Proper inheriting of branch attributes during DNS-based failover.

When creating a fake request based on an existing UAC entity, use the DST_URI and PATH_VEC specific to that UAC entity and not the per-message values.
This will correctly preserve the DST_URI and PATH_VEC during a DNS based failover, where the new branch must be a perfect copy of the original failed branch.

(cherry picked from commit 09473b3)

modules/tm/async.c

@@ -93,9 +93,12 @@ int t_resume_async(int fd, void *param)
 		abort();
 	}
 
-	/* prepare for resume route */
+	/* prepare for resume route, by filling in a phony UAC structure to
+	 * trigger the inheritance of the branch specific values */
 	uac.br_flags = getb0flags( t->uas.request ) ;
 	uac.uri = *GET_RURI( t->uas.request );
+	uac.duri = t->uas.request->dst_uri;
+	uac.path_vec = t->uas.request->path_vec;
 	if (!fake_req( &faked_req /* the fake msg to be built*/,
 		t->uas.request, /* the template msg saved in transaction */
 		&t->uas, /*the UAS side of the transaction*/

modules/tm/t_msgbuilder.h

@@ -227,23 +227,21 @@ static inline int fake_req(struct sip_msg *faked_req, struct sip_msg *shm_msg,
 	if (inherit_br_data) {
 		/* duplicate the dst_uri and path_vec into private mem
 		 * so that they can be visible and changed at script level */
-		if (shm_msg->dst_uri.s) {
-			faked_req->dst_uri.s = pkg_malloc(shm_msg->dst_uri.len);
+		if (uac->duri.s) {
+			faked_req->dst_uri.s = pkg_malloc(uac->duri.len);
 			if (!faked_req->dst_uri.s) {
 				LM_ERR("out of pkg mem\n");
 				goto out;
 			}
-			memcpy(faked_req->dst_uri.s, shm_msg->dst_uri.s,
-				shm_msg->dst_uri.len);
+			memcpy(faked_req->dst_uri.s, uac->duri.s, uac->duri.len);
 		}
-		if (shm_msg->path_vec.s) {
-			faked_req->path_vec.s = pkg_malloc(shm_msg->path_vec.len);
+		if (uac->path_vec.s) {
+			faked_req->path_vec.s = pkg_malloc(uac->path_vec.len);
 			if (!faked_req->path_vec.s) {
 				LM_ERR("out of pkg mem\n");
 				goto out2;
 			}
-			memcpy(faked_req->path_vec.s, shm_msg->path_vec.s,
-				shm_msg->path_vec.len);
+			memcpy(faked_req->path_vec.s, uac->path_vec.s, uac->path_vec.len);
 		}
 		/* Q value was already copied as part of the sip_msg struct */
 	} else {