;
+  copy->action = rule->action;
+  copy->sides = rule->sides;
+  copy->anchored = rule->anchored;
+  copy->dir_only = rule->dir_only;
+  copy->negate = rule->negate;
+  copy->perishable = rule->perishable;
+  copy->no_inherit = rule->no_inherit;
+  copy->owner = str_dup(rule->owner ? rule->owner : "");
+  copy->pattern = str_dup(rule->pattern ? rule->pattern : "");
+  if (!copy->owner || !copy->pattern) {
+    filter_rule_free(copy);
+    return NULL;
+  }
+  return copy;
+}
+
 FilterRuleList* filter_rule_list_create(void) {
   return calloc(1, sizeof(FilterRuleList));
 }
@@ -58,37 +70,94 @@ void filter_rule_list_free(FilterRuleList* list) {
   for (int i = 0; i < list->count; i++)
     filter_rule_free(list->items[i]);
   for (int i = 0; i < list->dir_merge_count; i++)
-    free(list->dir_merge_names[i]);
-  free(list->dir_merge_names);
+    free(list->dir_merges[i].name);
+  free(list->dir_merges);
   free(list->items);
   free(list);
 }
 
+/* Append an implicit exclude rule for the merge file itself (rsync's 'e'
+ * modifier).  The rule is owned by the transfer root and matches the basename
+ * anywhere, exactly like rsync's EXCLUDE_SELF (a dual-sided exclude: it hides
+ * the file and protects its destination mirror from --delete). */
+static bool filter_list_add_exclude_self(FilterRuleList* list, const char* name) {
+  const char* base = strrchr(name, '/');
+  base = base ? base + 1 : name;
+  if (base[0] == '\0')
+    return true;
+  FilterRule* rule = calloc(1, sizeof(FilterRule));
+  if (!rule)
+    return false;
+  rule->action = FILTER_ACTION_EXCLUDE;
+  rule->sides = FILTER_SIDE_SENDER | FILTER_SIDE_RECEIVER;
+  rule->pattern = str_dup(base);
+  if (!rule->pattern || !filter_rule_set_owner(rule, "")) {
+    filter_rule_free(rule);
+    return false;
+  }
+  if (!filter_rule_list_add(list, rule)) {
+    filter_rule_free(rule);
+    return false;
+  }
+  return true;
+}
+
 /* Register a per-directory merge-file basename (for "dir-merge NAME"/": NAME"
  * and -F's .rsync-filter).  Duplicate names are ignored. */
 bool filter_rule_list_add_dir_merge(FilterRuleList* list, const char* name) {
+  return filter_rule_list_add_dir_merge_ex(list, name, false, false, false, false, false);
+}
+
+bool filter_rule_list_add_dir_merge_ex(FilterRuleList* list, const char* name, bool no_prefixes,
+                                       bool include, bool word_split, bool no_inherit,
+                                       bool exclude_self) {
   if (!list || !name || name[0] == '\0')
     return false;
   for (int i = 0; i < list->dir_merge_count; i++) {
-    if (strcmp(list->dir_merge_names[i], name) == 0)
+    if (strcmp(list->dir_merges[i].name, name) == 0) {
+      /* rsync keeps the first registration (first-wins), but the 'e' modifier
+         is a list side effect, not a registration field: honor it on the
+         duplicate path too, adding the implicit exclude-self rule at most
+         once. */
+      if (exclude_self && !list->dir_merges[i].exclude_self) {
+        if (!filter_list_add_exclude_self(list, name))
+          return false;
+        list->dir_merges[i].exclude_self = true;
+      }
       return true;
+    }
   }
   if (list->dir_merge_count == list->dir_merge_capacity) {
+    if (list->dir_merge_capacity > INT_MAX / 2)
+      return false;
     int new_cap = list->dir_merge_capacity > 0 ? list->dir_merge_capacity * 2 : 4;
-    char** grown = realloc(list->dir_merge_names, (size_t)new_cap * sizeof(char*));
+    FilterDirMerge* grown = realloc(list->dir_merges, (size_t)new_cap * sizeof(*grown));
     if (!grown)
       return false;
-    list->dir_merge_names = grown;
+    list->dir_merges = grown;
     list->dir_merge_capacity = new_cap;
   }
   char* dup = str_dup(name);
   if (!dup)
     return false;
-  list->dir_merge_names[list->dir_merge_count++] = dup;
+  if (exclude_self && !filter_list_add_exclude_self(list, name)) {
+    free(dup);
+    return false;
+  }
+  FilterDirMerge* entry = &list->dir_merges[list->dir_merge_count];
+  entry->name = dup;
+  entry->no_prefixes = no_prefixes;
+  entry->include = include;
+  entry->word_split = word_split;
+  entry->no_inherit = no_inherit;
+  entry->exclude_self = exclude_self;
+  list->dir_merge_count++;
   return true;
 }
 
-static bool set_rule_owner(FilterRule* rule, const char* owner) {
+bool filter_rule_set_owner(FilterRule* rule, const char* owner) {
+  if (!rule)
+    return false;
   char* dup = str_dup(owner ? owner : "");
   if (!dup)
     return false;
@@ -172,14 +241,77 @@ static bool is_modifier_char(char c) {
   return c == 's' || c == 'r' || c == 'p' || c == 'x' || c == '/' || c == '!' || c == 'C';
 }
 
+/* merge/dir-merge rules are the only rules rsync accepts the merge-file
+ * modifiers on. */
+static bool is_merge_rule(RuleKind kind) {
+  return kind == RULE_KIND_MERGE || kind == RULE_KIND_DIR_MERGE;
+}
+
+/* Merge-file modifiers rsync defines but FastSync does not implement:
+ * 'e' exclude the merge file itself, 'n' do not inherit the merge file, 'w'
+ * word-split the merge file.  They are recognized as part of a modifier run on
+ * every rule (so a pure e/n/w token is rejected rather than folded into the
+ * pattern), but are accepted (and ignored) only on merge/dir-merge rules. */
+static bool is_unsupported_modifier_char(char c) {
+  return c == 'e' || c == 'n' || c == 'w';
+}
+
+/* Merge-file modifiers rsync accepts on merge/dir-merge rules: 'e' (exclude
+ * self), 'n' (no inherit), 'w' (word split), '-' (bare excludes) and '+'
+ * (bare includes). */
+static bool is_merge_modifier_char(char c) {
+  return c == 'e' || c == 'n' || c == 'w' || c == '-' || c == '+';
+}
+
+/* Characters that count as part of a modifier run for `kind` when deciding
+ * whether a token is a pure modifier run.  e/n/w count on every rule so that a
+ * pure e/n/w token is rejected on non-merge rules; '-' only on merge rules. */
+static bool is_modifier_scan_char(char c, RuleKind kind) {
+  return is_modifier_char(c) || is_unsupported_modifier_char(c) ||
+         (is_merge_rule(kind) && is_merge_modifier_char(c));
+}
+
+/* Characters actually consumed as modifiers for `kind`.  The merge-file
+ * modifiers are consumed only on merge/dir-merge rules; elsewhere e/n/w fall
+ * through to the pattern (so mixed tokens such as "H,!secret" keep their
+ * historical "ecret" pattern). */
+static bool is_consumed_modifier_char(char c, RuleKind kind) {
+  return is_modifier_char(c) || (is_merge_rule(kind) && is_merge_modifier_char(c));
+}
+
+/* Inspect the token that follows a rule name (up to the first space/underscore
+ * or the end).  If the token is composed *solely* of modifier characters and
+ * includes one that is invalid for `kind`, it is unambiguously a modifier run:
+ * return that character so the caller can reject it.  A token that contains any
+ * non-modifier character is a pattern (e.g. "-newfile") and returns '\0', which
+ * keeps the historical parsing of mixed tokens such as "H,!secret" intact. */
+static char unsupported_modifier_in_token(const char* tok, RuleKind kind) {
+  if (*tok == '\0' || *tok == ' ' || *tok == '_')
+    return '\0';
+  char bad = '\0';
+  for (const char* q = tok; *q != '\0' && *q != ' ' && *q != '_'; q++) {
+    if (!is_modifier_scan_char(*q, kind))
+      return '\0';
+    if (!is_merge_rule(kind) && is_unsupported_modifier_char(*q))
+      bad = *q;
+  }
+  return bad;
+}
+
 /* Parse "RULE[,MODIFIERS] [PATTERN]".  On success `kind`, `sides`,
  * `sides_explicit`, `negate`, `anchored_mod`, `perishable`, `xattr`,
  * `cvs_inject` and the pattern span (`pat_start`/`pat_len`, possibly 0 for
- * merge/clear) are filled.  Returns true on success. */
+ * merge/clear) are filled.  Returns true on success.
+ *
+ * On failure `*bad_mod` is set to the offending modifier character when the
+ * rule carried a modifier FastSync does not implement, and left '\0' for a
+ * generic syntax error so callers can emit a precise diagnostic. */
 static bool parse_rule_syntax(const char* text, RuleKind* kind, unsigned* sides,
                               bool* sides_explicit, bool* negate, bool* anchored_mod,
-                              bool* perishable, bool* xattr, bool* cvs_inject,
-                              const char** pat_start, size_t* pat_len) {
+                              bool* perishable, bool* xattr, bool* cvs_inject, bool* no_prefixes,
+                              bool* include_defaults, bool* word_split, bool* no_inherit,
+                              bool* exclude_self, const char** pat_start, size_t* pat_len,
+                              char* bad_mod) {
   const char* p = text;
   *sides = FILTER_SIDE_SENDER | FILTER_SIDE_RECEIVER;
   *sides_explicit = false;
@@ -188,8 +320,14 @@ static bool parse_rule_syntax(const char* text, RuleKind* kind, unsigned* sides,
   *perishable = false;
   *xattr = false;
   *cvs_inject = false;
+  *no_prefixes = false;
+  *include_defaults = false;
+  *word_split = false;
+  *no_inherit = false;
+  *exclude_self = false;
   *pat_start = NULL;
   *pat_len = 0;
+  *bad_mod = '\0';
 
   bool is_short = false;
   if (short_rule_char(*p, kind)) {
@@ -210,17 +348,25 @@ static bool parse_rule_syntax(const char* text, RuleKind* kind, unsigned* sides,
   /* Modifiers: long names require a comma; short names may attach directly.
      Only commit a modifier run that terminates at a separator or the end, so a
      pattern such as "*.tmp" written as "-*.tmp" is not mistaken for modifiers. */
+  if (*p == ',') {
+    *bad_mod = unsupported_modifier_in_token(p + 1, *kind);
+  } else if (is_short) {
+    *bad_mod = unsupported_modifier_in_token(p, *kind);
+  }
+  if (*bad_mod != '\0')
+    return false;
+
   const char* mod_start = p;
   const char* mod_end = p;
   if (*p == ',') {
     p++;
     mod_start = p;
-    while (is_modifier_char(*p))
+    while (is_consumed_modifier_char(*p, *kind))
       p++;
     mod_end = p;
   } else if (is_short) {
     const char* scan = p;
-    while (is_modifier_char(*scan))
+    while (is_consumed_modifier_char(*scan, *kind))
       scan++;
     if (*scan == '\0' || *scan == ' ' || *scan == '_') {
       mod_start = p;
@@ -253,6 +399,21 @@ static bool parse_rule_syntax(const char* text, RuleKind* kind, unsigned* sides,
     case 'C':
       *cvs_inject = true;
       break;
+    case '-':
+      *no_prefixes = true;
+      break;
+    case '+':
+      *include_defaults = true;
+      break;
+    case 'e':
+      *exclude_self = true;
+      break;
+    case 'n':
+      *no_inherit = true;
+      break;
+    case 'w':
+      *word_split = true;
+      break;
     default:
       break;
     }
@@ -288,11 +449,17 @@ FilterRule* filter_rule_parse(const char* line, const FilterParseOptions* opts,
   RuleKind kind = RULE_KIND_UNKNOWN;
   unsigned sides;
   bool sides_explicit, negate, anchored_mod, perishable, xattr, cvs_inject;
+  bool no_prefixes, include_defaults, word_split, no_inherit, exclude_self;
   const char* pat;
   size_t pat_len;
+  char bad_mod;
   if (!parse_rule_syntax(p, &kind, &sides, &sides_explicit, &negate, &anchored_mod, &perishable,
-                         &xattr, &cvs_inject, &pat, &pat_len)) {
-    filter_set_error(err, err_size, "unrecognized filter rule syntax");
+                         &xattr, &cvs_inject, &no_prefixes, &include_defaults, &word_split,
+                         &no_inherit, &exclude_self, &pat, &pat_len, &bad_mod)) {
+    if (bad_mod != '\0')
+      filter_set_error(err, err_size, "unsupported filter modifier '%c'", bad_mod);
+    else
+      filter_set_error(err, err_size, "unrecognized filter rule syntax");
     return NULL;
   }
   if (cvs_inject) {
@@ -401,7 +568,6 @@ FilterRule* filter_rule_parse(const char* line, const FilterParseOptions* opts,
   rule->dir_only = dir_only;
   rule->negate = negate;
   rule->perishable = perishable;
-  (void)xattr; /* xattr-name rules never match file/dir names; accepted/ignored */
   return rule;
 }
 
@@ -442,7 +608,7 @@ static bool filter_list_append_cvs(FilterRuleList* list, unsigned sides) {
     }
     memcpy(rule->pattern, CVS_DEFAULTS[i].pattern, plen);
     rule->pattern[plen] = '\0';
-    if (!set_rule_owner(rule, "")) {
+    if (!filter_rule_set_owner(rule, "")) {
       filter_rule_free(rule);
       return false;
     }
@@ -460,16 +626,138 @@ static bool filter_list_parse_append_depth(FilterRuleList* list, const char* lin
                                            const FilterParseOptions* opts, const char* base_dir,
                                            int depth, char* err, size_t err_size);
 
-/* Read a merge file and splice its rules into `list`.  A relative path is
- * resolved below `base_dir` when given, else used as-is (rsync resolves a
- * command-line merge file relative to the current directory). */
+/* Append one merge-file token/line to `list`, honoring the merge rule's
+ * no-prefix/include mode.  In no-prefix mode the token is a bare pattern whose
+ * include/exclude default comes from the merge rule (rsync's "-"/"+" merge
+ * modifiers); otherwise the token is parsed as a full filter rule. */
+static bool filter_merge_append_token(FilterRuleList* list, const char* token,
+                                      const FilterDirMerge* spec, const FilterParseOptions* opts,
+                                      const char* base_dir, int depth, char* err, size_t err_size) {
+  if (spec->no_prefixes || spec->include) {
+    size_t tlen = strlen(token);
+    char* text = malloc(tlen + 3);
+    if (!text) {
+      filter_set_error(err, err_size, "memory allocation failed");
+      return false;
+    }
+    text[0] = spec->include ? '+' : '-';
+    text[1] = ' ';
+    memcpy(text + 2, token, tlen + 1);
+    bool ok = filter_list_parse_append_depth(list, text, opts, base_dir, depth + 1, err, err_size);
+    free(text);
+    return ok;
+  }
+  return filter_list_parse_append_depth(list, token, opts, base_dir, depth + 1, err, err_size);
+}
+
+/* Read a merge file's tokens/lines into `list` for `spec`.  A `w` merge rule
+ * word-splits on whitespace (turning comments off); otherwise lines are parsed
+ * and whole-line `#` comments skipped.  When `owner_rel` is non-NULL the newly
+ * added rules are owned by that directory; a no-inherit spec marks them so they
+ * apply only there.  Returns false on parse/allocation failure. */
+static bool filter_merge_read(FilterRuleList* list, FILE* fp, const char* display_path,
+                              const FilterDirMerge* spec, const FilterParseOptions* opts,
+                              const char* base_dir, const char* owner_rel, int depth, char* err,
+                              size_t err_size) {
+  /* Lowest list index this read is responsible for.  A "clear"/"!" inside the
+   * file resets list->count to 0 (freeing the caller's earlier rules too), so
+   * the base must follow it down: otherwise post-clear rules sit below the
+   * original count and never receive an owner (nor no-inherit) and are missed
+   * by the rollback. */
+  int floor = list->count;
+  char* line = NULL;
+  size_t cap = 0;
+  bool ok = true;
+  while (ok) {
+    ssize_t n = utils_getdelim_bounded(fp, &line, &cap, '\n', UTILS_MAX_LINE_LEN);
+    if (n < 0) {
+      if (errno == EFBIG)
+        filter_set_error(err, err_size, "line in %s exceeds %d bytes", display_path,
+                         (int)UTILS_MAX_LINE_LEN);
+      else
+        filter_set_error(err, err_size, "error reading %s: %s", display_path, strerror(errno));
+      ok = false;
+      break;
+    }
+    if (n == 0)
+      break;
+    if (spec->word_split) {
+      /* Whitespace-separated tokens; newlines are ordinary separators and
+       * comments are disabled. */
+      const char* s = line;
+      while (*s) {
+        while (*s == ' ' || *s == '\t' || *s == '\n' || *s == '\r')
+          s++;
+        if (*s == '\0')
+          break;
+        const char* start = s;
+        while (*s != '\0' && *s != ' ' && *s != '\t' && *s != '\n' && *s != '\r')
+          s++;
+        size_t tlen = (size_t)(s - start);
+        char* token = malloc(tlen + 1);
+        if (!token) {
+          filter_set_error(err, err_size, "memory allocation failed");
+          ok = false;
+          break;
+        }
+        memcpy(token, start, tlen);
+        token[tlen] = '\0';
+        if (!filter_merge_append_token(list, token, spec, opts, base_dir, depth, err, err_size))
+          ok = false;
+        if (list->count < floor)
+          floor = list->count; /* a "clear" reset the list below this read's base */
+        free(token);
+      }
+    } else {
+      const char* lp = line;
+      while (*lp == ' ' || *lp == '\t')
+        lp++;
+      if (*lp == '\0' || *lp == '\n' || *lp == '\r' || *lp == '#')
+        continue;
+      if (!filter_merge_append_token(list, lp, spec, opts, base_dir, depth, err, err_size))
+        ok = false;
+      if (list->count < floor)
+        floor = list->count; /* a "clear" reset the list below this read's base */
+    }
+  }
+  free(line);
+  if (!ok) {
+    /* Drop every live rule this read is responsible for.  After a "clear" that
+     * base is 0, so the post-clear rules are freed too instead of leaking. */
+    for (int i = floor; i < list->count; i++)
+      filter_rule_free(list->items[i]);
+    list->count = floor;
+    return false;
+  }
+  for (int i = floor; i < list->count; i++) {
+    FilterRule* rule = list->items[i];
+    if (spec->no_inherit)
+      rule->no_inherit = true;
+    if (owner_rel && !filter_rule_set_owner(rule, owner_rel)) {
+      filter_set_error(err, err_size, "memory allocation failed");
+      for (int j = floor; j < list->count; j++)
+        filter_rule_free(list->items[j]);
+      list->count = floor;
+      return false;
+    }
+  }
+  return true;
+}
+
+/* Read a single-instance merge file and splice its rules into `list`.  A
+ * relative path is resolved below `base_dir` when given, else used as-is (rsync
+ * resolves a command-line merge file relative to the current directory). */
 static bool filter_list_merge_file(FilterRuleList* list, const char* name,
-                                   const FilterParseOptions* opts, const char* base_dir, int depth,
-                                   char* err, size_t err_size) {
+                                   const FilterDirMerge* spec, const FilterParseOptions* opts,
+                                   const char* base_dir, int depth, char* err, size_t err_size) {
   if (name[0] == '\0') {
     filter_set_error(err, err_size, "merge requires a filename");
     return false;
   }
+  if (spec->exclude_self && !filter_list_add_exclude_self(list, name)) {
+    filter_set_error(err, err_size, "memory allocation failed");
+    return false;
+  }
   char* path =
       (base_dir && base_dir[0] && name[0] != '/') ? path_cat(base_dir, name) : str_dup(name);
   if (!path) {
@@ -482,29 +770,7 @@ static bool filter_list_merge_file(FilterRuleList* list, const char* name,
     free(path);
     return false;
   }
-  char* line = NULL;
-  size_t cap = 0;
-  bool ok = true;
-  while (true) {
-    ssize_t n = utils_getdelim_bounded(fp, &line, &cap, '\n', UTILS_MAX_LINE_LEN);
-    if (n < 0) {
-      filter_set_error(err, err_size, "error reading merge file '%s'", path);
-      ok = false;
-      break;
-    }
-    if (n == 0)
-      break;
-    const char* lp = line;
-    while (*lp == ' ' || *lp == '\t')
-      lp++;
-    if (*lp == '\0' || *lp == '\n' || *lp == '\r' || *lp == '#')
-      continue;
-    if (!filter_list_parse_append_depth(list, lp, opts, base_dir, depth + 1, err, err_size)) {
-      ok = false;
-      break;
-    }
-  }
-  free(line);
+  bool ok = filter_merge_read(list, fp, path, spec, opts, base_dir, NULL, depth, err, err_size);
   fclose(fp);
   free(path);
   return ok;
@@ -528,18 +794,31 @@ static bool filter_list_parse_append_depth(FilterRuleList* list, const char* lin
   RuleKind kind = RULE_KIND_UNKNOWN;
   unsigned sides;
   bool sides_explicit, negate, anchored_mod, perishable, xattr, cvs_inject;
+  bool no_prefixes, include_defaults, word_split, no_inherit, exclude_self;
   const char* pat;
   size_t pat_len;
+  char bad_mod;
   if (!parse_rule_syntax(p, &kind, &sides, &sides_explicit, &negate, &anchored_mod, &perishable,
-                         &xattr, &cvs_inject, &pat, &pat_len)) {
-    filter_set_error(err, err_size, "unrecognized filter rule syntax: %s", p);
+                         &xattr, &cvs_inject, &no_prefixes, &include_defaults, &word_split,
+                         &no_inherit, &exclude_self, &pat, &pat_len, &bad_mod)) {
+    if (bad_mod != '\0')
+      filter_set_error(err, err_size, "unsupported filter modifier '%c': %s", bad_mod, p);
+    else
+      filter_set_error(err, err_size, "unrecognized filter rule syntax: %s", p);
     return false;
   }
   (void)sides_explicit;
   (void)negate;
   (void)anchored_mod;
   (void)perishable;
-  (void)xattr;
+
+  /* xattr-name rules are not implemented; reject them everywhere (including on
+   * merge/dir-merge, where the flag would otherwise be silently dropped) with
+   * the same diagnostic the standalone parser gives. */
+  if (xattr) {
+    filter_set_error(err, err_size, "xattr-name filter rules (the x modifier) are not supported");
+    return false;
+  }
 
   if (cvs_inject) {
     /* "C" injects the CVS defaults in place; no pattern is expected. */
@@ -567,7 +846,15 @@ static bool filter_list_parse_append_depth(FilterRuleList* list, const char* lin
     }
     memcpy(name, pat, pat_len);
     name[pat_len] = '\0';
-    bool ok = filter_list_merge_file(list, name, opts, base_dir, depth, err, err_size);
+    /* A single-instance merge has no inheritance, so 'n' is meaningless; the
+     * other merge modifiers still shape how the file is read. */
+    FilterDirMerge spec = {.name = name,
+                           .no_prefixes = no_prefixes,
+                           .include = include_defaults,
+                           .word_split = word_split,
+                           .no_inherit = false,
+                           .exclude_self = exclude_self};
+    bool ok = filter_list_merge_file(list, name, &spec, opts, base_dir, depth, err, err_size);
     free(name);
     return ok;
   }
@@ -583,7 +870,8 @@ static bool filter_list_parse_append_depth(FilterRuleList* list, const char* lin
     }
     memcpy(name, pat, pat_len);
     name[pat_len] = '\0';
-    bool ok = filter_rule_list_add_dir_merge(list, name);
+    bool ok = filter_rule_list_add_dir_merge_ex(list, name, no_prefixes, include_defaults,
+                                                word_split, no_inherit, exclude_self);
     free(name);
     if (!ok) {
       filter_set_error(err, err_size, "memory allocation failed");
@@ -644,27 +932,30 @@ FilterRuleList* filter_base_build(const char* const* rule_texts, int rule_count,
 /* Undo the rules and dir-merge registrations that one merge file appended,
  * leaving the caller's earlier content intact.  A "clear" rule inside the file
  * frees every rule, including the caller's; clamp to the surviving count so
- * those already-freed rules are never resurrected and freed a second time. */
+ * those already-freed rules are never resurrected and freed a second time.
+ * (filter_merge_read() has already rolled its own range back by the time this
+ * runs, so on a post-clear failure `list->count` is below `rules_before` and
+ * this is a no-op for the rules.) */
 static void filter_file_rollback(FilterRuleList* list, int rules_before, int dir_merges_before) {
   int first = rules_before < list->count ? rules_before : list->count;
   for (int i = first; i < list->count; i++)
     filter_rule_free(list->items[i]);
   list->count = first;
   for (int i = dir_merges_before; i < list->dir_merge_count; i++)
-    free(list->dir_merge_names[i]);
+    free(list->dir_merges[i].name);
   list->dir_merge_count = dir_merges_before;
 }
 
