115 lines
3.1 KiB
C
115 lines
3.1 KiB
C
/*
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* Copyright (c) 1995, Mike Mitchell
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* Copyright (c) 1982, 1992, 1993
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* The Regents of the University of California. All rights reserved.
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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, Berkeley 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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* @(#)ipx_cksum.c
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/param.h>
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#include <sys/mbuf.h>
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#include <sys/libkern.h>
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#include <netipx/ipx.h>
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#include <netipx/ipx_var.h>
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#define SUMADV sum += *w++
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u_short
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ipx_cksum(struct mbuf *m, int len) {
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u_int32_t sum = 0;
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u_char *w;
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u_char oldtc;
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int mlen, words;
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struct ipx *ipx;
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union {
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u_char b[2];
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u_short w;
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} buf;
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ipx = mtod(m, struct ipx*);
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oldtc = ipx->ipx_tc;
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ipx->ipx_tc = 0;
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w = (u_char *)&ipx->ipx_len;
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len -= 2;
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mlen = 2;
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for(;;) {
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mlen = imin(m->m_len - mlen, len);
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words = mlen / 2;
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len -= mlen & ~1;
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while (words >= 16) {
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SUMADV; SUMADV; SUMADV; SUMADV;
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SUMADV; SUMADV; SUMADV; SUMADV;
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SUMADV; SUMADV; SUMADV; SUMADV;
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SUMADV; SUMADV; SUMADV; SUMADV;
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words -= 16;
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}
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while (words--)
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SUMADV;
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if (len == 0)
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break;
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mlen &= 1;
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if (mlen) {
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buf.b[0] = *w;
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if (--len == 0) {
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buf.b[1] = 0;
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sum += buf.w;
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break;
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}
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}
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m = m->m_next;
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if (m == NULL)
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break;
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w = mtod(m, u_char *);
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if (mlen) {
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buf.b[1] = *w;
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sum += buf.w;
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w++;
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if (--len == 0)
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break;
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}
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}
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ipx->ipx_tc = oldtc;
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sum = (sum & 0xffff) + (sum >> 16);
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if (sum >= 0x10000)
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sum++;
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if (sum)
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sum = ~sum;
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return (sum);
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}
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