conncheck: avoid transport association mismatch

In some rare cases, the same address and port number may match two
remotes candidates, a tcp and an udp one, and lead to buggy pair
construction with incompatible transport. This supplementary check
prevents this problem. The matching test is not aimed to be exhaustive
but just a way to discard obviously broken associations, and fallback to
accept everything else (because socket type has a great diversity, with
socket types based on other sockets types).

It should fix #81, where such bogus transport association has been
reported (tcp-pass:udp).

1 files changed, 35 insertions, 2 deletions

diff --git a/agent/conncheck.c b/agent/conncheck.c
index e139ead..a979f3f 100644
--- a/agent/conncheck.c
+++ b/agent/conncheck.c
@@ -1855,6 +1855,35 @@ gint conn_check_compare (const CandidateCheckPair *a, const CandidateCheckPair *
   return 0;
 }
 
+static gboolean
+priv_match_remote_candidate_transport_and_socket_type (NiceAgent *agent,
+    NiceCandidate *candidate, NiceSocket *socket)
+{
+  gboolean ret = TRUE;
+  g_assert (socket);
+  g_assert (candidate);
+
+  /* Detect some obvious incompatibilites.
+   *
+   * In rare situations, tcp and udp candidate may have the same
+   * couple (address, port), they must be identified by their
+   * matching transport.
+   */
+  if (socket->type == NICE_SOCKET_TYPE_UDP_BSD &&
+      candidate->transport == NICE_CANDIDATE_TRANSPORT_TCP_ACTIVE)
+    ret = FALSE;
+  if (socket->type == NICE_SOCKET_TYPE_TCP_BSD &&
+      candidate->transport == NICE_CANDIDATE_TRANSPORT_UDP)
+    ret = FALSE;
+
+  nice_debug_verbose ("Agent %p : socket/candidate compat: %s and %s: %s",
+      agent, priv_socket_type_to_string (socket->type),
+      priv_candidate_transport_to_string (candidate->transport),
+      ret ? "yes" : "no");
+
+  return ret;
+}
+
 void
 conn_check_remote_candidates_set(NiceAgent *agent, NiceStream *stream,
     NiceComponent *component)
@@ -1883,7 +1912,9 @@ conn_check_remote_candidates_set(NiceAgent *agent, NiceStream *stream,
       NiceCandidate *rcand = l->data;
       NiceCandidate *lcand = NULL;
 
-      if (nice_address_equal (&rcand->addr, &icheck->from)) {
+      if (nice_address_equal (&rcand->addr, &icheck->from) &&
+          priv_match_remote_candidate_transport_and_socket_type
+            (agent, rcand, icheck->local_socket)) {
         for (m = component->local_candidates; m; m = m->next) {
           NiceCandidate *cand = m->data;
           NiceAddress *addr;
@@ -4461,7 +4492,9 @@ gboolean conn_check_handle_inbound_stun (NiceAgent *agent, NiceStream *stream,
 
   for (i = component->remote_candidates; i; i = i->next) {
     NiceCandidate *cand = i->data;
-    if (nice_address_equal (from, &cand->addr)) {
+    if (nice_address_equal (from, &cand->addr) &&
+        priv_match_remote_candidate_transport_and_socket_type
+          (agent, cand, nicesock)) {
       remote_candidate = cand;
       break;
     }