-bool filter_file_append(FilterRuleList* list, const char* dir_path, const char* name,
-                        const char* owner_rel, const FilterParseOptions* opts, bool* exists,
-                        char* err, size_t err_size) {
+bool filter_dir_merge_append(FilterRuleList* list, const char* dir_path, const FilterDirMerge* spec,
+                             const char* owner_rel, const FilterParseOptions* opts, bool* exists,
+                             char* err, size_t err_size) {
   if (err && err_size > 0)
     err[0] = '\0';
   if (exists)
     *exists = false;
-  if (!list)
+  if (!list || !spec || !spec->name)
     return false;
-  char* filter_path = path_cat(dir_path, name);
+  char* filter_path = path_cat(dir_path, spec->name);
   if (!filter_path) {
     filter_set_error(err, err_size, "memory allocation failed");
     return false;
@@ -675,7 +966,7 @@ bool filter_file_append(FilterRuleList* list, const char* dir_path, const char*
     if (errno == ENOENT || errno == ENOTDIR)
       return true;
     char* escaped_dir = output_escape(dir_path, log_get_8_bit_output());
-    log_message(LOG_LEVEL_WARNING, "Could not read %s in %s: %s", name,
+    log_message(LOG_LEVEL_WARNING, "Could not read %s in %s: %s", spec->name,
                 escaped_dir ? escaped_dir : "<allocation failed>", strerror(errno));
     free(escaped_dir);
     return true;
@@ -684,51 +975,25 @@ bool filter_file_append(FilterRuleList* list, const char* dir_path, const char*
     *exists = true;
   int rules_before = list->count;
   int dir_merges_before = list->dir_merge_count;
-  char* line = NULL;
-  size_t line_cap = 0;
-  bool ok = true;
-  while (true) {
-    ssize_t n = utils_getdelim_bounded(fp, &line, &line_cap, '\n', UTILS_MAX_LINE_LEN);
-    if (n < 0) {
-      if (errno == EFBIG) {
-        filter_set_error(err, err_size, "line in %s exceeds %d bytes", name,
-                         (int)UTILS_MAX_LINE_LEN);
-      } else {
-        filter_set_error(err, err_size, "error reading %s: %s", name, strerror(errno));
-      }
-      ok = false;
-      break;
-    }
-    if (n == 0)
-      break;
-    const char* p = line;
-    while (*p == ' ' || *p == '\t')
-      p++;
-    if (*p == '\0' || *p == '\n' || *p == '\r' || *p == '#')
-      continue;
-    /* Merge files inside a per-directory file resolve relative to that
-       directory. */
-    if (!filter_list_parse_append_depth(list, p, opts, dir_path, 0, err, err_size)) {
-      ok = false;
-      break;
-    }
-  }
-  free(line);
+  /* Merge files inside a per-directory file resolve relative to that
+     directory. */
+  bool ok =
+      filter_merge_read(list, fp, spec->name, spec, opts, dir_path, owner_rel, 0, err, err_size);
   fclose(fp);
   if (!ok) {
     filter_file_rollback(list, rules_before, dir_merges_before);
     return false;
   }
-  for (int i = rules_before; i < list->count; i++) {
-    if (!set_rule_owner(list->items[i], owner_rel)) {
-      filter_set_error(err, err_size, "memory allocation failed");
-      filter_file_rollback(list, rules_before, dir_merges_before);
-      return false;
-    }
-  }
   return true;
 }
 
+bool filter_file_append(FilterRuleList* list, const char* dir_path, const char* name,
+                        const char* owner_rel, const FilterParseOptions* opts, bool* exists,
+                        char* err, size_t err_size) {
+  FilterDirMerge spec = {.name = (char*)name};
+  return filter_dir_merge_append(list, dir_path, &spec, owner_rel, opts, exists, err, err_size);
+}
+
 FilterRuleList* filter_file_read_named(const char* dir_path, const char* name,
                                        const char* owner_rel, const FilterParseOptions* opts,
                                        bool* exists, char* err, size_t err_size) {
@@ -770,11 +1035,16 @@ static FilterAction rule_matches(const FilterRule* rule, const char* rel_path, c
     return FILTER_ACTION_NONE;
   if (!(rule->sides & side))
     return FILTER_ACTION_NONE;
-  /* A rule applies only to entries below its owner directory. */
+  /* A rule applies only to entries below its owner directory.  The receive
+   * root's destination-relative coordinate may be written as "." (the
+   * synced-directory sentinel), which is the same scope as the empty owner. */
+  const char* owner = rule->owner;
+  if (owner && strcmp(owner, ".") == 0)
+    owner = "";
   const char* rel2 = rel_path;
-  if (rule->owner && rule->owner[0] != '\0') {
-    size_t owner_len = strlen(rule->owner);
-    if (strncmp(rule->owner, rel_path, owner_len) != 0)
+  if (owner && owner[0] != '\0') {
+    size_t owner_len = strlen(owner);
+    if (strncmp(owner, rel_path, owner_len) != 0)
       return FILTER_ACTION_NONE;
     if (rel_path[owner_len] != '/')
       return FILTER_ACTION_NONE;
@@ -782,6 +1052,10 @@ static FilterAction rule_matches(const FilterRule* rule, const char* rel_path, c
   }
   if (rel2[0] == '\0')
     return FILTER_ACTION_NONE;
+  /* A no-inherit rule ('n' on its dir-merge) applies only to direct children of
+   * its owner directory, never to deeper entries. */
+  if (rule->no_inherit && strchr(rel2, '/') != NULL)
+    return FILTER_ACTION_NONE;
   bool matched;
   if (rule->dir_only && !is_dir)
     matched = false;
@@ -812,7 +1086,44 @@ FilterAction filter_rules_apply_side(const FilterRuleList* list, const char* rel
   return FILTER_ACTION_NONE;
 }
 
-FilterAction filter_rules_apply(const FilterRuleList* list, const char* rel_path, const char* leaf,
-                                bool is_dir) {
-  return filter_rules_apply_side(list, rel_path, leaf, is_dir, FILTER_SIDE_SENDER);
+FilterAction filter_dir_rules_apply_side(const FilterRuleList* dir_rules, const char* rel_path,
+                                         const char* leaf, bool is_dir) {
+  if (!dir_rules || !rel_path)
+    return FILTER_ACTION_NONE;
+  size_t len = strlen(rel_path);
+  if (len == 0)
+    return FILTER_ACTION_NONE;
+  /* The containing directory of rel_path is the prefix before its final '/'. */
+  size_t owner_len = 0;
+  for (size_t i = 0; i < len; i++) {
+    if (rel_path[i] == '/')
+      owner_len = i;
+  }
+  for (;;) {
+    for (int i = 0; i < dir_rules->count; i++) {
+      const FilterRule* rule = dir_rules->items[i];
+      const char* rule_owner = rule && rule->owner ? rule->owner : "";
+      /* "." is the receive root's coordinate (see rule_matches). */
+      if (strcmp(rule_owner, ".") == 0)
+        rule_owner = "";
+      size_t rule_owner_len = strlen(rule_owner);
+      if (rule_owner_len != owner_len)
+        continue;
+      if (owner_len != 0 && memcmp(rule_owner, rel_path, owner_len) != 0)
+        continue;
+      FilterAction action = rule_matches(rule, rel_path, leaf, is_dir, FILTER_SIDE_RECEIVER);
+      if (action != FILTER_ACTION_NONE)
+        return action;
+    }
+    if (owner_len == 0)
+      break;
+    /* Move to the parent directory: the last '/' before owner_len. */
+    size_t parent = 0;
+    for (size_t j = 0; j < owner_len; j++) {
+      if (rel_path[j] == '/')
+        parent = j;
+    }
+    owner_len = parent;
+  }
+  return FILTER_ACTION_NONE;
 }

src/shared/filter.h

@@ -23,7 +23,14 @@
  *   dir-merge/: per-directory merge file (registered for the scanner)
  *   clear/!     clear the current rule list (takes no argument)
  * Modifiers: '/' absolute anchor, '!' negate match, 'C' inject CVS defaults,
- * 's' sender side, 'r' receiver side, 'p' perishable, 'x' xattr name rule.
+ * 's' sender side, 'r' receiver side, 'p' perishable.  The rsync 'x'
+ * (xattr-name) modifier is not implemented and is rejected explicitly
+ * everywhere.  The merge-only modifiers are accepted only on merge/dir-merge
+ * rules (rejected on every other rule, matching rsync): 'e' excludes the merge
+ * file itself, 'n' makes the merged rules non-inheriting (they apply only to
+ * the directory that holds the merge file), 'w' word-splits the merge file on
+ * whitespace instead of lines, and '-' reads the merge file as a list of bare
+ * exclude patterns with no rule prefixes.
  * A trailing '/' makes a pattern match directories only.  A leading '/' anchors
  * the pattern to its owner directory.
  */
@@ -49,18 +56,32 @@ typedef struct {
   bool dir_only;       /* pattern had a trailing '/': matches directories only */
   bool negate;         /* '!' modifier: match succeeds when the pattern does not */
   bool perishable;     /* 'p' modifier (ignored in deleted directories) */
+  bool no_inherit;     /* 'n' on the owning dir-merge: applies only in `owner` */
   char* owner;         /* owning directory rel path ("" == transfer root) */
   char* pattern;       /* cleaned glob pattern (no leading '/', no trailing '/') */
 } FilterRule;
 
+/* One per-directory merge-file registration ("dir-merge NAME"/": NAME", "merge
+ * NAME"/". NAME" and -F's .rsync-filter) together with the merge-only modifiers
+ * parsed from the rule.  The scanner reads `name` in every directory it
+ * traverses and applies `no_prefixes`/`include`/`word_split`/`no_inherit`/
+ * `exclude_self` while merging the file's rules. */
+typedef struct {
+  char* name;
+  bool no_prefixes;  /* '-' : file holds only bare exclude patterns */
+  bool include;      /* '+' : file holds only bare include patterns */
+  bool word_split;   /* 'w' : split the file on whitespace, not lines */
+  bool no_inherit;   /* 'n' : the merged rules do not inherit below their dir */
+  bool exclude_self; /* 'e' : exclude the merge file itself from the transfer */
+} FilterDirMerge;
+
 typedef struct FilterRuleList {
   FilterRule** items; /* owned array of rule pointers */
   int count;
   int capacity;
-  /* Per-directory merge-file basenames registered by "dir-merge NAME"/": NAME"
-   * or by -F (.rsync-filter).  Owned strings; the scanner reads each name in
-   * every directory it traverses. */
-  char** dir_merge_names;
+  /* Per-directory merge-file registrations.  Owned; the scanner reads each
+   * name in every directory it traverses. */
+  FilterDirMerge* dir_merges;
   int dir_merge_count;
   int dir_merge_capacity;
 } FilterRuleList;
@@ -77,13 +98,28 @@ typedef struct {
 FilterRule* filter_rule_parse(const char* line, const FilterParseOptions* opts, char* err,
                               size_t err_size);
 void filter_rule_free(FilterRule* rule);
+/* Deep-copy a rule (owned pattern/owner).  Returns NULL on allocation failure. */
+FilterRule* filter_rule_clone(const FilterRule* rule);
+/* Replace a rule's owner directory (owned copy of `owner`, "" for the transfer
+ * root).  Returns false on allocation failure, leaving the rule unchanged.
+ * Used to re-express a mirrored per-directory rule in the receiver's
+ * destination-relative coordinate system. */
+bool filter_rule_set_owner(FilterRule* rule, const char* owner);
 
 FilterRuleList* filter_rule_list_create(void);
 /* Append a fully-parsed rule (takes ownership). Returns false on OOM. */
 bool filter_rule_list_add(FilterRuleList* list, FilterRule* rule);
-/* Register a per-directory merge-file basename (idempotent). Returns false on
- * OOM.  Used by the scanner to read custom "dir-merge" files. */
+/* Register a per-directory merge-file basename (idempotent, no modifiers).
+ * Returns false on OOM.  Used by the scanner to read custom "dir-merge" files. */
 bool filter_rule_list_add_dir_merge(FilterRuleList* list, const char* name);
+/* Register a per-directory merge file with its merge-only modifiers.  On a
+ * duplicate name the existing registration is kept (rsync's first wins) and true
+ * is returned.  When `exclude_self` is set an implicit exclude rule for the
+ * merge file's basename is appended to the list at this position, matching
+ * rsync's `e` modifier.  Returns false on OOM. */
+bool filter_rule_list_add_dir_merge_ex(FilterRuleList* list, const char* name, bool no_prefixes,
+                                       bool include, bool word_split, bool no_inherit,
+                                       bool exclude_self);
 /* Parse `line` and append it.  Handles "clear"/"!" (resets the list), "merge
  * FILE"/". FILE" (splices the file's rules) and "dir-merge NAME"/": NAME"
  * (registers a per-directory filename).  Returns false and fills `err` on bad
@@ -116,6 +152,15 @@ bool filter_file_append(FilterRuleList* list, const char* dir_path, const char*
                         const char* owner_rel, const FilterParseOptions* opts, bool* exists,
                         char* err, size_t err_size);
 
+/* Append a per-directory merge file honoring its merge-only modifiers: `-`
+ * reads every (word-split, when `w`) token as a bare exclude, `+` as a bare
+ * include, and `n` marks each read rule non-inheriting.  A plain name behaves
+ * like filter_file_append.  A missing file yields *exists=false with no error;
+ * returns false only on a parse/allocation failure (message in `err`). */
+bool filter_dir_merge_append(FilterRuleList* list, const char* dir_path, const FilterDirMerge* spec,
+                             const char* owner_rel, const FilterParseOptions* opts, bool* exists,
+                             char* err, size_t err_size);
+
 /* filter_file_read_named with the default ".rsync-filter" name. */
 FilterRuleList* filter_file_read(const char* dir_path, const char* owner_rel, bool* exists,
                                  char* err, size_t err_size);
@@ -129,9 +174,15 @@ FilterRuleList* filter_file_read(const char* dir_path, const char* owner_rel, bo
 FilterAction filter_rules_apply_side(const FilterRuleList* list, const char* rel_path,
                                      const char* leaf, bool is_dir, unsigned side);
 
-/* Sender-side convenience wrapper (kept for callers/tests that only need the
- * transfer decision). */
-FilterAction filter_rules_apply(const FilterRuleList* list, const char* rel_path, const char* leaf,
-                                bool is_dir);
+/* Evaluate a received per-directory rule set for the receiver side, using
+ * rsync's per-directory-before-ancestors order: the entry's containing
+ * directory's rules are tried first, then each ancestor's, then the receive
+ * root's.  `dir_rules` is a flat list whose rules carry `owner`; a rule applies
+ * only when `owner` is exactly the directory being examined (a no-inherit rule
+ * therefore applies only to that directory's direct children).  Returns the
+ * first matching rule's receiver verdict (PROTECT/RISK) or FILTER_ACTION_NONE.
+ * The caller evaluates the command-line base rules after this chain. */
+FilterAction filter_dir_rules_apply_side(const FilterRuleList* dir_rules, const char* rel_path,
+                                         const char* leaf, bool is_dir);
 
 #endif

src/shared/format.c

@@ -62,14 +62,16 @@ bool format_dest_state_send(int fd, const OutputDestState* state) {
   if (!state)
     return false;
   int32_t has_old = state->existed ? 1 : 0;
+  int32_t target_matches = state->target_matches ? 1 : 0;
   uint64_t size = (uint64_t)state->size;
   int64_t mtime = (int64_t)state->mtime_sec;
   int64_t mtime_nsec = state->mtime_nsec;
   uint32_t mode = state->mode;
   int32_t uid = state->uid;
   int32_t gid = state->gid;
-  return send_n_data(fd, &has_old, sizeof(has_old)) && send_n_data(fd, &size, sizeof(size)) &&
-         send_n_data(fd, &mtime, sizeof(mtime)) &&
+  return send_n_data(fd, &has_old, sizeof(has_old)) &&
+         send_n_data(fd, &target_matches, sizeof(target_matches)) &&
+         send_n_data(fd, &size, sizeof(size)) && send_n_data(fd, &mtime, sizeof(mtime)) &&
          send_n_data(fd, &mtime_nsec, sizeof(mtime_nsec)) && send_n_data(fd, &mode, sizeof(mode)) &&
          send_n_data(fd, &uid, sizeof(uid)) && send_n_data(fd, &gid, sizeof(gid));
 }
@@ -78,14 +80,16 @@ bool format_dest_state_receive(int fd, OutputDestState* state) {
   if (!state)
     return false;
   int32_t has_old = 0;
+  int32_t target_matches = 0;
   uint64_t size = 0;
   int64_t mtime = 0;
   int64_t mtime_nsec = 0;
   uint32_t mode = 0;
   int32_t uid = 0;
   int32_t gid = 0;
-  if (!receive_n_data(fd, &has_old, sizeof(has_old)) || !receive_n_data(fd, &size, sizeof(size)) ||
-      !receive_n_data(fd, &mtime, sizeof(mtime)) ||
+  if (!receive_n_data(fd, &has_old, sizeof(has_old)) ||
+      !receive_n_data(fd, &target_matches, sizeof(target_matches)) ||
+      !receive_n_data(fd, &size, sizeof(size)) || !receive_n_data(fd, &mtime, sizeof(mtime)) ||
       !receive_n_data(fd, &mtime_nsec, sizeof(mtime_nsec)) ||
       !receive_n_data(fd, &mode, sizeof(mode)) || !receive_n_data(fd, &uid, sizeof(uid)) ||
       !receive_n_data(fd, &gid, sizeof(gid)))
@@ -93,6 +97,7 @@ bool format_dest_state_receive(int fd, OutputDestState* state) {
   memset(state, 0, sizeof(*state));
   state->known = true;
   state->existed = has_old != 0;
+  state->target_matches = target_matches != 0;
   state->size = size;
   state->mtime_sec = mtime;
   state->mtime_nsec = mtime_nsec;
@@ -105,9 +110,10 @@ bool format_dest_state_receive(int fd, OutputDestState* state) {
 bool format_stats_send(int fd, const ReceiverStats* stats) {
   if (!stats)
     return false;
-  unsigned long long fields[8] = {
+  unsigned long long fields[12] = {
       stats->matched_data, stats->deleted_files, stats->would_delete_count, stats->literal_bytes,
       stats->created_reg,  stats->created_dir,   stats->created_link,       stats->created_special,
+      stats->deleted_reg,  stats->deleted_dir,   stats->deleted_link,       stats->deleted_special,
   };
   return send_n_data(fd, fields, sizeof(fields));
 }
@@ -115,7 +121,7 @@ bool format_stats_send(int fd, const ReceiverStats* stats) {
 bool format_stats_receive(int fd, ReceiverStats* stats) {
   if (!stats)
     return false;
-  unsigned long long fields[8] = {0};
+  unsigned long long fields[12] = {0};
   if (!receive_n_data(fd, fields, sizeof(fields)))
     return false;
   memset(stats, 0, sizeof(*stats));
@@ -127,5 +133,9 @@ bool format_stats_receive(int fd, ReceiverStats* stats) {
   stats->created_dir = fields[5];
   stats->created_link = fields[6];
   stats->created_special = fields[7];
+  stats->deleted_reg = fields[8];
+  stats->deleted_dir = fields[9];
+  stats->deleted_link = fields[10];
+  stats->deleted_special = fields[11];
   return true;
 }

src/shared/format.h

@@ -17,10 +17,18 @@
 /* Pre-transfer destination snapshot, reported by the receiver when the wire
  * config carries report_dest_info.  `known` distinguishes "no report was
  * requested/received" from "the destination did not exist" (`existed == false`
- * with `known == true`). */
+ * with `known == true`).
+ *
+ * `target_matches` is meaningful only for a symlink destination (protocol
+ * 2.30.0): the receiver compares its on-disk link target with the incoming
+ * target and reports whether they are equal, so the sender can render rsync's
+ * `cLc........` (target changed) versus `.L..t......` (attributes only) and
+ * suppress an unchanged symlink's line entirely.  It is always false for every
+ * other entry kind. */
 typedef struct {
   bool known;
   bool existed;
+  bool target_matches;
   unsigned long long size;
   long long mtime_sec;
   long long mtime_nsec;
@@ -57,17 +65,24 @@ bool format_dest_state_send(int fd, const OutputDestState* state);
 bool format_dest_state_receive(int fd, OutputDestState* state);
 
