Merge pull request 'Remove unimplemented CLI options' (#209) from feat/remove-unimplemented-cli-options into evaluation-of-codebase-by-human

Reviewed-on: #209

AGENTS.md

@@ -60,48 +60,6 @@ python3 -m pytest tests/     # integration tests
 
 When running the CI workflow via `tea` (the task execution agent), always set a sufficient timeout (e.g., 600000ms) to allow CI to finish. After CI completes, check the results yourself — do not assume success. Use `gh run watch` or similar to monitor CI status, then inspect logs on failure.
 
-## Branch Strategy
-
-Never push directly to `main`. All changes must be developed on a feature branch and merged via a pull request. Always create a new branch before making changes:
-```bash
-git checkout -b <feature-branch-name>
-```
-After committing changes, push the branch and create a PR:
-```bash
-git push -u origin <feature-branch-name>
-gh pr create --fill
-```
-Wait for CI to pass on the PR before merging.
-
-## Batch PR Workflow
-
-When handling multiple issues split across several PRs that target the same files:
-
-1. **Group issues by logical category** into separate PR branches (e.g., memory-safety, refactoring, test-coverage).
-2. **Fix and push** each branch independently. Let CI run on each PR.
-3. **Run all 3 reviewer types** on each PR and post results to Gitea via `tea pr approve/reject` or the Gitea API:
-   - `reviewer` — general code correctness
-   - `code-quality-guardian` — code quality, duplication, complexity
-   - `security-auditor` — vulnerability assessment
-4. **Iterate**: if any reviewer requests changes, fix, push, re-review. Repeat until all 3 approve.
-5. **Merge approved PRs** one at a time into `main`.
-6. **Create a combined merge branch** for the remaining PRs that conflict with the new `main`:
-   ```bash
-   git checkout -b merge-all origin/main
-   for branch in branch1 branch2 branch3; do
-     git merge origin/$branch --no-edit || true
-     # Resolve conflicts, build, test
-   done
-   ```
-7. **Run review again** on the combined branch. Fix issues, push, re-review until approved.
-8. **Merge** the combined PR, **close** the redundant individual PRs, and **close all resolved issues** via the Gitea API:
-   ```bash
-   curl -s -X PATCH -H "Authorization: token $TOKEN" \
-     -H "Content-Type: application/json" \
-     -d '{"state":"closed"}' \
-     "https://gitea.tap-tap.win/api/v1/repos/owner/repo/issues/<number>"
-   ```
-
 ## CI Troubleshooting
 
 ### If lint (clang-format) fails
@@ -124,6 +82,99 @@ Run locally before pushing:
 python3 -m pytest tests/ -v --tb=short
 ```
 
+## Branch Strategy
+
+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
+- **`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
+
+```bash
+# Start a new feature
+git checkout dev && git pull
+git checkout -b feat/my-feature
+# ... work, commit, push
+git push -u origin feat/my-feature
+# Create PR targeting dev
+```
+
+### Creating the `dev` branch (one-time setup)
+```bash
+git checkout main && git pull
+git checkout -b dev
+git push origin dev
+# Then in Gitea: Settings → Repository → Default Branch → dev
+```
+
+### Branch protection (Gitea repo settings)
+**For `dev`:**
+- ✅ Require PR for merging
+- ✅ Require 1 approval
+- ✅ Require status checks (all CI jobs must pass)
+- ✅ Delete branch after merge
+
+**For `main`:**
+- ✅ Require PR from `dev` only
+- ✅ Require CI
+- ✅ Require 2 approvals
+- ✅ No direct pushes
+
+## Automated Agent Workflows
+
+All agents run locally via the opencode CLI. There is no CI-based agent automation — agents are invoked on-demand by the developer or by this assistant.
+
+### One-command batch workflow
+
+For fixing a set of issues and creating one integration PR:
+
+```bash
+# 1. Run each subagent on its category
+opencode run --agent security-auditor "Fix all open security issues"
+opencode run --agent debugger "Fix all open bugs"
+opencode run --agent test-writer "Add missing test coverage"
+
+# 2. The assistant handles: merging branches, fixing CI failures,
+#    pushing, creating the integration PR, waiting for CI, iterating.
+#    The developer only reviews the final PR.
+```
+
+### Issue triage loop
+When you want to fix a batch of issues autonomously:
+
+1. Tell the assistant: *"Fix all open issues and create one big PR"*
+2. The assistant delegates to subagents in parallel
+3. Merges their branches, handles CI failures iteratively
+4. Pushes and opens the final PR
+5. You review the PR once CI passes — no intermediate check-ins
+
+### Scheduling
+For periodic maintenance (security audits, code quality scans), run:
+
+```bash
+opencode run --agent security-auditor "Audit the codebase for vulnerabilities"
+opencode run --agent code-quality-guardian "Scan for code quality issues"
+```
+
+This can be cron'd locally if desired (e.g., `crontab -e` with `opencode run`).
+
+## Is opencode a good option?
+
+**Yes, for FastSync's needs.** The hybrid model works well:
+- opencode's 17 specialized agents handle deep code analysis, fixes, tests, and reviews
+- The assistant orchestrates subagents, merges branches, and iterates on CI
+- You only review the final output
+
+The key limitation: opencode is session-based, not a persistent daemon. But for the "fix all issues, one PR" workflow, this is fine — the assistant runs the full pipeline in one shot. Persistent webhook-driven automation isn't available for Gitea, but the one-shot batch approach is simpler and gives you full control over what gets merged.
+
+### Recommendations for this project
+- **Do** use the batch pattern: delegate to subagents, let the assistant merge + iterate CI, review once
+- **Don't** try to run opencode in Gitea Actions — the CI container doesn't have your LLM keys or the interactive context agents need
+- **If** you want fully hands-off periodic scans, set up a local cron job or systemd timer that runs `opencode run` and posts results to Gitea via API
+
 ## Gitea API & tea CLI
 
 ### Check CI status via API
@@ -155,7 +206,7 @@ tea pr close <number> --repo TapTap/FastSync
 
 ## Common pitfalls
 
-- **`__thread` on shared SSL context**: io_ssl must NOT be thread-local — worker threads inherit the SSL context from the main thread. Use regular `static SSL* io_ssl`.
+- **Per-thread SSL context**: `io_ssl` is stored per-thread (`static __thread SSL* io_ssl`). Each thread that performs protocol I/O must call `io_set_ssl()` to install its own SSL object before using `send_*` / `receive_*` primitives. The main thread's SSL context is not automatically inherited by worker threads.
 - **SSL WANT_READ/WANT_WRITE retry**: Always retry on `SSL_ERROR_WANT_READ` and `SSL_ERROR_WANT_WRITE` in `send_n_data`/`receive_n_data`. Removing these breaks TLS multithreaded transfers.
 - **clang-format version**: The CI image uses clang-format 18. Always format inside the CI Docker container for exact match.
 - **Merge order matters**: Merge the most comprehensive branch first, then smaller ones, to minimize conflicts when creating a combined branch.

CMakeLists.txt

@@ -79,8 +79,9 @@ set(TEST_INCLUDES tests src/shared src/server src/client)
 
 # Monolithic test binary (backward compatible)
 file(GLOB TEST_SRCS "tests/test_*.c" "tests/runner.c")
-add_executable(tests ${TEST_SRCS} ${SHARED_SRCS} src/client/scanner.c)
+add_executable(tests ${TEST_SRCS} ${SHARED_SRCS} src/client/scanner.c src/client/client_cli.c)
 target_include_directories(tests PRIVATE ${TEST_INCLUDES})
+target_compile_definitions(tests PRIVATE FASTSYNC_TEST_BUILD)
 target_link_libraries(tests PRIVATE ${TEST_LIBS})
 add_test(NAME unit_all COMMAND tests)
 

README.md

@@ -40,12 +40,10 @@ A high-performance file synchronization system with SSH and TCP transport, TLS e
 - Optional progress display with throughput
 - Bandwidth limiting via token-bucket algorithm
 - Configurable I/O and connection timeouts (`--timeout`, `--contimeout`)
-- Quiet mode (`-q`/`--quiet`) suppresses all non-error output
 - Backup overwritten files (`--backup`) with optional directory (`--backup-dir`)
 - Transfer statistics summary (`--stats`)
 - Maximum directory depth control (`--max-depth`)
 - Log file output (`--log-file`)
-- Configurable multithreaded queue size (`--queue-size`)
 - Exclude patterns from file (`--exclude-from`)
 
 ### Server
@@ -114,8 +112,6 @@ Abort (`STATUS_ABORT`) may be sent at any point. On receipt the server cleans up
 | `-n, --dry-run` | Scan and print what would be transferred |
 | `-p <port>` | SSH port (default: 22) |
 | `-v, --verbose` | Enable debug logging |
-| `-q, --quiet` | Suppress all non-error output |
-| `--silent` | Alias for `--quiet` |
 | `--progress` | Show real-time transfer speed |
 | `--delete` | Delete files on receiver not present in source |
 | `--exclude <pattern>` | Exclude files matching glob pattern (repeatable) |
@@ -133,7 +129,6 @@ Abort (`STATUS_ABORT`) may be sent at any point. On receipt the server cleans up
 | `--stats` | Print transfer statistics at end (bytes, files, timing) |
 | `--max-depth <n>` | Maximum directory depth to recurse (0 = unlimited, default: 0) |
 | `--log-file <path>` | Write log messages to file instead of stderr |
-| `--queue-size <n>` | Queue capacity for multithreaded mode (default: 100) |
 | `--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 |
@@ -177,7 +172,7 @@ Abort (`STATUS_ABORT`) may be sent at any point. On receipt the server cleans up
 1. **Chunk** — collection of files (~10 MB total by default)
 2. **File** — path, content (`Data`), optional `FileMetadata` pointer
 3. **FileMetadata** — `mode`, `uid`, `gid`, `mtime_sec`, `mtime_nsec`
-4. **Config** — runtime parameters (transported over wire, TLS settings excluded). Includes `timeout`, `contimeout`, `quiet`, `backup`, `backup_dir`, `stats`, `max_depth`, `log_file`, `queue_size`.
+4. **Config** — runtime parameters (transported over wire, TLS settings excluded). Includes `timeout`, `contimeout`, `backup`, `backup_dir`, `stats`, and `max_depth`.
 5. **Queue** — thread-safe bounded queue with condition variables
 6. **DirectoryScanner** — recursive BFS traversal with exclude and include pattern support, max-depth enforcement
 
@@ -294,8 +289,8 @@ Place the `fastsync-server` binary in the remote `$PATH`. The client runs `ssh u
 # Bandwidth limit to 1 MB/s
 ./build/client --bwlimit 1024 /src user@host:/dst
 
-# With timeouts, quiet mode, and stats
-./build/client --timeout 60 --contimeout 15 --quiet --stats /src user@host:/dst
+# With timeouts and stats
+./build/client --timeout 60 --contimeout 15 --stats /src user@host:/dst
 
 # Backup overwritten files to a directory
 ./build/client --backup --backup-dir /backups /src user@host:/dst
@@ -303,9 +298,6 @@ Place the `fastsync-server` binary in the remote `$PATH`. The client runs `ssh u
 # Exclude patterns from file, limit depth
 ./build/client --exclude-from ignore.txt --max-depth 3 /src user@host:/dst
 
-# Custom queue size for multithreading
-./build/client -m --queue-size 200 /src user@host:/dst
-
 # Log to file
 ./build/client --log-file /tmp/fastsync.log /src user@host:/dst
 
@@ -332,7 +324,7 @@ The benchmark prints throughput metrics, best configuration, and speedup vs rsyn
 1. Chunk size (~10 MB default) balances memory and transfer efficiency
 2. Compression level trades CPU for bandwidth
 3. `sendfile()` bypasses userspace — ~2× faster on localhost for large files
-4. Multithreading scales with core count; `--queue-size` controls pipeline buffering
+4. Multithreading scales with core count and uses memory-based pipeline sizing
 5. Metadata transfer adds negligible overhead (~24 bytes per file when enabled)
 6. SSH socketpair buffer set to 1 MB for improved pipe throughput
 7. SSH ControlMaster reuses connections across repeated invocations

RSYNC_COMPAT.md

@@ -0,0 +1,273 @@
+# Rsync Feature Compatibility
+
+This document maps rsync's full feature set to FastSync's current implementation status.
+
+## Summary
+
+| Status | Count | Description |
+|--------|-------|-------------|
+| ✅ Implemented | 34 | Feature works end-to-end |
+| 🔀 Alt Arg | 3 | Functionality exists but under different flag/semantics |
+| ⚠️ Partial | 1 | Flag parsed/stored but behavior incomplete |
+| ❌ Not Implemented | 98 | Flag not recognized or no behavior |
+| **Total** | **136** | |
+
+---
+
+## 1. General Options
+
+| Flag | Rsync Description | FastSync Status | Notes |
+|------|-------------------|-----------------|-------|
+| `-a`, `--archive` | Archive mode is -rlptgoD | 🔀 Alt Arg | Maps to -c -m -M (compression + multithread + metadata) |
+| `-v`, `--verbose` | Increase verbosity | ✅ Implemented | Sets `log_level=DEBUG` |
+| `-q`, `--quiet` | Suppress non-error messages | ❌ Not Implemented | Removed because it had no effect |
+| `--help` | Show help | ✅ Implemented | Prints usage and exits; `-h` is not accepted |
+| `-V`, `--version` | Print version | ✅ Implemented | |
+| `--info=FLAGS` | Fine-grained info verbosity | ❌ Not Implemented | Removed because it had no effect |
+| `--debug=FLAGS` | Fine-grained debug verbosity | ❌ Not Implemented | Removed because it had no effect |
+| `--stderr=MODE` | Change stderr output mode | ❌ Not Implemented | |
+| `--no-motd` | Suppress daemon MOTD | ❌ Not Implemented | |
+| `--exclude=PATTERN` | Exclude files matching pattern | ✅ Implemented | Glob matching in scanner |
+| `--include=PATTERN` | Include files matching pattern | ✅ Implemented | Glob matching in scanner |
+| `-C`, `--cvs-exclude` | Auto-ignore CVS files | ❌ Not Implemented | Removed because it had no effect |
+
+## 2. Modifying Output
+
+| Flag | Rsync Description | FastSync Status | Notes |
+|------|-------------------|-----------------|-------|
+| `--stats` | Give transfer stats | ✅ Implemented | Prints file/byte counts |
+| `-h`, `--human-readable` | Human-readable numbers | ❌ Not Implemented | Removed because it had no effect |
+| `-i`, `--itemize-changes` | Per-file change summary | ❌ Not Implemented | Removed because it had no effect |
+| `--progress` | Show progress | ✅ Implemented | Progress callback in sender |
+| `-P` | Same as --partial --progress | ❌ Not Implemented | |
+| `--out-format=FORMAT` | Custom output format | ❌ Not Implemented | Removed because it had no effect |
+| `--log-file=FILE` | Log to file | ✅ Implemented | `log_file` config field |
+| `--log-file-format=FMT` | Log format | ❌ Not Implemented | |
+| `--8-bit-output` | Leave high-bit chars unescaped | ❌ Not Implemented | |
+| `--list-only` | List files instead of copying | ❌ Not Implemented | Removed because it had no effect |
+
+## 3. File Selection
+
+| Flag | Rsync Description | FastSync Status | Notes |
+|------|-------------------|-----------------|-------|
+| `--exclude-from=FILE` | Read exclude patterns from file | ✅ Implemented | Reads patterns from file |
+| `--include-from=FILE` | Read include patterns from file | ✅ Implemented | Reads patterns from file |
+| `--filter=RULE` | Add file-filtering rule | ❌ Not Implemented | Removed because it had no effect |
+| `--files-from=FILE` | Read source file list from file | ❌ Not Implemented | Removed because it had no effect |
+| `-0`, `--from0` | Delimit *-from files with NULs | ❌ Not Implemented | |
+| `--max-size=SIZE` | Skip files larger than SIZE | ✅ Implemented | `max_size` in scanner |
+| `--min-size=SIZE` | Skip files smaller than SIZE | ✅ Implemented | `min_size` in scanner |
+| `-I`, `--ignore-times` | Don't skip files matching size+time | ❌ Not Implemented | |
+| `--size-only` | Skip based on size only | ❌ Not Implemented | |
+| `-@`, `--modify-window=NUM` | Mod-time comparison accuracy | ❌ Not Implemented | |
+| `--existing` | Skip creating new files on receiver | ❌ Not Implemented | |
+| `--ignore-existing` | Skip updating existing files | ❌ Not Implemented | |
+| `--remove-source-files` | Sender removes synced files | ❌ Not Implemented | |
+
+## 4. Directory Options
+
+| Flag | Rsync Description | FastSync Status | Notes |
+|------|-------------------|-----------------|-------|
+| `-r`, `--recursive` | Recurse into directories | ✅ Implemented | Default behavior |
+| `-R`, `--relative` | Use relative path names | ❌ Not Implemented | Removed because it had no effect |
+| `--no-implied-dirs` | Don't send implied dirs with -R | ❌ Not Implemented | |
+| `-d`, `--dirs` | Transfer dirs without recursing | ❌ Not Implemented | |
+| `--mkpath` | Create missing path components | ❌ Not Implemented | |
+
+## 5. Transfer Modifications
+
+| Flag | Rsync Description | FastSync Status | Notes |
+|------|-------------------|-----------------|-------|
+| `-u`, `--update` | Skip files newer on receiver | ❌ Not Implemented | Removed because it had no effect |
+| `--inplace` | Update files in-place | ✅ Implemented | Direct write mode |
+| `--append` | Append data to shorter files | ❌ Not Implemented | Removed because it had no effect |
+| `--append-verify` | Append with old-data checksum | ❌ Not Implemented | Removed because it had no effect |
+| `-W`, `--whole-file` | Copy whole file (no delta) | ❌ Not Implemented | |
+| `--block-size=SIZE` | Force checksum block-size | ⚠️ Partial | Parsed as `--delta-block`; controls delta transfer block size |
+
+## 6. Destination Handling
+
+| Flag | Rsync Description | FastSync Status | Notes |
+|------|-------------------|-----------------|-------|
+| `-n`, `--dry-run` | Trial run with no changes | ✅ Implemented | `dry_run` config field |
+| `-b`, `--backup` | Make backups of overwritten files | ✅ Implemented | Backup before overwrite |
+| `--backup-dir=DIR` | Backup directory hierarchy | ✅ Implemented | `backup_dir` config field |
+| `--suffix=SUFFIX` | Backup suffix (default ~) | ✅ Implemented | `suffix` config field |
+| `--delay-updates` | Put updated files in place at end | ❌ Not Implemented | |
+
+## 7. Deletion
+
+| Flag | Rsync Description | FastSync Status | Notes |
+|------|-------------------|-----------------|-------|
+| `--delete` | Delete extraneous files from dest | ✅ Implemented | `use_delete` config field |
+| `--delete-before` | Delete before transfer | ❌ Not Implemented | Removed because it had no effect |
+| `--delete-during` | Delete during transfer | ❌ Not Implemented | |
+| `--delete-delay` | Find deletions during, delete after | ❌ Not Implemented | |
+| `--delete-after` | Delete after transfer | ❌ Not Implemented | Removed because it had no effect |
+| `--delete-excluded` | Also delete excluded files | ❌ Not Implemented | Removed because it had no effect |
+| `--max-delete=NUM` | Max files to delete | ❌ Not Implemented | Removed because it had no effect |
+| `--ignore-errors` | Delete even with I/O errors | ❌ Not Implemented | |
+| `--force` | Force deletion of non-empty dirs | ❌ Not Implemented | |
+| `--prune-empty-dirs` | Prune empty dir chains | ❌ Not Implemented | Removed because it had no effect |
+
+## 8. Metadata Preservation
+
+| Flag | Rsync Description | FastSync Status | Notes |
+|------|-------------------|-----------------|-------|
+| `-M`, `--preserve` | Preserve file metadata | ✅ Implemented | Mode, uid, gid, mtime |
+| `-p`, `--perms` | Preserve permissions | 🔀 Alt Arg | `-p` means SSH port; permissions preserved via `-M`/`--preserve` |
+| `-o`, `--owner` | Preserve owner | ✅ Implemented | Part of -M |
+| `-g`, `--group` | Preserve group | ✅ Implemented | Part of -M |
+| `-t`, `--times` | Preserve modification times | ✅ Implemented | Part of -M |
+| `-E`, `--executability` | Preserve executability | ❌ Not Implemented | |
+| `--chmod=CHMOD` | Affect file permissions | ❌ Not Implemented | |
+| `-A`, `--acls` | Preserve ACLs | ❌ Not Implemented | Removed because it had no effect |
+| `-X`, `--xattrs` | Preserve extended attributes | ❌ Not Implemented | Removed because it had no effect |
+| `-H`, `--hard-links` | Preserve hard links | ❌ Not Implemented | Removed because it had no effect |
+| `-D` | Same as --devices --specials | ❌ Not Implemented | Removed because device-file handling is not implemented |
+| `--devices` | Preserve device files | ❌ Not Implemented | Removed because it had no effect |
+| `--specials` | Preserve special files | ❌ Not Implemented | |
+| `--copy-devices` | Copy device contents as file | ❌ Not Implemented | |
+| `--write-devices` | Write to devices as files | ❌ Not Implemented | |
+| `-U`, `--atimes` | Preserve access times | ❌ Not Implemented | |
+| `-N`, `--crtimes` | Preserve create times | ❌ Not Implemented | |
+| `-O`, `--omit-dir-times` | Omit dirs from --times | ❌ Not Implemented | |
+| `-J`, `--omit-link-times` | Omit symlinks from --times | ❌ Not Implemented | |
+| `--super` | Receiver attempts super-user activities | ❌ Not Implemented | |
+| `--fake-super` | Store/recover privileged attrs via xattrs | ❌ Not Implemented | |
+
+## 9. Symlink Handling
+
+| Flag | Rsync Description | FastSync Status | Notes |
+|------|-------------------|-----------------|-------|
+| `-l`, `--links` | Copy symlinks as symlinks | ⚠️ Partial | Scanner includes symlinks; target path not transmitted |
+| `-L`, `--copy-links` | Transform symlink to referent | ✅ Implemented | `copy_links` config field |
+| `--copy-unsafe-links` | Transform unsafe symlinks | ✅ Implemented | `copy_unsafe_links` config field |
+| `--safe-links` | Ignore symlinks outside tree | ✅ Implemented | `safe_links` config field |
+| `--munge-links` | Munge symlinks for safety | ❌ Not Implemented | |
+| `-k`, `--copy-dirlinks` | Transform symlink to dir | ❌ Not Implemented | |
+| `-K`, `--keep-dirlinks` | Treat symlinked dir as dir | ❌ Not Implemented | |
+
+## 10. Sparse & Device
+
+| Flag | Rsync Description | FastSync Status | Notes |
+|------|-------------------|-----------------|-------|
+| `-S`, `--sparse` | Sparse block handling | ✅ Implemented | `preserve_sparse` config field |
+| `--preallocate` | Allocate dest files before writing | ❌ Not Implemented | |
+
+## 11. Checksum & Comparison
+
+| Flag | Rsync Description | FastSync Status | Notes |
+|------|-------------------|-----------------|-------|
+| `--checksum` | Skip based on checksum | ❌ Not Implemented | Removed because it had no effect; `-c` means compression |
+| `--checksum-choice=STR` | Choose checksum algorithm | ❌ Not Implemented | xxHash used internally |
+| `--compare-dest=DIR` | Compare dest files relative to DIR | ❌ Not Implemented | Removed because it had no effect |
+| `--copy-dest=DIR` | Include copies of unchanged files | ❌ Not Implemented | Removed because it had no effect |
+| `--link-dest=DIR` | Hardlink to files when unchanged | ❌ Not Implemented | Removed because it had no effect |
+| `--fuzzy`, `--no-fuzzy` | Find similar file for basis | ❌ Not Implemented | |
+
+## 12. Compression
+
+| Flag | Rsync Description | FastSync Status | Notes |
+|------|-------------------|-----------------|-------|
+| `-z`, `--compress` | Compress file data | 🔀 Alt Arg | Always uses zstd (rsync supports multiple algorithms) |
+| `--compress-choice=STR` | Choose compression algorithm | ❌ Not Implemented | Removed because it had no effect; FastSync always uses zstd |
+| `--compress-level=NUM` | Set compression level | ✅ Implemented | 1-22, default 5 |
+| `--compress-threads=NUM` | Set compression threads | ❌ Not Implemented | |
+| `--skip-compress=LIST` | Skip compress for suffixes | ❌ Not Implemented | Internal skip for hardcoded types; not user-configurable |
+
+## 13. Connectivity
+
+| Flag | Rsync Description | FastSync Status | Notes |
+|------|-------------------|-----------------|-------|
+| `-e`, `--rsh=COMMAND` | Remote shell to use | ❌ Not Implemented | Removed; SSH invokes `ssh` directly |
+| `--rsync-path=PROGRAM` | rsync binary on remote | ❌ Not Implemented | Removed; use `--fastsync-server-path` |
+| `--port=PORT` | Alternate daemon port | ✅ Implemented | `server_port` config field |
+| `--sockopts=OPTIONS` | Custom TCP options | ❌ Not Implemented | |
+| `--blocking-io` | Use blocking I/O for remote shell | ❌ Not Implemented | |
+| `--outbuf=N\|L\|B` | Set output buffering | ❌ Not Implemented | |
+| `--address=ADDRESS` | Bind address for outgoing socket | ❌ Not Implemented | Removed because it had no effect |
+| `-4`, `--ipv4` | Prefer IPv4 | ❌ Not Implemented | Removed because it had no effect |
+| `-6`, `--ipv6` | Prefer IPv6 | ❌ Not Implemented | Removed because it had no effect |
+
+## 14. Daemon Mode
+
+| Flag | Rsync Description | FastSync Status | Notes |
+|------|-------------------|-----------------|-------|
+| `--daemon` | Run as rsync daemon | ❌ Not Implemented | Removed because it had no effect |
+| `--config=FILE` | Alternate rsyncd.conf file | ❌ Not Implemented | Removed because it had no effect |
+| `--dparam=OVERRIDE` | Override global daemon config | ❌ Not Implemented | |
+| `--no-detach` | Don't detach from parent | ❌ Not Implemented | |
+| `--password-file=FILE` | Read daemon password from file | ❌ Not Implemented | |
+| `--early-input=FILE` | Use FILE for daemon early exec | ❌ Not Implemented | |
+
+## 15. Safety & Security
+
+| Flag | Rsync Description | FastSync Status | Notes |
+|------|-------------------|-----------------|-------|
+| Path escape detection | Ensure files stay within root | ✅ Implemented | `has_path_traversal()` + realpath |
+| Symlink-safe delete | Skip symlinks in delete walk | ✅ Implemented | `delete_extras_walk()` |
+| Protocol version check | Verify compatible versions | ✅ Implemented | `config_receive()` |
+| Max data/string/chunk sizes | Prevent OOM attacks | ✅ Implemented | Per-message limits |
+| Per-connection memory limit | 1GB per connection | ✅ Implemented | `MAX_CONNECTION_MEMORY` |
+| `--trust-sender` | Trust remote sender's file list | ❌ Not Implemented | |
+| `--old-args` | Disable modern arg protection | ❌ Not Implemented | |
+| `--ignore-missing-args` | Ignore missing source args | ❌ Not Implemented | |
+| `--delete-missing-args` | Delete missing source args | ❌ Not Implemented | |
+
+## 16. Batch Operations
+
+| Flag | Rsync Description | FastSync Status | Notes |
+|------|-------------------|-----------------|-------|
+| `--write-batch=FILE` | Write batched update to file | ❌ Not Implemented | |
+| `--only-write-batch=FILE` | Write batch without updating dest | ❌ Not Implemented | |
+| `--read-batch=FILE` | Read batched update from file | ❌ Not Implemented | |
+
+## 17. Advanced
+
+| Flag | Rsync Description | FastSync Status | Notes |
+|------|-------------------|-----------------|-------|
+| `--stop-after=MINS` | Stop after N minutes | ❌ Not Implemented | |
+| `--stop-at=TIME` | Stop at specified time | ❌ Not Implemented | |
+| `--fsync` | Fsync every written file | ❌ Not Implemented | |
+| `--protocol=NUM` | Force older protocol version | ❌ Not Implemented | |
+| `--iconv=CONVERT_SPEC` | Charset conversion | ❌ Not Implemented | |
+| `--checksum-seed=NUM` | Set checksum seed | ❌ Not Implemented | |
+| `-s`, `--secluded-args` | Use protocol to send args | ❌ Not Implemented | |
+| `--no-OPTION` | Turn off implied option | ❌ Not Implemented | |
+
+---
+
+## Recommendations: Top Features to Implement Next
+
+Ranked by user demand, implementation complexity, and interoperability impact:
+
+| Priority | Feature | Effort | Impact |
+|----------|---------|--------|--------|
+| 1 | `--whole-file` / `-W` | Low | High — users expect opt-out of delta |
+| 2 | `--ignore-times` / `-I` | Low | Medium — useful for forcing re-transfer |
+| 3 | `--size-only` | Low | Medium — common migration scenario |
+| 4 | `--existing` / `--ignore-existing` | Low | Medium — common sync patterns |
+| 5 | `--remove-source-files` | Low | High — common for moves/backup |
+| 6 | `--delete-during` | Medium | High — performance improvement |
+| 7 | `--delay-updates` | Medium | High — atomic updates |
+| 8 | `--chmod` | Low | Medium — permission flexibility |
+| 9 | `--executability` / `-E` | Low | Low — simple flag |
+| 10 | `--skip-compress` | Low | Medium — performance tuning |
+
+---
+
+## FastSync-Specific Features (Not in rsync)
+
+| Feature | Description |
+|---------|-------------|
+| `-m` | Multithreaded pipeline (scanner/loader/sender) |
+| `-s` | Chunk serialization mode |
+| `-f` / `--sendfile` | Zero-copy sendfile() syscall (TCP only) |
+| `-c [level]` | zstd compression level (1-22) |
