nf_conntrack_helper.c revision cf778b00e96df6d64f8e21b8395d1f8a859ecdc7 
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/random.h>
19#include <linux/err.h>
20#include <linux/kernel.h>
21#include <linux/netdevice.h>
22#include <linux/rculist.h>
23#include <linux/rtnetlink.h>
24
25#include <net/netfilter/nf_conntrack.h>
26#include <net/netfilter/nf_conntrack_l3proto.h>
27#include <net/netfilter/nf_conntrack_l4proto.h>
28#include <net/netfilter/nf_conntrack_helper.h>
29#include <net/netfilter/nf_conntrack_core.h>
30#include <net/netfilter/nf_conntrack_extend.h>
31
32static DEFINE_MUTEX(nf_ct_helper_mutex);
33static struct hlist_head *nf_ct_helper_hash __read_mostly;
34static unsigned int nf_ct_helper_hsize __read_mostly;
35static unsigned int nf_ct_helper_count __read_mostly;
36
37
38/* Stupid hash, but collision free for the default registrations of the
39 * helpers currently in the kernel. */
40static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
41{
42	return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
43		(__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
44}
45
46static struct nf_conntrack_helper *
47__nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
48{
49	struct nf_conntrack_helper *helper;
50	struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
51	struct hlist_node *n;
52	unsigned int h;
53
54	if (!nf_ct_helper_count)
55		return NULL;
56
57	h = helper_hash(tuple);
58	hlist_for_each_entry_rcu(helper, n, &nf_ct_helper_hash[h], hnode) {
59		if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
60			return helper;
61	}
62	return NULL;
63}
64
65struct nf_conntrack_helper *
66__nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum)
67{
68	struct nf_conntrack_helper *h;
69	struct hlist_node *n;
70	unsigned int i;
71
72	for (i = 0; i < nf_ct_helper_hsize; i++) {
73		hlist_for_each_entry_rcu(h, n, &nf_ct_helper_hash[i], hnode) {
74			if (!strcmp(h->name, name) &&
75			    h->tuple.src.l3num == l3num &&
76			    h->tuple.dst.protonum == protonum)
77				return h;
78		}
79	}
80	return NULL;
81}
82EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find);
83
84struct nf_conntrack_helper *
85nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
86{
87	struct nf_conntrack_helper *h;
88
89	h = __nf_conntrack_helper_find(name, l3num, protonum);
90#ifdef CONFIG_MODULES
91	if (h == NULL) {
92		if (request_module("nfct-helper-%s", name) == 0)
93			h = __nf_conntrack_helper_find(name, l3num, protonum);
94	}
95#endif
96	if (h != NULL && !try_module_get(h->me))
97		h = NULL;
98
99	return h;
100}
101EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);
102
103struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
104{
105	struct nf_conn_help *help;
106
107	help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
108	if (help)
109		INIT_HLIST_HEAD(&help->expectations);
110	else
111		pr_debug("failed to add helper extension area");
112	return help;
113}
114EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
115
116int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
117			      gfp_t flags)
118{
119	struct nf_conntrack_helper *helper = NULL;
120	struct nf_conn_help *help;
121	int ret = 0;
122
123	if (tmpl != NULL) {
124		/* we've got a userspace helper. */
125		if (tmpl->status & IPS_USERSPACE_HELPER) {
126			help = nf_ct_helper_ext_add(ct, flags);
127			if (help == NULL) {
128				ret = -ENOMEM;
129				goto out;
130			}
131			rcu_assign_pointer(help->helper, NULL);
132			__set_bit(IPS_USERSPACE_HELPER_BIT, &ct->status);
133			ret = 0;
134			goto out;
135		}
136		help = nfct_help(tmpl);
137		if (help != NULL)
138			helper = help->helper;
139	}
140
141	help = nfct_help(ct);
142	if (helper == NULL)
143		helper = __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
144	if (helper == NULL) {
145		if (help)
146			RCU_INIT_POINTER(help->helper, NULL);
147		goto out;
148	}
149
150	if (help == NULL) {
151		help = nf_ct_helper_ext_add(ct, flags);
152		if (help == NULL) {
153			ret = -ENOMEM;
154			goto out;
