fbbd9655e5
Renumber cluase 4 to 3, per what everybody else did when BSD granted them permission to remove clause 3. My insistance on keeping the same numbering for legal reasons is too pedantic, so give up on that point. Submitted by: Jan Schaumann <jschauma@stevens.edu> Pull Request: https://github.com/freebsd/freebsd/pull/96
95 lines
2.9 KiB
C
95 lines
2.9 KiB
C
/* $NetBSD: in_cksum.c,v 1.6 2000/03/31 19:55:09 castor Exp $ */
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/*
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* Copyright (c) 1992 Regents of the University of California.
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* All rights reserved.
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*
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* This software was developed by the Computer Systems Engineering group
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* at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
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* contributed to Berkeley.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#) Header: in_cksum.c,v 1.1 92/09/11 01:15:55 leres Exp (LBL)
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/types.h>
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#include <machine/endian.h>
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#include "stand.h"
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/*
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* Checksum routine for Internet Protocol family headers.
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* This routine is very heavily used in the network
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* code and should be modified for each CPU to be as fast as possible.
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* In particular, it should not be this one.
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*/
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int
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in_cksum(p, len)
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void *p;
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int len;
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{
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int sum = 0, oddbyte = 0, v = 0;
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u_char *cp = p;
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/* we assume < 2^16 bytes being summed */
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while (len > 0) {
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if (oddbyte) {
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sum += v + *cp++;
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len--;
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}
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if (((long)cp & 1) == 0) {
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while ((len -= 2) >= 0) {
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sum += *(u_short *)cp;
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cp += 2;
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}
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} else {
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while ((len -= 2) >= 0) {
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#if BYTE_ORDER == BIG_ENDIAN
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sum += *cp++ << 8;
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sum += *cp++;
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#else
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sum += *cp++;
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sum += *cp++ << 8;
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#endif
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}
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}
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if ((oddbyte = len & 1) != 0)
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#if BYTE_ORDER == BIG_ENDIAN
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v = *cp << 8;
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#else
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v = *cp;
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#endif
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}
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if (oddbyte)
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sum += v;
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sum = (sum >> 16) + (sum & 0xffff); /* add in accumulated carries */
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sum += sum >> 16; /* add potential last carry */
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return (0xffff & ~sum);
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}
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