1/*	$OpenBSD: in_cksum.c,v 1.1 2015/10/02 04:26:47 renato Exp $	*/
2/*	$NetBSD: in_cksum.c,v 1.3 1995/04/22 13:53:48 cgd Exp $	*/
3
4/*
5 * Copyright (c) 1992 Regents of the University of California.
6 * All rights reserved.
7 *
8 * This software was developed by the Computer Systems Engineering group
9 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
10 * contributed to Berkeley.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 *    notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 *    notice, this list of conditions and the following disclaimer in the
19 *    documentation and/or other materials provided with the distribution.
20 * 3. Neither the name of the University nor the names of its contributors
21 *    may be used to endorse or promote products derived from this software
22 *    without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 *
36 * @(#) Header: in_cksum.c,v 1.1 92/09/11 01:15:55 leres Exp  (LBL)
37 */
38
39#include <sys/types.h>
40
41#include "eigrpd.h"
42#include "log.h"
43
44/*
45 * Checksum routine for Internet Protocol family headers.
46 * This routine is very heavily used in the network
47 * code and should be modified for each CPU to be as fast as possible.
48 * In particular, it should not be this one.
49 */
50uint16_t
51in_cksum(void *p, size_t l)
52{
53	unsigned int	 sum = 0;
54	int		 len;
55	unsigned char	*cp = p;
56
57	/* ensure that < 2^16 bytes being summed */
58	if (l >= (1 << 16))
59		fatalx("in_cksum: packet too big");
60	len = (int)l;
61
62	if (((long)cp & 1) == 0) {
63		while (len > 1) {
64			sum += htons(*(unsigned short *)cp);
65			cp += 2;
66			len -= 2;
67		}
68	} else {
69		while (len > 1) {
70			sum += *cp++ << 8;
71			sum += *cp++;
72			len -= 2;
73		}
74	}
75	if (len == 1)
76		sum += *cp << 8;
77
78	sum = (sum >> 16) + (sum & 0xffff); /* add in accumulated carries */
79	sum += sum >> 16;		/* add potential last carry */
80	sum = ntohs(sum);
81	return (0xffff & ~sum);
82}
83