--- a/m4/ChangeLog
+++ b/m4/ChangeLog
@@ -1,3 +1,7 @@
+2004-11-09  Bruno Haible  <bruno@clisp.org>
+
+	* sockpfaf.m4: New file.
+
 2004-11-03  Albert Chin <china@thewrittenword.com>
 	    Paul Eggert  <eggert@cs.ucla.edu>
 

new file mode 100644
--- /dev/null
+++ b/m4/sockpfaf.m4
@@ -0,0 +1,41 @@
+# sockpfaf.m4 serial 1
+dnl Copyright (C) 2004 Free Software Foundation, Inc.
+dnl This file is free software, distributed under the terms of the GNU
+dnl General Public License.  As a special exception to the GNU General
+dnl Public License, this file may be distributed as part of a program
+dnl that contains a configuration script generated by Autoconf, under
+dnl the same distribution terms as the rest of that program.
+
+dnl Test for some common socket protocol families (PF_INET, PF_INET6, ...)
+dnl and some common address families (AF_INET, AF_INET6, ...).
+dnl This test assumes that a system supports an address family if and only if
+dnl it supports the corresponding protocol family.
+
+dnl From Bruno Haible.
+
+AC_DEFUN([gl_SOCKET_FAMILIES],
+[
+  AC_MSG_CHECKING(for IPv4 sockets)
+  AC_CACHE_VAL(gl_cv_socket_ipv4,
+    [AC_TRY_COMPILE([#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>],
+[int x = AF_INET; struct in_addr y; struct sockaddr_in z;],
+       gl_cv_socket_ipv4=yes, gl_cv_socket_ipv4=no)])
+  AC_MSG_RESULT($gl_cv_socket_ipv4)
+  if test $gl_cv_socket_ipv4 = yes; then
+    AC_DEFINE(HAVE_IPV4, 1, [Define to 1 if <sys/socket.h> defines AF_INET.])
+  fi
+
+  AC_MSG_CHECKING(for IPv6 sockets)
+  AC_CACHE_VAL(gl_cv_socket_ipv6,
+    [AC_TRY_COMPILE([#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>],
+[int x = AF_INET6; struct in6_addr y; struct sockaddr_in6 z;],
+       gl_cv_socket_ipv6=yes, gl_cv_socket_ipv6=no)])
+  AC_MSG_RESULT($gl_cv_socket_ipv6)
+  if test $gl_cv_socket_ipv6 = yes; then
+    AC_DEFINE(HAVE_IPV6, 1, [Define to 1 if <sys/socket.h> defines AF_INET6.])
+  fi
+])