mirror of
https://git.FreeBSD.org/src.git
synced 2024-12-23 11:18:54 +00:00
84 lines
3.0 KiB
C
84 lines
3.0 KiB
C
/* $NetBSD: in_cksum.c,v 1.3 1995/04/22 13:53:48 cgd Exp $ */
|
|
|
|
/*
|
|
* Copyright (c) 1992 Regents of the University of California.
|
|
* All rights reserved.
|
|
*
|
|
* This software was developed by the Computer Systems Engineering group
|
|
* at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
|
|
* contributed to Berkeley.
|
|
*
|
|
* 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, Lawrence Berkeley Laboratory 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.
|
|
*
|
|
* @(#) Header: in_cksum.c,v 1.1 92/09/11 01:15:55 leres Exp (LBL)
|
|
*/
|
|
|
|
#include <sys/types.h>
|
|
|
|
/*
|
|
* Checksum routine for Internet Protocol family headers.
|
|
* This routine is very heavily used in the network
|
|
* code and should be modified for each CPU to be as fast as possible.
|
|
* In particular, it should not be this one.
|
|
*/
|
|
int
|
|
in_cksum(p, len)
|
|
register void *p;
|
|
register int len;
|
|
{
|
|
register int sum = 0, oddbyte = 0, v = 0;
|
|
register u_char *cp = p;
|
|
|
|
/* we assume < 2^16 bytes being summed */
|
|
while (len > 0) {
|
|
if (oddbyte) {
|
|
sum += v + *cp++;
|
|
len--;
|
|
}
|
|
if (((long)cp & 1) == 0) {
|
|
while ((len -= 2) >= 0) {
|
|
sum += *(u_short *)cp;
|
|
cp += 2;
|
|
}
|
|
} else {
|
|
while ((len -= 2) >= 0) {
|
|
sum += *cp++ << 8;
|
|
sum += *cp++;
|
|
}
|
|
}
|
|
if ((oddbyte = len & 1) != 0)
|
|
v = *cp << 8;
|
|
}
|
|
if (oddbyte)
|
|
sum += v;
|
|
sum = (sum >> 16) + (sum & 0xffff); /* add in accumulated carries */
|
|
sum += sum >> 16; /* add potential last carry */
|
|
return (0xffff & ~sum);
|
|
}
|