Change the size of the ICE ufrag to 4 bytes

webrtc/p2p/base/relayserver.cc

Index: webrtc/p2p/base/relayserver.cc
diff --git a/webrtc/p2p/base/relayserver.cc b/webrtc/p2p/base/relayserver.cc
index e098cbcd843b5f5e0d99c2513a9e3dd7c5d704d8..37b3371bf753f25446891bb6c66ffaa30aa46cbf 100644
--- a/webrtc/p2p/base/relayserver.cc
+++ b/webrtc/p2p/base/relayserver.cc
@@ -26,9 +26,6 @@ namespace cricket {
 // By default, we require a ping every 90 seconds.
 const int MAX_LIFETIME = 15 * 60 * 1000;
 
-// The number of bytes in each of the usernames we use.
-const uint32_t USERNAME_LENGTH = 16;
-
 // Calls SendTo on the given socket and logs any bad results.
 void Send(rtc::AsyncPacketSocket* socket, const char* bytes, size_t size,
           const rtc::SocketAddress& addr) {
@@ -263,11 +260,14 @@ void RelayServer::OnExternalPacket(
     return;
   }
 
-  uint32_t length =
-      std::min(static_cast<uint32_t>(username_attr->length()), USERNAME_LENGTH);
+  uint32_t length = static_cast<uint32_t>(username_attr->length());
   std::string username(username_attr->bytes(), length);
+  // The username is the substring before colon in username_attr
+  std::string::size_type colonpos = username.find(':');
+  if (colonpos != std::string::npos) {
+    username = username.substr(0, colonpos);
+  }
   // TODO: Check the HMAC.
-
   // The binding should already be present.
   BindingMap::iterator biter = bindings_.find(username);
   if (biter == bindings_.end()) {