Add code to set TCP keep alive delay on OSX.

net/socket/tcp_socket_libevent.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>
 
@@ skipping 38 matching lines @@
 // After calling this function, the kernel will not wait. See TCP_NODELAY in
 // `man 7 tcp`.
 bool SetTCPNoDelay(int fd, bool no_delay) {
   int on = no_delay ? 1 : 0;
   int error = setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, &on, sizeof(on));
   return error == 0;
 }
 
 // SetTCPKeepAlive sets SO_KEEPALIVE.
 bool SetTCPKeepAlive(int fd, bool enable, int delay) {
+  // Enabling TCP keepalives is the same on all platforms.
   int on = enable ? 1 : 0;
   if (setsockopt(fd, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on))) {
     PLOG(ERROR) << "Failed to set SO_KEEPALIVE on fd: " << fd;
     return false;
   }
 
   // If we disabled TCP keep alive, our work is done here.
   if (!enable)
     return true;
 
 #if defined(OS_LINUX) || defined(OS_ANDROID)
+  // Setting the keepalive interval varies by platform.
+
   // Set seconds until first TCP keep alive.
   if (setsockopt(fd, SOL_TCP, TCP_KEEPIDLE, &delay, sizeof(delay))) {
     PLOG(ERROR) << "Failed to set TCP_KEEPIDLE on fd: " << fd;
     return false;
   }
   // Set seconds between TCP keep alives.
   if (setsockopt(fd, SOL_TCP, TCP_KEEPINTVL, &delay, sizeof(delay))) {
     PLOG(ERROR) << "Failed to set TCP_KEEPINTVL on fd: " << fd;
     return false;
   }
+#elif defined(OS_MACOSX) || defined(OS_IOS)
+  if (setsockopt(fd, IPPROTO_TCP, TCP_KEEPALIVE, &delay, sizeof(delay))) {
+    PLOG(ERROR) << "Failed to set TCP_KEEPALIVE on fd: " << fd;
+    return false;
+  }
 #endif
   return true;
 }
 
 #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;
@@ skipping 642 matching lines @@
     }
   } else {
     tcp_fastopen_status_ =
         (tcp_fastopen_status_ == TCP_FASTOPEN_FAST_CONNECT_RETURN ?
          TCP_FASTOPEN_SYN_DATA_GETSOCKOPT_FAILED :
          TCP_FASTOPEN_NO_SYN_DATA_GETSOCKOPT_FAILED);
   }
 }
 
 }  // namespace net