conncheck: add a check to move into the ready state after a pair failed

This patch tries to move the component state from connected to ready in
places where a pair may fail. Consequently, the final check done after
the expiration of the idle timeout can be removed, assuming that
transitions are done as soon as they occur.

The only place where such a situation has been observed in a real world
stress test is a 401 unauthorized stun error received in
priv_map_reply_to_conn_check_request(), when the conncheck contains a
local and a remote candidate, both of type host, with an identical IP
address and port number (two boxes with a private network using the same
subnet). In such a case, a stun request to the remote candidate will
reach the local candidate instead, and will logically fail.

agent/conncheck.c

@@ -71,6 +71,8 @@ static size_t priv_create_username (NiceAgent *agent, NiceStream *stream,
     uint8_t *dest, guint dest_len, gboolean inbound);
 static size_t priv_get_password (NiceAgent *agent, NiceStream *stream,
     NiceCandidate *remote, uint8_t **password);
+static void candidate_check_pair_fail (NiceStream *stream,
+    NiceAgent *agent, CandidateCheckPair *p);
 static void candidate_check_pair_free (NiceAgent *agent,
     CandidateCheckPair *pair);
 static CandidateCheckPair *priv_conn_check_add_for_candidate_pair_matched (
@@ -390,7 +392,17 @@ priv_conn_check_initiate (NiceAgent *agent, CandidateCheckPair *pair)
 {
   SET_PAIR_STATE (agent, pair, NICE_CHECK_IN_PROGRESS);
   if (conn_check_send (agent, pair)) {
-    SET_PAIR_STATE (agent, pair, NICE_CHECK_FAILED);
+    NiceStream *stream;
+    NiceComponent *component;
+
+    if (!agent_find_component (agent, pair->stream_id, pair->component_id,
+        &stream, &component)) {
+      nice_debug ("Could not find stream or component in conn_check_initiate");
+      SET_PAIR_STATE (agent, pair, NICE_CHECK_FAILED);
+      return FALSE;
+    }
+    candidate_check_pair_fail (stream, agent, pair);
+    conn_check_update_check_list_state_for_ready (agent, stream, component);
     return FALSE;
   }
   return TRUE;
@@ -1176,7 +1188,7 @@ static gboolean priv_conn_check_tick_agent_locked (NiceAgent *agent,
 {
   gboolean keep_timer_going = FALSE;
   gboolean stun_sent = FALSE;
-  GSList *i, *j;
+  GSList *i;
 
   /* step: process triggered checks
    * these steps are ordered by priority, since a single stun request
@@ -1237,10 +1249,6 @@ static gboolean priv_conn_check_tick_agent_locked (NiceAgent *agent,
     for (i = agent->streams; i; i = i->next) {
       NiceStream *stream = i->data;
       priv_update_check_list_failed_components (agent, stream);
-      for (j = stream->components; j; j = j->next) {
-        NiceComponent *component = j->data;
-        conn_check_update_check_list_state_for_ready (agent, stream, component);
-      }
     }
 
     nice_debug ("Agent %p : %s: stopping conncheck timer", agent, G_STRFUNC);
@@ -3578,6 +3586,8 @@ static gboolean priv_map_reply_to_conn_check_request (NiceAgent *agent, NiceStre
 		tmpbuf, nice_address_get_port (&p->remote->addr),
 		tmpbuf2, nice_address_get_port (from));
 	  }
+          conn_check_update_check_list_state_for_ready (agent,
+              stream, component);
 	  return TRUE;
 	}
 
@@ -3587,6 +3597,8 @@ static gboolean priv_map_reply_to_conn_check_request (NiceAgent *agent, NiceStre
             nice_debug ("Agent %p : pair %p FAILED "
                 "(got a matching pair without a known remote candidate).", agent, p);
           }
+          conn_check_update_check_list_state_for_ready (agent,
+              stream, component);
           return TRUE;
         }
 
@@ -3728,6 +3740,7 @@ static gboolean priv_map_reply_to_conn_check_request (NiceAgent *agent, NiceStre
       } else {
 	/* case: STUN error, the check STUN context was freed */
 	candidate_check_pair_fail (stream, agent, p);
+        conn_check_update_check_list_state_for_ready (agent, stream, component);
       }
       return TRUE;
     }
@@ -4856,6 +4869,7 @@ conn_check_prune_socket (NiceAgent *agent, NiceStream *stream, NiceComponent *co
     NiceSocket *sock)
 {
   GSList *l;
+  gboolean pair_failed = FALSE;
 
   if (component->selected_pair.local &&
       component->selected_pair.local->sockptr == sock &&
@@ -4879,8 +4893,15 @@ conn_check_prune_socket (NiceAgent *agent, NiceStream *stream, NiceComponent *co
       candidate_check_pair_fail (stream, agent, p);
       candidate_check_pair_free (agent, p);
       stream->conncheck_list = g_slist_delete_link (stream->conncheck_list, l);
+      pair_failed = TRUE;
     }
 
     l = next;
   }
+
+  /* outside of the previous loop, because it may
+   * remove pairs from the conncheck list
+   */
+  if (pair_failed)
+    conn_check_update_check_list_state_for_ready (agent, stream, component);
 }