nf_conntrack_helper.c revision b8a7fe6c10511fce10b20efa163123f4041f2550 
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 struct hlist_head *nf_ct_helper_hash __read_mostly;
32static unsigned int nf_ct_helper_hsize __read_mostly;
33static unsigned int nf_ct_helper_count __read_mostly;
34static int nf_ct_helper_vmalloc;
35
36
37/* Stupid hash, but collision free for the default registrations of the
38 * helpers currently in the kernel. */
39static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
40{
41	return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
42		tuple->src.u.all) % nf_ct_helper_hsize;
43}
44
45struct nf_conntrack_helper *
46__nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
47{
48	struct nf_conntrack_helper *helper;
49	struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
50	struct hlist_node *n;
51	unsigned int h;
52
53	if (!nf_ct_helper_count)
54		return NULL;
55
56	h = helper_hash(tuple);
57	hlist_for_each_entry(helper, n, &nf_ct_helper_hash[h], hnode) {
58		if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
59			return helper;
60	}
61	return NULL;
62}
63
64struct nf_conntrack_helper *
65nf_ct_helper_find_get(const struct nf_conntrack_tuple *tuple)
66{
67	struct nf_conntrack_helper *helper;
68
69	/* need nf_conntrack_lock to assure that helper exists until
70	 * try_module_get() is called */
71	read_lock_bh(&nf_conntrack_lock);
72
73	helper = __nf_ct_helper_find(tuple);
74	if (helper) {
75		/* need to increase module usage count to assure helper will
76		 * not go away while the caller is e.g. busy putting a
77		 * conntrack in the hash that uses the helper */
78		if (!try_module_get(helper->me))
79			helper = NULL;
80	}
81
82	read_unlock_bh(&nf_conntrack_lock);
83
84	return helper;
85}
86EXPORT_SYMBOL_GPL(nf_ct_helper_find_get);
87
88void nf_ct_helper_put(struct nf_conntrack_helper *helper)
89{
90	module_put(helper->me);
91}
92EXPORT_SYMBOL_GPL(nf_ct_helper_put);
93
94struct nf_conntrack_helper *
95__nf_conntrack_helper_find_byname(const char *name)
96{
97	struct nf_conntrack_helper *h;
98	struct hlist_node *n;
99	unsigned int i;
100
101	for (i = 0; i < nf_ct_helper_hsize; i++) {
102		hlist_for_each_entry(h, n, &nf_ct_helper_hash[i], hnode) {
103			if (!strcmp(h->name, name))
104				return h;
105		}
106	}
107	return NULL;
108}
109EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find_byname);
110
111struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
112{
113	struct nf_conn_help *help;
114
115	help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
116	if (help)
117		INIT_HLIST_HEAD(&help->expectations);
118	else
119		pr_debug("failed to add helper extension area");
120	return help;
121}
122EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
123
124static inline int unhelp(struct nf_conntrack_tuple_hash *i,
125			 const struct nf_conntrack_helper *me)
126{
127	struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
128	struct nf_conn_help *help = nfct_help(ct);
129
130	if (help && help->helper == me) {
131		nf_conntrack_event(IPCT_HELPER, ct);
132		rcu_assign_pointer(help->helper, NULL);
133	}
134	return 0;
135}
136
137int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
138{
139	unsigned int h = helper_hash(&me->tuple);
140
141	BUG_ON(me->timeout == 0);
142
143	write_lock_bh(&nf_conntrack_lock);
144	hlist_add_head(&me->hnode, &nf_ct_helper_hash[h]);
145	nf_ct_helper_count++;
146	write_unlock_bh(&nf_conntrack_lock);
147
148	return 0;
149}
150EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
151
152void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
153{
154	struct nf_conntrack_tuple_hash *h;
155	struct nf_conntrack_expect *exp;
156	struct hlist_node *n, *next;
157	unsigned int i;
158
159	/* Need write lock here, to delete helper. */
160	write_lock_bh(&nf_conntrack_lock);
161	hlist_del(&me->hnode);
162	nf_ct_helper_count--;
163
164	/* Get rid of expectations */
165	for (i = 0; i < nf_ct_expect_hsize; i++) {
166		hlist_for_each_entry_safe(exp, n, next,
167					  &nf_ct_expect_hash[i], hnode) {
168			struct nf_conn_help *help = nfct_help(exp->master);
169			if ((help->helper == me || exp->helper == me) &&
170			    del_timer(&exp->timeout)) {
171				nf_ct_unlink_expect(exp);
172				nf_ct_expect_put(exp);
173			}
174		}
175	}
176
177	/* Get rid of expecteds, set helpers to NULL. */
178	hlist_for_each_entry(h, n, &unconfirmed, hnode)
179		unhelp(h, me);
180	for (i = 0; i < nf_conntrack_htable_size; i++) {
181		hlist_for_each_entry(h, n, &nf_conntrack_hash[i], hnode)
182			unhelp(h, me);
183	}
184	write_unlock_bh(&nf_conntrack_lock);
185
186	/* Someone could be still looking at the helper in a bh. */
187	synchronize_net();
188}
189EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
190
191static struct nf_ct_ext_type helper_extend __read_mostly = {
192	.len	= sizeof(struct nf_conn_help),
193	.align	= __alignof__(struct nf_conn_help),
194	.id	= NF_CT_EXT_HELPER,
195};
196
197int nf_conntrack_helper_init()
198{
199	int err;
200
201	nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
202	nf_ct_helper_hash = nf_ct_alloc_hashtable(&nf_ct_helper_hsize,
203						  &nf_ct_helper_vmalloc);
204	if (!nf_ct_helper_hash)
205		return -ENOMEM;
206
207	err = nf_ct_extend_register(&helper_extend);
208	if (err < 0)
209		goto err1;
210
211	return 0;
212
213err1:
214	nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
215			     nf_ct_helper_hsize);
216	return err;
217}
218
219void nf_conntrack_helper_fini()
220{
221	nf_ct_extend_unregister(&helper_extend);
222	nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
223			     nf_ct_helper_hsize);
224}
225