Add a flag to filter out high-cost networks.

webrtc/p2p/client/basicportallocator.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 375 matching lines @@
     network_manager->GetAnyAddressNetworks(networks);
   } else {
     network_manager->GetNetworks(networks);
   }
   networks->erase(std::remove_if(networks->begin(), networks->end(),
                                  [this](rtc::Network* network) {
                                    return allocator_->network_ignore_mask() &
                                           network->type();
                                  }),
                   networks->end());
+
+  if (flags() & PORTALLOCATOR_GATHER_LOW_COST_NETWORK_ONLY) {
+    uint16_t lowest_cost = rtc::kMaxNetworkCost;
+    for (rtc::Network* network : *networks) {
+      uint16_t cost = network->GetCost();
+      if (cost < lowest_cost) {
+        lowest_cost = cost;
+      }
+    }

[pthatcher1, 2016/05/17 20:44:28]

std::min might work here

[honghaiz3, 2016/05/18 05:55:02]

Done.

+    networks->erase(std::remove_if(networks->begin(), networks->end(),
+                                   [lowest_cost](rtc::Network* network) {
+                                     return network->GetCost() > lowest_cost;
+                                   }),
+                    networks->end());

[pthatcher1, 2016/05/17 20:44:28]

We could use a threshold greater than zero (perhaps 50), such as "return
network->GetCost() > lowest_cost + kNetworkCostLow"

[honghaiz3, 2016/05/18 05:55:02]

Done.

+  }
 }
 
 // For each network, see if we have a sequence that covers it already.  If not,
 // create a new sequence to create the appropriate ports.
 void BasicPortAllocatorSession::DoAllocate() {
   bool done_signal_needed = false;
   std::vector<rtc::Network*> networks;
   GetNetworks(&networks);
 
   if (networks.empty()) {
@@ skipping 827 matching lines @@
   ServerAddresses servers;
   for (size_t i = 0; i < relays.size(); ++i) {
     if (relays[i].type == turn_type && SupportsProtocol(relays[i], type)) {
       servers.insert(relays[i].ports.front().address);
     }
   }
   return servers;
 }
 
 }  // namespace cricket