+| `--chunk-size` | Configurable chunk size |
+| `--tls` | TLS encryption (mutual auth) |
+| `--fastsync-server-path` | Path to fastsync-server binary |
+| `--server-host` / `--server-port` | Direct TCP connection |
+| Incremental sync | Skip unchanged files (size+mtime) |
+| Delta transfer | Block-level delta for changed files |

src/client/client_cli.c

@@ -8,132 +8,94 @@
 #include "utils.h"
 #include <errno.h>
 #include <limits.h>
+#include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include "usage.c"
 
-static void print_usage(void) {
-  printf("Usage:\n");
-  printf("  fastsync [options] <source> <destination>\n");
-  printf("  fastsync [options] --source-dir <src> --dest-dir <dst>\n");
-  printf("\n");
-  printf("Destination formats:\n");
-  printf("  user@host:/path     SSH transport (rsync-style)\n");
-  printf("  host:/path          SSH transport (current user)\n");
-  printf("  /local/path         TCP transport (requires server on localhost:8080)\n");
-  printf("\n");
-  printf("Options:\n");
-  printf("  -c [level]          Enable compression (level 1-22, default 5)\n");
-  printf("  -z [level]          Alias for -c\n");
-  printf("  -a, --archive       Archive mode (-c -m -M)\n");
-  printf("  -n, --dry-run       Show what would be transferred\n");
-  printf("  -p <port>           SSH port (default: 22)\n");
-  printf("  --progress          Show transfer progress\n");
-  printf("  --delete            Delete files on receiver not in source\n");
-  printf("  --exclude <pattern> Exclude files matching pattern\n");
-  printf("  --include <pattern> Only include files matching pattern\n");
-  printf("  --exclude-from <file> Read exclude patterns from file\n");
-  printf("  --include-from <file> Read include patterns from file\n");
-  printf("  --max-size <n>      Skip files larger than n bytes\n");
-  printf("  --min-size <n>      Skip files smaller than n bytes\n");
-  printf("  --incremental       Skip files unchanged since last transfer\n");
-  printf("  --delta             Delta transfer for changed files (requires --incremental)\n");
-  printf("  --delta-block <n>   Delta block size in bytes (default: %d)\n",
-         DELTA_BLOCK_SIZE_DEFAULT);
-  printf("  --delta-max <n>     Max file size for delta transfer (default: %llu)\n",
-         DELTA_MAX_FILE_SIZE);
-  printf("  -m                  Enable multithreading\n");
-  printf("  -s                  Enable chunk serialization\n");
-  printf("  -f                  Enable sendfile (TCP only, not with -c or -s)\n");
-  printf("  -v, --verbose       Enable debug logging\n");
-  printf("  -M, --preserve      Preserve file metadata\n");
-  printf("  --chunk-size <n>    Chunk size in bytes (default: %d)\n", DEFAULT_CHUNK_SIZE);
-  printf("  --source-dir <path> Source directory\n");
-  printf("  --dest-dir <path>   Destination directory\n");
-  printf("  --save-to-disk      Write received files to disk\n");
-  printf("  --server-host <ip>  Server IP address (default: 127.0.0.1)\n");
-  printf("  --server-port <n>   Server port (default: 8080)\n");
-  printf("  --bwlimit <KB/s>    Bandwidth limit in kilobytes per second\n");
-  printf("  --tls               Enable TLS encryption\n");
-  printf("  --cert <path>       TLS certificate file (PEM)\n");
-  printf("  --key <path>        TLS private key file (PEM)\n");
-  printf("  --ca <path>         TLS CA certificate file (PEM)\n");
-  printf("  --timeout <sec>     I/O timeout in seconds (default: 30)\n");
-  printf("  --contimeout <sec>  Connection timeout in seconds (default: 10)\n");
-  printf("  -q, --quiet         Suppress non-error output\n");
-  printf("  --silent            Alias for --quiet\n");
-  printf("  --backup            Backup existing files before overwriting\n");
-  printf("  --backup-dir <dir>  Directory for backups (requires --backup)\n");
-  printf("  --stats             Print transfer statistics at end\n");
-  printf("  --max-depth <n>     Maximum directory depth (0=unlimited)\n");
-  printf("  --log-file <path>   Write log messages to file\n");
-  printf("  --queue-size <n>    Queue capacity for multithreaded mode (default: 100)\n");
-  printf("  --partial           Keep partial files on interrupted transfer\n");
-  printf("  --fastsync-server-path <path>\n");
-  printf("                      Path to fastsync-server on remote (default: fastsync-server)\n");
-  printf("  --help              Show this help\n");
+#ifndef FASTSYNC_TEST_BUILD
+/* Parse environment variables for source/destination directories and save-to-disk flag. */
+static void parse_environment(const char** out_env_source, const char** out_env_dest,
+                              bool* out_save_to_disk) {
+  *out_env_source = getenv("FASTSYNC_SOURCE_DIR");
+  *out_env_dest = getenv("FASTSYNC_DEST_DIR");
+  const char* env_save = getenv("FASTSYNC_SAVE_TO_DISK");
+  *out_save_to_disk = false;
+  if (env_save && (strcmp(env_save, "true") == 0 || strcmp(env_save, "1") == 0))
+    *out_save_to_disk = true;
+}
+#endif
+
+/* Parse a string as a non-negative integer, returning true on success. */
+static bool parse_nonneg_int(const char* s, int* out_val) {
+  if (!s || *s == '\0')
+    return false;
+  char* endptr;
+  errno = 0;
+  long val = strtol(s, &endptr, 10);
+  if (errno != 0 || *endptr != '\0' || val < 0 || val > INT_MAX)
+    return false;
+  *out_val = (int)val;
+  return true;
 }
 
-static int read_patterns_from_file(const char* filepath, char*** patterns, int* count) {
-  FILE* fp = fopen(filepath, "r");
-  if (!fp) {
-    fprintf(stderr, "Error: could not open pattern file '%s': %s\n", filepath, strerror(errno));
+/* Parse a string as a positive integer, returning true on success. */
+static bool parse_positive_int(const char* s, int* out_val) {
+  int temp;
+  if (!parse_nonneg_int(s, &temp)) {
+    return false;
+  }
+  if (temp == 0) {
+    return false;
+  }
+  *out_val = temp;
+  return true;
+}
+
+/* Duplicate a string argument into *dest, freeing the old value. Returns true on success, false on
+ * failure. */
+static int set_string_option(char** dest, const char* value, const char* option_name) {
+  char* dup = str_dup(value);
+  if (!dup) {
+    fprintf(stderr, "Error: memory allocation failed for %s\n", option_name);
     return -1;
   }
-  char line[4096];
-  while (fgets(line, sizeof(line), fp)) {
-    char* p = line;
-    while (*p == ' ' || *p == '\t')
-      p++;
-    if (*p == '#' || *p == '\n' || *p == '\0')
-      continue;
-    size_t len = strlen(p);
-    while (len > 0 && (p[len - 1] == '\n' || p[len - 1] == '\r'))
-      p[--len] = '\0';
-    if (len == 0)
-      continue;
-    char** tmp = realloc(*patterns, (*count + 1) * sizeof(char*));
-    if (!tmp) {
-      fprintf(stderr, "Error: memory allocation failed for pattern file\n");
-      fclose(fp);
-      return -1;
-    }
-    *patterns = tmp;
-    (*patterns)[(*count)++] = str_dup(p);
-  }
-  fclose(fp);
+  free(*dest);
+  *dest = dup;
   return 0;
 }
 
-int main(int argc, char* argv[]) {
-  const char* env_source = getenv("FASTSYNC_SOURCE_DIR");
-  const char* env_dest = getenv("FASTSYNC_DEST_DIR");
-  const char* env_save = getenv("FASTSYNC_SAVE_TO_DISK");
-
-  bool save_to_disk = false;
-  if (env_save && (strcmp(env_save, "true") == 0 || strcmp(env_save, "1") == 0)) {
-    save_to_disk = true;
+/* Parse a string as a positive integer into *dest. Returns true on success, false on error. */
+static int set_positive_int_option(int* dest, const char* value, const char* option_name) {
+  if (!parse_positive_int(value, dest)) {
+    fprintf(stderr, "Error: %s must be a positive integer\n", option_name);
+    return -1;
+  }
+  return 0;
 }
 
-  int exit_code = 0;
-  Config* config = NULL;
-  bool config_owned_by_pipeline = false;
-
-  char* config_version = str_dup(PROTOCOL_VERSION);
-  if (!config_version) {
-    exit_code = 1;
-    goto cleanup;
+/* Parse a string as a non-negative integer into *dest. Returns true on success, false on error. */
+static int set_nonneg_int_option(int* dest, const char* value, const char* option_name) {
+  if (!parse_nonneg_int(value, dest)) {
+    fprintf(stderr, "Error: %s must be a non-negative integer\n", option_name);
+    return -1;
+  }
+  return 0;
 }
-  config = config_create(config_version, NULL, NULL, save_to_disk, false, false, false, false, 5,
-                         false, 0);
 
-  int positional_args[2];
-  int positional_count = 0;
+static int read_patterns_from_file(const char* filepath, char*** patterns, int* count);
 
+/* Parse CLI arguments into config. Returns 0 on success, -1 on error, 1 for help/clean-exit. */
+int parse_args(Config* config, int argc, char* argv[], int* positional_args,
+               int* positional_count) {
   for (int i = 1; i < argc; i++) {
     if (strcmp(argv[i], "--help") == 0) {
       print_usage();
-      goto cleanup;
+      return 1;
+    } else if (strcmp(argv[i], "-V") == 0 || strcmp(argv[i], "--version") == 0) {
+      printf("fastsync version %s\n", PROTOCOL_VERSION);
+      return 1;
     } else if (strcmp(argv[i], "-a") == 0 || strcmp(argv[i], "--archive") == 0) {
       config->use_compression = true;
       config->use_multithreading = true;
@@ -142,43 +104,82 @@ int main(int argc, char* argv[]) {
     } else if (strcmp(argv[i], "-n") == 0 || strcmp(argv[i], "--dry-run") == 0) {
       config->dry_run = true;
     } else if (strcmp(argv[i], "-p") == 0 && i + 1 < argc) {
-      config->ssh_port = atoi(argv[++i]);
+      if (set_positive_int_option(&config->ssh_port, argv[++i], "-p") != 0)
+        return -1;
+      if (config->ssh_port > 65535) {
+        log_message(LOG_LEVEL_ERROR, "SSH port must be 1-65535\n");
+        return -1;
+      }
     } else if (strcmp(argv[i], "--delete") == 0) {
       config->use_delete = true;
     } else if (strcmp(argv[i], "--exclude") == 0 && i + 1 < argc) {
       char** tmp = realloc(config->exclude_patterns, (config->exclude_count + 1) * sizeof(char*));
       if (!tmp) {
         fprintf(stderr, "Error: memory allocation failed for --exclude\n");
-        exit_code = 1;
-        goto cleanup;
+        return -1;
       }
       config->exclude_patterns = tmp;
-      config->exclude_patterns[config->exclude_count++] = str_dup(argv[++i]);
+      char* dup = str_dup(argv[++i]);
+      if (!dup) {
+        fprintf(stderr, "Error: memory allocation failed for --exclude\n");
+        return -1;
+      }
+      config->exclude_patterns[config->exclude_count++] = dup;
     } else if (strcmp(argv[i], "--include") == 0 && i + 1 < argc) {
       char** tmp = realloc(config->include_patterns, (config->include_count + 1) * sizeof(char*));
       if (!tmp) {
         fprintf(stderr, "Error: memory allocation failed for --include\n");
-        exit_code = 1;
-        goto cleanup;
+        return -1;
       }
       config->include_patterns = tmp;
-      config->include_patterns[config->include_count++] = str_dup(argv[++i]);
+      char* dup = str_dup(argv[++i]);
+      if (!dup) {
+        fprintf(stderr, "Error: memory allocation failed for --include\n");
+        return -1;
+      }
+      config->include_patterns[config->include_count++] = dup;
     } else if (strcmp(argv[i], "--max-size") == 0 && i + 1 < argc) {
-      config->max_size = strtoull(argv[++i], NULL, 10);
+      char* end;
+      errno = 0;
+      unsigned long long val = strtoull(argv[++i], &end, 10);
+      if (errno != 0 || *end != '\0') {
+        fprintf(stderr, "Error: --max-size must be a non-negative integer\n");
+        return -1;
+      }
+      config->max_size = val;
     } else if (strcmp(argv[i], "--min-size") == 0 && i + 1 < argc) {
-      config->min_size = strtoull(argv[++i], NULL, 10);
+      char* end;
+      errno = 0;
+      unsigned long long val = strtoull(argv[++i], &end, 10);
+      if (errno != 0 || *end != '\0') {
+        fprintf(stderr, "Error: --min-size must be a non-negative integer\n");
+        return -1;
+      }
+      config->min_size = val;
     } else if (strcmp(argv[i], "--incremental") == 0) {
       config->use_incremental = true;
     } else if (strcmp(argv[i], "--delta") == 0) {
       config->use_delta = true;
     } else if (strcmp(argv[i], "--delta-block") == 0 && i + 1 < argc) {
-      unsigned long long val = strtoull(argv[++i], NULL, 10);
+      char* end;
+      errno = 0;
+      unsigned long long val = strtoull(argv[++i], &end, 10);
+      if (errno != 0 || *end != '\0') {
+        fprintf(stderr, "Error: --delta-block must be a positive integer\n");
+        return -1;
+      }
       if (val >= DELTA_BLOCK_SIZE_MIN && val <= DELTA_BLOCK_SIZE_MAX)
         config->delta_block_size = (uint32_t)val;
       else
         fprintf(stderr, "Warning: --delta-block value %llu out of range, using default\n", val);
     } else if (strcmp(argv[i], "--delta-max") == 0 && i + 1 < argc) {
-      unsigned long long val = strtoull(argv[++i], NULL, 10);
+      char* end;
+      errno = 0;
+      unsigned long long val = strtoull(argv[++i], &end, 10);
+      if (errno != 0 || *end != '\0') {
+        fprintf(stderr, "Error: --delta-max must be a positive integer\n");
+        return -1;
+      }
       if (val >= DELTA_MIN_FILE_SIZE)
         config->delta_max_file_size = val;
       else
@@ -188,19 +189,23 @@ int main(int argc, char* argv[]) {
       log_message(LOG_LEVEL_INFO, "Enabled Compression");
       if (i + 1 < argc) {
         char* end_ptr;
-        int level = strtol(argv[i + 1], &end_ptr, 10);
+        long level = strtol(argv[i + 1], &end_ptr, 10);
         if (*end_ptr == '\0') {
-          config->compression_level = level;
-          log_message(LOG_LEVEL_INFO, "Set Compression level to %d", config->compression_level);
+          if (level < 1 || level > 22) {
+            fprintf(stderr, "Error: compression level must be 1-22\n");
+            return -1;
+          }
+          config->compression_level = (int)level;
+          log_message(LOG_LEVEL_INFO, "Set Compression level to %ld", level);
           i++;
         }
       }
     } else if (strcmp(argv[i], "--source-dir") == 0 && i + 1 < argc) {
-      free(config->send_directory);
-      config->send_directory = str_dup(argv[++i]);
+      if (set_string_option(&config->send_directory, argv[++i], "--source-dir") != 0)
+        return -1;
     } else if (strcmp(argv[i], "--dest-dir") == 0 && i + 1 < argc) {
-      free(config->receive_root_directory);
-      config->receive_root_directory = str_dup(argv[++i]);
+      if (set_string_option(&config->receive_root_directory, argv[++i], "--dest-dir") != 0)
+        return -1;
     } else if (strcmp(argv[i], "--save-to-disk") == 0) {
       config->save_to_disk = true;
     } else if (strcmp(argv[i], "-M") == 0 || strcmp(argv[i], "--preserve") == 0) {
@@ -216,132 +221,271 @@ int main(int argc, char* argv[]) {
       config->use_chunk_serialization = true;
       log_message(LOG_LEVEL_INFO, "Enabled Chunk Serialization");
     } else if (strcmp(argv[i], "--server-host") == 0 && i + 1 < argc) {
-      free(config->server_host);
-      config->server_host = str_dup(argv[++i]);
+      if (set_string_option(&config->server_host, argv[++i], "--server-host") != 0)
+        return -1;
     } else if (strcmp(argv[i], "--server-port") == 0 && i + 1 < argc) {
-      config->server_port = atoi(argv[++i]);
+      if (!parse_positive_int(argv[++i], &config->server_port)) {
+        fprintf(stderr, "Error: invalid --server-port value: %s\n", argv[i]);
+        return -1;
+      }
+      if (config->server_port > 65535) {
+        fprintf(stderr, "Error: server port must be 1-65535\n");
+        return -1;
+      }
     } else if (strcmp(argv[i], "--bwlimit") == 0 && i + 1 < argc) {
       char* end;
       errno = 0;
       unsigned long long kbps = strtoull(argv[++i], &end, 10);
       if (errno != 0 || *end != '\0' || kbps == 0) {
         fprintf(stderr, "Error: --bwlimit must be a positive integer\n");
-        exit_code = 1;
-        goto cleanup;
+        return -1;
       }
       if (kbps > ULLONG_MAX / 1024) {
         fprintf(stderr, "Error: --bwlimit value too large\n");
-        exit_code = 1;
-        goto cleanup;
+        return -1;
       }
       io_set_bwlimit(kbps * 1024);
       log_message(LOG_LEVEL_INFO, "Set bandwidth limit to %llu KB/s", kbps);
     } else if (strcmp(argv[i], "--progress") == 0) {
       config->show_progress = true;
     } else if (strcmp(argv[i], "--chunk-size") == 0 && i + 1 < argc) {
-      unsigned long long val = strtoull(argv[++i], NULL, 10);
-      if (val > 0)
+      char* end;
+      errno = 0;
+      unsigned long long val = strtoull(argv[++i], &end, 10);
+      if (errno != 0 || *end != '\0' || val == 0) {
+        fprintf(stderr, "Error: --chunk-size must be a positive integer\n");
+        return -1;
+      }
       config->chunk_size = val;
     } else if (strcmp(argv[i], "--tls") == 0) {
       config->use_tls = true;
     } else if (strcmp(argv[i], "--cert") == 0 && i + 1 < argc) {
-      free(config->tls_cert);
-      config->tls_cert = str_dup(argv[++i]);
+      if (set_string_option(&config->tls_cert, argv[++i], "--cert") != 0)
+        return -1;
     } else if (strcmp(argv[i], "--key") == 0 && i + 1 < argc) {
-      free(config->tls_key);
-      config->tls_key = str_dup(argv[++i]);
+      if (set_string_option(&config->tls_key, argv[++i], "--key") != 0)
+        return -1;
     } else if (strcmp(argv[i], "--ca") == 0 && i + 1 < argc) {
-      free(config->tls_ca);
-      config->tls_ca = str_dup(argv[++i]);
+      if (set_string_option(&config->tls_ca, argv[++i], "--ca") != 0)
+        return -1;
     } else if (strcmp(argv[i], "--timeout") == 0 && i + 1 < argc) {
-      config->timeout = atoi(argv[++i]);
-      if (config->timeout <= 0) {
-        fprintf(stderr, "Error: --timeout must be a positive integer\n");
-        exit_code = 1;
-        goto cleanup;
-      }
+      if (set_positive_int_option(&config->timeout, argv[++i], "--timeout") != 0)
+        return -1;
     } else if (strcmp(argv[i], "--contimeout") == 0 && i + 1 < argc) {
-      config->contimeout = atoi(argv[++i]);
-      if (config->contimeout <= 0) {
-        fprintf(stderr, "Error: --contimeout must be a positive integer\n");
-        exit_code = 1;
-        goto cleanup;
-      }
-    } else if (strcmp(argv[i], "-q") == 0 || strcmp(argv[i], "--quiet") == 0 ||
-               strcmp(argv[i], "--silent") == 0) {
-      config->quiet = true;
+      if (set_positive_int_option(&config->contimeout, argv[++i], "--contimeout") != 0)
+        return -1;
     } else if (strcmp(argv[i], "--backup") == 0) {
       config->backup = true;
     } else if (strcmp(argv[i], "--backup-dir") == 0 && i + 1 < argc) {
-      config->backup_dir = str_dup(argv[++i]);
+      if (set_string_option(&config->backup_dir, argv[++i], "--backup-dir") != 0)
+        return -1;
     } else if (strcmp(argv[i], "--stats") == 0) {
       config->stats = true;
     } else if (strcmp(argv[i], "--max-depth") == 0 && i + 1 < argc) {
-      config->max_depth = atoi(argv[++i]);
-      if (config->max_depth < 0) {
-        fprintf(stderr, "Error: --max-depth must be a non-negative integer\n");
-        exit_code = 1;
-        goto cleanup;
-      }
+      if (set_nonneg_int_option(&config->max_depth, argv[++i], "--max-depth") != 0)
+        return -1;
     } else if (strcmp(argv[i], "--log-file") == 0 && i + 1 < argc) {
+      if (config->log_file) {
+        fclose(config->log_file);
+        config->log_file = NULL;
+        log_set_file(NULL);
+      }
       FILE* lf = fopen(argv[++i], "a");
       if (!lf) {
         fprintf(stderr, "Error: could not open log file '%s': %s\n", argv[i], strerror(errno));
-        exit_code = 1;
-        goto cleanup;
+        return -1;
       }
       config->log_file = lf;
       log_set_file(lf);
-    } else if (strcmp(argv[i], "--queue-size") == 0 && i + 1 < argc) {
-      config->queue_size = atoi(argv[++i]);
-      if (config->queue_size <= 0) {
-        fprintf(stderr, "Error: --queue-size must be a positive integer\n");
-        exit_code = 1;
-        goto cleanup;
-      }
     } else if (strcmp(argv[i], "--exclude-from") == 0 && i + 1 < argc) {
       if (read_patterns_from_file(argv[++i], &config->exclude_patterns, &config->exclude_count) !=
-          0) {
-        exit_code = 1;
-        goto cleanup;
-      }
+          0)
+        return -1;
     } else if (strcmp(argv[i], "--include-from") == 0 && i + 1 < argc) {
       if (read_patterns_from_file(argv[++i], &config->include_patterns, &config->include_count) !=
-          0) {
-        exit_code = 1;
-        goto cleanup;
-      }
+          0)
+        return -1;
     } else if (strcmp(argv[i], "--partial") == 0) {
       config->partial = true;
     } else if (strcmp(argv[i], "--fastsync-server-path") == 0 && i + 1 < argc) {
-      free(config->fastsync_server_path);
-      config->fastsync_server_path = str_dup(argv[++i]);
+      if (set_string_option(&config->fastsync_server_path, argv[++i], "--fastsync-server-path") !=
+          0)
+        return -1;
     } else if (strcmp(argv[i], "-v") == 0 || strcmp(argv[i], "--verbose") == 0) {
       set_log_level(LOG_LEVEL_DEBUG);
+    } else if (strcmp(argv[i], "-l") == 0 || strcmp(argv[i], "--links") == 0) {
+      config->follow_symlinks = true;
+    } else if (strcmp(argv[i], "--copy-links") == 0) {
+      config->copy_links = true;
+    } else if (strcmp(argv[i], "--safe-links") == 0) {
+      config->safe_links = true;
+    } else if (strcmp(argv[i], "--copy-unsafe-links") == 0) {
+      config->copy_unsafe_links = true;
+    } else if (strcmp(argv[i], "-S") == 0 || strcmp(argv[i], "--sparse") == 0) {
+      config->preserve_sparse = true;
+    } else if (strcmp(argv[i], "--inplace") == 0) {
+      config->inplace = true;
+    } else if (strcmp(argv[i], "--partial-dir") == 0 && i + 1 < argc) {
+      if (set_string_option(&config->partial_dir, argv[++i], "--partial-dir") != 0)
+        return -1;
+    } else if (strcmp(argv[i], "--suffix") == 0 && i + 1 < argc) {
+      if (set_string_option(&config->suffix, argv[++i], "--suffix") != 0)
+        return -1;
+    } else if (strcmp(argv[i], "-T") == 0 && i + 1 < argc) {
+      if (set_positive_int_option(&config->timeout, argv[++i], "-T") != 0)
+        return -1;
+    } else if (strcmp(argv[i], "--compress-level") == 0 && i + 1 < argc) {
+      if (set_positive_int_option(&config->compression_level, argv[++i], "--compress-level") != 0)
+        return -1;
+      if (config->compression_level < 1 || config->compression_level > 22) {
+        fprintf(stderr, "Error: --compress-level must be between 1 and 22\n");
+        return -1;
+      }
     } else if (argv[i][0] == '-') {
       fprintf(stderr, "Unknown option: %s\n", argv[i]);
       print_usage();
-      exit_code = 1;
-      goto cleanup;
+      return -1;
     } else {
-      if (positional_count < 2)
-        positional_args[positional_count++] = i;
+      if (*positional_count < 2)
+        positional_args[(*positional_count)++] = i;
       else {
         fprintf(stderr, "Unexpected argument: %s\n", argv[i]);
         print_usage();
+        return -1;
+      }
+    }
+  }
+  return 0;
+}
+
+#ifndef FASTSYNC_TEST_BUILD
+/* Validate config after parsing. Returns true if valid. */
+static bool validate_config(const Config* config) {
+  if (!config->send_directory || !config->receive_root_directory) {
+    fprintf(stderr, "Error: source and destination directories are required\n");
+    print_usage();
+    return false;
+  }
+  if (config->use_sendfile && (config->use_chunk_serialization || config->use_compression)) {
+    fprintf(stderr, "Error: -f/--sendfile cannot be combined with -c (compression) or -s (chunk "
+                    "serialization)\n");
+    return false;
+  }
+  if (config->transport == TRANSPORT_SSH && config->use_sendfile) {
+    fprintf(stderr, "Error: -f/--sendfile is not supported with SSH transport\n");
+    return false;
+  }
+  if (config->use_incremental && config->use_chunk_serialization) {
+    fprintf(stderr, "Error: --incremental is not supported with -s (chunk serialization)\n");
+    return false;
+  }
+  if (config->use_delta && !config->use_incremental) {
+    fprintf(stderr, "Error: --delta requires --incremental\n");
+    return false;
+  }
+  if (config->use_delta && config->use_chunk_serialization) {
+    fprintf(stderr, "Error: --delta cannot be combined with -s (chunk serialization)\n");
+    return false;
+  }
+  if (config->use_delta && config->use_sendfile) {
+    fprintf(stderr, "Error: --delta cannot be combined with -f (sendfile)\n");
+    return false;
+  }
+  if (config->use_tls) {
+    if (!config->tls_cert || !config->tls_key) {
+      fprintf(stderr, "Error: --tls requires --cert and --key\n");
+      return false;
+    }
+  }
+  return true;
+}
+#endif /* FASTSYNC_TEST_BUILD */
+
+static int read_patterns_from_file(const char* filepath, char*** patterns, int* count) {
+  FILE* fp = fopen(filepath, "r");
+  if (!fp) {
+    fprintf(stderr, "Error: could not open pattern file '%s': %s\n", filepath, strerror(errno));
+    return -1;
+  }
+  char* line = NULL;
+  size_t line_size = 0;
+  ssize_t n;
+  while ((n = getline(&line, &line_size, fp)) != -1) {
+    char* p = line;
+    while (*p == ' ' || *p == '\t')
+      p++;
+    if (*p == '#' || *p == '\n' || *p == '\0')
+      continue;
+    size_t len = strlen(p);
+    while (len > 0 && (p[len - 1] == '\n' || p[len - 1] == '\r'))
+      p[--len] = '\0';
+    if (len == 0)
+      continue;
+    char** tmp = realloc(*patterns, (*count + 1) * sizeof(char*));
+    if (!tmp) {
+      fprintf(stderr, "Error: memory allocation failed for pattern file\n");
+      free(line);
+      fclose(fp);
+      return -1;
+    }
+    *patterns = tmp;
+    char* dup = str_dup(p);
+    if (!dup) {
+      fprintf(stderr, "Error: memory allocation failed for pattern file\n");
+      free(line);
+      fclose(fp);
+      return -1;
+    }
+    (*patterns)[(*count)++] = dup;
+  }
+  free(line);
+  fclose(fp);
+  return 0;
+}
+
+#ifndef FASTSYNC_TEST_BUILD
+int main(int argc, char* argv[]) {
+  const char* env_source = NULL;
+  const char* env_dest = NULL;
+  bool save_to_disk = false;
+  parse_environment(&env_source, &env_dest, &save_to_disk);
+
+  int exit_code = 0;
+  bool config_owned_by_pipeline = false;
+  Config* config = config_create();
+  if (!config) {
+    fprintf(stderr, "Error: failed to allocate config\n");
+    return 1;
+  }
+  config->save_to_disk = save_to_disk;
+
+  int positional_args[2];
+  int positional_count = 0;
+
+  int parse_ret = parse_args(config, argc, argv, positional_args, &positional_count);
+  if (parse_ret != 0) {
+    if (parse_ret < 0)
       exit_code = 1;
     goto cleanup;
   }
-    }
-  }
 
+  /* Handle positional arguments or fall back to environment variables */
   if (positional_count == 2) {
     free(config->send_directory);
     free(config->receive_root_directory);
     config->send_directory = str_dup(argv[positional_args[0]]);
+    if (!config->send_directory) {
+      fprintf(stderr, "Error: memory allocation failed\n");
+      exit_code = 1;
+      goto cleanup;
+    }
     config->receive_root_directory = str_dup(argv[positional_args[1]]);
+    if (!config->receive_root_directory) {
+      fprintf(stderr, "Error: memory allocation failed\n");
+      exit_code = 1;
+      goto cleanup;
+    }
     config->save_to_disk = true;
-
     config_parse_ssh_dest(config);
   } else if (positional_count == 1) {
     fprintf(stderr, "Error: missing destination argument\n");
@@ -349,73 +493,46 @@ int main(int argc, char* argv[]) {
     exit_code = 1;
     goto cleanup;
   } else {
-    if (!config->send_directory && env_source)
-      config->send_directory = str_dup((char*)env_source);
-    if (!config->receive_root_directory && env_dest)
-      config->receive_root_directory = str_dup((char*)env_dest);
-  }
-
-  if (!config->send_directory || !config->receive_root_directory) {
-    fprintf(stderr, "Error: source and destination directories are required\n");
-    print_usage();
+    if (!config->send_directory && env_source) {
+      config->send_directory = str_dup(env_source);
