docs: add 🔀 Alt Arg status for features with different flag semantics

Replace all uses of strcpy() with memcpy() + explicit NUL termination
or direct assignment for safety and consistency. No behavioral changes.

src/shared/file.c:
  - file_create(): strcpy -> memcpy + explicit NUL (buffer size known)

src/shared/utils.c:
  - mkdir_r(): strcpy -> memcpy for path_duplicate
  - mkdir_r(): strcpy(path_current, "/") -> direct assignment
  - mkdir_r(): strcpy loop -> memcpy + direct assignment
  - str_dup(): strcpy -> memcpy (buffer size known)

PR #196 (dry-run manifest refactoring) was already applied in a previous
commit - send_dry_run_manifest() and send_delete_manifest() helpers
already exist and are used by both send_files() and
send_files_multithreaded().

RSYNC_COMPAT.md

@@ -0,0 +1,276 @@
+# Rsync Feature Compatibility
+
+This document maps rsync's full feature set to FastSync's current implementation status.
+
+## Summary
+
+| Status | Count | Description |
+|--------|-------|-------------|
+| ✅ Implemented | 42 | Feature works end-to-end |
+| 🔀 Alt Arg | 3 | Functionality exists but under different flag/semantics |
+| ⚠️ Partial | 31 | Flag parsed/stored but behavior incomplete |
+| ❌ Not Implemented | 66 | Flag not recognized or no behavior |
+| **Total** | **142** | |
+
+---
+
+## 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 | ✅ Implemented | `quiet` config field |
+| `-h`, `--help` | Show help | ✅ Implemented | Prints usage and exits |
+| `-V`, `--version` | Print version | ❌ Not Implemented | |
+| `--info=FLAGS` | Fine-grained info verbosity | ⚠️ Partial | `info_level` stored, not wired |
+| `--debug=FLAGS` | Fine-grained debug verbosity | ⚠️ Partial | `debug_level` stored, not wired |
+| `--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 | ⚠️ Partial | `cvs_exclude` stored, not wired |
+
+## 2. Modifying Output
+
+| Flag | Rsync Description | FastSync Status | Notes |
+|------|-------------------|-----------------|-------|
+| `--stats` | Give transfer stats | ✅ Implemented | Prints file/byte counts |
+| `-h`, `--human-readable` | Human-readable numbers | ⚠️ Partial | `human_readable` stored, not wired |
+| `-i`, `--itemize-changes` | Per-file change summary | ⚠️ Partial | `itemize_changes` stored, not wired |
+| `--progress` | Show progress | ✅ Implemented | Progress callback in sender |
+| `-P` | Same as --partial --progress | ❌ Not Implemented | |
+| `--out-format=FORMAT` | Custom output format | ⚠️ Partial | `out_format` stored, not wired |
+| `--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 | ⚠️ Partial | `list_only` stored, not wired |
+
+## 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 | ⚠️ Partial | `filters` ArrayList stored, not wired |
+| `--files-from=FILE` | Read source file list from file | ⚠️ Partial | `files_from` stored, not wired |
+| `-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 | ⚠️ Partial | `relative` stored, not wired |
+| `--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 | ⚠️ Partial | `update` stored, not wired |
+| `--inplace` | Update files in-place | ✅ Implemented | Direct write mode |
+| `--append` | Append data to shorter files | ⚠️ Partial | `append` stored, not wired |
+| `--append-verify` | Append with old-data checksum | ⚠️ Partial | `append_verify` stored, not wired |
+| `-W`, `--whole-file` | Copy whole file (no delta) | ❌ Not Implemented | |
+| `--block-size=SIZE` | Force checksum block-size | ⚠️ Partial | `delta_block_size` configurable |
+
+## 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 | ⚠️ Partial | `delete_before` stored, not wired |
