Annotation of sys/lib/libsa/in_cksum.c, Revision 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: }
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