sys/netproto/ns/ns_cksum.c

   1 /*
   2  * Copyright (c) 1982, 1992, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  *
  33  *      @(#)ns_cksum.c  8.1 (Berkeley) 6/10/93
  34  * $FreeBSD: src/sys/netns/ns_cksum.c,v 1.7 1999/08/28 00:49:49 peter Exp $
  35  * $DragonFly: src/sys/netproto/ns/ns_cksum.c,v 1.5 2006/01/14 13:36:40 swildner Exp $
  36  */
  37
  38 #include <sys/param.h>
  39 #include <sys/mbuf.h>
  40 #include <sys/socketvar.h>
  41 #include "ns.h"
  42
  43 /*
  44  * Checksum routine for Network Systems Protocol Packets (Big-Endian).
  45  *
  46  * This routine is very heavily used in the network
  47  * code and should be modified for each CPU to be as fast as possible.
  48  */
  49
  50 #define ADDCARRY(x)  { if ((x) > 65535) (x) -= 65535; }
  51 #define FOLD(x) {l_util.l = (x); (x) = l_util.s[0] + l_util.s[1]; ADDCARRY(x);}
  52
  53 u_short
  54 ns_cksum(struct mbuf *m, int len)
  55 {
  56         u_short *w;
  57         int sum = 0;
  58         int mlen = 0;
  59         int sum2;
  60
  61         union {
  62                 u_short s[2];
  63                 long    l;
  64         } l_util;
  65
  66         for (;m && len; m = m->m_next) {
  67                 if (m->m_len == 0)
  68                         continue;
  69                 /*
  70                  * Each trip around loop adds in
  71                  * word from one mbuf segment.
  72                  */
  73                 w = mtod(m, u_short *);
  74                 if (mlen == -1) {
  75                         /*
  76                          * There is a byte left from the last segment;
  77                          * ones-complement add it into the checksum.
  78                          */
  79 #if BYTE_ORDER == BIG_ENDIAN
  80                         sum  += *(u_char *)w;
  81 #else
  82                         sum  += *(u_char *)w << 8;
  83 #endif
  84                         sum += sum;
  85                         w = (u_short *)(1 + (char *)w);
  86                         mlen = m->m_len - 1;
  87                         len--;
  88                         FOLD(sum);
  89                 } else
  90                         mlen = m->m_len;
  91                 if (len < mlen)
  92                         mlen = len;
  93                 len -= mlen;
  94                 /*
  95                  * We can do a 16 bit ones complement sum using
  96                  * 32 bit arithmetic registers for adding,
  97                  * with carries from the low added
  98                  * into the high (by normal carry-chaining)
  99                  * so long as we fold back before 16 carries have occured.
 100                  */
 101                 if (1 & (int) w)
 102                         goto uuuuglyy;
 103 #ifndef TINY
 104 /* -DTINY reduces the size from 1250 to 550, but slows it down by 22% */
 105                 while ((mlen -= 32) >= 0) {
 106                         sum += w[0]; sum += sum; sum += w[1]; sum += sum;
 107                         sum += w[2]; sum += sum; sum += w[3]; sum += sum;
 108                         sum += w[4]; sum += sum; sum += w[5]; sum += sum;
 109                         sum += w[6]; sum += sum; sum += w[7]; sum += sum;
 110                         FOLD(sum);
 111                         sum += w[8]; sum += sum; sum += w[9]; sum += sum;
 112                         sum += w[10]; sum += sum; sum += w[11]; sum += sum;
 113                         sum += w[12]; sum += sum; sum += w[13]; sum += sum;
 114                         sum += w[14]; sum += sum; sum += w[15]; sum += sum;
 115                         FOLD(sum);
 116                         w += 16;
 117                 }
 118                 mlen += 32;
 119 #endif
 120                 while ((mlen -= 8) >= 0) {
 121                         sum += w[0]; sum += sum; sum += w[1]; sum += sum;
