/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright (c) 1996-2001 by Sun Microsystems, Inc.
 * All rights reserved.
 */

#include <sys/types.h>
#include "v4_sum_impl.h"

/*
 * Compute one's complement checksum for IP packet headers.
 */
uint16_t
ipv4cksum(uint16_t *cp, uint16_t count)
{
        uint_t          sum = 0;
        uint_t          oneword = BIT_WRAP;

        if (count == 0)
                return (0);

        count >>= 1;
        while (count--) {
                sum += (uint_t)*cp++;
                if (sum >= oneword) {           /* Wrap carries into low bit */
                        sum -= oneword;
                        sum++;
                }
        }
        return ((uint16_t)~sum);
}