Add MOSQ_OPT_BIND_ADDRESS.

This allows setting of a bind address independently of the
`mosquitto_connect*()` call.

ChangeLog.txt

@@ -75,6 +75,8 @@ Client library:
 - Fix send quota being incorrecly reset on reconnect. Closes #1822.
 - Don't use logging until log mutex is initialised. Closes #1819.
 - Fix missing mach/mach_time.h header on OS X. Closes #1831.
+- Add MOSQ_OPT_BIND_ADDRESS to allow setting of a bind address independently
+  of the `mosquitto_connect*()` call.
 
 Clients:
 - Add timeout return code (27) for `mosquitto_sub -W <secs>` and

include/mosquitto.h

@@ -118,6 +118,7 @@ enum mosq_opt_t {
 	MOSQ_OPT_TLS_OCSP_REQUIRED = 9,
 	MOSQ_OPT_TLS_ALPN = 10,
 	MOSQ_OPT_TCP_NODELAY = 11,
+	MOSQ_OPT_BIND_ADDRESS = 12,
 };
 
 
@@ -1485,6 +1486,9 @@ libmosq_EXPORT int mosquitto_int_option(struct mosquitto *mosq, enum mosq_opt_t
  *	          services available on a single TLS port, such as both MQTT
  *	          and WebSockets, use this option to configure the ALPN
  *	          option for the connection.
+ *
+ *	MOSQ_OPT_BIND_ADDRESS - Set the hostname or ip address of the local network
+ *	          interface to bind to when connecting.
  */
 libmosq_EXPORT int mosquitto_string_option(struct mosquitto *mosq, enum mosq_opt_t option, const char *value);
 

lib/connect.c

@@ -33,10 +33,10 @@ Contributors:
 static char alphanum[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
 
 static int mosquitto__reconnect(struct mosquitto *mosq, bool blocking, const mosquitto_property *properties);
-static int mosquitto__connect_init(struct mosquitto *mosq, const char *host, int port, int keepalive, const char *bind_address);
+static int mosquitto__connect_init(struct mosquitto *mosq, const char *host, int port, int keepalive);
 
 
-static int mosquitto__connect_init(struct mosquitto *mosq, const char *host, int port, int keepalive, const char *bind_address)
+static int mosquitto__connect_init(struct mosquitto *mosq, const char *host, int port, int keepalive)
 {
 	int i;
 	int rc;
@@ -70,12 +70,6 @@ static int mosquitto__connect_init(struct mosquitto *mosq, const char *host, int
 	if(!mosq->host) return MOSQ_ERR_NOMEM;
 	mosq->port = port;
 
-	mosquitto__free(mosq->bind_address);
-	if(bind_address){
-		mosq->bind_address = mosquitto__strdup(bind_address);
-		if(!mosq->bind_address) return MOSQ_ERR_NOMEM;
-	}
-
 	mosq->keepalive = keepalive;
 	mosq->msgs_in.inflight_quota = mosq->msgs_in.inflight_maximum;
 	mosq->msgs_out.inflight_quota = mosq->msgs_out.inflight_maximum;
@@ -100,12 +94,15 @@ int mosquitto_connect_bind_v5(struct mosquitto *mosq, const char *host, int port
 {
 	int rc;
 
+	rc = mosquitto_string_option(mosq, MOSQ_OPT_BIND_ADDRESS, bind_address);
+	if(rc) return rc;
+
 	if(properties){
 		rc = mosquitto_property_check_all(CMD_CONNECT, properties);
 		if(rc) return rc;
 	}
 
-	rc = mosquitto__connect_init(mosq, host, port, keepalive, bind_address);
+	rc = mosquitto__connect_init(mosq, host, port, keepalive);
 	if(rc) return rc;
 
 	mosquitto__set_state(mosq, mosq_cs_new);
@@ -122,7 +119,12 @@ int mosquitto_connect_async(struct mosquitto *mosq, const char *host, int port,
 
 int mosquitto_connect_bind_async(struct mosquitto *mosq, const char *host, int port, int keepalive, const char *bind_address)
 {
-	int rc = mosquitto__connect_init(mosq, host, port, keepalive, bind_address);
+	int rc;
+
+	rc = mosquitto_string_option(mosq, MOSQ_OPT_BIND_ADDRESS, bind_address);
+	if(rc) return rc;
+
+	rc = mosquitto__connect_init(mosq, host, port, keepalive);
 	if(rc) return rc;
 
 	return mosquitto__reconnect(mosq, false, NULL);

lib/options.c

@@ -321,6 +321,20 @@ int mosquitto_string_option(struct mosquitto *mosq, enum mosq_opt_t option, cons
 #endif
 			break;
 
+		case MOSQ_OPT_BIND_ADDRESS:
+			mosquitto__free(mosq->bind_address);
+			if(value){
+				mosq->bind_address = mosquitto__strdup(value);
+				if(mosq->bind_address){
+					return MOSQ_ERR_SUCCESS;
+				}else{
+					return MOSQ_ERR_NOMEM;
+				}
+			}else{
+				return MOSQ_ERR_SUCCESS;
+			}
+
+
 		default:
 			return MOSQ_ERR_INVAL;
 	}