nf_conntrack_helper.c revision 226c0c0ef2abdf91b8d9cce1aaf7d4635a5e5926 
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
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;
36static int nf_ct_helper_vmalloc;
37
38
39/* Stupid hash, but collision free for the default registrations of the
40 * helpers currently in the kernel. */
41static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
42{
43	return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
44		(__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
45}
46
47static struct nf_conntrack_helper *
48__nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
49{
50	struct nf_conntrack_helper *helper;
51	struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
52	struct hlist_node *n;
53	unsigned int h;
54
55	if (!nf_ct_helper_count)
56		return NULL;
57
58	h = helper_hash(tuple);
59	hlist_for_each_entry_rcu(helper, n, &nf_ct_helper_hash[h], hnode) {
60		if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
61			return helper;
62	}
63	return NULL;
64}
65
66struct nf_conntrack_helper *
67__nf_conntrack_helper_find_byname(const char *name)
68{
69	struct nf_conntrack_helper *h;
70	struct hlist_node *n;
71	unsigned int i;
72
73	for (i = 0; i < nf_ct_helper_hsize; i++) {
74		hlist_for_each_entry_rcu(h, n, &nf_ct_helper_hash[i], hnode) {
75			if (!strcmp(h->name, name))
76				return h;
77		}
78	}
79	return NULL;
80}
81EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find_byname);
82
83struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
84{
85	struct nf_conn_help *help;
86
87	help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
88	if (help)
89		INIT_HLIST_HEAD(&help->expectations);
90	else
91		pr_debug("failed to add helper extension area");
92	return help;
93}
94EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
95
96int __nf_ct_try_assign_helper(struct nf_conn *ct, gfp_t flags)
97{
98	int ret = 0;
99	struct nf_conntrack_helper *helper;
100	struct nf_conn_help *help = nfct_help(ct);
101
102	helper = __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
103	if (helper == NULL) {
104		if (help)
105			rcu_assign_pointer(help->helper, NULL);
106		goto out;
107	}
108
109	if (help == NULL) {
110		help = nf_ct_helper_ext_add(ct, flags);
111		if (help == NULL) {
112			ret = -ENOMEM;
113			goto out;
114		}
115	} else {
116		memset(&help->help, 0, sizeof(help->help));
117	}
118
119	rcu_assign_pointer(help->helper, helper);
120out:
121	return ret;
122}
123EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
124
125static inline int unhelp(struct nf_conntrack_tuple_hash *i,
126			 const struct nf_conntrack_helper *me)
127{
128	struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
129	struct nf_conn_help *help = nfct_help(ct);
130
131	if (help && help->helper == me) {
132		nf_conntrack_event(IPCT_HELPER, ct);
133		rcu_assign_pointer(help->helper, NULL);
134	}
135	return 0;
136}
137
138int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
139{
140	unsigned int h = helper_hash(&me->tuple);
141
142	BUG_ON(me->expect_policy == NULL);
143	BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
144
145	mutex_lock(&nf_ct_helper_mutex);
146	hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
147	nf_ct_helper_count++;
148	mutex_unlock(&nf_ct_helper_mutex);
149
150	return 0;
151}
152EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
153
154static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
155					     struct net *net)
156{
157	struct nf_conntrack_tuple_hash *h;
158	struct nf_conntrack_expect *exp;
159	const struct hlist_node *n, *next;
160	unsigned int i;
161
162	/* Get rid of expectations */
163	for (i = 0; i < nf_ct_expect_hsize; i++) {
164		hlist_for_each_entry_safe(exp, n, next,
165					  &net->ct.expect_hash[i], hnode) {
166			struct nf_conn_help *help = nfct_help(exp->master);
167			if ((help->helper == me || exp->helper == me) &&
168			    del_timer(&exp->timeout)) {
169				nf_ct_unlink_expect(exp);
170				nf_ct_expect_put(exp);
171			}
172		}
173	}
174
175	/* Get rid of expecteds, set helpers to NULL. */
176	hlist_for_each_entry(h, n, &net->ct.unconfirmed, hnode)
177		unhelp(h, me);
178	for (i = 0; i < nf_conntrack_htable_size; i++) {
179		hlist_for_each_entry(h, n, &net->ct.hash[i], hnode)
180			unhelp(h, me);
181	}
182}
183
184void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
185{
186	struct net *net;
187
188	mutex_lock(&nf_ct_helper_mutex);
189	hlist_del_rcu(&me->hnode);
190	nf_ct_helper_count--;
191	mutex_unlock(&nf_ct_helper_mutex);
192
193	/* Make sure every nothing is still using the helper unless its a
194	 * connection in the hash.
195	 */
196	synchronize_rcu();
197
198	spin_lock_bh(&nf_conntrack_lock);
199	for_each_net(net)
200		__nf_conntrack_helper_unregister(me, net);
201	spin_unlock_bh(&nf_conntrack_lock);
202}
203EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
204
205static struct nf_ct_ext_type helper_extend __read_mostly = {
206	.len	= sizeof(struct nf_conn_help),
207	.align	= __alignof__(struct nf_conn_help),
208	.id	= NF_CT_EXT_HELPER,
209};
210
211int nf_conntrack_helper_init(void)
212{
213	int err;
214
215	nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
216	nf_ct_helper_hash = nf_ct_alloc_hashtable(&nf_ct_helper_hsize,
217						  &nf_ct_helper_vmalloc);
218	if (!nf_ct_helper_hash)
219		return -ENOMEM;
220
221	err = nf_ct_extend_register(&helper_extend);
222	if (err < 0)
223		goto err1;
224
225	return 0;
226
227err1:
228	nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
229			     nf_ct_helper_hsize);
230	return err;
231}
232
233void nf_conntrack_helper_fini(void)
234{
235	nf_ct_extend_unregister(&helper_extend);
236	nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
237			     nf_ct_helper_hsize);
238}
239