Ignore errors on SetDoNotFragment on platforms where it is not implemented.

net/quic/chromium/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/chromium/quic_stream_factory.h"
 
 #include <openssl/aead.h>
 
 #include <algorithm>
 #include <tuple>
@@ skipping 1688 matching lines @@
     return rv;
   }
 
   rv = socket->SetReceiveBufferSize(socket_receive_buffer_size_);
   if (rv != OK) {
     HistogramCreateSessionFailure(CREATION_ERROR_SETTING_RECEIVE_BUFFER);
     return rv;
   }
 
   rv = socket->SetDoNotFragment();
-  if (rv != OK) {
+  // SetDoNotFragment is not implemented on all platforms, so ignore errors.
+  if (rv != OK && rv != ERR_NOT_IMPLEMENTED) {

[Ryan Hamilton, 2016/08/27 21:55:56]

Alternatively, we could ignore ALL errors since it's not crucial if this does
not succeed. That being said, from UMA, it's only failing on OS X so this fix is
sufficient.

     HistogramCreateSessionFailure(CREATION_ERROR_SETTING_NO_NOT_FRAGMENT);

[mef, 2016/08/29 19:27:14]

nit: This should probably be CREATION_ERROR_SETTING_DO_NOT_FRAGMENT
(s/_NO_/_DO_/).

[Ryan Hamilton, 2016/08/29 19:42:48]

Good point. Will do so in a followup since this has been a bear to land)

[Ryan Hamilton, 2016/08/29 23:31:15]

Ok, I gave up on the CQ and landed this manually, so I fixed this. Done.

     return rv;
   }
 
   // Set a buffer large enough to contain the initial CWND's worth of packet
   // to work around the problem with CHLO packets being sent out with the
   // wrong encryption level, when the send buffer is full.
   rv = socket->SetSendBufferSize(kMaxPacketSize * 20);
   if (rv != OK) {
     HistogramCreateSessionFailure(CREATION_ERROR_SETTING_SEND_BUFFER);
     return rv;
@@ skipping 305 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