81 lines
2.7 KiB
C
81 lines
2.7 KiB
C
/* $OpenBSD: checksum.c,v 1.1 2021/02/26 16:16:37 florian Exp $ */
|
|
|
|
/* Packet assembly code, originally contributed by Archie Cobbs. */
|
|
|
|
/*
|
|
* Copyright (c) 1995, 1996, 1999 The Internet Software Consortium.
|
|
* 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 Internet Software Consortium 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 INTERNET SOFTWARE CONSORTIUM 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 INTERNET SOFTWARE CONSORTIUM 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.
|
|
*
|
|
* This software has been written for the Internet Software Consortium
|
|
* by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
|
|
* Enterprises. To learn more about the Internet Software Consortium,
|
|
* see ``http://www.vix.com/isc''. To learn more about Vixie
|
|
* Enterprises, see ``http://www.vix.com''.
|
|
*/
|
|
|
|
#include <arpa/inet.h>
|
|
|
|
#include <stdint.h>
|
|
|
|
#include "checksum.h"
|
|
|
|
uint32_t
|
|
checksum(uint8_t *buf, uint32_t nbytes, uint32_t sum)
|
|
{
|
|
unsigned int i;
|
|
|
|
/* Checksum all the pairs of bytes first. */
|
|
for (i = 0; i < (nbytes & ~1U); i += 2) {
|
|
sum += (uint16_t)ntohs(*((uint16_t *)(buf + i)));
|
|
if (sum > 0xFFFF)
|
|
sum -= 0xFFFF;
|
|
}
|
|
|
|
/*
|
|
* If there's a single byte left over, checksum it, too.
|
|
* Network byte order is big-endian, so the remaining byte is
|
|
* the high byte.
|
|
*/
|
|
if (i < nbytes) {
|
|
sum += buf[i] << 8;
|
|
if (sum > 0xFFFF)
|
|
sum -= 0xFFFF;
|
|
}
|
|
|
|
return sum;
|
|
}
|
|
|
|
uint32_t
|
|
wrapsum(uint32_t sum)
|
|
{
|
|
sum = ~sum & 0xFFFF;
|
|
return htons(sum);
|
|
}
|