vde-2/slirpvde/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 <config.h>
  38 #include <slirp.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  * XXX Since we will never span more than 1 mbuf, we can optimise this
  47  */
  48
  49 #define ADDCARRY(x)  (x > 65535 ? x -= 65535 : x)
  50 #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}
  51
  52 int cksum(struct mbuf *m, int len)
  53 {
  54         register u_int16_t *w;
  55         register int sum = 0;
  56         register int mlen = 0;
  57         int byte_swapped = 0;
  58
  59         union {
  60                 u_int8_t        c[2];
  61                 u_int16_t       s;
  62         } s_util;
  63         union {
  64                 u_int16_t s[2];
  65                 u_int32_t l;
  66         } l_util;
  67
  68         if (m->m_len == 0)
  69            goto cont;
  70         w = mtod(m, u_int16_t *);
  71
  72         mlen = m->m_len;
  73
  74         if (len < mlen)
  75            mlen = len;
  76         len -= mlen;
  77         /*
  78          * Force to even boundary.
  79          */
  80         if ((1 & (long) w) && (mlen > 0)) {
  81                 REDUCE;
  82                 sum <<= 8;
  83                 s_util.c[0] = *(u_int8_t *)w;
  84                 w = (u_int16_t *)((int8_t *)w + 1);
  85                 mlen--;
  86                 byte_swapped = 1;
  87         }
  88         /*
  89          * Unroll the loop to make overhead from
  90          * branches &c small.
  91          */
  92         while ((mlen -= 32) >= 0) {
  93                 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
  94                 sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
  95                 sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
  96                 sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
  97                 w += 16;
  98         }
  99         mlen += 32;
 100         while ((mlen -= 8) >= 0) {
 101                 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
 102                 w += 4;
 103         }
 104         mlen += 8;
 105         if (mlen == 0 && byte_swapped == 0)
 106            goto cont;
 107         REDUCE;
 108         while ((mlen -= 2) >= 0) {
 109                 sum += *w++;
 110         }
 111
 112         if (byte_swapped) {
 113                 REDUCE;
 114                 sum <<= 8;
 115                 byte_swapped = 0;
 116                 if (mlen == -1) {
 117                         s_util.c[1] = *(u_int8_t *)w;
 118                         sum += s_util.s;
 119                         mlen = 0;
 120                 } else
 121
 122                    mlen = -1;
 123         } else if (mlen == -1)
 124            s_util.c[0] = *(u_int8_t *)w;
 125
 126 cont:
 127 #ifdef DEBUG
 128         if (len) {
 129                 DEBUG_ERROR((dfd, "cksum: out of data\n"));
 130                 DEBUG_ERROR((dfd, " len = %d\n", len));
 131         }
 132 #endif
 133         if (mlen == -1) {
 134                 /* The last mbuf has odd # of bytes. Follow the
 135                  standard (the odd byte may be shifted left by 8 bits
 136                            or not as determined by endian-ness of the machine) */
 137                 s_util.c[1] = 0;
 138                 sum += s_util.s;
 139         }
 140         REDUCE;
 141         return (~sum & 0xffff);
 142 }