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
LibAliasInternetChecksum(struct libalias * la __unused,u_short * ptr,int nbytes)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
IpChecksum(struct ip * pip)98 IpChecksum(struct ip *pip)
99 {
100 return (LibAliasInternetChecksum(NULL, (u_short *)pip,
101 (pip->ip_hl << 2)));
102
103 }
104
105 u_short
TcpChecksum(struct ip * pip)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
DifferentialChecksum(u_short * cksum,void * newp,void * oldp,int n)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