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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 
   37 #include <sys/cdefs.h>
   38 __FBSDID("$FreeBSD: src/sys/netipx/ipx_cksum.c,v 1.11.2.2 2005/02/25 13:26:39 rwatson Exp $");
   39 
   40 #include <sys/param.h>
   41 #include <sys/mbuf.h>
   42 #include <sys/libkern.h>
   43 
   44 #include <netipx/ipx.h>
   45 #include <netipx/ipx_var.h>
   46 
   47 
   48 #define SUMADV  sum += *w++
   49 
   50 u_short
   51 ipx_cksum(struct mbuf *m, int len) {
   52         u_int32_t sum = 0;
   53         u_char *w;
   54         u_char oldtc;
   55         int mlen, words;
   56         struct ipx *ipx;
   57         union {
   58                 u_char  b[2];
   59                 u_short w;
   60         } buf;
   61 
   62         ipx = mtod(m, struct ipx*);
   63         oldtc = ipx->ipx_tc;
   64         ipx->ipx_tc = 0;
   65         w = (u_char *)&ipx->ipx_len;
   66         len -= 2;
   67         mlen = 2;
   68 
   69         for(;;) {
   70                 mlen = imin(m->m_len - mlen, len);
   71                 words = mlen / 2;
   72                 len -= mlen & ~1;
   73                 while (words >= 16) {
   74                         SUMADV; SUMADV; SUMADV; SUMADV;
   75                         SUMADV; SUMADV; SUMADV; SUMADV;
   76                         SUMADV; SUMADV; SUMADV; SUMADV;
   77                         SUMADV; SUMADV; SUMADV; SUMADV;
   78                         words -= 16;
   79                 }
   80                 while (words--)
   81                         SUMADV;
   82                 if (len == 0)
   83                         break;
   84                 mlen &= 1;
   85                 if (mlen) {
   86                         buf.b[0] = *w;
   87                         if (--len == 0) {
   88                                 buf.b[1] = 0;
   89                                 sum += buf.w;
   90                                 break;
   91                         }
   92                 }
   93                 m = m->m_next;
   94                 if (m == NULL)
   95                         break;
   96                 w = mtod(m, u_char *);
   97                 if (mlen) {
   98                         buf.b[1] = *w;
   99                         sum += buf.w;
  100                         w++;
  101                         if (--len == 0)
  102                                 break;
  103                 }
  104         }
  105 
  106         ipx->ipx_tc = oldtc;
  107 
  108         sum = (sum & 0xffff) + (sum >> 16);
  109         if (sum >= 0x10000)
  110                 sum++;
  111         if (sum)
  112                 sum = ~sum;
  113         return (sum);
  114 }

Cache object: 17b44a6a8875812b0dc88c65940daab2


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