155		}
156	} else {
157		memset(&help->help, 0, sizeof(help->help));
158	}
159
160	rcu_assign_pointer(help->helper, helper);
161out:
162	return ret;
163}
164EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
165
166static inline int unhelp(struct nf_conntrack_tuple_hash *i,
167			 const struct nf_conntrack_helper *me)
168{
169	struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
170	struct nf_conn_help *help = nfct_help(ct);
171
172	if (help && rcu_dereference_protected(
173			help->helper,
174			lockdep_is_held(&nf_conntrack_lock)
175			) == me) {
176		nf_conntrack_event(IPCT_HELPER, ct);
177		RCU_INIT_POINTER(help->helper, NULL);
178	}
179	return 0;
180}
181
182void nf_ct_helper_destroy(struct nf_conn *ct)
183{
184	struct nf_conn_help *help = nfct_help(ct);
185	struct nf_conntrack_helper *helper;
186
187	if (help) {
188		rcu_read_lock();
189		helper = rcu_dereference(help->helper);
190		if (helper && helper->destroy)
191			helper->destroy(ct);
192		rcu_read_unlock();
193	}
194}
195
196int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
197{
198	unsigned int h = helper_hash(&me->tuple);
199
200	BUG_ON(me->expect_policy == NULL);
201	BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
202	BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
203
204	mutex_lock(&nf_ct_helper_mutex);
205	hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
206	nf_ct_helper_count++;
207	mutex_unlock(&nf_ct_helper_mutex);
208
209	return 0;
210}
211EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
212
213static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
214					     struct net *net)
215{
216	struct nf_conntrack_tuple_hash *h;
217	struct nf_conntrack_expect *exp;
218	const struct hlist_node *n, *next;
219	const struct hlist_nulls_node *nn;
220	unsigned int i;
221
222	/* Get rid of expectations */
223	for (i = 0; i < nf_ct_expect_hsize; i++) {
224		hlist_for_each_entry_safe(exp, n, next,
225					  &net->ct.expect_hash[i], hnode) {
226			struct nf_conn_help *help = nfct_help(exp->master);
227			if ((rcu_dereference_protected(
228					help->helper,
229					lockdep_is_held(&nf_conntrack_lock)
230					) == me || exp->helper == me) &&
231			    del_timer(&exp->timeout)) {
232				nf_ct_unlink_expect(exp);
233				nf_ct_expect_put(exp);
234			}
235		}
236	}
237
238	/* Get rid of expecteds, set helpers to NULL. */
239	hlist_nulls_for_each_entry(h, nn, &net->ct.unconfirmed, hnnode)
240		unhelp(h, me);
241	for (i = 0; i < net->ct.htable_size; i++) {
242		hlist_nulls_for_each_entry(h, nn, &net->ct.hash[i], hnnode)
243			unhelp(h, me);
244	}
245}
246
247void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
248{
249	struct net *net;
250
251	mutex_lock(&nf_ct_helper_mutex);
252	hlist_del_rcu(&me->hnode);
253	nf_ct_helper_count--;
254	mutex_unlock(&nf_ct_helper_mutex);
255
256	/* Make sure every nothing is still using the helper unless its a
257	 * connection in the hash.
258	 */
259	synchronize_rcu();
260
261	rtnl_lock();
262	spin_lock_bh(&nf_conntrack_lock);
263	for_each_net(net)
264		__nf_conntrack_helper_unregister(me, net);
265	spin_unlock_bh(&nf_conntrack_lock);
266	rtnl_unlock();
267}
268EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
269
270static struct nf_ct_ext_type helper_extend __read_mostly = {
271	.len	= sizeof(struct nf_conn_help),
272	.align	= __alignof__(struct nf_conn_help),
273	.id	= NF_CT_EXT_HELPER,
274};
275
276int nf_conntrack_helper_init(void)
277{
278	int err;
279
280	nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
281	nf_ct_helper_hash = nf_ct_alloc_hashtable(&nf_ct_helper_hsize, 0);
282	if (!nf_ct_helper_hash)
283		return -ENOMEM;
284
285	err = nf_ct_extend_register(&helper_extend);
286	if (err < 0)
287		goto err1;
288
289	return 0;
290
291err1:
292	nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize);
293	return err;
294}
295
296void nf_conntrack_helper_fini(void)
297{
298	nf_ct_extend_unregister(&helper_extend);
299	nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize);
300}
301