summaryrefslogtreecommitdiff
path: root/net/netfilter/xt_helper.c
blob: 047d0046b28cde8bf19c434e5735f58ff95c45ad (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
/* iptables module to match on related connections */
/*
 * (C) 2001 Martin Josefsson <gandalf@wlug.westbo.se>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/netfilter.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_helper.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Martin Josefsson <gandalf@netfilter.org>");
MODULE_DESCRIPTION("iptables helper match module");
MODULE_ALIAS("ipt_helper");
MODULE_ALIAS("ip6t_helper");

#if 0
#define DEBUGP printk
#else
#define DEBUGP(format, args...)
#endif

static bool
match(const struct sk_buff *skb,
      const struct net_device *in,
      const struct net_device *out,
      const struct xt_match *match,
      const void *matchinfo,
      int offset,
      unsigned int protoff,
      bool *hotdrop)
{
	const struct xt_helper_info *info = matchinfo;
	const struct nf_conn *ct;
	const struct nf_conn_help *master_help;
	enum ip_conntrack_info ctinfo;
	bool ret = info->invert;

	ct = nf_ct_get(skb, &ctinfo);
	if (!ct) {
		DEBUGP("xt_helper: Eek! invalid conntrack?\n");
		return ret;
	}

	if (!ct->master) {
		DEBUGP("xt_helper: conntrack %p has no master\n", ct);
		return ret;
	}

	read_lock_bh(&nf_conntrack_lock);
	master_help = nfct_help(ct->master);
	if (!master_help || !master_help->helper) {
		DEBUGP("xt_helper: master ct %p has no helper\n",
			exp->expectant);
		goto out_unlock;
	}

	DEBUGP("master's name = %s , info->name = %s\n",
		ct->master->helper->name, info->name);

	if (info->name[0] == '\0')
		ret = !ret;
	else
		ret ^= !strncmp(master_help->helper->name, info->name,
				strlen(master_help->helper->name));
out_unlock:
	read_unlock_bh(&nf_conntrack_lock);
	return ret;
}

static bool check(const char *tablename,
		  const void *inf,
		  const struct xt_match *match,
		  void *matchinfo,
		  unsigned int hook_mask)
{
	struct xt_helper_info *info = matchinfo;

	if (nf_ct_l3proto_try_module_get(match->family) < 0) {
		printk(KERN_WARNING "can't load conntrack support for "
				    "proto=%d\n", match->family);
		return false;
	}
	info->name[29] = '\0';
	return true;
}

static void
destroy(const struct xt_match *match, void *matchinfo)
{
	nf_ct_l3proto_module_put(match->family);
}

static struct xt_match xt_helper_match[] = {
	{
		.name		= "helper",
		.family		= AF_INET,
		.checkentry	= check,
		.match		= match,
		.destroy	= destroy,
		.matchsize	= sizeof(struct xt_helper_info),
		.me		= THIS_MODULE,
	},
	{
		.name		= "helper",
		.family		= AF_INET6,
		.checkentry	= check,
		.match		= match,
		.destroy	= destroy,
		.matchsize	= sizeof(struct xt_helper_info),
		.me		= THIS_MODULE,
	},
};

static int __init xt_helper_init(void)
{
	return xt_register_matches(xt_helper_match,
				   ARRAY_SIZE(xt_helper_match));
}

static void __exit xt_helper_fini(void)
{
	xt_unregister_matches(xt_helper_match, ARRAY_SIZE(xt_helper_match));
}

module_init(xt_helper_init);
module_exit(xt_helper_fini);