1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 3 * 4 * Copyright (c) 2001 Charles Mott <cm@linktel.net> 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29 #include <sys/cdefs.h> 30 /* 31 Alias_util.c contains general utilities used by other functions 32 in the packet aliasing module. At the moment, there are functions 33 for computing IP header and TCP packet checksums. 34 35 The checksum routines are based upon example code in a Unix networking 36 text written by Stevens (sorry, I can't remember the title -- but 37 at least this is a good author). 38 39 Initial Version: August, 1996 (cjm) 40 41 Version 1.7: January 9, 1997 42 Added differential checksum update function. 43 */ 44 45 #ifdef _KERNEL 46 #include <sys/param.h> 47 #include <sys/proc.h> 48 #else 49 #include <sys/types.h> 50 #include <stdio.h> 51 #endif 52 53 #include <netinet/in_systm.h> 54 #include <netinet/in.h> 55 #include <netinet/ip.h> 56 #include <netinet/tcp.h> 57 58 #ifdef _KERNEL 59 #include <netinet/libalias/alias.h> 60 #include <netinet/libalias/alias_local.h> 61 #else 62 #include "alias.h" 63 #include "alias_local.h" 64 #endif 65 66 /* 67 * Note: the checksum routines assume that the actual checksum word has 68 * been zeroed out. If the checksum word is filled with the proper value, 69 * then these routines will give a result of zero (useful for testing 70 * purposes); 71 */ 72 u_short 73 LibAliasInternetChecksum(struct libalias *la __unused, u_short *ptr, 74 int nbytes) 75 { 76 int sum, oddbyte; 77 78 LIBALIAS_LOCK(la); 79 sum = 0; 80 while (nbytes > 1) { 81 sum += *ptr++; 82 nbytes -= 2; 83 } 84 if (nbytes == 1) { 85 oddbyte = 0; 86 ((u_char *)&oddbyte)[0] = *(u_char *)ptr; 87 ((u_char *)&oddbyte)[1] = 0; 88 sum += oddbyte; 89 } 90 sum = (sum >> 16) + (sum & 0xffff); 91 sum += (sum >> 16); 92 LIBALIAS_UNLOCK(la); 93 return (~sum); 94 } 95 96 #ifndef _KERNEL 97 u_short 98 IpChecksum(struct ip *pip) 99 { 100 return (LibAliasInternetChecksum(NULL, (u_short *)pip, 101 (pip->ip_hl << 2))); 102 103 } 104 105 u_short 106 TcpChecksum(struct ip *pip) 107 { 108 u_short *ptr; 109 struct tcphdr *tc; 110 int nhdr, ntcp, nbytes; 111 int sum, oddbyte; 112 113 nhdr = pip->ip_hl << 2; 114 ntcp = ntohs(pip->ip_len) - nhdr; 115 116 tc = (struct tcphdr *)ip_next(pip); 117 ptr = (u_short *)tc; 118 119 /* Add up TCP header and data */ 120 nbytes = ntcp; 121 sum = 0; 122 while (nbytes > 1) { 123 sum += *ptr++; 124 nbytes -= 2; 125 } 126 if (nbytes == 1) { 127 oddbyte = 0; 128 ((u_char *)&oddbyte)[0] = *(u_char *)ptr; 129 ((u_char *)&oddbyte)[1] = 0; 130 sum += oddbyte; 131 } 132 /* "Pseudo-header" data */ 133 ptr = (void *)&pip->ip_dst; 134 sum += *ptr++; 135 sum += *ptr; 136 ptr = (void *)&pip->ip_src; 137 sum += *ptr++; 138 sum += *ptr; 139 sum += htons((u_short)ntcp); 140 sum += htons((u_short)pip->ip_p); 141 142 /* Roll over carry bits */ 143 sum = (sum >> 16) + (sum & 0xffff); 144 sum += (sum >> 16); 145 146 /* Return checksum */ 147 return ((u_short)~sum); 148 } 149 #endif /* not _KERNEL */ 150 151 void 152 DifferentialChecksum(u_short *cksum, void *newp, void *oldp, int n) 153 { 154 int i; 155 int accumulate; 156 u_short *new = newp; 157 u_short *old = oldp; 158 159 accumulate = *cksum; 160 for (i = 0; i < n; i++) { 161 accumulate -= *new++; 162 accumulate += *old++; 163 } 164 165 if (accumulate < 0) { 166 accumulate = -accumulate; 167 accumulate = (accumulate >> 16) + (accumulate & 0xffff); 168 accumulate += accumulate >> 16; 169 *cksum = (u_short)~accumulate; 170 } else { 171 accumulate = (accumulate >> 16) + (accumulate & 0xffff); 172 accumulate += accumulate >> 16; 173 *cksum = (u_short)accumulate; 174 } 175 } 176