 /* End-of-transfer receiver counters reported through STATUS_STATS (protocol
- * 2.25.0, extended in 2.28.0) when the wire config carries report_stats.
- * `would_delete_count` is the number of destination-relative paths the receiver
- * would have deleted in a -n/--dry-run --delete run; that many wire strings
- * immediately follow the fixed record (sent/read by the caller).
+ * 2.25.0, extended in 2.28.0 and 2.30.0) when the wire config carries
+ * report_stats.  `would_delete_count` is the number of destination-relative
+ * paths the receiver would have deleted in a -n/--dry-run --delete run; that
+ * many wire strings immediately follow the fixed record (sent/read by the
+ * caller).
  *
  * Protocol 2.28.0 adds the receiver-observed counters the sender cannot see:
  * `literal_bytes` is the file data the receiver actually stored literally
  * (whole files plus the literal fragments of a delta) and the four `created_*`
  * counters split the destination entries the receiver newly created by type,
  * reproducing rsync's `Number of created files` breakdown and an exact
- * `Literal data` for a delta run. */
+ * `Literal data` for a delta run.
+ *
+ * Protocol 2.30.0 appends the four `deleted_*` counters: the same reg/dir/link/
+ * special split for the entries the receiver ACTUALLY removed, so `--stats` can
+ * render rsync's `Number of deleted files: X (reg: A, dir: B, link: C,
+ * special: D)` parenthetical.  The scalar `deleted_files` stays the authoritative
+ * total (the breakdown is a strict partition of it). */
 typedef struct {
   unsigned long long matched_data;
   unsigned long long deleted_files;
@@ -77,6 +92,10 @@ typedef struct {
   unsigned long long created_dir;
   unsigned long long created_link;
   unsigned long long created_special;
+  unsigned long long deleted_reg;
+  unsigned long long deleted_dir;
+  unsigned long long deleted_link;
+  unsigned long long deleted_special;
 } ReceiverStats;
 
 /* Fixed-width STATUS_STATS counter record.  The status frame and the optional

src/shared/identity.c

@@ -3,6 +3,7 @@
 #include "utils.h"
 #include <errno.h>
 #include <fcntl.h>
+#include <fnmatch.h>
 #include <grp.h>
 #include <limits.h>
 #include <pwd.h>
@@ -12,6 +13,8 @@
 #include <sys/stat.h>
 #include <unistd.h>
 
+static bool identity_id_fits_int32(unsigned long id);
+
 /* The active identity snapshot lives in a per-process global.  The TCP server
  * forks one child process per connection, so a connection never shares this
  * with another; within a connection the multithreaded receiver reads it without
@@ -273,7 +276,7 @@ static bool identity_wire_map_valid(const IdentityMap* map) {
   }
   if (map->to < IDENTITY_CURRENT)
     return false;
-  if (map->to_name && strlen(map->to_name) > 255)
+  if (map->to_name && strlen(map->to_name) > IDENTITY_MAX_NAME_LEN)
     return false;
   return true;
 }
@@ -419,17 +422,10 @@ static int identity_parse_from(const char* token, bool is_group, int32_t* out_fr
     /* Not a numeric LOW-HIGH range: fall through and treat as a name (a
      * hyphenated account name like "wayne-smith" must still resolve). */
   }
-  /* A sender-side name.  A wildcard other than the bare '*' is matched by rsync
-   * against the sender's names; because FastSync transmits numeric ids only, the
-   * receiver cannot evaluate it, so reject rather than silently mis-match. */
-  if (identity_token_has_glob(token)) {
-    log_message(LOG_LEVEL_ERROR,
-                "%smap FROM '%s': name wildcards other than '*' are not supported "
-                "(FastSync transmits numeric ids, so sender names are unavailable on the "
-                "receiver)",
-                is_group ? "--group" : "--user", token);
-    return -1;
-  }
+  /* A sender-side name.  A FROM name wildcard other than the bare '*' is handled
+   * by identity_expand_from_glob() in the caller (it expands against the
+   * sender's account database at CLI-parse time), so this function only sees the
+   * bare '*' or a literal name here. */
   int32_t id;
   if (identity_resolve_token(token, is_group, &id) != 0)
     return -1;
@@ -486,6 +482,138 @@ static int identity_append_rule(IdentityMap** map, int* count, const IdentityMap
   return 0;
 }
 
+/* True when `lo` and `hi` are adjacent ids (no overflow at INT32_MAX). */
+static bool identity_ids_adjacent(int32_t lo, int32_t hi) {
+  return lo < INT32_MAX && hi == lo + 1;
+}
+
+static int identity_id_cmp(const void* a, const void* b) {
+  int32_t x = *(const int32_t*)a;
+  int32_t y = *(const int32_t*)b;
+  return (x > y) - (x < y);
+}
+
+static bool identity_ids_push(int32_t** ids, size_t* count, size_t* cap, int32_t id) {
+  if (*count == *cap) {
+    size_t grown_cap = *cap ? *cap * 2 : 16;
+    int32_t* grown = realloc(*ids, grown_cap * sizeof(int32_t));
+    if (!grown)
+      return false;
+    *ids = grown;
+    *cap = grown_cap;
+  }
+  (*ids)[(*count)++] = id;
+  return true;
+}
+
+/* Expand a FROM name wildcard (rsync's match against sender-side account names)
+ * into one rule per contiguous run of matching numeric ids, all sharing the same
+ * TO side.  FastSync transmits numeric ids only, so the wildcard must be
+ * resolved here -- at CLI-parse time -- against the SENDER's passwd/group
+ * database; the receiver has no sender names to match.  Contiguous matched ids
+ * are collapsed into a single LOW-HIGH range (a range of adjacent ids contains
+ * exactly the ids it spans, so this is semantically exact).  Returns 0 on
+ * success, -1 on an allocation failure, a wildcard that matches no sender
+ * account, or an expansion that would push the map past MAX_IDENTITY_MAP. */
+static int identity_expand_from_glob(Config* config, const char* glob, bool is_group,
+                                     const IdentityMap* to_rule) {
+  const char* optname = is_group ? "--groupmap" : "--usermap";
+  size_t cap = 0;
+  size_t n = 0;
+  int32_t* ids = NULL;
+  bool alloc_failed = false;
+
+  if (is_group) {
+    setgrent();
+    struct group* gr;
+    while ((gr = getgrent()) != NULL) {
+      if (fnmatch(glob, gr->gr_name, 0) != 0)
+        continue;
+      if (!identity_id_fits_int32((unsigned long)gr->gr_gid))
+        continue;
+      if (!identity_ids_push(&ids, &n, &cap, (int32_t)gr->gr_gid)) {
+        alloc_failed = true;
+        break;
+      }
+    }
+    endgrent();
+  } else {
+    setpwent();
+    struct passwd* pw;
+    while ((pw = getpwent()) != NULL) {
+      if (fnmatch(glob, pw->pw_name, 0) != 0)
+        continue;
+      if (!identity_id_fits_int32((unsigned long)pw->pw_uid))
+        continue;
+      if (!identity_ids_push(&ids, &n, &cap, (int32_t)pw->pw_uid)) {
+        alloc_failed = true;
+        break;
+      }
+    }
+    endpwent();
+  }
+
+  if (alloc_failed) {
+    free(ids);
+    log_message(LOG_LEVEL_ERROR, "%s: memory allocation failed expanding FROM '%s'", optname, glob);
+    return -1;
+  }
+  if (n == 0) {
+    free(ids);
+    log_message(LOG_LEVEL_ERROR, "%s FROM '%s': no source account name matches the wildcard",
+                optname, glob);
+    return -1;
+  }
+
+  qsort(ids, n, sizeof(int32_t), identity_id_cmp);
+  size_t unique = 0;
+  for (size_t i = 0; i < n; i++) {
+    if (unique == 0 || ids[unique - 1] != ids[i])
+      ids[unique++] = ids[i];
+  }
+  n = unique;
+
+  int runs = 0;
+  for (size_t i = 0; i < n; i++) {
+    if (i == 0 || !identity_ids_adjacent(ids[i - 1], ids[i]))
+      runs++;
+  }
+
+  IdentityMap** map = is_group ? &config->groupmap : &config->usermap;
+  int* count = is_group ? &config->groupmap_count : &config->usermap_count;
+  if (*count > MAX_IDENTITY_MAP - runs) {
+    log_message(LOG_LEVEL_ERROR,
+                "%s FROM '%s': the name wildcard expands to %d rule(s), which would exceed "
+                "the maximum of %d map rules",
+                optname, glob, runs, MAX_IDENTITY_MAP);
+    free(ids);
+    return -1;
+  }
+
+  for (size_t i = 0; i < n;) {
+    size_t j = i;
+    while (j + 1 < n && identity_ids_adjacent(ids[j], ids[j + 1]))
+      j++;
+    IdentityMap rule;
+    rule.from = ids[i];
+    rule.from_hi = ids[j];
+    rule.to = to_rule->to;
+    rule.to_name = to_rule->to_name ? str_dup(to_rule->to_name) : NULL;
+    if (to_rule->to_name && !rule.to_name) {
+      free(ids);
+      return -1;
+    }
+    if (identity_append_rule(map, count, &rule) != 0) {
+      free(rule.to_name);
+      free(ids);
+      return -1;
+    }
+    i = j + 1;
+  }
+  free(ids);
+  return 0;
+}
+
 int identity_parse_map(Config* config, const char* value, bool is_group) {
   if (!config || !value || *value == '\0') {
     log_message(LOG_LEVEL_ERROR, "%smap requires a value", is_group ? "--group" : "--user");
@@ -509,6 +637,30 @@ int identity_parse_map(Config* config, const char* value, bool is_group) {
     char* to_token = colon + 1;
     IdentityMap parsed;
     memset(&parsed, 0, sizeof(parsed));
+    /* A FROM name wildcard (anything with a glob metacharacter other than the
+     * bare '*') is expanded against the sender's account database here, while
+     * the sender's passwd/group DB is still available; the resulting numeric
+     * rules travel on the wire like an explicit list.  The TO side is parsed
+     * first so every expanded rule shares it. */
+    if (strcmp(from_token, "*") != 0 && identity_token_has_glob(from_token)) {
+      if (identity_parse_to(to_token, is_group, &parsed.to, &parsed.to_name) != 0) {
+        log_message(LOG_LEVEL_ERROR, "%s could not parse TO '%s' in '%s'", optname, to_token,
+                    value);
+        free(list);
+        return -1;
+      }
+      if (identity_expand_from_glob(config, from_token, is_group, &parsed) != 0) {
+        free(parsed.to_name);
+        free(list);
+        return -1;
+      }
+      /* Every rule emitted by the expansion took its own str_dup of the name,
+       * so the parse-time copy is unreachable on success: release it here (the
+       * failure path above already does).  `parsed.to_name` is NULL for a
+       * numeric TO. */
+      free(parsed.to_name);
+      continue;
+    }
     if (identity_parse_from(from_token, is_group, &parsed.from, &parsed.from_hi) != 0) {
       log_message(LOG_LEVEL_ERROR,
                   "%s could not resolve FROM '%s' in '%s' (a name must exist on the "

src/shared/identity.h

@@ -6,6 +6,11 @@
 #include <stdint.h>
 #include <sys/types.h>
 
+/* Maximum length of a receiver-resolved identity name in a FROM:TO map's TO
+ * field.  Bounded so a malicious/huge name can never cross the wire (see
+ * identity_wire_map_valid). */
+#define IDENTITY_MAX_NAME_LEN 255
+
 /*
  * Identity mapping: --numeric-ids / --usermap / --groupmap / --chown / --copy-as.
  *
@@ -25,8 +30,14 @@
 
 /* Parse one --usermap= / --groupmap= value (comma-separated FROM:TO rules,
  * first match wins) into config->usermap / config->groupmap.  is_group selects
- * the group tables and name databases.  Returns 0 on success, -1 on a
- * malformed spec or an unresolvable name (never a silent no-op). */
+ * the group tables and name databases.  A FROM name wildcard (containing `*`,
+ * `?` or `[...]`, but not the bare `*`) is expanded against the SENDER's
+ * account database at parse time into one or more numeric id/range rules
+ * (contiguous ids collapse to a range) sharing the same TO, because only
+ * numeric ids cross the wire; the expansion is capped at MAX_IDENTITY_MAP and a
+ * wildcard matching no account is an error.  Returns 0 on success, -1 on a
+ * malformed spec, an unresolvable name, an unmatched wildcard, or a map that
+ * would exceed MAX_IDENTITY_MAP (never a silent no-op). */
 int identity_parse_map(Config* config, const char* value, bool is_group);
 
 /* Parse --chown=USER:GROUP.  Supports USER:GROUP, USER (owner only), :GROUP

src/shared/incremental_check.h

@@ -0,0 +1,41 @@
+#ifndef INCREMENTAL_CHECK_H
+#define INCREMENTAL_CHECK_H
+
+#include "config.h"
+#include "file_types.h"
+#include "protocol.h"
+#include <stdbool.h>
+
+/* Incremental-check module: the per-file STATUS_CHECK state machine, the
+ * incremental delta / alternate-basis / fuzzy matching helpers and the shared
+ * xattr receive helper.  These declarations are re-exported by the
+ * file_receive.h facade. */
+
+/* Whole-file payload bound shared by the plain receive path and the
+ * incremental check paths. */
+#define MAX_FILE_DATA_SIZE MAX_RECEIVE_WHOLE_FILE_SIZE
+
+/* Receive a file's xattr block (when the config enables xattr transport) and
+ * attach it to `file`.  Returns false on a malformed/oversized frame. */
+bool receive_file_xattrs(File* file, int fd, const Config* config);
+
+File* receive_incremental_check(int fd, const Config* config, bool* skipped);
+/* Extended variant used by the receiver.  `would_transfer` (may be NULL) is set
+ * true only on the server-contacting --dry-run path when the file is not up to
+ * date: the receiver has already sent STATUS_DRY_RUN_TRANSFER and returns NULL
+ * without storing anything.  On that path `*skipped` is true for an up-to-date
+ * (STATUS_OK) file and both flags are false for a genuine error. */
+File* receive_incremental_check_ex(int fd, const Config* config, bool* skipped,
+                                   bool* would_transfer);
+
+/* Testable basis quick-check / verification policy.  file_basis_quick_match is
+ * rsync's metadata quick-check for a basis candidate (equal size is required
+ * separately by the caller; this adds the --size-only / mtime / --modify-window
+ * leg).  file_basis_content_required reports whether a hit must ALSO be
+ * confirmed by a whole-file content digest (--verify-basis; false is the
+ * default rsync-parity behavior). */
+bool file_basis_quick_match(const Config* config, const struct stat* st, time_t check_mtime,
+                            long check_mtime_nsec);
+bool file_basis_content_required(const Config* config);
+
+#endif

src/shared/log.c

@@ -1,4 +1,5 @@
 #include "log.h"
+#include "utils.h"
 #include <errno.h>
 #include <stdbool.h>
 #include <stdarg.h>
@@ -16,6 +17,7 @@ static bool info_flags_explicit = false;
 static FILE* log_fp = NULL;
 static _Thread_local bool eight_bit_output;
 static LogStderrMode stderr_mode = LOG_STDERR_ERRORS;
+static LogClientMsgSink client_msg_sink = NULL;
 
 /* Serializes access to log_fp and makes each emitted line atomic: the
  * timestamp prefix, formatted body, and trailing newline are written as one
@@ -77,6 +79,51 @@ LogStderrMode log_get_stderr_mode(void) {
   return stderr_mode;
 }
 
+void log_set_client_msg_sink(LogClientMsgSink sink) {
+  client_msg_sink = sink;
+}
+
+LogClientMsgSink log_get_client_msg_sink(void) {
+  return client_msg_sink;
+}
+
+/* Format just the message body (no prefix/newline) into a freshly allocated
+ * buffer.  Shared by log_message (which may hand the body to a client-message
+ * sink) and log_client_message.  Returns NULL on allocation/format failure. */
+static char* format_log_body(const char* format, va_list args) {
+  va_list copy;
+  va_copy(copy, args);
+  int body_len = vsnprintf(NULL, 0, format, copy);
+  va_end(copy);
+  if (body_len < 0)
+    return NULL;
+  char* body = malloc((size_t)body_len + 1);
+  if (!body)
+    return NULL;
+  vsnprintf(body, (size_t)body_len + 1, format, args);
+  return body;
+}
+
+/* Assemble a complete log line (prefix + body + newline) from an already
+ * formatted body.  Returns NULL on allocation failure. */
+static char* format_log_line_from_body(LogLevel log_level, const struct tm* t, const char* body) {
+  char prefix[64];
+  int prefix_len = snprintf(
+      prefix, sizeof(prefix), "%04d-%02d-%02d %02d:%02d:%02d [%s]: ", t->tm_year + 1900,
+      t->tm_mon + 1, t->tm_mday, t->tm_hour, t->tm_min, t->tm_sec, log_level_strings[log_level]);
+  if (prefix_len < 0 || prefix_len >= (int)sizeof(prefix))
+    return NULL;
+  size_t body_len = strlen(body);
+  char* line = malloc((size_t)prefix_len + body_len + 2); /* body + '\n' + NUL */
+  if (!line)
+    return NULL;
+  memcpy(line, prefix, (size_t)prefix_len);
+  memcpy(line + prefix_len, body, body_len);
+  line[(size_t)prefix_len + body_len] = '\n';
+  line[(size_t)prefix_len + body_len + 1] = '\0';
+  return line;
+}
+
 /* Format one complete log line (timestamp prefix + body + newline) into a
  * freshly allocated buffer.  This is pure CPU/malloc work and must happen
  * OUTSIDE the log mutex: the mutex only guards the log_fp pointer, so a
@@ -84,26 +131,11 @@ LogStderrMode log_get_stderr_mode(void) {
  * on allocation/formatting failure. */
 static char* format_log_line(LogLevel log_level, const struct tm* t, const char* format,
                              va_list args) {
-  char prefix[64];
-  int prefix_len = snprintf(
-      prefix, sizeof(prefix), "%04d-%02d-%02d %02d:%02d:%02d [%s]: ", t->tm_year + 1900,
-      t->tm_mon + 1, t->tm_mday, t->tm_hour, t->tm_min, t->tm_sec, log_level_strings[log_level]);
-  if (prefix_len < 0 || prefix_len >= (int)sizeof(prefix))
+  char* body = format_log_body(format, args);
+  if (!body)
     return NULL;
-  va_list copy;
-  va_copy(copy, args);
-  int body_len = vsnprintf(NULL, 0, format, copy);
-  va_end(copy);
-  if (body_len < 0)
-    return NULL;
-  size_t total = (size_t)prefix_len + (size_t)body_len;
-  char* line = malloc(total + 2); /* body bytes + '\n' + NUL */
-  if (!line)
-    return NULL;
-  memcpy(line, prefix, (size_t)prefix_len);
-  vsnprintf(line + prefix_len, (size_t)body_len + 1, format, args);
-  line[total] = '\n';
-  line[total + 1] = '\0';
+  char* line = format_log_line_from_body(log_level, t, body);
+  free(body);
   return line;
 }
 
@@ -121,6 +153,26 @@ static void emit_log_line(FILE* console, const char* line) {
   mtx_unlock(&log_mutex);
 }
 
