nf_conntrack_helper.c revision ceceae1b1555a9afcb8dacf90df5fa1f20fd5466 
1/* Helper handling for netfilter. */
2
3/* (C) 1999-2001 Paul `Rusty' Russell
4 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
5 * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 */
11
12#include <linux/types.h>
13#include <linux/netfilter.h>
14#include <linux/module.h>
15#include <linux/skbuff.h>
16#include <linux/vmalloc.h>
17#include <linux/stddef.h>
18#include <linux/slab.h>
19#include <linux/random.h>
20#include <linux/err.h>
21#include <linux/kernel.h>
22#include <linux/netdevice.h>
23
24#include <net/netfilter/nf_conntrack.h>
25#include <net/netfilter/nf_conntrack_l3proto.h>
26#include <net/netfilter/nf_conntrack_l4proto.h>
27#include <net/netfilter/nf_conntrack_helper.h>
28#include <net/netfilter/nf_conntrack_core.h>
29#include <net/netfilter/nf_conntrack_extend.h>
30
31static __read_mostly LIST_HEAD(helpers);
32
33struct nf_conntrack_helper *
34__nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
35{
36	struct nf_conntrack_helper *h;
37
38	list_for_each_entry(h, &helpers, list) {
39		if (nf_ct_tuple_mask_cmp(tuple, &h->tuple, &h->mask))
40			return h;
41	}
42	return NULL;
43}
44
45struct nf_conntrack_helper *
46nf_ct_helper_find_get( const struct nf_conntrack_tuple *tuple)
47{
48	struct nf_conntrack_helper *helper;
49
50	/* need nf_conntrack_lock to assure that helper exists until
51	 * try_module_get() is called */
52	read_lock_bh(&nf_conntrack_lock);
53
54	helper = __nf_ct_helper_find(tuple);
55	if (helper) {
56		/* need to increase module usage count to assure helper will
57		 * not go away while the caller is e.g. busy putting a
58		 * conntrack in the hash that uses the helper */
59		if (!try_module_get(helper->me))
60			helper = NULL;
61	}
62
63	read_unlock_bh(&nf_conntrack_lock);
64
65	return helper;
66}
67EXPORT_SYMBOL_GPL(nf_ct_helper_find_get);
68
69void nf_ct_helper_put(struct nf_conntrack_helper *helper)
70{
71	module_put(helper->me);
72}
73EXPORT_SYMBOL_GPL(nf_ct_helper_put);
74
75struct nf_conntrack_helper *
76__nf_conntrack_helper_find_byname(const char *name)
77{
78	struct nf_conntrack_helper *h;
79
80	list_for_each_entry(h, &helpers, list) {
81		if (!strcmp(h->name, name))
82			return h;
83	}
84
85	return NULL;
86}
87EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find_byname);
88
89static inline int unhelp(struct nf_conntrack_tuple_hash *i,
90			 const struct nf_conntrack_helper *me)
91{
92	struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
93	struct nf_conn_help *help = nfct_help(ct);
94
95	if (help && help->helper == me) {
96		nf_conntrack_event(IPCT_HELPER, ct);
97		rcu_assign_pointer(help->helper, NULL);
98	}
99	return 0;
100}
101
102int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
103{
104	BUG_ON(me->timeout == 0);
105
106	write_lock_bh(&nf_conntrack_lock);
107	list_add(&me->list, &helpers);
108	write_unlock_bh(&nf_conntrack_lock);
109
110	return 0;
111}
112EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
113
114void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
115{
116	unsigned int i;
117	struct nf_conntrack_tuple_hash *h;
118	struct nf_conntrack_expect *exp, *tmp;
119
120	/* Need write lock here, to delete helper. */
121	write_lock_bh(&nf_conntrack_lock);
122	list_del(&me->list);
123
124	/* Get rid of expectations */
125	list_for_each_entry_safe(exp, tmp, &nf_conntrack_expect_list, list) {
126		struct nf_conn_help *help = nfct_help(exp->master);
127		if ((help->helper == me || exp->helper == me) &&
128		    del_timer(&exp->timeout)) {
129			nf_ct_unlink_expect(exp);
130			nf_conntrack_expect_put(exp);
131		}
132	}
133
134	/* Get rid of expecteds, set helpers to NULL. */
135	list_for_each_entry(h, &unconfirmed, list)
136		unhelp(h, me);
137	for (i = 0; i < nf_conntrack_htable_size; i++) {
138		list_for_each_entry(h, &nf_conntrack_hash[i], list)
139			unhelp(h, me);
140	}
141	write_unlock_bh(&nf_conntrack_lock);
142
143	/* Someone could be still looking at the helper in a bh. */
144	synchronize_net();
145}
146EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
147
148struct nf_ct_ext_type helper_extend = {
149	.len	= sizeof(struct nf_conn_help),
150	.align	= __alignof__(struct nf_conn_help),
151	.id	= NF_CT_EXT_HELPER,
152};
153
154int nf_conntrack_helper_init()
155{
156	return nf_ct_extend_register(&helper_extend);
157}
158
159void nf_conntrack_helper_fini()
160{
161	nf_ct_extend_unregister(&helper_extend);
162}
163