nf_conntrack_helper.c revision af9d32ad6718b9a80fa89f557cc1fbb63a93ec15 
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_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
97int __nf_ct_try_assign_helper(struct nf_conn *ct, gfp_t flags)
98{
99	int ret = 0;
100	struct nf_conntrack_helper *helper;
101	struct nf_conn_help *help = nfct_help(ct);
102
103	helper = __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
104	if (helper == NULL) {
105		if (help)
106			rcu_assign_pointer(help->helper, NULL);
107		goto out;
108	}
109
110	if (help == NULL) {
111		help = nf_ct_helper_ext_add(ct, flags);
112		if (help == NULL) {
113			ret = -ENOMEM;
114			goto out;
115		}
116	} else {
117		memset(&help->help, 0, sizeof(help->help));
118	}
119
120	rcu_assign_pointer(help->helper, helper);
121out:
122	return ret;
123}
124EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
125
126static inline int unhelp(struct nf_conntrack_tuple_hash *i,
127			 const struct nf_conntrack_helper *me)
128{
129	struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
130	struct nf_conn_help *help = nfct_help(ct);
131
132	if (help && help->helper == me) {
133		nf_conntrack_event(IPCT_HELPER, ct);
134		rcu_assign_pointer(help->helper, NULL);
135	}
136	return 0;
137}
138
139int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
140{
141	unsigned int h = helper_hash(&me->tuple);
142
143	BUG_ON(me->expect_policy == NULL);
144	BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
145	BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
146
147	mutex_lock(&nf_ct_helper_mutex);
148	hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
149	nf_ct_helper_count++;
150	mutex_unlock(&nf_ct_helper_mutex);
151
152	return 0;
153}
154EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
155
156static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
157					     struct net *net)
158{
159	struct nf_conntrack_tuple_hash *h;
160	struct nf_conntrack_expect *exp;
161	const struct hlist_node *n, *next;
162	unsigned int i;
163
164	/* Get rid of expectations */
165	for (i = 0; i < nf_ct_expect_hsize; i++) {
166		hlist_for_each_entry_safe(exp, n, next,
167					  &net->ct.expect_hash[i], hnode) {
168			struct nf_conn_help *help = nfct_help(exp->master);
169			if ((help->helper == me || exp->helper == me) &&
170			    del_timer(&exp->timeout)) {
171				nf_ct_unlink_expect(exp);
172				nf_ct_expect_put(exp);
173			}
174		}
175	}
176
177	/* Get rid of expecteds, set helpers to NULL. */
178	hlist_for_each_entry(h, n, &net->ct.unconfirmed, hnode)
179		unhelp(h, me);
180	for (i = 0; i < nf_conntrack_htable_size; i++) {
181		hlist_for_each_entry(h, n, &net->ct.hash[i], hnode)
182			unhelp(h, me);
183	}
184}
185
186void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
187{
188	struct net *net;
189
190	mutex_lock(&nf_ct_helper_mutex);
191	hlist_del_rcu(&me->hnode);
192	nf_ct_helper_count--;
193	mutex_unlock(&nf_ct_helper_mutex);
194
195	/* Make sure every nothing is still using the helper unless its a
196	 * connection in the hash.
197	 */
198	synchronize_rcu();
199
200	rtnl_lock();
201	spin_lock_bh(&nf_conntrack_lock);
202	for_each_net(net)
203		__nf_conntrack_helper_unregister(me, net);
204	spin_unlock_bh(&nf_conntrack_lock);
205	rtnl_unlock();
206}
207EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
208
209static struct nf_ct_ext_type helper_extend __read_mostly = {
210	.len	= sizeof(struct nf_conn_help),
211	.align	= __alignof__(struct nf_conn_help),
212	.id	= NF_CT_EXT_HELPER,
213};
214
215int nf_conntrack_helper_init(void)
216{
217	int err;
218
219	nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
220	nf_ct_helper_hash = nf_ct_alloc_hashtable(&nf_ct_helper_hsize,
221						  &nf_ct_helper_vmalloc);
222	if (!nf_ct_helper_hash)
223		return -ENOMEM;
224
225	err = nf_ct_extend_register(&helper_extend);
226	if (err < 0)
227		goto err1;
228
229	return 0;
230
231err1:
232	nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
233			     nf_ct_helper_hsize);
234	return err;
235}
236
237void nf_conntrack_helper_fini(void)
238{
239	nf_ct_extend_unregister(&helper_extend);
240	nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
241			     nf_ct_helper_hsize);
242}
243