+void log_client_message(const char* message) {
+  if (!message)
+    return;
+  /* The body is peer-controlled: escape every non-printable byte (newlines,
+     CR, ANSI ESC, ...) so a hostile client cannot forge log lines or inject
+     terminal control sequences.  output_escape() is the codebase's canonical
+     escaper and leaves printable text untouched. */
+  char* escaped = output_escape(message, log_get_8_bit_output());
+  if (!escaped)
+    return;
+  /* Route through the ordinary log level / destination gate (log_message):
+     this respects --log-file, the configured stderr mode and the level
+     threshold instead of always writing to stderr.  The wire body carries no
+     severity, so the forwarded diagnostic is emitted as a warning -- the
+     lowest level the default gate admits, which keeps the peer's messages
+     visible without bypassing --quiet. */
+  log_message(LOG_LEVEL_WARNING, "%s", escaped);
+  free(escaped);
+}
+
 void log_message(LogLevel log_level, const char* format, ...) {
   if (log_level < current_log_level)
     return;
@@ -138,8 +190,23 @@ void log_message(LogLevel log_level, const char* format, ...) {
 
   va_list args;
   va_start(args, format);
-  char* line = format_log_line(log_level, &t, format, args);
+  char* body = format_log_body(format, args);
   va_end(args);
+  if (!body)
+    return;
+  /* LOG_STDERR_CLIENT: hand the diagnostic to the client-message channel.  A
+     sink that takes ownership suppresses the local write; otherwise (no sink
+     yet, or the peer connection is not up) fall through to local output so the
+     diagnostic is never lost. */
+  if (stderr_mode == LOG_STDERR_CLIENT) {
+    LogClientMsgSink sink = client_msg_sink;
+    if (sink && sink(body)) {
+      free(body);
+      return;
+    }
+  }
+  char* line = format_log_line_from_body(log_level, &t, body);
+  free(body);
   if (!line)
     return;
   emit_log_line(dest_io, line);

src/shared/log.h

@@ -5,15 +5,40 @@
 #include <stdbool.h>
 #include <stdint.h>
 
+/* Ask the compiler to type-check the printf-style arguments of the variadic
+ * logging helpers.  Only enabled for GNU-compatible compilers (gcc/clang). */
+#if defined(__GNUC__)
+#define LOG_PRINTF_ATTR(fmt_idx, first_vararg_idx)                                                 \
+  __attribute__((format(printf, fmt_idx, first_vararg_idx)))
+#else
+#define LOG_PRINTF_ATTR(fmt_idx, first_vararg_idx)
+#endif
+
 typedef enum { LOG_LEVEL_DEBUG, LOG_LEVEL_INFO, LOG_LEVEL_WARNING, LOG_LEVEL_ERROR } LogLevel;
-typedef enum { LOG_STDERR_ERRORS, LOG_STDERR_ALL } LogStderrMode;
+/* --stderr=MODE destinations.  ERRORS keeps errors on stderr and everything
+ * else on stdout; ALL sends every message to stderr; CLIENT routes the client's
+ * own diagnostics over the protocol stream to the peer's stderr (rsync's
+ * --stderr=client / --no-msgs2stderr). */
+typedef enum { LOG_STDERR_ERRORS, LOG_STDERR_ALL, LOG_STDERR_CLIENT } LogStderrMode;
 
 typedef enum {
   LOG_DEBUG_IO = 1u << 0,
   LOG_DEBUG_PROTO = 1u << 1,
   LOG_DEBUG_PACK = 1u << 2,
   LOG_DEBUG_UTIL = 1u << 3,
-  LOG_DEBUG_ALL = (1u << 4) - 1,
+  /* rsync --debug categories that now map to a natural FastSync event:
+   * flist (file-list scan progress), del (deletions), hash/deltasum
+   * (whole-file hashing and delta-sum generation), recv (receiver
+   * responses/signatures), filter (selection/exclusion decisions) and send
+   * (files handed to the sender).  Only emitted when the category is
+   * explicitly enabled; a normal run stays silent. */
+  LOG_DEBUG_FLIST = 1u << 4,
+  LOG_DEBUG_DEL = 1u << 5,
+  LOG_DEBUG_HASH = 1u << 6,
+  LOG_DEBUG_RECV = 1u << 7,
+  LOG_DEBUG_FILTER = 1u << 8,
+  LOG_DEBUG_SEND = 1u << 9,
+  LOG_DEBUG_ALL = (1u << 10) - 1,
 } LogDebugFlag;
 
 typedef enum {
@@ -38,12 +63,16 @@ typedef enum {
      the info_level bitset (there is no separate Config field) and is never set
      by --info=all (which selects level 1). */
   LOG_INFO_NAME_UPTODATE = 1u << 10,
+  /* --info=mount: print rsync's `[sender] skipping mount-point dir NAME` when
+   * -xx/--one-file-system drops a mount-point directory (FastSync's client is
+   * the sender). */
+  LOG_INFO_MOUNT = 1u << 11,
   LOG_INFO_ALL = LOG_INFO_COPY | LOG_INFO_MISC | LOG_INFO_SKIP | LOG_INFO_STATS | LOG_INFO_DEL |
                  LOG_INFO_REMOVE | LOG_INFO_NAME | LOG_INFO_FLIST | LOG_INFO_NONREG |
-                 LOG_INFO_PROGRESS,
+                 LOG_INFO_PROGRESS | LOG_INFO_MOUNT,
 } LogInfoFlag;
 
-void log_message(LogLevel log_level, const char* message, ...);
+void log_message(LogLevel log_level, const char* message, ...) LOG_PRINTF_ATTR(2, 3);
 void log_perror(const char* context);
 void set_log_level(LogLevel level);
 void set_log_debug_flags(uint32_t flags);
@@ -52,14 +81,29 @@ uint32_t get_log_debug_flags(void);
  * the debug log level is enabled AND the flag is selected.  Hot paths use this
  * to skip expensive message formatting/escaping when the line is filtered. */
 bool log_debug_enabled(LogDebugFlag flag);
-void log_debug_message(LogDebugFlag flag, const char* message, ...);
+void log_debug_message(LogDebugFlag flag, const char* message, ...) LOG_PRINTF_ATTR(2, 3);
 void set_log_info_flags(uint32_t flags);
 uint32_t get_log_info_flags(void);
-void log_info_message(LogInfoFlag flag, const char* message, ...);
+void log_info_message(LogInfoFlag flag, const char* message, ...) LOG_PRINTF_ATTR(2, 3);
 void log_set_file(FILE* fp);
 void log_set_8_bit_output(bool enabled);
 bool log_get_8_bit_output(void);
 void log_set_stderr_mode(LogStderrMode mode);
 LogStderrMode log_get_stderr_mode(void);
+/* Write a message a peer forwarded over the client-message channel to this
+ * process's stderr (and log file), with the standard log prefix.  Used by the
+ * server side of rsync's --stderr=client. */
+void log_client_message(const char* message);
+
+/* Sink for LOG_STDERR_CLIENT.  log_message() passes the un-prefixed message
+ * body to the installed sink; a `true` return means the sink took ownership
+ * (e.g. queued it for protocol transmission) and the message must NOT also be
+ * written locally.  A `false` return (or a NULL sink) makes log_message fall
+ * back to the normal local destination, so a diagnostic emitted before the peer
+ * connection exists is never lost (rsync's documented fallback).  The sink may
+ * be called from any thread and must be tolerant of that. */
+typedef bool (*LogClientMsgSink)(const char* message);
+void log_set_client_msg_sink(LogClientMsgSink sink);
+LogClientMsgSink log_get_client_msg_sink(void);
 
 #endif

src/shared/metadata.c

@@ -211,13 +211,22 @@ FileMetadata* metadata_receive(int file_descriptor, int* ok) {
 
 bool metadata_mode_for_policy(mode_t source_mode, mode_t current_mode, FileAttrPolicy policy,
                               mode_t* out_mode) {
+  const mode_t special_bits = (mode_t)(S_ISUID | S_ISGID | S_ISVTX);
   const mode_t execute_bits = S_IXUSR | S_IXGRP | S_IXOTH;
   if (policy.perms) {
     /* rsync --perms copies the source's permission and special bits exactly,
      * including group/other write and setuid/setgid/sticky.  The kernel may
      * still clear setgid when the receiver is not in the file's group; the
-     * caller logs a failed chmod rather than silently masking the bits here. */
-    *out_mode = source_mode & (mode_t)(S_ISUID | S_ISGID | S_ISVTX | 0777);
+     * caller logs a failed chmod rather than silently masking the bits here.
+     * Setuid/setgid/sticky are super-user activities: when the connection did
+     * not permit them (SUPER_MODE_OFF / --no-super) they are stripped, so a
+     * client can never install a privileged bit on a receiver that forbade
+     * super-user activities.  This also covers bits introduced by --chmod,
+     * whose result is fed in as source_mode. */
+    mode_t bits = source_mode & (mode_t)(special_bits | 0777);
+    if (!policy.super_permitted)
+      bits &= ~special_bits;
+    *out_mode = bits;
     return true;
   }
   if (policy.executability) {
@@ -227,8 +236,11 @@ bool metadata_mode_for_policy(mode_t source_mode, mode_t current_mode, FileAttrP
      * execute); otherwise clear every execute bit.  This runs on the
      * destination-derived base (pre-existing dest mode, or source&~umask for a
      * new file), and leaves the special bits untouched.  --perms wins when both
-     * are set (handled above). */
-    mode_t base = current_mode & (mode_t)(S_ISUID | S_ISGID | S_ISVTX | 0777);
+     * are set (handled above).  The destination's own special bits survive
+     * unless super-user activities are forbidden. */
+    mode_t base = current_mode & (mode_t)(special_bits | 0777);
+    if (!policy.super_permitted)
+      base &= ~special_bits;
     if (source_mode & 0111)
       *out_mode = base | ((base & 0444) >> 2);
     else
@@ -240,12 +252,13 @@ bool metadata_mode_for_policy(mode_t source_mode, mode_t current_mode, FileAttrP
 }
 
 FileAttrPolicy file_attr_policy_from_config(const Config* config) {
-  FileAttrPolicy policy = {false, false, false, false};
+  FileAttrPolicy policy = {0};
   if (config) {
     policy.perms = config->preserve_perms;
     policy.times = config->preserve_times;
     policy.atimes = config->preserve_atimes;
     policy.executability = config->use_executability;
+    policy.super_permitted = privilege_super_mode_permitted(config->super_mode);
   }
   return policy;
 }
@@ -314,6 +327,8 @@ bool file_restore_symlink_metadata(const char* path, const FileMetadata* metadat
      transfer never fails over it. */
   if (policy.perms) {
     mode_t link_mode = metadata->mode & (mode_t)(S_ISUID | S_ISGID | S_ISVTX | 0777);
+    if (!policy.super_permitted)
+      link_mode &= ~(mode_t)(S_ISUID | S_ISGID | S_ISVTX);
     if (fchmodat(parent_fd, leaf, link_mode, AT_SYMLINK_NOFOLLOW) != 0 && errno != EOPNOTSUPP &&
         errno != ENOTSUP && errno != ENOSYS) {
       log_message(LOG_LEVEL_DEBUG, "Could not set symlink mode on %s: %s", path, strerror(errno));

src/shared/multiprocessing.c

@@ -34,9 +34,11 @@ PipelineContextSender* pipeline_context_sender_create(Config* config, Queue* que
   context->synced_dirs = NULL;
   context->plan_dirs = NULL;
   context->missing_args = NULL;
+  context->per_dir_rules = NULL;
   context->scan_had_io_error = false;
   context->remove_source_files = NULL;
   context->early_delete = false;
+  context->prescan_chunks = NULL;
   context->delete_plans = NULL;
   context->delete_suppressed = false;
   context->scan_stopped_early = false;
@@ -50,7 +52,9 @@ PipelineContextSender* pipeline_context_sender_create(Config* config, Queue* que
   protocol_session_set_max_alloc(&context->allocation_session, config->max_alloc);
   context->dir_entries = NULL;
   context->dir_entries_mutex_init = false;
+  atomic_init(&context->dir_count, 0);
   context->delete_limit = false;
+  context->partial = false;
   int init = 0;
   if (config->use_metadata) {
     context->dir_entries = array_list_create(file_destroy);
@@ -85,11 +89,13 @@ PipelineContextSender* pipeline_context_sender_create(Config* config, Queue* que
   return context;
 
 fail:
-  log_perror("Error initializing synchronization objects");
+  log_message(LOG_LEVEL_ERROR, "%s", "Error initializing synchronization objects");
   if (context->dir_entries_mutex_init)
     mtx_destroy(&context->dir_entries_mutex);
   if (context->dir_entries)
     array_list_delete(context->dir_entries);
+  if (init >= 7)
+    mtx_destroy(&context->mutex_progress);
   if (init >= 6)
     cnd_destroy(&context->condition_not_empty_loader);
   if (init >= 5)
@@ -191,6 +197,8 @@ void pipeline_context_sender_destroy(PipelineContextSender* context) {
   if (context->manifest) {
     array_list_delete(context->manifest);
   }
+  if (context->prescan_chunks)
+    array_list_delete(context->prescan_chunks);
   if (context->delete_plans)
     delete_plan_sender_destroy(context->delete_plans);
   if (context->excluded_paths)
@@ -203,6 +211,8 @@ void pipeline_context_sender_destroy(PipelineContextSender* context) {
     array_list_delete(context->plan_dirs);
   if (context->missing_args)
     array_list_delete(context->missing_args);
+  if (context->per_dir_rules)
+    filter_rule_list_free(context->per_dir_rules);
   if (context->remove_source_files)
     array_list_delete(context->remove_source_files);
   if (context->dir_entries)

src/shared/multiprocessing.h

@@ -67,6 +67,12 @@ typedef struct {
      them in the manifest frame's third section and the receiver deletes each as
      an explicit request. */
   ArrayList* missing_args;
+  /* Per-directory filter rules the source scan compiled (protocol 2.30.0),
+     sent with the delete manifest/plan config so the receiver can re-derive the
+     per-directory protect/risk set.  NULL when --delete is off.  Populated by
+     the scanner (parallel workers append under mutex_scanner) or the early
+     pre-scan. */
+  FilterRuleList* per_dir_rules;
   /* A source I/O error (unreadable directory) was recorded during the scan.
      Set by the pre-scan (before the threads start) or by the scanner thread
      under mutex_scanner; the caller turns it into a non-zero exit when
@@ -78,6 +84,13 @@ typedef struct {
      path-only pre-scan on the calling thread and the pipeline scanner must not
      append to it.  Set once before the worker threads start. */
   bool early_delete;
+  /* --delete-before: the path-only pre-scan that built the early keep-set,
+     retained as the pipeline's file list (owning Chunk*; consumed and NULLed by
+     the scanner thread) so the data pass replays rsync's single file list
+     instead of re-reading the source.  NULL in every other mode, where the
+     scanner thread scans normally.  Set once before the worker threads start
+     and freed with the context. */
+  ArrayList* prescan_chunks;
   /* Non-NULL for --delete-during/--delete-delay: the per-directory plan set
      prebuilt by the path-only pre-scan on the calling thread.  The sender
      thread transmits the root plan before any data and the remaining plans
@@ -119,10 +132,19 @@ typedef struct {
   ArrayList* dir_entries;
   mtx_t dir_entries_mutex;
   bool dir_entries_mutex_init;
+  /* --stats directory accounting for a `-r` scan (no directory metadata):
+     shared by the parallel scanner workers, read by the sender thread once the
+     scanner is done.  See ScannerOptions.dir_count. */
+  atomic_ullong dir_count;
   /* Set by the sender thread when the receiver reported a --max-delete-capped
      deletion (STATUS_DELETE_LIMIT): the transfer succeeded and the process must
      exit 25 like rsync.  Read by the caller after the sender thread is joined. */
   bool delete_limit;
+  /* Set by the sender thread when the receiver reported STATUS_PARTIAL (a
+     per-entry receiver failure that did not abort the stream): the transfer
+     otherwise succeeded, successfully stored --remove-source-files sources were
+     removed, and the process must exit 23 like rsync.  Read after join. */
+  bool partial;
 } PipelineContextSender;
 
 /* `config` is borrowed and must outlive the context: destroy does NOT free it,

src/shared/protocol.c

@@ -38,6 +38,150 @@ static atomic_ullong io_bytes_read = 0;
 
 static unsigned long long global_bwlimit(void);
 
+/* Runtime whole-file receive bound (see protocol.h).  Resolved once; an
+ * override can only LOWER the ceiling, never raise it above the protocol
+ * constant, so the wire/security bound is unchanged.  A parse failure or a
+ * non-positive value leaves the default in place. */
+unsigned long long protocol_whole_file_receive_limit(void) {
+  static atomic_ullong cached = 0;
+  unsigned long long value = atomic_load_explicit(&cached, memory_order_relaxed);
+  if (value != 0)
+    return value;
+  value = MAX_RECEIVE_WHOLE_FILE_SIZE;
+  const char* env = getenv("FASTSYNC_MAX_WHOLE_FILE_SIZE");
+  if (env && env[0] != '\0') {
+    char* end = NULL;
+    unsigned long long parsed = strtoull(env, &end, 10);
+    if (end && *end == '\0' && parsed > 0 && parsed < value)
+      value = parsed;
+  }
+  atomic_store_explicit(&cached, value, memory_order_relaxed);
+  return value;
+}
+
+/* ------------------------------------------------------------------------- *
+ * Transport vtable implementations.
+ *
+ * Each op performs exactly one transfer attempt.  WANT_READ/WANT_WRITE and an
+ * EINTR-interrupted syscall are reported as PROTOCOL_IO_RETRY (with
+ * *wait_events set to the poll event the caller must wait on); a clean peer
+ * close is PROTOCOL_IO_CLOSED and anything else is PROTOCOL_IO_ERROR.  This
+ * keeps every WANT_READ/WANT_WRITE and EINTR retry exactly where it was before
+ * the vtable was introduced, just moved behind the function pointer.
+ * ------------------------------------------------------------------------- */
+
+static ssize_t plain_io_send(ProtocolSession* session, const void* data, size_t size,
+                             short* wait_events) {
+  ssize_t written = write(session->write_fd, data, size);
+  if (written < 0) {
+    if (errno == EINTR)
+      return PROTOCOL_IO_RETRY;
+    return PROTOCOL_IO_ERROR;
+  }
+  if (written == 0)
+    return PROTOCOL_IO_ERROR;
+  *wait_events = POLLOUT;
+  return written;
+}
+
+static ssize_t plain_io_recv(ProtocolSession* session, void* data, size_t size,
+                             short* wait_events) {
+  ssize_t received = read(session->read_fd, data, size);
+  if (received < 0) {
+    if (errno == EINTR)
+      return PROTOCOL_IO_RETRY;
+    return PROTOCOL_IO_ERROR;
+  }
+  if (received == 0)
+    return PROTOCOL_IO_CLOSED;
+  *wait_events = POLLIN;
+  return received;
+}
+
+static bool plain_io_has_pending(const ProtocolSession* session) {
+  (void)session;
+  return false;
+}
+
+static ssize_t tls_io_send(ProtocolSession* session, const void* data, size_t size,
+                           short* wait_events) {
+  /* SSL_write takes an int length; clamp a >INT_MAX request into chunks so the
+   * size_t downcast can never truncate into a negative/partial write. */
+  size_t chunk = size > (size_t)INT_MAX ? (size_t)INT_MAX : size;
+  ssize_t written = SSL_write(session->ssl, data, (int)chunk);
+  if (written <= 0) {
+    int ssl_err = SSL_get_error(session->ssl, (int)written);
+    if (ssl_err == SSL_ERROR_WANT_WRITE) {
+      *wait_events = POLLOUT;
+      return PROTOCOL_IO_RETRY;
+    }
+    if (ssl_err == SSL_ERROR_WANT_READ) {
+      *wait_events = POLLIN;
+      return PROTOCOL_IO_RETRY;
+    }
+    /* A signal (e.g. Ctrl-C) interrupts the blocking TLS write: retry so the
+     * send loop can observe the abort flag at the next checkpoint.  Only an
+     * actual negative return is an interrupted syscall; a 0-byte SSL_write is
+     * not a valid EINTR retry. */
+    if (written < 0 && ssl_err == SSL_ERROR_SYSCALL && errno == EINTR)
+      return PROTOCOL_IO_RETRY;
+    return PROTOCOL_IO_ERROR;
+  }
+  *wait_events = POLLOUT;
+  return written;
+}
+
+static ssize_t tls_io_recv(ProtocolSession* session, void* data, size_t size, short* wait_events) {
+  /* SSL_read takes an int length; clamp a >INT_MAX request into chunks
+   * (mirrors the send path) so the size_t downcast can never truncate into a
+   * negative/partial read. */
+  size_t chunk = size > (size_t)INT_MAX ? (size_t)INT_MAX : size;
+  ssize_t received = SSL_read(session->ssl, data, (int)chunk);
+  if (received <= 0) {
+    int ssl_err = SSL_get_error(session->ssl, (int)received);
+    if (ssl_err == SSL_ERROR_WANT_WRITE) {
+      *wait_events = POLLOUT;
+      return PROTOCOL_IO_RETRY;
+    }
+    if (ssl_err == SSL_ERROR_WANT_READ) {
+      *wait_events = POLLIN;
+      return PROTOCOL_IO_RETRY;
+    }
+    /* A signal interrupts the blocking TLS read: retry (mirrors the send path)
+     * so the loop reaches its next abort/deadline checkpoint.  Only an actual
+     * negative return is an interrupted syscall: a 0-byte SSL_read is an
+     * unexpected EOF (the peer closed without close_notify), which OpenSSL also
+     * reports as SSL_ERROR_SYSCALL with errno possibly still EINTR from an
+     * earlier interrupted poll/read.  Retrying that would busy-spin the
+     * status-read loop until its deadline, so classify it as closed instead. */
+    if (received < 0 && ssl_err == SSL_ERROR_SYSCALL && errno == EINTR)
+      return PROTOCOL_IO_RETRY;
+    /* A zero-length SSL_read is the peer's clean close_notify (or EOF without
+     * one); report it distinctly so the caller can log it as a close. */
+    if (received == 0)
+      return PROTOCOL_IO_CLOSED;
+    return PROTOCOL_IO_ERROR;
+  }
+  *wait_events = POLLIN;
+  return received;
+}
+
+static bool tls_io_has_pending(const ProtocolSession* session) {
+  return session->ssl != NULL && SSL_pending(session->ssl) > 0;
+}
+
+static const ProtocolIoOps plain_io_ops = {
+    .send = plain_io_send,
+    .recv = plain_io_recv,
+    .has_pending = plain_io_has_pending,
+};
+
+static const ProtocolIoOps tls_io_ops = {
+    .send = tls_io_send,
+    .recv = tls_io_recv,
+    .has_pending = tls_io_has_pending,
+};
+
 static bool protocol_reserve_memory(ProtocolSession* session, size_t charge) {
   unsigned long long allocated = atomic_load(&session->total_allocated_bytes);
   while (true) {
@@ -79,6 +223,7 @@ void io_set_fds(int read_fd, int write_fd) {
   legacy_io_session.read_fd = read_fd;
   legacy_io_session.write_fd = write_fd;
   legacy_io_session.ssl = NULL;
+  legacy_io_session.ops = &plain_io_ops;
   legacy_io_session.eight_bit_output = false;
   atomic_store(&legacy_io_session.total_allocated_bytes, 0);
   legacy_io_session.max_alloc = DEFAULT_MAX_ALLOC;
@@ -91,6 +236,7 @@ void protocol_session_init(ProtocolSession* session, int read_fd, int write_fd)
   memset(session, 0, sizeof(*session));
   session->read_fd = read_fd;
   session->write_fd = write_fd;
+  session->ops = &plain_io_ops;
   session->max_alloc = DEFAULT_MAX_ALLOC;
   session->io_timeout_sec = RECEIVE_TIMEOUT_SEC;
   atomic_init(&session->total_allocated_bytes, 0);
@@ -158,8 +304,12 @@ void protocol_session_unbind(void) {
 }
 
 void protocol_session_set_ssl(ProtocolSession* session, SSL* ssl) {
-  if (session)
-    session->ssl = ssl;
+  if (!session)
+    return;
+  session->ssl = ssl;
+  /* Select the transport dispatch once, here, instead of branching on the SSL
+   * pointer inside every I/O loop. */
+  session->ops = ssl ? &tls_io_ops : &plain_io_ops;
 }
 
 static void bw_mutex_init(void) {
@@ -270,6 +420,20 @@ SSL* io_get_ssl(void) {
   return io_ssl;
 }
 
