1/* $NetBSD: ip_cksum.c,v 1.1 2006/01/24 17:07:19 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 */ 66int 67ip_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} 107