Dampening connection switch.

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 190 matching lines @@
   PortAllocatorSession* allocator_session() {
     return allocator_sessions_.back().get();
   }
 
   // Public for unit tests.
   const std::vector<RemoteCandidate>& remote_candidates() const {
     return remote_candidates_;
   }
 
  private:
-  rtc::Thread* thread() { return worker_thread_; }
+  rtc::Thread* thread() const { return worker_thread_; }
   bool IsGettingPorts() { return allocator_session()->IsGettingPorts(); }
 
   // A transport channel is weak if the current best connection is either
   // not receiving or not writable, or if there is no best connection at all.
   bool weak() const;
   // Returns true if it's possible to send packets on this channel.
   bool ReadyToSend() const;
   void UpdateConnectionStates();
   void RequestSortAndStateUpdate();
   // Start pinging if we haven't already started, and we now have a connection
   // that's pingable.
   void MaybeStartPinging();
 
-  // The methods below return a positive value if a is preferable to b,
-  // a negative value if b is preferable, and 0 if they're equally preferable.
-  int CompareConnectionStates(const cricket::Connection* a,
-                              const cricket::Connection* b) const;
+  // The methods below return a positive value if |a| is preferable to |b|,
+  // a negative value if |b| is preferable, and 0 if they're equally preferable.
+  // If |receiving_unchanged_threshold| is set, then when |b| is receiving and
+  // |a| is not, returns a negative value only if |b| has been in receiving
+  // state and |a| has been in not receiving state since
+  // |receiving_unchanged_threshold| and sets
+  // |missed_receiving_unchanged_threshold| to true otherwise.
+  int CompareConnectionStates(
+      const cricket::Connection* a,
+      const cricket::Connection* b,
+      rtc::Optional<int64_t> receiving_unchanged_threshold,
+      bool* missed_receiving_unchanged_threshold) const;
   int CompareConnectionCandidates(const cricket::Connection* a,
                                   const cricket::Connection* b) const;
   // Compares two connections based on the connection states
   // (writable/receiving/connected), nomination states, last data received time,
   // and static preferences. Does not include latency. Used by both sorting
   // and ShouldSwitchSelectedConnection().
   // Returns a positive value if |a| is better than |b|.
   int CompareConnections(const cricket::Connection* a,
-                         const cricket::Connection* b) const;
+                         const cricket::Connection* b,
+                         rtc::Optional<int64_t> receiving_unchanged_threshold,
+                         bool* missed_receiving_unchanged_threshold) const;
 
   bool PresumedWritable(const cricket::Connection* conn) const;
 
-  bool ShouldSwitchSelectedConnection(const cricket::Connection* selected,
-                                      const cricket::Connection* conn) const;
   void SortConnectionsAndUpdateState();
   void SwitchSelectedConnection(Connection* conn);
   void UpdateState();
   void HandleAllTimedOut();
   void MaybeStopPortAllocatorSessions();
   TransportChannelState ComputeState() const;
 
   Connection* GetBestConnectionOnNetwork(rtc::Network* network) const;
   bool CreateConnections(const Candidate& remote_candidate,
                          PortInterface* origin_port);
@@ skipping 46 matching lines @@
   void OnSentPacket(const rtc::SentPacket& sent_packet);
   void OnReadyToSend(Connection* connection);
   void OnConnectionDestroyed(Connection *connection);
 
   void OnNominated(Connection* conn);
 
   void OnMessage(rtc::Message* pmsg) override;
   void OnCheckAndPing();
   void OnRegatherOnFailedNetworks();
 
-  // Returns true if the new_connection should be selected for transmission.
-  bool ShouldSwitchSelectedConnection(Connection* new_connection) const;
+  // 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);
 
   void PruneConnections();
   bool IsBackupConnection(const Connection* conn) const;
 
   Connection* FindConnectionToPing(int64_t now);
   Connection* FindOldestConnectionNeedingTriggeredCheck(int64_t now);
   // Between |conn1| and |conn2|, this function returns the one which should
   // be pinged first.
   Connection* SelectMostPingableConnection(Connection* conn1,
                                            Connection* conn2);
@@ skipping 66 matching lines @@
   IceConfig config_;
   int last_sent_packet_id_ = -1;  // -1 indicates no packet was sent before.
   bool started_pinging_ = false;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(P2PTransportChannel);
 };
 
 }  // namespace cricket
 
 #endif  // WEBRTC_P2P_BASE_P2PTRANSPORTCHANNEL_H_