Add code to set TCP keep alive delay on OSX.

net/socket/tcp_socket_libevent.cc

Index: net/socket/tcp_socket_libevent.cc
diff --git a/net/socket/tcp_socket_libevent.cc b/net/socket/tcp_socket_libevent.cc
index c5d30e1d5b085ec3781c3ca74044f7402fbd5283..6f9ae23f862e11e29a9df2cab2a806561067a07d 100644
--- a/net/socket/tcp_socket_libevent.cc
+++ b/net/socket/tcp_socket_libevent.cc
@@ -56,6 +56,7 @@ bool SetTCPNoDelay(int fd, bool no_delay) {
 
 // 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;
@@ -66,6 +67,7 @@ bool SetTCPKeepAlive(int fd, bool enable, int delay) {
   if (!enable)
     return true;
 
+// Setting the keepalive interval varies by platform.

[mmenke, 2015/04/07 15:28:06]

Indent here is weird, but that's what git cl format likes.

[ramant (doing other things), 2015/04/08 20:08:38]

Is it possible to move the comment inside #ifdef to get around git cl format
issue.

[mmenke, 2015/04/08 21:22:19]

Done.

 #if defined(OS_LINUX) || defined(OS_ANDROID)
   // Set seconds until first TCP keep alive.
   if (setsockopt(fd, SOL_TCP, TCP_KEEPIDLE, &delay, sizeof(delay))) {
@@ -77,6 +79,11 @@ bool SetTCPKeepAlive(int fd, bool enable, int 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;
 }