reactos/lib/drivers/oskittcp/oskittcp/in_cksum.c

   1 /*
   2  * Copyright (c) 1988, 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  *      @(#)in_cksum.c  8.1 (Berkeley) 6/10/93
  34  */
  35
  36 #include <sys/param.h>
  37 #include <sys/mbuf.h>
  38 #include <sys/systm.h>
  39
  40 /*
  41  * Checksum routine for Internet Protocol family headers (Portable Version).
  42  *
  43  * This routine is very heavily used in the network
  44  * code and should be modified for each CPU to be as fast as possible.
  45  */
  46
  47 #define ADDCARRY(x)  (x > 65535 ? x -= 65535 : x)
  48 #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}
  49
  50 int
  51 in_cksum(m, len)
  52         register struct mbuf *m;
  53         register int len;
  54 {
  55         register u_short *w;
  56         register int sum = 0;
  57         register int mlen = 0;
  58         int byte_swapped = 0;
  59
  60         union {
  61                 char    c[2];
  62                 u_short s;
  63         } s_util;
  64         union {
  65                 u_short s[2];
  66                 long    l;
  67         } l_util;
  68
  69         for (;m && len; m = m->m_next) {
  70                 if (m->m_len == 0)
  71                         continue;
  72                 w = mtod(m, u_short *);
  73                 if (mlen == -1) {
  74                         /*
  75                          * The first byte of this mbuf is the continuation
  76                          * of a word spanning between this mbuf and the
  77                          * last mbuf.
  78                          *
  79                          * s_util.c[0] is already saved when scanning previous
  80                          * mbuf.
  81                          */
  82                         s_util.c[1] = *(char *)w;
  83                         sum += s_util.s;
  84                         w = (u_short *)((char *)w + 1);
  85                         mlen = m->m_len - 1;
  86                         len--;
  87                 } else
  88                         mlen = m->m_len;
  89                 if (len < mlen)
  90                         mlen = len;
  91                 len -= mlen;
  92                 /*
  93                  * Force to even boundary.
  94                  */
  95                 if ((1 & (int) w) && (mlen > 0)) {
  96                         REDUCE;
  97                         sum <<= 8;
  98                         s_util.c[0] = *(u_char *)w;
  99                         w = (u_short *)((char *)w + 1);
 100                         mlen--;
 101                         byte_swapped = 1;
 102                 }
 103                 /*
 104                  * Unroll the loop to make overhead from
 105                  * branches &c small.
 106                  */
 107                 while ((mlen -= 32) >= 0) {
 108                         sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
 109                         sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
 110                         sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
 111                         sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
 112                         w += 16;
 113                 }
 114                 mlen += 32;
 115                 while ((mlen -= 8) >= 0) {
 116                         sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
 117                         w += 4;
 118                 }
 119                 mlen += 8;
 120                 if (mlen == 0 && byte_swapped == 0)
 121                         continue;
 122                 REDUCE;
 123                 while ((mlen -= 2) >= 0) {
 124                         sum += *w++;
 125                 }
 126                 if (byte_swapped) {
 127                         REDUCE;
 128                         sum <<= 8;
 129                         byte_swapped = 0;
 130                         if (mlen == -1) {
 131                                 s_util.c[1] = *(char *)w;
 132                                 sum += s_util.s;
 133                                 mlen = 0;
 134                         } else
 135                                 mlen = -1;
 136                 } else if (mlen == -1)
 137                         s_util.c[0] = *(char *)w;
 138         }
 139         if (len) {
 140             panic("cksum: out of data: need %d bytes\n", len);
 141         }
 142         if (mlen == -1) {
 143                 /* The last mbuf has odd # of bytes. Follow the
 144                    standard (the odd byte may be shifted left by 8 bits
 145                    or not as determined by endian-ness of the machine) */
 146                 s_util.c[1] = 0;
 147                 sum += s_util.s;
 148         }
 149         REDUCE;
 150         return (~sum & 0xffff);
 151 }