Do not create incompatible TurnPort if the server address family is known.

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 658bac3e88f76114525c0afa044575551b4df31c..bffd70a492e8aa7e97403295347ba66a3c21b0b9 100644
--- a/webrtc/p2p/client/basicportallocator.cc
+++ b/webrtc/p2p/client/basicportallocator.cc
@@ -1296,6 +1296,19 @@ void AllocationSequence::CreateTurnPort(const RelayServerConfig& config) {
       continue;
     }
 
+    // Do not create a port if the server address family is known and does
+    // not match the local IP address family.
+    int server_ip_family = relay_port->address.ipaddr().family();
+    int local_ip_family = network_->GetBestIP().family();

[Taylor Brandstetter, 2016/08/05 20:31:29]

Can just use ip_.family().

[honghaiz3, 2016/08/05 22:04:07]

Done.

+    if (server_ip_family != AF_UNSPEC && server_ip_family != local_ip_family) {

[pthatcher1, 2016/08/03 21:33:08]

What happens if local_ip_family is AF_UNSPEC and server_ip_family isn't?  Is it
possible for GetBestIP() to return an address with AF_UNSPEC?

[Taylor Brandstetter, 2016/08/05 20:31:29]

I agree about this. Even if it's not possible to be AF_UNSPEC right now, a
DCHECK would be useful so we can tell if the assumption changes.

[honghaiz3, 2016/08/05 22:04:07]

It is possible (although very strange) to have a network with AF_UNSPEC address.
Mostly, it will be a NIL address in that case. But if that happens, the Port
will be destroyed soon anyway because of the Iscompatible Check later. 
https://cs.chromium.org/chromium/src/third_party/webrtc/p2p/base/turnport.cc?...
If that happens, even though the TurnPort will fail, it does not necessarily
fail the call. For that reason, I think we'd better not have a DCHECK here.  

[Taylor Brandstetter, 2016/08/05 22:19:26]

Ok, makes sense. So we actually do want to treat AF_UNSPEC as mismatching.

+      LOG(LS_INFO) << "Server and local address families are not compatible. "
+                   << "Server address: "
+                   << relay_port->address.ipaddr().ToString()
+                   << " Local address: " << network_->GetBestIP().ToString();
+      continue;
+    }
+
+
     // Shared socket mode must be enabled only for UDP based ports. Hence
     // don't pass shared socket for ports which will create TCP sockets.
     // TODO(mallinath) - Enable shared socket mode for TURN ports. Disabled