1/*	$NetBSD: ip_cksum.c,v 1.1 2006/01/24 17:07:19 christos Exp $	*/
2
3/*
4 * Copyright (c) 1992 Regents of the University of California.
5 * All rights reserved.
6 *
7 * This software was developed by the Computer Systems Engineering group
8 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
9 * contributed to Berkeley.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 *    notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 *    notice, this list of conditions and the following disclaimer in the
18 *    documentation and/or other materials provided with the distribution.
19 * 3. All advertising materials mentioning features or use of this software
20 *    must display the following acknowledgement:
21 *	This product includes software developed by the University of
22 *	California, Lawrence Berkeley Laboratory and its contributors.
23 * 4. Neither the name of the University nor the names of its contributors
24 *    may be used to endorse or promote products derived from this software
25 *    without specific prior written permission.
26 *
27 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
28 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
29 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
30 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
31 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
32 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
33 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
34 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
35 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
36 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
37 * SUCH DAMAGE.
38 *
39 * @(#) Header: in_cksum.c,v 1.1 92/09/11 01:15:55 leres Exp  (LBL)
40 */
41
42#include <sys/types.h>
43#include <sys/socket.h>
44
45#include <net/if.h>
46#include <net/if_ether.h>
47
48#include <netinet/in.h>
49#include <netinet/in_systm.h>
50#include <netinet/ip.h>
51#include <netinet/ip_var.h>
52#include <netinet/udp.h>
53#include <netinet/udp_var.h>
54
55#include <machine/endian.h>
56
57#include "stand.h"
58#include "net.h"
59
60/*
61 * Checksum routine for Internet Protocol family headers.
62 * This routine is very heavily used in the network
63 * code and should be modified for each CPU to be as fast as possible.
64 * In particular, it should not be this one.
65 */
66int
67ip_cksum(const void *p, size_t llen)
68{
69	int sum = 0, oddbyte = 0, v = 0, len = (int)llen;
70	const u_char *cp = p;
71
72	/* we assume < 2^16 bytes being summed */
73	while (len > 0) {
74		if (oddbyte) {
75			sum += v + *cp++;
76			len--;
77		}
78		if (((long)cp & 1) == 0) {
79			while ((len -= 2) >= 0) {
80				sum += *(const u_short *)cp;
81				cp += 2;
82			}
83		} else {
84			while ((len -= 2) >= 0) {
85#if BYTE_ORDER == BIG_ENDIAN
86				sum += *cp++ << 8;
87				sum += *cp++;
88#else
89				sum += *cp++;
90				sum += *cp++ << 8;
91#endif
92			}
93		}
94		if ((oddbyte = len & 1) != 0)
95#if BYTE_ORDER == BIG_ENDIAN
96			v = *cp << 8;
97#else
98			v = *cp;
99#endif
100	}
101	if (oddbyte)
102		sum += v;
103	sum = (sum >> 16) + (sum & 0xffff); /* add in accumulated carries */
104	sum += sum >> 16;		/* add potential last carry */
105	return (0xffff & ~sum);
106}
107