1/* 2 * Copyright (c) 2000-2002 Apple Computer, Inc. All rights reserved. 3 * 4 * @APPLE_LICENSE_HEADER_START@ 5 * 6 * The contents of this file constitute Original Code as defined in and 7 * are subject to the Apple Public Source License Version 1.1 (the 8 * "License"). You may not use this file except in compliance with the 9 * License. Please obtain a copy of the License at 10 * http://www.apple.com/publicsource and read it before using this file. 11 * 12 * This Original Code and all software distributed under the License are 13 * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER 14 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, 15 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, 16 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT. Please see the 17 * License for the specific language governing rights and limitations 18 * under the License. 19 * 20 * @APPLE_LICENSE_HEADER_END@ 21 */ 22/*- 23 * Copyright (c) 2001 Charles Mott <cmott@scientech.com> 24 * All rights reserved. 25 * 26 * Redistribution and use in source and binary forms, with or without 27 * modification, are permitted provided that the following conditions 28 * are met: 29 * 1. Redistributions of source code must retain the above copyright 30 * notice, this list of conditions and the following disclaimer. 31 * 2. Redistributions in binary form must reproduce the above copyright 32 * notice, this list of conditions and the following disclaimer in the 33 * documentation and/or other materials provided with the distribution. 34 * 35 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 36 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 37 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 38 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 39 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 40 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 41 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 42 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 43 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 44 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 45 * SUCH DAMAGE. 46 * 47 * Based upon: 48 * $FreeBSD: src/lib/libalias/alias_util.c,v 1.4.2.2 2001/06/04 14:59:06 brian Exp $ 49 */ 50 51/* 52 Alias_util.c contains general utilities used by other functions 53 in the packet aliasing module. At the moment, there are functions 54 for computing IP header and TCP packet checksums. 55 56 The checksum routines are based upon example code in a Unix networking 57 text written by Stevens (sorry, I can't remember the title -- but 58 at least this is a good author). 59 60 Initial Version: August, 1996 (cjm) 61 62 Version 1.7: January 9, 1997 63 Added differential checksum update function. 64*/ 65 66/* 67Note: the checksum routines assume that the actual checksum word has 68been zeroed out. If the checksum word is filled with the proper value, 69then these routines will give a result of zero (useful for testing 70purposes); 71*/ 72 73#include <sys/types.h> 74#include <netinet/in_systm.h> 75#include <netinet/in.h> 76#include <netinet/ip.h> 77#include <netinet/tcp.h> 78 79#include "alias.h" 80#include "alias_local.h" 81 82u_short 83PacketAliasInternetChecksum(u_short *ptr, int nbytes) 84{ 85 int sum, oddbyte; 86 87 sum = 0; 88 while (nbytes > 1) 89 { 90 sum += *ptr++; 91 nbytes -= 2; 92 } 93 if (nbytes == 1) 94 { 95 oddbyte = 0; 96 ((u_char *) &oddbyte)[0] = *(u_char *) ptr; 97 ((u_char *) &oddbyte)[1] = 0; 98 sum += oddbyte; 99 } 100 sum = (sum >> 16) + (sum & 0xffff); 101 sum += (sum >> 16); 102 return(~sum); 103} 104 105u_short 106IpChecksum(struct ip *pip) 107{ 108 return( PacketAliasInternetChecksum((u_short *) pip, 109 (pip->ip_hl << 2)) ); 110 111} 112 113u_short 114TcpChecksum(struct ip *pip) 115{ 116 u_short *ptr; 117 struct tcphdr *tc; 118 int nhdr, ntcp, nbytes; 119 int sum, oddbyte; 120 121 nhdr = pip->ip_hl << 2; 122 ntcp = ntohs(pip->ip_len) - nhdr; 123 124 tc = (struct tcphdr *) ((char *) pip + nhdr); 125 ptr = (u_short *) tc; 126 127/* Add up TCP header and data */ 128 nbytes = ntcp; 129 sum = 0; 130 while (nbytes > 1) 131 { 132 sum += *ptr++; 133 nbytes -= 2; 134 } 135 if (nbytes == 1) 136 { 137 oddbyte = 0; 138 ((u_char *) &oddbyte)[0] = *(u_char *) ptr; 139 ((u_char *) &oddbyte)[1] = 0; 140 sum += oddbyte; 141 } 142 143/* "Pseudo-header" data */ 144 ptr = (u_short *) &(pip->ip_dst); 145 sum += *ptr++; 146 sum += *ptr; 147 ptr = (u_short *) &(pip->ip_src); 148 sum += *ptr++; 149 sum += *ptr; 150 sum += htons((u_short) ntcp); 151 sum += htons((u_short) pip->ip_p); 152 153/* Roll over carry bits */ 154 sum = (sum >> 16) + (sum & 0xffff); 155 sum += (sum >> 16); 156 157/* Return checksum */ 158 return((u_short) ~sum); 159} 160 161 162void 163DifferentialChecksum(u_short *cksum, u_short *new, u_short *old, int n) 164{ 165 int i; 166 int accumulate; 167 168 accumulate = *cksum; 169 for (i=0; i<n; i++) 170 { 171 accumulate -= *new++; 172 accumulate += *old++; 173 } 174 175 if (accumulate < 0) 176 { 177 accumulate = -accumulate; 178 accumulate = (accumulate >> 16) + (accumulate & 0xffff); 179 accumulate += accumulate >> 16; 180 *cksum = (u_short) ~accumulate; 181 } 182 else 183 { 184 accumulate = (accumulate >> 16) + (accumulate & 0xffff); 185 accumulate += accumulate >> 16; 186 *cksum = (u_short) accumulate; 187 } 188} 189 190