feat(p5-socket): --address, -4/-6, --sockopts, server bind options

src/client/client_cli.c

@@ -148,6 +148,24 @@ static int set_compression_threads_option(int* dest, const char* value) {
   return 0;
 }
 
+/* Parse and validate --sockopts=OPTIONS into the config.  The strict allowlist
+ * (config_sockopts_parse) rejects an unknown option name or an invalid value
+ * up front, so a typo never silently disables a socket option. */
+static int set_sockopts_option(Config* config, const char* value) {
+  SockOptEntry* entries = NULL;
+  int count = 0;
+  if (config_sockopts_parse(value, &entries, &count) != 0) {
+    log_message(LOG_LEVEL_ERROR,
+                "--sockopts must be a comma-separated OPT=VAL list of supported options "
+                "(TCP_NODELAY, SO_KEEPALIVE, SO_RCVBUF, SO_SNDBUF, SO_REUSEADDR)");
+    return -1;
+  }
+  free(config->sockopts);
+  config->sockopt_count = count;
+  config->sockopts = entries;
+  return 0;
+}
+
 /* Parse a string as a non-negative integer into *dest. Returns 0 on success, -1 on error. */
 static int set_nonneg_int_option(int* dest, const char* value, const char* option_name) {
   if (!parse_nonneg_int(value, dest)) {
@@ -530,6 +548,9 @@ static const OptionEntry OPTION_TABLE[] = {
     {"--timeout", NULL, OPT_POS_INT, offsetof(Config, timeout)},
     {"--contimeout", NULL, OPT_POS_INT, offsetof(Config, contimeout)},
     {"--max-depth", NULL, OPT_NONNEG_INT, offsetof(Config, max_depth)},
+    {"--address", NULL, OPT_STRING, offsetof(Config, address)},
+    {"--ipv4", "-4", OPT_FLAG, offsetof(Config, ipv4)},
+    {"--ipv6", "-6", OPT_FLAG, offsetof(Config, ipv6)},
 
     {"--max-size", NULL, OPT_ULL, offsetof(Config, max_size)},
     {"--min-size", NULL, OPT_ULL, offsetof(Config, min_size)},
@@ -1125,6 +1146,16 @@ int parse_args(Config* config, int argc, char* argv[], int* positional_args,
       }
       if (set_checksum_seed(config, argv[++i]) != 0)
         return -1;
+    } else if (strncmp(argv[i], "--sockopts=", 11) == 0) {
+      if (set_sockopts_option(config, argv[i] + 11) != 0)
+        return -1;
+    } else if (opt_is(argv[i], "--sockopts", NULL)) {
+      if (i + 1 >= argc) {
+        log_message(LOG_LEVEL_ERROR, "missing argument for --sockopts");
+        return -1;
+      }
+      if (set_sockopts_option(config, argv[++i]) != 0)
+        return -1;
     } else if (strncmp(argv[i], "--compare-dest=", 15) == 0) {
       if (set_basis_dest_option(config, BASIS_DEST_COMPARE, argv[i] + 15, "--compare-dest") != 0)
         return -1;

src/client/client_send.c

@@ -373,12 +373,21 @@ static Client* connect_transfer_client(const Config* config) {
   Client* client = client_create();
   if (!client)
     return NULL;
+  /* Socket/connect concerns that never cross the wire: --address (source bind),
+   * -4/-6 (family pinning), and --sockopts.  Passed straight to the TCP layer. */
+  TcpConnectOptions connect_opts;
+  connect_opts.bind_address = config->address;
+  connect_opts.family = tcp_connect_family(config->ipv4, config->ipv6);
+  connect_opts.sockopts = config->sockopts;
+  connect_opts.sockopt_count = config->sockopt_count;
   bool connected;
   if (config->use_tls) {
-    connected = client_connect_tls(client, config->server_host, config->server_port,
-                                   config->tls_cert, config->tls_key, config->tls_ca);
+    connected = client_connect_tls_ex(client, config->server_host, config->server_port,
+                                      config->tls_cert, config->tls_key, config->tls_ca,
+                                      &connect_opts);
   } else {
-    connected = client_connect(client, config->server_host, config->server_port);
+    connected = client_connect_ex(client, config->server_host, config->server_port,
+                                  &connect_opts);
   }
   if (!connected) {
     client_disconnect(client);

src/client/client_validation.c

@@ -34,6 +34,11 @@ bool validate_config(const Config* config) {
     log_message(LOG_LEVEL_ERROR, "--incremental is not supported with -s (chunk serialization)");
     return false;
   }
+  /* -4 and -6 are mutually exclusive: a socket address family cannot be both. */
+  if (config->ipv4 && config->ipv6) {
+    log_message(LOG_LEVEL_ERROR, "-4/--ipv4 and -6/--ipv6 are mutually exclusive");
+    return false;
+  }
   if (config->skip_compress_set && config->use_chunk_serialization) {
     log_message(LOG_LEVEL_ERROR,
                 "--skip-compress cannot be combined with -s (chunk serialization)");

src/client/usage.c

@@ -166,6 +166,11 @@ void print_usage(void) {
   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("  --address <ip>      Bind the outgoing client socket to this source address\n");
+  printf("  -4, --ipv4          Force IPv4 for destination resolution\n");
+  printf("  -6, --ipv6          Force IPv6 for destination resolution\n");
+  printf("  --sockopts=OPTS     Comma-separated OPT=VAL socket options applied before connect:\n");
+  printf("                      TCP_NODELAY, SO_KEEPALIVE, SO_RCVBUF, SO_SNDBUF, SO_REUSEADDR\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");