 122                         sum += w[2]; sum += sum; sum += w[3]; sum += sum;
 123                         FOLD(sum);
 124                         w += 4;
 125                 }
 126                 mlen += 8;
 127                 while ((mlen -= 2) >= 0) {
 128                         sum += *w++; sum += sum;
 129                 }
 130                 goto commoncase;
 131 uuuuglyy:
 132 #if BYTE_ORDER == BIG_ENDIAN
 133 #define ww(n) (((u_char *)w)[n + n + 1])
 134 #define vv(n) (((u_char *)w)[n + n])
 135 #else
 136 #if BYTE_ORDER == LITTLE_ENDIAN
 137 #define vv(n) (((u_char *)w)[n + n + 1])
 138 #define ww(n) (((u_char *)w)[n + n])
 139 #endif
 140 #endif
 141                 sum2 = 0;
 142 #ifndef TINY
 143                 while ((mlen -= 32) >= 0) {
 144                     sum += ww(0); sum += sum; sum += ww(1); sum += sum;
 145                     sum += ww(2); sum += sum; sum += ww(3); sum += sum;
 146                     sum += ww(4); sum += sum; sum += ww(5); sum += sum;
 147                     sum += ww(6); sum += sum; sum += ww(7); sum += sum;
 148                     FOLD(sum);
 149                     sum += ww(8); sum += sum; sum += ww(9); sum += sum;
 150                     sum += ww(10); sum += sum; sum += ww(11); sum += sum;
 151                     sum += ww(12); sum += sum; sum += ww(13); sum += sum;
 152                     sum += ww(14); sum += sum; sum += ww(15); sum += sum;
 153                     FOLD(sum);
 154                     sum2 += vv(0); sum2 += sum2; sum2 += vv(1); sum2 += sum2;
 155                     sum2 += vv(2); sum2 += sum2; sum2 += vv(3); sum2 += sum2;
 156                     sum2 += vv(4); sum2 += sum2; sum2 += vv(5); sum2 += sum2;
 157                     sum2 += vv(6); sum2 += sum2; sum2 += vv(7); sum2 += sum2;
 158                     FOLD(sum2);
 159                     sum2 += vv(8); sum2 += sum2; sum2 += vv(9); sum2 += sum2;
 160                     sum2 += vv(10); sum2 += sum2; sum2 += vv(11); sum2 += sum2;
 161                     sum2 += vv(12); sum2 += sum2; sum2 += vv(13); sum2 += sum2;
 162                     sum2 += vv(14); sum2 += sum2; sum2 += vv(15); sum2 += sum2;
 163                     FOLD(sum2);
 164                     w += 16;
 165                 }
 166                 mlen += 32;
 167 #endif
 168                 while ((mlen -= 8) >= 0) {
 169                     sum += ww(0); sum += sum; sum += ww(1); sum += sum;
 170                     sum += ww(2); sum += sum; sum += ww(3); sum += sum;
 171                     FOLD(sum);
 172                     sum2 += vv(0); sum2 += sum2; sum2 += vv(1); sum2 += sum2;
 173                     sum2 += vv(2); sum2 += sum2; sum2 += vv(3); sum2 += sum2;
 174                     FOLD(sum2);
 175                     w += 4;
 176                 }
 177                 mlen += 8;
 178                 while ((mlen -= 2) >= 0) {
 179                         sum += ww(0); sum += sum;
 180                         sum2 += vv(0); sum2 += sum2;
 181                         w++;
 182                 }
 183                 sum += (sum2 << 8);
 184 commoncase:
 185                 if (mlen == -1) {
 186 #if BYTE_ORDER == BIG_ENDIAN
 187                         sum += *(u_char *)w << 8;
 188 #else
 189                         sum += *(u_char *)w;
 190 #endif
 191                 }
 192                 FOLD(sum);
 193         }
 194         if (mlen == -1) {
 195                 /* We had an odd number of bytes to sum; assume a garbage
 196                    byte of zero and clean up */
 197                 sum += sum;
 198                 FOLD(sum);
 199         }
 200         /*
 201          * sum has already been kept to low sixteen bits.
 202          * just examine result and exit.
 203          */
 204         if(sum==0xffff) sum = 0;
 205         return (sum);
 206 }