tests/in_cksum.c

   1 /*
   2  * Copyright (c) 2000-2018 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23
  24 /*
  25  * Copyright (c) 1988, 1992, 1993
  26  *      The Regents of the University of California.  All rights reserved.
  27  *
  28  *      @(#)in_cksum.c  8.1 (Berkeley) 6/10/93
  29  */
  30
  31 #include <sys/param.h>
  32 #include "in_cksum.h"
  33
  34 typedef union {
  35         char        c[2];
  36         u_short     s;
  37 } short_union_t;
  38
  39 typedef union {
  40         u_short     s[2];
  41         long        l;
  42 } long_union_t;
  43
  44 static __inline__ void
  45 reduce(int * sum)
  46 {
  47         long_union_t l_util;
  48
  49         l_util.l = *sum;
  50         *sum = l_util.s[0] + l_util.s[1];
  51         if (*sum > 65535) {
  52                 *sum -= 65535;
  53         }
  54         return;
  55 }
  56
  57
  58 #include <stdio.h>
  59
  60 unsigned short
  61 in_cksum(void * pkt, int len)
  62 {
  63         u_short * w;
  64         int sum = 0;
  65
  66         w = (u_short *)pkt;
  67         while ((len -= 32) >= 0) {
  68                 sum += w[0]; sum += w[1];
  69                 sum += w[2]; sum += w[3];
  70                 sum += w[4]; sum += w[5];
  71                 sum += w[6]; sum += w[7];
  72                 sum += w[8]; sum += w[9];
  73                 sum += w[10]; sum += w[11];
  74                 sum += w[12]; sum += w[13];
  75                 sum += w[14]; sum += w[15];
  76                 w += 16;
  77         }
  78         len += 32;
  79         while ((len -= 8) >= 0) {
  80                 sum += w[0]; sum += w[1];
  81                 sum += w[2]; sum += w[3];
  82                 w += 4;
  83         }
  84         len += 8;
  85         if (len) {
  86                 reduce(&sum);
  87                 while ((len -= 2) >= 0) {
  88                         sum += *w++;
  89                 }
  90         }
  91         if (len == -1) { /* odd-length packet */
  92                 short_union_t s_util;
  93
  94                 s_util.s = 0;
  95                 s_util.c[0] = *((char *)w);
  96                 s_util.c[1] = 0;
  97                 sum += s_util.s;
  98         }
  99         reduce(&sum);
 100         return ~sum & 0xffff;
 101 }