Correct interface binding

Signed-off-by: Thomas De Backer <mosterdt@debacker.me>

src/net.c

@@ -640,7 +640,8 @@ static int net__bind_interface(struct mosquitto__listener *listener, struct addr
 		}
 	}
 	freeifaddrs(ifaddr);
-	log__printf(NULL, MOSQ_LOG_ERR, "Error: Interface %s not found.", listener->bind_interface);
+	log__printf(NULL, MOSQ_LOG_WARNING, "Warning: Interface %s does not support %s.",
+	            listener->bind_interface, rp->ai_addr->sa_family == AF_INET ? "ipv4" : "ipv6");
 	return MOSQ_ERR_NOT_FOUND;
 }
 #endif
@@ -654,6 +655,9 @@ static int net__socket_listen_tcp(struct mosquitto__listener *listener)
 	char service[10];
 	int rc;
 	int ss_opt = 1;
+#ifndef WIN32
+	bool interface_bound = false;
+#endif
 
 	if(!listener) return MOSQ_ERR_INVAL;
 
@@ -718,12 +722,14 @@ static int net__socket_listen_tcp(struct mosquitto__listener *listener)
 
 #ifndef WIN32
 		if(listener->bind_interface){
+			/* It might be possible that an interface does not support all relevant sa_families.
+			 * We should successfully find at least one. */
 			if(net__bind_interface(listener, rp)){
 				COMPAT_CLOSE(sock);
-				freeaddrinfo(ainfo);
-				mosquitto__free(listener->socks);
-				return 1;
+				listener->sock_count--;
+				continue;
 			}
+			interface_bound = true;
 		}
 #endif
 
@@ -745,6 +751,13 @@ static int net__socket_listen_tcp(struct mosquitto__listener *listener)
 	}
 	freeaddrinfo(ainfo);
 
+#ifndef WIN32
+	if(listener->bind_interface && !interface_bound){
+		mosquitto__free(listener->socks);
+		return 1;
+	}
+#endif
+
 	return 0;
 }