+SSL* protocol_current_ssl(void) {
+  /* The bound session is the authoritative transport for a worker thread: it
+   * was explicitly handed to protocol_session_bind() and carries its own SSL,
+   * whereas io_ssl is thread-local and NULL in a thread that never performed
+   * the handshake.  Only a session whose selected dispatch is TLS may supply
+   * the SSL: a bound plaintext session has ssl == NULL and must not shadow a
+   * live thread-local io_ssl, or file_send.c would take the raw sendfile(2)
+   * path on a socket this thread is driving with TLS.  With no TLS session
+   * bound (plaintext session, or the fd-shim path), fall back to io_ssl. */
+  if (bound_session && bound_session->ops == &tls_io_ops && bound_session->ssl)
+    return bound_session->ssl;
+  return io_ssl;
+}
+
 unsigned long long protocol_bytes_written(void) {
   return atomic_load(&io_bytes_written);
 }
@@ -298,9 +462,21 @@ static ProtocolSession* legacy_session(int read_fd, int write_fd) {
     protocol_session_set_bwlimit(&legacy_io_session, global_bwlimit());
   }
   legacy_io_session.ssl = io_ssl;
+  legacy_io_session.ops = io_ssl ? &tls_io_ops : &plain_io_ops;
   return &legacy_io_session;
 }
 
+/* Pace an out-of-band write that bypassed protocol_send_n_data (the plaintext
+ * sendfile fast path).  The bound/legacy session is resolved exactly as the
+ * preceding send_n_data(fd, ...) resolved it, so the same token-bucket state is
+ * throttled and the TLS and plaintext transports share identical --bwlimit
+ * semantics.  Passing the wire fd (rather than -1) is essential: the sendfile
+ * send left legacy_io_session.write_fd bound to it, so resolving with -1 would
+ * mismatch, re-initialize the session and hand out a second first-call burst. */
+void protocol_throttle_bytes(int file_descriptor, size_t bytes) {
+  bw_throttle_session(legacy_session(-1, file_descriptor), bytes);
+}
+
 bool send_n_data(int file_descriptor, const void* data, size_t data_size) {
   return protocol_send_n_data(legacy_session(-1, file_descriptor), data, data_size);
 }
@@ -324,8 +500,9 @@ bool protocol_send_n_data(ProtocolSession* session, const void* data, size_t dat
   if (!data && data_size != 0)
     return false;
   log_debug_message(LOG_DEBUG_IO, "    Sending n Data: %zu", data_size);
-  if (!session)
+  if (!session || !session->ops)
     return false;
+  const ProtocolIoOps* ops = session->ops;
   /* A non-positive session timeout disables the deadline entirely (rsync's
    * --timeout=0 default); poll then blocks until the socket becomes writable. */
   int timeout_sec = session->io_timeout_sec > 0 ? session->io_timeout_sec : 0;
@@ -351,38 +528,18 @@ bool protocol_send_n_data(ProtocolSession* session, const void* data, size_t dat
       continue;
     if (pfd.revents & (POLLERR | POLLNVAL))
       return false;
-    ssize_t bytes_send;
-    if (session->ssl) {
-      /* SSL_write takes an int length; clamp a >INT_MAX request into chunks so
-       * the size_t downcast can never truncate into a negative/partial write. */
-      size_t ssl_chunk = chunk > (size_t)INT_MAX ? (size_t)INT_MAX : chunk;
-      bytes_send = SSL_write(session->ssl, (const char*)data + total_bytes_send, (int)ssl_chunk);
-    } else {
-      bytes_send = write(fd, (const char*)data + total_bytes_send, chunk);
-    }
+    ssize_t bytes_send =
+        ops->send(session, (const char*)data + total_bytes_send, chunk, &wait_events);
+    if (bytes_send == PROTOCOL_IO_RETRY)
+      continue;
     if (bytes_send <= 0) {
-      if (session->ssl) {
-        int ssl_err = SSL_get_error(session->ssl, (int)bytes_send);
-        if (ssl_err == SSL_ERROR_WANT_WRITE || ssl_err == SSL_ERROR_WANT_READ) {
-          wait_events = ssl_err == SSL_ERROR_WANT_WRITE ? POLLOUT : POLLIN;
-          continue;
-        }
-        /* A signal (e.g. Ctrl-C) interrupts the blocking TLS write: retry so
-           the send loop can observe the abort flag at the next checkpoint. */
-        if (ssl_err == SSL_ERROR_SYSCALL && errno == EINTR)
-          continue;
-      } else if (errno == EINTR) {
-        continue;
-      }
       log_message(LOG_LEVEL_ERROR, "Could not send data");
       return false;
     }
     bw_throttle_session(session, (size_t)bytes_send);
     total_bytes_send += bytes_send;
-    if (session->ssl)
-      wait_events = POLLOUT;
   }
-  log_debug_message(LOG_DEBUG_IO, "    Send n Data: %zu", total_bytes_send);
+  log_debug_message(LOG_DEBUG_IO, "    Send n Data: %zd", total_bytes_send);
   atomic_fetch_add(&io_bytes_written, (unsigned long long)total_bytes_send);
   return true;
 }
@@ -413,14 +570,15 @@ bool protocol_receive_n_data(ProtocolSession* session, void* data, size_t data_s
 static bool protocol_receive_n_data_until(ProtocolSession* session, void* data, size_t data_size,
                                           const struct timespec* deadline) {
   log_debug_message(LOG_DEBUG_IO, "    Receiving n Data: %zu", data_size);
-  if (!session)
+  if (!session || !session->ops)
     return false;
+  const ProtocolIoOps* ops = session->ops;
   int fd = session->read_fd;
 
   size_t total_bytes_received = 0;
   short wait_events = POLLIN;
   while (total_bytes_received < data_size) {
-    if (!session->ssl || SSL_pending(session->ssl) == 0) {
+    if (!ops->has_pending(session)) {
       struct pollfd pfd = {.fd = fd, .events = wait_events};
       /* A NULL deadline means "wait indefinitely" (timeout disabled). */
       int poll_result = poll(&pfd, 1, deadline ? deadline_remaining_ms(deadline) : -1);
@@ -438,37 +596,19 @@ static bool protocol_receive_n_data_until(ProtocolSession* session, void* data,
         return false;
     }
 
-    ssize_t bytes_received;
-    if (session->ssl)
-      bytes_received = SSL_read(session->ssl, (char*)data + total_bytes_received,
-                                data_size - total_bytes_received);
-    else
-      bytes_received =
-          read(fd, (char*)data + total_bytes_received, data_size - total_bytes_received);
+    ssize_t bytes_received = ops->recv(session, (char*)data + total_bytes_received,
+                                       data_size - total_bytes_received, &wait_events);
+    if (bytes_received == PROTOCOL_IO_RETRY)
+      continue;
+    if (bytes_received == PROTOCOL_IO_CLOSED) {
+      log_message(LOG_LEVEL_ERROR, "Connection closed while receiving data");
+      return false;
+    }
     if (bytes_received <= 0) {
-      if (session->ssl) {
-        int ssl_err = SSL_get_error(session->ssl, (int)bytes_received);
-        if (ssl_err == SSL_ERROR_WANT_WRITE || ssl_err == SSL_ERROR_WANT_READ) {
-          wait_events = ssl_err == SSL_ERROR_WANT_WRITE ? POLLOUT : POLLIN;
-          continue;
-        }
-        /* A signal interrupts the blocking TLS read: retry (mirrors the send
-           path and protocol_read_status_until) so the loop reaches its next
-           abort/deadline checkpoint instead of failing spuriously. */
-        if (ssl_err == SSL_ERROR_SYSCALL && errno == EINTR)
-          continue;
-      } else if (errno == EINTR) {
-        continue;
-      }
-      if (bytes_received == 0)
-        log_message(LOG_LEVEL_ERROR, "Connection closed while receiving data");
-      else
-        log_message(LOG_LEVEL_ERROR, "Could not receive bytes");
+      log_message(LOG_LEVEL_ERROR, "Could not receive bytes");
       return false;
     }
     total_bytes_received += (size_t)bytes_received;
-    if (session->ssl)
-      wait_events = POLLIN;
   }
   log_debug_message(LOG_DEBUG_IO, "    Received n Data: %zu", total_bytes_received);
   atomic_fetch_add(&io_bytes_read, (unsigned long long)total_bytes_received);
@@ -545,11 +685,24 @@ static const char* status_to_string(Status status) {
     return "DELETE_LIMIT";
   case STATUS_DEST_INFO:
     return "DEST_INFO";
+  case STATUS_CLIENT_MSG:
+    return "CLIENT_MSG";
+  case STATUS_PARTIAL:
+    return "PARTIAL";
   default:
     return "UNKNOWN";
   }
 }
 
+/* Reject a raw wire status outside the known enum range before it is handed to
+ * callers, so an unknown/corrupt frame fails as a protocol error instead of
+ * being silently interpreted as an unexpected-but-valid verdict.  STATUS_OK is
+ * the first enumerator and STATUS_PARTIAL the last, so the range check accepts
+ * every status the protocol defines. */
+static bool status_is_valid(Status status) {
+  return status >= STATUS_OK && status <= STATUS_PARTIAL;
+}
+
 /* Shared string send/receive implementation.  `redact` selects whether the
  * payload body is written to the LOG_DEBUG_PROTO debug log: daemon auth material
  * (the username and the proof/signature fields) sets it so a --verbose log never
@@ -633,21 +786,15 @@ bool protocol_send_data(ProtocolSession* session, const Data* data) {
     return false;
   if (!protocol_send_n_data(session, data->data, data_size))
     return false;
-  log_debug_message(LOG_DEBUG_PROTO, "Send %lld data", data_size);
+  log_debug_message(LOG_DEBUG_PROTO, "Send %llu data", data_size);
   return true;
 }
 
-Data* protocol_receive_data_limited(ProtocolSession* session, unsigned long long maximum_size) {
+Data* protocol_receive_data_alloc(ProtocolSession* session, unsigned long long size) {
   if (!session)
     return NULL;
-  unsigned long long size = 0;
-  if (!protocol_receive_n_data(session, &size, sizeof(unsigned long long)))
+  if (size > MAX_DATA_PAYLOAD_SIZE)
     return NULL;
-  if (size > MAX_DATA_PAYLOAD_SIZE || size > maximum_size) {
-    log_message(LOG_LEVEL_ERROR, "Data size %llu exceeds maximum %llu", size,
-                (unsigned long long)MAX_DATA_PAYLOAD_SIZE);
-    return NULL;
-  }
   if (size > SIZE_MAX)
     return NULL;
   size_t allocation_size = size == 0 ? 1 : (size_t)size;
@@ -662,12 +809,6 @@ Data* protocol_receive_data_limited(ProtocolSession* session, unsigned long long
     protocol_release_memory_for_session(session, allocation_size);
     return NULL;
   }
-  if (!protocol_receive_n_data(session, data, (size_t)size)) {
-    free(data);
-    protocol_release_memory_for_session(session, allocation_size);
-    return NULL;
-  }
-  log_debug_message(LOG_DEBUG_PROTO, "Received %lld data", size);
   Data* result = data_create(data, (size_t)size);
   if (!result) {
     protocol_release_memory_for_session(session, allocation_size);
@@ -678,6 +819,32 @@ Data* protocol_receive_data_limited(ProtocolSession* session, unsigned long long
   return result;
 }
 
+Data* protocol_receive_data_body(ProtocolSession* session, unsigned long long size) {
+  Data* result = protocol_receive_data_alloc(session, size);
+  if (!result)
+    return NULL;
+  if (!protocol_receive_n_data(session, result->data, (size_t)size)) {
+    data_destroy(result);
+    return NULL;
+  }
+  log_debug_message(LOG_DEBUG_PROTO, "Received %llu data", size);
+  return result;
+}
+
+Data* protocol_receive_data_limited(ProtocolSession* session, unsigned long long maximum_size) {
+  if (!session)
+    return NULL;
+  unsigned long long size = 0;
+  if (!protocol_receive_n_data(session, &size, sizeof(unsigned long long)))
+    return NULL;
+  if (size > MAX_DATA_PAYLOAD_SIZE || size > maximum_size) {
+    log_message(LOG_LEVEL_ERROR, "Data size %llu exceeds maximum %llu", size,
+                (unsigned long long)MAX_DATA_PAYLOAD_SIZE);
+    return NULL;
+  }
+  return protocol_receive_data_body(session, size);
+}
+
 bool protocol_send_int(ProtocolSession* session, int data) {
   if (!protocol_send_n_data(session, &data, sizeof(int)))
     return false;
@@ -777,6 +944,10 @@ bool protocol_receive_status(ProtocolSession* session, Status* status) {
   }
   if (!protocol_receive_n_data_until(session, status, sizeof(Status), deadline_ptr))
     return false;
+  if (!status_is_valid(*status)) {
+    log_message(LOG_LEVEL_ERROR, "Received unknown protocol status %d", *status);
+    return false;
+  }
   if (!protocol_capture_error_detail(session, status, deadline_ptr, NULL))
     return false;
   log_debug_message(LOG_DEBUG_PROTO, "Received Status: %s", status_to_string(*status));
@@ -798,6 +969,10 @@ bool protocol_receive_status_timed(ProtocolSession* session, Status* status, int
   deadline.tv_sec += timeout_sec;
   if (!protocol_receive_n_data_until(session, status, sizeof(Status), &deadline))
     return false;
+  if (!status_is_valid(*status)) {
+    log_message(LOG_LEVEL_ERROR, "Received unknown protocol status %d", *status);
+    return false;
+  }
   if (!protocol_capture_error_detail(session, status, &deadline, NULL))
     return false;
   log_debug_message(LOG_DEBUG_PROTO, "Received Status: %s", status_to_string(*status));
@@ -811,11 +986,14 @@ bool protocol_receive_status_timed(ProtocolSession* session, Status* status, int
  * reply across a frame boundary.  Returns false on timeout/EOF/error. */
 static bool protocol_read_status_until(ProtocolSession* session, Status* status,
                                        const struct timespec* deadline) {
+  if (!session || !session->ops)
+    return false;
+  const ProtocolIoOps* ops = session->ops;
   Status received = STATUS_ERROR;
   size_t got = 0;
   short wait_events = POLLIN;
   while (got < sizeof(Status)) {
-    if (!session->ssl || SSL_pending(session->ssl) == 0) {
+    if (!ops->has_pending(session)) {
       int remaining_ms = deadline ? deadline_remaining_ms(deadline) : -1;
       if (remaining_ms == 0) {
         log_message(LOG_LEVEL_ERROR, "Receive timeout while reading status");
@@ -835,21 +1013,11 @@ static bool protocol_read_status_until(ProtocolSession* session, Status* status,
       if (pfd.revents & (POLLERR | POLLNVAL))
         return false;
     }
-    ssize_t bytes_received;
-    if (session->ssl)
-      bytes_received = SSL_read(session->ssl, (char*)&received + got, sizeof(Status) - got);
-    else
-      bytes_received = read(session->read_fd, (char*)&received + got, sizeof(Status) - got);
+    ssize_t bytes_received =
+        ops->recv(session, (char*)&received + got, sizeof(Status) - got, &wait_events);
+    if (bytes_received == PROTOCOL_IO_RETRY)
+      continue;
     if (bytes_received <= 0) {
-      if (session->ssl) {
-        int ssl_err = SSL_get_error(session->ssl, (int)bytes_received);
-        if (ssl_err == SSL_ERROR_WANT_READ || ssl_err == SSL_ERROR_WANT_WRITE) {
-          wait_events = ssl_err == SSL_ERROR_WANT_WRITE ? POLLOUT : POLLIN;
-          continue;
-        }
-      }
-      if (bytes_received < 0 && errno == EINTR)
-        continue;
       log_message(LOG_LEVEL_ERROR, "Connection closed while receiving status");
       return false;
     }
@@ -878,7 +1046,7 @@ bool protocol_receive_status_keepalive(ProtocolSession* session, Status* status,
   while (true) {
     if (abort_check && abort_check())
       return false;
-    if (!session->ssl || SSL_pending(session->ssl) == 0) {
+    if (!session->ops || !session->ops->has_pending(session)) {
       int remaining_ms = deadline_remaining_ms(&deadline);
       if (remaining_ms <= 0) {
         log_message(LOG_LEVEL_ERROR, "Receive timeout after %ds", timeout_sec);
@@ -911,6 +1079,10 @@ bool protocol_receive_status_keepalive(ProtocolSession* session, Status* status,
     Status received;
     if (!protocol_read_status_until(session, &received, &deadline))
       return false;
+    if (!status_is_valid(received)) {
+      log_message(LOG_LEVEL_ERROR, "Received unknown protocol status %d", received);
+      return false;
+    }
     if (!protocol_capture_error_detail(session, &received, &deadline, abort_check))
       return false;
     if (received == STATUS_KEEPALIVE) {
@@ -977,6 +1149,12 @@ Data* receive_data(int fd) {
 Data* receive_data_limited(int fd, unsigned long long maximum_size) {
   return protocol_receive_data_limited(legacy_session(fd, -1), maximum_size);
 }
+Data* receive_data_body(int fd, unsigned long long size) {
+  return protocol_receive_data_body(legacy_session(fd, -1), size);
+}
+Data* receive_data_alloc(int fd, unsigned long long size) {
+  return protocol_receive_data_alloc(legacy_session(fd, -1), size);
+}
 bool send_int(int fd, int data) {
   return protocol_send_int(legacy_session(-1, fd), data);
 }
@@ -1011,6 +1189,19 @@ bool send_error_detail(int fd, const char* message) {
   return send_status(fd, STATUS_ERROR_DETAIL) && send_str(fd, message);
 }
 
+bool send_client_message(int fd, const char* message) {
+  if (!message)
+    message = "";
+  char bounded[MAX_CLIENT_MSG_BYTES + 1];
+  size_t len = strlen(message);
+  if (len > MAX_CLIENT_MSG_BYTES) {
+    memcpy(bounded, message, MAX_CLIENT_MSG_BYTES);
+    bounded[MAX_CLIENT_MSG_BYTES] = '\0';
+    message = bounded;
+  }
+  return send_status(fd, STATUS_CLIENT_MSG) && send_str(fd, message);
+}
+
 const char* protocol_last_error(void) {
   return io_error_detail;
 }

src/shared/protocol.h

@@ -15,6 +15,12 @@
  * this for a rejection and the detail frame stays a small, fixed bound. */
 #define MAX_ERROR_DETAIL_BYTES 4096
 
+/* Hard cap on a client diagnostic forwarded over the STATUS_CLIENT_MSG channel
+ * (protocol 2.30.0, rsync's --stderr=client).  The body is reused from the
+ * bounded-string wire helper and sliced to this many bytes before it is sent,
+ * so a peer can never be made to retain more than this per message. */
+#define MAX_CLIENT_MSG_BYTES 4096
+
 /* Maximum uncompressed file payload accepted by the receiver's whole-file
  * paths.  A single whole file is charged against the per-connection memory
  * reservation (MAX_CONNECTION_MEMORY) and against the server allocation
@@ -26,8 +32,22 @@
 /* Maximum allowed data payload size for receive_data (whole-file bound) */
 #define MAX_DATA_PAYLOAD_SIZE MAX_RECEIVE_WHOLE_FILE_SIZE
 
+/* Runtime whole-file receive bound.  It defaults to MAX_RECEIVE_WHOLE_FILE_SIZE
+ * and exists so the test suite can lower the ceiling (via the
+ * FASTSYNC_MAX_WHOLE_FILE_SIZE environment variable, a byte count) and exercise
+ * the streaming path with a small, fast transfer.  A payload at or below the
+ * bound keeps the historical whole-buffer path; a larger one is streamed
+ * through a bounded buffer.  The value is resolved once per process and never
+ * exceeds the compile-time ceiling, so a malicious environment cannot raise it
+ * beyond the protocol limit. */
+unsigned long long protocol_whole_file_receive_limit(void);
+
 /* Maximum chunk size (64 MB) — prevents unbounded allocation from the wire */
 #define MAX_CHUNK_SIZE (64ULL * 1024 * 1024)
+/* Files larger than this are not kept fully in memory while loading: the
+ * loader skips them so the sender streams from the path, and file_checksum
+ * hashes them from disk in bounded buffers instead of forcing a full load. */
+#define STREAM_THRESHOLD (64ULL * 1024 * 1024)
 #define MAX_MANIFEST_ENTRIES (1024 * 1024)
 /* Aggregate bytes retained by one received deletion manifest. */
 #define MAX_MANIFEST_BYTES (16ULL * 1024 * 1024)
@@ -46,16 +66,48 @@
 
 typedef struct ssl_st SSL;
 
