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in_cksum.c revision 1.7
      1  1.1      cgd /*
      2  1.1      cgd  * Copyright (c) 1988 Regents of the University of California.
      3  1.1      cgd  * All rights reserved.
      4  1.1      cgd  *
      5  1.1      cgd  * Redistribution and use in source and binary forms, with or without
      6  1.1      cgd  * modification, are permitted provided that the following conditions
      7  1.1      cgd  * are met:
      8  1.1      cgd  * 1. Redistributions of source code must retain the above copyright
      9  1.1      cgd  *    notice, this list of conditions and the following disclaimer.
     10  1.1      cgd  * 2. Redistributions in binary form must reproduce the above copyright
     11  1.1      cgd  *    notice, this list of conditions and the following disclaimer in the
     12  1.1      cgd  *    documentation and/or other materials provided with the distribution.
     13  1.1      cgd  * 3. All advertising materials mentioning features or use of this software
     14  1.1      cgd  *    must display the following acknowledgement:
     15  1.1      cgd  *	This product includes software developed by the University of
     16  1.1      cgd  *	California, Berkeley and its contributors.
     17  1.1      cgd  * 4. Neither the name of the University nor the names of its contributors
     18  1.1      cgd  *    may be used to endorse or promote products derived from this software
     19  1.1      cgd  *    without specific prior written permission.
     20  1.1      cgd  *
     21  1.1      cgd  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     22  1.1      cgd  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     23  1.1      cgd  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     24  1.1      cgd  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     25  1.1      cgd  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     26  1.1      cgd  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     27  1.1      cgd  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     28  1.1      cgd  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     29  1.1      cgd  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     30  1.1      cgd  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     31  1.1      cgd  * SUCH DAMAGE.
     32  1.1      cgd  *
     33  1.3      cgd  *	from: @(#)in_cksum.c	7.3 (Berkeley) 6/28/90
     34  1.7  mycroft  *	$Id: in_cksum.c,v 1.7 1994/01/10 23:20:07 mycroft Exp $
     35  1.1      cgd  */
     36  1.1      cgd 
     37  1.7  mycroft #include <sys/param.h>
     38  1.4  mycroft #include <sys/mbuf.h>
     39  1.1      cgd 
     40  1.1      cgd /*
     41  1.1      cgd  * Checksum routine for Internet Protocol family headers (Portable Version).
     42  1.1      cgd  *
     43  1.1      cgd  * This routine is very heavily used in the network
     44  1.1      cgd  * code and should be modified for each CPU to be as fast as possible.
     45  1.1      cgd  */
     46  1.1      cgd 
     47  1.5  mycroft #define	ADDCARRY(x) (x > 65535 ? x -= 65535 : x)
     48  1.5  mycroft #define	REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}
     49  1.1      cgd 
     50  1.6  mycroft int
     51  1.7  mycroft in_cksum(m, len)
     52  1.1      cgd 	register struct mbuf *m;
     53  1.1      cgd 	register int len;
     54  1.1      cgd {
     55  1.1      cgd 	register u_short *w;
     56  1.1      cgd 	register int sum = 0;
     57  1.1      cgd 	register int mlen = 0;
     58  1.1      cgd 	int byte_swapped = 0;
     59  1.1      cgd 
     60  1.1      cgd 	union {
     61  1.1      cgd 		char	c[2];
     62  1.1      cgd 		u_short	s;
     63  1.1      cgd 	} s_util;
     64  1.1      cgd 	union {
     65  1.1      cgd 		u_short s[2];
     66  1.1      cgd 		long	l;
     67  1.1      cgd 	} l_util;
     68  1.1      cgd 
     69  1.1      cgd 	for (;m && len; m = m->m_next) {
     70  1.1      cgd 		if (m->m_len == 0)
     71  1.1      cgd 			continue;
     72  1.1      cgd 		w = mtod(m, u_short *);
     73  1.1      cgd 		if (mlen == -1) {
     74  1.1      cgd 			/*
     75  1.1      cgd 			 * The first byte of this mbuf is the continuation
     76  1.1      cgd 			 * of a word spanning between this mbuf and the
     77  1.1      cgd 			 * last mbuf.