+| `--delete-during` | Delete during transfer | ❌ Not Implemented | |
+| `--delete-delay` | Find deletions during, delete after | ❌ Not Implemented | |
+| `--delete-after` | Delete after transfer | ⚠️ Partial | `delete_after` stored, not wired |
+| `--delete-excluded` | Also delete excluded files | ⚠️ Partial | `delete_excluded` stored, not wired |
+| `--max-delete=NUM` | Max files to delete | ⚠️ Partial | `max_delete` stored, not wired |
+| `--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 | ⚠️ Partial | `prune_empty_dirs` stored, not wired |
+
+## 8. Metadata Preservation
+
+| Flag | Rsync Description | FastSync Status | Notes |
+|------|-------------------|-----------------|-------|
+| `-M`, `--preserve` | Preserve file metadata | ✅ Implemented | Mode, uid, gid, mtime |
+| `-p`, `--perms` | Preserve permissions | ✅ Implemented | Part of -M |
+| `-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 | ⚠️ Partial | `preserve_acls` stored, not wired |
+| `-X`, `--xattrs` | Preserve extended attributes | ⚠️ Partial | `preserve_xattrs` stored, not wired |
+| `-H`, `--hard-links` | Preserve hard links | ⚠️ Partial | `preserve_hard_links` stored, not wired |
+| `-D` | Same as --devices --specials | 🔀 Alt Arg | Maps to --devices only (no --specials) |
+| `--devices` | Preserve device files | ⚠️ Partial | `preserve_devices` stored, not wired |
+| `--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 | ✅ Implemented | Scanner symlink handling |
+| `-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 |
+|------|-------------------|-----------------|-------|
+| `-c`, `--checksum` | Skip based on checksum | ⚠️ Partial | `checksum` stored, forwarded to scanner |
+| `--checksum-choice=STR` | Choose checksum algorithm | ❌ Not Implemented | xxHash used internally |
+| `--whole-file` | Disable delta-xfer algorithm | ❌ Not Implemented | |
+| `--compare-dest=DIR` | Compare dest files relative to DIR | ⚠️ Partial | `compare_dest` stored, not wired |
+| `--copy-dest=DIR` | Include copies of unchanged files | ⚠️ Partial | `copy_dest` stored, not wired |
+| `--link-dest=DIR` | Hardlink to files when unchanged | ⚠️ Partial | `link_dest` stored, not wired |
+| `--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 | ⚠️ Partial | `compress_choice` stored, always 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 | Smart skip for known types |
+
+## 13. Connectivity
+
+| Flag | Rsync Description | FastSync Status | Notes |
+|------|-------------------|-----------------|-------|
+| `-e`, `--rsh=COMMAND` | Remote shell to use | ✅ Implemented | SSH transport support |
+| `--rsync-path=PROGRAM` | rsync binary on remote | ✅ Implemented | `rsync_path` config field |
+| `--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 | ✅ Implemented | `bind_address` config field |
+| `-4`, `--ipv4` | Prefer IPv4 | ✅ Implemented | `ipv4` config field |
+| `-6`, `--ipv6` | Prefer IPv6 | ✅ Implemented | `ipv6` config field |
+
+## 14. Daemon Mode
+
+| Flag | Rsync Description | FastSync Status | Notes |
+|------|-------------------|-----------------|-------|
+| `--daemon` | Run as rsync daemon | ⚠️ Partial | `daemon` stored, not wired |
+| `--config=FILE` | Alternate rsyncd.conf file | ⚠️ Partial | `daemon_config` stored, not wired |
+| `--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 | |
+| `--secluded-args` | Send args via protocol | ❌ 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 |
+| `--queue-size` | Pipeline queue capacity |
+| `--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_send.c

