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 "qemu/osdep.h"
  34 #include <slirp.h>
  35
  36 /*
  37  * Checksum routine for Internet Protocol family headers (Portable Version).
  38  *
  39  * This routine is very heavily used in the network
  40  * code and should be modified for each CPU to be as fast as possible.
  41  *
  42  * XXX Since we will never span more than 1 mbuf, we can optimise this
  43  */
  44
  45 #define ADDCARRY(x)  (x > 65535 ? x -= 65535 : x)
  46 #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1];        \
  47         (void)ADDCARRY(sum);}
  48
  49 int cksum(struct mbuf *m, int len)
  50 {
  51         register uint16_t *w;
  52         register int sum = 0;
  53         register int mlen = 0;
  54         int byte_swapped = 0;
  55
  56         union {
  57                 uint8_t  c[2];
  58                 uint16_t s;
  59         } s_util;
  60         union {
  61                 uint16_t s[2];
  62                 uint32_t l;
  63         } l_util;
  64
  65         if (m->m_len == 0)
  66            goto cont;
  67         w = mtod(m, uint16_t *);
  68
  69         mlen = m->m_len;
  70
  71         if (len < mlen)
  72            mlen = len;
  73 #ifdef DEBUG
  74         len -= mlen;
  75 #endif
  76         /*
  77          * Force to even boundary.
  78          */
  79         if ((1 & (uintptr_t)w) && (mlen > 0)) {
  80                 REDUCE;
  81                 sum <<= 8;
  82                 s_util.c[0] = *(uint8_t *)w;
  83                 w = (uint16_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                 if (mlen == -1) {
 115                         s_util.c[1] = *(uint8_t *)w;
 116                         sum += s_util.s;
 117                         mlen = 0;
 118                 } else
 119
 120                    mlen = -1;
 121         } else if (mlen == -1)
 122            s_util.c[0] = *(uint8_t *)w;
 123
 124 cont:
 125 #ifdef DEBUG
 126         if (len) {
 127                 DEBUG_ERROR((dfd, "cksum: out of data\n"));
 128                 DEBUG_ERROR((dfd, " len = %d\n", len));
 129         }
 130 #endif
 131         if (mlen == -1) {
 132                 /* The last mbuf has odd # of bytes. Follow the
 133                  standard (the odd byte may be shifted left by 8 bits
 134                            or not as determined by endian-ness of the machine) */
 135                 s_util.c[1] = 0;
 136                 sum += s_util.s;
 137         }
 138         REDUCE;
 139         return (~sum & 0xffff);
 140 }