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/* $OpenBSD: ns_cksum.c,v 1.2 1997/02/24 14:38:37 niklas Exp $ */
/* $NetBSD: ns_cksum.c,v 1.3 1995/03/08 02:14:53 cgd Exp $ */
/*
* 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.
*
* @(#)ns_cksum.c 8.1 (Berkeley) 6/10/93
*/
#include <sys/param.h>
#include <sys/mbuf.h>
/*
* Checksum routine for Network Systems Protocol Packets (Big-Endian).
*
* This routine is very heavily used in the network
* code and should be modified for each CPU to be as fast as possible.
*/
#define ADDCARRY(x) { if ((x) > 65535) (x) -= 65535; }
#define FOLD(x) {l_util.l = (x); (x) = l_util.s[0] + l_util.s[1]; ADDCARRY(x);}
u_short
ns_cksum(m, len)
register struct mbuf *m;
register int len;
{
register u_int16_t *w;
register int sum = 0;
register int mlen = 0;
register int sum2;
union {
u_int16_t s[2];
int32_t l;
} l_util;
for (;m && len; m = m->m_next) {
if (m->m_len == 0)
continue;
/*
* Each trip around loop adds in
* word from one mbuf segment.
*/
w = mtod(m, u_int16_t *);
if (mlen == -1) {
/*
* There is a byte left from the last segment;
* ones-complement add it into the checksum.
*/
#if BYTE_ORDER == BIG_ENDIAN
sum += *(u_char *)w;
#else
sum += *(u_char *)w << 8;
#endif
sum += sum;
w = (u_int16_t *)(1 + (char *)w);
mlen = m->m_len - 1;
len--;
FOLD(sum);
} else
mlen = m->m_len;
if (len < mlen)
mlen = len;
len -= mlen;
/*
* We can do a 16 bit ones complement sum using
* 32 bit arithmetic registers for adding,
* with carries from the low added
* into the high (by normal carry-chaining)
* so long as we fold back before 16 carries have occured.
*/
if (1 & (long) w)
goto uuuuglyy;
#ifndef TINY
/* -DTINY reduces the size from 1250 to 550, but slows it down by 22% */
while ((mlen -= 32) >= 0) {
sum += w[0]; sum += sum; sum += w[1]; sum += sum;
sum += w[2]; sum += sum; sum += w[3]; sum += sum;
sum += w[4]; sum += sum; sum += w[5]; sum += sum;
sum += w[6]; sum += sum; sum += w[7]; sum += sum;
FOLD(sum);
sum += w[8]; sum += sum; sum += w[9]; sum += sum;
sum += w[10]; sum += sum; sum += w[11]; sum += sum;
sum += w[12]; sum += sum; sum += w[13]; sum += sum;
sum += w[14]; sum += sum; sum += w[15]; sum += sum;
FOLD(sum);
w += 16;
}
mlen += 32;
#endif
while ((mlen -= 8) >= 0) {
sum += w[0]; sum += sum; sum += w[1]; sum += sum;
sum += w[2]; sum += sum; sum += w[3]; sum += sum;
FOLD(sum);
w += 4;
}
mlen += 8;
while ((mlen -= 2) >= 0) {
sum += *w++; sum += sum;
}
goto commoncase;
uuuuglyy:
#if BYTE_ORDER == BIG_ENDIAN
#define ww(n) (((u_char *)w)[n + n + 1])
#define vv(n) (((u_char *)w)[n + n])
#else
#if BYTE_ORDER == LITTLE_ENDIAN
#define vv(n) (((u_char *)w)[n + n + 1])
#define ww(n) (((u_char *)w)[n + n])
#endif
#endif
sum2 = 0;
#ifndef TINY
while ((mlen -= 32) >= 0) {
sum += ww(0); sum += sum; sum += ww(1); sum += sum;
sum += ww(2); sum += sum; sum += ww(3); sum += sum;
sum += ww(4); sum += sum; sum += ww(5); sum += sum;
sum += ww(6); sum += sum; sum += ww(7); sum += sum;
FOLD(sum);
sum += ww(8); sum += sum; sum += ww(9); sum += sum;
sum += ww(10); sum += sum; sum += ww(11); sum += sum;
sum += ww(12); sum += sum; sum += ww(13); sum += sum;
sum += ww(14); sum += sum; sum += ww(15); sum += sum;
FOLD(sum);
sum2 += vv(0); sum2 += sum2; sum2 += vv(1); sum2 += sum2;
sum2 += vv(2); sum2 += sum2; sum2 += vv(3); sum2 += sum2;
sum2 += vv(4); sum2 += sum2; sum2 += vv(5); sum2 += sum2;
sum2 += vv(6); sum2 += sum2; sum2 += vv(7); sum2 += sum2;
FOLD(sum2);
sum2 += vv(8); sum2 += sum2; sum2 += vv(9); sum2 += sum2;
sum2 += vv(10); sum2 += sum2; sum2 += vv(11); sum2 += sum2;
sum2 += vv(12); sum2 += sum2; sum2 += vv(13); sum2 += sum2;
sum2 += vv(14); sum2 += sum2; sum2 += vv(15); sum2 += sum2;
FOLD(sum2);
w += 16;
}
mlen += 32;
#endif
while ((mlen -= 8) >= 0) {
sum += ww(0); sum += sum; sum += ww(1); sum += sum;
sum += ww(2); sum += sum; sum += ww(3); sum += sum;
FOLD(sum);
sum2 += vv(0); sum2 += sum2; sum2 += vv(1); sum2 += sum2;
sum2 += vv(2); sum2 += sum2; sum2 += vv(3); sum2 += sum2;
FOLD(sum2);
w += 4;
}
mlen += 8;
while ((mlen -= 2) >= 0) {
sum += ww(0); sum += sum;
sum2 += vv(0); sum2 += sum2;
w++;
}
sum += (sum2 << 8);
commoncase:
if (mlen == -1) {
#if BYTE_ORDER == BIG_ENDIAN
sum += *(u_char *)w << 8;
#else
sum += *(u_char *)w;
#endif
}
FOLD(sum);
}
if (mlen == -1) {
/* We had an odd number of bytes to sum; assume a garbage
byte of zero and clean up */
sum += sum;
FOLD(sum);
}
/*
* sum has already been kept to low sixteen bits.
* just examine result and exit.
*/
if(sum==0xffff) sum = 0;
return (sum);
}
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