1/*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License, Version 1.0 only
6 * (the "License").  You may not use this file except in compliance
7 * with the License.
8 *
9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10 * or http://www.opensolaris.org/os/licensing.
11 * See the License for the specific language governing permissions
12 * and limitations under the License.
13 *
14 * When distributing Covered Code, include this CDDL HEADER in each
15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16 * If applicable, add the following below this CDDL HEADER, with the
17 * fields enclosed by brackets "[]" replaced with your own identifying
18 * information: Portions Copyright [yyyy] [name of copyright owner]
19 *
20 * CDDL HEADER END
21 */
22/*
23 * Copyright (c) 1996-2001 by Sun Microsystems, Inc.
24 * All rights reserved.
25 */
26
27#pragma ident	"%Z%%M%	%I%	%E% SMI"
28
29#include <sys/types.h>
30#include "v4_sum_impl.h"
31
32/*
33 * Compute one's complement checksum for IP packet headers.
34 */
35uint16_t
36ipv4cksum(uint16_t *cp, uint16_t count)
37{
38	uint_t		sum = 0;
39	uint_t		oneword = BIT_WRAP;
40
41	if (count == 0)
42		return (0);
43
44	count >>= 1;
45	while (count--) {
46		sum += (uint_t)*cp++;
47		if (sum >= oneword) {		/* Wrap carries into low bit */
48			sum -= oneword;
49			sum++;
50		}
51	}
52	return ((uint16_t)~sum);
53}
54