/* * Copyright (c) 1988, 1992, 1993 *	The Regents of the University of California.  All rights reserved. * * 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. * *	@(#)in_cksum.c	8.1 (Berkeley) 6/10/93 * in_cksum.c,v 1.2 1994/08/02 07:48:16 davidg Exp */#include "slirp.h"/* * Checksum routine for Internet Protocol family headers (Portable Version). * * This routine is very heavily used in the network * code and should be modified for each CPU to be as fast as possible. *  * XXX Since we will never span more than 1 mbuf, we can optimise this */#define ADDCARRY(x)  (x > 65535 ? x -= 65535 : x)#define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}int cksum(struct mbuf *m, int len){	register u_int16_t *w;	register int sum = 0;	register int mlen = 0;	int byte_swapped = 0;	union {		u_int8_t	c[2];		u_int16_t	s;	} s_util;	union {		u_int16_t s[2];		u_int32_t l;	} l_util;		if (m->m_len == 0)	   goto cont;	w = mtod(m, u_int16_t *);		mlen = m->m_len;		if (len < mlen)	   mlen = len;	len -= mlen;	/*	 * Force to even boundary.	 */	if ((1 & (long) w) && (mlen > 0)) {		REDUCE;		sum <<= 8;		s_util.c[0] = *(u_int8_t *)w;		w = (u_int16_t *)((int8_t *)w + 1);		mlen--;		byte_swapped = 1;	}	/*	 * Unroll the loop to make overhead from	 * branches &c small.	 */	while ((mlen -= 32) >= 0) {		sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];		sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];		sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];		sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];		w += 16;	}	mlen += 32;	while ((mlen -= 8) >= 0) {		sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];		w += 4;	}	mlen += 8;	if (mlen == 0 && byte_swapped == 0)	   goto cont;	REDUCE;	while ((mlen -= 2) >= 0) {		sum += *w++;	}		if (byte_swapped) {		REDUCE;		sum <<= 8;		byte_swapped = 0;		if (mlen == -1) {			s_util.c[1] = *(u_int8_t *)w;			sum += s_util.s;			mlen = 0;		} else		   		   mlen = -1;	} else if (mlen == -1)	   s_util.c[0] = *(u_int8_t *)w;	cont:#ifdef DEBUG	if (len) {		DEBUG_ERROR((dfd, "cksum: out of data\n"));		DEBUG_ERROR((dfd, " len = %d\n", len));	}#endif	if (mlen == -1) {		/* The last mbuf has odd # of bytes. Follow the		 standard (the odd byte may be shifted left by 8 bits			   or not as determined by endian-ness of the machine) */		s_util.c[1] = 0;		sum += s_util.s;	}	REDUCE;	return (~sum & 0xffff);}