add hurd/hurdsocket.h file missing from a5eb23d

hurd/hurdsocket.h

@@ -0,0 +1,30 @@
+/* Hurd-specific socket functions
+   Copyright (C) 2013-2015 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _HURD_HURDSOCKET_H
+#define _HURD_HURDSOCKET_H
+
+#include <string.h>
+
+/* Returns a duplicate of ADDR->sun_path with LEN limitation.  This
+   should to be used whenever reading a unix socket address, to cope with
+   sun_path possibly not including a trailing \0.  */
+#define _hurd_sun_path_dupa(addr, len) \
+  strndupa ((addr)->sun_path, (len) - offsetof (struct sockaddr_un, sun_path))
+
+#endif /* hurdsocket.h */