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/*
* Copyright (c) 1995, Mike Mitchell
* Copyright (c) 1982, 1992, 1993
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)ipx_cksum.c
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/mbuf.h>
#include <sys/libkern.h>
#include <netipx/ipx.h>
#include <netipx/ipx_var.h>
#define SUMADV sum += *w++
u_short
ipx_cksum(struct mbuf *m, int len) {
u_int32_t sum = 0;
u_char *w;
u_char oldtc;
int mlen, words;
struct ipx *ipx;
union {
u_char b[2];
u_short w;
} buf;
ipx = mtod(m, struct ipx*);
oldtc = ipx->ipx_tc;
ipx->ipx_tc = 0;
w = (u_char *)&ipx->ipx_len;
len -= 2;
mlen = 2;
for(;;) {
mlen = imin(m->m_len - mlen, len);
words = mlen / 2;
len -= mlen & ~1;
while (words >= 16) {
SUMADV; SUMADV; SUMADV; SUMADV;
SUMADV; SUMADV; SUMADV; SUMADV;
SUMADV; SUMADV; SUMADV; SUMADV;
SUMADV; SUMADV; SUMADV; SUMADV;
words -= 16;
}
while (words--)
SUMADV;
if (len == 0)
break;
mlen &= 1;
if (mlen) {
buf.b[0] = *w;
if (--len == 0) {
buf.b[1] = 0;
sum += buf.w;
break;
}
}
m = m->m_next;
if (m == NULL)
break;
w = mtod(m, u_char *);
if (mlen) {
buf.b[1] = *w;
sum += buf.w;
w++;
if (--len == 0)
break;
}
}
ipx->ipx_tc = oldtc;
sum = (sum & 0xffff) + (sum >> 16);
if (sum >= 0x10000)
sum++;
if (sum)
sum = ~sum;
return (sum);
}
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