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      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 
     10 namespace net {
     11 
     12 namespace {
     13 
     14 #if defined(OS_LINUX)
     15 
     16 // Checks to see if the system supports TCP FastOpen. Notably, it requires
     17 // kernel support. Additionally, this checks system configuration to ensure that
     18 // it's enabled.
     19 bool SystemSupportsTCPFastOpen() {
     20   static const base::FilePath::CharType kTCPFastOpenProcFilePath[] =
     21       "/proc/sys/net/ipv4/tcp_fastopen";
     22   std::string system_enabled_tcp_fastopen;
     23   if (!base::ReadFileToString(
     24           base::FilePath(kTCPFastOpenProcFilePath),
     25           &system_enabled_tcp_fastopen)) {
     26     return false;
     27   }
     28 
     29   // As per http://lxr.linux.no/linux+v3.7.7/include/net/tcp.h#L225
     30   // TFO_CLIENT_ENABLE is the LSB
     31   if (system_enabled_tcp_fastopen.empty() ||
     32       (system_enabled_tcp_fastopen[0] & 0x1) == 0) {
     33     return false;
     34   }
     35 
     36   return true;
     37 }
     38 
     39 #else
     40 
     41 bool SystemSupportsTCPFastOpen() {
     42   return false;
     43 }
     44 
     45 #endif
     46 
     47 bool g_tcp_fastopen_enabled = false;
     48 
     49 }  // namespace
     50 
     51 void SetTCPFastOpenEnabled(bool value) {
     52   g_tcp_fastopen_enabled = value && SystemSupportsTCPFastOpen();
     53 }
     54 
     55 bool IsTCPFastOpenEnabled() {
     56   return g_tcp_fastopen_enabled;
     57 }
     58 
     59 }  // namespace net
     60