Add socket_domain option.

ChangeLog.txt

@@ -1,6 +1,12 @@
 1.5.5 - 201812xx
 ================
 
+Broker:
+- Add `socket_domain` option to allow listeners to disable IPv6 support.
+  This is required to work around a problem in libwebsockets that means
+  sockets only listen on IPv6 by default if IPv6 support is compiled in.
+  Closes #1004.
+
 Client:
 - Always print leading zeros in mosquitto_sub when output format is hex.
   Closes #1066.

man/mosquitto.conf.5.xml

@@ -813,6 +813,27 @@
 						<para>Not reloaded on reload signal.</para>
 					</listitem>
 				</varlistentry>
+				<varlistentry>
+					<term><option>socket_domain</option> [ ipv4 | ipv6 ]</term>
+					<listitem>
+						<para>By default, a listener will attempt to listen on
+							all supported IP protocol versions. If you do not
+							have an IPv4 or IPv6 interface you may wish to
+							disable support for either of those protocol
+							versions. In particular, note that due to the
+							limitations of the websockets library, it will only
+							ever attempt to open IPv6 sockets if IPv6 support
+							is compiled in, and so will fail if IPv6 is not
+							available.</para>
+						<para>Set to <option>ipv4</option> to force the
+							listener to only use IPv4, or set to
+							<option>ipv6</option> to force the listener to only
+							use IPv6. If you want support for both IPv4 and
+							IPv6, then do not use the
+							<option>socket_domain</option> option.</para>
+						<para>Not reloaded on reload signal.</para>
+					</listitem>
+				</varlistentry>
 				<varlistentry>
 					<term><option>use_username_as_clientid</option> [ true | false ]</term>
 					<listitem>

src/conf.c

@@ -446,6 +446,7 @@ int config__parse_args(struct mosquitto_db *db, struct mosquitto__config *config
 			|| config->default_listener.max_connections != -1
 			|| config->default_listener.mount_point
 			|| config->default_listener.protocol != mp_mqtt
+			|| config->default_listener.socket_domain
 			|| config->default_listener.security_options.password_file
 			|| config->default_listener.security_options.psk_file
 			|| config->default_listener.security_options.auth_plugin_config_count
@@ -476,6 +477,7 @@ int config__parse_args(struct mosquitto_db *db, struct mosquitto__config *config
 		}
 		config->listeners[config->listener_count-1].max_connections = config->default_listener.max_connections;
 		config->listeners[config->listener_count-1].protocol = config->default_listener.protocol;
+		config->listeners[config->listener_count-1].socket_domain = config->default_listener.socket_domain;
 		config->listeners[config->listener_count-1].client_count = 0;
 		config->listeners[config->listener_count-1].socks = NULL;
 		config->listeners[config->listener_count-1].sock_count = 0;
@@ -1773,6 +1775,22 @@ int config__read_file_core(struct mosquitto__config *config, bool reload, struct
 #else
 					log__printf(NULL, MOSQ_LOG_WARNING, "Warning: Bridge support not available.");
 #endif
+				}else if(!strcmp(token, "socket_domain")){
+					if(reload) continue; // Listeners not valid for reloading.
+					token = strtok_r(NULL, " ", &saveptr);
+					if(token){
+						if(!strcmp(token, "ipv4")){
+							cur_listener->socket_domain = AF_INET;
+						}else if(!strcmp(token, "ipv6")){
+							cur_listener->socket_domain = AF_INET6;
+						}else{
+							log__printf(NULL, MOSQ_LOG_ERR, "Error: Invalid socket_domain value \"%s\" in configuration.", token);
+							return MOSQ_ERR_INVAL;
+						}
+					}else{
+						log__printf(NULL, MOSQ_LOG_ERR, "Error: Empty socket_domain value in configuration.");
+						return MOSQ_ERR_INVAL;
+					}
 				}else if(!strcmp(token, "store_clean_interval")){
 					log__printf(NULL, MOSQ_LOG_WARNING, "Warning: store_clean_interval is no longer needed.");
 				}else if(!strcmp(token, "sys_interval")){

src/mosquitto_broker_internal.h

@@ -218,6 +218,7 @@ struct mosquitto__listener {
 	int sock_count;
 	int client_count;
 	enum mosquitto_protocol protocol;
+	int socket_domain;
 	bool use_username_as_clientid;
 #ifdef WITH_TLS
 	char *cafile;

src/net.c

@@ -391,7 +391,11 @@ int net__socket_listen(struct mosquitto__listener *listener)
 
 	snprintf(service, 10, "%d", listener->port);
 	memset(&hints, 0, sizeof(struct addrinfo));
+	if(listener->socket_domain){
+		hints.ai_family = listener->socket_domain;
+	}else{
 		hints.ai_family = AF_UNSPEC;
+	}
 	hints.ai_flags = AI_PASSIVE;
 	hints.ai_socktype = SOCK_STREAM;
 

src/websockets.c

@@ -729,6 +729,9 @@ struct libwebsocket_context *mosq_websockets_init(struct mosquitto__listener *li
 #if LWS_LIBRARY_VERSION_MAJOR>1
 	info.options |= LWS_SERVER_OPTION_DO_SSL_GLOBAL_INIT;
 #endif
+	if(listener->socket_domain == AF_INET){
+		info.options |= LWS_SERVER_OPTION_DISABLE_IPV6;
+	}
 
 	user = mosquitto__calloc(1, sizeof(struct libws_mqtt_hack));
 	if(!user){