     78  1.1      cgd 			 *
     79  1.5  mycroft 			 * s_util.c[0] is already saved when scanning previous
     80  1.1      cgd 			 * mbuf.
     81  1.1      cgd 			 */
     82  1.1      cgd 			s_util.c[1] = *(char *)w;
     83  1.1      cgd 			sum += s_util.s;
     84  1.1      cgd 			w = (u_short *)((char *)w + 1);
     85  1.1      cgd 			mlen = m->m_len - 1;
     86  1.1      cgd 			len--;
     87  1.1      cgd 		} else
     88  1.1      cgd 			mlen = m->m_len;
     89  1.1      cgd 		if (len < mlen)
     90  1.1      cgd 			mlen = len;
     91  1.1      cgd 		len -= mlen;
     92  1.1      cgd 		/*
     93  1.1      cgd 		 * Force to even boundary.
     94  1.1      cgd 		 */
     95  1.1      cgd 		if ((1 & (int) w) && (mlen > 0)) {
     96  1.1      cgd 			REDUCE;
     97  1.1      cgd 			sum <<= 8;
     98  1.1      cgd 			s_util.c[0] = *(u_char *)w;
     99  1.1      cgd 			w = (u_short *)((char *)w + 1);
    100  1.1      cgd 			mlen--;
    101  1.1      cgd 			byte_swapped = 1;
    102  1.1      cgd 		}
    103  1.1      cgd 		/*
    104  1.1      cgd 		 * Unroll the loop to make overhead from
    105  1.1      cgd 		 * branches &c small.
    106  1.1      cgd 		 */
    107  1.1      cgd 		while ((mlen -= 32) >= 0) {
    108  1.1      cgd 			sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
    109  1.1      cgd 			sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
    110  1.1      cgd 			sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
    111  1.1      cgd 			sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
    112  1.1      cgd 			w += 16;
    113  1.1      cgd 		}
    114  1.1      cgd 		mlen += 32;
    115  1.1      cgd 		while ((mlen -= 8) >= 0) {
    116  1.1      cgd 			sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
    117  1.1      cgd 			w += 4;
    118  1.1      cgd 		}
    119  1.1      cgd 		mlen += 8;
    120  1.1      cgd 		if (mlen == 0 && byte_swapped == 0)
    121  1.1      cgd 			continue;
    122  1.1      cgd 		REDUCE;
    123  1.1      cgd 		while ((mlen -= 2) >= 0) {
    124  1.1      cgd 			sum += *w++;
    125  1.1      cgd 		}
    126  1.1      cgd 		if (byte_swapped) {
    127  1.1      cgd 			REDUCE;
    128  1.1      cgd 			sum <<= 8;
    129  1.1      cgd 			byte_swapped = 0;
    130  1.1      cgd 			if (mlen == -1) {
    131  1.1      cgd 				s_util.c[1] = *(char *)w;
    132  1.1      cgd 				sum += s_util.s;
    133  1.1      cgd 				mlen = 0;
    134  1.1      cgd 			} else
    135  1.1      cgd 				mlen = -1;
    136  1.1      cgd 		} else if (mlen == -1)
    137  1.1      cgd 			s_util.c[0] = *(char *)w;
    138  1.1      cgd 	}
    139  1.1      cgd 	if (len)
    140  1.1      cgd 		printf("cksum: out of data\n");
    141  1.1      cgd 	if (mlen == -1) {
    142  1.1      cgd 		/* The last mbuf has odd # of bytes. Follow the
    143  1.1      cgd 		   standard (the odd byte may be shifted left by 8 bits
    144  1.1      cgd 		   or not as determined by endian-ness of the machine) */
    145  1.1      cgd 		s_util.c[1] = 0;
    146  1.1      cgd 		sum += s_util.s;
    147  1.1      cgd 	}
    148  1.1      cgd 	REDUCE;
    149  1.1      cgd 	return (~sum & 0xffff);
    150  1.1      cgd }
    151