sys/netinet/in_cksum.c

   1 /*      $OpenBSD: in_cksum.c,v 1.3 1997/02/24 14:06:35 niklas Exp $     */
   2 /*      $NetBSD: in_cksum.c,v 1.11 1996/04/08 19:55:37 jonathan Exp $   */
   3
   4 /*
   5  * Copyright (c) 1988, 1992, 1993
   6  *      The Regents of the University of California.  All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  *
  36  *      @(#)in_cksum.c  8.1 (Berkeley) 6/10/93
  37  */
  38
  39 #include <sys/param.h>
  40 #include <sys/mbuf.h>
  41 #include <sys/systm.h>
  42 #include <netinet/in.h>
  43
  44 /*
  45  * Checksum routine for Internet Protocol family headers (Portable Version).
  46  *
  47  * This routine is very heavily used in the network
  48  * code and should be modified for each CPU to be as fast as possible.
  49  */
  50
  51 #define ADDCARRY(x)  (x > 65535 ? x -= 65535 : x)
  52 #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}
  53
  54 int
  55 in_cksum(m, len)
  56         register struct mbuf *m;
  57         register int len;
  58 {
  59         register u_int16_t *w;
  60         register int sum = 0;
  61         register int mlen = 0;
  62         int byte_swapped = 0;
  63
  64         union {
  65                 u_int8_t  c[2];
  66                 u_int16_t s;
  67         } s_util;
  68         union {
  69                 u_int16_t s[2];
  70                 u_int32_t l;
  71         } l_util;
  72
  73         for (;m && len; m = m->m_next) {
  74                 if (m->m_len == 0)
  75                         continue;
  76                 w = mtod(m, u_int16_t *);
  77                 if (mlen == -1) {
  78                         /*
  79                          * The first byte of this mbuf is the continuation
  80                          * of a word spanning between this mbuf and the
  81                          * last mbuf.
  82                          *
  83                          * s_util.c[0] is already saved when scanning previous
  84                          * mbuf.
  85                          */
  86                         s_util.c[1] = *(u_int8_t *)w;
  87                         sum += s_util.s;
  88                         w = (u_int16_t *)((u_int8_t *)w + 1);
  89                         mlen = m->m_len - 1;
  90                         len--;
  91                 } else
  92                         mlen = m->m_len;
  93                 if (len < mlen)
  94                         mlen = len;
  95                 len -= mlen;
  96                 /*
  97                  * Force to even boundary.
  98                  */
  99                 if ((1 & (long) w) && (mlen > 0)) {
 100                         REDUCE;
 101                         sum <<= 8;
 102                         s_util.c[0] = *(u_int8_t *)w;
 103                         w = (u_int16_t *)((int8_t *)w + 1);
 104                         mlen--;
 105                         byte_swapped = 1;
 106                 }
 107                 /*
 108                  * Unroll the loop to make overhead from
 109                  * branches &c small.
 110                  */
 111                 while ((mlen -= 32) >= 0) {
 112                         sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
 113                         sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
 114                         sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
 115                         sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
 116                         w += 16;
 117                 }
 118                 mlen += 32;
 119                 while ((mlen -= 8) >= 0) {
 120                         sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
 121                         w += 4;
 122                 }
 123                 mlen += 8;
 124                 if (mlen == 0 && byte_swapped == 0)
 125                         continue;
 126                 REDUCE;
 127                 while ((mlen -= 2) >= 0) {
 128                         sum += *w++;
 129                 }
 130                 if (byte_swapped) {
 131                         REDUCE;
 132                         sum <<= 8;
 133                         byte_swapped = 0;
 134                         if (mlen == -1) {
 135                                 s_util.c[1] = *(u_int8_t *)w;
 136                                 sum += s_util.s;
 137                                 mlen = 0;
 138                         } else
 139                                 mlen = -1;
 140                 } else if (mlen == -1)
 141                         s_util.c[0] = *(u_int8_t *)w;
 142         }
 143         if (len)
 144                 printf("cksum: out of data\n");
 145         if (mlen == -1) {
 146                 /* The last mbuf has odd # of bytes. Follow the
 147                    standard (the odd byte may be shifted left by 8 bits
 148                    or not as determined by endian-ness of the machine) */
 149                 s_util.c[1] = 0;
 150                 sum += s_util.s;
 151         }
 152         REDUCE;
 153         return (~sum & 0xffff);
 154 }