"Fossies" - the Fresh Open Source Software Archive

Member "ospfd/in_cksum.c" (8 Jan 2007, 2863 Bytes) of package /linux/privat/old/openospfd-4.6.tgz:

    1 /*  $OpenBSD: in_cksum.c,v 1.6 2007/01/08 19:37:04 deraadt Exp $    */
    2 /*  $NetBSD: in_cksum.c,v 1.3 1995/04/22 13:53:48 cgd Exp $ */
    3 
    4 /*
    5  * Copyright (c) 1992 Regents of the University of California.
    6  * All rights reserved.
    7  *
    8  * This software was developed by the Computer Systems Engineering group
    9  * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
   10  * contributed to Berkeley.
   11  *
   12  * Redistribution and use in source and binary forms, with or without
   13  * modification, are permitted provided that the following conditions
   14  * are met:
   15  * 1. Redistributions of source code must retain the above copyright
   16  *    notice, this list of conditions and the following disclaimer.
   17  * 2. Redistributions in binary form must reproduce the above copyright
   18  *    notice, this list of conditions and the following disclaimer in the
   19  *    documentation and/or other materials provided with the distribution.
   20  * 3. Neither the name of the University nor the names of its contributors
   21  *    may be used to endorse or promote products derived from this software
   22  *    without specific prior written permission.
   23  *
   24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   34  * SUCH DAMAGE.
   35  *
   36  * @(#) Header: in_cksum.c,v 1.1 92/09/11 01:15:55 leres Exp  (LBL)
   37  */
   38 
   39 #include <sys/types.h>
   40 
   41 #include "ospfd.h"
   42 #include "log.h"
   43 
   44 /*
   45  * Checksum routine for Internet Protocol family headers.
   46  * This routine is very heavily used in the network
   47  * code and should be modified for each CPU to be as fast as possible.
   48  * In particular, it should not be this one.
   49  */
   50 u_int16_t
   51 in_cksum(void *p, size_t l)
   52 {
   53     unsigned int sum = 0;
   54     int len;
   55     u_char *cp = p;
   56 
   57     /* ensure that < 2^16 bytes being summed */
   58     if (l >= (1 << 16))
   59         fatalx("in_cksum: packet to big");
   60     len = (int)l;
   61 
   62     if (((long)cp & 1) == 0) {
   63         while (len > 1) {
   64             sum += htons(*(u_short *)cp);
   65             cp += 2;
   66             len -= 2;
   67         }
   68     } else {
   69         while (len > 1) {
   70             sum += *cp++ << 8;
   71             sum += *cp++;
   72             len -= 2;
   73         }
   74     }
   75     if (len == 1)
   76         sum += *cp << 8;
   77 
   78     sum = (sum >> 16) + (sum & 0xffff); /* add in accumulated carries */
   79     sum += sum >> 16;       /* add potential last carry */
   80     sum = ntohs(sum);
   81     return (0xffff & ~sum);
   82 }