common/lib/libc/net/__cmsg_alignbytes.c

   1 /*      $NetBSD: __cmsg_alignbytes.c,v 1.2 2008/04/28 20:22:53 martin Exp $     */
   2
   3 /*-
   4  * Copyright (c) 2000 The NetBSD Foundation, Inc.
   5  * All rights reserved.
   6  *
   7  * This code is derived from software contributed to The NetBSD Foundation
   8  * by Jun-ichiro Hagino.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
  20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
  23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  29  * POSSIBILITY OF SUCH DAMAGE.
  30  */
  31
  32 #if !defined(_KERNEL) && !defined(_STANDALONE)
  33 #include <sys/cdefs.h>
  34 #if defined(LIBC_SCCS) && !defined(lint)
  35 __RCSID("$NetBSD: __cmsg_alignbytes.c,v 1.2 2008/04/28 20:22:53 martin Exp $");
  36 #endif /* LIBC_SCCS and not lint */
  37
  38 #include "namespace.h"
  39 #include <sys/types.h>
  40 #include <sys/param.h>
  41 #include <sys/sysctl.h>
  42 #include <sys/socket.h>
  43 #else
  44 #include <sys/types.h>
  45 #include <sys/param.h>
  46 #include <sys/socket.h>
  47 #endif
  48
  49 int
  50 __cmsg_alignbytes(void)
  51 {
  52         static int alignbytes = -1;
  53 #ifdef HW_ALIGNBYTES
  54         int mib[2];
  55         size_t len;
  56         int ret;
  57 #endif
  58
  59         if (alignbytes > 0)
  60                 return alignbytes;
  61
  62 #ifdef HW_ALIGNBYTES
  63         mib[0] = CTL_HW;
  64         mib[1] = HW_ALIGNBYTES;
  65         len = sizeof(alignbytes);
  66         ret = sysctl(mib, (u_int) (sizeof(mib) / sizeof(mib[0])),
  67             (void *)&alignbytes, &len, NULL, (size_t)0);
  68         if (ret >= 0 && alignbytes >= 0)
  69                 return alignbytes;
  70 #endif
  71         /* last resort */
  72         alignbytes = ALIGNBYTES;
  73         return alignbytes;
  74 }