net/socket/tcp_socket.cc

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "net/socket/tcp_socket.h"
   6
   7 #include "base/file_util.h"
   8 #include "base/files/file_path.h"
   9 #include "base/memory/ref_counted.h"
  10 #include "base/threading/worker_pool.h"
  11
  12 namespace net {
  13
  14 namespace {
  15
  16 bool g_tcp_fastopen_enabled = false;
  17
  18 #if defined(OS_LINUX) || defined(OS_ANDROID)
  19
  20 typedef base::RefCountedData<bool> SharedBoolean;
  21
  22 // Checks to see if the system supports TCP FastOpen. Notably, it requires
  23 // kernel support. Additionally, this checks system configuration to ensure that
  24 // it's enabled.
  25 void SystemSupportsTCPFastOpen(scoped_refptr<SharedBoolean> supported) {
  26   supported->data = false;
  27   static const base::FilePath::CharType kTCPFastOpenProcFilePath[] =
  28       "/proc/sys/net/ipv4/tcp_fastopen";
  29   std::string system_enabled_tcp_fastopen;
  30   if (!base::ReadFileToString(base::FilePath(kTCPFastOpenProcFilePath),
  31                               &system_enabled_tcp_fastopen)) {
  32     return;
  33   }
  34
  35   // As per http://lxr.linux.no/linux+v3.7.7/include/net/tcp.h#L225
  36   // TFO_CLIENT_ENABLE is the LSB
  37   if (system_enabled_tcp_fastopen.empty() ||
  38       (system_enabled_tcp_fastopen[0] & 0x1) == 0) {
  39     return;
  40   }
  41
  42   supported->data = true;
  43 }
  44
  45 void EnableCallback(scoped_refptr<SharedBoolean> supported) {
  46   g_tcp_fastopen_enabled = supported->data;
  47 }
  48
  49 // This is asynchronous because it needs to do file IO, and it isn't allowed to
  50 // do that on the IO thread.
  51 void EnableFastOpenIfSupported() {
  52   scoped_refptr<SharedBoolean> supported = new SharedBoolean;
  53   base::WorkerPool::PostTaskAndReply(
  54       FROM_HERE,
  55       base::Bind(SystemSupportsTCPFastOpen, supported),
  56       base::Bind(EnableCallback, supported),
  57       false);
  58 }
  59
  60 #else
  61
  62 void EnableFastOpenIfSupported() {
  63   g_tcp_fastopen_enabled = false;
  64 }
  65
  66 #endif
  67
  68 }  // namespace
  69
  70 void SetTCPFastOpenEnabled(bool value) {
  71   if (value) {
  72     EnableFastOpenIfSupported();
  73   } else {
  74     g_tcp_fastopen_enabled = false;
  75   }
  76 }
  77
  78 bool IsTCPFastOpenEnabled() {
  79   return g_tcp_fastopen_enabled;
  80 }
  81
  82 }  // namespace net