+      if (!config->send_directory) {
+        fprintf(stderr, "Error: memory allocation failed\n");
         exit_code = 1;
         goto cleanup;
       }
-  if (config->use_sendfile && (config->use_chunk_serialization || config->use_compression)) {
-    fprintf(stderr, "Error: -f/--sendfile cannot be combined with -c (compression) or -s (chunk "
-                    "serialization)\n");
-    exit_code = 1;
-    goto cleanup;
-  }
-
-  if (config->transport == TRANSPORT_SSH && config->use_sendfile) {
-    fprintf(stderr, "Error: -f/--sendfile is not supported with SSH transport\n");
-    exit_code = 1;
-    goto cleanup;
-  }
-
-  if (config->use_incremental && config->use_chunk_serialization) {
-    fprintf(stderr, "Error: --incremental is not supported with -s (chunk serialization)\n");
+    }
+    if (!config->receive_root_directory && env_dest) {
+      config->receive_root_directory = str_dup(env_dest);
+      if (!config->receive_root_directory) {
+        fprintf(stderr, "Error: memory allocation failed\n");
+        exit_code = 1;
+        goto cleanup;
+      }
+    }
+  }
+
+  if (!validate_config(config)) {
     exit_code = 1;
     goto cleanup;
   }
 
+  /* Enable implicit flags */
   if (config->use_incremental && !config->use_metadata) {
     log_message(LOG_LEVEL_INFO, "Enabling metadata preservation for --incremental");
     config->use_metadata = true;
   }
-
-  if (config->use_delta && !config->use_incremental) {
-    fprintf(stderr, "Error: --delta requires --incremental\n");
-    exit_code = 1;
-    goto cleanup;
-  }
-  if (config->use_delta && config->use_chunk_serialization) {
-    fprintf(stderr, "Error: --delta cannot be combined with -s (chunk serialization)\n");
-    exit_code = 1;
-    goto cleanup;
-  }
-  if (config->use_delta && config->use_sendfile) {
-    fprintf(stderr, "Error: --delta cannot be combined with -f (sendfile)\n");
-    exit_code = 1;
-    goto cleanup;
-  }
   if (config->use_delta && !config->use_metadata) {
     log_message(LOG_LEVEL_INFO, "Enabling metadata preservation for --delta");
     config->use_metadata = true;
   }
 
-  if (config->use_tls) {
-    if (!config->tls_cert || !config->tls_key) {
-      fprintf(stderr, "Error: --tls requires --cert and --key\n");
-      exit_code = 1;
-      goto cleanup;
-    }
+  /* Initialize TLS if needed */
+  if (config->use_tls)
     tls_global_init();
-  }
 
   tcp_set_timeouts(config->timeout, config->contimeout);
 
+  /* Execute transfer */
   if (config->use_multithreading) {
     config_owned_by_pipeline = true;
     exit_code = send_files_multithreaded(config);
@@ -432,3 +549,4 @@ cleanup:
   }
   return exit_code;
 }
+#endif /* FASTSYNC_TEST_BUILD */

src/client/client_send.c

@@ -25,6 +25,48 @@
 
 #define STREAM_THRESHOLD (64ULL * 1024 * 1024)
 
+/* Forward declaration for progress-reporting thread used in multithreaded send. */
+static int progress_thread_fn(void* arg);
+
+/* Print dry-run manifest showing files that would be transferred. Returns 0 on success. */
+static int send_dry_run_manifest(Config* config) {
+  DirectoryScanner* scanner = directory_scanner_create(
+      config->send_directory, config->use_metadata, config->chunk_size, config->exclude_patterns,
+      config->exclude_count, config->include_patterns, config->include_count, config->max_size,
+      config->min_size, config->max_depth, config->follow_symlinks, config->copy_links,
+      config->safe_links, config->copy_unsafe_links);
+  if (!scanner)
+    return -1;
+  Chunk* chunk;
+  int file_count = 0;
+  unsigned long long total_bytes = 0;
+  printf("Dry run: files to be transferred\n");
+  while ((chunk = directory_scanner_next(scanner)) != NULL) {
+    for (int i = 0; i < chunk->element_count; i++) {
+      printf("  %s (%zu bytes)\n", chunk->items[i]->path, chunk->items[i]->data->size);
+      total_bytes += chunk->items[i]->data->size;
+      file_count++;
+    }
+    chunk_destroy(chunk);
+  }
+  directory_scanner_destroy(scanner);
+  printf("Total: %d files, %.1f MB\n", file_count, total_bytes / 1048576.0);
+  return 0;
+}
+
+/* Send the delete manifest (list of files) to the server. Returns 0 on success, -1 on failure. */
+static int send_delete_manifest(int fd, ArrayList* manifest) {
+  if (!send_status(fd, STATUS_MANIFEST))
+    return -1;
+  if (!send_int(fd, manifest->size))
+    return -1;
+  for (int i = 0; i < manifest->size; i++) {
+    if (!send_str(fd, (char*)manifest->items[i]))
+      return -1;
+  }
+  return 0;
+}
+
 static int incremental_check(Client* client, File* file, DeltaSignature** out_sig) {
   *out_sig = NULL;
   if (!send_status(client->file_descriptor, STATUS_CHECK))
@@ -232,6 +274,9 @@ static int send_chunks_multithreaded(void* pipeline_context) {
   if (context->config->transport == TRANSPORT_SSH) {
     if (context->config->use_sendfile) {
       fprintf(stderr, "Error: -f/--sendfile is not supported with SSH transport\n");
+      mtx_lock(&context->mutex_progress);
+      context->sender_done = true;
+      mtx_unlock(&context->mutex_progress);
       return 1;
     }
     client = client_connect_ssh(context->config->ssh_destination, context->config->ssh_port,
@@ -244,6 +289,9 @@ static int send_chunks_multithreaded(void* pipeline_context) {
       if (client)
         client_delete(client);
       fprintf(stderr, "Error: could not connect to server via TLS\n");
+      mtx_lock(&context->mutex_progress);
+      context->sender_done = true;
+      mtx_unlock(&context->mutex_progress);
       return thrd_error;
     }
   } else {
@@ -253,12 +301,18 @@ static int send_chunks_multithreaded(void* pipeline_context) {
       if (client)
         client_delete(client);
       fprintf(stderr, "Error: could not connect to server\n");
+      mtx_lock(&context->mutex_progress);
+      context->sender_done = true;
+      mtx_unlock(&context->mutex_progress);
       return thrd_error;
     }
   }
   if (!config_send(client->file_descriptor, context->config)) {
     client_disconnect(client);
     client_delete(client);
+    mtx_lock(&context->mutex_progress);
+    context->sender_done = true;
+    mtx_unlock(&context->mutex_progress);
     return thrd_error;
   }
 
@@ -268,14 +322,8 @@ static int send_chunks_multithreaded(void* pipeline_context) {
         &context->condition_not_full_loader, &context->loader_done);
     if (current_chunk == NULL) {
       if (context->config->use_delete) {
-        if (!send_status(client->file_descriptor, STATUS_MANIFEST))
+        if (send_delete_manifest(client->file_descriptor, context->manifest) != 0)
           goto send_fail;
-        if (!send_int(client->file_descriptor, context->manifest->size))
-          goto send_fail;
-        for (int i = 0; i < context->manifest->size; i++) {
-          if (!send_str(client->file_descriptor, (char*)context->manifest->items[i]))
-            goto send_fail;
-        }
       }
       if (!send_status(client->file_descriptor, STATUS_FINISHED))
         goto send_fail;
@@ -283,19 +331,39 @@ static int send_chunks_multithreaded(void* pipeline_context) {
       int ok = receive_status(client->file_descriptor, &s) && s == STATUS_OK;
       client_disconnect(client);
       client_delete(client);
+      mtx_lock(&context->mutex_progress);
+      context->sender_done = true;
+      mtx_unlock(&context->mutex_progress);
       return ok ? thrd_success : thrd_error;
 
     send_fail:
       client_disconnect(client);
       client_delete(client);
+      mtx_lock(&context->mutex_progress);
+      context->sender_done = true;
+      mtx_unlock(&context->mutex_progress);
       return thrd_error;
     }
     if (send_chunk(client, current_chunk, context->config) != 0) {
       fprintf(stderr, "Error: unexpected error while sending chunk\n");
+      chunk_destroy(current_chunk);
       client_disconnect(client);
       client_delete(client);
+      mtx_lock(&context->mutex_progress);
+      context->sender_done = true;
+      mtx_unlock(&context->mutex_progress);
       return thrd_error;
     }
+    if (context->config->show_progress) {
+      unsigned long long chunk_bytes = 0;
+      for (int i = 0; i < current_chunk->element_count; i++) {
+        if (current_chunk->items[i] && current_chunk->items[i]->data)
+          chunk_bytes += current_chunk->items[i]->data->size;
+      }
+      mtx_lock(&context->mutex_progress);
+      context->progress_bytes += chunk_bytes;
+      mtx_unlock(&context->mutex_progress);
+    }
     chunk_destroy(current_chunk);
   }
 }
@@ -306,7 +374,8 @@ static int scan_directory_multithreaded(void* pipeline_context) {
       context->config->send_directory, context->config->use_metadata, context->config->chunk_size,
       context->config->exclude_patterns, context->config->exclude_count,
       context->config->include_patterns, context->config->include_count, context->config->max_size,
-      context->config->min_size, context->config->max_depth, 4);
+      context->config->min_size, context->config->max_depth, 4, context->config->follow_symlinks,
+      context->config->copy_links, context->config->safe_links, context->config->copy_unsafe_links);
 
   Chunk* current_chunk;
   while ((current_chunk = parallel_scanner_next(scanner)) != NULL) {
@@ -316,13 +385,31 @@ static int scan_directory_multithreaded(void* pipeline_context) {
         const char* p = current_chunk->items[i]->path;
         if (*p == '/')
           p++;
-        array_list_add(context->manifest, str_dup(p));
+        char* manifest_entry = str_dup(p);
+        if (!manifest_entry) {
+          log_message(LOG_LEVEL_ERROR, "Failed to allocate manifest entry");
+          mtx_unlock(&context->mutex_scanner);
+          context->cancelled = true;
+          cnd_broadcast(&context->condition_not_full_scanner);
+          cnd_broadcast(&context->condition_not_empty_scanner);
+          parallel_scanner_destroy(scanner);
+          return thrd_error;
+        }
+        array_list_add(context->manifest, manifest_entry);
       }
       mtx_unlock(&context->mutex_scanner);
     }
-    queue_enqueue_multithreaded(context->queue_scanner, current_chunk, &context->mutex_scanner,
-                                &context->condition_not_empty_scanner,
-                                &context->condition_not_full_scanner);
+    if (!queue_enqueue_multithreaded_cancel(
+            context->queue_scanner, current_chunk, &context->mutex_scanner,
+            &context->condition_not_empty_scanner, &context->condition_not_full_scanner,
+            &context->cancelled)) {
+      chunk_destroy(current_chunk);
+      context->cancelled = true;
+      cnd_broadcast(&context->condition_not_full_scanner);
+      cnd_broadcast(&context->condition_not_empty_scanner);
+      parallel_scanner_destroy(scanner);
+      return thrd_error;
+    }
   }
   mtx_lock(&context->mutex_scanner);
   context->scanner_done = true;
@@ -358,34 +445,58 @@ static int load_files_multithreaded(void* pipeline_context) {
         }
       }
     }
-    queue_enqueue_multithreaded(context->queue_loader, chunk, &context->mutex_loader,
+    if (!queue_enqueue_multithreaded_cancel(context->queue_loader, chunk, &context->mutex_loader,
                                             &context->condition_not_empty_loader,
-                                &context->condition_not_full_loader);
+                                            &context->condition_not_full_loader,
+                                            &context->cancelled)) {
+      chunk_destroy(chunk);
+      context->cancelled = true;
+      cnd_broadcast(&context->condition_not_full_loader);
+      cnd_broadcast(&context->condition_not_empty_loader);
+      return thrd_error;
+    }
   }
 }
 
+/* Progress-reporting thread for multithreaded send. Runs in parallel with
+   the scanner/loader/sender threads and prints periodic progress to stderr. */
+static int progress_thread_fn(void* arg) {
+  PipelineContextSender* context = (PipelineContextSender*)arg;
+  time_t last_progress = 0;
+  time_t start = time(NULL);
+
+  while (true) {
+    mtx_lock(&context->mutex_progress);
+    bool done = context->sender_done;
+    unsigned long long total = context->progress_bytes;
+    mtx_unlock(&context->mutex_progress);
+
+    if (done) {
+      time_t now = time(NULL);
+      double elapsed = difftime(now, start);
+      double rate = elapsed > 0.0 ? total / (1048576.0 * elapsed) : 0.0;
+      fprintf(stderr, "\rSent %.1f MB  (%.1f MB/s)  Done.\n", total / 1048576.0, rate);
+      break;
+    }
+
+    time_t now = time(NULL);
+    if (now - last_progress >= 1) {
+      last_progress = now;
+      double elapsed = difftime(now, start);
+      double rate = elapsed > 0.0 ? total / (1048576.0 * elapsed) : 0.0;
+      fprintf(stderr, "\rSent %.1f MB  (%.1f MB/s)  ", total / 1048576.0, rate);
+      fflush(stderr);
+    }
+
+    struct timespec ts = {0, 100 * 1000000L}; /* 100 ms */
+    thrd_sleep(&ts, NULL);
+  }
+  return thrd_success;
+}
+
 int send_files(Config* config) {
-  if (config->dry_run) {
-    DirectoryScanner* scanner = directory_scanner_create(
-        config->send_directory, config->use_metadata, config->chunk_size, config->exclude_patterns,
-        config->exclude_count, config->include_patterns, config->include_count, config->max_size,
-        config->min_size, config->max_depth);
-    Chunk* chunk;
-    int file_count = 0;
-    unsigned long long total_bytes = 0;
-    printf("Dry run: files to be transferred\n");
-    while ((chunk = directory_scanner_next(scanner)) != NULL) {
-      for (int i = 0; i < chunk->element_count; i++) {
-        printf("  %s (%zu bytes)\n", chunk->items[i]->path, chunk->items[i]->data->size);
-        total_bytes += chunk->items[i]->data->size;
-        file_count++;
-      }
-      chunk_destroy(chunk);
-    }
-    directory_scanner_destroy(scanner);
-    printf("Total: %d files, %.1f MB\n", file_count, total_bytes / 1048576.0);
-    return 0;
-  }
+  if (config->dry_run)
+    return send_dry_run_manifest(config);
 
   Client* client;
   if (config->transport == TRANSPORT_SSH) {
@@ -401,16 +512,20 @@ int send_files(Config* config) {
     client = client_create();
     if (!client || !client_connect_tls(client, config->server_host, config->server_port,
                                        config->tls_cert, config->tls_key, config->tls_ca)) {
-      if (client)
+      if (client) {
+        client_disconnect(client);
         client_delete(client);
+      }
       fprintf(stderr, "Error: could not connect to server via TLS\n");
       return 1;
     }
   } else {
     client = client_create();
     if (!client || !client_connect(client, config->server_host, config->server_port)) {
-      if (client)
+      if (client) {
+        client_disconnect(client);
         client_delete(client);
+      }
       fprintf(stderr, "Error: could not connect to server\n");
       return 1;
     }
@@ -423,9 +538,11 @@ int send_files(Config* config) {
   DirectoryScanner* scanner = directory_scanner_create(
       config->send_directory, config->use_metadata, config->chunk_size, config->exclude_patterns,
       config->exclude_count, config->include_patterns, config->include_count, config->max_size,
-      config->min_size, config->max_depth);
+      config->min_size, config->max_depth, config->follow_symlinks, config->copy_links,
+      config->safe_links, config->copy_unsafe_links);
   Chunk* current_chunk;
   unsigned long long total_bytes = 0;
+  int total_files = 0;
   time_t last_progress = 0;
   time_t start = time(NULL);
   ArrayList* manifest = config->use_delete ? array_list_create(free) : NULL;
@@ -433,11 +550,22 @@ int send_files(Config* config) {
     unsigned long long chunk_bytes = 0;
     for (int i = 0; i < current_chunk->element_count; i++) {
       chunk_bytes += current_chunk->items[i]->data->size;
+      total_files++;
       if (manifest) {
         const char* p = current_chunk->items[i]->path;
         if (*p == '/')
           p++;
-        array_list_add(manifest, str_dup(p));
+        char* manifest_entry = str_dup(p);
+        if (!manifest_entry) {
+          log_message(LOG_LEVEL_ERROR, "Failed to allocate manifest entry");
+          chunk_destroy(current_chunk);
+          array_list_delete(manifest);
+          directory_scanner_destroy(scanner);
+          client_disconnect(client);
+          client_delete(client);
+          return 1;
+        }
+        array_list_add(manifest, manifest_entry);
       }
     }
     if (!config->use_sendfile) {
@@ -470,65 +598,41 @@ int send_files(Config* config) {
     chunk_destroy(current_chunk);
   }
   if (config->use_delete) {
-    if (!send_status(client->file_descriptor, STATUS_MANIFEST)) {
+    if (send_delete_manifest(client->file_descriptor, manifest) != 0) {
       array_list_delete(manifest);
       goto send_fail;
     }
-    if (!send_int(client->file_descriptor, manifest->size)) {
-      array_list_delete(manifest);
-      goto send_fail;
-    }
-    for (int i = 0; i < manifest->size; i++) {
-      if (!send_str(client->file_descriptor, (char*)manifest->items[i])) {
-        array_list_delete(manifest);
-        goto send_fail;
-      }
-    }
     array_list_delete(manifest);
   }
   if (!send_status(client->file_descriptor, STATUS_FINISHED))
     goto send_fail;
   Status s;
   int ok = receive_status(client->file_descriptor, &s) && s == STATUS_OK;
+  double elapsed_total = difftime(time(NULL), start);
   if (config->show_progress) {
-    double elapsed = difftime(time(NULL), start);
-    double rate = elapsed > 0 ? total_bytes / (1048576.0 * elapsed) : 0;
+    double rate = elapsed_total > 0 ? total_bytes / (1048576.0 * elapsed_total) : 0;
     fprintf(stderr, "\rSent %.1f MB  (%.1f MB/s)  Done.\n", total_bytes / 1048576.0, rate);
   }
+  if (config->stats) {
+    double rate = elapsed_total > 0 ? total_bytes / (1048576.0 * elapsed_total) : 0;
+    fprintf(stderr, "Stats: %d files, %.1f MB, %.1f MB/s\n", total_files, total_bytes / 1048576.0,
+            rate);
+  }
   directory_scanner_destroy(scanner);
   client_disconnect(client);
   client_delete(client);
-  return ok ? 0 : -1;
+  return ok ? 0 : 1;
 
 send_fail:
   directory_scanner_destroy(scanner);
   client_disconnect(client);
   client_delete(client);
-  return -1;
+  return 1;
 }
 
 int send_files_multithreaded(Config* config) {
-  if (config->dry_run) {
-    DirectoryScanner* scanner = directory_scanner_create(
-        config->send_directory, config->use_metadata, config->chunk_size, config->exclude_patterns,
-        config->exclude_count, config->include_patterns, config->include_count, config->max_size,
-        config->min_size, config->max_depth);
-    Chunk* chunk;
-    int file_count = 0;
-    unsigned long long total_bytes = 0;
-    printf("Dry run: files to be transferred\n");
-    while ((chunk = directory_scanner_next(scanner)) != NULL) {
-      for (int i = 0; i < chunk->element_count; i++) {
-        printf("  %s (%zu bytes)\n", chunk->items[i]->path, chunk->items[i]->data->size);
-        total_bytes += chunk->items[i]->data->size;
-        file_count++;
-      }
-      chunk_destroy(chunk);
-    }
-    directory_scanner_destroy(scanner);
-    printf("Total: %d files, %.1f MB\n", file_count, total_bytes / 1048576.0);
-    return 0;
-  }
+  if (config->dry_run)
+    return send_dry_run_manifest(config);
 
   long pages = sysconf(_SC_AVPHYS_PAGES);
   long page_size = sysconf(_SC_PAGE_SIZE);
@@ -561,19 +665,59 @@ int send_files_multithreaded(Config* config) {
     context->manifest = array_list_create(free);
 
   thrd_t scanner, loader, sender;
-  if (thrd_create(&scanner, scan_directory_multithreaded, context) != thrd_success ||
-      thrd_create(&loader, load_files_multithreaded, context) != thrd_success ||
-      thrd_create(&sender, send_chunks_multithreaded, context) != thrd_success) {
+  bool scanner_created = false;
+  bool loader_created = false;
+  bool sender_created = false;
+
+  scanner_created = (thrd_create(&scanner, scan_directory_multithreaded, context) == thrd_success);
+  if (scanner_created)
+    loader_created = (thrd_create(&loader, load_files_multithreaded, context) == thrd_success);
+  if (scanner_created && loader_created)
+    sender_created = (thrd_create(&sender, send_chunks_multithreaded, context) == thrd_success);
+
+  if (!scanner_created || !loader_created || !sender_created) {
     perror("Error creating threads.\n");
+    context->cancelled = true;
+    context->scanner_done = true;
+    context->loader_done = true;
+    context->sender_done = true;
+    cnd_broadcast(&context->condition_not_full_scanner);
+    cnd_broadcast(&context->condition_not_empty_scanner);
+    cnd_broadcast(&context->condition_not_full_loader);
+    cnd_broadcast(&context->condition_not_empty_loader);
+    if (sender_created)
+      thrd_join(sender, NULL);
+    if (loader_created)
+      thrd_join(loader, NULL);
+    if (scanner_created)
+      thrd_join(scanner, NULL);
     pipeline_context_sender_destroy(context);
     return 1;
   }
 
+  thrd_t progress;
+  bool progress_created = false;
+  if (config->show_progress) {
+    progress_created = (thrd_create(&progress, progress_thread_fn, context) == thrd_success);
+    if (!progress_created) {
+      perror("Error creating progress thread.\n");
+      /* Non-fatal; continue without progress reporting */
+    }
+  }
+
   int sender_result;
   thrd_join(scanner, NULL);
   thrd_join(loader, NULL);
   thrd_join(sender, &sender_result);
 
-  pipeline_context_sender_destroy(context);
-  return sender_result == thrd_success ? 0 : -1;
+  if (progress_created) {
+    /* Signal progress thread to exit if it hasn't already */
+    mtx_lock(&context->mutex_progress);
+    context->sender_done = true;
+    mtx_unlock(&context->mutex_progress);
+    thrd_join(progress, NULL);
+  }
+
+  pipeline_context_sender_destroy(context);
+  return sender_result == thrd_success ? 0 : 1;
 }

src/client/scanner.c

@@ -27,10 +27,14 @@ static void dir_entry_destroy(void* item) {
 
 static DirEntry* dir_entry_create(const char* path, int depth) {
   DirEntry* de = malloc(sizeof(DirEntry));
-  if (de) {
+  if (!de)
+    return NULL;
   de->path = str_dup(path);
-    de->depth = depth;
+  if (!de->path) {
+    free(de);
+    return NULL;
   }
+  de->depth = depth;
   return de;
 }
 
@@ -38,7 +42,9 @@ DirectoryScanner* directory_scanner_create(const char* root_directory, bool use_
                                            unsigned long long chunk_size, char** exclude_patterns,
                                            int exclude_count, char** include_patterns,
                                            int include_count, unsigned long long max_size,
-                                           unsigned long long min_size, int max_depth) {
+                                           unsigned long long min_size, int max_depth,
+                                           bool follow_symlinks, bool copy_links, bool safe_links,
+                                           bool copy_unsafe_links) {
   DirectoryScanner* scanner = malloc(sizeof(DirectoryScanner));
   if (scanner == NULL)
     return NULL;
@@ -55,7 +61,22 @@ DirectoryScanner* directory_scanner_create(const char* root_directory, bool use_
   scanner->min_size = min_size;
   scanner->max_depth = max_depth;
   scanner->current_depth = 0;
-  queue_enqueue(scanner->directories, dir_entry_create(root_directory, 0));
+  scanner->follow_symlinks = follow_symlinks;
+  scanner->copy_links = copy_links;
+  scanner->safe_links = safe_links;
+  scanner->copy_unsafe_links = copy_unsafe_links;
+  DirEntry* root = dir_entry_create(root_directory, 0);
+  if (!root) {
+    queue_destroy(scanner->directories);
+    free(scanner);
+    return NULL;
+  }
+  if (!queue_enqueue(scanner->directories, root)) {
+    dir_entry_destroy(root);
+    queue_destroy(scanner->directories);
+    free(scanner);
+    return NULL;
+  }
   return scanner;
 }
 
@@ -131,10 +152,58 @@ Chunk* directory_scanner_next(DirectoryScanner* scanner) {
 
     char* cur_path = path_cat(scanner->current_path, entry->d_name);
     struct stat stats;
+    struct stat lstats;
+    bool is_symlink = false;
+    if (lstat(cur_path, &lstats) != 0) {
+      free(cur_path);
+      continue;
+    }
+    is_symlink = S_ISLNK(lstats.st_mode);
+
+    if (is_symlink && !scanner->follow_symlinks && !scanner->copy_links && !scanner->safe_links &&
+        !scanner->copy_unsafe_links) {
+      free(cur_path);
+      continue;
+    }
+
+    if (is_symlink && scanner->safe_links) {
+      char link_target[4096];
+      ssize_t len = readlink(cur_path, link_target, sizeof(link_target) - 1);
+      if (len < 0) {
+        free(cur_path);
+        continue;
+      }
+      link_target[len] = '\0';
+      if (link_target[0] == '/') {
+        free(cur_path);
+        continue;
+      }
+    }
+
+    if (is_symlink && scanner->copy_unsafe_links && !scanner->copy_links) {
+      char link_target[4096];
+      ssize_t len = readlink(cur_path, link_target, sizeof(link_target) - 1);
+      if (len < 0) {
+        free(cur_path);
+        continue;
+      }
+      link_target[len] = '\0';
+      bool unsafe = (link_target[0] == '/');
+      if (!unsafe) {
+        free(cur_path);
+        continue;
+      }
+    }
+
+    bool use_lstat = is_symlink && scanner->follow_symlinks && !scanner->copy_links;
+    if (use_lstat) {
+      stats = lstats;
+    } else {
       if (stat(cur_path, &stats) != 0) {
         free(cur_path);
         continue;
       }
+    }
 
     if (S_ISDIR(stats.st_mode)) {
       int next_depth = scanner->current_depth + 1;
@@ -218,6 +287,10 @@ typedef struct {
   unsigned long long max_size;
   unsigned long long min_size;
   int max_depth;
+  bool follow_symlinks;
+  bool copy_links;
+  bool safe_links;
+  bool copy_unsafe_links;
 } ParallelWorkerArg;
 
 static int parallel_worker_thread(void* arg) {
@@ -225,7 +298,8 @@ static int parallel_worker_thread(void* arg) {
   for (int i = 0; i < wa->dir_count; i++) {
     DirectoryScanner* ds = directory_scanner_create(
         wa->dirs[i], wa->use_metadata, wa->chunk_size, wa->exclude_patterns, wa->exclude_count,
-        wa->include_patterns, wa->include_count, wa->max_size, wa->min_size, wa->max_depth);
+        wa->include_patterns, wa->include_count, wa->max_size, wa->min_size, wa->max_depth,
+        wa->follow_symlinks, wa->copy_links, wa->safe_links, wa->copy_unsafe_links);
     Chunk* chunk;
     while ((chunk = directory_scanner_next(ds)) != NULL) {
       queue_enqueue_multithreaded(wa->ps->result_queue, chunk, &wa->ps->result_mutex,
@@ -252,7 +326,8 @@ ParallelScanner* parallel_scanner_create(char* root_directory, bool use_metadata
                                          int exclude_count, char** include_patterns,
                                          int include_count, unsigned long long max_size,
                                          unsigned long long min_size, int max_depth,
-                                         int num_threads) {
+                                         int num_threads, bool follow_symlinks, bool copy_links,
+                                         bool safe_links, bool copy_unsafe_links) {
   ParallelScanner* ps = calloc(1, sizeof(ParallelScanner));
   if (!ps)
     return NULL;
@@ -261,9 +336,28 @@ ParallelScanner* parallel_scanner_create(char* root_directory, bool use_metadata
     free(ps);
     return NULL;
   }
-  if (mtx_init(&ps->result_mutex, mtx_plain) != thrd_success ||
-      cnd_init(&ps->result_not_empty) != thrd_success ||
-      cnd_init(&ps->result_not_full) != thrd_success) {
+  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);
     free(ps);
     return NULL;
@@ -285,11 +379,62 @@ ParallelScanner* parallel_scanner_create(char* root_directory, bool use_metadata
     char* cur_path = path_cat(root_directory, entry->d_name);
     if (!cur_path)
       continue;
+    struct stat lstats;
+    if (lstat(cur_path, &lstats) != 0) {
+      free(cur_path);
+      continue;
+    }
+    bool is_symlink = S_ISLNK(lstats.st_mode);
+
+    // Skip symlinks unless the user explicitly enabled following/copying them.
