nf_conntrack_helper.c revision 794e68716bab578ae8f8912dc934496d7c7abc90 
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#include <linux/rculist.h>
24#include <linux/rtnetlink.h>
25
26#include <net/netfilter/nf_conntrack.h>
27#include <net/netfilter/nf_conntrack_l3proto.h>
28#include <net/netfilter/nf_conntrack_l4proto.h>
29#include <net/netfilter/nf_conntrack_helper.h>
30#include <net/netfilter/nf_conntrack_core.h>
31#include <net/netfilter/nf_conntrack_extend.h>
32
33static DEFINE_MUTEX(nf_ct_helper_mutex);
34static struct hlist_head *nf_ct_helper_hash __read_mostly;
35static unsigned int nf_ct_helper_hsize __read_mostly;
36static unsigned int nf_ct_helper_count __read_mostly;
37static int nf_ct_helper_vmalloc;
38
39
40/* Stupid hash, but collision free for the default registrations of the
41 * helpers currently in the kernel. */
42static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
43{
44	return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
45		(__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
46}
47
48static struct nf_conntrack_helper *
49__nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
50{
51	struct nf_conntrack_helper *helper;
52	struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
53	struct hlist_node *n;
54	unsigned int h;
55
56	if (!nf_ct_helper_count)
57		return NULL;
58
59	h = helper_hash(tuple);
60	hlist_for_each_entry_rcu(helper, n, &nf_ct_helper_hash[h], hnode) {
61		if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
62			return helper;
63	}
64	return NULL;
65}
66
67struct nf_conntrack_helper *
68__nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum)
69{
70	struct nf_conntrack_helper *h;
71	struct hlist_node *n;
72	unsigned int i;
73
74	for (i = 0; i < nf_ct_helper_hsize; i++) {
75		hlist_for_each_entry_rcu(h, n, &nf_ct_helper_hash[i], hnode) {
76			if (!strcmp(h->name, name) &&
77			    h->tuple.src.l3num == l3num &&
78			    h->tuple.dst.protonum == protonum)
79				return h;
80		}
81	}
82	return NULL;
83}
84EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find);
85
86struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
87{
88	struct nf_conn_help *help;
89
90	help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
91	if (help)
92		INIT_HLIST_HEAD(&help->expectations);
93	else
94		pr_debug("failed to add helper extension area");
95	return help;
96}
97EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
98
99int __nf_ct_try_assign_helper(struct nf_conn *ct, gfp_t flags)
100{
101	int ret = 0;
102	struct nf_conntrack_helper *helper;
103	struct nf_conn_help *help = nfct_help(ct);
104
105	helper = __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
106	if (helper == NULL) {
107		if (help)
108			rcu_assign_pointer(help->helper, NULL);
109		goto out;
110	}
111
112	if (help == NULL) {
113		help = nf_ct_helper_ext_add(ct, flags);
114		if (help == NULL) {
115			ret = -ENOMEM;
116			goto out;
117		}
118	} else {
119		memset(&help->help, 0, sizeof(help->help));
120	}
121
122	rcu_assign_pointer(help->helper, helper);
123out:
124	return ret;
125}
126EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
127
128static inline int unhelp(struct nf_conntrack_tuple_hash *i,
129			 const struct nf_conntrack_helper *me)
130{
131	struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
132	struct nf_conn_help *help = nfct_help(ct);
133
134	if (help && help->helper == me) {
135		nf_conntrack_event(IPCT_HELPER, ct);
136		rcu_assign_pointer(help->helper, NULL);
137	}
138	return 0;
139}
140
141void nf_ct_helper_destroy(struct nf_conn *ct)
142{
143	struct nf_conn_help *help = nfct_help(ct);
144	struct nf_conntrack_helper *helper;
145
146	if (help) {
147		rcu_read_lock();
148		helper = rcu_dereference(help->helper);
149		if (helper && helper->destroy)
150			helper->destroy(ct);
151		rcu_read_unlock();
152	}
153}
154
155int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
156{
157	unsigned int h = helper_hash(&me->tuple);
158
159	BUG_ON(me->expect_policy == NULL);
160	BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
161	BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
162
163	mutex_lock(&nf_ct_helper_mutex);
164	hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
165	nf_ct_helper_count++;
166	mutex_unlock(&nf_ct_helper_mutex);
167
168	return 0;
169}
170EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
171
172static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
173					     struct net *net)
174{
175	struct nf_conntrack_tuple_hash *h;
176	struct nf_conntrack_expect *exp;
177	const struct hlist_node *n, *next;
178	const struct hlist_nulls_node *nn;
179	unsigned int i;
180
181	/* Get rid of expectations */
182	for (i = 0; i < nf_ct_expect_hsize; i++) {
183		hlist_for_each_entry_safe(exp, n, next,
184					  &net->ct.expect_hash[i], hnode) {
185			struct nf_conn_help *help = nfct_help(exp->master);
186			if ((help->helper == me || exp->helper == me) &&
187			    del_timer(&exp->timeout)) {
188				nf_ct_unlink_expect(exp);
189				nf_ct_expect_put(exp);
190			}
191		}
192	}
193
194	/* Get rid of expecteds, set helpers to NULL. */
195	hlist_nulls_for_each_entry(h, nn, &net->ct.unconfirmed, hnnode)
196		unhelp(h, me);
197	for (i = 0; i < nf_conntrack_htable_size; i++) {
198		hlist_nulls_for_each_entry(h, nn, &net->ct.hash[i], hnnode)
199			unhelp(h, me);
200	}
201}
202
203void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
204{
205	struct net *net;
206
207	mutex_lock(&nf_ct_helper_mutex);
208	hlist_del_rcu(&me->hnode);
209	nf_ct_helper_count--;
210	mutex_unlock(&nf_ct_helper_mutex);
211
212	/* Make sure every nothing is still using the helper unless its a
213	 * connection in the hash.
214	 */
215	synchronize_rcu();
216
217	rtnl_lock();
218	spin_lock_bh(&nf_conntrack_lock);
219	for_each_net(net)
220		__nf_conntrack_helper_unregister(me, net);
221	spin_unlock_bh(&nf_conntrack_lock);
222	rtnl_unlock();
223}
224EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
225
226static struct nf_ct_ext_type helper_extend __read_mostly = {
227	.len	= sizeof(struct nf_conn_help),
228	.align	= __alignof__(struct nf_conn_help),
229	.id	= NF_CT_EXT_HELPER,
230};
231
232int nf_conntrack_helper_init(void)
233{
234	int err;
235
236	nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
237	nf_ct_helper_hash = nf_ct_alloc_hashtable(&nf_ct_helper_hsize,
238						  &nf_ct_helper_vmalloc, 0);
239	if (!nf_ct_helper_hash)
240		return -ENOMEM;
241
242	err = nf_ct_extend_register(&helper_extend);
243	if (err < 0)
244		goto err1;
245
246	return 0;
247
248err1:
249	nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
250			     nf_ct_helper_hsize);
251	return err;
252}
253
254void nf_conntrack_helper_fini(void)
255{
256	nf_ct_extend_unregister(&helper_extend);
257	nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
258			     nf_ct_helper_hsize);
259}
260