channels/chan_sip.c: use binding IP address for outgoing TCP SIP connections

For outgoing TCP connections, Asterisk uses the first IP address of the
interface instead of the IP address we asked him to bind to.

ASTERISK-26922 #close
Reported-by: Ksenia

Change-Id: I43c71ca89211dbf1838e5bcdb9be8d06d98e54eb

channels/chan_sip.c

@@ -29275,6 +29275,17 @@ static int sip_prepare_socket(struct sip_pvt *p)
 		}
 	}
 
+	/* If a bind address has been specified, use it */
+	if ((s->type == AST_TRANSPORT_TLS) && !ast_sockaddr_isnull(&sip_tls_desc.local_address)) {
+		ca->local_address = sip_tls_desc.local_address;
+	}
+	else if ((s->type == AST_TRANSPORT_TCP) && !ast_sockaddr_isnull(&sip_tcp_desc.local_address)) {
+		ca->local_address = sip_tcp_desc.local_address;
+	}
+	/* Reset tcp source port to zero to let system pick a random one */
+	if (!ast_sockaddr_isnull(&ca->local_address)) {
+		ast_sockaddr_set_port(&ca->local_address, 0);
+	}
 	/* Create a client connection for address, this does not start the connection, just sets it up. */
 	if (!(s->tcptls_session = ast_tcptls_client_create(ca))) {
 		goto create_tcptls_session_fail;