1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2005 Paolo Pisati <[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 * Alias_dummy is just an empty skeleton used to demostrate how to write
34 * a module for libalias, that will run unalterated in userland or in
35 * kernel land.
36 */
37
38 #ifdef _KERNEL
39 #include <sys/param.h>
40 #include <sys/kernel.h>
41 #include <sys/module.h>
42 #else
43 #include <errno.h>
44 #include <sys/types.h>
45 #include <stdio.h>
46 #endif
47
48 #include <netinet/in_systm.h>
49 #include <netinet/in.h>
50 #include <netinet/ip.h>
51 #include <netinet/udp.h>
52
53 #ifdef _KERNEL
54 #include <netinet/libalias/alias_local.h>
55 #include <netinet/libalias/alias_mod.h>
56 #else
57 #include "alias_local.h"
58 #include "alias_mod.h"
59 #endif
60
61 static void
62 AliasHandleDummy(struct libalias *la, struct ip *ip, struct alias_data *ah);
63
64 static int
fingerprint(struct libalias * la,struct alias_data * ah)65 fingerprint(struct libalias *la, struct alias_data *ah)
66 {
67
68 /*
69 * Check here all the data that will be used later, if any field
70 * is empy/NULL, return a -1 value.
71 */
72 if (ah->dport == NULL || ah->sport == NULL || ah->lnk == NULL ||
73 ah->maxpktsize == 0)
74 return (-1);
75 /*
76 * Fingerprint the incoming packet, if it matches any conditions
77 * return an OK value.
78 */
79 if (ntohs(*ah->dport) == 123
80 || ntohs(*ah->sport) == 456)
81 return (0); /* I know how to handle it. */
82 return (-1); /* I don't recognize this packet. */
83 }
84
85 /*
86 * Wrap in this general purpose function, the real function used to alias the
87 * packets.
88 */
89
90 static int
protohandler(struct libalias * la,struct ip * pip,struct alias_data * ah)91 protohandler(struct libalias *la, struct ip *pip, struct alias_data *ah)
92 {
93
94 AliasHandleDummy(la, pip, ah);
95 return (0);
96 }
97
98 /*
99 * NOTA BENE: the next variable MUST NOT be renamed in any case if you want
100 * your module to work in userland, cause it's used to find and use all
101 * the protocol handlers present in every module.
102 * So WATCH OUT, your module needs this variables and it needs it with
103 * ITS EXACT NAME: handlers.
104 */
105
106 struct proto_handler handlers [] = {
107 {
108 .pri = 666,
109 .dir = IN|OUT,
110 .proto = UDP|TCP,
111 .fingerprint = &fingerprint,
112 .protohandler = &protohandler
113 },
114 { EOH }
115 };
116
117 static int
mod_handler(module_t mod,int type,void * data)118 mod_handler(module_t mod, int type, void *data)
119 {
120 int error;
121
122 switch (type) {
123 case MOD_LOAD:
124 error = 0;
125 LibAliasAttachHandlers(handlers);
126 break;
127 case MOD_UNLOAD:
128 error = 0;
129 LibAliasDetachHandlers(handlers);
130 break;
131 default:
132 error = EINVAL;
133 }
134 return (error);
135 }
136
137 #ifdef _KERNEL
138 static
139 #endif
140 moduledata_t alias_mod = {
141 "alias_dummy", mod_handler, NULL
142 };
143
144 #ifdef _KERNEL
145 DECLARE_MODULE(alias_dummy, alias_mod, SI_SUB_DRIVERS, SI_ORDER_SECOND);
146 MODULE_VERSION(alias_dummy, 1);
147 MODULE_DEPEND(alias_dummy, libalias, 1, 1, 1);
148 #endif
149
150 static void
AliasHandleDummy(struct libalias * la,struct ip * ip,struct alias_data * ah)151 AliasHandleDummy(struct libalias *la, struct ip *ip, struct alias_data *ah)
152 {
153 ; /* Dummy. */
154 }
155