network_cmds-511.tar.gz
[apple/network_cmds.git] / alias / alias_util.c
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 /*
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
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
82 u_short
83 PacketAliasInternetChecksum(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
105 u_short
106 IpChecksum(struct ip *pip)
107 {
108 return( PacketAliasInternetChecksum((u_short *) pip,
109 (pip->ip_hl << 2)) );
110
111 }
112
113 u_short
114 TcpChecksum(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
162 void
163 DifferentialChecksum(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