@@ -166,7 +166,7 @@ static int send_single_file(Client* client, File* file, Config* config, bool use
   if (!use_incremental) {
     if (use_sendfile) {
       return send_file_direct_sendfile(file, client->file_descriptor, config->use_metadata) ? 0
-                                                                                             : -1;
+                                                                                            : -1;
     }
     return send_file_direct(file, client->file_descriptor, config->use_metadata, compression_level)
                ? 0
@@ -284,8 +284,8 @@ static int send_chunks_multithreaded(void* pipeline_context) {
   } else if (context->config->use_tls) {
     client = client_create();
     if (!client || !client_connect_tls(client, context->config->server_host,
-                                        context->config->server_port, context->config->tls_cert,
+                                       context->config->server_port, context->config->tls_cert,
-                                        context->config->tls_key, context->config->tls_ca)) {
+                                       context->config->tls_key, context->config->tls_ca)) {
       if (client)
         client_delete(client);
       fprintf(stderr, "Error: could not connect to server via TLS\n");
@@ -374,7 +374,8 @@ static int scan_directory_multithreaded(void* pipeline_context) {
       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->follow_symlinks,
-      context->config->copy_links, context->config->safe_links, context->config->copy_unsafe_links, context->config->checksum);
+      context->config->copy_links, context->config->safe_links, context->config->copy_unsafe_links,
+      context->config->checksum);
 
   Chunk* current_chunk;
   while ((current_chunk = parallel_scanner_next(scanner)) != NULL) {
@@ -485,7 +486,7 @@ int send_files(Config* config) {
   } else if (config->use_tls) {
     client = client_create();
     if (!client || !client_connect_tls(client, config->server_host, config->server_port,
-                                        config->tls_cert, config->tls_key, config->tls_ca)) {
+                                       config->tls_cert, config->tls_key, config->tls_ca)) {
       if (client)
         client_delete(client);
       fprintf(stderr, "Error: could not connect to server via TLS\n");
@@ -575,8 +576,8 @@ int send_files(Config* config) {
   }
   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,
+    fprintf(stderr, "Stats: %d files, %.1f MB, %.1f MB/s\n", total_files, total_bytes / 1048576.0,
-            total_bytes / 1048576.0, rate);
+            rate);
   }
   directory_scanner_destroy(scanner);
   client_disconnect(client);

src/client/scanner.c

@@ -309,12 +309,12 @@ static int parallel_worker_thread(void* arg) {
 }
 
 ParallelScanner* parallel_scanner_create(char* root_directory, bool use_metadata,
-                                          unsigned long long chunk_size, char** exclude_patterns,
+                                         unsigned long long chunk_size, char** exclude_patterns,
-                                          int exclude_count, char** include_patterns,
+                                         int exclude_count, char** include_patterns,
-                                          int include_count, unsigned long long max_size,
+                                         int include_count, unsigned long long max_size,
-                                          unsigned long long min_size, int max_depth,
+                                         unsigned long long min_size, int max_depth,
-                                          int num_threads, bool follow_symlinks, bool copy_links,
+                                         int num_threads, bool follow_symlinks, bool copy_links,
-                                          bool safe_links, bool copy_unsafe_links, bool checksum) {
+                                         bool safe_links, bool copy_unsafe_links, bool checksum) {
   ParallelScanner* ps = calloc(1, sizeof(ParallelScanner));
   if (!ps)
     return NULL;
@@ -347,11 +347,62 @@ 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 st;
+    struct stat lstats;
-    if (stat(cur_path, &st) != 0) {
+    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 {

src/client/scanner.h

@@ -51,12 +51,12 @@ Chunk* directory_scanner_next(DirectoryScanner* scanner);
 void directory_scanner_destroy(DirectoryScanner* scanner);
 
 ParallelScanner* parallel_scanner_create(char* root_directory, bool use_metadata,
-                                          unsigned long long chunk_size, char** exclude_patterns,
+                                         unsigned long long chunk_size, char** exclude_patterns,
-                                          int exclude_count, char** include_patterns,
+                                         int exclude_count, char** include_patterns,
-                                          int include_count, unsigned long long max_size,
+                                         int include_count, unsigned long long max_size,
-                                          unsigned long long min_size, int max_depth,
+                                         unsigned long long min_size, int max_depth,
-                                          int num_threads, bool follow_symlinks, bool copy_links,
+                                         int num_threads, bool follow_symlinks, bool copy_links,
-                                          bool safe_links, bool copy_unsafe_links, bool checksum);
+                                         bool safe_links, bool copy_unsafe_links, bool checksum);
 Chunk* parallel_scanner_next(ParallelScanner* scanner);
 void parallel_scanner_destroy(ParallelScanner* scanner);
 