+    if (is_symlink && !follow_symlinks && !copy_links && !safe_links && !copy_unsafe_links) {
+      free(cur_path);
+      continue;
+    }
+
+    // --safe-links: reject symlinks pointing outside the source tree.
+    if (is_symlink && safe_links) {
+      char link_target[4096];
+      ssize_t len = readlink(cur_path, link_target, sizeof(link_target) - 1);
+      if (len < 0) {
+        free(cur_path);
+        continue;
+      }
+      link_target[len] = 0;
+      if (link_target[0] == '/') {
+        free(cur_path);
+        continue;
+      }
+    }
+
+    // --copy-unsafe-links (without --copy-links): only copy absolute symlinks.
+    if (is_symlink && copy_unsafe_links && !copy_links) {
+      char link_target[4096];
+      ssize_t len = readlink(cur_path, link_target, sizeof(link_target) - 1);
+      if (len < 0) {
+        free(cur_path);
+        continue;
+      }
+      link_target[len] = 0;
+      bool unsafe = (link_target[0] == '/');
+      if (!unsafe) {
+        free(cur_path);
+        continue;
+      }
+    }
+
+    // Determine whether to use lstat or stat results for the entry.
     struct stat st;
+    bool use_lstat_res = is_symlink && follow_symlinks && !copy_links;
+    if (use_lstat_res) {
+      st = lstats;
+    } else {
       if (stat(cur_path, &st) != 0) {
         free(cur_path);
         continue;
       }
+    }
+
     if (S_ISDIR(st.st_mode)) {
       array_list_add(subdirs, cur_path);
     } else {
@@ -411,6 +556,10 @@ ParallelScanner* parallel_scanner_create(char* root_directory, bool use_metadata
       wa->max_size = max_size;
       wa->min_size = min_size;
       wa->max_depth = max_depth;
+      wa->follow_symlinks = follow_symlinks;
+      wa->copy_links = copy_links;
+      wa->safe_links = safe_links;
+      wa->copy_unsafe_links = copy_unsafe_links;
       start += count;
       if (thrd_create(&ps->threads[t], parallel_worker_thread, wa) != thrd_success) {
         for (int j = 0; j < count; j++)
@@ -446,6 +595,7 @@ void parallel_scanner_destroy(ParallelScanner* ps) {
     return;
   ps->done = true;
   cnd_signal(&ps->result_not_empty);
+  cnd_broadcast(&ps->result_not_full);
   for (int i = 0; i < ps->num_threads; i++)
     thrd_join(ps->threads[i], NULL);
   free(ps->threads);

src/client/scanner.h

@@ -21,6 +21,10 @@ typedef struct {
   unsigned long long min_size;
   int max_depth;
   int current_depth;
+  bool follow_symlinks;
+  bool copy_links;
+  bool safe_links;
+  bool copy_unsafe_links;
 } DirectoryScanner;
 
 typedef struct {
@@ -39,7 +43,9 @@ DirectoryScanner* directory_scanner_create(const char* root_directory, bool use_
                                            unsigned long long chunk_size, char** exclude_patterns,
                                            int exclude_count, char** include_patterns,
                                            int include_count, unsigned long long max_size,
-                                           unsigned long long min_size, int max_depth);
+                                           unsigned long long min_size, int max_depth,
+                                           bool follow_symlinks, bool copy_links, bool safe_links,
+                                           bool copy_unsafe_links);
 Chunk* directory_scanner_next(DirectoryScanner* scanner);
 void directory_scanner_destroy(DirectoryScanner* scanner);
 
@@ -48,7 +54,8 @@ ParallelScanner* parallel_scanner_create(char* root_directory, bool use_metadata
                                          int exclude_count, char** include_patterns,
                                          int include_count, unsigned long long max_size,
                                          unsigned long long min_size, int max_depth,
-                                         int num_threads);
+                                         int num_threads, bool follow_symlinks, bool copy_links,
+                                         bool safe_links, bool copy_unsafe_links);
 Chunk* parallel_scanner_next(ParallelScanner* scanner);
 void parallel_scanner_destroy(ParallelScanner* scanner);
 

src/client/usage.c

@@ -0,0 +1,73 @@
+#include "stdio.h"
+#include <delta.h>
+#include <chunk.h>
+
+static __attribute__((unused)) void print_usage() {
+  printf("Usage:\n");
+  printf("  fastsync [options] <source> <destination>\n");
+  printf("  fastsync [options] --source-dir <src> --dest-dir <dst>\n");
+  printf("\n");
+  printf("Destination formats:\n");
+  printf("  user@host:/path     SSH transport (rsync-style)\n");
+  printf("  host:/path          SSH transport (current user)\n");
+  printf("  /local/path         TCP transport (requires server on localhost:8080)\n");
+  printf("\n");
+  printf("Options:\n");
+  printf("  -c [level]          Enable compression (level 1-22, default 5)\n");
+  printf("  -z [level]          Alias for -c\n");
+  printf("  -a, --archive       Archive mode (-c -m -M)\n");
+  printf("  -n, --dry-run       Show what would be transferred\n");
+  printf("  -p <port>           SSH port (default: 22)\n");
+  printf("  --progress          Show transfer progress\n");
+  printf("  --delete            Delete files on receiver not in source\n");
+  printf("  --exclude <pattern> Exclude files matching pattern\n");
+  printf("  --include <pattern> Only include files matching pattern\n");
+  printf("  --exclude-from <file> Read exclude patterns from file\n");
+  printf("  --include-from <file> Read include patterns from file\n");
+  printf("  --max-size <n>      Skip files larger than n bytes\n");
+  printf("  --min-size <n>      Skip files smaller than n bytes\n");
+  printf("  --incremental       Skip files unchanged since last transfer\n");
+  printf("  --delta             Delta transfer for changed files (requires --incremental)\n");
+  printf("  --delta-block <n>   Delta block size in bytes (default: %d)\n",
+         DELTA_BLOCK_SIZE_DEFAULT);
+  printf("  --delta-max <n>     Max file size for delta transfer (default: %llu)\n",
+         DELTA_MAX_FILE_SIZE);
+  printf("  -m                  Enable multithreading\n");
+  printf("  -s                  Enable chunk serialization\n");
+  printf("  -f                  Enable sendfile (TCP only, not with -c or -s)\n");
+  printf("  -v, --verbose       Enable debug logging\n");
+  printf("  -M, --preserve      Preserve file metadata\n");
+  printf("  --chunk-size <n>    Chunk size in bytes (default: %d)\n", DEFAULT_CHUNK_SIZE);
+  printf("  --source-dir <path> Source directory\n");
+  printf("  --dest-dir <path>   Destination directory\n");
+  printf("  --save-to-disk      Write received files to disk\n");
+  printf("  --server-host <ip>  Server IP address (default: 127.0.0.1)\n");
+  printf("  --server-port <n>   Server port (default: 8080)\n");
+  printf("  --bwlimit <KB/s>    Bandwidth limit in kilobytes per second\n");
+  printf("  --tls               Enable TLS encryption\n");
+  printf("  --cert <path>       TLS certificate file (PEM)\n");
+  printf("  --key <path>        TLS private key file (PEM)\n");
+  printf("  --ca <path>         TLS CA certificate file (PEM)\n");
+  printf("  --timeout <sec>     I/O timeout in seconds (default: 30)\n");
+  printf("  -T <sec>            Alias for --timeout\n");
+  printf("  --contimeout <sec>  Connection timeout in seconds (default: 10)\n");
+  printf("  --backup            Backup existing files before overwriting\n");
+  printf("  --backup-dir <dir>  Directory for backups (requires --backup)\n");
+  printf("  --suffix <str>      Backup suffix (default: ~)\n");
+  printf("  --stats             Print transfer statistics at end\n");
+  printf("  --max-depth <n>     Maximum directory depth (0=unlimited)\n");
+  printf("  --log-file <path>   Write log messages to file\n");
+  printf("  --partial           Keep partial files on interrupted transfer\n");
+  printf("  --partial-dir <dir> Directory for partial files\n");
+  printf("  --fastsync-server-path <path>\n");
+  printf("                      Path to fastsync-server on remote (default: fastsync-server)\n");
+  printf("  -l, --links         Copy symlinks as symlinks\n");
+  printf("  --copy-links        Transform symlinks into referent files\n");
+  printf("  --safe-links        Skip symlinks that point outside transfer tree\n");
+  printf("  --copy-unsafe-links  Only transform unsafe symlinks into referent files\n");
+  printf("  -S, --sparse        Handle sparse files efficiently\n");
+  printf("  --inplace           Update files in-place (no temp+rename)\n");
+  printf("  --compress-level <n>    Compression level (default: 5)\n");
+  printf("  --help              Show this help\n");
+  printf("  -V, --version       Show version\n");
+}

src/server/server.c

@@ -112,6 +112,7 @@ int receive_files(Config* config, int fd) {
 }
 
 void handler(int file_descriptor) {
+  SSL* ssl = io_get_ssl();
   Config* config = config_receive(file_descriptor);
   if (config == NULL) {
     log_message(LOG_LEVEL_ERROR, "Failed to receive config");
@@ -125,7 +126,8 @@ void handler(int file_descriptor) {
       close(file_descriptor);
       return;
     }
-    PipelineContextReceiver* context = pipeline_context_receiver_create(config, q, file_descriptor);
+    PipelineContextReceiver* context =
+        pipeline_context_receiver_create(config, q, file_descriptor, ssl);
     if (context == NULL) {
       queue_destroy(q);
       config_delete(config);
@@ -133,22 +135,41 @@ void handler(int file_descriptor) {
       return;
     }
     thrd_t receiver, writer;
-    if (thrd_create(&receiver, receive_thread, context) != thrd_success ||
-        thrd_create(&writer, write_thread, context) != thrd_success) {
+    bool receiver_created = false;
+    bool writer_created = false;
+    receiver_created = (thrd_create(&receiver, receive_thread, context) == thrd_success);
+    if (receiver_created)
+      writer_created = (thrd_create(&writer, write_thread, context) == thrd_success);
+    if (!receiver_created || !writer_created) {
       perror("Error creating Threads");
-      pipeline_context_receiver_destroy(context);
+      if (receiver_created) {
+        mtx_lock(&context->mutex);
+        context->cancelled = true;
+        cnd_broadcast(&context->condition_not_full);
+        cnd_broadcast(&context->condition_not_empty);
+        mtx_unlock(&context->mutex);
         close(file_descriptor);
+        thrd_join(receiver, NULL);
+      } else {
+        close(file_descriptor);
+      }
+      if (writer_created)
+        thrd_join(writer, NULL);
+      pipeline_context_receiver_destroy(context);
       return;
     }
     thrd_join(receiver, NULL);
     thrd_join(writer, NULL);
     send_status(file_descriptor, STATUS_OK);
     pipeline_context_receiver_destroy(context);
-  } else
+  } else {
     receive_files(config, file_descriptor);
+    config_delete(config);
+  }
   close(file_descriptor);
 }
 
+#ifndef FASTSYNC_SERVER_AS_LIB
 static Server* g_server = NULL;
 
 static void cleanup(int sig) {
@@ -244,3 +265,4 @@ int main(int argc, char* argv[]) {
   }
   return 0;
 }
+#endif /* !FASTSYNC_SERVER_AS_LIB */

src/shared/chunk.c

@@ -12,6 +12,9 @@
 #include "metadata.h"
 #include "protocol.h"
 
+/* Maximum individual file data size within a chunk (64 MB) */
+#define MAX_FILE_DATA_SIZE (64ULL * 1024 * 1024)
+
 Chunk* chunk_create(File** items, int element_count) {
   Chunk* chunk = (Chunk*)malloc(sizeof(Chunk));
   if (chunk == NULL) {
@@ -157,6 +160,14 @@ Chunk* chunk_deserialize(Data* data, bool use_metadata) {
       return NULL;
     }
 
+    // Reject individual file data larger than the maximum allowed size.
+    if (file_data_size > MAX_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);
+      array_list_delete(files);
+      return NULL;
+    }
+
     void* file_data = malloc(file_data_size);
     if (file_data == NULL) {
       perror("Could not allocate memory for file data");
@@ -210,6 +221,15 @@ Chunk* receive_chunk_data(int fd, const Config* config) {
       return NULL;
     }
   }
+
+  // Reject chunks larger than the maximum allowed size to prevent OOM.
+  if (data_to_process->size > MAX_CHUNK_SIZE) {
+    log_message(LOG_LEVEL_ERROR, "Chunk size %zu exceeds maximum %llu", data_to_process->size,
+                (unsigned long long)MAX_CHUNK_SIZE);
+    data_destroy(data_to_process);
+    return NULL;
+  }
+
   Chunk* chunk = chunk_deserialize(data_to_process, config->use_metadata);
   data_destroy(data_to_process);
   if (chunk == NULL)

src/shared/compression.c

@@ -1,12 +1,13 @@
 #include "compression.h"
 #include "data.h"
 #include "log.h"
-#include "stdlib.h"
-#include "string.h"
+#include <stdlib.h>
+#include <string.h>
 #include <strings.h>
-#include "zstd.h"
+#include <zstd.h>
 
 #define INITIAL_DECOMPRESS_BUF_SIZE (1024 * 1024)
+#define MAX_DECOMPRESSED_SIZE (100ULL * 1024 * 1024) /* 100 MB hard ceiling */
 
 static const char* SKIP_COMPRESSION_EXTENSIONS[] = {".jpg", ".jpeg", ".png", ".gif", ".mp4", ".mkv",
                                                     ".zip", ".gz",   ".xz",  ".zst", NULL};
@@ -84,6 +85,13 @@ Data* data_decompress(Data* compressed_data) {
     dst_size = compressed_data->size * 3;
     if (dst_size < INITIAL_DECOMPRESS_BUF_SIZE)
       dst_size = INITIAL_DECOMPRESS_BUF_SIZE;
+    if (dst_size > MAX_DECOMPRESSED_SIZE)
+      dst_size = MAX_DECOMPRESSED_SIZE;
+  }
+  if (dst_size > MAX_DECOMPRESSED_SIZE) {
+    log_message(LOG_LEVEL_ERROR, "Declared decompressed size exceeds %llu bytes",
+                (unsigned long long)MAX_DECOMPRESSED_SIZE);
+    return NULL;
   }
 
   ZSTD_DCtx* dctx = ZSTD_createDCtx();
@@ -113,7 +121,16 @@ Data* data_decompress(Data* compressed_data) {
       return NULL;
     }
     if (ret > 0 && output.pos == output.size) {
+      if (buf_size >= MAX_DECOMPRESSED_SIZE) {
+        log_message(LOG_LEVEL_ERROR, "Decompressed data exceeds %llu bytes",
+                    (unsigned long long)MAX_DECOMPRESSED_SIZE);
+        ZSTD_freeDCtx(dctx);
+        data_destroy(uncompressed_data);
+        return NULL;
+      }
       buf_size *= 2;
+      if (buf_size > MAX_DECOMPRESSED_SIZE)
+        buf_size = MAX_DECOMPRESSED_SIZE;
       void* new_data = realloc(uncompressed_data->data, buf_size);
       if (!new_data) {
         log_message(LOG_LEVEL_ERROR, "Failed to grow decompression buffer");

src/shared/config.c

@@ -8,28 +8,21 @@
 #include <stdlib.h>
 #include <string.h>
 
-Config* config_create(char* version, char* send_directory, char* receive_directory,
-                      bool save_to_disk, bool use_multithreading, bool use_chunk_serialization,
-                      bool use_compression, bool use_metadata, int compression_level,
-                      bool use_sendfile, unsigned long long chunk_size) {
-
-  Config* config = malloc(sizeof(Config));
-  if (!config)
-    return NULL;
-  config->version = version;
-  config->send_directory = send_directory;
-  config->receive_root_directory = receive_directory;
-  config->save_to_disk = save_to_disk;
-  config->use_multithreading = use_multithreading;
-  config->use_chunk_serialization = use_chunk_serialization;
-  config->use_compression = use_compression;
-  config->use_metadata = use_metadata;
+static void config_set_defaults(Config* config) {
+  config->version = str_dup(PROTOCOL_VERSION);
+  config->send_directory = NULL;
+  config->receive_root_directory = NULL;
+  config->save_to_disk = false;
+  config->use_multithreading = false;
+  config->use_chunk_serialization = false;
+  config->use_compression = false;
+  config->use_metadata = false;
   config->show_progress = false;
   config->dry_run = false;
   config->use_delete = false;
-  config->compression_level = compression_level;
-  config->use_sendfile = use_sendfile;
-  config->chunk_size = chunk_size > 0 ? chunk_size : DEFAULT_CHUNK_SIZE;
+  config->compression_level = 5;
+  config->use_sendfile = false;
+  config->chunk_size = DEFAULT_CHUNK_SIZE;
   config->ssh_port = 22;
   config->transport = TRANSPORT_TCP;
   config->ssh_destination = NULL;
@@ -52,13 +45,27 @@ Config* config_create(char* version, char* send_directory, char* receive_directo
   config->server_port = 8080;
   config->timeout = 30;
   config->contimeout = 10;
-  config->quiet = false;
   config->backup = false;
   config->backup_dir = NULL;
   config->stats = false;
   config->max_depth = 0;
   config->log_file = NULL;
-  config->queue_size = 100;
+  config->follow_symlinks = false;
+  config->partial = false;
+  config->copy_links = false;
+  config->safe_links = false;
+  config->copy_unsafe_links = false;
+  config->preserve_sparse = false;
+  config->inplace = false;
+  config->partial_dir = NULL;
+  config->suffix = NULL;
+}
+
+Config* config_create(void) {
+  Config* config = malloc(sizeof(Config));
+  if (!config)
+    return NULL;
+  config_set_defaults(config);
   return config;
 }
 
@@ -89,6 +96,8 @@ void config_parse_ssh_dest(Config* config) {
 }
 
 void config_delete(Config* config) {
+  if (config == NULL)
+    return;
   free(config->version);
   free(config->send_directory);
   free(config->receive_root_directory);
@@ -105,9 +114,22 @@ void config_delete(Config* config) {
   free(config->tls_ca);
   free(config->backup_dir);
   free(config->server_host);
+  free(config->partial_dir);
+  free(config->suffix);
   free(config);
 }
 
+/* Wire format order (must match config_receive and be updated when PROTOCOL_VERSION bumps):
+ * version, send_directory, receive_root_directory, save_to_disk, use_multithreading,
+ * use_chunk_serialization, use_compression, use_metadata, compression_level, chunk_size,
+ * use_sendfile, use_delete, use_incremental, use_delta, delta_block_size, delta_max_file_size,
+ * backup, backup_dir, follow_symlinks, copy_links, safe_links, copy_unsafe_links,
+ * obsolete metadata flags, preserve_sparse, obsolete transfer flags, inplace, obsolete delete
+ * flags, obsolete path options, partial, partial_dir, suffix, obsolete checksum options, status
+ *
+ * Obsolete fields remain as zero/empty compatibility slots. They must be consumed in this order
+ * until the protocol version is intentionally changed.
+ */
 bool config_send(int file_descriptor, const Config* config) {
   if (!send_str(file_descriptor, config->version))
     return false;
@@ -137,7 +159,7 @@ bool config_send(int file_descriptor, const Config* config) {
     return false;
   if (!send_int(file_descriptor, config->use_delta))
     return false;
-  if (!send_int(file_descriptor, (int)config->delta_block_size))
+  if (!send_n_data(file_descriptor, &config->delta_block_size, sizeof(config->delta_block_size)))
     return false;
   if (!send_n_data(file_descriptor, &config->delta_max_file_size, sizeof(unsigned long long)))
     return false;
@@ -145,6 +167,57 @@ bool config_send(int file_descriptor, const Config* config) {
     return false;
   if (!send_str(file_descriptor, config->backup_dir ? config->backup_dir : ""))
     return false;
+  if (!send_int(file_descriptor, config->follow_symlinks))
+    return false;
+  if (!send_int(file_descriptor, config->copy_links))
+    return false;
+  if (!send_int(file_descriptor, config->safe_links))
+    return false;
+  if (!send_int(file_descriptor, config->copy_unsafe_links))
+    return false;
+  if (!send_int(file_descriptor, 0))
+    return false;
+  if (!send_int(file_descriptor, 0))
+    return false;
+  if (!send_int(file_descriptor, 0))
+    return false;
+  if (!send_int(file_descriptor, 0))
+    return false;
+  if (!send_int(file_descriptor, config->preserve_sparse))
+    return false;
+  if (!send_int(file_descriptor, 0))
+    return false;
+  if (!send_int(file_descriptor, config->inplace))
+    return false;
+  if (!send_int(file_descriptor, 0))
+    return false;
+  if (!send_int(file_descriptor, 0))
+    return false;
+  if (!send_int(file_descriptor, 0))
+    return false;
+  if (!send_int(file_descriptor, 0))
+    return false;
+  int obsolete_int = 0;
+  if (!send_n_data(file_descriptor, &obsolete_int, sizeof(obsolete_int)))
+    return false;
+  if (!send_int(file_descriptor, 0))
+    return false;
+  if (!send_int(file_descriptor, 0))
+    return false;
+  if (!send_str(file_descriptor, ""))
+    return false;
+  if (!send_int(file_descriptor, config->partial))
+    return false;
+  if (!send_str(file_descriptor, config->partial_dir ? config->partial_dir : ""))
+    return false;
+  if (!send_str(file_descriptor, config->suffix ? config->suffix : ""))
+    return false;
+  if (!send_int(file_descriptor, 0))
+    return false;
+  if (!send_int(file_descriptor, 0))
+    return false;
+  if (!send_str(file_descriptor, ""))
+    return false;
   Status status;
   if (!receive_status(file_descriptor, &status))
     return false;
@@ -155,13 +228,16 @@ bool config_send(int file_descriptor, const Config* config) {
   return true;
 }
 
+/* Wire format order: see the comment above config_send. */
 Config* config_receive(int file_descriptor) {
   Config* config = (Config*)malloc(sizeof(Config));
   if (config == NULL)
     return NULL;
-  memset(config, 0, sizeof(*config));
+  config_set_defaults(config);
+  free(config->version);
   config->version = receive_str(file_descriptor);
   if (!config->version) {
+    free(config->server_host);
     free(config);
     return NULL;
   }
@@ -169,6 +245,7 @@ Config* config_receive(int file_descriptor) {
     fprintf(stderr, "Protocol version mismatch: client=%s, server=%s\n", config->version,
             PROTOCOL_VERSION);
     free(config->version);
+    free(config->server_host);
     free(config);
     send_status(file_descriptor, STATUS_ERROR);
     return NULL;
@@ -176,6 +253,7 @@ Config* config_receive(int file_descriptor) {
   config->send_directory = receive_str(file_descriptor);
   if (!config->send_directory) {
     free(config->version);
+    free(config->server_host);
     free(config);
     return NULL;
   }
@@ -183,6 +261,7 @@ Config* config_receive(int file_descriptor) {
   if (!config->receive_root_directory) {
     free(config->version);
     free(config->send_directory);
+    free(config->server_host);
     free(config);
     return NULL;
   }
@@ -219,42 +298,80 @@ Config* config_receive(int file_descriptor) {
   if (!receive_int(file_descriptor, &tmp))
     goto error;
   config->use_delta = tmp;
-  if (!receive_int(file_descriptor, &tmp))
+  if (!receive_n_data(file_descriptor, &config->delta_block_size, sizeof(config->delta_block_size)))
     goto error;
-  config->delta_block_size = (uint32_t)tmp;
   if (!receive_n_data(file_descriptor, &config->delta_max_file_size, sizeof(unsigned long long)))
     goto error;
-  config->show_progress = false;
-  config->dry_run = false;
-  config->ssh_port = 22;
-  config->transport = TRANSPORT_TCP;
-  config->ssh_destination = NULL;
-  config->fastsync_server_path = NULL;
-  config->exclude_patterns = NULL;
-  config->exclude_count = 0;
-  config->include_patterns = NULL;
-  config->include_count = 0;
-  config->max_size = 0;
-  config->min_size = 0;
-  config->use_tls = false;
-  config->tls_cert = NULL;
-  config->tls_key = NULL;
-  config->tls_ca = NULL;
-  config->timeout = 30;
-  config->contimeout = 10;
-  config->quiet = false;
-  config->stats = false;
-  config->max_depth = 0;
-  config->log_file = NULL;
-  config->queue_size = 100;
   if (!receive_int(file_descriptor, &tmp))
     goto error;
   config->backup = tmp;
   config->backup_dir = receive_str(file_descriptor);
   if (config->backup_dir == NULL)
     goto error;
-  config->server_host = str_dup("127.0.0.1");
-  config->server_port = 8080;
+  if (!receive_int(file_descriptor, &tmp))
+    goto error;
+  config->follow_symlinks = tmp;
+  if (!receive_int(file_descriptor, &tmp))
+    goto error;
+  config->copy_links = tmp;
+  if (!receive_int(file_descriptor, &tmp))
+    goto error;
+  config->safe_links = tmp;
+  if (!receive_int(file_descriptor, &tmp))
+    goto error;
+  config->copy_unsafe_links = tmp;
+  if (!receive_int(file_descriptor, &tmp))
+    goto error;
+  if (!receive_int(file_descriptor, &tmp))
+    goto error;
+  if (!receive_int(file_descriptor, &tmp))
+    goto error;
+  if (!receive_int(file_descriptor, &tmp))
+    goto error;
+  if (!receive_int(file_descriptor, &tmp))
+    goto error;
+  config->preserve_sparse = tmp;
+  if (!receive_int(file_descriptor, &tmp))
+    goto error;
+  if (!receive_int(file_descriptor, &tmp))
+    goto error;
+  config->inplace = tmp;
+  if (!receive_int(file_descriptor, &tmp))
+    goto error;
+  if (!receive_int(file_descriptor, &tmp))
+    goto error;
+  if (!receive_int(file_descriptor, &tmp))
+    goto error;
+  if (!receive_int(file_descriptor, &tmp))
+    goto error;
+  int obsolete_int = 0;
+  if (!receive_n_data(file_descriptor, &obsolete_int, sizeof(obsolete_int)))
+    goto error;
+  if (!receive_int(file_descriptor, &tmp))
+    goto error;
+  if (!receive_int(file_descriptor, &tmp))
+    goto error;
+  char* obsolete_string = receive_str(file_descriptor);
+  if (obsolete_string == NULL)
+    goto error;
+  free(obsolete_string);
+  if (!receive_int(file_descriptor, &tmp))
+    goto error;
+  config->partial = tmp;
+  config->partial_dir = receive_str(file_descriptor);
+  if (config->partial_dir == NULL)
+    goto error;
+  config->suffix = receive_str(file_descriptor);
+  if (config->suffix == NULL)
+    goto error;
+  if (!receive_int(file_descriptor, &tmp))
+    goto error;
+  if (!receive_int(file_descriptor, &tmp))
+    goto error;
+  obsolete_string = receive_str(file_descriptor);
+  if (obsolete_string == NULL)
+    goto error;
+  free(obsolete_string);
   if (!send_status(file_descriptor, STATUS_OK))
     goto error;
   return config;
@@ -265,6 +382,8 @@ error:
   free(config->receive_root_directory);
   free(config->server_host);
   free(config->backup_dir);
+  free(config->partial_dir);
+  free(config->suffix);
   free(config);
   return NULL;
 }

src/shared/config.h

@@ -44,24 +44,36 @@ typedef struct Config {
   char* tls_ca;
   int timeout;
   int contimeout;
-  bool quiet;
   bool backup;
   char* backup_dir;
   bool stats;
   int max_depth;
   FILE* log_file;
-  int queue_size;
   bool follow_symlinks;
   bool partial;
+
+  // Issue #120: Symlink handling
+  bool copy_links;
+  bool safe_links;
+  bool copy_unsafe_links;
+
+  bool preserve_sparse;
+
+  bool inplace;
+
+  // PR #174: Partial transfer resumption
+  char* partial_dir;
+
+  // PR #178: Backup versioning
+  char* suffix;
+
 } Config;
 
-#define PROTOCOL_VERSION "1.3.0"
+/* This version must be bumped whenever config_send / config_receive wire format changes. */
+#define PROTOCOL_VERSION "2.1.0"
 #define DEFAULT_CHUNK_SIZE (10 * 1024 * 1024)
 
-Config* config_create(char* version, char* send_directory, char* receive_directory,
-                      bool save_to_disk, bool use_multithreading, bool use_chunk_serialization,
-                      bool use_compression, bool use_metadata, int compression_level,
-                      bool use_sendfile, unsigned long long chunk_size);
+Config* config_create(void);
 void config_delete(Config* config);
 bool config_send(int file_descriptor, const Config* config);
 Config* config_receive(int file_descriptor);

src/shared/delta.c

@@ -388,6 +388,10 @@ Delta* delta_deserialize(const Data* data) {
 
     if (type == DELTA_OP_BLOCK_MATCH) {
       if (pos + sizeof(uint32_t) * 3 > data->size) {
+        for (uint32_t k = 0; k < i; k++) {
+          if (delta->instructions[k].type == DELTA_INSTR_LITERAL)
+            free(delta->instructions[k].literal.data);
+        }
         free(delta->instructions);
         free(delta);
         return NULL;
@@ -426,6 +430,11 @@ Delta* delta_deserialize(const Data* data) {
       }
       delta->instructions[i].literal.data = malloc(lit_len);
       if (!delta->instructions[i].literal.data) {
+        log_message(LOG_LEVEL_ERROR, "Failed to allocate %u bytes for literal data", lit_len);
+        for (uint32_t k = 0; k < i; k++) {
+          if (delta->instructions[k].type == DELTA_INSTR_LITERAL)
+            free(delta->instructions[k].literal.data);
+        }
         free(delta->instructions);
         free(delta);
         return NULL;
@@ -449,7 +458,8 @@ Delta* delta_deserialize(const Data* data) {
 
 void* delta_apply(const void* old_data, uint64_t old_size, const Delta* delta,
                   uint32_t block_size) {
-  if (!old_data || !delta)
+  if (!old_data || !delta || (delta->new_file_size > 0 && delta->instructions == NULL) ||
+      (delta->instruction_count > 0 && block_size == 0))
     return NULL;
 
   void* output = malloc((size_t)delta->new_file_size);
@@ -463,10 +473,15 @@ void* delta_apply(const void* old_data, uint64_t old_size, const Delta* delta,
   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 + len > old_size) {
+      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;
       }
@@ -474,6 +489,10 @@ void* delta_apply(const void* old_data, uint64_t old_size, const Delta* delta,
       out_pos += len;
     } else {
       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;
     }

src/shared/file.c

@@ -16,7 +16,6 @@
 #include "config.h"
 #include "data.h"
 #include "file.h"
-#include "log.h"
 #include "metadata.h"
 #include "protocol.h"
 #include "utils.h"
@@ -35,7 +34,8 @@ File* file_create(const char* path) {
     return NULL;
   }
 
-  strcpy(file->path, path);
+  memcpy(file->path, path, path_len);
+  file->path[path_len] = '\0';
   file->data = data_create_reserve(0);
   if (file->data == NULL) {
     free(file->path);
@@ -95,6 +95,9 @@ bool file_load_data(File* file) {
   size_t bytes_read = file_content_to_buffer(file);
   if (bytes_read != file->data->size) {
     log_message(LOG_LEVEL_ERROR, "Did not read expected amount of bytes from file");
+    free(file->data->data);
+    file->data->data = NULL;
+    file->data->size = 0;
     return false;
   }
   return true;
@@ -129,22 +132,29 @@ bool file_send_single_calls(File* file, int file_descriptor, bool use_metadata,
 }
 
 bool file_save_to_disk(const char* root_directory, File* file, const Config* config) {
-  (void)config;
+  bool backup_enabled = config && config->backup;
+  bool inplace = config && config->inplace;
+  bool sparse = config && config->preserve_sparse;
+  const char* backup_suffix = (config && config->suffix) ? config->suffix : "~";
+  const char* backup_dir = (config && config->backup_dir) ? config->backup_dir : NULL;
+  const char* partial_dir = (config && config->partial_dir) ? config->partial_dir : NULL;
+
   if (has_path_traversal(file->path)) {
     log_message(LOG_LEVEL_ERROR, "Path traversal detected in file path: %s", file->path);
     return false;
   }
 
-  // Resolve the destination root to its real path, preventing symlink-based escapes.
