ipx_cksum.c

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    1 /*
    2  * Copyright (c) 1995, Mike Mitchell
    3  * Copyright (c) 1982, 1992, 1993
    4  *      The Regents of the University of California.  All rights reserved.
    5  *
    6  * Redistribution and use in source and binary forms, with or without
    7  * modification, are permitted provided that the following conditions
    8  * are met:
    9  * 1. Redistributions of source code must retain the above copyright
   10  *    notice, this list of conditions and the following disclaimer.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  * 3. All advertising materials mentioning features or use of this software
   15  *    must display the following acknowledgement:
   16  *      This product includes software developed by the University of
   17  *      California, Berkeley and its contributors.
   18  * 4. Neither the name of the University nor the names of its contributors
   19  *    may be used to endorse or promote products derived from this software
   20  *    without specific prior written permission.
   21  *
   22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   32  * SUCH DAMAGE.
   33  *
   34  *      @(#)ipx_cksum.c
   35  *
   36  * $FreeBSD: src/sys/netipx/ipx_cksum.c,v 1.3.4.2 1999/09/05 08:18:55 peter Exp $
   37  */
   38 
   39 #include <sys/param.h>
   40 #include <sys/mbuf.h>
   41 
   42 #include <netipx/ipx_var.h>
   43 
   44 /*
   45  * Checksum routine for Network Systems Protocol Packets (Big-Endian).
   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)  { if ((x) > 65535) (x) -= 65535; }
   52 #define FOLD(x) {l_util.l = (x); (x) = l_util.s[0] + l_util.s[1]; ADDCARRY(x);}
   53 
   54 u_short
   55 ipx_cksum(m, len)
   56         struct mbuf *m;
   57         int len;
   58 {
   59         register u_short *w;
   60         register int sum = 0;
   61         register int mlen = 0;
   62         register int sum2;
   63 
   64         union {
   65                 u_short s[2];
   66                 long    l;
   67         } l_util;
   68 
   69         for (;m != NULL && len; m = m->m_next) {
   70                 if (m->m_len == 0)
   71                         continue;
   72                 /*
   73                  * Each trip around loop adds in
   74                  * word from one mbuf segment.
   75                  */
   76                 w = mtod(m, u_short *);
   77                 if (mlen == -1) {
   78                         /*
   79                          * There is a byte left from the last segment;
   80                          * ones-complement add it into the checksum.
   81                          */
   82 #if BYTE_ORDER == BIG_ENDIAN
   83                         sum  += *(u_char *)w;
   84 #else
   85                         sum  += *(u_char *)w << 8;
   86 #endif
   87                         sum += sum;
   88                         w = (u_short *)(1 + (char *)w);
   89                         mlen = m->m_len - 1;
   90                         len--;
   91                         FOLD(sum);
   92                 } else
   93                         mlen = m->m_len;
   94                 if (len < mlen)
   95                         mlen = len;
   96                 len -= mlen;
   97                 /*
   98                  * We can do a 16 bit ones complement sum using
   99                  * 32 bit arithmetic registers for adding,
  100                  * with carries from the low added
  101                  * into the high (by normal carry-chaining)
  102                  * so long as we fold back before 16 carries have occured.
  103                  */
  104                 if (1 & (int) w)
  105                         goto uuuuglyy;
  106 #ifndef TINY
  107 /* -DTINY reduces the size from 1250 to 550, but slows it down by 22% */
  108                 while ((mlen -= 32) >= 0) {
  109                         sum += w[0]; sum += sum; sum += w[1]; sum += sum;
  110                         sum += w[2]; sum += sum; sum += w[3]; sum += sum;
  111                         sum += w[4]; sum += sum; sum += w[5]; sum += sum;
  112                         sum += w[6]; sum += sum; sum += w[7]; sum += sum;
  113                         FOLD(sum);
  114                         sum += w[8]; sum += sum; sum += w[9]; sum += sum;
  115                         sum += w[10]; sum += sum; sum += w[11]; sum += sum;
  116                         sum += w[12]; sum += sum; sum += w[13]; sum += sum;
