/* $NetBSD: in_cksum.c,v 1.7 1997/09/02 13:18:15 thorpej Exp $ */

/*-
 * SPDX-License-Identifier: BSD-4-Clause
 *
 * Copyright (c) 1988, 1992, 1993
 *	The Regents of the University of California.  All rights reserved.
 * Copyright (c) 1996
 *	Matt Thomas <matt@3am-software.com>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>			/* RCS ID & Copyright macro defns */
#include <sys/param.h>
#include <sys/mbuf.h>
#include <sys/systm.h>
#include <netinet/in_systm.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <machine/in_cksum.h>

/*
 * Checksum routine for Internet Protocol family headers
 *    (Portable Alpha version).
 *
 * This routine is very heavily used in the network
 * code and should be modified for each CPU to be as fast as possible.
 */

#define ADDCARRY(x)  (x > 65535 ? x -= 65535 : x)
#define REDUCE32							  \
    {									  \
	q_util.q = sum;							  \
	sum = q_util.s[0] + q_util.s[1] + q_util.s[2] + q_util.s[3];	  \
    }
#define REDUCE16							  \
    {									  \
	q_util.q = sum;							  \
	l_util.l = q_util.s[0] + q_util.s[1] + q_util.s[2] + q_util.s[3]; \
	sum = l_util.s[0] + l_util.s[1];				  \
	ADDCARRY(sum);							  \
    }

union l_util {
	u_int16_t s[2];
	u_int32_t l;
};
union q_util {
	u_int16_t s[4];
	u_int32_t l[2];
	u_int64_t q;
};

u_short
in_addword(u_short a, u_short b)
{
	u_int64_t sum = a + b;

	ADDCARRY(sum);
	return (sum);
}

static
uint64_t _do_cksum(void *addr, int len)
{
	uint64_t sum;
	union q_util q_util;

	sum = do_cksum(addr, len);
	REDUCE32;
	return (sum);
}

u_short
in_cksum_skip(struct mbuf *m, int len, int skip)
{
	u_int64_t sum = 0;
	int mlen = 0;
	int clen = 0;
	caddr_t addr;
	union q_util q_util;
	union l_util l_util;

        len -= skip;
        for (; skip && m; m = m->m_next) {
                if (m->m_len > skip) {
                        mlen = m->m_len - skip;
			addr = mtod(m, caddr_t) + skip;
                        goto skip_start;
                } else {
                        skip -= m->m_len;
                }
        }

	for (; m && len; m = m->m_next) {
		if (m->m_len == 0)
			continue;
		mlen = m->m_len;
		addr = mtod(m, caddr_t);
skip_start:
		if (len < mlen)
			mlen = len;

		if ((clen ^ (int) addr) & 1)
		    sum += _do_cksum(addr, mlen) << 8;
		else
		    sum += _do_cksum(addr, mlen);

		clen += mlen;
		len -= mlen;
	}
	REDUCE16;
	return (~sum & 0xffff);
}

u_int in_cksum_hdr(const struct ip *ip)
{
	u_int64_t sum = do_cksum(ip, sizeof(struct ip));
	union q_util q_util;
    	union l_util l_util;
	REDUCE16;
	return (~sum & 0xffff);
}