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