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FreeBSD/Linux Kernel Cross Reference
sys/netipx/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 1.9 1999/08/28 18:21:53 jhay Exp $
   37  */
   38 
   39 #include <sys/param.h>
   40 #include <sys/mbuf.h>
   41 #include <sys/libkern.h>
   42 
   43 #include <netipx/ipx.h>
   44 #include <netipx/ipx_var.h>
   45 
   46 
   47 #define SUMADV  sum += *w++
   48 
   49 u_short
   50 ipx_cksum(struct mbuf *m, int len) {
   51         u_int32_t sum = 0;
   52         u_short *w;
   53         u_char oldtc;
   54         int mlen, words;
   55         struct ipx *ipx;
   56         union {
   57                 u_char  b[2];
   58                 u_short w;
   59         } buf;
   60 
   61         ipx = mtod(m, struct ipx*);
   62         oldtc = ipx->ipx_tc;
   63         ipx->ipx_tc = 0;
   64         w = &ipx->ipx_len;
   65         len -= 2;
   66         mlen = 2;
   67 
   68         for(;;) {
   69                 mlen = imin(m->m_len - mlen, len);
   70                 words = mlen / 2;
   71                 len -= mlen & ~1;
   72                 while (words >= 16) {
   73                         SUMADV; SUMADV; SUMADV; SUMADV;
   74                         SUMADV; SUMADV; SUMADV; SUMADV;
   75                         SUMADV; SUMADV; SUMADV; SUMADV;
   76                         SUMADV; SUMADV; SUMADV; SUMADV;
   77                         words -= 16;
   78                 }
   79                 while (words--)
   80                         SUMADV;
   81                 if (len == 0)
   82                         break;
   83                 mlen &= 1;
   84                 if (mlen) {
   85                         buf.b[0] = *(u_char*)w;
   86                         if (--len == 0) {
   87                                 buf.b[1] = 0;
   88                                 sum += buf.w;
   89                                 break;
   90                         }
   91                 }
   92                 m = m->m_next;
   93                 if (m == NULL)
   94                         break;
   95                 w = mtod(m, u_short*);
   96                 if (mlen) {
   97                         buf.b[1] = *(u_char*)w;
   98                         sum += buf.w;
   99                         ((u_char*)w)++;
  100                         if (--len == 0)
  101                                 break;
  102                 } 
  103         }
  104 
  105         ipx->ipx_tc = oldtc;
  106 
  107         sum = (sum & 0xffff) + (sum >> 16);
  108         if (sum >= 0x10000)
  109                 sum++;
  110         if (sum)
  111                 sum = ~sum;
  112         return (sum);
  113 }

Cache object: a461eb0b3e197d997dcc3496714be104


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