-  // If the root does not yet exist, try to create it so realpath can succeed.
-  char* resolved_root = realpath(root_directory, NULL);
+  char* resolved_root = NULL;
+  const char* actual_root =
+      (partial_dir && config && config->partial) ? partial_dir : root_directory;
+  resolved_root = realpath(actual_root, NULL);
   if (resolved_root == NULL) {
-    if (mkdir_r(root_directory)) {
-      resolved_root = realpath(root_directory, NULL);
+    if (mkdir_r(actual_root)) {
+      resolved_root = realpath(actual_root, NULL);
     }
   }
   if (resolved_root == NULL) {
-    log_message(LOG_LEVEL_ERROR, "Failed to resolve destination root: %s", root_directory);
+    log_message(LOG_LEVEL_ERROR, "Failed to resolve destination root: %s", actual_root);
     return false;
   }
 
@@ -154,7 +164,43 @@ bool file_save_to_disk(const char* root_directory, File* file, const Config* con
     return false;
   }
 
-  // Ensure the target directory exists so the parent can be resolved for path safety.
+  if (backup_enabled) {
+    struct stat backup_stat;
+    if (stat(disk_path, &backup_stat) == 0) {
+      char* backup_path = NULL;
+      if (backup_dir) {
+        char* resolved_backup_dir = realpath(backup_dir, NULL);
+        if (!resolved_backup_dir) {
+          mkdir_r(backup_dir);
+          resolved_backup_dir = realpath(backup_dir, NULL);
+        }
+        if (resolved_backup_dir) {
+          backup_path = path_cat(resolved_backup_dir, file->path);
+          free(resolved_backup_dir);
+        }
+      }
+      if (!backup_path) {
+        size_t path_len = strlen(disk_path);
+        size_t suffix_len = strlen(backup_suffix);
+        backup_path = malloc(path_len + suffix_len + 1);
+        if (backup_path) {
+          memcpy(backup_path, disk_path, path_len);
+          memcpy(backup_path + path_len, backup_suffix, suffix_len + 1);
+        }
+      }
+      if (backup_path) {
+        char* backup_dir_path = str_dup(backup_path);
+        if (backup_dir_path) {
+          const char* bdir = dirname(backup_dir_path);
+          mkdir_r(bdir);
+          free(backup_dir_path);
+        }
+        rename(disk_path, backup_path);
+        free(backup_path);
+      }
+    }
+  }
+
   char* dir_dup = str_dup(disk_path);
   if (!dir_dup) {
     free(resolved_root);
@@ -162,7 +208,6 @@ bool file_save_to_disk(const char* root_directory, File* file, const Config* con
     return false;
   }
   char* dir_str = dirname(dir_dup);
-  // Create the directory if needed (no-op if it already exists) so realpath can resolve it.
   if (!mkdir_r(dir_str)) {
     free(dir_dup);
     free(resolved_root);
@@ -178,12 +223,10 @@ bool file_save_to_disk(const char* root_directory, File* file, const Config* con
     return false;
   }
 
-  // Verify that the resolved directory is inside the resolved root.
-  // Both are canonical absolute paths — this prevents symlink-based escapes.
   size_t root_len = strlen(resolved_root);
   if (strncmp(resolved_dir, resolved_root, root_len) != 0 ||
       (resolved_dir[root_len] != '\0' && resolved_dir[root_len] != '/')) {
-    log_message(LOG_LEVEL_ERROR, "Path escape detected: %s is outside %s", disk_path, root_directory);
+    log_message(LOG_LEVEL_ERROR, "Path escape detected: %s is outside %s", disk_path, actual_root);
     free(resolved_dir);
     free(resolved_root);
     free(disk_path);
@@ -192,7 +235,7 @@ bool file_save_to_disk(const char* root_directory, File* file, const Config* con
   free(resolved_dir);
   free(resolved_root);
 
-  bool ok = to_disk(disk_path, file->data->data, file->data->size);
+  bool ok = to_disk(disk_path, file->data->data, file->data->size, inplace, sparse);
   if (ok)
     file_restore_metadata(disk_path, file->metadata);
   free(disk_path);
@@ -477,7 +520,8 @@ File* receive_incremental_check(int fd, const Config* config, bool* skipped) {
   return file;
 }
 
-bool to_disk(const char* path, const void* data, unsigned long long data_size) {
+bool to_disk(const char* path, const void* data, unsigned long long data_size, bool inplace,
+             bool sparse) {
   char* tmp_path = NULL;
   char* directory = NULL;
 
@@ -494,6 +538,39 @@ bool to_disk(const char* path, const void* data, unsigned long long data_size) {
   if (!mkdir_r(directory))
     goto done;
 
+  if (inplace) {
+    FILE* file_pointer = fopen(path, "wb");
+    if (file_pointer == NULL) {
+      perror("Could not open file for inplace write");
+      ok = false;
+      goto done;
+    }
+    if (sparse && data_size > 0) {
+      if (fseek(file_pointer, data_size - 1, SEEK_SET) != 0) {
+        perror("Failed to seek for sparse file");
+        fclose(file_pointer);
+        ok = false;
+        goto done;
+      }
+      if (fwrite("", 1, 1, file_pointer) != 1) {
+        perror("Failed to write sparse file");
+        fclose(file_pointer);
+        ok = false;
+        goto done;
+      }
+      rewind(file_pointer);
+    }
+    if (data_size > 0 && fwrite(data, 1, data_size, file_pointer) != data_size) {
+      perror("Failed to write all data to file");
+      fclose(file_pointer);
+      ok = false;
+      goto done;
+    }
+    fclose(file_pointer);
+    free(directory);
+    return true;
+  }
+
   size_t path_len = strlen(path);
   tmp_path = malloc(path_len + 5);
   if (!tmp_path) {
@@ -509,6 +586,21 @@ bool to_disk(const char* path, const void* data, unsigned long long data_size) {
     ok = false;
     goto done;
   }
+  if (sparse && data_size > 0) {
+    if (fseek(file_pointer, data_size - 1, SEEK_SET) != 0) {
+      perror("Failed to seek for sparse file");
+      fclose(file_pointer);
+      ok = false;
+      goto done;
+    }
+    if (fwrite("", 1, 1, file_pointer) != 1) {
+      perror("Failed to write sparse file");
+      fclose(file_pointer);
+      ok = false;
+      goto done;
+    }
+    rewind(file_pointer);
+  }
   if (fwrite(data, 1, data_size, file_pointer) != data_size) {
     perror("Failed to write all data to temporary file");
     fclose(file_pointer);
@@ -533,13 +625,6 @@ done:
 
 bool file_send_sendfile(File* file, int file_descriptor, bool use_metadata, int compression_level,
                         bool send_path) {
-  // sendfile is incompatible with compression (kernel zero-copy).
-  // If compression is requested, fall back to the regular send path.
-  // NOTE: This is a safety net only — callers must ensure compression_level == 0
-  // before calling file_send_sendfile. The fallback to file_send_single_calls
-  // preserves the send_path contract, but callers should not rely on it for
-  // correctness (the --sendfile flag is validated to be mutually exclusive with
-  // -c/--compress at the CLI layer).
   if (compression_level > 0)
     return file_send_single_calls(file, file_descriptor, use_metadata, compression_level,
                                   send_path);
@@ -565,6 +650,8 @@ bool file_send_sendfile(File* file, int file_descriptor, bool use_metadata, int
   while ((unsigned long long)offset < file_size) {
     ssize_t sent = sendfile(file_descriptor, fd, &offset, file_size - offset);
     if (sent == -1) {
+      if (errno == EAGAIN || errno == EINTR)
+        continue;
       perror("sendfile failed");
       close(fd);
       return false;

src/shared/file.h

@@ -34,7 +34,8 @@ bool file_send_sendfile(File* file, int file_descriptor, bool use_metadata, int
 size_t file_content_to_buffer(File* file);
 FileMetadata* file_metadata_create(const struct stat* stats);
 void file_metadata_destroy(void* metadata);
-bool to_disk(const char* path, const void* data, unsigned long long data_size);
+bool to_disk(const char* path, const void* data, unsigned long long data_size, bool inplace,
+             bool sparse);
 bool file_save_to_disk(const char* root_directory, File* file, const Config* config);
 File* receive_incremental_check(int fd, const Config* config, bool* skipped);
 int receive_manifest(int fd, const Config* config, int* next_status);

src/shared/log.c

@@ -15,28 +15,38 @@ void log_set_file(FILE* fp) {
   log_fp = fp;
 }
 
+static inline void write_message(FILE* dest_io, LogLevel log_level, struct tm t, const char* format,
+                                 va_list args) {
+  fprintf(dest_io, "%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]);
+
+  vfprintf(dest_io, format, args);
+  fprintf(dest_io, "\n");
+}
+
 void log_message(LogLevel log_level, const char* format, ...) {
   if (log_level < current_log_level)
     return;
+  if (log_level < 0 || log_level >= (int)(sizeof(log_level_strings) / sizeof(log_level_strings[0])))
+    return;
   time_t now = time(NULL);
-  const struct tm* t = localtime(&now);
+  struct tm t;
+  if (!localtime_r(&now, &t))
+    return;
 
-  fprintf(stderr, "%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]);
+  FILE* dest_io = stdout;
+  if (log_level == LOG_LEVEL_ERROR) {
+    dest_io = stderr;
+  }
 
   va_list args;
   va_start(args, format);
-  vfprintf(stderr, format, args);
+  write_message(dest_io, log_level, t, format, args);
   va_end(args);
-  fprintf(stderr, "\n");
 
   if (log_fp) {
-    fprintf(log_fp, "%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]);
     va_start(args, format);
-    vfprintf(log_fp, format, args);
+    write_message(log_fp, log_level, t, format, args);
     va_end(args);
-    fprintf(log_fp, "\n");
-    fflush(log_fp);
   }
 }

src/shared/multiprocessing.c

@@ -24,18 +24,51 @@ PipelineContextSender* pipeline_context_sender_create(Config* config, Queue* que
   context->scanner_done = false;
   context->loader_done = false;
   context->manifest = NULL;
-  if (mtx_init(&context->mutex_scanner, mtx_plain) != thrd_success ||
-      cnd_init(&context->condition_not_full_scanner) != thrd_success ||
-      cnd_init(&context->condition_not_empty_scanner) != thrd_success ||
-      mtx_init(&context->mutex_loader, mtx_plain) != thrd_success ||
-      cnd_init(&context->condition_not_full_loader) != thrd_success ||
-      cnd_init(&context->condition_not_empty_loader) != thrd_success) {
+  context->progress_bytes = 0;
+  context->sender_done = false;
+  context->cancelled = false;
+  int init = 0;
+  if (mtx_init(&context->mutex_scanner, mtx_plain) != thrd_success)
+    goto fail;
+  init++;
+  if (cnd_init(&context->condition_not_full_scanner) != thrd_success)
+    goto fail;
+  init++;
+  if (cnd_init(&context->condition_not_empty_scanner) != thrd_success)
+    goto fail;
+  init++;
+  if (mtx_init(&context->mutex_loader, mtx_plain) != thrd_success)
+    goto fail;
+  init++;
+  if (cnd_init(&context->condition_not_full_loader) != thrd_success)
+    goto fail;
+  init++;
+  if (cnd_init(&context->condition_not_empty_loader) != thrd_success)
+    goto fail;
+  init++;
+  if (mtx_init(&context->mutex_progress, mtx_plain) != thrd_success)
+    goto fail;
+  // cppcheck-suppress unreadVariable
+  init++;
+  return context;
+
+fail:
   perror("Error initializing synchronization objects");
+  if (init >= 6)
+    cnd_destroy(&context->condition_not_empty_loader);
+  if (init >= 5)
+    cnd_destroy(&context->condition_not_full_loader);
+  if (init >= 4)
+    mtx_destroy(&context->mutex_loader);
+  if (init >= 3)
+    cnd_destroy(&context->condition_not_empty_scanner);
+  if (init >= 2)
+    cnd_destroy(&context->condition_not_full_scanner);
+  if (init >= 1)
+    mtx_destroy(&context->mutex_scanner);
   free(context);
   return NULL;
 }
-  return context;
-}
 
 void pipeline_context_sender_destroy(PipelineContextSender* context) {
   if (context->manifest) {
@@ -50,27 +83,45 @@ void pipeline_context_sender_destroy(PipelineContextSender* context) {
   mtx_destroy(&context->mutex_loader);
   cnd_destroy(&context->condition_not_full_loader);
   cnd_destroy(&context->condition_not_empty_loader);
+  mtx_destroy(&context->mutex_progress);
   free(context);
 }
 
 PipelineContextReceiver* pipeline_context_receiver_create(Config* config, Queue* queue,
-                                                          int file_descriptor) {
+                                                          int file_descriptor, SSL* ssl) {
   PipelineContextReceiver* context = malloc(sizeof(PipelineContextReceiver));
   if (context == NULL)
     return NULL;
   context->config = config;
   context->queue = queue;
   context->file_descriptor = file_descriptor;
+  context->ssl = ssl;
   context->receiver_done = false;
-  if (mtx_init(&context->mutex, mtx_plain) != thrd_success ||
-      cnd_init(&context->condition_not_full) != thrd_success ||
-      cnd_init(&context->condition_not_empty) != thrd_success) {
+  context->cancelled = false;
+  int init = 0;
+  if (mtx_init(&context->mutex, mtx_plain) != thrd_success)
+    goto fail;
+  init++;
+  if (cnd_init(&context->condition_not_full) != thrd_success)
+    goto fail;
+  init++;
+  if (cnd_init(&context->condition_not_empty) != thrd_success)
+    goto fail;
+  // cppcheck-suppress unreadVariable
+  init++;
+  return context;
+
+fail:
   perror("Error initializing synchronization objects");
+  if (init >= 3)
+    cnd_destroy(&context->condition_not_empty);
+  if (init >= 2)
+    cnd_destroy(&context->condition_not_full);
+  if (init >= 1)
+    mtx_destroy(&context->mutex);
   free(context);
   return NULL;
 }
-  return context;
-}
 
 void pipeline_context_receiver_destroy(PipelineContextReceiver* context) {
   config_delete(context->config);
@@ -81,22 +132,30 @@ void pipeline_context_receiver_destroy(PipelineContextReceiver* context) {
   free(context);
 }
 
-static void receive_chunk_enqueue(int file_descriptor, PipelineContextReceiver* context) {
+static bool receive_chunk_enqueue(int file_descriptor, PipelineContextReceiver* context) {
   Chunk* chunk = receive_chunk_data(file_descriptor, context->config);
   if (chunk == NULL)
-    return;
+    return false;
 
   for (int i = 0; i < chunk->element_count; i++) {
     File* file = chunk->items[i];
     chunk->items[i] = NULL;
-    queue_enqueue_multithreaded(context->queue, file, &context->mutex,
-                                &context->condition_not_empty, &context->condition_not_full);
+    if (!queue_enqueue_multithreaded_cancel(context->queue, file, &context->mutex,
+                                            &context->condition_not_empty,
+                                            &context->condition_not_full, &context->cancelled)) {
+      file_destroy(file);
+      chunk_destroy(chunk);
+      return false;
+    }
   }
   chunk_destroy(chunk);
+  return true;
 }
 
 int receive_thread(void* pipeline_context) {
   PipelineContextReceiver* context = (PipelineContextReceiver*)pipeline_context;
+  if (context->ssl)
+    io_set_ssl(context->ssl);
   mtx_lock(&context->mutex);
   int file_descriptor = context->file_descriptor;
   const Config* config = context->config;
@@ -121,11 +180,16 @@ int receive_thread(void* pipeline_context) {
       if (!skipped) {
         if (file == NULL)
           return thrd_error;
-        queue_enqueue_multithreaded(context->queue, file, &context->mutex,
-                                    &context->condition_not_empty, &context->condition_not_full);
+        if (!queue_enqueue_multithreaded_cancel(
+                context->queue, file, &context->mutex, &context->condition_not_empty,
+                &context->condition_not_full, &context->cancelled)) {
+          file_destroy(file);
+          return thrd_error;
+        }
       }
     } else if (status == STATUS_CHUNK) {
-      receive_chunk_enqueue(file_descriptor, context);
+      if (!receive_chunk_enqueue(file_descriptor, context))
+        return thrd_error;
     } else if (status == STATUS_CHECK_BATCH) {
       int count;
       if (!receive_int(file_descriptor, &count))
@@ -143,7 +207,7 @@ int receive_thread(void* pipeline_context) {
         }
         char* full_path = path_cat(config->receive_root_directory, check_path);
         struct stat st;
-        bool has_old = full_path && stat(full_path, &st) == 0;
+        bool has_old = full_path && lstat(full_path, &st) == 0;
         bool match = has_old && (unsigned long long)st.st_size == check_size &&
                      (long long)st.st_mtime == check_mtime;
         if (match)
@@ -157,10 +221,15 @@ int receive_thread(void* pipeline_context) {
     } else {
       File* file = file_receive(config, file_descriptor);
       if (file) {
-        queue_enqueue_multithreaded(context->queue, file, &context->mutex,
-                                    &context->condition_not_empty, &context->condition_not_full);
+        if (!queue_enqueue_multithreaded_cancel(
+                context->queue, file, &context->mutex, &context->condition_not_empty,
+                &context->condition_not_full, &context->cancelled)) {
+          file_destroy(file);
+          return thrd_error;
+        }
       } else {
         log_message(LOG_LEVEL_ERROR, "Failed to receive file");
+        return thrd_error;
       }
     }
   next:
@@ -180,6 +249,8 @@ int receive_thread(void* pipeline_context) {
 
 int write_thread(void* pipeline_context) {
   PipelineContextReceiver* context = (PipelineContextReceiver*)pipeline_context;
+  if (context->ssl)
+    io_set_ssl(context->ssl);
   mtx_lock(&context->mutex);
   bool save_to_disk = context->config->save_to_disk;
   char* root_directory = str_dup(context->config->receive_root_directory);

src/shared/multiprocessing.h

@@ -6,7 +6,9 @@
 #include "array_list.h"
 #include "config.h"
 #include "file.h"
+#include "protocol.h"
 #include "queue.h"
+#include <openssl/ssl.h>
 
 typedef struct {
   Config* config;
@@ -21,23 +23,29 @@ typedef struct {
   cnd_t condition_not_empty_loader;
   bool loader_done;
   ArrayList* manifest;
+  mtx_t mutex_progress;
+  unsigned long long progress_bytes;
+  bool sender_done;
+  bool cancelled;
 } PipelineContextSender;
 
 typedef struct PipelineContextReceiver {
   Queue* queue;
   Config* config;
   int file_descriptor;
+  SSL* ssl;
   mtx_t mutex;
   cnd_t condition_not_full;
   cnd_t condition_not_empty;
   bool receiver_done;
+  bool cancelled;
 } PipelineContextReceiver;
 
 PipelineContextSender* pipeline_context_sender_create(Config* config, Queue* queue_scanner,
                                                       Queue* queue_loader);
 void pipeline_context_sender_destroy(PipelineContextSender* context);
 PipelineContextReceiver* pipeline_context_receiver_create(Config* config, Queue* queue_receiver,
-                                                          int file_descriptor);
+                                                          int file_descriptor, SSL* ssl);
 void pipeline_context_receiver_destroy(PipelineContextReceiver* context);
 int receive_thread(void* pipeline_context);
 int write_thread(void* pipeline_context);

src/shared/protocol.c

@@ -6,20 +6,22 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <threads.h>
 #include <time.h>
 #include <unistd.h>
 
-#define MAX_DATA_SIZE (100ULL * 1024 * 1024)          /* 100 MB max per data message */
 #define RECEIVE_TIMEOUT_SEC 60                        /* 60 second per-message timeout */
 #define MAX_CONNECTION_MEMORY (1024ULL * 1024 * 1024) /* 1 GB total per connection */
 
 static __thread int io_read_fd = -1;
 static __thread int io_write_fd = -1;
-static SSL* io_ssl;
+static __thread SSL* io_ssl;
 
 static unsigned long long io_bwlimit = 0;
 static long long bw_tokens = 0;
 static struct timespec bw_last_refill = {0, 0};
+static mtx_t bw_mutex;
+static once_flag bw_mutex_once = ONCE_FLAG_INIT;
 
 static __thread unsigned long long total_allocated_bytes = 0;
 
@@ -28,15 +30,24 @@ void io_set_fds(int read_fd, int write_fd) {
   io_write_fd = write_fd;
 }
 
+static void bw_mutex_init(void) {
+  mtx_init(&bw_mutex, mtx_plain);
+}
+
 void io_set_bwlimit(unsigned long long bytes_per_sec) {
+  call_once(&bw_mutex_once, bw_mutex_init);
+  mtx_lock(&bw_mutex);
   io_bwlimit = bytes_per_sec;
   bw_tokens = (long long)io_bwlimit;
   clock_gettime(CLOCK_MONOTONIC, &bw_last_refill);
+  mtx_unlock(&bw_mutex);
 }
 
 static void bw_throttle(size_t bytes_written) {
   if (io_bwlimit == 0)
     return;
+  call_once(&bw_mutex_once, bw_mutex_init);
+  mtx_lock(&bw_mutex);
 
   struct timespec now;
   clock_gettime(CLOCK_MONOTONIC, &now);
@@ -61,12 +72,17 @@ static void bw_throttle(size_t bytes_written) {
     bw_tokens = 0;
     clock_gettime(CLOCK_MONOTONIC, &bw_last_refill);
   }
+  mtx_unlock(&bw_mutex);
 }
 
 void io_set_ssl(SSL* ssl) {
   io_ssl = ssl;
 }
 
+SSL* io_get_ssl(void) {
+  return io_ssl;
+}
+
 static int io_fd(int dir_fd, int file_descriptor) {
   return (dir_fd != -1) ? dir_fd : file_descriptor;
 }
@@ -173,6 +189,8 @@ static const char* status_to_string(Status status) {
 }
 
 bool send_str(int file_descriptor, const char* data) {
+  if (data == NULL)
+    return false;
   size_t size = strlen(data);
   if (!send_n_data(file_descriptor, &size, sizeof(size_t)))
     return false;
@@ -217,9 +235,9 @@ Data* receive_data(int file_descriptor) {
   unsigned long long size = 0;
   if (!receive_n_data(file_descriptor, &size, sizeof(unsigned long long)))
     return NULL;
-  if (size > MAX_DATA_SIZE) {
+  if (size > MAX_DATA_PAYLOAD_SIZE) {
     log_message(LOG_LEVEL_ERROR, "Data size %llu exceeds maximum %llu", size,
-                (unsigned long long)MAX_DATA_SIZE);
+                (unsigned long long)MAX_DATA_PAYLOAD_SIZE);
     return NULL;
   }
   if (total_allocated_bytes + size > MAX_CONNECTION_MEMORY) {

src/shared/protocol.h

@@ -11,6 +11,9 @@
 /* Maximum allowed data payload size for receive_data (100 MB) */
 #define MAX_DATA_PAYLOAD_SIZE (100ULL * 1024 * 1024)
 
+/* Maximum chunk size (64 MB) — prevents unbounded allocation from the wire */
+#define MAX_CHUNK_SIZE (64ULL * 1024 * 1024)
+
 typedef struct ssl_st SSL;
 
 typedef int Status;
@@ -32,6 +35,7 @@ enum NET_STATUS {
 void io_set_fds(int read_fd, int write_fd);
 void io_set_bwlimit(unsigned long long bytes_per_sec);
 void io_set_ssl(SSL* ssl);
+SSL* io_get_ssl(void);
 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);
 

src/shared/queue.c

@@ -103,6 +103,22 @@ bool queue_enqueue_multithreaded(Queue* queue, void* item, mtx_t* mutex, cnd_t*
   return ok;
 }
 
+bool queue_enqueue_multithreaded_cancel(Queue* queue, void* item, mtx_t* mutex,
+                                        cnd_t* condition_not_empty, cnd_t* condition_not_full,
+                                        const bool* cancelled) {
+  mtx_lock(mutex);
+  while (queue_is_full(queue) && (cancelled == NULL || !*cancelled))
+    cnd_wait(condition_not_full, mutex);
+  if (cancelled != NULL && *cancelled) {
+    mtx_unlock(mutex);
+    return false;
+  }
+  bool ok = queue_enqueue(queue, item);
+  cnd_signal(condition_not_empty);
+  mtx_unlock(mutex);
+  return ok;
+}
+
 void* queue_dequeue(Queue* queue) {
   if (queue == NULL || queue_is_empty(queue)) {
     perror("ERROR: Could not dequeue from null or empty queue.");

src/shared/queue.h

@@ -20,6 +20,9 @@ bool queue_is_full(const Queue* queue);
 bool queue_enqueue(Queue* queue, void* item);
 bool queue_enqueue_multithreaded(Queue* queue, void* item, mtx_t* mutex, cnd_t* condition_not_empty,
                                  cnd_t* condition_not_full);
+bool queue_enqueue_multithreaded_cancel(Queue* queue, void* item, mtx_t* mutex,
+                                        cnd_t* condition_not_empty, cnd_t* condition_not_full,
+                                        const bool* cancelled);
 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);

src/shared/transport_ssh.c

@@ -182,7 +182,7 @@ Client* client_connect_ssh(const char* destination, int port, const char* server
     return NULL;
   }
   client->file_descriptor = sv[0];
-  client->address.sin_family = AF_UNIX;
+  client->address.ss_family = AF_UNIX;
   client->address_length = 0;
   client->ssh_child_pid = pid;
   client->ssl = NULL;

src/shared/transport_tcp.c

@@ -3,6 +3,7 @@
 #include "protocol.h"
 #include <arpa/inet.h>
 #include <errno.h>
+#include <netdb.h>
 #include <openssl/ssl.h>
 #include <signal.h>
 #include <stdio.h>
@@ -143,6 +144,10 @@ void tcp_set_timeouts(int timeout_sec, int contimeout_sec) {
     g_contimeout_sec = contimeout_sec;
 }
 
+int tcp_get_contimeout_sec(void) {
+  return g_contimeout_sec;
+}
+
 static void tcp_apply_socket_timeout(int fd) {
   struct timeval tv;
   tv.tv_sec = g_timeout_sec;
@@ -152,19 +157,12 @@ static void tcp_apply_socket_timeout(int fd) {
 }
 
 Client* client_create() {
-  int file_descriptor = socket(AF_INET, SOCK_STREAM, 0);
-  if (file_descriptor < 0) {
-    perror("Could not create Socket!");
-    return NULL;
-  }
-
   Client* client = (Client*)malloc(sizeof(Client));
   if (client == NULL) {
-    close(file_descriptor);
     return NULL;
   }
-  client->file_descriptor = file_descriptor;
-  client->address.sin_family = AF_INET;
+  client->file_descriptor = -1;
+  memset(&client->address, 0, sizeof(client->address));
   client->address_length = sizeof(client->address);
   client->ssh_child_pid = -1;
   client->ssl = NULL;
@@ -173,23 +171,50 @@ Client* client_create() {
 }
 
 bool client_connect(Client* client, char* host, int port) {
-  client->address.sin_port = htons(port);
-  client->address.sin_family = AF_INET;
-  client->address_length = sizeof(client->address);
+  struct addrinfo hints;
+  struct addrinfo* result;
+  memset(&hints, 0, sizeof(hints));
+  hints.ai_family = AF_UNSPEC;
+  hints.ai_socktype = SOCK_STREAM;
+  hints.ai_protocol = IPPROTO_TCP;
 
-  if (inet_pton(AF_INET, host, &client->address.sin_addr) <= 0) {
-    perror("Could not convert host address!");
+  char port_str[16];
+  snprintf(port_str, sizeof(port_str), "%d", port);
+
+  int err = getaddrinfo(host, port_str, &hints, &result);
+  if (err != 0 || result == NULL) {
+    fprintf(stderr, "Could not resolve host: %s (%s)\n", host, gai_strerror(err));
     return false;
   }
 
+  struct addrinfo* rp;
+  bool connected = false;
+  for (rp = result; rp != NULL; rp = rp->ai_next) {
+    if (client->file_descriptor >= 0)
+      close(client->file_descriptor);
+
+    client->file_descriptor = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
+    if (client->file_descriptor < 0)
+      continue;
+
     struct timeval ct;
     ct.tv_sec = g_contimeout_sec;
     ct.tv_usec = 0;
     setsockopt(client->file_descriptor, SOL_SOCKET, SO_RCVTIMEO, &ct, sizeof(ct));
     setsockopt(client->file_descriptor, SOL_SOCKET, SO_SNDTIMEO, &ct, sizeof(ct));
 
-  if (connect(client->file_descriptor, (struct sockaddr*)&client->address, client->address_length) <
-      0) {
+    memcpy(&client->address, rp->ai_addr, rp->ai_addrlen);
+    client->address_length = rp->ai_addrlen;
+
+    if (connect(client->file_descriptor, (struct sockaddr*)&client->address,
+                client->address_length) == 0) {
+      connected = true;
+      break;
+    }
+  }
+  freeaddrinfo(result);
+
+  if (!connected) {
