slirp/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. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  *      @(#)in_cksum.c  8.1 (Berkeley) 6/10/93
  30  * in_cksum.c,v 1.2 1994/08/02 07:48:16 davidg Exp
  31  */
  32
  33 #include <slirp.h>
  34
  35 /*
  36  * Checksum routine for Internet Protocol family headers (Portable Version).
  37  *
  38  * This routine is very heavily used in the network
  39  * code and should be modified for each CPU to be as fast as possible.
  40  *
  41  * XXX Since we will never span more than 1 mbuf, we can optimise this
  42  */
  43
  44 #define ADDCARRY(x)  (x > 65535 ? x -= 65535 : x)
  45 #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1];        \
  46         (void)ADDCARRY(sum);}
  47
  48 int cksum(struct mbuf *m, int len)
  49 {
  50         register uint16_t *w;
  51         register int sum = 0;
  52         register int mlen = 0;
  53         int byte_swapped = 0;
  54
  55         union {
  56                 uint8_t  c[2];
  57                 uint16_t s;
  58         } s_util;
  59         union {
  60                 uint16_t s[2];
  61                 uint32_t l;
  62         } l_util;
  63
  64         if (m->m_len == 0)
  65            goto cont;
  66         w = mtod(m, uint16_t *);
  67
  68         mlen = m->m_len;
  69
  70         if (len < mlen)
  71            mlen = len;
  72 #ifdef DEBUG
  73         len -= mlen;
  74 #endif
  75         /*
  76          * Force to even boundary.
  77          */
  78         if ((1 & (long) w) && (mlen > 0)) {
  79                 REDUCE;
  80                 sum <<= 8;
  81                 s_util.c[0] = *(uint8_t *)w;
  82                 w = (uint16_t *)((int8_t *)w + 1);
  83                 mlen--;
  84                 byte_swapped = 1;
  85         }
  86         /*
  87          * Unroll the loop to make overhead from
  88          * branches &c small.
  89          */
  90         while ((mlen -= 32) >= 0) {
  91                 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
  92                 sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
  93                 sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
  94                 sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
  95                 w += 16;
  96         }
  97         mlen += 32;
  98         while ((mlen -= 8) >= 0) {
  99                 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
 100                 w += 4;
 101         }
 102         mlen += 8;
 103         if (mlen == 0 && byte_swapped == 0)
 104            goto cont;
 105         REDUCE;
 106         while ((mlen -= 2) >= 0) {
 107                 sum += *w++;
 108         }
 109
 110         if (byte_swapped) {
 111                 REDUCE;
 112                 sum <<= 8;
 113                 if (mlen == -1) {
 114                         s_util.c[1] = *(uint8_t *)w;
 115                         sum += s_util.s;
 116                         mlen = 0;
 117                 } else
 118
 119                    mlen = -1;
 120         } else if (mlen == -1)
 121            s_util.c[0] = *(uint8_t *)w;
 122
 123 cont:
 124 #ifdef DEBUG
 125         if (len) {
 126                 DEBUG_ERROR((dfd, "cksum: out of data\n"));
 127                 DEBUG_ERROR((dfd, " len = %d\n", len));
 128         }
 129 #endif
 130         if (mlen == -1) {
 131                 /* The last mbuf has odd # of bytes. Follow the
 132                  standard (the odd byte may be shifted left by 8 bits
 133                            or not as determined by endian-ness of the machine) */
 134                 s_util.c[1] = 0;
 135                 sum += s_util.s;
 136         }
 137         REDUCE;
 138         return (~sum & 0xffff);
 139 }