/
in_cksum.c
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/
in_cksum.c
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/* $NetBSD: in_cksum.c,v 1.19 2005/12/11 12:24:57 christos Exp $ */
/*
* Copyright (c) 1988, 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. 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.
*
* @(#)in_cksum.c 8.1 (Berkeley) 6/10/93
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: in_cksum.c,v 1.19 2005/12/11 12:24:57 christos Exp $");
#include <sys/param.h>
#include <sys/mbuf.h>
#include <sys/systm.h>
#include <netinet/in.h>
/*
* Checksum routine for Internet Protocol family headers (Portable Version).
*
* 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) (x > 65535 ? x -= 65535 : x)
#define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}
int
in_cksum(struct mbuf *m, int len)
{
u_int16_t *w;
int sum = 0;
int mlen = 0;
int byte_swapped = 0;
union {
u_int8_t c[2];
u_int16_t s;
} s_util;
union {
u_int16_t s[2];
u_int32_t l;
} l_util;
for (;m && len; m = m->m_next) {
if (m->m_len == 0)
continue;
w = mtod(m, u_int16_t *);
if (mlen == -1) {
/*
* The first byte of this mbuf is the continuation
* of a word spanning between this mbuf and the
* last mbuf.
*
* s_util.c[0] is already saved when scanning previous
* mbuf.
*/
s_util.c[1] = *(u_int8_t *)w;
sum += s_util.s;
w = (u_int16_t *)((u_int8_t *)w + 1);
mlen = m->m_len - 1;
len--;
} else
mlen = m->m_len;
if (len < mlen)
mlen = len;
len -= mlen;
/*
* Force to even boundary.
*/
if ((1 & (long) w) && (mlen > 0)) {
REDUCE;
sum <<= 8;
s_util.c[0] = *(u_int8_t *)w;
w = (u_int16_t *)((int8_t *)w + 1);
mlen--;
byte_swapped = 1;
}
/*
* Unroll the loop to make overhead from
* branches &c small.
*/
while ((mlen -= 32) >= 0) {
sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
w += 16;
}
mlen += 32;
while ((mlen -= 8) >= 0) {
sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
w += 4;
}
mlen += 8;
if (mlen == 0 && byte_swapped == 0)
continue;
REDUCE;
while ((mlen -= 2) >= 0) {
sum += *w++;
}
if (byte_swapped) {
REDUCE;
sum <<= 8;
byte_swapped = 0;
if (mlen == -1) {
s_util.c[1] = *(u_int8_t *)w;
sum += s_util.s;
mlen = 0;
} else
mlen = -1;
} else if (mlen == -1)
s_util.c[0] = *(u_int8_t *)w;
}
if (len)
printf("cksum: out of data\n");
if (mlen == -1) {
/* The last mbuf has odd # of bytes. Follow the
standard (the odd byte may be shifted left by 8 bits
or not as determined by endian-ness of the machine) */
s_util.c[1] = 0;
sum += s_util.s;
}
REDUCE;
return (~sum & 0xffff);
}