Adding IceConfig option to assume TURN/TURN candidate pairs will work.

webrtc/p2p/base/port.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 160 matching lines @@
   void set_component(int component) { component_ = component; }
 
   bool send_retransmit_count_attribute() const {
     return send_retransmit_count_attribute_;
   }
   void set_send_retransmit_count_attribute(bool enable) {
     send_retransmit_count_attribute_ = enable;
   }
 
   // Identifies the generation that this port was created in.
-  uint32_t generation() { return generation_; }
+  uint32_t generation() const { return generation_; }
   void set_generation(uint32_t generation) { generation_ = generation; }
 
   const std::string username_fragment() const;
   const std::string& password() const { return password_; }
 
   // May be called when this port was initially created by a pooled
   // PortAllocatorSession, and is now being assigned to an ICE transport.
   // Updates the information for candidates as well.
   void SetIceParameters(int component,
                         const std::string& username_fragment,
@@ skipping 236 matching lines @@
     STATE_FAILED        // Check for this connection failed.
   };
 
   virtual ~Connection();
 
   // The local port where this connection sends and receives packets.
   Port* port() { return port_; }
   const Port* port() const { return port_; }
 
   // Implementation of virtual methods in CandidatePairInterface.
-  // Returns the description of the local port
+  // Returns the description of the local port.
   virtual const Candidate& local_candidate() const;
   // Returns the description of the remote port to which we communicate.
   virtual const Candidate& remote_candidate() const;
 
   // Returns the pair priority.
   uint64_t priority() const;
 
   enum WriteState {
-    STATE_WRITABLE          = 0,  // we have received ping responses recently
-    STATE_WRITE_UNRELIABLE  = 1,  // we have had a few ping failures
-    STATE_WRITE_INIT        = 2,  // we have yet to receive a ping response
-    STATE_WRITE_TIMEOUT     = 3,  // we have had a large number of ping failures
+    STATE_WRITABLE = 0,           // We have received ping responses recently.
+    STATE_PRESUMED_WRITABLE = 1,  // We haven't received a ping response, but
+                                  // we presume we're writable, because we're a
+                                  // TURN-TURN connection and CreatePermission
+                                  // isn't required.
+    STATE_WRITE_UNRELIABLE = 2,   // We have had a few ping failures.
+    STATE_WRITE_INIT = 3,         // We have yet to receive a ping response.
+    STATE_WRITE_TIMEOUT = 4,  // We have had a large number of ping failures.
   };
 
   WriteState write_state() const { return write_state_; }
   bool writable() const { return write_state_ == STATE_WRITABLE; }
+  bool presumed_writable() const {
+    return write_state_ == STATE_WRITABLE ||
+           write_state_ == STATE_PRESUMED_WRITABLE;
+  }
   bool receiving() const { return receiving_; }
 
   // Determines whether the connection has finished connecting.  This can only
   // be false for TCP connections.
   bool connected() const { return connected_; }
   bool weak() const { return !(writable() && receiving() && connected()); }
   bool active() const {
     return write_state_ != STATE_WRITE_TIMEOUT;
   }
   // A connection is dead if it can be safely deleted.
@@ skipping 117 matching lines @@
   void MaybeUpdatePeerReflexiveCandidate(const Candidate& new_candidate);
 
   // Returns the last received time of any data, stun request, or stun
   // response in milliseconds
   int64_t last_received() const;
 
  protected:
   enum { MSG_DELETE = 0, MSG_FIRST_AVAILABLE };
 
   // Constructs a new connection to the given remote port.
-  Connection(Port* port, size_t index, const Candidate& candidate);
+  Connection(Port* port,
+             size_t index,
+             const Candidate& candidate,
+             const IceConfig& config);
 
   // Called back when StunRequestManager has a stun packet to send
   void OnSendStunPacket(const void* data, size_t size, StunRequest* req);
 
   // Callbacks from ConnectionRequest
   virtual void OnConnectionRequestResponse(ConnectionRequest* req,
                                            StunMessage* response);
   void OnConnectionRequestErrorResponse(ConnectionRequest* req,
                                         StunMessage* response);
   void OnConnectionRequestTimeout(ConnectionRequest* req);
   void OnConnectionRequestSent(ConnectionRequest* req);
 
+  // May be STATE_WRITE_INIT or STATE_PRESUMED_WRITABLE depending on ICE
+  // config and candidate types.
+  WriteState InitialWriteState() const;
+
   // Changes the state and signals if necessary.
   void set_write_state(WriteState value);
   void set_receiving(bool value);
   void set_state(State state);
   void set_connected(bool value);
 
   void OnMessage(rtc::Message *pmsg);
 
   Port* port_;
   size_t local_candidate_index_;
@@ skipping 28 matching lines @@
  private:
   void MaybeAddPrflxCandidate(ConnectionRequest* request,
                               StunMessage* response);
 
   bool reported_;
   State state_;
   // Time duration to switch from receiving to not receiving.
   int receiving_timeout_;
   int64_t time_created_ms_;
   int num_pings_sent_ = 0;
+  bool presume_writable_when_fully_relayed_;
 
   friend class Port;
   friend class ConnectionRequest;
 };
 
 // ProxyConnection defers all the interesting work to the port.
 class ProxyConnection : public Connection {
  public:
-  ProxyConnection(Port* port, size_t index, const Candidate& remote_candidate);
+  ProxyConnection(Port* port,
+                  size_t index,
+                  const Candidate& remote_candidate,
+                  const IceConfig& config);
 
   int Send(const void* data,
            size_t size,
            const rtc::PacketOptions& options) override;
   int GetError() override { return error_; }
 
  private:
   int error_ = 0;
 };
 
 }  // namespace cricket
 
 #endif  // WEBRTC_P2P_BASE_PORT_H_