From 6d9e032232b872d2386451b129e271260b179883 Mon Sep 17 00:00:00 2001
From: Jakub Adam <jakub.adam@ktknet.cz>
Date: Tue, 12 Aug 2014 10:10:04 +0200
Subject: [PATCH] media: align TCP RTP+RTCP candidate pairs

Lync uses a single TCP connection for both RTP and RTCP, and also
expects the components within each candidate pair we offer to have
the same priority, IP, port, etc.

However, libnice initially creates distinct TCP candidate pairs and
it's only later, when a candidate pair is established, that connection
can be switched to mux (single-TCP-channel) mode (see e13d3ea2).

Consequently, because libnice gives us distinct pairs, the application
itself is responsible for offering our candidates in a format Lync
expects, and thus presenting TCP-pairs as duplicats which differ only
in component type (RTP or RTCP).
---
 src/purple/purple-media.c | 52 +++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 46 insertions(+), 6 deletions(-)

diff --git a/src/purple/purple-media.c b/src/purple/purple-media.c
index 8fc71e8e..50a6299c 100644
--- a/src/purple/purple-media.c
+++ b/src/purple/purple-media.c
@@ -586,22 +586,60 @@ sipe_backend_stream_initialized(struct sipe_backend_media *media,
 	return FALSE;
 }
 
+static GList *
+duplicate_tcp_candidates(GList *candidates)
+{
+	GList *i;
+	GList *result = NULL;
+
+	for (i = candidates; i; i = i->next) {
+		PurpleMediaCandidate *candidate = i->data;
+		PurpleMediaNetworkProtocol protocol =
+				purple_media_candidate_get_protocol(candidate);
+		guint component_id =
+				purple_media_candidate_get_component_id(candidate);
+
+		if (protocol != PURPLE_MEDIA_NETWORK_PROTOCOL_UDP) {
+			PurpleMediaCandidate *c2;
+
+			if (component_id != PURPLE_MEDIA_COMPONENT_RTP) {
+				/* Ignore TCP candidates for other than
+				 * the first component. */
+				g_object_unref(candidate);
+				continue;
+			}
+
+			c2 = purple_media_candidate_copy(candidate);
+			g_object_set(c2,
+				     "component-id", PURPLE_MEDIA_COMPONENT_RTCP,
+				     NULL);
+			result = g_list_append(result, c2);
+		}
+
+		result = g_list_append(result, candidate);
+	}
+
+	g_list_free(candidates);
+
+	return result;
+}
+
 GList *
 sipe_backend_media_get_active_local_candidates(struct sipe_backend_media *media,
 					       struct sipe_backend_stream *stream)
 {
-	return purple_media_get_active_local_candidates(media->m,
-							stream->sessionid,
-							stream->participant);
+	GList *candidates = purple_media_get_active_local_candidates(
+			media->m, stream->sessionid, stream->participant);
+	return duplicate_tcp_candidates(candidates);
 }
 
 GList *
 sipe_backend_media_get_active_remote_candidates(struct sipe_backend_media *media,
 						struct sipe_backend_stream *stream)
 {
-	return purple_media_get_active_remote_candidates(media->m,
-							 stream->sessionid,
-							 stream->participant);
+	GList *candidates = purple_media_get_active_remote_candidates(
+			media->m, stream->sessionid, stream->participant);
+	return duplicate_tcp_candidates(candidates);
 }
 
 const gchar *
@@ -896,6 +934,8 @@ sipe_backend_get_local_candidates(struct sipe_backend_media *media,
 	GList *candidates = purple_media_get_local_candidates(media->m,
 							      stream->sessionid,
 							      stream->participant);
+	candidates = duplicate_tcp_candidates(candidates);
+
 	/*
 	 * Sometimes purple will not return complete list of candidates, even
 	 * after "candidates-prepared" signal is emitted. This is a feature of
-- 
2.11.4.GIT