Ping the premier connection on each network with higher priority.

webrtc/p2p/base/p2ptransportchannel.h

 /*
  *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 238 matching lines @@
   bool CreateConnection(PortInterface* port,
                         const Candidate& remote_candidate,
                         PortInterface* origin_port);
   bool FindConnection(cricket::Connection* connection) const;
 
   uint32_t GetRemoteCandidateGeneration(const Candidate& candidate);
   bool IsDuplicateRemoteCandidate(const Candidate& candidate);
   void RememberRemoteCandidate(const Candidate& remote_candidate,
                                PortInterface* origin_port);
   bool IsPingable(const Connection* conn, int64_t now) const;
-  bool IsSelectedConnectionPingable(int64_t now);
+  bool IsPremierConnectionPingable(Connection* conn, int64_t now);

[Taylor Brandstetter, 2016/10/04 02:08:10]

Can you explain in a comment somewhere what's meant by "premier connection"?

[honghaiz3, 2016/10/20 23:47:58]

Done.

   int CalculateActiveWritablePingInterval(const Connection* conn,
                                           int64_t now) const;
   void PingConnection(Connection* conn);
   void AddAllocatorSession(std::unique_ptr<PortAllocatorSession> session);
   void AddConnection(Connection* connection);
 
   void OnPortReady(PortAllocatorSession *session, PortInterface* port);
   void OnPortsPruned(PortAllocatorSession* session,
                      const std::vector<PortInterface*>& ports);
   void OnCandidatesReady(PortAllocatorSession *session,
@@ skipping 35 matching lines @@
   // Returns true if we should switch to the new connection.
   // sets |missed_receiving_unchanged_threshold| to true if either
   // the selected connection or the new connection missed its
   // receiving-unchanged-threshold.
   bool ShouldSwitchSelectedConnection(
       Connection* new_connection,
       bool* missed_receiving_unchanged_threshold) const;
   // Returns true if the new_connection is selected for transmission.
   bool MaybeSwitchSelectedConnection(Connection* new_connection,
                                      const std::string& reason);
-
+  // Updates the premier connection for each network name. This method is
+  // called every time after connections are sorted.
+  void UpdatePremierConnections();
   void PruneConnections();
   bool IsBackupConnection(const Connection* conn) const;
 
   Connection* FindConnectionToPing(int64_t now);
   Connection* FindOldestConnectionNeedingTriggeredCheck(int64_t now);
+  // Finds the best premier connection for pinging.
+  Connection* FindBestPremierConnectionToPing(int64_t now);
   // Between |conn1| and |conn2|, this function returns the one which should
   // be pinged first.
   Connection* SelectMostPingableConnection(Connection* conn1,
                                            Connection* conn2);
   // Select the connection which is Relay/Relay. If both of them are,
   // UDP relay protocol takes precedence.
   Connection* MostLikelyToWork(Connection* conn1, Connection* conn2);
   // Compare the last_ping_sent time and return the one least recently pinged.
   Connection* LeastRecentlyPinged(Connection* conn1, Connection* conn2);
 
@@ skipping 32 matching lines @@
   // |connections_| is a sorted list with the first one always be the
   // |selected_connection_| when it's not nullptr. The combination of
   // |pinged_connections_| and |unpinged_connections_| has the same
   // connections as |connections_|. These 2 sets maintain whether a
   // connection should be pinged next or not.
   std::vector<Connection *> connections_;
   std::set<Connection*> pinged_connections_;
   std::set<Connection*> unpinged_connections_;
 
   Connection* selected_connection_ = nullptr;
+  // The top-ranked connection for each network interface, identified by the
+  // interface name.
+  std::map<std::string, Connection*> premier_connection_by_network_name_;

[Taylor Brandstetter, 2016/10/04 02:08:10]

Can't this be determined algorithmically from connections_? If so I'd prefer not
storing a separate map.

[honghaiz3, 2016/10/20 23:47:58]

Done.

 
   std::vector<RemoteCandidate> remote_candidates_;
   bool sort_dirty_;  // indicates whether another sort is needed right now
   bool had_connection_ = false;  // if connections_ has ever been nonempty
   typedef std::map<rtc::Socket::Option, int> OptionMap;
   OptionMap options_;
   IceParameters ice_parameters_;
   std::vector<IceParameters> remote_ice_parameters_;
   IceMode remote_ice_mode_;
   IceRole ice_role_;
@@ skipping 10 matching lines @@
   // The value put in the "nomination" attribute for the next nominated
   // connection. A zero-value indicates the connection will not be nominated.
   uint32_t nomination_ = 0;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(P2PTransportChannel);
 };
 
 }  // namespace cricket
 
 #endif  // WEBRTC_P2P_BASE_P2PTRANSPORTCHANNEL_H_