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. 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  * in_cksum.c,v 1.2 1994/08/02 07:48:16 davidg Exp
  35  */
  36
  37 #include <slirp.h>
  38
  39 /*
  40  * Checksum routine for Internet Protocol family headers (Portable Version).
  41  *
  42  * This routine is very heavily used in the network
  43  * code and should be modified for each CPU to be as fast as possible.
  44  *
  45  * XXX Since we will never span more than 1 mbuf, we can optimise this
  46  */
  47
  48 #define ADDCARRY(x)  (x > 65535 ? x -= 65535 : x)
  49 #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}
  50
  51 int cksum(struct mbuf *m, int len)
  52 {
  53         register u_int16_t *w;
  54         register int sum = 0;
  55         register int mlen = 0;
  56         int byte_swapped = 0;
  57
  58         union {
  59                 u_int8_t        c[2];
  60                 u_int16_t       s;
  61         } s_util;
  62         union {
  63                 u_int16_t s[2];
  64                 u_int32_t l;
  65         } l_util;
  66
  67         if (m->m_len == 0)
  68            goto cont;
  69         w = mtod(m, u_int16_t *);
  70
  71         mlen = m->m_len;
  72
  73         if (len < mlen)
  74            mlen = len;
  75         len -= mlen;
  76         /*
  77          * Force to even boundary.
  78          */
  79         if ((1 & (long) w) && (mlen > 0)) {
  80                 REDUCE;
  81                 sum <<= 8;
  82                 s_util.c[0] = *(u_int8_t *)w;
  83                 w = (u_int16_t *)((int8_t *)w + 1);
  84                 mlen--;
  85                 byte_swapped = 1;
  86         }
  87         /*
  88          * Unroll the loop to make overhead from
  89          * branches &c small.
  90          */
  91         while ((mlen -= 32) >= 0) {
  92                 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
  93                 sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
  94                 sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
  95                 sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
  96                 w += 16;
  97         }
  98         mlen += 32;
  99         while ((mlen -= 8) >= 0) {
 100                 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
 101                 w += 4;
 102         }
 103         mlen += 8;
 104         if (mlen == 0 && byte_swapped == 0)
 105            goto cont;
 106         REDUCE;
 107         while ((mlen -= 2) >= 0) {
 108                 sum += *w++;
 109         }
 110
 111         if (byte_swapped) {
 112                 REDUCE;
 113                 sum <<= 8;
 114                 byte_swapped = 0;
 115                 if (mlen == -1) {
 116                         s_util.c[1] = *(u_int8_t *)w;
 117                         sum += s_util.s;
 118                         mlen = 0;
 119                 } else
 120
 121                    mlen = -1;
 122         } else if (mlen == -1)
 123            s_util.c[0] = *(u_int8_t *)w;
 124
 125 cont:
 126 #ifdef DEBUG
 127         if (len) {
 128                 DEBUG_ERROR((dfd, "cksum: out of data\n"));
 129                 DEBUG_ERROR((dfd, " len = %d\n", len));
 130         }
 131 #endif
 132         if (mlen == -1) {
 133                 /* The last mbuf has odd # of bytes. Follow the
 134                  standard (the odd byte may be shifted left by 8 bits
 135                            or not as determined by endian-ness of the machine) */
 136                 s_util.c[1] = 0;
 137                 sum += s_util.s;
 138         }
 139         REDUCE;
 140         return (~sum & 0xffff);
 141 }