+typedef struct ProtocolSession ProtocolSession;
+
+/*
+ * Transport vtable: the per-session set of I/O primitives the three protocol
+ * loops (send, receive, status-read) dispatch through.  The ops are selected
+ * once, when the session is initialized or its SSL is installed, so the loops
+ * never branch on the transport at runtime.  A plaintext session uses the
+ * read()/write() ops; a TLS session uses the SSL_read()/SSL_write() ops.
+ *
+ * `send`/`recv` attempt exactly one transfer and return:
+ *   > 0                    bytes transferred,
+ *   PROTOCOL_IO_RETRY      no progress; poll on *wait_events and retry,
+ *   PROTOCOL_IO_CLOSED     peer closed the stream,
+ *   PROTOCOL_IO_ERROR      fatal transport error.
+ * `has_pending` reports bytes already buffered by the transport (a TLS record
+ * residue); the receive loops skip the poll() gate when it is true.
+ */
+typedef struct ProtocolIoOps {
+  ssize_t (*send)(ProtocolSession* session, const void* data, size_t size, short* wait_events);
+  ssize_t (*recv)(ProtocolSession* session, void* data, size_t size, short* wait_events);
+  bool (*has_pending)(const ProtocolSession* session);
+} ProtocolIoOps;
+
+/* Negative sentinels returned by ProtocolIoOps.send/recv (see above). */
+enum {
+  PROTOCOL_IO_RETRY = -1,
+  PROTOCOL_IO_CLOSED = -2,
+  PROTOCOL_IO_ERROR = -3,
+};
+
 /*
  * Explicit owner of protocol I/O.  A session does not own the descriptors or
  * SSL object; it only describes the transport used by a transfer.  This makes
  * it safe to pass the transport to a worker without relying on inherited
  * thread-local state.
  */
-typedef struct ProtocolSession {
+struct ProtocolSession {
   int read_fd;
   int write_fd;
   SSL* ssl;
+  /* Transport dispatch selected by protocol_session_init()/set_ssl(). */
+  const ProtocolIoOps* ops;
   unsigned long long bwlimit;
   long long bw_tokens;
   long long bw_last_refill_sec;
@@ -71,7 +123,7 @@ typedef struct ProtocolSession {
    * SO_RCVTIMEO/SO_SNDTIMEO.  The server does not propagate a client 0 here: it
    * installs protocol_server_io_timeout_sec() so its sessions keep a floor. */
   int io_timeout_sec;
-} ProtocolSession;
+};
 
 typedef int Status;
 enum NET_STATUS {
@@ -87,8 +139,13 @@ enum NET_STATUS {
   STATUS_KEEPALIVE,
   STATUS_ABORT,
   STATUS_CHECK_BATCH,
-  /* An explicit directory entry (--dirs): the sender transmits only the path;
-   * the receiver creates the directory below the receive root. */
+  /* An explicit directory entry (--dirs / an empty source directory): the sender
+   * transmits the path and, when metadata/xattrs are negotiated, their blocks;
+   * the receiver creates the directory below the receive root.  Protocol 2.30.0
+   * inserts an int32 probe flag right after the status when report_dest_info is
+   * negotiated: probe=1 is a report-only frame (path only; the receiver answers
+   * STATUS_DEST_INFO and creates nothing), probe=0 is a real create that is
+   * answered with the directory's pre-transfer state before it is created. */
   STATUS_MKDIR,
   /* --append / --append-verify tail resume.  STATUS_APPEND is sent by the
    * receiver after a per-file STATUS_CHECK when the existing destination file
@@ -171,16 +228,22 @@ enum NET_STATUS {
    * limit stopped deletions").  Appended after STATUS_DRY_RUN_TRANSFER so no
    * existing status is renumbered. */
   STATUS_DELETE_LIMIT,
-  /* Destination-state report for output parity (protocol 2.23.0).  When the
-   * wire config carries report_dest_info=true, the receiver answers every
-   * per-file STATUS_CHECK request with STATUS_DEST_INFO FIRST, followed by a
-   * fixed record describing the pre-transfer destination entry
-   * (int32 has_old; uint64 size; int64 mtime; int64 mtime_nsec; uint32 mode;
-   * int32 uid; int32 gid).  The ordinary STATUS_OK/STATUS_NEXT/... verdict
-   * follows, so the sender can render rsync-accurate -i/--out-format columns
-   * (new vs modified, and which of size/time/perms/owner/group differ) without
-   * changing the transfer decision itself.  Appended after
-   * STATUS_DELETE_LIMIT so no existing status is renumbered. */
+  /* Destination-state report for output parity (protocol 2.23.0; extended to
+   * directories/symlinks in 2.30.0).  When the wire config carries
+   * report_dest_info=true, the receiver answers every per-file STATUS_CHECK
+   * request with STATUS_DEST_INFO FIRST, followed by a fixed record describing
+   * the pre-transfer destination entry (int32 has_old; int32 target_matches;
+   * uint64 size; int64 mtime; int64 mtime_nsec; uint32 mode; int32 uid;
+   * int32 gid).  The ordinary STATUS_OK/STATUS_NEXT/... verdict follows, so the
+   * sender can render rsync-accurate -i/--out-format columns (new vs modified,
+   * and which of size/time/perms/owner/group differ) without changing the
+   * transfer decision itself.  Protocol 2.30.0 also uses this record for
+   * STATUS_MKDIR and STATUS_SYMLINK: the sender consumes it into the entry's
+   * dest_state before emitting its change line, and target_matches reports
+   * whether an existing symlink's on-disk target already equals the incoming
+   * one (so the sender can render `cLc........` vs `.L..t......` and suppress
+   * an unchanged symlink).  Appended after STATUS_DELETE_LIMIT so no existing
+   * status is renumbered. */
   STATUS_DEST_INFO,
   /* Per-directory delete plan (protocol 2.24.0).  The sender of a
    * --delete-during/--delete-delay transfer streams one frame per source
@@ -202,9 +265,29 @@ enum NET_STATUS {
    * config carries report_stats=true, the receiver sends this status once,
    * immediately before its terminal success status, followed by a fixed stats
    * record (see format_stats_send/receive in format.h) and, when the run is a
-   * --dry-run with --delete, the would-delete path list.  Appended after
-   * STATUS_DELETE_PLAN so no existing status is renumbered. */
-  STATUS_STATS
+   * --dry-run with --delete, the would-delete path list.  Protocol 2.30.0
+   * appends the four deleted_reg/dir/link/special counters to that record, so
+   * --stats can render rsync's `Number of deleted files` per-type breakdown.
+   * Appended after STATUS_DELETE_PLAN so no existing status is renumbered. */
+  STATUS_STATS,
+  /* Client diagnostic channel (protocol 2.30.0, rsync's --stderr=client /
+   * --no-msgs2stderr).  When the client's --stderr mode is `client`, the
+   * client forwards its own diagnostics over this client->server frame
+   * (STATUS_CLIENT_MSG followed by a bounded length-prefixed string, capped at
+   * MAX_CLIENT_MSG_BYTES) instead of writing them to its local stderr.  The
+   * receiver reads the string and writes it to the server's stderr (respecting
+   * the server log destination).  Appended after STATUS_STATS so no existing
+   * status is renumbered. */
+  STATUS_CLIENT_MSG,
+  /* Receiver-side partial transfer (protocol 2.30.0).  Sent by the receiver as
+   * the terminal status INSTEAD of STATUS_OK when one or more entries failed
+   * per-entry without aborting the stream (currently a --devices mknod
+   * EPERM/EACCES).  The transfer otherwise succeeded and every successfully
+   * stored file was acknowledged, so the sender may still remove
+   * --remove-source-files sources; the sender maps this to rsync's exit code
+   * 23 ("partial transfer due to error"), distinct from a fatal STATUS_ERROR.
+   * Appended after STATUS_CLIENT_MSG so no existing status is renumbered. */
+  STATUS_PARTIAL
 };
 
 void io_set_fds(int read_fd, int write_fd);
@@ -212,6 +295,17 @@ void io_set_bwlimit(unsigned long long bytes_per_sec);
 unsigned long long io_get_bwlimit(void);
 void io_set_ssl(SSL* ssl);
 SSL* io_get_ssl(void);
+/* SSL object of the transport in effect on this thread: the currently bound
+ * session's SSL when a TLS session is bound, otherwise the legacy thread-local
+ * io_ssl.  NULL for a plaintext transport.  Unlike io_get_ssl(), this resolves
+ * worker threads that bound a TLS session via protocol_session_set_ssl()/
+ * protocol_session_bind() but never called io_set_ssl() themselves (C11
+ * _Thread_local state is not inherited by a new thread).  A bound session only
+ * wins when its selected dispatch is TLS; a bound plaintext session (ssl ==
+ * NULL) falls back to io_ssl so it can never mask a live encrypted transport.
+ * Callers that must choose a TLS-only code path (e.g. file_send.c's sendfile
+ * fallback) must use this instead of io_get_ssl(). */
+SSL* protocol_current_ssl(void);
 
 /* Process-wide wire byte counters.  protocol_send_n_data/protocol_receive_n_data
  * update them; the zero-copy sendfile path reports through
@@ -220,6 +314,15 @@ SSL* io_get_ssl(void);
 unsigned long long protocol_bytes_written(void);
 unsigned long long protocol_bytes_read(void);
 void protocol_note_bytes_written(unsigned long long bytes);
+/* Apply --bwlimit pacing to bytes written outside protocol_send_n_data (the
+ * plaintext zero-copy sendfile fast path).  `file_descriptor` is the wire fd
+ * the bytes were written to, so the legacy session is resolved exactly as the
+ * preceding send_n_data call resolved it (the bound TLS session still wins when
+ * set); resolving with the same fd avoids re-initializing the legacy session
+ * and granting a second first-call burst.  Runs the same token-bucket throttle,
+ * so the sendfile transport is paced identically to the buffered/TLS paths.  A
+ * no-op when the effective session has no bandwidth limit. */
+void protocol_throttle_bytes(int file_descriptor, size_t bytes);
 
 void protocol_session_init(ProtocolSession* session, int read_fd, int write_fd);
 /* Transitional bridge for helpers whose signatures still carry only an fd. */
@@ -263,6 +366,9 @@ bool protocol_send_int(ProtocolSession* session, int data);
 bool protocol_receive_int(ProtocolSession* session, int* data);
 bool protocol_send_status(ProtocolSession* session, Status status);
 bool protocol_receive_status(ProtocolSession* session, Status* status);
+/* As protocol_receive_status, but with an explicit per-message deadline
+ * (seconds) instead of the session's configured io_timeout_sec. */
+bool protocol_receive_status_timed(ProtocolSession* session, Status* status, int timeout_sec);
 bool send_n_data(int file_descriptor, const void* data, size_t data_size);
 bool receive_n_data(int file_descriptor, void* data, size_t data_size);
 
@@ -274,6 +380,15 @@ char* receive_str_redacted(int file_descriptor);
 bool send_data(int file_descriptor, const Data* data);
 Data* receive_data(int file_descriptor);
 Data* receive_data_limited(int file_descriptor, unsigned long long maximum_size);
+/* Read exactly `size` bytes as a charged Data body.  The length-prefixed
+ * receive_data_limited() reads the header itself; this variant is for callers
+ * that must inspect the declared size (and possibly stream the body instead)
+ * before allocating.  `size` must already be within MAX_DATA_PAYLOAD_SIZE. */
+Data* receive_data_body(int file_descriptor, unsigned long long size);
+/* Allocate (and charge) a `size`-byte Data body without reading it; the caller
+ * fills `result->data` itself.  Used when a frame's leading bytes must be
+ * inspected before the rest of the body is read. */
+Data* receive_data_alloc(int file_descriptor, unsigned long long size);
 bool send_int(int file_descriptor, int data);
 bool receive_int(int file_descriptor, int* data);
 bool send_status(int file_descriptor, Status status);
@@ -282,6 +397,11 @@ bool receive_status(int file_descriptor, Status* status);
  * length-prefixed string.  Over-long messages are sliced and NULL is treated
  * as "".  Returns false if the status or the string could not be sent. */
 bool send_error_detail(int file_descriptor, const char* message);
+/* Send STATUS_CLIENT_MSG followed by a bounded (<= MAX_CLIENT_MSG_BYTES)
+ * length-prefixed string carrying a client diagnostic.  Over-long messages are
+ * sliced and NULL is treated as "".  Returns false if the status or the string
+ * could not be sent. */
+bool send_client_message(int file_descriptor, const char* message);
 /* Human-readable reason captured from the most recent STATUS_ERROR_DETAIL
  * received on this thread, or "" when the last status was a bare STATUS_ERROR
  * (or no detail was seen).  Thread-local, and valid until the next non-keepalive

src/shared/queue.c

@@ -128,7 +128,7 @@ bool queue_enqueue_multithreaded_cancel(Queue* queue, void* item, mtx_t* mutex,
 
 void* queue_dequeue(Queue* queue) {
   if (queue == NULL || queue_is_empty(queue)) {
-    log_perror("ERROR: Could not dequeue from null or empty queue.");
+    log_message(LOG_LEVEL_ERROR, "%s", "ERROR: Could not dequeue from null or empty queue.");
     return NULL;
   }
 
@@ -139,6 +139,23 @@ void* queue_dequeue(Queue* queue) {
   return item;
 }
 
+bool queue_push(Queue* queue, void* item) {
+  return queue_enqueue(queue, item);
+}
+
+void* queue_pop(Queue* queue) {
+  if (queue == NULL || queue_is_empty(queue)) {
+    log_message(LOG_LEVEL_ERROR, "%s", "ERROR: Could not pop from null or empty queue.");
+    return NULL;
+  }
+
+  queue->rear = (queue->rear - 1 + queue->capacity) % queue->capacity;
+  void* item = queue->items[queue->rear];
+  queue->items[queue->rear] = NULL;
+  queue->size--;
+  return item;
+}
+
 void* queue_dequeue_multithreaded(Queue* queue, mtx_t* mutex, cnd_t* condition_not_empty,
                                   cnd_t* condition_not_full, const bool* other_thread_done) {
   mtx_lock(mutex);

src/shared/queue.h

@@ -28,4 +28,11 @@ void* queue_dequeue(Queue* queue);
 void* queue_dequeue_multithreaded(Queue* queue, mtx_t* mutex, cnd_t* condition_not_empty,
                                   cnd_t* condition_not_full, const bool* other_thread_done);
 
+/* LIFO stack operations over the same ring buffer.  queue_push() is the enqueue
+   primitive; queue_pop() removes from the rear, so a sequence of pushes is
+   returned in reverse order.  Used by the sequential scanner's depth-first
+   traversal. */
+bool queue_push(Queue* queue, void* item);
+void* queue_pop(Queue* queue);
+
 #endif

src/shared/transport_ssh.c

@@ -87,7 +87,7 @@ static int parse_remote_dest(const char* dest, RemoteDest* r) {
   return 0;
 }
 
-char* ssh_build_remote_command(const char* server_path, bool old_args, char* const* remote_options,
+char* ssh_build_remote_command(const char* server_path, char* const* remote_options,
                                int remote_option_count) {
   const char* path = server_path ? server_path : "fastsync-server";
   const char* suffix = " --stdio";
@@ -105,9 +105,7 @@ char* ssh_build_remote_command(const char* server_path, bool old_args, char* con
      shell word (remote options below reuse the same escaping), then
      " --stdio".  Quoting the path is the only injection-safe construction: an
      unquoted path would carry shell metacharacters straight into the remote
-     shell command.  --old-args is kept for CLI/ABI compatibility but no longer
-     disables that protection. */
-  (void)old_args;
+     shell command.  (rsync's --old-args no longer disables that protection.) */
   size_t quote_count = 0;
   for (const char* p = path; *p; p++)
     if (*p == '\'')
@@ -296,8 +294,8 @@ void ssh_free_client_argv(char** argv) {
 }
 
 Client* client_connect_ssh(const char* destination, int port, const char* server_path,
-                           bool old_args, const char* rsh_command, bool blocking_io,
-                           char* const* remote_options, int remote_option_count) {
+                           const char* rsh_command, bool blocking_io, char* const* remote_options,
+                           int remote_option_count) {
   RemoteDest r;
   if (parse_remote_dest(destination, &r) != 0) {
     char* escaped = output_escape(destination, false);
@@ -376,7 +374,7 @@ Client* client_connect_ssh(const char* destination, int port, const char* server
       snprintf(ssh_user, ssh_user_len, "%s", r.host);
 
     char* remote_command =
-        ssh_build_remote_command(server_path, old_args, remote_options, remote_option_count);
+        ssh_build_remote_command(server_path, remote_options, remote_option_count);
     if (!remote_command)
       ssh_child_setup_failed(exec_pipe[1]);
     char** ssh_argv = ssh_build_client_argv(rsh_command, port, ssh_user, remote_command);

src/shared/transport_ssh.h

@@ -4,17 +4,17 @@
 #include "transport_tcp.h"
 
 Client* client_connect_ssh(const char* destination, int port, const char* server_path,
-                           bool old_args, const char* rsh_command, bool blocking_io,
-                           char* const* remote_options, int remote_option_count);
+                           const char* rsh_command, bool blocking_io, char* const* remote_options,
+                           int remote_option_count);
 /* Build the escaped remote-shell command string (the server program path always
  * quoted as one remote-shell word, followed by ` --stdio` and each
  * --remote-option value appended as an individually single-quoted shell word).
- * `old_args` is accepted for CLI/ABI compatibility but no longer disables
- * quoting: the path is always escaped so a metacharacter-bearing
- * --rsync-path can never be interpreted by the remote shell.  Every
- * --remote-option value is individually escaped with the '\'' sequence and
- * values with empty/control characters are rejected at the CLI parse layer. */
-char* ssh_build_remote_command(const char* server_path, bool old_args, char* const* remote_options,
+ * The path is always escaped so a metacharacter-bearing --rsync-path can never
+ * be interpreted by the remote shell (the --old-args no-op does not disable
+ * quoting).  Every --remote-option value is individually escaped with the '\''
+ * sequence and values with empty/control characters are rejected at the CLI
+ * parse layer. */
+char* ssh_build_remote_command(const char* server_path, char* const* remote_options,
                                int remote_option_count);
 /* Build the NULL-terminated child argv for the remote-shell client (argv[0] is
  * the exec/execvp program).  rsh_command is whitespace-split into leading argv

src/shared/transport_tcp.c

@@ -134,7 +134,7 @@ Server* server_create_ex(int port, const ServerBindOptions* bind_opts) {
 
   server->file_descriptor = file_descriptor;
   server->ssl_ctx = NULL;
-  server->max_connections = 100;
+  server->max_connections = SERVER_DEFAULT_MAX_CONNECTIONS;
   server->active_connections = 0;
   server->limit_registry = NULL;
 

src/shared/transport_tcp.h

@@ -11,6 +11,10 @@
  * stored here so the transport layer does not depend on daemon config. */
 struct DaemonLimitRegistry;
 
+/* Connection cap applied by server_create_ex() until the daemon's configured
+ * `max connections` overrides it via server_set_max_connections(). */
+#define SERVER_DEFAULT_MAX_CONNECTIONS 100
+
 typedef struct Server {
   struct sockaddr_storage address;
   unsigned int address_length;

src/shared/utils.c

@@ -7,6 +7,7 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <netinet/in.h>
+#include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -48,6 +49,15 @@ const char* utils_get_authorized_root_path(void) {
   return authorized_root_path;
 }
 
+void utils_set_error(char* err, size_t err_size, const char* fmt, ...) {
+  if (!err || err_size == 0)
+    return;
+  va_list args;
+  va_start(args, fmt);
+  vsnprintf(err, err_size, fmt, args);
+  va_end(args);
+}
+
 bool path_is_within_root(const char* root, const char* path) {
   size_t root_len = strlen(root);
   return strncmp(root, path, root_len) == 0 && (path[root_len] == '\0' || path[root_len] == '/');
@@ -615,430 +625,6 @@ bool format_human_bytes(unsigned long long bytes, char* buffer, size_t buffer_si
   return written >= 0 && (size_t)written < buffer_size;
 }
 
