Reset the BWE when the network changes

webrtc/p2p/base/p2ptransportchannel.cc

 /*
  *  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 1139 matching lines @@
   Connection* old_best_connection = best_connection_;
   best_connection_ = conn;
   if (best_connection_) {
     if (old_best_connection) {
       LOG_J(LS_INFO, this) << "Previous best connection: "
                            << old_best_connection->ToString();
     }
     LOG_J(LS_INFO, this) << "New best connection: "
                          << best_connection_->ToString();
     SignalRouteChange(this, best_connection_->remote_candidate());
+    if (NetworkChanged(old_best_connection, best_connection_)) {
+      SignalNetworkChanged(this, best_connection_->port()->Network()->id(), 0);
+    }

[pthatcher1, 2016/03/16 21:22:03]

I think we could use a helper method called GetNetworkRoute(const Connection*
conn) like this:

NetworkRoute route;
if (!conn) {
  route.connected = false;
} else {
  route.local_network_id = new Optional<int>(conn->port()->Network()->id());
  // TODO: Signal remote network ID.
  // route.remote_net_id = conn->remote_candidate->network_id();
}
return route;


And then we can have the code here be:

NetworkRoute old_route = GetNetworkRoute(old_conn);
NetworkRoute new_route = GetNetworkRoute(new_conn);
if (old_route != new_route) {
  SignalNetworkRouteChanged(this, old_route, new_route);
}

Of course, we need to make sure to implement operator== and operator!=

[honghaiz3, 2016/03/17 03:38:27]

Instead of Optional and CandidatePair, I just pass the pointer of
best_connection_, 
It can check if the best_connection is null and it should include every possible
information we will need, and it is sort of equivalent to SelectedCandidatePair
but without the new struct. 

+
   } else {
     LOG_J(LS_INFO, this) << "No best connection";
   }
 }
 
+bool P2PTransportChannel::NetworkChanged(const Connection* old_conn,
+                                         const Connection* new_conn) const {
+  ASSERT(new_conn != nullptr);
+  // Occasionally the best connection may be removed and a new connection is
+  // chosen afterwards, so |old_conn| may be nullptr.
+  if (old_conn == nullptr) {
+    return true;
+  }
+  // A unique network should have been created for each network key, which is
+  // generated from the network interface name, ip prefix, and ip prefix length.
+  return old_conn->port()->Network() != new_conn->port()->Network();
+}
+
 // Warning: UpdateState should eventually be called whenever a connection
 // is added, deleted, or the write state of any connection changes so that the
 // transport controller will get the up-to-date channel state. However it
 // should not be called too often; in the case that multiple connection states
 // change, it should be called after all the connection states have changed. For
 // example, we call this at the end of SortConnections.
 void P2PTransportChannel::UpdateState() {
   state_ = ComputeState();
 
   bool writable = best_connection_ && best_connection_->writable();
@@ skipping 439 matching lines @@
 
   // During the initial state when nothing has been pinged yet, return the first
   // one in the ordered |connections_|.
   return *(std::find_if(connections_.begin(), connections_.end(),
                         [conn1, conn2](Connection* conn) {
                           return conn == conn1 || conn == conn2;
                         }));
 }
 
 }  // namespace cricket