From 2c5858513e2bd00c92f27b356f5bd3ed35b92ce0 Mon Sep 17 00:00:00 2001
From: Stéphane Raimbault <stephane.raimbault@gmail.com>
Date: Wed, 2 Nov 2011 23:42:33 +0100
Subject: [PATCH] Use accept4 with SOCK_CLOEXEC when available (Linux)

---
 configure.ac     | 2 +-
 src/modbus-tcp.c | 8 ++++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index 0d9bc8c..8266b5b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -101,7 +101,7 @@ AC_CHECK_DECLS([__CYGWIN__])
 
 # Checks for library functions.
 AC_FUNC_FORK
-AC_CHECK_FUNCS([gettimeofday inet_ntoa memset select socket strerror strlcpy getaddrinfo])
+AC_CHECK_FUNCS([accept4 getaddrinfo gettimeofday inet_ntoa memset select socket strerror strlcpy])
 
 # Add -Wall -Werror for GCC if not already there
 if test "x$GCC" = "xyes"; then
diff --git a/src/modbus-tcp.c b/src/modbus-tcp.c
index b215b18..11b11f1 100644
--- a/src/modbus-tcp.c
+++ b/src/modbus-tcp.c
@@ -16,6 +16,8 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+/* For accept4 when available */
+#define _GNU_SOURCE
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -526,7 +528,13 @@ int modbus_tcp_accept(modbus_t *ctx, int *socket)
     socklen_t addrlen;
 
     addrlen = sizeof(addr);
+#ifdef HAVE_ACCEPT4
+    /* Inherit socket flags and use accept4 call */
+    ctx->s = accept4(*socket, (struct sockaddr *)&addr, &addrlen, SOCK_CLOEXEC);
+#else
     ctx->s = accept(*socket, (struct sockaddr *)&addr, &addrlen);
+#endif
+
     if (ctx->s == -1) {
         close(*socket);
         *socket = 0;
--
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