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Annotation of sys/lib/libsa/in_cksum.c, Revision 1.1.1.1

1.1       nbrk        1: /*     $OpenBSD: in_cksum.c,v 1.3 2003/08/11 06:23:09 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. All advertising materials mentioning features or use of this software
                     21:  *    must display the following acknowledgement:
                     22:  *     This product includes software developed by the University of
                     23:  *     California, Lawrence Berkeley Laboratory and its contributors.
                     24:  * 4. Neither the name of the University nor the names of its contributors
                     25:  *    may be used to endorse or promote products derived from this software
                     26:  *    without specific prior written permission.
                     27:  *
                     28:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
                     29:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
                     30:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
                     31:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
                     32:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
                     33:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
                     34:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
                     35:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
                     36:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
                     37:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
                     38:  * SUCH DAMAGE.
                     39:  *
                     40:  * @(#) Header: in_cksum.c,v 1.1 92/09/11 01:15:55 leres Exp  (LBL)
                     41:  */
                     42:
                     43: #include <sys/types.h>
                     44: #include <sys/socket.h>
                     45: #include <net/if.h>
                     46: #include <netinet/in.h>
                     47:
                     48: #include <netinet/if_ether.h>
                     49: #include <netinet/in_systm.h>
                     50:
                     51: #include "stand.h"
                     52: #include "net.h"
                     53:
                     54: /*
                     55:  * Checksum routine for Internet Protocol family headers.
                     56:  * This routine is very heavily used in the network
                     57:  * code and should be modified for each CPU to be as fast as possible.
                     58:  * In particular, it should not be this one.
                     59:  */
                     60: int
                     61: in_cksum(void *p, int len)
                     62: {
                     63:        int sum = 0, oddbyte = 0, v = 0;
                     64:        u_char *cp = p;
                     65:
                     66:        /* we assume < 2^16 bytes being summed */
                     67:        while (len > 0) {
                     68:                if (oddbyte) {
                     69:                        sum += v + *cp++;
                     70:                        len--;
                     71:                }
                     72:                if (((long)cp & 1) == 0) {
                     73:                        while ((len -= 2) >= 0) {
                     74:                                sum += *(u_short *)cp;
                     75:                                cp += 2;
                     76:                        }
                     77:                } else {
                     78:                        while ((len -= 2) >= 0) {
                     79:                                sum += *cp++ << 8;
                     80:                                sum += *cp++;
                     81:                        }
                     82:                }
                     83:                if ((oddbyte = len & 1) != 0)
                     84:                        v = *cp << 8;
                     85:        }
                     86:        if (oddbyte)
                     87:                sum += v;
                     88:        sum = (sum >> 16) + (sum & 0xffff); /* add in accumulated carries */
                     89:        sum += sum >> 16;               /* add potential last carry */
                     90:        return (0xffff & ~sum);
                     91: }