199767f8919635c4928607450d9e0abb932109ceToomas Soome/* $NetBSD: in_cksum.c,v 1.6 2000/03/31 19:55:09 castor Exp $ */
199767f8919635c4928607450d9e0abb932109ceToomas Soome * Copyright (c) 1992 Regents of the University of California.
199767f8919635c4928607450d9e0abb932109ceToomas Soome * All rights reserved.
199767f8919635c4928607450d9e0abb932109ceToomas Soome * This software was developed by the Computer Systems Engineering group
199767f8919635c4928607450d9e0abb932109ceToomas Soome * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
199767f8919635c4928607450d9e0abb932109ceToomas Soome * contributed to Berkeley.
199767f8919635c4928607450d9e0abb932109ceToomas Soome * Redistribution and use in source and binary forms, with or without
199767f8919635c4928607450d9e0abb932109ceToomas Soome * modification, are permitted provided that the following conditions
199767f8919635c4928607450d9e0abb932109ceToomas Soome * 1. Redistributions of source code must retain the above copyright
199767f8919635c4928607450d9e0abb932109ceToomas Soome * notice, this list of conditions and the following disclaimer.
199767f8919635c4928607450d9e0abb932109ceToomas Soome * 2. Redistributions in binary form must reproduce the above copyright
199767f8919635c4928607450d9e0abb932109ceToomas Soome * notice, this list of conditions and the following disclaimer in the
199767f8919635c4928607450d9e0abb932109ceToomas Soome * documentation and/or other materials provided with the distribution.
199767f8919635c4928607450d9e0abb932109ceToomas Soome * 4. Neither the name of the University nor the names of its contributors
199767f8919635c4928607450d9e0abb932109ceToomas Soome * may be used to endorse or promote products derived from this software
199767f8919635c4928607450d9e0abb932109ceToomas Soome * without specific prior written permission.
199767f8919635c4928607450d9e0abb932109ceToomas Soome * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
199767f8919635c4928607450d9e0abb932109ceToomas Soome * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
199767f8919635c4928607450d9e0abb932109ceToomas Soome * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
199767f8919635c4928607450d9e0abb932109ceToomas Soome * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
199767f8919635c4928607450d9e0abb932109ceToomas Soome * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
199767f8919635c4928607450d9e0abb932109ceToomas Soome * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
199767f8919635c4928607450d9e0abb932109ceToomas Soome * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
199767f8919635c4928607450d9e0abb932109ceToomas Soome * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
199767f8919635c4928607450d9e0abb932109ceToomas Soome * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
199767f8919635c4928607450d9e0abb932109ceToomas Soome * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
199767f8919635c4928607450d9e0abb932109ceToomas Soome * SUCH DAMAGE.
199767f8919635c4928607450d9e0abb932109ceToomas Soome * @(#) Header: in_cksum.c,v 1.1 92/09/11 01:15:55 leres Exp (LBL)
199767f8919635c4928607450d9e0abb932109ceToomas Soome * Checksum routine for Internet Protocol family headers.
199767f8919635c4928607450d9e0abb932109ceToomas Soome * This routine is very heavily used in the network
199767f8919635c4928607450d9e0abb932109ceToomas Soome * code and should be modified for each CPU to be as fast as possible.
199767f8919635c4928607450d9e0abb932109ceToomas Soome * In particular, it should not be this one.
199767f8919635c4928607450d9e0abb932109ceToomas Soome /* we assume < 2^16 bytes being summed */
199767f8919635c4928607450d9e0abb932109ceToomas Soome while (len > 0) {
199767f8919635c4928607450d9e0abb932109ceToomas Soome sum = (sum >> 16) + (sum & 0xffff); /* add in accumulated carries */
199767f8919635c4928607450d9e0abb932109ceToomas Soome sum += sum >> 16; /* add potential last carry */