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 25 matching lines @@
 #include "webrtc/base/asyncpacketsocket.h"
 #include "webrtc/base/sigslot.h"
 
 namespace cricket {
 
 // Enum for UMA metrics, used to record whether the channel is
 // connected/connecting/disconnected when ICE restart happens.
 enum class IceRestartState { CONNECTING, CONNECTED, DISCONNECTED, MAX_VALUE };
 
 extern const int WEAK_PING_INTERVAL;
-extern const int STABILIZING_WRITABLE_CONNECTION_PING_INTERVAL;
-extern const int STABLE_WRITABLE_CONNECTION_PING_INTERVAL;
+extern const int WEAK_OR_STABILIZING_WRITABLE_CONNECTION_PING_INTERVAL;
+extern const int STRONG_AND_STABLE_WRITABLE_CONNECTION_PING_INTERVAL;
 static const int MIN_PINGS_AT_WEAK_PING_INTERVAL = 3;
 
 // Adds the port on which the candidate originated.
 class RemoteCandidate : public Candidate {
  public:
   RemoteCandidate(const Candidate& c, PortInterface* origin_port)
       : Candidate(c), origin_port_(origin_port) {}
 
   PortInterface* origin_port() { return origin_port_; }
 
@@ skipping 196 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);
+  // Whether a premier connection is pingable, where a premier connection is
+  // the top-ranked connection on each network.
+  bool IsPremierConnectionPingable(Connection* premier_conn, int64_t now);
   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);
-
+  // Gets all premier connections on all networks.
+  std::map<rtc::Network*, Connection*> GetPremierConnectionsByNetwork() const;
   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.

[pthatcher1, 2016/10/24 20:49:05]

I find this confusing since "best" and "premier" almost mean the same thing. 
What we actually have here is a "best per network" and "best across networks".

Can we have "best" mean "best across networks" and "best for network" mean "best
per network"?  For example, this method could just be
"FindBestConnectionToPing"?  And the method above could be
GetBestConnectionForNetwork(). 

[honghaiz3, 2016/10/24 23:35:09]

Removed this method base on another suggestion. 

+  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 64 matching lines @@
   uint32_t nomination_ = 0;
 
   webrtc::MetricsObserverInterface* metrics_observer_ = nullptr;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(P2PTransportChannel);
 };
 
 }  // namespace cricket
 
 #endif  // WEBRTC_P2P_BASE_P2PTRANSPORTCHANNEL_H_