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b7080c8e 1/*
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2 * Copyright (c) 2000-2002 Apple Computer, Inc. All rights reserved.
3 *
4 * @APPLE_LICENSE_HEADER_START@
5 *
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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.
7ba0088d 11 *
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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
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14 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
15 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
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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.
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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
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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
7ba0088d 68been zeroed out. If the checksum word is filled with the proper value,
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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;
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96 ((u_char *) &oddbyte)[0] = *(u_char *) ptr;
97 ((u_char *) &oddbyte)[1] = 0;
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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;
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138 ((u_char *) &oddbyte)[0] = *(u_char *) ptr;
139 ((u_char *) &oddbyte)[1] = 0;
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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