stun.c: Fix ast_stun_request() erratic timeout.

If ast_stun_request() receives packets other than a STUN response then we
could conceivably never exit if we continue to receive packets with less
than three seconds between them.

* Fix poll timeout to keep track of the time when we sent the STUN
request.  We will now send a STUN request every three seconds regardless
of how many other packets we receive while waiting for a response until we
have completed three STUN request transmission cycles.

Change-Id: Ib606cb08585e06eb50877f67b8d3bd385a85c266

main/stun.c

@@ -411,6 +411,7 @@ int ast_stun_request(int s, struct sockaddr_in *dst,
 		/* send request, possibly wait for reply */
 		struct sockaddr_in src;
 		socklen_t srclen;
+		struct timeval start;
 
 		/* Send STUN message. */
 		res = stun_send(s, dst, req);
@@ -424,12 +425,20 @@ int ast_stun_request(int s, struct sockaddr_in *dst,
 			break;
 		}
 
+		start = ast_tvnow();
 try_again:
 		/* Wait for response. */
 		{
 			struct pollfd pfds = { .fd = s, .events = POLLIN };
+			int ms;
 
-			res = ast_poll(&pfds, 1, 3000);
+			ms = ast_remaining_ms(start, 3000);
+			if (ms <= 0) {
+				/* No response, timeout */
+				res = 1;
+				continue;
+			}
+			res = ast_poll(&pfds, 1, ms);
 			if (res < 0) {
 				/* Error */
 				continue;