Allow binding a listener to a specific network interface

Signed-off-by: Steven Lawrance <[email protected]>

man/mosquitto.conf.5.xml

@@ -803,6 +803,16 @@
  <para>Not reloaded on reload signal.</para>
  </listitem>
  </varlistentry>
+ <varlistentry>
+ <term><option>bind_interface</option> <replaceable>device</replaceable></term>
+ <listitem>
+ <para>Listen for incoming network connections only on
+ the specified interface. This is similar to the
+ preceding option but useful when an interface has
+ multiple addresses or the address may change.</para>
+ <para>Not reloaded on reload signal.</para>
+ </listitem>
+ </varlistentry>
  <varlistentry>
  <term><option>http_dir</option> <replaceable>directory</replaceable></term>
  <listitem>

mosquitto.conf

@@ -207,6 +207,11 @@
 # Port to use for the default listener.
 #port 1883
 
+# Bind the listener to a specific interface. This is similar to
+# bind_address above but useful when an interface has multiple
+# addresses or the address may change. Only available on Linux.
+#bind_interface eth0
+
 # The maximum number of client connections to allow. This is 
 # a per listener setting.
 # Default is -1, which means unlimited connections.

src/conf.c

@@ -291,6 +291,7 @@ void config__cleanup(struct mosquitto__config *config)
  if(config->listeners){
  for(i=0; i<config->listener_count; i++){
  mosquitto__free(config->listeners[i].host);
+ mosquitto__free(config->listeners[i].bind_interface);
  mosquitto__free(config->listeners[i].mount_point);
  mosquitto__free(config->listeners[i].socks);
  mosquitto__free(config->listeners[i].security_options.auto_id_prefix);
@@ -915,6 +916,14 @@ int config__read_file_core(struct mosquitto__config *config, bool reload, struct
  if(conf__attempt_resolve(config->default_listener.host, "bind_address", MOSQ_LOG_ERR, "Error")){
  return MOSQ_ERR_INVAL;
  }
+ }else if(!strcmp(token, "bind_interface")){
+#ifdef SO_BINDTODEVICE
+ if(reload) continue; // Listeners not valid for reloading.
+ if(conf__parse_string(&token, "bind_interface", &cur_listener->bind_interface, saveptr)) return MOSQ_ERR_INVAL;
+#else
+ log__printf(NULL, MOSQ_LOG_ERR, "Error: bind_interface specified but socket option not available.");
+ return MOSQ_ERR_INVAL;
+#endif
  }else if(!strcmp(token, "bridge_attempt_unsubscribe")){
 #ifdef WITH_BRIDGE
  if(reload) continue; // FIXME

src/mosquitto_broker_internal.h

@@ -212,6 +212,7 @@ struct mosquitto__listener {
  int fd;
  uint16_t port;
  char *host;
+ char *bind_interface;
  int max_connections;
  char *mount_point;
  mosq_sock_t *socks;

src/net.c

@@ -22,6 +22,7 @@ and the Eclipse Distribution License is available at
 #include <arpa/inet.h>
 #include <sys/socket.h>
 #include <netinet/tcp.h>
+#include <net/if.h>
 #else
 #include <winsock2.h>
 #include <ws2tcpip.h>
@@ -395,6 +396,9 @@ int net__socket_listen(struct mosquitto__listener *listener)
  X509_LOOKUP *lookup;
  ENGINE *engine = NULL;
 #endif
+#ifdef SO_BINDTODEVICE
+ struct ifreq ifr;
+#endif
 
  if(!listener) return MOSQ_ERR_INVAL;
 
@@ -446,6 +450,20 @@ int net__socket_listen(struct mosquitto__listener *listener)
  return 1;
  }
 
+#ifdef SO_BINDTODEVICE
+ if(listener->bind_interface){
+ memset(&ifr, 0, sizeof(ifr));
+ strncpy(ifr.ifr_name, listener->bind_interface, sizeof(ifr.ifr_name)-1);
+ ifr.ifr_name[sizeof(ifr.ifr_name)-1] = '\0';
+ log__printf(NULL, MOSQ_LOG_INFO, "Binding listener to interface \"%s\".", ifr.ifr_name);
+ if(setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, (void *)&ifr, sizeof(ifr)) < 0) {
+ net__print_error(MOSQ_LOG_ERR, "Error: %s");
+ COMPAT_CLOSE(sock);
+ return 1;
+ }
+ }
+#endif
+
  if(bind(sock, rp->ai_addr, rp->ai_addrlen) == -1){
  net__print_error(MOSQ_LOG_ERR, "Error: %s");
  COMPAT_CLOSE(sock);