-/* Build the keep-set index from the exact manifest entries only.  A lookup of
-   `rel` succeeds iff `rel` is a kept entry, a kept directory, or an ancestor
-   directory of kept content (the old is_dir_in_manifest predicate); the sorted
-   view answers "is an ancestor of kept content" without materializing any
-   per-component prefix copy, so the index is O(manifest size) memory. */
-static bool build_keep_index(const ArrayList* manifest, PathIndex* index) {
-  if (!manifest || manifest->size <= 0)
-    return path_index_build(index, NULL, 0);
-  return path_index_build(index, (const char* const*)manifest->items, (size_t)manifest->size);
-}
-
-static bool keep_is_dir(const PathIndex* index, const char* rel_path) {
-  return path_index_contains(index, rel_path) || path_index_has_descendant(index, rel_path);
-}
-
-static bool keep_is_file(const PathIndex* index, const char* rel_path) {
-  return path_index_contains(index, rel_path);
-}
-
-/* True when child_rel is, or lies below, a protected entry.  A prefix "a"
-   therefore protects "a" and "a/b/c" but not "ab".  Entries with top_level_only
-   set only protect DIRECT children of the receive root (at_root); nested
-   directories that share such a name stay ordinary destination content. */
-bool path_under_skip_prefix(const char* child_rel, bool at_root, const DeleteSkipEntry* skips,
-                            int skip_count) {
-  for (int i = 0; i < skip_count; i++) {
-    if (skips[i].top_level_only && !at_root)
-      continue;
-    size_t prefix_len = strlen(skips[i].prefix);
-    if (strncmp(child_rel, skips[i].prefix, prefix_len) == 0 &&
-        (child_rel[prefix_len] == '\0' || child_rel[prefix_len] == '/'))
-      return true;
-  }
-  return false;
-}
-
-/* Per-run deletion budget and tallies.  `max_delete` is the cap on the number
-   of entries the walker may remove (SIZE_MAX = unlimited); once it is reached
-   the remaining extras are counted in `skipped` and left in place, matching
-   rsync's partial --max-delete behavior. */
-typedef struct {
-  size_t max_delete;
-  size_t deleted;
-  size_t skipped;
-  bool limit_hit;
-} DeleteBudget;
-
-/* True when direct children of the directory named by `rel` may be removed.
-   With no synchronization info (dirs == NULL) the whole tree is deletable; when
-   a dirs index is supplied only its exact entries are (the receive root is the
-   "." sentinel). */
-static bool is_synced_dir(const PathIndex* dirs, const char* rel) {
-  if (!dirs)
-    return true;
-  return path_index_contains(dirs, rel[0] == '\0' ? "." : rel);
-}
-
-/* Remove the extras directly inside the directory open on `dirfd`, recursing
-   into every child directory so kept content below a synchronized prefix is
-   reached.  `all_removed` reports whether every child entry was removed (so the
-   caller may rmdir this directory).  A child directory is never removed when it
-   is itself a synchronized directory or holds kept content; with a dirs index
-   supplied, direct children of a non-synchronized directory are never extras at
-   all (they are left in place but still descended into).  Symlinks are unlinked
-   like any other non-directory extra (never followed). */
-static bool delete_extras_fd(int dirfd, const char* rel_path, const PathIndex* keep,
-                             const PathIndex* dirs, DeleteBudget* budget,
-                             const DeleteSkipEntry* skips, int skip_count,
-                             const FilterRuleList* protect_rules, bool parent_deletable,
-                             bool* all_removed, DeletePathObserver observer,
-                             void* observer_context) {
-  /* openat(dirfd, ".") opens an independent file description: a dup() would
-     share dirfd's file offset and a prior pass could leave the stream drained. */
-  int scanfd = openat(dirfd, ".", O_RDONLY | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
-  if (scanfd < 0)
-    return false;
-  DIR* dir = fdopendir(scanfd);
-  if (!dir) {
-    close(scanfd);
-    return false;
-  }
-  bool operation_ok = true;
-  bool local_survives = false;
-  /* A directory is deletable when it or ANY ancestor is synchronized; the
-     `parent_deletable` flag carries that down the recursion so dest-only
-     directories below a synchronized root are removed wholesale. */
-  bool deletable = parent_deletable || is_synced_dir(dirs, rel_path);
-  const struct dirent* entry;
-  while ((entry = readdir(dir)) != NULL) {
-    if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
-      continue;
-    char* child_rel = path_cat((char*)rel_path, entry->d_name);
-    if (!child_rel) {
-      operation_ok = false;
-      continue;
-    }
-    /* A --delay-updates run keeps its staging directory as a direct child of
-       the receive root, and basis-dir snapshots live below it too.  Their
-       contents are not manifest entries, so descending into them would delete
-       every staged / basis file as an "extra".  Only the staging name (a
-       top-level-only prefix) and the basis prefixes are protected: a nested
-       destination directory that happens to be called .fastsync-stage is
-       ordinary content. */
-    if (path_under_skip_prefix(child_rel, rel_path[0] == '\0', skips, skip_count)) {
-      local_survives = true;
-      free(child_rel);
-      continue;
-    }
-    struct stat st;
-    if (fstatat(dirfd, entry->d_name, &st, AT_SYMLINK_NOFOLLOW) != 0) {
-      if (errno != ENOENT)
-        operation_ok = false;
-      free(child_rel);
-      continue;
-    }
-    bool is_dir = S_ISDIR(st.st_mode);
-    if (protect_rules && filter_rules_apply_side(protect_rules, child_rel, entry->d_name, is_dir,
-                                                 FILTER_SIDE_RECEIVER) == FILTER_ACTION_PROTECT) {
-      /* A first-match protect rule shields the extra; for a directory the whole
-         subtree is shielded (rsync prunes an excluded directory), so do not
-         descend. */
-      local_survives = true;
-      free(child_rel);
-      continue;
-    }
-    if (is_dir) {
-      int childfd = openat(dirfd, entry->d_name, O_RDONLY | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
-      bool child_all_removed = false;
-      if (childfd >= 0) {
-        if (!delete_extras_fd(childfd, child_rel, keep, dirs, budget, skips, skip_count,
-                              protect_rules, deletable, &child_all_removed, observer,
-                              observer_context))
-          operation_ok = false;
-        close(childfd);
-      } else if (errno != ENOENT) {
-        operation_ok = false;
-      }
-      bool child_synced = dirs && path_index_contains(dirs, child_rel);
-      if (child_synced || keep_is_dir(keep, child_rel)) {
-        /* A synchronized directory and a directory holding kept content are
-           never removed. */
-        local_survives = true;
-      } else if (child_all_removed && deletable) {
-        if (budget->deleted >= budget->max_delete) {
-          budget->limit_hit = true;
-          budget->skipped++;
-          local_survives = true;
-        } else if (unlinkat(dirfd, entry->d_name, AT_REMOVEDIR) != 0) {
-          /* ENOENT: already gone (fine).  ENOTEMPTY/EEXIST: the directory
-             still holds entries the walker leaves in place (a protected
-             excluded prefix, a kept file the manifest protects, a symlink);
-             rsync leaves such a directory behind, so this is not an error.
-             Only genuine I/O failures abort the deletion. */
-          if (errno != ENOENT && errno != ENOTEMPTY && errno != EEXIST)
-            operation_ok = false;
-          local_survives = true;
-        } else {
-          budget->deleted++;
-          if (observer)
-            observer(observer_context, child_rel);
-        }
-      } else {
-        local_survives = true;
-      }
-    } else {
-      bool found = keep_is_file(keep, child_rel);
-      if (found || !deletable) {
-        /* Kept file, or a child of a directory that is not synchronized: never
-           an extra for this run. */
-        local_survives = true;
-      } else if (budget->deleted >= budget->max_delete) {
-        budget->limit_hit = true;
-        budget->skipped++;
-        local_survives = true;
-      } else if (unlinkat(dirfd, entry->d_name, 0) != 0) {
-        if (errno != ENOENT)
-          operation_ok = false;
-        local_survives = true;
-      } else {
-        budget->deleted++;
-        if (observer)
-          observer(observer_context, child_rel);
-        char* escaped_path = output_escape(child_rel, log_get_8_bit_output());
-        fprintf(stderr, "  Deleted: %s\n", escaped_path ? escaped_path : "<allocation failed>");
-        free(escaped_path);
-      }
-    }
-    free(child_rel);
-  }
-  closedir(dir);
-  *all_removed = !local_survives;
-  return operation_ok;
-}
-
-/* Read-only mirror of delete_extras_fd: records the paths that WOULD be removed
-   without unlinking anything.  A child directory is reported after its own
-   reportable children (depth-first), matching the delete pass's ordering. */
-static bool list_extras_fd(int dirfd, const char* rel_path, const PathIndex* keep,
-                           const PathIndex* dirs, ArrayList* out, size_t* recorded,
-                           const DeleteSkipEntry* skips, int skip_count,
-                           const FilterRuleList* protect_rules, bool parent_deletable,
-                           bool* all_removed) {
-  int scanfd = openat(dirfd, ".", O_RDONLY | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
-  if (scanfd < 0)
-    return false;
-  DIR* dir = fdopendir(scanfd);
-  if (!dir) {
-    close(scanfd);
-    return false;
-  }
-  bool operation_ok = true;
-  bool local_survives = false;
-  bool deletable = parent_deletable || is_synced_dir(dirs, rel_path);
-  const struct dirent* entry;
-  while ((entry = readdir(dir)) != NULL) {
-    if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
-      continue;
-    char* child_rel = path_cat((char*)rel_path, entry->d_name);
-    if (!child_rel) {
-      operation_ok = false;
-      continue;
-    }
-    if (path_under_skip_prefix(child_rel, rel_path[0] == '\0', skips, skip_count)) {
-      local_survives = true;
-      free(child_rel);
-      continue;
-    }
-    struct stat st;
-    if (fstatat(dirfd, entry->d_name, &st, AT_SYMLINK_NOFOLLOW) != 0) {
-      if (errno != ENOENT)
-        operation_ok = false;
-      free(child_rel);
-      continue;
-    }
-    bool is_dir = S_ISDIR(st.st_mode);
-    if (protect_rules && filter_rules_apply_side(protect_rules, child_rel, entry->d_name, is_dir,
-                                                 FILTER_SIDE_RECEIVER) == FILTER_ACTION_PROTECT) {
-      /* Mirror the delete walk: a protected entry is never reported as a
-         would-delete and a protected directory's subtree is not enumerated. */
-      local_survives = true;
-      free(child_rel);
-      continue;
-    }
-    if (is_dir) {
-      int childfd = openat(dirfd, entry->d_name, O_RDONLY | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
-      bool child_all_removed = false;
-      if (childfd >= 0) {
-        if (!list_extras_fd(childfd, child_rel, keep, dirs, out, recorded, skips, skip_count,
-                            protect_rules, deletable, &child_all_removed))
-          operation_ok = false;
-        close(childfd);
-      } else if (errno != ENOENT) {
-        operation_ok = false;
-      }
-      bool child_synced = dirs && path_index_contains(dirs, child_rel);
-      if (child_synced || keep_is_dir(keep, child_rel)) {
-        local_survives = true;
-      } else if (child_all_removed && deletable) {
-        size_t len = strlen(child_rel);
-        char* copy = malloc(len + 2);
-        if (!copy) {
-          operation_ok = false;
-        } else {
-          memcpy(copy, child_rel, len);
-          copy[len] = '/';
-          copy[len + 1] = '\0';
-          if (!array_list_add(out, copy)) {
-            free(copy);
-            operation_ok = false;
-          } else {
-            (*recorded)++;
-          }
-        }
-      } else {
-        local_survives = true;
-      }
-    } else {
-      bool found = keep_is_file(keep, child_rel);
-      if (found || !deletable) {
-        local_survives = true;
-      } else {
-        char* copy = str_dup(child_rel);
-        if (!copy || !array_list_add(out, copy)) {
-          free(copy);
-          operation_ok = false;
-        } else {
-          (*recorded)++;
-        }
-      }
-    }
-    free(child_rel);
-  }
-  closedir(dir);
-  *all_removed = !local_survives;
-  return operation_ok;
-}
-
-bool delete_extras_list(const char* dest_root, const ArrayList* manifest,
-                        const ArrayList* synced_dirs, const DeleteSkipEntry* skips, int skip_count,
-                        const FilterRuleList* protect_rules, ArrayList* out, size_t* count_out) {
-  if (count_out)
-    *count_out = 0;
-  if (!manifest || !out)
-    return false;
-  PathIndex keep;
-  if (!build_keep_index(manifest, &keep))
-    return false;
-  PathIndex dirs;
-  bool have_dirs = synced_dirs != NULL;
-  if (have_dirs &&
-      !path_index_build(&dirs, (const char* const*)synced_dirs->items, (size_t)synced_dirs->size)) {
-    path_index_free(&keep);
-    return false;
-  }
-  int rootfd;
-  int root_fd = utils_get_authorized_root_fd();
-  if (root_fd >= 0) {
-    if (utils_get_authorized_root_path())
-      rootfd = utils_open_authorized_destination(dest_root);
-    else if (dest_root == NULL)
-      rootfd = dup(root_fd);
-    else
-      rootfd = -1;
-  } else {
-    rootfd = open(dest_root, O_RDONLY | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
-  }
-  if (rootfd < 0) {
-    path_index_free(&keep);
-    if (have_dirs)
-      path_index_free(&dirs);
-    return false;
-  }
-  bool all_removed = false;
-  size_t recorded = 0;
-  bool ok = list_extras_fd(rootfd, "", &keep, have_dirs ? &dirs : NULL, out, &recorded, skips,
-                           skip_count, protect_rules, false, &all_removed);
-  if (close(rootfd) != 0)
-    ok = false;
-  path_index_free(&keep);
-  if (have_dirs)
-    path_index_free(&dirs);
-  if (count_out)
-    *count_out = recorded;
-  return ok;
-}
-
-DeleteWalkResult delete_extras_limited_observed(const char* dest_root, const ArrayList* manifest,
-                                                const ArrayList* synced_dirs, size_t max_delete,
-                                                const DeleteSkipEntry* skips, int skip_count,
-                                                const FilterRuleList* protect_rules,
-                                                size_t* deleted_out, size_t* skipped_out,
-                                                DeletePathObserver observer,
-                                                void* observer_context) {
-  if (deleted_out)
-    *deleted_out = 0;
-  if (skipped_out)
-    *skipped_out = 0;
-  if (!manifest)
-    return DELETE_WALK_ERROR;
-  /* Index the keep-set (and the synchronized-dir set, when supplied) once so
-     membership is answered in O(path length) instead of scanning every entry
-     for every destination entry. */
-  PathIndex keep;
-  if (!build_keep_index(manifest, &keep))
-    return DELETE_WALK_ERROR;
-  PathIndex dirs;
-  bool have_dirs = synced_dirs != NULL;
-  if (have_dirs &&
-      !path_index_build(&dirs, (const char* const*)synced_dirs->items, (size_t)synced_dirs->size)) {
-    path_index_free(&keep);
-    return DELETE_WALK_ERROR;
-  }
-  int rootfd;
-  int root_fd = utils_get_authorized_root_fd();
-  if (root_fd >= 0) {
-    if (utils_get_authorized_root_path())
-      rootfd = utils_open_authorized_destination(dest_root);
-    else if (dest_root == NULL)
-      rootfd = dup(root_fd);
-    else
-      rootfd = -1;
-  } else {
-    rootfd = open(dest_root, O_RDONLY | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
-  }
-  if (rootfd < 0) {
-    path_index_free(&keep);
-    if (have_dirs)
-      path_index_free(&dirs);
-    return DELETE_WALK_ERROR;
-  }
-  DeleteBudget budget = {.max_delete = max_delete, .deleted = 0, .skipped = 0, .limit_hit = false};
-  bool all_removed = false;
-  bool ok =
-      delete_extras_fd(rootfd, "", &keep, have_dirs ? &dirs : NULL, &budget, skips, skip_count,
-                       protect_rules, false, &all_removed, observer, observer_context);
-  if (close(rootfd) != 0)
-    ok = false;
-  path_index_free(&keep);
-  if (have_dirs)
-    path_index_free(&dirs);
-  if (deleted_out)
-    *deleted_out = budget.deleted;
-  if (skipped_out)
-    *skipped_out = budget.skipped;
-  if (!ok)
-    return DELETE_WALK_ERROR;
-  return budget.limit_hit ? DELETE_WALK_LIMIT_REACHED : DELETE_WALK_OK;
-}
-
-DeleteWalkResult delete_extras_limited(const char* dest_root, const ArrayList* manifest,
-                                       const ArrayList* synced_dirs, size_t max_delete,
-                                       const DeleteSkipEntry* skips, int skip_count,
-                                       const FilterRuleList* protect_rules, size_t* deleted_out,
-                                       size_t* skipped_out) {
-  return delete_extras_limited_observed(dest_root, manifest, synced_dirs, max_delete, skips,
-                                        skip_count, protect_rules, deleted_out, skipped_out, NULL,
-                                        NULL);
-}
-
-bool delete_extras(const char* dest_root, const ArrayList* manifest) {
-  return delete_extras_limited(dest_root, manifest, NULL, SIZE_MAX, NULL, 0, NULL, NULL, NULL) ==
-         DELETE_WALK_OK;
-}
-
 bool has_path_traversal(const char* path) {
   if (!path)
     return true;

src/shared/utils.h

@@ -106,79 +106,7 @@ int env_choice_first(const char* env_name, int (*resolve)(const char*), bool* sp
 ssize_t utils_getdelim_bounded(FILE* stream, char** line, size_t* cap, int delim, size_t max_len);
 char* path_cat(const char* path1, const char* path2);
 bool glob_match(const char* pattern, const char* str);
-/* Result of a bounded extra-file deletion run. */
-typedef enum {
-  /* Every extra entry was removed (or there were none). */
-  DELETE_WALK_OK = 0,
-  /* The numeric cap for this run was reached before every extra was removed.
-     The walker removed exactly the entries the cap allowed and skipped (without
-     removing) the rest, matching rsync's partial --max-delete behavior. */
-  DELETE_WALK_LIMIT_REACHED,
-  /* A traversal or unlink failure aborted the deletion (partial removal is
-     possible, mirroring the delete pass). */
-  DELETE_WALK_ERROR
-} DeleteWalkResult;
-/* One protected entry for the delete walker.  When top_level_only is true the
-   prefix is skipped only as a DIRECT child of dest_root (the --delay-updates
-   staging directory, which must not hide genuine extras inside a nested
-   destination directory that happens to share the staging name); otherwise the
-   prefix is skipped at any depth (the --compare-dest/--copy-dest/--link-dest
-   basis trees, and the sender-side protected filter-excluded prefixes, which
-   are never destination content). */
-typedef struct {
-  const char* prefix;
-  bool top_level_only;
-} DeleteSkipEntry;
-/* True when child_rel is, or lies below, one of the protected entries (a prefix
-   "a" protects "a" and "a/b/c" but not "ab"; top_level_only entries protect
-   only DIRECT children of the destination root, i.e. child_rel has no '/'). */
-bool path_under_skip_prefix(const char* child_rel, bool at_root, const DeleteSkipEntry* skips,
-                            int skip_count);
-/* Remove files/dirs/symlinks under dest_root that are not listed in manifest
-   without ever descending into a protected prefix (see DeleteSkipEntry).  When
-   `synced_dirs` is non-NULL, extras are only removed directly inside a directory
-   whose destination-relative path is an exact entry in that list (the receive
-   root is the "." sentinel); directories outside the synchronized set are still
-   descended into so kept content below a listed directory is preserved, but
-   nothing in them is removed.  A NULL `synced_dirs` keeps the legacy behavior of
-   treating the whole destination tree as deletable.  `max_delete` caps the
-   number of removed entries (SIZE_MAX = unlimited): the walker removes up to the
-   cap and returns DELETE_WALK_LIMIT_REACHED when more extras remained.
-   `deleted_out`/`skipped_out` optionally receive the number of entries removed
-   and the number skipped because of the cap. */
-DeleteWalkResult delete_extras_limited(const char* dest_root, const ArrayList* manifest,
-                                       const ArrayList* synced_dirs, size_t max_delete,
-                                       const DeleteSkipEntry* skips, int skip_count,
-                                       const FilterRuleList* protect_rules, size_t* deleted_out,
-                                       size_t* skipped_out);
 
-/* Optional per-deletion observer: called for each destination-relative path
-   actually removed (a file, symlink, or directory), in removal order, so the
-   receiver can stream rsync's `--info=del`/`--info=remove` lines. */
-typedef void (*DeletePathObserver)(void* context, const char* rel_path);
-
-/* `delete_extras_limited_observed` is delete_extras_limited with an optional
- * observer; the observer is invoked only for entries truly removed.  When
- * `protect_rules` is non-NULL its receiver-side verdict is evaluated for every
- * candidate extra: a first-match PROTECT leaves the entry (and, for a
- * directory, its whole subtree) in place, while RISK/NONE fall through to the
- * ordinary skip-prefix/keep-set logic. */
-DeleteWalkResult delete_extras_limited_observed(const char* dest_root, const ArrayList* manifest,
-                                                const ArrayList* synced_dirs, size_t max_delete,
-                                                const DeleteSkipEntry* skips, int skip_count,
-                                                const FilterRuleList* protect_rules,
-                                                size_t* deleted_out, size_t* skipped_out,
-                                                DeletePathObserver observer,
-                                                void* observer_context);
-/* Read-only companion to delete_extras_limited: walk the destination exactly as
-   the delete pass would and APPEND (strdup'd) destination-relative paths that
-   WOULD be removed, without touching disk.  Used for -n/--dry-run --delete
-   would-delete reporting.  Returns true on a clean walk; the caller owns the
-   strings appended to `out` and receives their count in *count_out. */
-bool delete_extras_list(const char* dest_root, const ArrayList* manifest,
-                        const ArrayList* synced_dirs, const DeleteSkipEntry* skips, int skip_count,
-                        const FilterRuleList* protect_rules, ArrayList* out, size_t* count_out);
-bool delete_extras(const char* dest_root, const ArrayList* manifest);
 /* Open the existing destination directory at `dest_root`, confined to the
    authorized root with an O_NOFOLLOW component walk (the same confinement the
    deletion walker uses for its root).  Returns a new fd the caller owns, or -1
@@ -203,6 +131,11 @@ void utils_set_authorized_root_fd(int fd);
  * threads spawn; see utils.c). */
 int utils_get_authorized_root_fd(void);
 const char* utils_get_authorized_root_path(void);
+/* Write a diagnostic message into a caller-supplied buffer, mirroring
+ * vsnprintf.  A NULL `err` or a zero `err_size` is a no-op, so a caller that
+ * only needs the boolean status may safely pass NULL.  Returns nothing; the
+ * buffer is always NUL-terminated by vsnprintf when err_size > 0. */
+void utils_set_error(char* err, size_t err_size, const char* fmt, ...);
 /* True when `path` is `root` itself or lies directly beneath it: a lexical
  * prefix test requiring the byte after `root` to be '\0' or '/'.  Both `root`
  * and `path` must be absolute canonical paths free of "."/".." components (the

src/shared/xattr.c

@@ -7,6 +7,7 @@
 #include "utils.h"
 #include "file_types.h"
 #include <errno.h>
+#include <limits.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -133,16 +134,23 @@ static bool xattr_name_is_posix_acl(const char* name) {
 
 /* ---- SENDER: capture ---- */
 
-FileXattrList* xattr_capture_path(const char* path, bool preserve_acls) {
+/* The two syscall families differ only in whether the FINAL component is
+ * followed (`listxattr`/`getxattr` follow; `llistxattr`/`lgetxattr` do not), so
+ * one common implementation backs both public entry points. */
+typedef ssize_t (*XattrListFn)(const char* path, char* list, size_t size);
+typedef ssize_t (*XattrGetFn)(const char* path, const char* name, void* value, size_t size);
+
+static FileXattrList* xattr_capture_common(const char* path, bool preserve_acls,
+                                           XattrListFn list_fn, XattrGetFn get_fn) {
   if (!path)
     return NULL;
-  ssize_t list_size = listxattr(path, NULL, 0);
+  ssize_t list_size = list_fn(path, NULL, 0);
   if (list_size <= 0)
     return NULL; /* no xattrs, ENOTSUP, or error: nothing appliable */
   char* names = malloc((size_t)list_size);
   if (!names)
     return NULL;
-  ssize_t got = listxattr(path, names, (size_t)list_size);
+  ssize_t got = list_fn(path, names, (size_t)list_size);
   if (got < 0) {
     free(names);
     return NULL;
@@ -165,7 +173,7 @@ FileXattrList* xattr_capture_path(const char* path, bool preserve_acls) {
        negotiated.  Without it a plain -X capture never carries an ACL. */
     if (!xattr_name_appliable(name, preserve_acls))
       continue;
-    ssize_t value_size = getxattr(path, name, NULL, 0);
+    ssize_t value_size = get_fn(path, name, NULL, 0);
     if (value_size < 0)
       continue;
     if (value_size > XATTR_VALUE_MAX)
@@ -178,7 +186,7 @@ FileXattrList* xattr_capture_path(const char* path, bool preserve_acls) {
       free(names);
       return NULL;
     }
-    ssize_t read_len = getxattr(path, name, buffer, (size_t)value_size);
+    ssize_t read_len = get_fn(path, name, buffer, (size_t)value_size);
     if (read_len < 0 || read_len != value_size) {
       free(buffer);
       continue;
@@ -200,6 +208,14 @@ FileXattrList* xattr_capture_path(const char* path, bool preserve_acls) {
   return list;
 }
 
