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/* $OpenBSD: in_cksum.c,v 1.4 2014/07/20 20:27:19 tobias Exp $ */ |
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/* $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. 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/types.h> |
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#include "dvmrpd.h" |
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#include "log.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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u_int16_t |
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in_cksum(void *p, size_t l) |
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{ |
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unsigned int sum = 0; |
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int len; |
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u_char *cp = p; |
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/* ensure that < 2^16 bytes being summed */ |
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if (l >= (1 << 16)) |
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fatalx("in_cksum: packet too big"); |
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len = (int)l; |
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if (((long)cp & 1) == 0) { |
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while (len > 1) { |
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sum += htons(*(u_short *)cp); |
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cp += 2; |
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len -= 2; |
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} |
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} else { |
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while (len > 1) { |
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sum += *cp++ << 8; |
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sum += *cp++; |
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len -= 2; |
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} |
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} |
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if (len == 1) |
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sum += *cp << 8; |
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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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sum = ntohs(sum); |
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return (0xffff & ~sum); |
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} |