conncheck: dont cancel a pair for triggered check

This patch adds another supplementary "corner" case, not covered by the
ICE spec, sect 8.1.2, "Updating States". A pair in waiting state and in
the triggered check list should be considered like an in-progress pair,
and cancelled only if its priority is lower than the priority of the
nominated pair. This is required in some aggressive nomination
situations for both peers to select the same pair, having the highest
priority.

Differential Revision: https://phabricator.freedesktop.org/D933

agent/conncheck.c

@@ -64,7 +64,7 @@
 
 static void priv_update_check_list_failed_components (NiceAgent *agent, NiceStream *stream);
 static void priv_update_check_list_state_for_ready (NiceAgent *agent, NiceStream *stream, NiceComponent *component);
-static guint priv_prune_pending_checks (NiceStream *stream, guint component_id);
+static guint priv_prune_pending_checks (NiceAgent *agent, NiceStream *stream, guint component_id);
 static gboolean priv_schedule_triggered_check (NiceAgent *agent, NiceStream *stream, NiceComponent *component, NiceSocket *local_socket, NiceCandidate *remote_cand);
 static void priv_mark_pair_nominated (NiceAgent *agent, NiceStream *stream, NiceComponent *component, NiceCandidate *localcand, NiceCandidate *remotecand);
 static size_t priv_create_username (NiceAgent *agent, NiceStream *stream,
@@ -176,6 +176,16 @@ priv_print_conn_check_lists (NiceAgent *agent, const gchar *where, const gchar *
   }
 }
 
+/* Verify if the pair is in the triggered checks list
+ */
+
+static gboolean
+priv_is_pair_in_triggered_check_queue (NiceAgent *agent, CandidateCheckPair *pair)
+{
+  g_assert (pair);
+  return (g_slist_find (agent->triggered_check_queue, pair) != NULL);
+}
+
 /* Add the pair to the triggered checks list, if not already present
  */
 static void
@@ -1897,7 +1907,7 @@ static void priv_update_check_list_state_for_ready (NiceAgent *agent, NiceStream
     /* Only go to READY if no checks are left in progress. If there are
      * any that are kept, then this function will be called again when the
      * conncheck tick timer finishes them all */
-    if (priv_prune_pending_checks (stream, component->id) == 0) {
+    if (priv_prune_pending_checks (agent, stream, component->id) == 0) {
       /* Continue through the states to give client code a nice
        * logical progression. See http://phabricator.freedesktop.org/D218 for
        * discussion. */
@@ -2693,14 +2703,14 @@ int conn_check_send (NiceAgent *agent, CandidateCheckPair *pair)
  *
  * @see priv_update_check_list_state_failed_components()
  */
-static guint priv_prune_pending_checks (NiceStream *stream, guint component_id)
+static guint priv_prune_pending_checks (NiceAgent *agent, NiceStream *stream, guint component_id)
 {
   GSList *i;
   guint64 highest_nominated_priority = 0;
   guint in_progress = 0;
 
-  nice_debug ("Agent XXX: Finding highest priority for component %d",
-      component_id);
+  nice_debug ("Agent %p: Finding highest priority for component %d",
+      agent, component_id);
 
   for (i = stream->conncheck_list; i; i = i->next) {
     CandidateCheckPair *p = i->data;
@@ -2712,41 +2722,47 @@ static guint priv_prune_pending_checks (NiceStream *stream, guint component_id)
     }
   }
 
-  nice_debug ("Agent XXX: Pruning pending checks. Highest nominated priority "
-      "is %" G_GUINT64_FORMAT, highest_nominated_priority);
+  nice_debug ("Agent %p: Pruning pending checks. Highest nominated priority "
+      "is %" G_GUINT64_FORMAT, agent, highest_nominated_priority);
 
   /* step: cancel all FROZEN and WAITING pairs for the component */
   /* note: this case is not covered by the ICE spec, 8.1.2
    * "Updating States", but a pair in waiting state which will be
    * nominated on response receipt should be treated the same way
-   * that an in-progress pair.
+   * that an in-progress pair. A pair in waiting state and in
+   * the triggered check list should also be treated like an in-progress
+   * pair.
    */
   for (i = stream->conncheck_list; i; i = i->next) {
     CandidateCheckPair *p = i->data;
+
     if (p->component_id == component_id) {
+      gboolean like_in_progress =
+          p->mark_nominated_on_response_arrival ||
+          priv_is_pair_in_triggered_check_queue (agent, p);
+
       if (p->state == NICE_CHECK_FROZEN ||
-          (p->state == NICE_CHECK_WAITING &&
-          !p->mark_nominated_on_response_arrival)) {
+          (p->state == NICE_CHECK_WAITING && !like_in_progress)) {
 	p->state = NICE_CHECK_CANCELLED;
-        nice_debug ("Agent XXX : pair %p state CANCELED", p);
+        nice_debug ("Agent %p : pair %p state CANCELED", agent, p);
       }
 
       /* note: a SHOULD level req. in ICE 8.1.2. "Updating States" (ID-19) */
       if (p->state == NICE_CHECK_IN_PROGRESS ||
-          (p->state == NICE_CHECK_WAITING &&
-          p->mark_nominated_on_response_arrival)) {
+          (p->state == NICE_CHECK_WAITING && like_in_progress)) {
         if (highest_nominated_priority != 0 &&
             p->priority < highest_nominated_priority) {
           p->stun_message.buffer = NULL;
           p->stun_message.buffer_len = 0;
           p->state = NICE_CHECK_CANCELLED;
-          nice_debug ("Agent XXX : pair %p state CANCELED", p);
+          nice_debug ("Agent %p : pair %p state CANCELED", agent, p);
         } else {
           /* We must keep the higher priority pairs running because if a udp
            * packet was lost, we might end up using a bad candidate */
-          nice_debug ("Agent XXX : pair %p kept IN_PROGRESS because priority %"
+          nice_debug ("Agent %p : pair %p kept IN_PROGRESS because priority %"
               G_GUINT64_FORMAT " is higher than currently nominated pair %"
-              G_GUINT64_FORMAT, p, p->priority, highest_nominated_priority);
+              G_GUINT64_FORMAT, agent,
+              p, p->priority, highest_nominated_priority);
           in_progress++;
         }
       }