     perror("Could not connect to Server!");
     return false;
   }
@@ -205,7 +230,10 @@ void client_disconnect(Client* client) {
     client->ssl = NULL;
     io_set_ssl(NULL);
   }
+  if (client->file_descriptor >= 0) {
     close(client->file_descriptor);
+    client->file_descriptor = -1;
+  }
   if (client->ssh_child_pid > 0) {
     int status;
     waitpid(client->ssh_child_pid, &status, 0);

src/shared/transport_tcp.h

@@ -15,7 +15,7 @@ typedef struct Server {
 } Server;
 
 typedef struct Client {
-  struct sockaddr_in address;
+  struct sockaddr_storage address;
   unsigned int address_length;
   int file_descriptor;
   pid_t ssh_child_pid;
@@ -33,5 +33,6 @@ bool client_connect(Client* client, char* host, int port);
 void client_disconnect(Client* client);
 void client_delete(Client* client);
 void tcp_set_timeouts(int timeout_sec, int contimeout_sec);
+int tcp_get_contimeout_sec(void);
 
 #endif

src/shared/transport_tls.c

@@ -3,6 +3,7 @@
 #include "protocol.h"
 #include "transport_tcp.h"
 #include <arpa/inet.h>
+#include <netdb.h>
 #include <openssl/err.h>
 #include <openssl/ssl.h>
 #include <signal.h>
@@ -148,13 +149,50 @@ bool server_listen_tls(Server* server, void (*handler)(int file_descriptor)) {
 
 bool client_connect_tls(Client* client, char* host, int port, const char* cert_path,
                         const char* key_path, const char* ca_path) {
-  client->address.sin_port = htons(port);
-  if (inet_pton(AF_INET, host, &client->address.sin_addr) <= 0) {
-    perror("Could not convert host address!");
+  struct addrinfo hints;
+  struct addrinfo* result;
+  memset(&hints, 0, sizeof(hints));
+  hints.ai_family = AF_UNSPEC;
+  hints.ai_socktype = SOCK_STREAM;
+  hints.ai_protocol = IPPROTO_TCP;
+
+  char port_str[16];
+  snprintf(port_str, sizeof(port_str), "%d", port);
+
+  int err = getaddrinfo(host, port_str, &hints, &result);
+  if (err != 0 || result == NULL) {
+    fprintf(stderr, "Could not resolve host: %s (%s)\n", host, gai_strerror(err));
     return false;
   }
-  if (connect(client->file_descriptor, (struct sockaddr*)&client->address, client->address_length) <
-      0) {
+
+  struct addrinfo* rp;
+  bool connected = false;
+  for (rp = result; rp != NULL; rp = rp->ai_next) {
+    if (client->file_descriptor >= 0)
+      close(client->file_descriptor);
+
+    client->file_descriptor = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
+    if (client->file_descriptor < 0)
+      continue;
+
+    struct timeval ct;
+    ct.tv_sec = tcp_get_contimeout_sec();
+    ct.tv_usec = 0;
+    setsockopt(client->file_descriptor, SOL_SOCKET, SO_RCVTIMEO, &ct, sizeof(ct));
+    setsockopt(client->file_descriptor, SOL_SOCKET, SO_SNDTIMEO, &ct, sizeof(ct));
+
+    memcpy(&client->address, rp->ai_addr, rp->ai_addrlen);
+    client->address_length = rp->ai_addrlen;
+
+    if (connect(client->file_descriptor, (struct sockaddr*)&client->address,
+                client->address_length) == 0) {
+      connected = true;
+      break;
+    }
+  }
+  freeaddrinfo(result);
+
+  if (!connected) {
     perror("Could not connect to Server!");
     return false;
   }

src/shared/utils.c

@@ -10,18 +10,21 @@
 #include <unistd.h>
 
 bool mkdir_r(const char* path) {
-  char* path_duplicate = malloc(strlen(path) + 1);
+  size_t path_len = strlen(path);
+  char* path_duplicate = malloc(path_len + 1);
   if (!path_duplicate)
     return false;
-  strcpy(path_duplicate, path);
-  char* path_current = (char*)malloc((strlen(path) + 2) * sizeof(char));
+  memcpy(path_duplicate, path, path_len + 1);
+  size_t capacity = path_len + 2;
+  char* path_current = (char*)malloc(capacity * sizeof(char));
   if (!path_current) {
     free(path_duplicate);
     return false;
   }
   char* path_current_position = path_current;
   if (path[0] == '/') {
-    strcpy(path_current, "/");
+    path_current[0] = '/';
+    path_current[1] = '\0';
     path_current_position += 1;
   } else {
     path_current[0] = '\0';
@@ -31,10 +34,16 @@ bool mkdir_r(const char* path) {
   const char* part = strtok_r(path_duplicate, delimiter, &saveptr);
   bool ok = true;
   while (part != NULL) {
-    strcpy(path_current_position, part);
-    path_current_position += strlen(part) * sizeof(char);
-    strcpy(path_current_position, "/");
-    path_current_position += sizeof(char);
+    size_t part_len = strlen(part);
+    if ((size_t)(path_current_position - path_current) + part_len + 2 > capacity) {
+      ok = false;
+      break;
+    }
+    memcpy(path_current_position, part, part_len);
+    path_current_position += part_len;
+    path_current_position[0] = '/';
+    path_current_position[1] = '\0';
+    path_current_position++;
     struct stat st;
     if (stat(path_current, &st) != 0) {
       if (mkdir(path_current, 0755) != 0) {
@@ -53,15 +62,26 @@ bool mkdir_r(const char* path) {
 char* str_dup(const char* string) {
   if (string == NULL)
     return NULL;
-  char* new_string = (char*)malloc(strlen(string) + 1);
-  strcpy(new_string, string);
+  size_t str_len = strlen(string);
+  char* new_string = (char*)malloc(str_len + 1);
+  if (new_string == NULL)
+    return NULL;
+  memcpy(new_string, string, str_len + 1);
   return new_string;
 }
 
+/* Match a glob pattern against a string. Supported wildcards:
+ *   ?      matches any single character except '/'.
+ *   *      matches any sequence of characters within one path component (no '/').
+ *   **     matches any sequence of characters, including '/' (cross-directory).
+ *   slash-star-star-slash is treated as a cross-directory wildcard when it appears between
+ * literals.
+ */
 bool glob_match(const char* pattern, const char* str) {
   while (*pattern) {
     if (*pattern == '*') {
       if (*(pattern + 1) == '*') {
+        /* globstar: match across directories */
         pattern += 2;
         if (*pattern == '\0')
           return true;
@@ -74,6 +94,7 @@ bool glob_match(const char* pattern, const char* str) {
         }
         return glob_match(pattern, str);
       }
+      /* single *: match within one path component */
       pattern++;
       while (*str && *str != '/') {
         if (glob_match(pattern, str))
@@ -88,6 +109,7 @@ bool glob_match(const char* pattern, const char* str) {
       str++;
     } else {
       if (*pattern != *str) {
+        /* allow literal / ** / rest to match any number of directories */
         if (*pattern == '/' && *(pattern + 1) == '*' && *(pattern + 2) == '*') {
           const char* rest = pattern + 3;
           if (*rest == '/')

tests/integration/test_features.py

@@ -238,7 +238,7 @@ class TestProgress:
         )
         assert result.returncode == 0, f"Exit {result.returncode}: {result.stderr[:100]}"
         output = result.stdout + result.stderr
-        assert len(output) >= 0
+        assert output, "--progress produced no output"
 
 
 class TestBandwidthLimit:

tests/integration/test_ssh.py

@@ -52,9 +52,11 @@ def _check_ssh():
         pass
 
 
+_check_ssh()
+
+
 @pytest.fixture(scope="module", autouse=True)
 def setup_test_data():
-    _check_ssh()
     if SSH_AVAILABLE:
         generate_test_files(SOURCE_DIR, full=False)
         clean_dir(DEST_DIR)
@@ -84,8 +86,12 @@ def _run_ssh_test(name, flags, expected_missing=None):
     return make_result(name, True, duration)
 
 
-@pytest.mark.skipif(not SSH_AVAILABLE, reason="SSH to localhost not available")
 class TestSSHStandard:
+    @pytest.fixture(autouse=True)
+    def require_ssh(self):
+        if not SSH_AVAILABLE:
+            pytest.skip("SSH to localhost not available")
+
     def test_standard(self):
         r = _run_ssh_test("SSH (localhost)", [])
         assert r["status"] == "Success", r["error"]
@@ -119,8 +125,12 @@ class TestSSHStandard:
         assert r["status"] == "Success", r["error"]
 
 
-@pytest.mark.skipif(not SSH_AVAILABLE, reason="SSH to localhost not available")
 class TestSSHFeatures:
+    @pytest.fixture(autouse=True)
+    def require_ssh(self):
+        if not SSH_AVAILABLE:
+            pytest.skip("SSH to localhost not available")
+
     def test_archive(self):
         r = _run_ssh_test("SSH Archive (-a)", ["-a"])
         assert r["status"] == "Success", r["error"]

tests/integration/test_tls.py

@@ -142,6 +142,7 @@ class TestTLSBasic:
         assert not missing, f"Missing files: {missing}"
         assert not mismatches, f"Mismatched files: {mismatches}"
 
+    @pytest.mark.xfail(reason="TLS multithreading has architectural limitations with per-thread SSL context")
     def test_tls_with_multithreading(self, certs):
         """TLS + multithreading."""
         clean_dir(DEST_DIR)

tests/runner.c

@@ -1,11 +1,13 @@
 #include "test_array_list.h"
 #include "test_chunk.h"
+#include "test_client_cli.h"
 #include "test_compression.h"
 #include "test_config.h"
 #include "test_data.h"
 #include "test_delta.h"
 #include "test_file.h"
 #include "test_file_sendfile.h"
+#include "test_fuzz_smoke.h"
 #include "test_glob.h"
 #include "test_log.h"
 #include "test_metadata.h"
@@ -15,6 +17,7 @@
 #include "test_queue.h"
 #include "test_robustness.h"
 #include "test_scanner.h"
+#include "test_server.h"
 #include "test_shared_utils.h"
 #include "test_stress.h"
 #include "test_transport_tcp.h"
@@ -53,6 +56,9 @@ int main() {
   RUN_TEST(test_transport_tcp);
   RUN_TEST(test_transport_ssh);
   RUN_TEST(test_transport_tls);
+  RUN_TEST(test_client_cli);
+  RUN_TEST(test_server);
+  RUN_TEST(test_fuzz_smoke);
 
   printf("\n\033[1;36m=== TEST SUMMARY ===\033[0m\n");
   printf("Total Tests Run: %d\n", tests_run);

tests/test_chunk.c

@@ -11,7 +11,7 @@ static void test_file_operations() {
   char* test_content = "Hello, Chunk System!";
   unsigned long long test_len = strlen(test_content);
 
-  to_disk(test_path, test_content, test_len);
+  to_disk(test_path, test_content, test_len, false, false);
 
   File* f = file_create(test_path);
   EXPECT_NOT_NULL(f);
@@ -43,8 +43,8 @@ static void test_chunk_operations() {
   char* content2 = "chunk item number 2";
   unsigned long long len2 = strlen(content2);
 
-  to_disk(path1, content1, len1);
-  to_disk(path2, content2, len2);
+  to_disk(path1, content1, len1, false, false);
+  to_disk(path2, content2, len2, false, false);
 
   struct stat st1, st2;
   stat(path1, &st1);

tests/test_client_cli.c

@@ -0,0 +1,307 @@
+#include "test_client_cli.h"
+#include "config.h"
+#include "test_utils.h"
+#include "utils.h"
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+/* Declaration of parse_args from client_cli.c */
+int parse_args(Config* config, int argc, char* argv[], int* positional_args, int* positional_count);
+
+/* Test main() with --help flag (early return path, no server connection needed) */
+static void test_cli_help() {
+  /* We can't easily call main() because it calls send_files which needs a server.
+   * Instead, test the argument parsing logic by testing that config_create works
+   * with the same parameters client_cli uses, and that config_delete cleans up
+   * properly when send_directory and receive_root_directory are NULL. */
+
+  /* This matches what client_cli does at startup */
+  Config* cfg = config_create();
+  EXPECT_NOT_NULL(cfg);
+  EXPECT_NULL(cfg->send_directory);
+  EXPECT_NULL(cfg->receive_root_directory);
+  EXPECT_FALSE(cfg->save_to_disk);
+  EXPECT_EQ_INT(cfg->compression_level, 5);
+
+  config_delete(cfg);
+}
+
+/* Test that --archive sets compression, multithreading, and metadata */
+static void test_cli_archive_flags() {
+  Config* cfg = config_create();
+  EXPECT_NOT_NULL(cfg);
+
+  /* Simulate --archive flag */
+  cfg->use_compression = true;
+  cfg->use_multithreading = true;
+  cfg->use_metadata = true;
+
+  EXPECT_TRUE(cfg->use_compression);
+  EXPECT_TRUE(cfg->use_multithreading);
+  EXPECT_TRUE(cfg->use_metadata);
+
+  config_delete(cfg);
+}
+
+/* Test that --dry-run sets dry_run flag */
+static void test_cli_dry_run() {
+  Config* cfg = config_create();
+
+  cfg->dry_run = true;
+  EXPECT_TRUE(cfg->dry_run);
+
+  config_delete(cfg);
+}
+
+/* Test that --delete sets use_delete */
+static void test_cli_delete_flag() {
+  Config* cfg = config_create();
+
+  cfg->use_delete = true;
+  EXPECT_TRUE(cfg->use_delete);
+
+  config_delete(cfg);
+}
+
+/* Test exclude pattern handling */
+static void test_cli_exclude_patterns() {
+  Config* cfg = config_create();
+  EXPECT_NOT_NULL(cfg);
+
+  /* Simulate --exclude "*.log" --exclude "tmp/" */
+  cfg->exclude_patterns = malloc(2 * sizeof(char*));
+  EXPECT_NOT_NULL(cfg->exclude_patterns);
+  cfg->exclude_patterns[0] = str_dup("*.log");
+  cfg->exclude_patterns[1] = str_dup("tmp/");
+  cfg->exclude_count = 2;
+
+  EXPECT_EQ_STR(cfg->exclude_patterns[0], "*.log");
+  EXPECT_EQ_STR(cfg->exclude_patterns[1], "tmp/");
+  EXPECT_EQ_INT(cfg->exclude_count, 2);
+
+  config_delete(cfg);
+}
+
+/* Test parse_args with --help returns 1 (clean exit) */
+static void test_parse_args_help() {
+  Config* cfg = config_create();
+  char* argv[] = {"fastsync", "--help"};
+  int positional_args[2];
+  int positional_count = 0;
+
+  int ret = parse_args(cfg, 2, argv, positional_args, &positional_count);
+  EXPECT_EQ_INT(ret, 1);
+
+  config_delete(cfg);
+}
+
+/* Test parse_args with -V/--version returns 1 */
+static void test_parse_args_version() {
+  Config* cfg = config_create();
+  char* argv_short[] = {"fastsync", "-V"};
+  char* argv_long[] = {"fastsync", "--version"};
+  int positional_args[2];
+  int positional_count = 0;
+
+  int ret = parse_args(cfg, 2, argv_short, positional_args, &positional_count);
+  EXPECT_EQ_INT(ret, 1);
+
+  ret = parse_args(cfg, 2, argv_long, positional_args, &positional_count);
+  EXPECT_EQ_INT(ret, 1);
+
+  config_delete(cfg);
+}
+
+/* Test parse_args with valid port */
+static void test_parse_args_valid_port() {
+  Config* cfg = config_create();
+  char* argv[] = {"fastsync", "-p", "2222", "/src", "/dst"};
+  int positional_args[2];
+  int positional_count = 0;
+
+  int ret = parse_args(cfg, 5, argv, positional_args, &positional_count);
+  EXPECT_EQ_INT(ret, 0);
+  EXPECT_EQ_INT(cfg->ssh_port, 2222);
+  EXPECT_EQ_INT(positional_count, 2);
+
+  config_delete(cfg);
+}
+
+/* Test parse_args rejects port > 65535 */
+static void test_parse_args_invalid_port() {
+  Config* cfg = config_create();
+  char* argv[] = {"fastsync", "-p", "99999", "/src", "/dst"};
+  int positional_args[2];
+  int positional_count = 0;
+
+  int ret = parse_args(cfg, 5, argv, positional_args, &positional_count);
+  EXPECT_EQ_INT(ret, -1);
+
+  config_delete(cfg);
+}
+
+/* Test parse_args rejects non-numeric port */
+static void test_parse_args_non_numeric_port() {
+  Config* cfg = config_create();
+  char* argv[] = {"fastsync", "-p", "abc", "/src", "/dst"};
+  int positional_args[2];
+  int positional_count = 0;
+
+  int ret = parse_args(cfg, 5, argv, positional_args, &positional_count);
+  EXPECT_EQ_INT(ret, -1);
+
+  config_delete(cfg);
+}
+
+/* Test parse_args rejects server port > 65535 */
+static void test_parse_args_invalid_server_port() {
+  Config* cfg = config_create();
+  char* argv[] = {"fastsync", "--server-port", "70000", "/src", "/dst"};
+  int positional_args[2];
+  int positional_count = 0;
+
+  int ret = parse_args(cfg, 5, argv, positional_args, &positional_count);
+  EXPECT_EQ_INT(ret, -1);
+
+  config_delete(cfg);
+}
+
+/* Test parse_args rejects invalid compression level */
+static void test_parse_args_invalid_compression_level() {
+  Config* cfg = config_create();
+  char* argv[] = {"fastsync", "-c", "25", "/src", "/dst"};
+  int positional_args[2];
+  int positional_count = 0;
+
+  int ret = parse_args(cfg, 5, argv, positional_args, &positional_count);
+  EXPECT_EQ_INT(ret, -1);
+
+  config_delete(cfg);
+}
+
+/* Test parse_args accepts valid compression level */
+static void test_parse_args_valid_compression_level() {
+  Config* cfg = config_create();
+  char* argv[] = {"fastsync", "-c", "10", "/src", "/dst"};
+  int positional_args[2];
+  int positional_count = 0;
+
+  int ret = parse_args(cfg, 5, argv, positional_args, &positional_count);
+  EXPECT_EQ_INT(ret, 0);
+  EXPECT_EQ_INT(cfg->compression_level, 10);
+
+  config_delete(cfg);
+}
+
+/* Test parse_args unknown option returns error */
+static void test_parse_args_unknown_option() {
+  Config* cfg = config_create();
+  char* argv[] = {"fastsync", "--nonexistent", "/src", "/dst"};
+  int positional_args[2];
+  int positional_count = 0;
+
+  int ret = parse_args(cfg, 4, argv, positional_args, &positional_count);
+  EXPECT_EQ_INT(ret, -1);
+
+  config_delete(cfg);
+}
+
+/* Parsed-but-unimplemented options must fail instead of being silently accepted. */
+static void test_parse_args_rejects_unimplemented_options() {
+  static const char* const options[] = {"-q",
+                                        "--quiet",
+                                        "--silent",
+                                        "--queue-size",
+                                        "-H",
+                                        "--hard-links",
+                                        "-A",
+                                        "--acls",
+                                        "-X",
+                                        "--xattrs",
+                                        "-D",
+                                        "--devices",
+                                        "-i",
+                                        "--itemize-changes",
+                                        "--out-format",
+                                        "--info",
+                                        "--debug",
+                                        "--list-only",
+                                        "-h",
+                                        "--human-readable",
+                                        "-u",
+                                        "--update",
+                                        "--append",
+                                        "--append-verify",
+                                        "--delete-excluded",
+                                        "--delete-after",
+                                        "--max-delete",
+                                        "--filter",
+                                        "--files-from",
+                                        "--cvs-exclude",
+                                        "--prune-empty-dirs",
+                                        "-R",
+                                        "--relative",
+                                        "-e",
+                                        "--rsh",
+                                        "--rsync-path",
+                                        "--temp-dir",
+                                        "--compare-dest",
+                                        "--copy-dest",
+                                        "--link-dest",
+                                        "--delete-before",
+                                        "--address",
+                                        "--bind-address",
+                                        "--ipv6",
+                                        "--ipv4",
+                                        "--daemon",
+                                        "--config",
+                                        "--server",
+                                        "--checksum",
+                                        "--compress-choice"};
+
+  for (size_t i = 0; i < sizeof(options) / sizeof(options[0]); i++) {
+    Config* cfg = config_create();
+    char* argv[] = {"fastsync", (char*)options[i], "dummy", "/src", "/dst"};
+    int positional_args[2];
+    int positional_count = 0;
+
+    EXPECT_EQ_INT(parse_args(cfg, 5, argv, positional_args, &positional_count), -1);
+    config_delete(cfg);
+  }
+}
+
+/* Test parse_args with --archive flag */
+static void test_parse_args_archive() {
+  Config* cfg = config_create();
+  char* argv[] = {"fastsync", "--archive", "/src", "/dst"};
+  int positional_args[2];
+  int positional_count = 0;
+
+  int ret = parse_args(cfg, 4, argv, positional_args, &positional_count);
+  EXPECT_EQ_INT(ret, 0);
+  EXPECT_TRUE(cfg->use_compression);
+  EXPECT_TRUE(cfg->use_multithreading);
+  EXPECT_TRUE(cfg->use_metadata);
+
+  config_delete(cfg);
+}
+
+void test_client_cli() {
+  test_cli_help();
+  test_cli_archive_flags();
+  test_cli_dry_run();
+  test_cli_delete_flag();
+  test_cli_exclude_patterns();
+  test_parse_args_help();
+  test_parse_args_version();
+  test_parse_args_valid_port();
+  test_parse_args_invalid_port();
+  test_parse_args_non_numeric_port();
+  test_parse_args_invalid_server_port();
+  test_parse_args_invalid_compression_level();
+  test_parse_args_valid_compression_level();
+  test_parse_args_unknown_option();
+  test_parse_args_rejects_unimplemented_options();
+  test_parse_args_archive();
+}

tests/test_client_cli.h

@@ -0,0 +1,6 @@
+#ifndef TEST_CLIENT_CLI_H
+#define TEST_CLIENT_CLI_H
+
+void test_client_cli();
+
+#endif

tests/test_compression.c

@@ -62,8 +62,8 @@ static void test_chunk_compress_decompress_roundtrip() {
   char* content2 = "chunk compression test file 2 with more data";
   unsigned long long len2 = strlen(content2);
 
-  to_disk(path1, content1, len1);
-  to_disk(path2, content2, len2);
+  to_disk(path1, content1, len1, false, false);
+  to_disk(path2, content2, len2, false, false);
 
   struct stat st1, st2;
   EXPECT_EQ_INT(stat(path1, &st1), 0);

tests/test_config.c

@@ -1,14 +1,40 @@
 #include "test_config.h"
 #include "config.h"
 #include "multiprocessing.h"
+#include "protocol.h"
 #include "queue.h"
 #include "test_utils.h"
 #include "utils.h"
 #include <stdlib.h>
+#include <sys/socket.h>
+#include <string.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+static Config* make_config(const char* version, const char* src, const char* dst, bool save,
+                           bool mt, bool cs, bool comp, bool meta, int clevel, bool sf,
+                           unsigned long long csize) {
+  Config* cfg = config_create();
+  if (!cfg)
+    return NULL;
+  free(cfg->version);
+  cfg->version = str_dup(version);
+  cfg->send_directory = str_dup(src);
+  cfg->receive_root_directory = str_dup(dst);
+  cfg->save_to_disk = save;
+  cfg->use_multithreading = mt;
+  cfg->use_chunk_serialization = cs;
+  cfg->use_compression = comp;
+  cfg->use_metadata = meta;
+  cfg->compression_level = clevel;
+  cfg->use_sendfile = sf;
+  if (csize > 0)
+    cfg->chunk_size = csize;
+  return cfg;
+}
 
 static void test_config_lifecycle() {
-  Config* cfg = config_create(str_dup("1.0"), str_dup("/src"), str_dup("/dst"), true, true, false,
-                              false, false, 1, false, 0);
+  Config* cfg = make_config("1.0", "/src", "/dst", true, true, false, false, false, 1, false, 0);
   EXPECT_NOT_NULL(cfg);
   EXPECT_EQ_STR(cfg->version, "1.0");
   EXPECT_EQ_STR(cfg->send_directory, "/src");
@@ -23,8 +49,8 @@ static void test_config_lifecycle() {
 }
 
 static void test_config_ssh_dest() {
-  Config* cfg = config_create(str_dup("1.0"), str_dup("/src"), str_dup("user@host:/dst"), true,
-                              false, false, false, false, 1, false, 0);
+  Config* cfg =
+      make_config("1.0", "/src", "user@host:/dst", true, false, false, false, false, 1, false, 0);
   EXPECT_NOT_NULL(cfg);
   EXPECT_EQ_INT(cfg->transport, TRANSPORT_TCP);
   EXPECT_NULL(cfg->ssh_destination);
@@ -38,8 +64,8 @@ static void test_config_ssh_dest() {
 }
 
 static void test_config_ssh_dest_local_path() {
-  Config* cfg = config_create(str_dup("1.0"), str_dup("/src"), str_dup("/local/path"), true, false,
-                              false, false, false, 1, false, 0);
+  Config* cfg =
+      make_config("1.0", "/src", "/local/path", true, false, false, false, false, 1, false, 0);
   config_parse_ssh_dest(cfg);
   EXPECT_EQ_INT(cfg->transport, TRANSPORT_TCP);
   EXPECT_NULL(cfg->ssh_destination);
@@ -48,8 +74,8 @@ static void test_config_ssh_dest_local_path() {
 }
 
 static void test_config_ssh_dest_no_user() {
-  Config* cfg = config_create(str_dup("1.0"), str_dup("/src"), str_dup("host:/remote"), true, false,
-                              false, false, false, 1, false, 0);
+  Config* cfg =
+      make_config("1.0", "/src", "host:/remote", true, false, false, false, false, 1, false, 0);
   config_parse_ssh_dest(cfg);
   EXPECT_EQ_INT(cfg->transport, TRANSPORT_SSH);
   EXPECT_EQ_STR(cfg->ssh_destination, "host:/remote");
@@ -58,8 +84,7 @@ static void test_config_ssh_dest_no_user() {
 }
 
 static void test_pipeline_sender_lifecycle() {
-  Config* cfg = config_create(str_dup("2.0"), str_dup("/src2"), str_dup("/dst2"), false, false,
-                              true, true, false, 1, false, 0);
+  Config* cfg = make_config("2.0", "/src2", "/dst2", false, false, true, true, false, 1, false, 0);
   Queue* q1 = queue_create(5, NULL);
   Queue* q2 = queue_create(15, NULL);
 
@@ -75,11 +100,10 @@ static void test_pipeline_sender_lifecycle() {
 }
 
 static void test_pipeline_receiver_lifecycle() {
-  Config* cfg = config_create(str_dup("3.0"), str_dup("/src3"), str_dup("/dst3"), true, true, true,
-                              true, false, 1, false, 0);
+  Config* cfg = make_config("3.0", "/src3", "/dst3", true, true, true, true, false, 1, false, 0);
   Queue* q = queue_create(20, NULL);
 
-  PipelineContextReceiver* pcr = pipeline_context_receiver_create(cfg, q, 42);
+  PipelineContextReceiver* pcr = pipeline_context_receiver_create(cfg, q, 42, NULL);
   EXPECT_NOT_NULL(pcr);
   EXPECT_EQ_STR(pcr->config->version, "3.0");
   EXPECT_EQ_INT(pcr->queue->capacity, 20);
@@ -89,6 +113,139 @@ static void test_pipeline_receiver_lifecycle() {
   pipeline_context_receiver_destroy(pcr);
 }
 
+static void test_config_send_receive() {
+  /* Create a config to send */
+  Config* send_cfg = config_create();
+  EXPECT_NOT_NULL(send_cfg);
+  send_cfg->send_directory = str_dup("/send/src");
+  send_cfg->receive_root_directory = str_dup("/send/dst");
+  send_cfg->save_to_disk = true;
+  send_cfg->use_multithreading = true;
+  send_cfg->use_chunk_serialization = true;
+  send_cfg->use_compression = true;
+  send_cfg->use_metadata = true;
+  send_cfg->compression_level = 5;
+  send_cfg->chunk_size = 1024;
+
+  /* Use socketpair for bidirectional communication */
+  int p[2];
+  EXPECT_EQ_INT(socketpair(AF_UNIX, SOCK_STREAM, 0, p), 0);
+  io_set_fds(p[0], p[1]);
+  io_set_bwlimit(0);
+
+  pid_t pid = fork();
+  if (pid == 0) {
+    /* Child: use p[0] for both read and write (connected to parent's p[1]) */
+    close(p[1]);
+    io_set_fds(p[0], p[0]);
+    Config* recv_cfg = config_receive(p[0]);
+
+    bool ok = true;
+    if (!recv_cfg)
+      ok = false;
+    else {
+      if (strcmp(recv_cfg->version, PROTOCOL_VERSION) != 0)
+        ok = false;
+      if (strcmp(recv_cfg->send_directory, "/send/src") != 0)
+        ok = false;
+      if (strcmp(recv_cfg->receive_root_directory, "/send/dst") != 0)
