TCP Fast Open Support

Fixes #185

CHANGES.rst

@@ -4,6 +4,15 @@ List of changes
 This file contains the running log of changes applied to each released hitch
 version.
 
+hitch-xxx (unreleased)
+------------------------
+
+* Support for TCP Fast Open. Sinnce kernel version 3.13 Fast Open is enabled by
+  default (Issue: 185_)
+
+.. _185: https://github.com/varnish/hitch/issues/185
+
+
 hitch-1.5.0 (2018-12-17)
 ------------------------
 

configure.ac

@@ -110,6 +110,37 @@ if test "$ac_cv_so_reuseport_works" = yes; then
   AC_DEFINE([SO_REUSEPORT_WORKS], [1], [Define if SO_REUSEPORT works])
 fi
 
+AC_ARG_ENABLE(tfo,
+	AC_HELP_STRING([--enable-tfo],
+		[Enable TCP Fast Open. (default is yes)]),
+	[use_tfo="$enableval"],
+	[use_tfo=yes])
+
+if test x"$use_tfo" != xno; then
+	AC_CACHE_CHECK([whether SO_TFO works],
+		[ac_cv_so_tfo],
+		[AC_RUN_IFELSE(
+			[AC_LANG_PROGRAM([[
+				#include <sys/types.h>
+				#include <sys/socket.h>
+				#include <netinet/tcp.h>
+			]], [[
+				int s = socket(AF_INET, SOCK_STREAM, 0);
+				int i = 5;
+				if (setsockopt(s, SOL_TCP, TCP_FASTOPEN, &i, sizeof i) < 0)
+				return (1);
+				return (0);
+			]])],
+		[ac_cv_so_tfo=yes],
+		[ac_cv_so_tfo=no])
+		]
+	)
+	if test "$ac_cv_so_tfo" != yes; then
+		AC_MSG_ERROR([Socket option TCP_FASTOPEN is not supported by the kernel])
+	fi
+	AC_DEFINE([SO_TFO_WORKS], [1], [TCP Fast Open is enabled])
+fi
+
 SH_TESTS="$(cd $srcdir/src && echo tests/test*.sh)"
 AC_SUBST(SH_TESTS)
 

src/hitch.c

@@ -1326,6 +1326,17 @@ frontend_listen(const struct front_arg *fa, struct listen_sock_head *slist)
 			goto creat_frontend_err;
 		}
 #endif
+
+#ifdef SO_TFO_WORKS
+		if (setsockopt(ls->sock, SOL_TCP, TCP_FASTOPEN,
+			&t, sizeof(int))
+		    < 0) {
+			ERR("{setsockopt-tcp_fastopen}: %s: %s\n", strerror(errno),
+			    fa->pspec);
+			goto creat_frontend_err;
+		}
+#endif
+
 		if(setnonblocking(ls->sock) < 0) {
 			ERR("{listen sock: setnonblocking}: %s: %s\n",
 			    strerror(errno), fa->pspec);