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      1 /*	$NetBSD: __cmsg_alignbytes.c,v 1.2 2024/01/20 14:52:46 christos 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 #include <sys/cdefs.h>
     33 __RCSID("$NetBSD: __cmsg_alignbytes.c,v 1.2 2024/01/20 14:52:46 christos Exp $");
     34 
     35 #include "namespace.h"
     36 #include <sys/types.h>
     37 #include <sys/param.h>
     38 #include <sys/sysctl.h>
     39 #include <sys/socket.h>
     40 
     41 #include <compat/include/extern.h>
     42 
     43 int
     44 __cmsg_alignbytes(void)
     45 {
     46 	static int alignbytes = -1;
     47 #ifdef HW_ALIGNBYTES
     48 	int mib[2];
     49 	size_t len;
     50 	int ret;
     51 #endif
     52 
     53 	if (alignbytes > 0)
     54 		return alignbytes;
     55 
     56 #ifdef HW_ALIGNBYTES
     57 	mib[0] = CTL_HW;
     58 	mib[1] = HW_ALIGNBYTES;
     59 	len = sizeof(alignbytes);
     60 	ret = sysctl(mib, (u_int) (sizeof(mib) / sizeof(mib[0])),
     61 	    (void *)&alignbytes, &len, NULL, (size_t)0);
     62 	if (ret >= 0 && alignbytes >= 0)
     63 		return alignbytes;
     64 #endif
     65 	/* last resort */
     66 	alignbytes = ALIGNBYTES;
     67 	return alignbytes;
     68 }
     69