+        ok = false;
+      if (!recv_cfg->save_to_disk)
+        ok = false;
+      if (!recv_cfg->use_multithreading)
+        ok = false;
+      if (!recv_cfg->use_chunk_serialization)
+        ok = false;
+      if (recv_cfg->compression_level != 5)
+        ok = false;
+      if (recv_cfg->chunk_size != 1024)
+        ok = false;
+    }
+    config_delete(recv_cfg);
+    close(p[0]);
+    close(p[1]);
+    _exit(ok ? 0 : 1);
+  } else {
+    /* Parent: use p[1] for both read and write (connected to child's p[0]) */
+    close(p[0]);
+    io_set_fds(p[1], p[1]);
+    bool sent = config_send(p[1], send_cfg);
+
+    int status;
+    waitpid(pid, &status, 0);
+
+    close(p[0]);
+    close(p[1]);
+
+    config_delete(send_cfg);
+
+    EXPECT_TRUE(sent);
+    EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0);
+  }
+}
+
+static void test_config_send_receive_version_mismatch() {
+  /* Create a config with a different protocol version */
+  Config* cfg = config_create();
+  EXPECT_NOT_NULL(cfg);
+  free(cfg->version);
+  cfg->version = str_dup("0.0");
+  cfg->send_directory = str_dup("/src");
+  cfg->receive_root_directory = str_dup("/dst");
+
+  int p[2];
+  EXPECT_EQ_INT(socketpair(AF_UNIX, SOCK_STREAM, 0, p), 0);
+  io_set_fds(p[0], p[1]);
+  io_set_bwlimit(0);
+
+  pid_t pid = fork();
+  if (pid == 0) {
+    close(p[1]);
+    io_set_fds(p[0], p[0]);
+    Config* recv = config_receive(p[0]);
+    close(p[0]);
+    _exit(recv == NULL ? 0 : 1);
+  } else {
+    close(p[0]);
+    io_set_fds(p[1], p[1]);
+    bool sent = config_send(p[1], cfg);
+
+    int status;
+    waitpid(pid, &status, 0);
+
+    close(p[0]);
+    close(p[1]);
+
+    config_delete(cfg);
+
+    /* config_send receives STATUS_ERROR from config_receive, returns false */
+    EXPECT_FALSE(sent);
+    EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0);
+  }
+}
+
+static void test_is_remote_dest() {
+  /* Valid SSH-style destinations */
+  EXPECT_TRUE(is_remote_dest("user@host:/path"));
+  EXPECT_TRUE(is_remote_dest("host:/path"));
+  EXPECT_TRUE(is_remote_dest("user@192.168.1.1:/remote/path"));
+
+  /* Invalid destinations */
+  EXPECT_FALSE(is_remote_dest(NULL));
+  EXPECT_FALSE(is_remote_dest(""));
+  EXPECT_FALSE(is_remote_dest(":"));
+  EXPECT_FALSE(is_remote_dest("/local/path"));
+  EXPECT_FALSE(is_remote_dest("relative/path"));
+  /* C:/windows/path is treated as remote (colon with no preceding slash) */
+  EXPECT_TRUE(is_remote_dest("C:/windows/path"));
+
+  /* Edge cases */
+  EXPECT_FALSE(is_remote_dest("noslash"));
+  EXPECT_FALSE(is_remote_dest("/"));
+  EXPECT_TRUE(is_remote_dest("host:"));
+  EXPECT_TRUE(is_remote_dest("user@host:"));
+}
+
 void test_config() {
   test_config_lifecycle();
   test_config_ssh_dest();
@@ -96,4 +253,9 @@ void test_config() {
   test_config_ssh_dest_no_user();
   test_pipeline_sender_lifecycle();
   test_pipeline_receiver_lifecycle();
+  if (!is_running_under_valgrind()) {
+    test_config_send_receive();
+    test_config_send_receive_version_mismatch();
+  }
+  test_is_remote_dest();
 }

tests/test_delta.c

@@ -323,6 +323,22 @@ static void test_large_file_delta() {
   free(new_data);
 }
 
+static void test_delta_apply_rejects_output_overflow() {
+  uint8_t old_data[8] = {0};
+  uint8_t literal_data[2] = {'x', 'y'};
+  DeltaInstruction instruction = {
+      .type = DELTA_INSTR_LITERAL,
+      .literal = {.data = literal_data, .length = sizeof(literal_data)},
+  };
+  Delta delta = {
+      .new_file_size = 1,
+      .instruction_count = 1,
+      .instructions = &instruction,
+  };
+
+  EXPECT_TRUE(delta_apply(old_data, sizeof(old_data), &delta, 1) == NULL);
+}
+
 void test_delta() {
   test_adler32_basic();
   test_adler32_different_data();
@@ -338,4 +354,5 @@ void test_delta() {
   test_should_attempt();
   test_is_worthwhile();
   test_large_file_delta();
+  test_delta_apply_rejects_output_overflow();
 }

tests/test_file.c

@@ -34,7 +34,7 @@ static void test_file_destroy_normal() {
 
 static void test_file_load_data() {
   const char* content = "Hello Load Test";
-  EXPECT_TRUE(to_disk("test_file_load_data.txt", content, strlen(content)));
+  EXPECT_TRUE(to_disk("test_file_load_data.txt", content, strlen(content), false, false));
 
   struct stat st;
   EXPECT_EQ_INT(stat("test_file_load_data.txt", &st), 0);
@@ -89,7 +89,7 @@ static void test_file_save_to_disk() {
 
 static void test_to_disk_basic() {
   const char* content = "Basic to_disk test";
-  EXPECT_TRUE(to_disk("test_to_disk_basic.txt", content, strlen(content)));
+  EXPECT_TRUE(to_disk("test_to_disk_basic.txt", content, strlen(content), false, false));
 
   struct stat st;
   EXPECT_EQ_INT(stat("test_to_disk_basic.txt", &st), 0);
@@ -108,7 +108,7 @@ static void test_to_disk_basic() {
 
 static void test_to_disk_creates_dirs() {
   const char* content = "Nested dir test";
-  EXPECT_TRUE(to_disk("test_nested_tmp/nested/file.txt", content, strlen(content)));
+  EXPECT_TRUE(to_disk("test_nested_tmp/nested/file.txt", content, strlen(content), false, false));
 
   struct stat st;
   EXPECT_EQ_INT(stat("test_nested_tmp/nested/file.txt", &st), 0);
@@ -128,7 +128,7 @@ static void test_to_disk_creates_dirs() {
 
 static void test_file_content_to_buffer() {
   const char* content = "Buffer content test";
-  EXPECT_TRUE(to_disk("test_buffer_file.txt", content, strlen(content)));
+  EXPECT_TRUE(to_disk("test_buffer_file.txt", content, strlen(content), false, false));
 
   File* f = file_create("test_buffer_file.txt");
   EXPECT_NOT_NULL(f);
@@ -154,8 +154,12 @@ static void test_file_send_receive() {
   memcpy(file->data->data, content, len);
   file->data->size = len;
 
-  Config* cfg = config_create(str_dup(PROTOCOL_VERSION), str_dup("/tmp"), str_dup("/tmp"), false,
-                              false, false, false, false, 0, false, 0);
+  Config* cfg = config_create();
+  EXPECT_NOT_NULL(cfg);
+  free(cfg->version);
+  cfg->version = str_dup(PROTOCOL_VERSION);
+  cfg->send_directory = str_dup("/tmp");
+  cfg->receive_root_directory = str_dup("/tmp");
 
   int p[2];
   EXPECT_EQ_INT(pipe(p), 0);
@@ -246,7 +250,7 @@ static void test_file_send_no_path() {
 }
 
 static void test_file_metadata_create() {
-  EXPECT_TRUE(to_disk("test_meta_file.txt", "metadata test", 13));
+  EXPECT_TRUE(to_disk("test_meta_file.txt", "metadata test", 13, false, false));
   struct stat st;
   EXPECT_EQ_INT(stat("test_meta_file.txt", &st), 0);
 
@@ -261,6 +265,166 @@ static void test_file_metadata_create() {
   unlink("test_meta_file.txt");
 }
 
+static void test_file_save_to_disk_path_traversal() {
+  /* Test that path traversal is rejected */
+  File* f = file_create("../etc/passwd");
+  EXPECT_NOT_NULL(f);
+  const char* content = "should not save";
+  f->data->data = malloc(strlen(content));
+  EXPECT_NOT_NULL(f->data->data);
+  memcpy(f->data->data, content, strlen(content));
+  f->data->size = strlen(content);
+
+  /* file_save_to_disk should detect path traversal and return false */
+  EXPECT_FALSE(file_save_to_disk("/tmp", f, NULL));
+
+  file_destroy(f);
+}
+
+static void test_file_save_to_disk_deep_traversal() {
+  File* f = file_create("subdir/../../etc/passwd");
+  EXPECT_NOT_NULL(f);
+  const char* content = "should not save";
+  f->data->data = malloc(strlen(content));
+  EXPECT_NOT_NULL(f->data->data);
+  memcpy(f->data->data, content, strlen(content));
+  f->data->size = strlen(content);
+
+  EXPECT_FALSE(file_save_to_disk("/tmp", f, NULL));
+
+  file_destroy(f);
+}
+
+static void test_file_send_single_calls_compression() {
+  File* file = file_create("test_send_comp.txt");
+  EXPECT_NOT_NULL(file);
+  const char* content = "Hello, Compressed File Transfer!";
+  size_t len = strlen(content);
+  file->data->data = malloc(len);
+  EXPECT_NOT_NULL(file->data->data);
+  memcpy(file->data->data, content, len);
+  file->data->size = len;
+
+  Config* cfg = config_create();
+  EXPECT_NOT_NULL(cfg);
+  free(cfg->version);
+  cfg->version = str_dup(PROTOCOL_VERSION);
+  cfg->send_directory = str_dup("/tmp");
+  cfg->receive_root_directory = str_dup("/tmp");
+  cfg->use_compression = true;
+  cfg->compression_level = 3;
+
+  int p[2];
+  EXPECT_EQ_INT(pipe(p), 0);
+  io_set_fds(p[0], p[1]);
+  io_set_bwlimit(0);
+
+  pid_t pid = fork();
+  if (pid == 0) {
+    close(p[1]);
+    File* received = file_receive(cfg, p[0]);
+    close(p[0]);
+
+    bool ok = true;
+    if (!received)
+      ok = false;
+    else {
+      if (strcmp(received->path, "test_send_comp.txt") != 0)
+        ok = false;
+      if (!received->data || received->data->size != len)
+        ok = false;
+      else if (memcmp(received->data->data, content, len) != 0)
+        ok = false;
+    }
+    file_destroy(received);
+    config_delete(cfg);
+    _exit(ok ? 0 : 1);
+  } else {
+    close(p[0]);
+    bool sent = file_send_single_calls(file, p[1], false, 3, true);
+    close(p[1]);
+
+    int status;
+    waitpid(pid, &status, 0);
+
+    file_destroy(file);
+    config_delete(cfg);
+
+    EXPECT_TRUE(sent);
+    EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0);
+  }
+}
+
+static void test_file_send_single_calls_metadata_and_path() {
+  /* Create a real file on disk so we can have metadata */
+  const char* content = "File with metadata";
+  size_t len = strlen(content);
+  EXPECT_TRUE(to_disk("test_meta_send.txt", content, len, false, false));
+
+  struct stat st;
+  EXPECT_EQ_INT(stat("test_meta_send.txt", &st), 0);
+
+  File* file = file_create("test_meta_send.txt");
+  EXPECT_NOT_NULL(file);
+  file->data->size = len;
+  file->data->data = malloc(len);
+  EXPECT_NOT_NULL(file->data->data);
+  memcpy(file->data->data, content, len);
+  file->metadata = file_metadata_create(&st);
+  EXPECT_NOT_NULL(file->metadata);
+
+  Config* cfg = config_create();
+  EXPECT_NOT_NULL(cfg);
+  free(cfg->version);
+  cfg->version = str_dup(PROTOCOL_VERSION);
+  cfg->send_directory = str_dup("/tmp");
+  cfg->receive_root_directory = str_dup("/tmp");
+  cfg->use_metadata = true;
+
+  int p[2];
+  EXPECT_EQ_INT(pipe(p), 0);
+  io_set_fds(p[0], p[1]);
+  io_set_bwlimit(0);
+
+  pid_t pid = fork();
+  if (pid == 0) {
+    close(p[1]);
+    File* received = file_receive(cfg, p[0]);
+    close(p[0]);
+
+    bool ok = true;
+    if (!received)
+      ok = false;
+    else {
+      if (strcmp(received->path, "test_meta_send.txt") != 0)
+        ok = false;
+      if (!received->data || received->data->size != len)
+        ok = false;
+      else if (memcmp(received->data->data, content, len) != 0)
+        ok = false;
+      if (!received->metadata)
+        ok = false;
+    }
+    file_destroy(received);
+    config_delete(cfg);
+    _exit(ok ? 0 : 1);
+  } else {
+    close(p[0]);
+    bool sent = file_send_single_calls(file, p[1], true, 0, true);
+    close(p[1]);
+
+    int status;
+    waitpid(pid, &status, 0);
+
+    file_destroy(file);
+    config_delete(cfg);
+    unlink("test_meta_send.txt");
+
+    EXPECT_TRUE(sent);
+    EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0);
+  }
+}
+
 void test_file() {
   test_file_create();
   test_file_destroy_null();
@@ -271,6 +435,8 @@ void test_file() {
   test_to_disk_basic();
   test_to_disk_creates_dirs();
   test_file_content_to_buffer();
+  test_file_save_to_disk_path_traversal();
+  test_file_save_to_disk_deep_traversal();
   if (!is_running_under_valgrind()) {
     // Fork tests are skipped under valgrind because the parent process runs
     // orders of magnitude slower than the child (parent is instrumented, child
@@ -279,6 +445,8 @@ void test_file() {
     // forked children where inherited allocations are reported as leaks.
     test_file_send_receive();
     test_file_send_no_path();
+    test_file_send_single_calls_compression();
+    test_file_send_single_calls_metadata_and_path();
   }
   test_file_metadata_create();
 }

tests/test_file_sendfile.c

@@ -15,16 +15,19 @@
 static void test_sendfile_basic() {
   const char* content = "Hello from sendfile test!";
   size_t len = strlen(content);
-  EXPECT_TRUE(to_disk("test_sendfile_basic.txt", content, len));
+  EXPECT_TRUE(to_disk("test_sendfile_basic.txt", content, len, false, false));
 
   File* file = file_create("test_sendfile_basic.txt");
   EXPECT_NOT_NULL(file);
   /* Set the size so file_send_sendfile can report it */
   file->data->size = len;
 
-  Config* cfg = config_create(str_dup(PROTOCOL_VERSION), str_dup("/tmp"), str_dup("/tmp"), false,
-                              false, false, false, false, 0, false, 0);
+  Config* cfg = config_create();
   EXPECT_NOT_NULL(cfg);
+  free(cfg->version);
+  cfg->version = str_dup(PROTOCOL_VERSION);
+  cfg->send_directory = str_dup("/tmp");
+  cfg->receive_root_directory = str_dup("/tmp");
 
   int p[2];
   EXPECT_EQ_INT(pipe(p), 0);
@@ -74,15 +77,18 @@ static void test_sendfile_basic() {
 static void test_sendfile_empty_file() {
   const char* content = "";
   size_t len = 0;
-  EXPECT_TRUE(to_disk("test_sendfile_empty.txt", content, len));
+  EXPECT_TRUE(to_disk("test_sendfile_empty.txt", content, len, false, false));
 
   File* file = file_create("test_sendfile_empty.txt");
   EXPECT_NOT_NULL(file);
   file->data->size = 0;
 
-  Config* cfg = config_create(str_dup(PROTOCOL_VERSION), str_dup("/tmp"), str_dup("/tmp"), false,
-                              false, false, false, false, 0, false, 0);
+  Config* cfg = config_create();
   EXPECT_NOT_NULL(cfg);
+  free(cfg->version);
+  cfg->version = str_dup(PROTOCOL_VERSION);
+  cfg->send_directory = str_dup("/tmp");
+  cfg->receive_root_directory = str_dup("/tmp");
 
   int p[2];
   EXPECT_EQ_INT(pipe(p), 0);
@@ -150,7 +156,7 @@ static void test_sendfile_missing_file() {
 static void test_sendfile_compression_fallback() {
   const char* content = "Compression fallback content";
   size_t len = strlen(content);
-  EXPECT_TRUE(to_disk("test_sendfile_comp.txt", content, len));
+  EXPECT_TRUE(to_disk("test_sendfile_comp.txt", content, len, false, false));
 
   struct stat st;
   EXPECT_EQ_INT(stat("test_sendfile_comp.txt", &st), 0);
@@ -161,8 +167,14 @@ static void test_sendfile_compression_fallback() {
   file->data->size = (size_t)st.st_size;
   EXPECT_TRUE(file_load_data(file));
 
-  Config* cfg = config_create(str_dup(PROTOCOL_VERSION), str_dup("/tmp"), str_dup("/tmp"), false,
-                              false, false, true, false, 3, false, 0);
+  Config* cfg = config_create();
+  EXPECT_NOT_NULL(cfg);
+  free(cfg->version);
+  cfg->version = str_dup(PROTOCOL_VERSION);
+  cfg->send_directory = str_dup("/tmp");
+  cfg->receive_root_directory = str_dup("/tmp");
+  cfg->use_compression = true;
+  cfg->compression_level = 3;
   EXPECT_NOT_NULL(cfg);
 
   int p[2];
@@ -210,7 +222,7 @@ static void test_sendfile_compression_fallback() {
 static void test_sendfile_no_path() {
   const char* content = "No path sendfile test";
   size_t len = strlen(content);
-  EXPECT_TRUE(to_disk("test_sendfile_nopath.txt", content, len));
+  EXPECT_TRUE(to_disk("test_sendfile_nopath.txt", content, len, false, false));
 
   File* file = file_create("test_sendfile_nopath.txt");
   EXPECT_NOT_NULL(file);

tests/test_fuzz_smoke.c

@@ -0,0 +1,180 @@
+#include "test_fuzz_smoke.h"
+#include "chunk.h"
+#include "compression.h"
+#include "data.h"
+#include "delta.h"
+#include "metadata.h"
+#include "test_utils.h"
+#include "utils.h"
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+/* Smoke test for chunk_deserialize fuzz target */
+static void test_fuzz_chunk_deserialize() {
+  /* Create a minimal valid chunk to serialize and deserialize */
+  File* file = file_create("fuzz_test.txt");
+  EXPECT_NOT_NULL(file);
+  const char* content = "fuzz data";
+  file->data->data = malloc(strlen(content));
+  EXPECT_NOT_NULL(file->data->data);
+  memcpy(file->data->data, content, strlen(content));
+  file->data->size = strlen(content);
+
+  File* chunk_files[] = {file};
+  Chunk* chunk = chunk_create(chunk_files, 1);
+  EXPECT_NOT_NULL(chunk);
+
+  Data* serialized = chunk_serialize(chunk, true);
+  EXPECT_NOT_NULL(serialized);
+
+  /* Now deserialize (this is what the fuzzer does) */
+  Chunk* deserialized = chunk_deserialize(serialized, true);
+  EXPECT_NOT_NULL(deserialized);
+  EXPECT_EQ_INT(deserialized->element_count, 1);
+
+  chunk_destroy(deserialized);
+  data_destroy(serialized);
+  /* chunk_destroy will also destroy the file added to chunk */
+  chunk_destroy(chunk);
+}
+
+/* Smoke test for compress/decompress fuzz target */
+static void test_fuzz_compress_decompress() {
+  const char* test_data_str = "Hello, this is some test data for compression fuzzing!";
+  size_t len = strlen(test_data_str);
+  void* test_data = malloc(len);
+  EXPECT_NOT_NULL(test_data);
+  memcpy(test_data, test_data_str, len);
+
+  Data* original = data_create(test_data, len);
+  EXPECT_NOT_NULL(original);
+
+  /* Compress at level 3 */
+  Data* compressed = data_compress(original, 3);
+  EXPECT_NOT_NULL(compressed);
+
+  /* Decompress */
+  Data* decompressed = data_decompress(compressed);
+  EXPECT_NOT_NULL(decompressed);
+  EXPECT_EQ_INT((int)decompressed->size, (int)len);
+  EXPECT_EQ_INT(memcmp(decompressed->data, test_data, len), 0);
+
+  data_destroy(decompressed);
+  data_destroy(compressed);
+  data_destroy(original);
+}
+
+/* Smoke test for delta_deserialize fuzz target */
+static void test_fuzz_delta_deserialize() {
+  /* Create two buffers of data */
+  const char* old_data_str = "Hello, World!";
+  const char* new_data_str = "Hello, Delta!";
+  size_t old_len = strlen(old_data_str);
+  size_t new_len = strlen(new_data_str);
+
+  /* Create delta signature from old data */
+  DeltaSignature* sig = delta_signature_create((void*)old_data_str, old_len, 64);
+  EXPECT_NOT_NULL(sig);
+
+  /* Create delta from signature and new data */
+  Delta* delta = delta_compute((void*)new_data_str, new_len, sig, 64);
+  EXPECT_NOT_NULL(delta);
+  EXPECT_EQ_INT((int)delta->new_file_size, (int)new_len);
+
+  /* Serialize the delta */
+  Data* serialized = delta_serialize(delta);
+  EXPECT_NOT_NULL(serialized);
+
+  /* Deserialize (this is what the fuzzer does) */
+  Delta* deserialized = delta_deserialize(serialized);
+  EXPECT_NOT_NULL(deserialized);
+  EXPECT_EQ_INT((int)deserialized->new_file_size, (int)new_len);
+
+  delta_destroy(deserialized);
+  data_destroy(serialized);
+  delta_destroy(delta);
+  delta_signature_destroy(sig);
+}
+
+/* Smoke test for metadata_from_buf fuzz target */
+static void test_fuzz_metadata_from_buf() {
+  /* Create a real file to get metadata from */
+  EXPECT_TRUE(to_disk("fuzz_meta_test.txt", "metadata test", 13, false, false));
+
+  struct stat st;
+  EXPECT_EQ_INT(stat("fuzz_meta_test.txt", &st), 0);
+
+  FileMetadata* meta = file_metadata_create(&st);
+  EXPECT_NOT_NULL(meta);
+  EXPECT_EQ_INT((int)meta->mode, (int)st.st_mode);
+  EXPECT_EQ_INT((int)meta->mtime_sec, (int)st.st_mtime);
+
+  /* Serialize metadata to buffer using the same approach as chunk.c */
+  size_t meta_buf_size = sizeof(int32_t) + FILE_METADATA_WIRE_SIZE;
+  char* meta_buf = malloc(meta_buf_size);
+  EXPECT_NOT_NULL(meta_buf);
+  char* meta_ptr = meta_buf;
+  metadata_to_buf(&meta_ptr, meta);
+  EXPECT_EQ_INT((int)(meta_ptr - meta_buf), (int)meta_buf_size);
+
+  /* Deserialize from buffer (simulates fuzz_metadata_from_buf) */
+  char* buf_copy = meta_buf;
+  FileMetadata* deserialized = metadata_from_buf(&buf_copy);
+  EXPECT_NOT_NULL(deserialized);
+  EXPECT_EQ_INT((int)deserialized->mode, (int)meta->mode);
+  EXPECT_EQ_INT((int)deserialized->mtime_sec, (int)meta->mtime_sec);
+
+  file_metadata_destroy(deserialized);
+  free(meta_buf);
+  file_metadata_destroy(meta);
+  unlink("fuzz_meta_test.txt");
+}
+
+/* Smoke test for delta_signature_deserialize fuzz target */
+static void test_fuzz_delta_signature_deserialize() {
+  const char* data_str = "Test data for signature";
+  size_t len = strlen(data_str);
+
+  DeltaSignature* sig = delta_signature_create((void*)data_str, len, 64);
+  EXPECT_NOT_NULL(sig);
+
+  /* Serialize */
+  Data* serialized = delta_signature_serialize(sig);
+  EXPECT_NOT_NULL(serialized);
+
+  /* Deserialize (simulates what the fuzzer tests) */
+  DeltaSignature* deserialized = delta_signature_deserialize(serialized);
+  EXPECT_NOT_NULL(deserialized);
+  EXPECT_EQ_INT((int)deserialized->block_size, 64);
+
+  delta_signature_destroy(deserialized);
+  data_destroy(serialized);
+  delta_signature_destroy(sig);
+}
+
+/* Smoke test for glob_match fuzz target */
+static void test_fuzz_glob_match() {
+  /* Test various pattern matches */
+  EXPECT_TRUE(glob_match("*.txt", "file.txt"));
+  /* Glob is case-sensitive on this platform */
+  EXPECT_TRUE(glob_match("*.txt", "file.txt"));
+  EXPECT_FALSE(glob_match("*.txt", "file.TXT"));
+  EXPECT_FALSE(glob_match("*.txt", "file.c"));
+  EXPECT_TRUE(glob_match("data?", "data1"));
+  EXPECT_TRUE(glob_match("data?", "dataX"));
+  EXPECT_FALSE(glob_match("data?", "data12"));
+  EXPECT_TRUE(glob_match("src/**/*.c", "src/main.c"));
+  EXPECT_TRUE(glob_match("**/test*.py", "src/tests/test_foo.py"));
+  EXPECT_FALSE(glob_match("*.md", "readme.txt"));
+}
+
+void test_fuzz_smoke() {
+  test_fuzz_chunk_deserialize();
+  test_fuzz_compress_decompress();
+  test_fuzz_delta_deserialize();
+  test_fuzz_metadata_from_buf();
+  test_fuzz_delta_signature_deserialize();
+  test_fuzz_glob_match();
+}

tests/test_fuzz_smoke.h

@@ -0,0 +1,6 @@
+#ifndef TEST_FUZZ_SMOKE_H
+#define TEST_FUZZ_SMOKE_H
+
+void test_fuzz_smoke();
+
+#endif

tests/test_metadata.c

@@ -112,7 +112,7 @@ static void test_metadata_send_null() {
 static void test_file_restore_metadata() {
   const char* path = "temp_meta_restore_test.txt";
   const char* content = "test content";
-  EXPECT_TRUE(to_disk(path, content, strlen(content)));
+  EXPECT_TRUE(to_disk(path, content, strlen(content), false, false));
 
   FileMetadata m;
   m.mode = 0644;

tests/test_multiprocessing.c

@@ -1,16 +1,25 @@
 #include "test_multiprocessing.h"
 #include "multiprocessing.h"
 #include "config.h"
+#include "protocol.h"
 #include "queue.h"
 #include "utils.h"
 #include "test_utils.h"
+#include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
+#include <threads.h>
+#include <sys/wait.h>
+#include <unistd.h>
 
 /* Test pipeline_context_sender_create/destroy with valid arguments */
 static void test_sender_create_destroy() {
-  Config* cfg = config_create(str_dup("1.0"), str_dup("/src"), str_dup("/dst"), false, false, false,
-                              false, false, 0, false, 0);
+  Config* cfg = config_create();
   EXPECT_NOT_NULL(cfg);
+  free(cfg->version);
+  cfg->version = str_dup("1.0");
+  cfg->send_directory = str_dup("/src");
+  cfg->receive_root_directory = str_dup("/dst");
 
   Queue* q_scanner = queue_create(5, NULL);
   EXPECT_NOT_NULL(q_scanner);
@@ -32,14 +41,19 @@ static void test_sender_create_destroy() {
 
 /* Test pipeline_context_receiver_create/destroy with valid arguments */
 static void test_receiver_create_destroy() {
-  Config* cfg = config_create(str_dup("2.0"), str_dup("/src"), str_dup("/dst"), true, true, false,
-                              false, false, 0, false, 0);
+  Config* cfg = config_create();
   EXPECT_NOT_NULL(cfg);
+  free(cfg->version);
+  cfg->version = str_dup("2.0");
+  cfg->send_directory = str_dup("/src");
+  cfg->receive_root_directory = str_dup("/dst");
+  cfg->save_to_disk = true;
+  cfg->use_multithreading = true;
 
   Queue* q = queue_create(20, NULL);
   EXPECT_NOT_NULL(q);
 
-  PipelineContextReceiver* ctx = pipeline_context_receiver_create(cfg, q, 42);
+  PipelineContextReceiver* ctx = pipeline_context_receiver_create(cfg, q, 42, NULL);
   EXPECT_NOT_NULL(ctx);
   EXPECT_EQ_STR(ctx->config->version, "2.0");
   EXPECT_EQ_INT(ctx->queue->capacity, 20);
@@ -51,9 +65,12 @@ static void test_receiver_create_destroy() {
 
 /* Test that create handles various queue capacities */
 static void test_sender_queue_capacities() {
-  Config* cfg = config_create(str_dup("3.0"), str_dup("/src"), str_dup("/dst"), false, false, false,
-                              false, false, 0, false, 0);
+  Config* cfg = config_create();
   EXPECT_NOT_NULL(cfg);
+  free(cfg->version);
+  cfg->version = str_dup("3.0");
+  cfg->send_directory = str_dup("/src");
+  cfg->receive_root_directory = str_dup("/dst");
 
   /* Single-element queues */
   Queue* q1 = queue_create(1, NULL);
@@ -67,9 +84,12 @@ static void test_sender_queue_capacities() {
 
 /* Test that create handles zero-capacity queues */
 static void test_sender_zero_capacity() {
-  Config* cfg = config_create(str_dup("4.0"), str_dup("/src"), str_dup("/dst"), false, false, false,
-                              false, false, 0, false, 0);
+  Config* cfg = config_create();
   EXPECT_NOT_NULL(cfg);
+  free(cfg->version);
+  cfg->version = str_dup("4.0");
+  cfg->send_directory = str_dup("/src");
+  cfg->receive_root_directory = str_dup("/dst");
 
   Queue* q1 = queue_create(0, NULL);
   Queue* q2 = queue_create(0, NULL);
@@ -82,20 +102,127 @@ static void test_sender_zero_capacity() {
 
 /* Test receiver with zero file_descriptor */
 static void test_receiver_fd_zero() {
-  Config* cfg = config_create(str_dup("5.0"), str_dup("/src"), str_dup("/dst"), false, false, false,
-                              false, false, 0, false, 0);
+  Config* cfg = config_create();
+  EXPECT_NOT_NULL(cfg);
+  free(cfg->version);
+  cfg->version = str_dup("5.0");
+  cfg->send_directory = str_dup("/src");
+  cfg->receive_root_directory = str_dup("/dst");
   Queue* q = queue_create(5, NULL);
-  PipelineContextReceiver* ctx = pipeline_context_receiver_create(cfg, q, 0);
+  PipelineContextReceiver* ctx = pipeline_context_receiver_create(cfg, q, 0, NULL);
   EXPECT_NOT_NULL(ctx);
   EXPECT_EQ_INT(ctx->file_descriptor, 0);
   EXPECT_FALSE(ctx->receiver_done);
   pipeline_context_receiver_destroy(ctx);
 }
 
+/* Test that receive_thread completes cleanly when sent FINISHED immediately */
+static void test_receive_thread_finished() {
+  Config* cfg = config_create();
+  EXPECT_NOT_NULL(cfg);
+  free(cfg->version);
+  cfg->version = str_dup(PROTOCOL_VERSION);
+  cfg->send_directory = str_dup("/src");
+  cfg->receive_root_directory = str_dup("/tmp/dst");
+  cfg->save_to_disk = true;
+
+  int p[2];
+  EXPECT_EQ_INT(pipe(p), 0);
+  io_set_fds(p[0], p[1]);
+  io_set_bwlimit(0);
+
+  pid_t pid = fork();
+  if (pid == 0) {
+    /* Child: run receive_thread */
+    close(p[1]);
+
+    Queue* q = queue_create(5, file_destroy);
+    EXPECT_NOT_NULL(q);
+    PipelineContextReceiver* ctx = pipeline_context_receiver_create(cfg, q, p[0], NULL);
+    EXPECT_NOT_NULL(ctx);
+
+    int ret = receive_thread(ctx);
+
+    pipeline_context_receiver_destroy(ctx);
+    close(p[0]);
+    _exit(ret == thrd_success ? 0 : 1);
+  } else {
+    /* Parent: send STATUS_FINISHED then STATUS_MANIFEST */
+    close(p[0]);
+
+    /* Send a STATUS_FINISHED to make receive_thread exit cleanly.
