Support TCP_DEFER_ACCEPT sockopts for listeners

A listening socket can be enabled with the sockopt
TCP_DEFER_ACCEPT. This informs the kernel to not call the user-land
accept() until real data has been written to the socket.

A new flag LEV_OPT_DEFERRED_ACCEPT has been introduced to
automatically set this option. Optionally
evutil_make_tcp_listen_socket_deferred() can be called manually.

(Tweaked slightly by nickm.)

1 files changed, 17 insertions, 0 deletions

diff --git a/evutil.c b/evutil.c
index bc81a093..c340b54a 100644
--- a/evutil.c
+++ b/evutil.c
@@ -64,6 +64,9 @@
 #ifdef _EVENT_HAVE_NETINET_IN6_H
 #include <netinet/in6.h>
 #endif
+#ifdef _EVENT_HAVE_NETINET_TCP_H
+#include <netinet/tcp.h>
+#endif
 #ifdef _EVENT_HAVE_ARPA_INET_H
 #include <arpa/inet.h>
 #endif
@@ -365,6 +368,20 @@ evutil_make_listen_socket_reuseable(evutil_socket_t sock)
 }
 
 int
+evutil_make_tcp_listen_socket_deferred(evutil_socket_t sock)
+{
+#if defined(_EVENT_HAVE_NETINET_TCP_H) && defined(TCP_DEFER_ACCEPT)
+	int one = 1;
+
+	/* TCP_DEFER_ACCEPT tells the kernel to call defer accept() only after data
+	 * has arrived and ready to read */ 
+	return setsockopt(sock, IPPROTO_TCP, TCP_DEFER_ACCEPT, &one,
+		(ev_socklen_t)sizeof(one)); 
+#endif
+	return 0;
+}
+
+int
 evutil_make_socket_closeonexec(evutil_socket_t fd)
 {
 #if !defined(_WIN32) && defined(_EVENT_HAVE_SETFD)