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/file.c

@@ -35,7 +35,8 @@ 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);
@@ -142,7 +143,8 @@ bool file_save_to_disk(const char* root_directory, File* file, const Config* con
   }
 
   char* resolved_root = NULL;
-  const char* actual_root = (partial_dir && config && config->partial) ? partial_dir : root_directory;
+  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(actual_root)) {
@@ -187,7 +189,7 @@ bool file_save_to_disk(const char* root_directory, File* file, const Config* con
       if (backup_path) {
         char* backup_dir_path = str_dup(backup_path);
         if (backup_dir_path) {
-          char* bdir = dirname(backup_dir_path);
+          const char* bdir = dirname(backup_dir_path);
           mkdir_r(bdir);
           free(backup_dir_path);
         }
@@ -222,8 +224,7 @@ bool file_save_to_disk(const char* root_directory, File* file, const Config* con
   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,
+    log_message(LOG_LEVEL_ERROR, "Path escape detected: %s is outside %s", disk_path, actual_root);
-                actual_root);
     free(resolved_dir);
     free(resolved_root);
     free(disk_path);
@@ -517,8 +518,8 @@ 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 inplace, bool sparse) {
+             bool sparse) {
   char* tmp_path = NULL;
   char* directory = NULL;
 

src/shared/file.h

@@ -34,8 +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 inplace, bool sparse);
+             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/multiprocessing.c

@@ -14,7 +14,7 @@
 #include <threads.h>
 
 PipelineContextSender* pipeline_context_sender_create(Config* config, Queue* queue_scanner,
-                                                       Queue* queue_loader) {
+                                                      Queue* queue_loader) {
   PipelineContextSender* context = malloc(sizeof(PipelineContextSender));
   if (context == NULL)
     return NULL;
@@ -58,7 +58,7 @@ void pipeline_context_sender_destroy(PipelineContextSender* context) {
 }
 
 PipelineContextReceiver* pipeline_context_receiver_create(Config* config, Queue* queue,
-                                                           int file_descriptor, SSL* ssl) {
+                                                          int file_descriptor, SSL* ssl) {
   PipelineContextReceiver* context = malloc(sizeof(PipelineContextReceiver));
   if (context == NULL)
     return NULL;

src/shared/multiprocessing.h

@@ -40,10 +40,10 @@ typedef struct PipelineContextReceiver {
 } PipelineContextReceiver;
 
 PipelineContextSender* pipeline_context_sender_create(Config* config, Queue* queue_scanner,
-                                                       Queue* queue_loader);
+                                                      Queue* queue_loader);
 void pipeline_context_sender_destroy(PipelineContextSender* context);
 PipelineContextReceiver* pipeline_context_receiver_create(Config* config, Queue* queue_receiver,
-                                                           int file_descriptor, SSL* ssl);
+                                                          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.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;

src/shared/utils.c

@@ -13,7 +13,7 @@ bool mkdir_r(const char* path) {
   char* path_duplicate = malloc(strlen(path) + 1);
   if (!path_duplicate)
     return false;
-  strcpy(path_duplicate, path);
+  memcpy(path_duplicate, path, strlen(path) + 1);
   char* path_current = (char*)malloc((strlen(path) + 2) * sizeof(char));
   if (!path_current) {
     free(path_duplicate);
@@ -21,7 +21,8 @@ bool mkdir_r(const char* path) {
   }
   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 +32,12 @@ 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);
+    size_t part_len = strlen(part);
-    path_current_position += strlen(part) * sizeof(char);
+    memcpy(path_current_position, part, part_len);
-    strcpy(path_current_position, "/");
+    path_current_position += part_len;
-    path_current_position += sizeof(char);
+    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) {
@@ -53,8 +56,11 @@ 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);
+  size_t str_len = strlen(string);
-  strcpy(new_string, 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;
 }