Fix incorrect behavior in checking for TCP FastOpen platform support.

net/socket/tcp_socket_posix.cc

 // Copyright 2013 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/socket/tcp_socket.h"
 
 #include <errno.h>
 #include <netinet/tcp.h>
 #include <sys/socket.h>
 
 #include "base/bind.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/logging.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/posix/eintr_wrapper.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_piece.h"
 #include "base/task_scheduler/post_task.h"
 #include "base/time/time.h"
 #include "net/base/address_list.h"
 #include "net/base/io_buffer.h"
 #include "net/base/ip_endpoint.h"
 #include "net/base/net_errors.h"
 #include "net/base/network_activity_monitor.h"
 #include "net/base/network_change_notifier.h"
 #include "net/base/sockaddr_storage.h"
 #include "net/log/net_log.h"
@@ skipping 58 matching lines @@
 #if defined(OS_LINUX) || defined(OS_ANDROID)
 // Checks if the kernel supports TCP FastOpen.
 bool SystemSupportsTCPFastOpen() {
   const base::FilePath::CharType kTCPFastOpenProcFilePath[] =
       "/proc/sys/net/ipv4/tcp_fastopen";
   std::string system_supports_tcp_fastopen;
   if (!base::ReadFileToString(base::FilePath(kTCPFastOpenProcFilePath),
                               &system_supports_tcp_fastopen)) {
     return false;
   }
-  // The read from /proc should return '1' if TCP FastOpen is enabled in the OS.
+  // The read value from /proc will be set in its least significant bit if
+  // TCP FastOpen is enabled.
+  int read_int = 0;
   if (system_supports_tcp_fastopen.empty() ||
-      (system_supports_tcp_fastopen[0] != '1')) {
+      !StringToInt(StringPiece(system_supports_tcp_fastopen), &read_int) ||

[Randy Smith (Not in Mondays), 2017/02/23 15:15:32]

Are you comfortable with this failing if there's leading whitespace?  The
documentation indicates that it'll return false in those circumstances.

[Jana, 2017/02/24 19:24:44]

I've added whitespace trimming, PTAL.

+      (read_int & 0x1) != 1) {
     return false;
   }
   return true;
 }
 
 void RegisterTCPFastOpenIntentAndSupport(bool user_enabled,
                                          bool system_supported) {
   g_tcp_fastopen_supported = system_supported;
   g_tcp_fastopen_user_enabled = user_enabled;
 }
@@ skipping 686 matching lines @@
     if (info.tcpi_rtt > 0) {
       *out_rtt = base::TimeDelta::FromMicroseconds(info.tcpi_rtt);
       return true;
     }
   }
 #endif  // defined(TCP_INFO)
   return false;
 }
 
 }  // namespace net