87 lines
3.0 KiB
C
87 lines
3.0 KiB
C
/* $NetBSD: in_cksum.c,v 1.3 1995/04/22 13:53:48 cgd 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. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Lawrence Berkeley Laboratory and its contributors.
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* 4. 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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/*
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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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sum += *cp++ << 8;
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sum += *cp++;
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}
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}
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if ((oddbyte = len & 1) != 0)
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v = *cp << 8;
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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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