TT#14008 delay learning of endpoint address after re-invite

This fixes a race condition: Peer sends updated SDP with new address,
but an older RTP packet from the old address is received afterwards.
Thsi triggers learning of this old address is the "correct" endpoint.
Afterwards the peer stops sending RTP until a packet to the new endpoint
is received there, which never happens because the new endpoint has been
discarded in favour of the "learned" old one.

closes #817

Change-Id: I508f465a669f03e35ddcc6e770d5e7859e57569f
(cherry picked from commit 45bd10d323)

daemon/media_socket.c

@@ -4,6 +4,7 @@
 #include <glib.h>
 #include <errno.h>
 #include <netinet/in.h>
+#include <stdbool.h>
 #include "str.h"
 #include "ice.h"
 #include "socket.h"
@@ -1798,6 +1799,12 @@ static int media_packet_address_check(struct packet_handler_ctx *phc)
 		goto out;
 	}
 
+	/* wait at least 3 seconds after last signal before committing to a particular
+	 * endpoint address */
+	bool wait_time = false;
+	if (!phc->mp.call->last_signal || rtpe_now.tv_sec <= phc->mp.call->last_signal + 3)
+		wait_time = true;
+
 	const struct endpoint *use_endpoint_confirm = &phc->mp.fsin;
 
 	if (rtpe_config.endpoint_learning == EL_IMMEDIATE)
@@ -1836,9 +1843,7 @@ static int media_packet_address_check(struct packet_handler_ctx *phc)
 		}
 	}
 
-	/* wait at least 3 seconds after last signal before committing to a particular
-	 * endpoint address */
-	if (!phc->mp.call->last_signal || rtpe_now.tv_sec <= phc->mp.call->last_signal + 3)
+	if (wait_time)
 		goto update_peerinfo;
 
 confirm_now:
@@ -1851,11 +1856,18 @@ confirm_now:
 
 update_peerinfo:
 	mutex_lock(&phc->mp.stream->out_lock);
-	endpoint = phc->mp.stream->endpoint;
-	phc->mp.stream->endpoint = *use_endpoint_confirm;
-	if (memcmp(&endpoint, &phc->mp.stream->endpoint, sizeof(endpoint))) {
-		phc->unkernelize = 1;
-		phc->update = 1;
+	// if we're during the wait time, check the received address against the previously
+	// learned address. if they're the same, ignore this packet for learning purposes
+	if (!wait_time || !phc->mp.stream->learned_endpoint.address.family ||
+			memcmp(use_endpoint_confirm, &phc->mp.stream->learned_endpoint, sizeof(endpoint)))
+	{
+		endpoint = phc->mp.stream->endpoint;
+		phc->mp.stream->endpoint = *use_endpoint_confirm;
+		phc->mp.stream->learned_endpoint = *use_endpoint_confirm;
+		if (memcmp(&endpoint, &phc->mp.stream->endpoint, sizeof(endpoint))) {
+			phc->unkernelize = 1;
+			phc->update = 1;
+		}
 	}
 update_addr:
 	mutex_unlock(&phc->mp.stream->out_lock);

include/call.h

@@ -277,6 +277,7 @@ struct packet_stream {
 	struct endpoint		detected_endpoints[4];	/* LOCK: out_lock */
 	struct timeval		ep_detect_signal; /* LOCK: out_lock */
 	struct endpoint		advertised_endpoint; /* RO */
+	struct endpoint		learned_endpoint; /* LOCK: out_lock */
 	struct crypto_context	crypto;		/* OUT direction, LOCK: out_lock */
 	struct ssrc_ctx		*ssrc_in,	/* LOCK: in_lock */ // XXX eliminate these
 				*ssrc_out;	/* LOCK: out_lock */