Add 16-bit network id to the candidate signaling.

webrtc/base/network.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 155 matching lines @@
   int max_ipv6_networks_;
 
   NetworkMap networks_map_;
   bool ipv6_enabled_;
 
   rtc::scoped_ptr<rtc::Network> ipv4_any_address_network_;
   rtc::scoped_ptr<rtc::Network> ipv6_any_address_network_;
 
   IPAddress default_local_ipv4_address_;
   IPAddress default_local_ipv6_address_;
+  // We use 16 bits to save the bandwidth consumption when sending the network
+  // id over the Internet. It is OK that the 16-bit integer overflows to get a
+  // network id 0 because we only compare the network ids in the old and the new
+  // best connections in the transport channel.
+  uint16_t next_available_network_id_ = 1;
 };
 
 // Basic implementation of the NetworkManager interface that gets list
 // of networks using OS APIs.
 class BasicNetworkManager : public NetworkManagerBase,
                             public MessageHandler,
                             public sigslot::has_slots<> {
  public:
   BasicNetworkManager();
   ~BasicNetworkManager() override;
@@ skipping 146 matching lines @@
   void set_scope_id(int id) { scope_id_ = id; }
 
   // Indicates whether this network should be ignored, perhaps because
   // the IP is 0, or the interface is one we know is invalid.
   bool ignored() const { return ignored_; }
   void set_ignored(bool ignored) { ignored_ = ignored; }
 
   AdapterType type() const { return type_; }
   void set_type(AdapterType type) { type_ = type; }
 
+  // A unique id assigned by the network manager, which may be signaled
+  // to the remote side in the candidate.
+  uint16_t id() const { return id_; }
+  void set_id(uint16_t id) { id_ = id; }
+
   int preference() const { return preference_; }
   void set_preference(int preference) { preference_ = preference; }
 
   // When we enumerate networks and find a previously-seen network is missing,
   // we do not remove it (because it may be used elsewhere). Instead, we mark
   // it inactive, so that we can detect network changes properly.
   bool active() const { return active_; }
   void set_active(bool active) {
     if (active_ == active) {
       return;
@@ skipping 13 matching lines @@
   std::string description_;
   IPAddress prefix_;
   int prefix_length_;
   std::string key_;
   std::vector<InterfaceAddress> ips_;
   int scope_id_;
   bool ignored_;
   AdapterType type_;
   int preference_;
   bool active_ = true;
+  uint16_t id_ = 0;
 
   friend class NetworkManager;
 };
 
 }  // namespace rtc
 
 #endif  // WEBRTC_BASE_NETWORK_H_