Set TCP keep alive on Linux and Mac.

net/socket/tcp_client_socket_libevent.cc

 // Copyright (c) 2010 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_client_socket.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <netdb.h>
 #include <sys/socket.h>
@@ skipping 27 matching lines @@
 
 // DisableNagle turns off buffering in the kernel. By default, TCP sockets will
 // wait up to 200ms for more data to complete a packet before transmitting.
 // After calling this function, the kernel will not wait. See TCP_NODELAY in
 // `man 7 tcp`.
 int DisableNagle(int fd) {
   int on = 1;
   return setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, &on, sizeof(on));
 }
 
+// SetTCPKeepAlive sets SO_KEEPALIVE.
+void SetTCPKeepAlive(int fd) {
+  int optval = 1;
+  socklen_t optlen = sizeof(optval);
+  if (setsockopt(fd, SOL_SOCKET, SO_KEEPALIVE, &optval, optlen)) {
+    PLOG(ERROR) << "Failed to set SO_KEEPALIVE on fd: " << fd;
+    return;
+  }
+#if defined(OS_LINUX)
+  // Set seconds until first TCP keep alive.
+  optval = 45;
+  if (setsockopt(fd, SOL_TCP, TCP_KEEPIDLE, &optval, optlen)) {
+    PLOG(ERROR) << "Failed to set TCP_KEEPIDLE on fd: " << fd;
+    return;
+  }
+  // Set seconds between TCP keep alives.
+  if (setsockopt(fd, SOL_TCP, TCP_KEEPINTVL, &optval, optlen)) {
+    PLOG(ERROR) << "Failed to set TCP_KEEPINTVL on fd: " << fd;
+    return;
+  }
+#endif
+}
+
 // Convert values from <errno.h> to values from "net/base/net_errors.h"
 int MapPosixError(int os_error) {
   // There are numerous posix error codes, but these are the ones we thus far
   // find interesting.
   switch (os_error) {
     case EAGAIN:
 #if EWOULDBLOCK != EAGAIN
     case EWOULDBLOCK:
 #endif
       return ERR_IO_PENDING;
@@ skipping 428 matching lines @@
   if (SetNonBlocking(socket_)) {
     const int err = errno;
     close(socket_);
     socket_ = kInvalidSocket;
     return err;
   }
 
   // This mirrors the behaviour on Windows. See the comment in
   // tcp_client_socket_win.cc after searching for "NODELAY".
   DisableNagle(socket_);  // If DisableNagle fails, we don't care.
+  SetTCPKeepAlive(socket_);

[wtc, 2011/01/18 20:22:48]

Please add a comment to explain why we need to set the
SO_KEEPALIVE socket option.

 
   return 0;
 }
 
 void TCPClientSocketLibevent::LogConnectCompletion(int net_error) {
   scoped_refptr<NetLog::EventParameters> params;
   if (net_error != OK)
     params = new NetLogIntegerParameter("net_error", net_error);
   net_log_.EndEvent(NetLog::TYPE_TCP_CONNECT, params);
 }
@@ skipping 117 matching lines @@
 
 bool TCPClientSocketLibevent::WasEverUsed() const {
   return use_history_.was_used_to_convey_data();
 }
 
 bool TCPClientSocketLibevent::UsingTCPFastOpen() const {
   return use_tcp_fastopen_;
 }
 
 }  // namespace net