alias_util.c revision 145921
1285163Sdim/*- 2285163Sdim * Copyright (c) 2001 Charles Mott <cm@linktel.net> 3353358Sdim * All rights reserved. 4353358Sdim * 5353358Sdim * Redistribution and use in source and binary forms, with or without 6285163Sdim * modification, are permitted provided that the following conditions 7285163Sdim * are met: 8285163Sdim * 1. Redistributions of source code must retain the above copyright 9285163Sdim * notice, this list of conditions and the following disclaimer. 10341825Sdim * 2. Redistributions in binary form must reproduce the above copyright 11285163Sdim * notice, this list of conditions and the following disclaimer in the 12285163Sdim * documentation and/or other materials provided with the distribution. 13285163Sdim * 14285163Sdim * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15285163Sdim * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16285163Sdim * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17285163Sdim * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18296417Sdim * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19285163Sdim * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20285163Sdim * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21285163Sdim * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22321369Sdim * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23321369Sdim * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24321369Sdim * SUCH DAMAGE. 25321369Sdim */ 26321369Sdim 27285163Sdim#include <sys/cdefs.h> 28285163Sdim__FBSDID("$FreeBSD: head/sys/netinet/libalias/alias_util.c 145921 2005-05-05 19:27:32Z glebius $"); 29285163Sdim 30 31/* 32 Alias_util.c contains general utilities used by other functions 33 in the packet aliasing module. At the moment, there are functions 34 for computing IP header and TCP packet checksums. 35 36 The checksum routines are based upon example code in a Unix networking 37 text written by Stevens (sorry, I can't remember the title -- but 38 at least this is a good author). 39 40 Initial Version: August, 1996 (cjm) 41 42 Version 1.7: January 9, 1997 43 Added differential checksum update function. 44*/ 45 46/* 47Note: the checksum routines assume that the actual checksum word has 48been zeroed out. If the checksum word is filled with the proper value, 49then these routines will give a result of zero (useful for testing 50purposes); 51*/ 52 53#ifdef _KERNEL 54#include <sys/param.h> 55#else 56#include <sys/types.h> 57#include <stdio.h> 58#endif 59 60#include <netinet/in_systm.h> 61#include <netinet/in.h> 62#include <netinet/ip.h> 63#include <netinet/tcp.h> 64 65#ifdef _KERNEL 66#include <netinet/libalias/alias.h> 67#include <netinet/libalias/alias_local.h> 68#else 69#include "alias.h" 70#include "alias_local.h" 71#endif 72 73u_short 74LibAliasInternetChecksum(struct libalias *la, u_short * ptr, int nbytes) 75{ 76 int sum, oddbyte; 77 78 (void)la; 79 80 sum = 0; 81 while (nbytes > 1) { 82 sum += *ptr++; 83 nbytes -= 2; 84 } 85 if (nbytes == 1) { 86 oddbyte = 0; 87 ((u_char *) & oddbyte)[0] = *(u_char *) ptr; 88 ((u_char *) & oddbyte)[1] = 0; 89 sum += oddbyte; 90 } 91 sum = (sum >> 16) + (sum & 0xffff); 92 sum += (sum >> 16); 93 return (~sum); 94} 95 96u_short 97IpChecksum(struct ip *pip) 98{ 99 return (PacketAliasInternetChecksum((u_short *) pip, 100 (pip->ip_hl << 2))); 101 102} 103 104u_short 105TcpChecksum(struct ip *pip) 106{ 107 u_short *ptr; 108 struct tcphdr *tc; 109 int nhdr, ntcp, nbytes; 110 int sum, oddbyte; 111 112 nhdr = pip->ip_hl << 2; 113 ntcp = ntohs(pip->ip_len) - nhdr; 114 115 tc = (struct tcphdr *)ip_next(pip); 116 ptr = (u_short *) tc; 117 118/* Add up TCP header and data */ 119 nbytes = ntcp; 120 sum = 0; 121 while (nbytes > 1) { 122 sum += *ptr++; 123 nbytes -= 2; 124 } 125 if (nbytes == 1) { 126 oddbyte = 0; 127 ((u_char *) & oddbyte)[0] = *(u_char *) ptr; 128 ((u_char *) & oddbyte)[1] = 0; 129 sum += oddbyte; 130 } 131/* "Pseudo-header" data */ 132 ptr = (u_short *) & (pip->ip_dst); 133 sum += *ptr++; 134 sum += *ptr; 135 ptr = (u_short *) & (pip->ip_src); 136 sum += *ptr++; 137 sum += *ptr; 138 sum += htons((u_short) ntcp); 139 sum += htons((u_short) pip->ip_p); 140 141/* Roll over carry bits */ 142 sum = (sum >> 16) + (sum & 0xffff); 143 sum += (sum >> 16); 144 145/* Return checksum */ 146 return ((u_short) ~ sum); 147} 148 149 150void 151DifferentialChecksum(u_short * cksum, void *newp, void *oldp, int n) 152{ 153 int i; 154 int accumulate; 155 u_short *new = newp; 156 u_short *old = oldp; 157 158 accumulate = *cksum; 159 for (i = 0; i < n; i++) { 160 accumulate -= *new++; 161 accumulate += *old++; 162 } 163 164 if (accumulate < 0) { 165 accumulate = -accumulate; 166 accumulate = (accumulate >> 16) + (accumulate & 0xffff); 167 accumulate += accumulate >> 16; 168 *cksum = (u_short) ~ accumulate; 169 } else { 170 accumulate = (accumulate >> 16) + (accumulate & 0xffff); 171 accumulate += accumulate >> 16; 172 *cksum = (u_short) accumulate; 173 } 174} 175