  117                         sum += w[14]; sum += sum; sum += w[15]; sum += sum;
  118                         FOLD(sum);
  119                         w += 16;
  120                 }
  121                 mlen += 32;
  122 #endif
  123                 while ((mlen -= 8) >= 0) {
  124                         sum += w[0]; sum += sum; sum += w[1]; sum += sum;
  125                         sum += w[2]; sum += sum; sum += w[3]; sum += sum;
  126                         FOLD(sum);
  127                         w += 4;
  128                 }
  129                 mlen += 8;
  130                 while ((mlen -= 2) >= 0) {
  131                         sum += *w++; sum += sum;
  132                 }
  133                 goto commoncase;
  134 uuuuglyy:
  135 #if BYTE_ORDER == BIG_ENDIAN
  136 #define ww(n) (((u_char *)w)[n + n + 1])
  137 #define vv(n) (((u_char *)w)[n + n])
  138 #else
  139 #if BYTE_ORDER == LITTLE_ENDIAN
  140 #define vv(n) (((u_char *)w)[n + n + 1])
  141 #define ww(n) (((u_char *)w)[n + n])
  142 #endif
  143 #endif
  144                 sum2 = 0;
  145 #ifndef TINY
  146                 while ((mlen -= 32) >= 0) {
  147                     sum += ww(0); sum += sum; sum += ww(1); sum += sum;
  148                     sum += ww(2); sum += sum; sum += ww(3); sum += sum;
  149                     sum += ww(4); sum += sum; sum += ww(5); sum += sum;
  150                     sum += ww(6); sum += sum; sum += ww(7); sum += sum;
  151                     FOLD(sum);
  152                     sum += ww(8); sum += sum; sum += ww(9); sum += sum;
  153                     sum += ww(10); sum += sum; sum += ww(11); sum += sum;
  154                     sum += ww(12); sum += sum; sum += ww(13); sum += sum;
  155                     sum += ww(14); sum += sum; sum += ww(15); sum += sum;
  156                     FOLD(sum);
  157                     sum2 += vv(0); sum2 += sum2; sum2 += vv(1); sum2 += sum2;
  158                     sum2 += vv(2); sum2 += sum2; sum2 += vv(3); sum2 += sum2;
  159                     sum2 += vv(4); sum2 += sum2; sum2 += vv(5); sum2 += sum2;
  160                     sum2 += vv(6); sum2 += sum2; sum2 += vv(7); sum2 += sum2;
  161                     FOLD(sum2);
  162                     sum2 += vv(8); sum2 += sum2; sum2 += vv(9); sum2 += sum2;
  163                     sum2 += vv(10); sum2 += sum2; sum2 += vv(11); sum2 += sum2;
  164                     sum2 += vv(12); sum2 += sum2; sum2 += vv(13); sum2 += sum2;
  165                     sum2 += vv(14); sum2 += sum2; sum2 += vv(15); sum2 += sum2;
  166                     FOLD(sum2);
  167                     w += 16;
  168                 }
  169                 mlen += 32;
  170 #endif
  171                 while ((mlen -= 8) >= 0) {
  172                     sum += ww(0); sum += sum; sum += ww(1); sum += sum;
  173                     sum += ww(2); sum += sum; sum += ww(3); sum += sum;
  174                     FOLD(sum);
  175                     sum2 += vv(0); sum2 += sum2; sum2 += vv(1); sum2 += sum2;
  176                     sum2 += vv(2); sum2 += sum2; sum2 += vv(3); sum2 += sum2;
  177                     FOLD(sum2);
  178                     w += 4;
  179                 }
  180                 mlen += 8;
  181                 while ((mlen -= 2) >= 0) {
  182                         sum += ww(0); sum += sum;
  183                         sum2 += vv(0); sum2 += sum2;
  184                         w++;
  185                 }
  186                 sum += (sum2 << 8);
  187 commoncase:
  188                 if (mlen == -1) {
  189 #if BYTE_ORDER == BIG_ENDIAN
  190                         sum += *(u_char *)w << 8;
  191 #else
  192                         sum += *(u_char *)w;
  193 #endif
  194                 }
  195                 FOLD(sum);
  196         }
  197         if (mlen == -1) {
  198                 /* We had an odd number of bytes to sum; assume a garbage
  199                    byte of zero and clean up */
  200                 sum += sum;
  201                 FOLD(sum);
  202         }
  203         /*
  204          * sum has already been kept to low sixteen bits.
  205          * just examine result and exit.
  206          */
  207         if(sum == 0xffff)
  208                 sum = 0;
  209         return (sum);
  210 }

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FreeBSD/Linux Kernel Cross Reference sys/netipx/ipx_cksum.c

FreeBSD/Linux Kernel Cross Reference
sys/netipx/ipx_cksum.c