nf_conntrack_helper.c revision 9b03f38d0487f3908696242286d934c9b38f9d2a 
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
47struct 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}
65EXPORT_SYMBOL_GPL(__nf_ct_helper_find);
66
67struct nf_conntrack_helper *
68__nf_conntrack_helper_find_byname(const char *name)
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				return h;
78		}
79	}
80	return NULL;
81}
82EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find_byname);
83
84struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
85{
86	struct nf_conn_help *help;
87
88	help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
89	if (help)
90		INIT_HLIST_HEAD(&help->expectations);
91	else
92		pr_debug("failed to add helper extension area");
93	return help;
94}
95EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
96
97static inline int unhelp(struct nf_conntrack_tuple_hash *i,
98			 const struct nf_conntrack_helper *me)
99{
100	struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
101	struct nf_conn_help *help = nfct_help(ct);
102
103	if (help && help->helper == me) {
104		nf_conntrack_event(IPCT_HELPER, ct);
105		rcu_assign_pointer(help->helper, NULL);
106	}
107	return 0;
108}
109
110int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
111{
112	unsigned int h = helper_hash(&me->tuple);
113
114	BUG_ON(me->expect_policy == NULL);
115	BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
116
117	mutex_lock(&nf_ct_helper_mutex);
118	hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
119	nf_ct_helper_count++;
120	mutex_unlock(&nf_ct_helper_mutex);
121
122	return 0;
123}
124EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
125
126void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
127{
128	struct nf_conntrack_tuple_hash *h;
129	struct nf_conntrack_expect *exp;
130	const struct hlist_node *n, *next;
131	unsigned int i;
132
133	mutex_lock(&nf_ct_helper_mutex);
134	hlist_del_rcu(&me->hnode);
135	nf_ct_helper_count--;
136	mutex_unlock(&nf_ct_helper_mutex);
137
138	/* Make sure every nothing is still using the helper unless its a
139	 * connection in the hash.
140	 */
141	synchronize_rcu();
142
143	spin_lock_bh(&nf_conntrack_lock);
144
145	/* Get rid of expectations */
146	for (i = 0; i < nf_ct_expect_hsize; i++) {
147		hlist_for_each_entry_safe(exp, n, next,
148					  &init_net.ct.expect_hash[i], hnode) {
149			struct nf_conn_help *help = nfct_help(exp->master);
150			if ((help->helper == me || exp->helper == me) &&
151			    del_timer(&exp->timeout)) {
152				nf_ct_unlink_expect(exp);
153				nf_ct_expect_put(exp);
154			}
155		}
156	}
157
158	/* Get rid of expecteds, set helpers to NULL. */
159	hlist_for_each_entry(h, n, &unconfirmed, hnode)
160		unhelp(h, me);
161	for (i = 0; i < nf_conntrack_htable_size; i++) {
162		hlist_for_each_entry(h, n, &init_net.ct.hash[i], hnode)
163			unhelp(h, me);
164	}
165	spin_unlock_bh(&nf_conntrack_lock);
166}
167EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
168
169static struct nf_ct_ext_type helper_extend __read_mostly = {
170	.len	= sizeof(struct nf_conn_help),
171	.align	= __alignof__(struct nf_conn_help),
172	.id	= NF_CT_EXT_HELPER,
173};
174
175int nf_conntrack_helper_init(void)
176{
177	int err;
178
179	nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
180	nf_ct_helper_hash = nf_ct_alloc_hashtable(&nf_ct_helper_hsize,
181						  &nf_ct_helper_vmalloc);
182	if (!nf_ct_helper_hash)
183		return -ENOMEM;
184
185	err = nf_ct_extend_register(&helper_extend);
186	if (err < 0)
187		goto err1;
188
189	return 0;
190
191err1:
192	nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
193			     nf_ct_helper_hsize);
194	return err;
195}
196
197void nf_conntrack_helper_fini(void)
198{
199	nf_ct_extend_unregister(&helper_extend);
200	nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
201			     nf_ct_helper_hsize);
202}
203