POSIX only: Move client socket functionality from TCPClientSocket into TCPSocket.

net/socket/tcp_socket.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 "base/file_util.h"
+#include "base/files/file_path.h"
+
+namespace net {
+
+namespace {
+
+#if defined(OS_LINUX)
+
+// Checks to see if the system supports TCP FastOpen. Notably, it requires
+// kernel support. Additionally, this checks system configuration to ensure that
+// it's enabled.
+bool SystemSupportsTCPFastOpen() {
+  static const base::FilePath::CharType kTCPFastOpenProcFilePath[] =
+      "/proc/sys/net/ipv4/tcp_fastopen";
+  std::string system_enabled_tcp_fastopen;
+  if (!base::ReadFileToString(
+          base::FilePath(kTCPFastOpenProcFilePath),
+          &system_enabled_tcp_fastopen)) {
+    return false;
+  }
+
+  // As per http://lxr.linux.no/linux+v3.7.7/include/net/tcp.h#L225
+  // TFO_CLIENT_ENABLE is the LSB
+  if (system_enabled_tcp_fastopen.empty() ||
+      (system_enabled_tcp_fastopen[0] & 0x1) == 0) {
+    return false;
+  }
+
+  return true;
+}
+
+#else
+
+bool SystemSupportsTCPFastOpen() {
+  return false;
+}
+
+#endif
+
+bool g_tcp_fastopen_enabled = false;
+
+}  // namespace
+
+void SetTCPFastOpenEnabled(bool value) {
+  g_tcp_fastopen_enabled = value && SystemSupportsTCPFastOpen();
+}
+
+bool IsTCPFastOpenEnabled() {
+  return g_tcp_fastopen_enabled;
+}
+
+}  // namespace net