+FileXattrList* xattr_capture_path(const char* path, bool preserve_acls) {
+  return xattr_capture_common(path, preserve_acls, listxattr, getxattr);
+}
+
+FileXattrList* xattr_capture_path_nofollow(const char* path, bool preserve_acls) {
+  return xattr_capture_common(path, preserve_acls, llistxattr, lgetxattr);
+}
+
 /* ---- WIRE ---- */
 
 bool xattr_send(int fd, const FileXattrList* list) {
@@ -363,29 +379,140 @@ bool xattr_apply_fd(int fd, const FileXattrList* list) {
   return true;
 }
 
-/* ---- --fake-super: park ownership/mode/mtime in a reserved xattr ---- */
+/* Symlink counterpart of xattr_apply_fd(): target the link ITSELF, never its
+ * referent.  fsetxattr cannot be used (no *at xattr syscall exists, and the
+ * kernel rejects xattr syscalls on an O_PATH descriptor), so the already-open,
+ * confinement-checked parent directory is addressed through /proc/self/fd and
+ * the final component is applied with lsetxattr, which does not follow it.
+ *
+ * The list is trusted to come from xattr_receive() (already whitelisted), but
+ * every name is re-validated here so this path-based primitive is confined on
+ * its own -- this is the only apply primitive that addresses a path, and the
+ * header promises a whitelisted apply.  The apply is best-effort: if /proc is
+ * not mounted (the anchor cannot be formed) or the kernel refuses the set, the
+ * failure is skipped and never fails the transfer.  See xattr.h for the bounded
+ * residual TOCTOU between link creation and lsetxattr. */
+bool xattr_apply_path_nofollow(int parent_fd, const char* leaf, const FileXattrList* list,
+                               bool preserve_acls) {
+  if (parent_fd < 0 || !leaf || leaf[0] == '\0' || strchr(leaf, '/') != NULL || !list)
+    return false;
+  if (list->count == 0)
+    return true;
+  char prefix[64];
+  int prefix_len = snprintf(prefix, sizeof(prefix), "/proc/self/fd/%d/", parent_fd);
+  if (prefix_len < 0 || (size_t)prefix_len >= sizeof(prefix))
+    return false;
+  size_t leaf_len = strlen(leaf);
+  char* path = malloc((size_t)prefix_len + leaf_len + 1);
+  if (!path)
+    return false;
+  memcpy(path, prefix, (size_t)prefix_len);
+  memcpy(path + prefix_len, leaf, leaf_len + 1);
+  bool warned = false;
+  int first_errno = 0;
+  for (int i = 0; i < list->count; i++) {
+    const FileXattr* xa = &list->items[i];
+    /* Defense in depth: re-validate against the receiver's full whitelist, so a
+       hand-crafted list can never apply a privileged namespace or the reserved
+       --fake-super key through this path-based primitive. */
+    if (!xattr_name_appliable(xa->name, preserve_acls))
+      continue;
+    if (lsetxattr(path, xa->name, xa->value, xa->value_len, 0) != 0) {
+      if (!warned) {
+        warned = true;
+        first_errno = errno;
+      }
+    }
+  }
+  if (warned)
+    log_message(LOG_LEVEL_WARNING,
+                "could not set one or more xattrs on the destination symlink: %s",
+                strerror(first_errno));
+  free(path);
+  return true;
+}
 
-void fake_super_store_fd(int fd, uint32_t uid, uint32_t gid, uint32_t mode, int64_t mtime_sec,
-                         int64_t mtime_nsec) {
+/* ---- --fake-super: park ownership/mode/rdev in a reserved xattr ---- */
+
+void fake_super_store_fd(int fd, uint32_t uid, uint32_t gid, uint32_t mode, uint32_t rdev_major,
+                         uint32_t rdev_minor) {
   if (fd < 0)
     return;
-  char record[128];
-  int len =
-      snprintf(record, sizeof(record), "%lu:%lu:%03o:%lld:%ld", (unsigned long)uid,
-               (unsigned long)gid, (unsigned)mode & 0777U, (long long)mtime_sec, (long)mtime_nsec);
+  /* rsync 3.4.1's exact grammar: "<octal full st_mode> <rdev_major>,<rdev_minor>
+   * <uid>:<gid>".  The octal mode carries the S_IFMT bits (e.g. 0104711 for a
+   * setuid regular file, 020644 for a char device); the rdev pair is 0,0 for a
+   * non-device.  No mtime field: rsync leaves the file's own timestamp in
+   * charge of mtime.  This value is what rsync reads back to restore a
+   * fake-super tree, so the field order and separators must not change. */
+  char record[96];
+  int len = snprintf(record, sizeof(record), "%o %u,%u %u:%u", (unsigned)mode, (unsigned)rdev_major,
+                     (unsigned)rdev_minor, (unsigned)uid, (unsigned)gid);
   if (len <= 0 || (size_t)len >= sizeof(record))
     return;
   if (fsetxattr(fd, FAKESUPER_XATTR, record, (size_t)len, 0) != 0) {
-    log_message(LOG_LEVEL_WARNING, "--fake-super: could not store %s on destination file: %s",
+    log_message(LOG_LEVEL_WARNING, "--fake-super: could not store %s on destination entry: %s",
                 FAKESUPER_XATTR, strerror(errno));
   }
 }
 
-/* --fake-super replay: read the freshly-stored record and re-apply mode/mtime
- * fd-relative.  The recorded uid/gid are retained for a later privileged
- * restore but are NEVER chowned here: --fake-super only RECORDS ownership, it
- * must not real-chown the recorded (resolved) owner.  Mode/mtime still apply so
- * unprivileged --fake-super keeps working. */
+/* Parse rsync's `user.rsync.%stat` grammar strictly:
+ *   "<octal st_mode> <rdev_major>,<rdev_minor> <uid>:<gid>"
+ * Every field is parsed with strtoul() so an out-of-range value is a clean
+ * rejection rather than the undefined behavior sscanf("%u") exhibited, each
+ * field is range-checked against the same bounds the wire validator uses, and
+ * the whole record must be consumed (only trailing whitespace is tolerated) so
+ * trailing garbage is refused.  Returns false on any malformed input. */
+static bool fake_super_parse_stat(const char* record, unsigned* mode_out, unsigned* rdev_major_out,
+                                  unsigned* rdev_minor_out, unsigned* uid_out, unsigned* gid_out) {
+  if (!record)
+    return false;
+  char* end = NULL;
+  const char* p = record;
+  errno = 0;
+  unsigned long mode = strtoul(p, &end, 8);
+  if (errno != 0 || end == p || mode > (unsigned long)UINT_MAX || *end != ' ')
+    return false;
+  p = end + 1;
+  errno = 0;
+  unsigned long rdev_major = strtoul(p, &end, 10);
+  if (errno != 0 || end == p || rdev_major > 0xffffUL || *end != ',')
+    return false;
+  p = end + 1;
+  errno = 0;
+  unsigned long rdev_minor = strtoul(p, &end, 10);
+  if (errno != 0 || end == p || rdev_minor > 0x00ffffffUL || *end != ' ')
+    return false;
+  p = end + 1;
+  errno = 0;
+  unsigned long uid = strtoul(p, &end, 10);
+  if (errno != 0 || end == p || uid > (unsigned long)UINT_MAX || *end != ':')
+    return false;
+  p = end + 1;
+  errno = 0;
+  unsigned long gid = strtoul(p, &end, 10);
+  if (errno != 0 || end == p || gid > (unsigned long)UINT_MAX)
+    return false;
+  p = end;
+  while (*p == ' ' || *p == '\t' || *p == '\n' || *p == '\r')
+    p++;
+  if (*p != '\0')
+    return false;
+  *mode_out = (unsigned)mode;
+  *rdev_major_out = (unsigned)rdev_major;
+  *rdev_minor_out = (unsigned)rdev_minor;
+  *uid_out = (unsigned)uid;
+  *gid_out = (unsigned)gid;
+  return true;
+}
+
+/* --fake-super replay: read the freshly-stored record and re-apply its
+ * permission bits fd-relative.  The recorded uid/gid are retained for a later
+ * privileged restore but are NEVER chowned here: --fake-super only RECORDS
+ * ownership, it must not real-chown the recorded (resolved) owner.  The
+ * recorded rdev is likewise parsed for grammar compatibility but is not acted
+ * on (device recreation is a separate, privilege-gated path).  mtime is not in
+ * the record: the normal metadata path applies it (policy.times), exactly as
+ * rsync relies on the file's own timestamp. */
 bool fake_super_restore_fd(int fd, FileAttrPolicy policy) {
   if (fd < 0)
     return false;
@@ -394,24 +521,25 @@ bool fake_super_restore_fd(int fd, FileAttrPolicy policy) {
   if (len < 0)
     return false; /* absent or filesystem without xattrs: silent no-op */
   record[len] = '\0';
-  unsigned long ul_uid, ul_gid, ul_mode;
-  long long mtime_sec;
-  long mtime_nsec;
-  if (sscanf(record, "%lu:%lu:%lo:%lld:%ld", &ul_uid, &ul_gid, &ul_mode, &mtime_sec, &mtime_nsec) !=
-      5)
+  unsigned ul_mode, rdev_major, rdev_minor, ul_uid, ul_gid;
+  if (!fake_super_parse_stat(record, &ul_mode, &rdev_major, &rdev_minor, &ul_uid, &ul_gid))
     return false; /* malformed record: skip, never fatal */
 
-  /* --fake-super NEVER performs a real chown: that would defeat the whole
-     point of the flag (record privileged ownership on an unprivileged receiver
-     for a later privileged restore).  The uid/gid parsed above are retained in
-     the record for that later restore, but no ownership change happens here. */
+  /* --fake-super NEVER performs a real chown: that would defeat the whole point
+     of the flag (record privileged ownership on an unprivileged receiver for a
+     later privileged restore).  The uid/gid parsed above are retained in the
+     record for that later restore, but no ownership change happens here.  The
+     rdev is retained for the same reason. */
+  (void)rdev_major;
+  (void)rdev_minor;
   (void)ul_uid;
   (void)ul_gid;
   /* Mode is applied only when the per-attribute policy asks for it, through the
-     SAME shared helper the normal metadata path uses (metadata_mode_for_policy):
-     under --perms the recorded source mode is copied exactly, including
-     group/other write and setuid/setgid/sticky bits (rsync parity), and the -E
-     rule derives exec bits from the destination's read bits exactly like
+     SAME shared helper the normal metadata path uses (metadata_mode_for_policy).
+     The recorded special bits are stripped first: rsync's fake-super receiver
+     stores the full mode in the xattr but never installs setuid/setgid/sticky on
+     the real file, so only the 0777 permission bits may be replayed.  The -E
+     rule then derives exec bits from the destination's read bits exactly like
      file_restore_metadata_fd. */
   if (policy.perms || policy.executability) {
     struct stat cur;
@@ -419,19 +547,12 @@ bool fake_super_restore_fd(int fd, FileAttrPolicy policy) {
     if (fstat(fd, &cur) != 0) {
       log_message(LOG_LEVEL_WARNING, "--fake-super: could not read destination mode: %s",
                   strerror(errno));
-    } else if (metadata_mode_for_policy((mode_t)ul_mode, cur.st_mode, policy, &want)) {
+    } else if (metadata_mode_for_policy((mode_t)(ul_mode & 0777U), cur.st_mode, policy, &want)) {
       if (fchmod(fd, want) != 0)
         log_message(LOG_LEVEL_WARNING,
-                    "--fake-super: could not restore mode on destination file: %s",
+                    "--fake-super: could not restore mode on destination entry: %s",
                     strerror(errno));
     }
   }
-  if (policy.times) {
-    struct timespec times[2] = {{.tv_sec = 0, .tv_nsec = UTIME_OMIT},
-                                {.tv_sec = (time_t)mtime_sec, .tv_nsec = mtime_nsec}};
-    if (futimens(fd, times) != 0)
-      log_message(LOG_LEVEL_WARNING,
-                  "--fake-super: could not restore mtime on destination file: %s", strerror(errno));
-  }
   return true;
 }

src/shared/xattr.h

@@ -26,16 +26,22 @@
  *     and total bytes) on BOTH ends to prevent OOM/memory abuse; an oversized
  *     or malformed frame is a clean protocol rejection, never an allocation
  *     blowup.
- *   * Application is confined to the exact destination file descriptor
- *     (fsetxattr on the just-written fd), never a caller-controlled path.
+ *   * Application is confined to the exact destination entry: fsetxattr on the
+ *     just-written fd for regular files/directories, and for a symlink an
+ *     lsetxattr on "/proc/self/fd/<parent_fd>/<leaf>" reached through the
+ *     already-opened, confinement-checked parent directory -- never a
+ *     caller-controlled path, and never following the link.
  */
 
 /* Reserved key used by --fake-super to park the source's privileged ownership
- * / mode / mtime on the destination file as an unprivileged user.* xattr, so a
- * later privileged restore could re-apply them.  Exact documented format:
- *   uid:gid:mode:mtime_sec:mtime_nsec           (decimal, decimal, octal, dec, dec)
- * e.g. "1000:1000:644:1765238400:0". */
-#define FAKESUPER_XATTR "user.fastsync.stat"
+ * / mode / rdev on the destination file as an unprivileged user.* xattr, so the
+ * tree is interoperable with rsync 3.4.1 and a later privileged restore can
+ * re-apply them.  This is rsync's own key and value grammar exactly:
+ *   <octal st_mode with S_IFMT> <rdev_major>,<rdev_minor> <uid>:<gid>
+ * e.g. "104711 0,0 1234:5678" for a setuid regular file owned by 1234:5678,
+ * or "20644 1,3 111:222" for a char device.  mtime is deliberately NOT part of
+ * the record: exactly like rsync, the file's own timestamp carries it. */
+#define FAKESUPER_XATTR "user.rsync.%stat"
 
 /* --- bounds --- */
 #define XATTR_NAME_MAX 255                /* xattr names are limited to 255 bytes */
@@ -76,6 +82,17 @@ bool xattr_name_appliable(const char* name, bool preserve_acls);
  * distinct from NULL. */
 FileXattrList* xattr_capture_path(const char* path, bool preserve_acls);
 
+/* Sender: like xattr_capture_path() but reads the xattrs of `path` ITSELF,
+ * never following a final symlink (llistxattr/lgetxattr).  A symlink entry must
+ * use this so the scanner never captures the REFERENT's attributes onto the
+ * link (the path-following variant would).  On Linux the VFS refuses to
+ * associate xattrs with symlinks at all, so this normally returns NULL; it is
+ * still correct and portable for a filesystem/platform that supports them.
+ * The same whitelist/bounds as xattr_capture_path() apply.  Returns NULL when
+ * the link has no appliable xattrs (or the filesystem does not support them);
+ * an empty-but-valid list is never returned distinct from NULL. */
+FileXattrList* xattr_capture_path_nofollow(const char* path, bool preserve_acls);
+
 /* Wire: bounded serialization.  xattr_send returns false on write failure; an
  * empty/NULL list transmits a zero-count block.  xattr_receive returns NULL and
  * sets *ok = 0 on any malformed / oversized / non-whitelisted entry.  When
@@ -91,24 +108,61 @@ FileXattrList* xattr_receive(int fd, int* ok, bool preserve_acls);
  * true when apply was attempted (allowing callers to treat it as best-effort). */
 bool xattr_apply_fd(int fd, const FileXattrList* list);
 
-/* --fake-super: write the source uid/gid/mode/mtime record into the reserved
- * FAKESUPER_XATTR on `fd`.  Best-effort (logged, never fatal).  Only meaningful
- * when metadata was transmitted so the values exist. */
-void fake_super_store_fd(int fd, uint32_t uid, uint32_t gid, uint32_t mode, int64_t mtime_sec,
-                         int64_t mtime_nsec);
+/* Receiver: apply every entry to the symlink named by (parent_fd, leaf) WITHOUT
+ * following it, via lsetxattr() on the confined path
+ * "/proc/self/fd/<parent_fd>/<leaf>".  Every incoming name is independently
+ * re-validated against xattr_name_appliable() with `preserve_acls`, exactly like
+ * xattr_apply_fd(): a non-whitelisted namespace (including the reserved
+ * --fake-super key) is skipped, so this primitive stays confined even if handed
+ * a hand-crafted list.  A symlink cannot be targeted by the fd-relative
+ * fsetxattr() path: there is no *at() xattr syscall and the kernel rejects
+ * xattr syscalls on an O_PATH descriptor, so the already-opened,
+ * confinement-checked parent directory is the anchor and only the final
+ * component is the (no-follow) link.  `leaf` must be a single path component.
+ *
+ * Portability: the "/proc/self/fd/<parent_fd>" anchor requires a mounted /proc.
+ * Where /proc is unavailable (or the fd cannot be addressed that way) the
+ * lsetxattr simply fails and is skipped -- the apply is best-effort exactly like
+ * xattr_apply_fd(), so no error is propagated and the transfer continues.  A
+ * per-attribute failure (on Linux every set on a symlink fails with EPERM) is
+ * logged once and skipped, never fatal.  Returns false only for an invalid
+ * anchor/list; true when an apply was attempted.
+ *
+ * Residual TOCTOU: `leaf` is a caller-supplied name resolved by path in the
+ * parent, so a local writer could replace the just-created symlink between its
+ * creation and lsetxattr().  This is bounded: it requires write access to the
+ * confinement-checked destination directory (already trusted), can only install
+ * a whitelisted user namespace or POSIX-ACL name, and never follows the link (a
+ * replacement symlink is still applied to as the final, no-follow component). */
+bool xattr_apply_path_nofollow(int parent_fd, const char* leaf, const FileXattrList* list,
+                               bool preserve_acls);
+
+/* --fake-super: write the source uid/gid/mode/rdev record into the reserved
+ * FAKESUPER_XATTR on `fd`, using rsync 3.4.1's exact grammar (see the key
+ * comment above).  `mode` is the full st_mode including its S_IFMT bits.
+ * `fd` may be a regular file, a faked char/block device (written as a regular
+ * file), or a DIRECTORY: rsync stores a directory's faked mode/uid/gid in the
+ * reserved xattr on the directory itself.  Best-effort (logged, never fatal).
+ * Only meaningful when metadata was transmitted so the values exist. */
+void fake_super_store_fd(int fd, uint32_t uid, uint32_t gid, uint32_t mode, uint32_t rdev_major,
+                         uint32_t rdev_minor);
 
 /* --fake-super replay: parse the FAKESUPER_XATTR record previously written on
- * `fd` by fake_super_store_fd and re-apply mode/mtime fd-relative.  The
- * recorded uid/gid are deliberately NOT chowned for real: --fake-super only
- * RECORDS ownership (the caller stores the resolved mapping via
- * identity_resolve_storage_ids), it never performs a real chown.  Best-effort:
- * absence of the xattr or a malformed record is a silent no-op that never fails
- * the transfer.  The MODE leg is applied only when policy.perms||policy.
- * executability and the MTIME leg only when policy.times, so the fake-super
- * replay cannot bypass the per-attribute split; the mode follows the normal
- * metadata path exactly (under --perms the source mode is copied verbatim,
- * special and group/other write bits included).
- * Returns true when the xattr was present and parsed. */
+ * `fd` by fake_super_store_fd and re-apply the recorded permission bits
+ * fd-relative.  `fd` may be a regular file, a faked device, or a DIRECTORY;
+ * fgetxattr/fchmod work identically on a directory descriptor.  The recorded
+ * uid/gid are deliberately NOT chowned for real: --fake-super only RECORDS
+ * ownership (the caller stores the resolved mapping via
+ * identity_resolve_storage_ids), it never performs a real chown.  The
+ * recorded rdev is retained for a later privileged restore but is not acted on
+ * here.  Best-effort: absence of the xattr or a malformed record is a silent
+ * no-op that never fails the transfer.  The MODE leg is applied only when
+ * policy.perms||policy.executability, and the recorded special bits
+ * (setuid/setgid/sticky) are NOT applied to the real entry -- exactly like
+ * rsync's fake-super receiver, which stores the full mode in the xattr but
+ * strips the special bits on disk.  mtime is not part of the record; the normal
+ * metadata path carries it (policy.times) exactly as rsync sets the file's own
+ * timestamp.  Returns true when the xattr was present and parsed. */
 bool fake_super_restore_fd(int fd, FileAttrPolicy policy);
 
 #endif

test_data-manual/dst/f.bin

@@ -1 +0,0 @@
-OLDDEST

test_data-manual/dst/test_data-manual/src/f.bin

@@ -1 +0,0 @@
-NEWCONTENT

test_data-manual/src/f.bin

@@ -1 +0,0 @@
-NEWCONTENT

test_probe/dst/workspace/test_probe/src/a.txt

@@ -0,0 +1 @@
+hello

test_probe/dst/workspace/test_probe/src/extra.txt

@@ -0,0 +1 @@
+x

test_probe/dst/workspace/test_probe/src/extradir/in.txt

@@ -0,0 +1 @@
+y

test_probe/dst/workspace/test_probe/src/extralink

@@ -0,0 +1 @@
+a.txt

test_probe/dst/workspace/test_probe/src/link

@@ -0,0 +1 @@
+b.txt

test_probe/dst/workspace/test_probe/src/sub/b.txt

@@ -0,0 +1 @@
+world

test_probe/dst/workspace/test_probe/src/sub/deep/d.txt

@@ -0,0 +1 @@
+deep

test_probe/dst/workspace/test_probe/src/sub/rel

@@ -0,0 +1 @@
+../a.txt