QUIC - Android - Fix the bug in QuicServerInfoMap iteration when server

net/quic/quic_stream_factory.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/quic/quic_stream_factory.h"
 
 #include <algorithm>
 #include <set>
 #include <utility>
 
@@ skipping 1694 matching lines @@
       if (alternative_service_info.alternative_service.protocol == QUIC) {
         quic_supported_servers_at_startup_.insert(key_value.first);
         break;
       }
     }
   }
 
   if (http_server_properties_->max_server_configs_stored_in_properties() == 0)
     return;
   // Create a temporary QuicServerInfo object to deserialize and to populate the
-  // in-memory crypto server config cache.
+  // in-memory crypto server config cache in the MRU order.
   scoped_ptr<QuicServerInfo> server_info;
   CompletionCallback callback;
-  for (const auto& key_value :
-       http_server_properties_->quic_server_info_map()) {
-    const QuicServerId& server_id = key_value.first;
+  // Get the list of servers to be deserialized first because WaitForDataReady
+  // touches quic_server_info_map.
+  const QuicServerInfoMap& quic_server_info_map =
+      http_server_properties_->quic_server_info_map();
+  std::vector<QuicServerId> server_list(quic_server_info_map.size());
+  for (const auto& key_value : quic_server_info_map)
+    server_list.insert(server_list.begin(), key_value.first);

[Ryan Hamilton, 2016/04/06 04:25:54]

It looks like this is going to be O(n^2) since it adds to the front of the list
each time and then has to move the remaining elements. I wonder if it might be
faster do do something like:

  sever_list[i++] = key_value.first;

When n is 5 n^2 isn't that big, so this isn't a big deal.

[ramant (doing other things), 2016/04/06 04:56:07]

facepalm (thanks for catching this). Used push_back and iterated over the list
in the reverse order.

Done.

+  for (QuicServerId server_id : server_list) {
     server_info.reset(quic_server_info_factory_->GetForServer(server_id));
     if (server_info->WaitForDataReady(callback) == OK) {
       DVLOG(1) << "Initialized server config for: " << server_id.ToString();
       InitializeCachedStateInCryptoConfig(server_id, server_info, nullptr);
     }
   }
 }
 
 void QuicStreamFactory::ProcessGoingAwaySession(
     QuicChromiumClientSession* session,
@@ skipping 31 matching lines @@
   // Since the session was active, there's no longer an
   // HttpStreamFactoryImpl::Job running which can mark it broken, unless the TCP
   // job also fails. So to avoid not using QUIC when we otherwise could, we mark
   // it as recently broken, which means that 0-RTT will be disabled but we'll
   // still race.
   http_server_properties_->MarkAlternativeServiceRecentlyBroken(
       alternative_service);
 }
 
 }  // namespace net