1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2001 Charles Mott <[email protected]>
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 __FBSDID("$FreeBSD$");
31
32
33 /*
34 Alias_util.c contains general utilities used by other functions
35 in the packet aliasing module. At the moment, there are functions
36 for computing IP header and TCP packet checksums.
37
38 The checksum routines are based upon example code in a Unix networking
39 text written by Stevens (sorry, I can't remember the title -- but
40 at least this is a good author).
41
42 Initial Version: August, 1996 (cjm)
43
44 Version 1.7: January 9, 1997
45 Added differential checksum update function.
46 */
47
48 #ifdef _KERNEL
49 #include <sys/param.h>
50 #include <sys/proc.h>
51 #else
52 #include <sys/types.h>
53 #include <stdio.h>
54 #endif
55
56 #include <netinet/in_systm.h>
57 #include <netinet/in.h>
58 #include <netinet/ip.h>
59 #include <netinet/tcp.h>
60
61 #ifdef _KERNEL
62 #include <netinet/libalias/alias.h>
63 #include <netinet/libalias/alias_local.h>
64 #else
65 #include "alias.h"
66 #include "alias_local.h"
67 #endif
68
69 /*
70 * Note: the checksum routines assume that the actual checksum word has
71 * been zeroed out. If the checksum word is filled with the proper value,
72 * then these routines will give a result of zero (useful for testing
73 * purposes);
74 */
75 u_short
LibAliasInternetChecksum(struct libalias * la __unused,u_short * ptr,int nbytes)76 LibAliasInternetChecksum(struct libalias *la __unused, u_short * ptr,
77 int nbytes)
78 {
79 int sum, oddbyte;
80
81 LIBALIAS_LOCK(la);
82 sum = 0;
83 while (nbytes > 1) {
84 sum += *ptr++;
85 nbytes -= 2;
86 }
87 if (nbytes == 1) {
88 oddbyte = 0;
89 ((u_char *) & oddbyte)[0] = *(u_char *) ptr;
90 ((u_char *) & oddbyte)[1] = 0;
91 sum += oddbyte;
92 }
93 sum = (sum >> 16) + (sum & 0xffff);
94 sum += (sum >> 16);
95 LIBALIAS_UNLOCK(la);
96 return (~sum);
97 }
98
99 #ifndef _KERNEL
100 u_short
IpChecksum(struct ip * pip)101 IpChecksum(struct ip *pip)
102 {
103 return (LibAliasInternetChecksum(NULL, (u_short *) pip,
104 (pip->ip_hl << 2)));
105
106 }
107
108 u_short
TcpChecksum(struct ip * pip)109 TcpChecksum(struct ip *pip)
110 {
111 u_short *ptr;
112 struct tcphdr *tc;
113 int nhdr, ntcp, nbytes;
114 int sum, oddbyte;
115
116 nhdr = pip->ip_hl << 2;
117 ntcp = ntohs(pip->ip_len) - nhdr;
118
119 tc = (struct tcphdr *)ip_next(pip);
120 ptr = (u_short *) tc;
121
122 /* Add up TCP header and data */
123 nbytes = ntcp;
124 sum = 0;
125 while (nbytes > 1) {
126 sum += *ptr++;
127 nbytes -= 2;
128 }
129 if (nbytes == 1) {
130 oddbyte = 0;
131 ((u_char *) & oddbyte)[0] = *(u_char *) ptr;
132 ((u_char *) & oddbyte)[1] = 0;
133 sum += oddbyte;
134 }
135 /* "Pseudo-header" data */
136 ptr = (void *)&pip->ip_dst;
137 sum += *ptr++;
138 sum += *ptr;
139 ptr = (void *)&pip->ip_src;
140 sum += *ptr++;
141 sum += *ptr;
142 sum += htons((u_short) ntcp);
143 sum += htons((u_short) pip->ip_p);
144
145 /* Roll over carry bits */
146 sum = (sum >> 16) + (sum & 0xffff);
147 sum += (sum >> 16);
148
149 /* Return checksum */
150 return ((u_short) ~ sum);
151 }
152 #endif /* not _KERNEL */
153
154 void
DifferentialChecksum(u_short * cksum,void * newp,void * oldp,int n)155 DifferentialChecksum(u_short * cksum, void *newp, void *oldp, int n)
156 {
157 int i;
158 int accumulate;
159 u_short *new = newp;
160 u_short *old = oldp;
161
162 accumulate = *cksum;
163 for (i = 0; i < n; i++) {
164 accumulate -= *new++;
165 accumulate += *old++;
166 }
167
168 if (accumulate < 0) {
169 accumulate = -accumulate;
170 accumulate = (accumulate >> 16) + (accumulate & 0xffff);
171 accumulate += accumulate >> 16;
172 *cksum = (u_short) ~ accumulate;
173 } else {
174 accumulate = (accumulate >> 16) + (accumulate & 0xffff);
175 accumulate += accumulate >> 16;
176 *cksum = (u_short) accumulate;
177 }
178 }
179