1 /*-
2 * Copyright (c) 2001 Charles Mott <cm@linktel.net>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27 #include <sys/cdefs.h>
28 __FBSDID("$FreeBSD: stable/10/sys/netinet/libalias/alias_util.c 174348 2007-12-06 09:31:13Z des $");
29
30
31 /*
32 Alias_util.c contains general utilities used by other functions
33 in the packet aliasing module. At the moment, there are functions
34 for computing IP header and TCP packet checksums.
35
36 The checksum routines are based upon example code in a Unix networking
37 text written by Stevens (sorry, I can't remember the title -- but
38 at least this is a good author).
39
40 Initial Version: August, 1996 (cjm)
41
42 Version 1.7: January 9, 1997
43 Added differential checksum update function.
44 */
45
46 #ifdef _KERNEL
47 #include <sys/param.h>
48 #include <sys/proc.h>
49 #else
50 #include <sys/types.h>
51 #include <stdio.h>
52 #endif
53
54 #include <netinet/in_systm.h>
55 #include <netinet/in.h>
56 #include <netinet/ip.h>
57 #include <netinet/tcp.h>
58
59 #ifdef _KERNEL
60 #include <netinet/libalias/alias.h>
61 #include <netinet/libalias/alias_local.h>
62 #else
63 #include "alias.h"
64 #include "alias_local.h"
65 #endif
66
67 /*
68 * Note: the checksum routines assume that the actual checksum word has
69 * been zeroed out. If the checksum word is filled with the proper value,
70 * then these routines will give a result of zero (useful for testing
71 * purposes);
72 */
73 u_short
LibAliasInternetChecksum(struct libalias * la __unused,u_short * ptr,int nbytes)74 LibAliasInternetChecksum(struct libalias *la __unused, u_short * ptr,
75 int nbytes)
76 {
77 int sum, oddbyte;
78
79 LIBALIAS_LOCK(la);
80 sum = 0;
81 while (nbytes > 1) {
82 sum += *ptr++;
83 nbytes -= 2;
84 }
85 if (nbytes == 1) {
86 oddbyte = 0;
87 ((u_char *) & oddbyte)[0] = *(u_char *) ptr;
88 ((u_char *) & oddbyte)[1] = 0;
89 sum += oddbyte;
90 }
91 sum = (sum >> 16) + (sum & 0xffff);
92 sum += (sum >> 16);
93 LIBALIAS_UNLOCK(la);
94 return (~sum);
95 }
96
97 #ifndef _KERNEL
98 u_short
IpChecksum(struct ip * pip)99 IpChecksum(struct ip *pip)
100 {
101 return (LibAliasInternetChecksum(NULL, (u_short *) pip,
102 (pip->ip_hl << 2)));
103
104 }
105
106 u_short
TcpChecksum(struct ip * pip)107 TcpChecksum(struct ip *pip)
108 {
109 u_short *ptr;
110 struct tcphdr *tc;
111 int nhdr, ntcp, nbytes;
112 int sum, oddbyte;
113
114 nhdr = pip->ip_hl << 2;
115 ntcp = ntohs(pip->ip_len) - nhdr;
116
117 tc = (struct tcphdr *)ip_next(pip);
118 ptr = (u_short *) tc;
119
120 /* Add up TCP header and data */
121 nbytes = ntcp;
122 sum = 0;
123 while (nbytes > 1) {
124 sum += *ptr++;
125 nbytes -= 2;
126 }
127 if (nbytes == 1) {
128 oddbyte = 0;
129 ((u_char *) & oddbyte)[0] = *(u_char *) ptr;
130 ((u_char *) & oddbyte)[1] = 0;
131 sum += oddbyte;
132 }
133 /* "Pseudo-header" data */
134 ptr = (void *)&pip->ip_dst;
135 sum += *ptr++;
136 sum += *ptr;
137 ptr = (void *)&pip->ip_src;
138 sum += *ptr++;
139 sum += *ptr;
140 sum += htons((u_short) ntcp);
141 sum += htons((u_short) pip->ip_p);
142
143 /* Roll over carry bits */
144 sum = (sum >> 16) + (sum & 0xffff);
145 sum += (sum >> 16);
146
147 /* Return checksum */
148 return ((u_short) ~ sum);
149 }
150 #endif /* not _KERNEL */
151
152 void
DifferentialChecksum(u_short * cksum,void * newp,void * oldp,int n)153 DifferentialChecksum(u_short * cksum, void *newp, void *oldp, int n)
154 {
155 int i;
156 int accumulate;
157 u_short *new = newp;
158 u_short *old = oldp;
159
160 accumulate = *cksum;
161 for (i = 0; i < n; i++) {
162 accumulate -= *new++;
163 accumulate += *old++;
164 }
165
166 if (accumulate < 0) {
167 accumulate = -accumulate;
168 accumulate = (accumulate >> 16) + (accumulate & 0xffff);
169 accumulate += accumulate >> 16;
170 *cksum = (u_short) ~ accumulate;
171 } else {
172 accumulate = (accumulate >> 16) + (accumulate & 0xffff);
173 accumulate += accumulate >> 16;
174 *cksum = (u_short) accumulate;
175 }
176 }
177