WebRTC might leak srflx ip address when multiple_routes disabled and IceTransportType is relay

webrtc/p2p/client/basicportallocator.cc

Index: webrtc/p2p/client/basicportallocator.cc
diff --git a/webrtc/p2p/client/basicportallocator.cc b/webrtc/p2p/client/basicportallocator.cc
index 3c77b4feabaa4a63664dc76cdccf119ca77f91e3..a16c8c469e84e19179d33a40ae9a219646b494c9 100644
--- a/webrtc/p2p/client/basicportallocator.cc
+++ b/webrtc/p2p/client/basicportallocator.cc
@@ -473,9 +473,14 @@ void BasicPortAllocatorSession::OnCandidateReady(
 
   ProtocolType pvalue;
   bool candidate_signalable = CheckCandidateFilter(c);
+
+  // Here we only allow the port if the CF_HOST was originally specified in the
+  // allocator's candidate filter, as when enumeration is disabled, the port's
+  // filter has been modified to prevent local address leakage. If this local
+  // port is not filtered out, it'll send STUN ping and cause IP address leak.

[pthatcher1, 2015/09/30 05:32:10]

I think this could be a little more, perhaps with something like 

"When device enumeration is disabled (to prevent non-default IP addresses from
leaking), we ping from some local candidates even though we don't signal them. 
However, if host candidates are also disabled (for example, to prevent even
default IP addresses from leaking), we still don't want to ping from them, even
if device enumeration is disabled.  Thus, we check for both device enumeration
and host candidates being disabled."

[guoweis_webrtc, 2015/09/30 16:29:28]

Done.

   bool candidate_pairable =
       candidate_signalable ||
-      (c.address().IsAnyIP() &&
+      ((allocator_->candidate_filter() & CF_HOST) && c.address().IsAnyIP() &&
        (port->SharedSocket() || c.protocol() == TCP_PROTOCOL_NAME));

[pthatcher1, 2015/09/30 05:32:10]

This is getting a little hard to read.  Perhaps some named variables would help:

bool network_enumeration_disabled = c.address().IsAnyIP();
bool can_ping_from_candidate = (port->SharedSocket() || c.protocol() ==
TCP_PROTOCOL_NAME);
bool host_canidates_disabled = !(allocator_->candidate_filter() & CF_HOST);
bool candidate_pairable = candidate_signalable || (
  network_enumeration_disabled && can_ping_from_candidate &&  &&
!host_canidates_disabled));

[guoweis_webrtc, 2015/09/30 16:29:28]

Done.

   bool candidate_protocol_enabled =
       StringToProto(c.protocol().c_str(), &pvalue) &&