nf_conntrack_helper.c revision e2b7606cdb602a4f69c02cfc8bebe9c63b595e24 
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#define ASSERT_READ_LOCK(x)
25#define ASSERT_WRITE_LOCK(x)
26
27#include <net/netfilter/nf_conntrack.h>
28#include <net/netfilter/nf_conntrack_l3proto.h>
29#include <net/netfilter/nf_conntrack_protocol.h>
30#include <net/netfilter/nf_conntrack_helper.h>
31#include <net/netfilter/nf_conntrack_core.h>
32
33static __read_mostly LIST_HEAD(helpers);
34
35struct nf_conntrack_helper *
36__nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
37{
38	struct nf_conntrack_helper *h;
39
40	list_for_each_entry(h, &helpers, list) {
41		if (nf_ct_tuple_mask_cmp(tuple, &h->tuple, &h->mask))
42			return h;
43	}
44	return NULL;
45}
46
47struct nf_conntrack_helper *
48nf_ct_helper_find_get( const struct nf_conntrack_tuple *tuple)
49{
50	struct nf_conntrack_helper *helper;
51
52	/* need nf_conntrack_lock to assure that helper exists until
53	 * try_module_get() is called */
54	read_lock_bh(&nf_conntrack_lock);
55
56	helper = __nf_ct_helper_find(tuple);
57	if (helper) {
58		/* need to increase module usage count to assure helper will
59		 * not go away while the caller is e.g. busy putting a
60		 * conntrack in the hash that uses the helper */
61		if (!try_module_get(helper->me))
62			helper = NULL;
63	}
64
65	read_unlock_bh(&nf_conntrack_lock);
66
67	return helper;
68}
69
70void nf_ct_helper_put(struct nf_conntrack_helper *helper)
71{
72	module_put(helper->me);
73}
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}
87
88static inline int unhelp(struct nf_conntrack_tuple_hash *i,
89			 const struct nf_conntrack_helper *me)
90{
91	struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
92	struct nf_conn_help *help = nfct_help(ct);
93
94	if (help && help->helper == me) {
95		nf_conntrack_event(IPCT_HELPER, ct);
96		help->helper = NULL;
97	}
98	return 0;
99}
100
101int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
102{
103	int ret;
104	BUG_ON(me->timeout == 0);
105
106	ret = nf_conntrack_register_cache(NF_CT_F_HELP, "nf_conntrack:help",
107					  sizeof(struct nf_conn)
108					  + sizeof(struct nf_conn_help)
109					  + __alignof__(struct nf_conn_help));
110	if (ret < 0) {
111		printk(KERN_ERR "nf_conntrack_helper_register: Unable to create slab cache for conntracks\n");
112		return ret;
113	}
114	write_lock_bh(&nf_conntrack_lock);
115	list_add(&me->list, &helpers);
116	write_unlock_bh(&nf_conntrack_lock);
117
118	return 0;
119}
120
121void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
122{
123	unsigned int i;
124	struct nf_conntrack_tuple_hash *h;
125	struct nf_conntrack_expect *exp, *tmp;
126
127	/* Need write lock here, to delete helper. */
128	write_lock_bh(&nf_conntrack_lock);
129	list_del(&me->list);
130
131	/* Get rid of expectations */
132	list_for_each_entry_safe(exp, tmp, &nf_conntrack_expect_list, list) {
133		struct nf_conn_help *help = nfct_help(exp->master);
134		if (help->helper == me && del_timer(&exp->timeout)) {
135			nf_ct_unlink_expect(exp);
136			nf_conntrack_expect_put(exp);
137		}
138	}
139
140	/* Get rid of expecteds, set helpers to NULL. */
141	list_for_each_entry(h, &unconfirmed, list)
142		unhelp(h, me);
143	for (i = 0; i < nf_conntrack_htable_size; i++) {
144		list_for_each_entry(h, &nf_conntrack_hash[i], list)
145			unhelp(h, me);
146	}
147	write_unlock_bh(&nf_conntrack_lock);
148
149	/* Someone could be still looking at the helper in a bh. */
150	synchronize_net();
151}
152