summaryrefslogtreecommitdiff
path: root/net/netfilter/nf_conntrack_helper.c
blob: bbe23baa19b64f4df7b2532b1471614a5315cc26 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
/* Helper handling for netfilter. */

/* (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
 * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/types.h>
#include <linux/netfilter.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/vmalloc.h>
#include <linux/stddef.h>
#include <linux/random.h>
#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/rculist.h>
#include <linux/rtnetlink.h>

#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_l3proto.h>
#include <net/netfilter/nf_conntrack_l4proto.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/nf_conntrack_extend.h>

static DEFINE_MUTEX(nf_ct_helper_mutex);
static struct hlist_head *nf_ct_helper_hash __read_mostly;
static unsigned int nf_ct_helper_hsize __read_mostly;
static unsigned int nf_ct_helper_count __read_mostly;


/* Stupid hash, but collision free for the default registrations of the
 * helpers currently in the kernel. */
static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
{
	return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
		(__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
}

static struct nf_conntrack_helper *
__nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
{
	struct nf_conntrack_helper *helper;
	struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
	struct hlist_node *n;
	unsigned int h;

	if (!nf_ct_helper_count)
		return NULL;

	h = helper_hash(tuple);
	hlist_for_each_entry_rcu(helper, n, &nf_ct_helper_hash[h], hnode) {
		if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
			return helper;
	}
	return NULL;
}

struct nf_conntrack_helper *
__nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum)
{
	struct nf_conntrack_helper *h;
	struct hlist_node *n;
	unsigned int i;

	for (i = 0; i < nf_ct_helper_hsize; i++) {
		hlist_for_each_entry_rcu(h, n, &nf_ct_helper_hash[i], hnode) {
			if (!strcmp(h->name, name) &&
			    h->tuple.src.l3num == l3num &&
			    h->tuple.dst.protonum == protonum)
				return h;
		}
	}
	return NULL;
}
EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find);

struct nf_conntrack_helper *
nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
{
	struct nf_conntrack_helper *h;

	h = __nf_conntrack_helper_find(name, l3num, protonum);
#ifdef CONFIG_MODULES
	if (h == NULL) {
		if (request_module("nfct-helper-%s", name) == 0)
			h = __nf_conntrack_helper_find(name, l3num, protonum);
	}
#endif
	if (h != NULL && !try_module_get(h->me))
		h = NULL;

	return h;
}
EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);

struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
{
	struct nf_conn_help *help;

	help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
	if (help)
		INIT_HLIST_HEAD(&help->expectations);
	else
		pr_debug("failed to add helper extension area");
	return help;
}
EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);

int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
			      gfp_t flags)
{
	struct nf_conntrack_helper *helper = NULL;
	struct nf_conn_help *help;
	int ret = 0;

	if (tmpl != NULL) {
		help = nfct_help(tmpl);
		if (help != NULL)
			helper = help->helper;
	}

	help = nfct_help(ct);
	if (helper == NULL)
		helper = __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
	if (helper == NULL) {
		if (help)
			RCU_INIT_POINTER(help->helper, NULL);
		goto out;
	}

	if (help == NULL) {
		help = nf_ct_helper_ext_add(ct, flags);
		if (help == NULL) {
			ret = -ENOMEM;
			goto out;
		}
	} else {
		memset(&help->help, 0, sizeof(help->help));
	}

	rcu_assign_pointer(help->helper, helper);
out:
	return ret;
}
EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);

static inline int unhelp(struct nf_conntrack_tuple_hash *i,
			 const struct nf_conntrack_helper *me)
{
	struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
	struct nf_conn_help *help = nfct_help(ct);

	if (help && rcu_dereference_protected(
			help->helper,
			lockdep_is_held(&nf_conntrack_lock)
			) == me) {
		nf_conntrack_event(IPCT_HELPER, ct);
		RCU_INIT_POINTER(help->helper, NULL);
	}
	return 0;
}

void nf_ct_helper_destroy(struct nf_conn *ct)
{
	struct nf_conn_help *help = nfct_help(ct);
	struct nf_conntrack_helper *helper;

	if (help) {
		rcu_read_lock();
		helper = rcu_dereference(help->helper);
		if (helper && helper->destroy)
			helper->destroy(ct);
		rcu_read_unlock();
	}
}

int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
{
	unsigned int h = helper_hash(&me->tuple);

	BUG_ON(me->expect_policy == NULL);
	BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
	BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);

	mutex_lock(&nf_ct_helper_mutex);
	hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
	nf_ct_helper_count++;
	mutex_unlock(&nf_ct_helper_mutex);

	return 0;
}
EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);

static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
					     struct net *net)
{
	struct nf_conntrack_tuple_hash *h;
	struct nf_conntrack_expect *exp;
	const struct hlist_node *n, *next;
	const struct hlist_nulls_node *nn;
	unsigned int i;

	/* Get rid of expectations */
	for (i = 0; i < nf_ct_expect_hsize; i++) {
		hlist_for_each_entry_safe(exp, n, next,
					  &net->ct.expect_hash[i], hnode) {
			struct nf_conn_help *help = nfct_help(exp->master);
			if ((rcu_dereference_protected(
					help->helper,
					lockdep_is_held(&nf_conntrack_lock)
					) == me || exp->helper == me) &&
			    del_timer(&exp->timeout)) {
				nf_ct_unlink_expect(exp);
				nf_ct_expect_put(exp);
			}
		}
	}

	/* Get rid of expecteds, set helpers to NULL. */
	hlist_nulls_for_each_entry(h, nn, &net->ct.unconfirmed, hnnode)
		unhelp(h, me);
	for (i = 0; i < net->ct.htable_size; i++) {
		hlist_nulls_for_each_entry(h, nn, &net->ct.hash[i], hnnode)
			unhelp(h, me);
	}
}

void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
{
	struct net *net;

	mutex_lock(&nf_ct_helper_mutex);
	hlist_del_rcu(&me->hnode);
	nf_ct_helper_count--;
	mutex_unlock(&nf_ct_helper_mutex);

	/* Make sure every nothing is still using the helper unless its a
	 * connection in the hash.
	 */
	synchronize_rcu();

	rtnl_lock();
	spin_lock_bh(&nf_conntrack_lock);
	for_each_net(net)
		__nf_conntrack_helper_unregister(me, net);
	spin_unlock_bh(&nf_conntrack_lock);
	rtnl_unlock();
}
EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);

static struct nf_ct_ext_type helper_extend __read_mostly = {
	.len	= sizeof(struct nf_conn_help),
	.align	= __alignof__(struct nf_conn_help),
	.id	= NF_CT_EXT_HELPER,
};

int nf_conntrack_helper_init(void)
{
	int err;

	nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
	nf_ct_helper_hash = nf_ct_alloc_hashtable(&nf_ct_helper_hsize, 0);
	if (!nf_ct_helper_hash)
		return -ENOMEM;

	err = nf_ct_extend_register(&helper_extend);
	if (err < 0)
		goto err1;

	return 0;

err1:
	nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize);
	return err;
}

void nf_conntrack_helper_fini(void)
{
	nf_ct_extend_unregister(&helper_extend);
	nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize);
}