sys/lib/libsa/ip_cksum.c

   1 /*      $NetBSD: ip_cksum.c,v 1.2 2006/01/25 13:46:09 christos Exp $    */
   2
   3 /*
   4  * Copyright (c) 1992 Regents of the University of California.
   5  * All rights reserved.
   6  *
   7  * This software was developed by the Computer Systems Engineering group
   8  * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
   9  * contributed to Berkeley.
  10  *
  11  * Redistribution and use in source and binary forms, with or without
  12  * modification, are permitted provided that the following conditions
  13  * are met:
  14  * 1. Redistributions of source code must retain the above copyright
  15  *    notice, this list of conditions and the following disclaimer.
  16  * 2. Redistributions in binary form must reproduce the above copyright
  17  *    notice, this list of conditions and the following disclaimer in the
  18  *    documentation and/or other materials provided with the distribution.
  19  * 3. All advertising materials mentioning features or use of this software
  20  *    must display the following acknowledgement:
  21  *      This product includes software developed by the University of
  22  *      California, Lawrence Berkeley Laboratory and its contributors.
  23  * 4. Neither the name of the University nor the names of its contributors
  24  *    may be used to endorse or promote products derived from this software
  25  *    without specific prior written permission.
  26  *
  27  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  28  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  29  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  30  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  31  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  32  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  33  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  34  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  35  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  36  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  37  * SUCH DAMAGE.
  38  *
  39  * @(#) Header: in_cksum.c,v 1.1 92/09/11 01:15:55 leres Exp  (LBL)
  40  */
  41
  42 #include <sys/types.h>
  43 #include <sys/socket.h>
  44
  45 #include <net/if.h>
  46 #include <net/if_ether.h>
  47
  48 #include <netinet/in.h>
  49 #include <netinet/in_systm.h>
  50 #include <netinet/ip.h>
  51 #include <netinet/ip_var.h>
  52 #include <netinet/udp.h>
  53 #include <netinet/udp_var.h>
  54
  55 #include <machine/endian.h>
  56
  57 #include "stand.h"
  58 #include "net.h"
  59
  60 /*
  61  * Checksum routine for Internet Protocol family headers.
  62  * This routine is very heavily used in the network
  63  * code and should be modified for each CPU to be as fast as possible.
  64  * In particular, it should not be this one.
  65  */
  66 int
  67 ip_cksum(const void *p, size_t llen)
  68 {
  69         int sum = 0, oddbyte = 0, v = 0, len = (int)llen;
  70         const u_char *cp = p;
  71
  72         /* we assume < 2^16 bytes being summed */
  73         while (len > 0) {
  74                 if (oddbyte) {
  75                         sum += v + *cp++;
  76                         len--;
  77                 }
  78                 if (((long)cp & 1) == 0) {
  79                         while ((len -= 2) >= 0) {
  80                                 sum += *(const u_short *)cp;
  81                                 cp += 2;
  82                         }
  83                 } else {
  84                         while ((len -= 2) >= 0) {
  85 #if BYTE_ORDER == BIG_ENDIAN
  86                                 sum += *cp++ << 8;
  87                                 sum += *cp++;
  88 #else
  89                                 sum += *cp++;
  90                                 sum += *cp++ << 8;
  91 #endif
  92                         }
  93                 }
  94                 if ((oddbyte = len & 1) != 0)
  95 #if BYTE_ORDER == BIG_ENDIAN
  96                         v = *cp << 8;
  97 #else
  98                         v = *cp;
  99 #endif
 100         }
 101         if (oddbyte)
 102                 sum += v;
 103         sum = (sum >> 16) + (sum & 0xffff); /* add in accumulated carries */
 104         sum += sum >> 16;               /* add potential last carry */
 105         return (0xffff & ~sum);
 106 }