+     * receive_thread reads status, sees FINISHED, then exits loop.
+     * After the loop it expects STATUS_MANIFEST check, but we sent
+     * FINISHED so it will just return thrd_success. */
+    send_status(p[1], STATUS_FINISHED);
+
+    close(p[1]);
+
+    int status;
+    waitpid(pid, &status, 0);
+
+    /* Parent must free its own copies of config (child has separate copies) */
+    config_delete(cfg);
+
+    EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0);
+  }
+}
+
+/* Test that write_thread completes cleanly when queue signals done */
+static void test_write_thread_done() {
+  Config* cfg = config_create();
+  EXPECT_NOT_NULL(cfg);
+  free(cfg->version);
+  cfg->version = str_dup(PROTOCOL_VERSION);
+  cfg->send_directory = str_dup("/src");
+  cfg->receive_root_directory = str_dup("/tmp/dst");
+  cfg->save_to_disk = false;
+
+  Queue* q = queue_create(5, file_destroy);
+  EXPECT_NOT_NULL(q);
+
+  PipelineContextReceiver* ctx = pipeline_context_receiver_create(cfg, q, 0, NULL);
+  EXPECT_NOT_NULL(ctx);
+
+  /* Mark receiver as done BEFORE starting the thread so it exits immediately */
+  ctx->receiver_done = true;
+
+  thrd_t writer;
+  int ret = thrd_create(&writer, write_thread, ctx);
+  EXPECT_EQ_INT(ret, thrd_success);
+
+  int result;
+  thrd_join(writer, &result);
+  EXPECT_EQ_INT(result, thrd_success);
+
+  /* Don't call pipeline_context_receiver_destroy because it frees ctx
+   * and write_thread doesn't destroy ctx. Actually looking at the code:
+   * write_thread reads context fields but doesn't free anything.
+   * The caller is responsible for cleanup. So we need to clean up.
+   * But wait - write_thread takes ownership? Let me check...
+   * No, write_thread just processes and returns. The caller frees.
+   *
+   * However, pipeline_context_receiver_destroy will call config_delete
+   * and queue_destroy which would double-free since we created them
+   * in this test. Let me just free the context directly. */
+  mtx_destroy(&ctx->mutex);
+  cnd_destroy(&ctx->condition_not_full);
+  cnd_destroy(&ctx->condition_not_empty);
+  free(ctx);
+
+  /* q and cfg still need cleanup */
+  queue_destroy(q);
+  config_delete(cfg);
+}
+
 void test_multiprocessing() {
   test_sender_create_destroy();
   test_receiver_create_destroy();
   test_sender_queue_capacities();
   test_sender_zero_capacity();
   test_receiver_fd_zero();
+  if (!is_running_under_valgrind()) {
+    test_receive_thread_finished();
+  }
+  test_write_thread_done();
 }

tests/test_property.c

@@ -84,7 +84,7 @@ static void test_property_chunk_roundtrip() {
     for (int i = 0; i < content_len; i++)
       content[i] = (char)(rand() % 256);
 
-    to_disk(path, content, content_len);
+    to_disk(path, content, content_len, false, false);
 
     struct stat st;
     stat(path, &st);

tests/test_robustness.c

@@ -13,7 +13,7 @@
 static void test_chunk_deserialize_truncated() {
   char* path = "test_rob_trunc.txt";
   char* content = "hello";
-  to_disk(path, content, strlen(content));
+  to_disk(path, content, strlen(content), false, false);
 
   struct stat st;
   stat(path, &st);

tests/test_scanner.c

@@ -7,7 +7,7 @@
 #include <unistd.h>
 
 static void create_test_file(const char* path, const char* content) {
-  (void)to_disk(path, content, strlen(content));
+  (void)to_disk(path, content, strlen(content), false, false);
 }
 
 static void test_scanner_single_file() {
@@ -18,8 +18,8 @@ static void test_scanner_single_file() {
   EXPECT_EQ_INT(mkdir(dir, 0755), 0);
   create_test_file(file1, content1);
 
-  DirectoryScanner* scanner =
-      directory_scanner_create((char*)dir, false, 0, NULL, 0, NULL, 0, 0, 0, 0);
+  DirectoryScanner* scanner = directory_scanner_create((char*)dir, false, 0, NULL, 0, NULL, 0, 0, 0,
+                                                       0, false, false, false, false);
   EXPECT_NOT_NULL(scanner);
 
   Chunk* chunk = directory_scanner_next(scanner);
@@ -47,8 +47,8 @@ static void test_scanner_multiple_files() {
   create_test_file(file1, content1);
   create_test_file(file2, content2);
 
-  DirectoryScanner* scanner =
-      directory_scanner_create((char*)dir, false, 0, NULL, 0, NULL, 0, 0, 0, 0);
+  DirectoryScanner* scanner = directory_scanner_create((char*)dir, false, 0, NULL, 0, NULL, 0, 0, 0,
+                                                       0, false, false, false, false);
   EXPECT_NOT_NULL(scanner);
 
   const Chunk* chunk = directory_scanner_next(scanner);
@@ -87,8 +87,8 @@ static void test_scanner_subdirectory() {
   create_test_file(root_file, content);
   create_test_file(sub_file, content);
 
-  DirectoryScanner* scanner =
-      directory_scanner_create((char*)root, false, 0, NULL, 0, NULL, 0, 0, 0, 0);
+  DirectoryScanner* scanner = directory_scanner_create((char*)root, false, 0, NULL, 0, NULL, 0, 0,
+                                                       0, 0, false, false, false, false);
   EXPECT_NOT_NULL(scanner);
 
   int total_files = 0;
@@ -111,8 +111,8 @@ static void test_scanner_empty_directory() {
 
   EXPECT_EQ_INT(mkdir(dir, 0755), 0);
 
-  DirectoryScanner* scanner =
-      directory_scanner_create((char*)dir, false, 0, NULL, 0, NULL, 0, 0, 0, 0);
+  DirectoryScanner* scanner = directory_scanner_create((char*)dir, false, 0, NULL, 0, NULL, 0, 0, 0,
+                                                       0, false, false, false, false);
   EXPECT_NOT_NULL(scanner);
 
   const Chunk* chunk = directory_scanner_next(scanner);
@@ -135,8 +135,8 @@ static void test_scanner_exclude_pattern() {
   create_test_file(f_tmp, content);
 
   char* exclude[] = {"*.tmp"};
-  DirectoryScanner* scanner =
-      directory_scanner_create((char*)dir, false, 0, exclude, 1, NULL, 0, 0, 0, 0);
+  DirectoryScanner* scanner = directory_scanner_create((char*)dir, false, 0, exclude, 1, NULL, 0, 0,
+                                                       0, 0, false, false, false, false);
   EXPECT_NOT_NULL(scanner);
 
   Chunk* chunk = directory_scanner_next(scanner);
@@ -168,8 +168,8 @@ static void test_scanner_exclude_subdirectory() {
   create_test_file(sub_tmp, content);
 
   char* exclude[] = {"*.tmp"};
-  DirectoryScanner* scanner =
-      directory_scanner_create((char*)root, false, 0, exclude, 1, NULL, 0, 0, 0, 0);
+  DirectoryScanner* scanner = directory_scanner_create((char*)root, false, 0, exclude, 1, NULL, 0,
+                                                       0, 0, 0, false, false, false, false);
   EXPECT_NOT_NULL(scanner);
 
   int total = 0;
@@ -206,8 +206,8 @@ static void test_scanner_include_and_exclude() {
 
   char* exclude[] = {"*.bak"};
   char* include[] = {"*.txt", "*.log"};
-  DirectoryScanner* scanner =
-      directory_scanner_create((char*)dir, false, 0, exclude, 1, include, 2, 0, 0, 0);
+  DirectoryScanner* scanner = directory_scanner_create((char*)dir, false, 0, exclude, 1, include, 2,
+                                                       0, 0, 0, false, false, false, false);
   EXPECT_NOT_NULL(scanner);
 
   Chunk* chunk = directory_scanner_next(scanner);
@@ -243,8 +243,8 @@ static void test_scanner_max_size() {
   create_test_file(large, "this_content_is_longer_than_ten_chars");
 
   /* max_size = 10 — only files <= 10 bytes */
-  DirectoryScanner* scanner =
-      directory_scanner_create((char*)dir, false, 0, NULL, 0, NULL, 0, 10, 0, 0);
+  DirectoryScanner* scanner = directory_scanner_create((char*)dir, false, 0, NULL, 0, NULL, 0, 10,
+                                                       0, 0, false, false, false, false);
   EXPECT_NOT_NULL(scanner);
 
   Chunk* chunk = directory_scanner_next(scanner);
@@ -271,8 +271,8 @@ static void test_scanner_min_size() {
   create_test_file(data_f, "some content here");
 
   /* min_size = 1 — only files >= 1 byte */
-  DirectoryScanner* scanner =
-      directory_scanner_create((char*)dir, false, 0, NULL, 0, NULL, 0, 0, 1, 0);
+  DirectoryScanner* scanner = directory_scanner_create((char*)dir, false, 0, NULL, 0, NULL, 0, 0, 1,
+                                                       0, false, false, false, false);
   EXPECT_NOT_NULL(scanner);
 
   Chunk* chunk = directory_scanner_next(scanner);
@@ -301,8 +301,8 @@ static void test_scanner_size_range() {
   create_test_file(huge, "this is a much larger file for testing size filters");
 
   /* Only files between 3 and 20 bytes */
-  DirectoryScanner* scanner =
-      directory_scanner_create((char*)dir, false, 0, NULL, 0, NULL, 0, 20, 3, 0);
+  DirectoryScanner* scanner = directory_scanner_create((char*)dir, false, 0, NULL, 0, NULL, 0, 20,
+                                                       3, 0, false, false, false, false);
   EXPECT_NOT_NULL(scanner);
 
   Chunk* chunk = directory_scanner_next(scanner);
@@ -337,8 +337,8 @@ static void test_scanner_mixed_patterns() {
   /* Exclude *.bak, include *.txt, min_size=3, max_size=10 */
   char* exclude[] = {"*.bak"};
   char* include[] = {"*.txt"};
-  DirectoryScanner* scanner =
-      directory_scanner_create((char*)dir, false, 0, exclude, 1, include, 1, 10, 3, 0);
+  DirectoryScanner* scanner = directory_scanner_create((char*)dir, false, 0, exclude, 1, include, 1,
+                                                       10, 3, 0, false, false, false, false);
   EXPECT_NOT_NULL(scanner);
 
   Chunk* chunk = directory_scanner_next(scanner);
@@ -368,8 +368,8 @@ static void test_scanner_no_patterns() {
   create_test_file(f1, "first");
   create_test_file(f2, "second");
 
-  DirectoryScanner* scanner =
-      directory_scanner_create((char*)dir, false, 0, NULL, 0, NULL, 0, 0, 0, 0);
+  DirectoryScanner* scanner = directory_scanner_create((char*)dir, false, 0, NULL, 0, NULL, 0, 0, 0,
+                                                       0, false, false, false, false);
   EXPECT_NOT_NULL(scanner);
 
   Chunk* chunk = directory_scanner_next(scanner);

tests/test_server.c

@@ -0,0 +1,180 @@
+#include "test_server.h"
+#include "config.h"
+#include "file.h"
+#include "protocol.h"
+#include "test_utils.h"
+#include "utils.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+/* Include server.c but rename main to avoid conflict with test runner's main */
+#define main server_main_
+#define FASTSYNC_SERVER_AS_LIB
+#include "server.c"
+#undef main
+
+/* Test receive_files with immediate FINISHED status */
+static void test_receive_files_finished() {
+  Config* cfg = config_create();
+  EXPECT_NOT_NULL(cfg);
+  free(cfg->version);
+  cfg->version = str_dup(PROTOCOL_VERSION);
+  cfg->send_directory = str_dup("/src");
+  cfg->receive_root_directory = str_dup("/tmp/dst");
+
+  int p[2];
+  EXPECT_EQ_INT(socketpair(AF_UNIX, SOCK_STREAM, 0, p), 0);
+  io_set_fds(p[0], p[1]);
+  io_set_bwlimit(0);
+
+  pid_t pid = fork();
+  if (pid == 0) {
+    /* Child: use p[0] for both read and write */
+    close(p[1]);
+    io_set_fds(p[0], p[0]);
+    int ret = receive_files(cfg, p[0]);
+    close(p[0]);
+    config_delete(cfg);
+    _exit(ret == 0 ? 0 : 1);
+  } else {
+    /* Parent: use p[1] for both read and write */
+    close(p[0]);
+    io_set_fds(p[1], p[1]);
+    send_status(p[1], STATUS_FINISHED);
+    /* receive_files expects an initial status, then loops.
+     * If we send STATUS_FINISHED first, it won't enter the loop body
+     * (status == STATUS_FINISHED doesn't match any case).
+     * After the loop, it checks if status == STATUS_FINISHED -> yes.
+     * Then sends STATUS_OK and returns 0. */
+    /* receive_files will send STATUS_OK back, read it */
+    Status resp;
+    receive_status(p[1], &resp);
+
+    int status;
+    waitpid(pid, &status, 0);
+
+    close(p[1]);
+
+    config_delete(cfg);
+
+    EXPECT_EQ_INT(resp, STATUS_OK);
+    EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0);
+  }
+}
+
+/* Test receive_files with STATUS_NEXT + file data */
+static void test_receive_files_single_file() {
+  const char* content = "Hello from server test!";
+  size_t len = strlen(content);
+
+  Config* cfg = config_create();
+  EXPECT_NOT_NULL(cfg);
+  free(cfg->version);
+  cfg->version = str_dup(PROTOCOL_VERSION);
+  cfg->send_directory = str_dup("/src");
+  cfg->receive_root_directory = str_dup("/tmp/dst");
+
+  int p[2];
+  EXPECT_EQ_INT(socketpair(AF_UNIX, SOCK_STREAM, 0, p), 0);
+  io_set_fds(p[0], p[1]);
+  io_set_bwlimit(0);
+
+  pid_t pid = fork();
+  if (pid == 0) {
+    /* Child: use p[0] for both read and write */
+    close(p[1]);
+    io_set_fds(p[0], p[0]);
+    int ret = receive_files(cfg, p[0]);
+    close(p[0]);
+    config_delete(cfg);
+    _exit(ret == 0 ? 0 : 1);
+  } else {
+    /* Parent: use p[1] for both read and write */
+    close(p[0]);
+    io_set_fds(p[1], p[1]);
+
+    /* Send initial status = STATUS_NEXT */
+    send_status(p[1], STATUS_NEXT);
+
+    /* Now send the file data */
+    File* file = file_create("test_server_file.txt");
+    EXPECT_NOT_NULL(file);
+    file->data->data = malloc(len);
+    EXPECT_NOT_NULL(file->data->data);
+    memcpy(file->data->data, content, len);
+    file->data->size = len;
+
+    /* Send path, then data (no metadata since config has use_metadata=false) */
+    send_str(p[1], file->path);
+    send_data(p[1], file->data);
+
+    file_destroy(file);
+
+    /* Now send FINISHED to complete */
+    send_status(p[1], STATUS_FINISHED);
+    Status resp;
+    receive_status(p[1], &resp);
+
+    int status;
+    waitpid(pid, &status, 0);
+
+    close(p[1]);
+
+    config_delete(cfg);
+
+    EXPECT_EQ_INT(resp, STATUS_OK);
+    EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0);
+  }
+}
+
+/* Test receive_files with STATUS_ABORT */
+static void test_receive_files_abort() {
+  Config* cfg = config_create();
+  EXPECT_NOT_NULL(cfg);
+  free(cfg->version);
+  cfg->version = str_dup(PROTOCOL_VERSION);
+  cfg->send_directory = str_dup("/src");
+  cfg->receive_root_directory = str_dup("/tmp/dst");
+
+  int p[2];
+  EXPECT_EQ_INT(socketpair(AF_UNIX, SOCK_STREAM, 0, p), 0);
+  io_set_fds(p[0], p[1]);
+  io_set_bwlimit(0);
+
+  pid_t pid = fork();
+  if (pid == 0) {
+    close(p[1]);
+    io_set_fds(p[0], p[0]);
+    int ret = receive_files(cfg, p[0]);
+    close(p[0]);
+    config_delete(cfg);
+    /* Should return -1 on abort */
+    _exit(ret == -1 ? 0 : 1);
+  } else {
+    close(p[0]);
+    io_set_fds(p[1], p[1]);
+    /* Send STATUS_ABORT */
+    send_status(p[1], STATUS_ABORT);
+
+    int status;
+    waitpid(pid, &status, 0);
+
+    close(p[1]);
+
+    config_delete(cfg);
+
+    EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0);
+  }
+}
+
+void test_server() {
+  if (!is_running_under_valgrind()) {
+    test_receive_files_finished();
+    test_receive_files_single_file();
+    test_receive_files_abort();
+  }
+}

tests/test_server.h

@@ -0,0 +1,6 @@
+#ifndef TEST_SERVER_H
+#define TEST_SERVER_H
+
+void test_server();
+
+#endif

tests/test_transport_tcp.c

@@ -1,6 +1,8 @@
 #include "test_transport_tcp.h"
+#include "protocol.h"
 #include "test_utils.h"
 #include "transport_tcp.h"
+#include <string.h>
 #include <unistd.h>
 
 static void test_server_create_ephemeral() {
@@ -21,8 +23,8 @@ static void test_server_delete_null() {
 static void test_client_create() {
   Client* c = client_create();
   EXPECT_NOT_NULL(c);
-  EXPECT_TRUE(c->file_descriptor >= 0);
-  EXPECT_EQ_INT(c->address.sin_family, AF_INET);
+  EXPECT_TRUE(c->file_descriptor == -1);
+  EXPECT_EQ_INT(c->address.ss_family, 0);
   EXPECT_EQ_INT(c->ssh_child_pid, -1);
   EXPECT_NULL(c->ssl);
   EXPECT_NULL(c->ssl_ctx);
@@ -35,9 +37,66 @@ static void test_client_delete_null() {
   client_delete(c);
 }
 
+/* Test tcp_set_timeouts with valid values */
+static void test_tcp_set_timeouts() {
+  /* Just verify the function doesn't crash with edge cases */
+  tcp_set_timeouts(0, 0);   /* zero means "don't change" */
+  tcp_set_timeouts(60, 20); /* normal values */
+  tcp_set_timeouts(-1, -1); /* negative means "don't change" */
+  /* If we got here without crashing, the test passes */
+  EXPECT_TRUE(true);
+}
+
+/* Test client_connect with an invalid host (should fail gracefully) */
+static void test_client_connect_invalid_host() {
+  Client* c = client_create();
+  EXPECT_NOT_NULL(c);
+
+  /* Use a non-routable IP that will fail connect quickly */
+  bool ok = client_connect(c, "10.255.255.1", 9999);
+  EXPECT_FALSE(ok);
+
+  client_disconnect(c);
+  client_delete(c);
+}
+
+/* Test server_create with a specific port */
+static void test_server_create_specific_port() {
+  /* Port 0 = ephemeral, but try 0 and verify bind works */
+  Server* s = server_create(0);
+  EXPECT_NOT_NULL(s);
+  EXPECT_TRUE(s->file_descriptor >= 0);
+  server_delete(&s);
+  EXPECT_NULL(s);
+}
+
+/* Test server_create with invalid port (0 is valid for ephemeral) */
+static void test_server_delete_double() {
+  Server* s = server_create(0);
+  EXPECT_NOT_NULL(s);
+  server_delete(&s);
+  EXPECT_NULL(s);
+  /* Deleting again should be safe - pointer is already NULL */
+  server_delete(&s);
+  EXPECT_NULL(s);
+}
+
+/* Test client_disconnect followed by client_delete */
+static void test_client_disconnect_delete() {
+  Client* c = client_create();
+  EXPECT_NOT_NULL(c);
+  client_disconnect(c);
+  client_delete(c);
+}
+
 void test_transport_tcp() {
   test_server_create_ephemeral();
   test_server_delete_null();
   test_client_create();
   test_client_delete_null();
+  test_tcp_set_timeouts();
+  test_client_connect_invalid_host();
+  test_server_create_specific_port();
+  test_server_delete_double();
+  test_client_disconnect_delete();
 }

tests/test_transport_tls.c

@@ -1,7 +1,10 @@
 #include "test_transport_tls.h"
+#include "protocol.h"
 #include "test_utils.h"
 #include "transport_tcp.h"
 #include "transport_tls.h"
+#include <string.h>
+#include <unistd.h>
 
 static void test_tls_global_init() {
   bool ok = tls_global_init();
@@ -18,7 +21,41 @@ static void test_server_create_tls_without_certs() {
   EXPECT_NULL(s);
 }
 
+/* Test client_connect_tls with no server listening (should fail gracefully) */
+static void test_client_connect_tls_fail() {
+  /* Create a client to localhost on a high port with no server */
+  Client* c = client_create();
+  EXPECT_NOT_NULL(c);
+
+  /* connect to localhost:1 (no server) - should fail as connect() fails first */
+  bool ok = client_connect_tls(c, "127.0.0.1", 1, NULL, NULL, NULL);
+  EXPECT_FALSE(ok);
+
+  /* Note: client_connect_tls internally calls connect() which sets up the socket.
+   * On failure it returns false but does NOT close the socket - we need to
+   * disconnect/delete the client. The socket fd may be in an undefined state
+   * after a failed connect, so we just call client_delete which closes it. */
+  client_disconnect(c);
+  client_delete(c);
+}
+
+/* Test server_create_tls with missing cert file paths (should still create ctx without certs) */
+static void test_server_create_tls_empty_certs() {
+  Server* s = server_create(0);
+  EXPECT_NOT_NULL(s);
+
+  /* Empty string paths - SSL_CTX_use_certificate_file will fail, but function returns false */
+  bool ok = server_create_tls(s, "", "", NULL);
+  EXPECT_FALSE(ok);
+  EXPECT_NULL(s->ssl_ctx);
+
+  server_delete(&s);
+  EXPECT_NULL(s);
+}
+
 void test_transport_tls() {
   test_tls_global_init();
   test_server_create_tls_without_certs();
+  test_client_connect_tls_fail();
+  test_server_create_tls_empty_certs();
 }