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      1  1.2  christos /*	$NetBSD: __cmsg_alignbytes.c,v 1.2 2024/01/20 14:52:46 christos Exp $	*/
      2  1.1     joerg 
      3  1.1     joerg /*-
      4  1.1     joerg  * Copyright (c) 2000 The NetBSD Foundation, Inc.
      5  1.1     joerg  * All rights reserved.
      6  1.1     joerg  *
      7  1.1     joerg  * This code is derived from software contributed to The NetBSD Foundation
      8  1.1     joerg  * by Jun-ichiro Hagino.
      9  1.1     joerg  *
     10  1.1     joerg  * Redistribution and use in source and binary forms, with or without
     11  1.1     joerg  * modification, are permitted provided that the following conditions
     12  1.1     joerg  * are met:
     13  1.1     joerg  * 1. Redistributions of source code must retain the above copyright
     14  1.1     joerg  *    notice, this list of conditions and the following disclaimer.
     15  1.1     joerg  * 2. Redistributions in binary form must reproduce the above copyright
     16  1.1     joerg  *    notice, this list of conditions and the following disclaimer in the
     17  1.1     joerg  *    documentation and/or other materials provided with the distribution.
     18  1.1     joerg  *
     19  1.1     joerg  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  1.1     joerg  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  1.1     joerg  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  1.1     joerg  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  1.1     joerg  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  1.1     joerg  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  1.1     joerg  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  1.1     joerg  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  1.1     joerg  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  1.1     joerg  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  1.1     joerg  * POSSIBILITY OF SUCH DAMAGE.
     30  1.1     joerg  */
     31  1.1     joerg 
     32  1.1     joerg #include <sys/cdefs.h>
     33  1.2  christos __RCSID("$NetBSD: __cmsg_alignbytes.c,v 1.2 2024/01/20 14:52:46 christos Exp $");
     34  1.1     joerg 
     35  1.1     joerg #include "namespace.h"
     36  1.1     joerg #include <sys/types.h>
     37  1.1     joerg #include <sys/param.h>
     38  1.1     joerg #include <sys/sysctl.h>
     39  1.1     joerg #include <sys/socket.h>
     40  1.1     joerg 
     41  1.2  christos #include <compat/include/extern.h>
     42  1.1     joerg 
     43  1.1     joerg int
     44  1.1     joerg __cmsg_alignbytes(void)
     45  1.1     joerg {
     46  1.1     joerg 	static int alignbytes = -1;
     47  1.1     joerg #ifdef HW_ALIGNBYTES
     48  1.1     joerg 	int mib[2];
     49  1.1     joerg 	size_t len;
     50  1.1     joerg 	int ret;
     51  1.1     joerg #endif
     52  1.1     joerg 
     53  1.1     joerg 	if (alignbytes > 0)
     54  1.1     joerg 		return alignbytes;
     55  1.1     joerg 
     56  1.1     joerg #ifdef HW_ALIGNBYTES
     57  1.1     joerg 	mib[0] = CTL_HW;
     58  1.1     joerg 	mib[1] = HW_ALIGNBYTES;
     59  1.1     joerg 	len = sizeof(alignbytes);
     60  1.1     joerg 	ret = sysctl(mib, (u_int) (sizeof(mib) / sizeof(mib[0])),
     61  1.1     joerg 	    (void *)&alignbytes, &len, NULL, (size_t)0);
     62  1.1     joerg 	if (ret >= 0 && alignbytes >= 0)
     63  1.1     joerg 		return alignbytes;
     64  1.1     joerg #endif
     65  1.1     joerg 	/* last resort */
     66  1.1     joerg 	alignbytes = ALIGNBYTES;
     67  1.1     joerg 	return alignbytes;
     68  1.1     joerg }
     69