sys/netproto/ipx/ipx_cksum.c

   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  * $DragonFly: src/sys/netproto/ipx/ipx_cksum.c,v 1.4 2005/02/15 18:11:59 joerg Exp $
  38  */
  39
  40 #include <sys/param.h>
  41 #include <sys/mbuf.h>
  42 #include <sys/libkern.h>
  43
  44 #include "ipx.h"
  45 #include "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_short *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 = &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] = *(u_char*)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_short*);
  97                 if (mlen) {
  98                         buf.b[1] = *(u_char*)w;
  99                         sum += buf.w;
 100                         w = (uint16_t *)((uint8_t *)w + 1);
 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 }