IPv6: fix race between cleanup and add/delete address
[linux-2.6.git] / net / netfilter / nf_conntrack_helper.c
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
33 static DEFINE_MUTEX(nf_ct_helper_mutex);
34 static struct hlist_head *nf_ct_helper_hash __read_mostly;
35 static unsigned int nf_ct_helper_hsize __read_mostly;
36 static unsigned int nf_ct_helper_count __read_mostly;
37 static 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. */
42 static 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
48 static 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
67 struct 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 }
84 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find);
85
86 struct nf_conntrack_helper *
87 nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
88 {
89         struct nf_conntrack_helper *h;
90
91         h = __nf_conntrack_helper_find(name, l3num, protonum);
92 #ifdef CONFIG_MODULES
93         if (h == NULL) {
94                 if (request_module("nfct-helper-%s", name) == 0)
95                         h = __nf_conntrack_helper_find(name, l3num, protonum);
96         }
97 #endif
98         if (h != NULL && !try_module_get(h->me))
99                 h = NULL;
100
101         return h;
102 }
103 EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);
104
105 struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
106 {
107         struct nf_conn_help *help;
108
109         help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
110         if (help)
111                 INIT_HLIST_HEAD(&help->expectations);
112         else
113                 pr_debug("failed to add helper extension area");
114         return help;
115 }
116 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
117
118 int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
119                               gfp_t flags)
120 {
121         struct nf_conntrack_helper *helper = NULL;
122         struct nf_conn_help *help;
123         int ret = 0;
124
125         if (tmpl != NULL) {
126                 help = nfct_help(tmpl);
127                 if (help != NULL)
128                         helper = help->helper;
129         }
130
131         help = nfct_help(ct);
132         if (helper == NULL)
133                 helper = __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
134         if (helper == NULL) {
135                 if (help)
136                         rcu_assign_pointer(help->helper, NULL);
137                 goto out;
138         }
139
140         if (help == NULL) {
141                 help = nf_ct_helper_ext_add(ct, flags);
142                 if (help == NULL) {
143                         ret = -ENOMEM;
144                         goto out;
145                 }
146         } else {
147                 memset(&help->help, 0, sizeof(help->help));
148         }
149
150         rcu_assign_pointer(help->helper, helper);
151 out:
152         return ret;
153 }
154 EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
155
156 static inline int unhelp(struct nf_conntrack_tuple_hash *i,
157                          const struct nf_conntrack_helper *me)
158 {
159         struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
160         struct nf_conn_help *help = nfct_help(ct);
161
162         if (help && help->helper == me) {
163                 nf_conntrack_event(IPCT_HELPER, ct);
164                 rcu_assign_pointer(help->helper, NULL);
165         }
166         return 0;
167 }
168
169 void nf_ct_helper_destroy(struct nf_conn *ct)
170 {
171         struct nf_conn_help *help = nfct_help(ct);
172         struct nf_conntrack_helper *helper;
173
174         if (help) {
175                 rcu_read_lock();
176                 helper = rcu_dereference(help->helper);
177                 if (helper && helper->destroy)
178                         helper->destroy(ct);
179                 rcu_read_unlock();
180         }
181 }
182
183 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
184 {
185         unsigned int h = helper_hash(&me->tuple);
186
187         BUG_ON(me->expect_policy == NULL);
188         BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
189         BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
190
191         mutex_lock(&nf_ct_helper_mutex);
192         hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
193         nf_ct_helper_count++;
194         mutex_unlock(&nf_ct_helper_mutex);
195
196         return 0;
197 }
198 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
199
200 static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
201                                              struct net *net)
202 {
203         struct nf_conntrack_tuple_hash *h;
204         struct nf_conntrack_expect *exp;
205         const struct hlist_node *n, *next;
206         const struct hlist_nulls_node *nn;
207         unsigned int i;
208
209         /* Get rid of expectations */
210         for (i = 0; i < nf_ct_expect_hsize; i++) {
211                 hlist_for_each_entry_safe(exp, n, next,
212                                           &net->ct.expect_hash[i], hnode) {
213                         struct nf_conn_help *help = nfct_help(exp->master);
214                         if ((help->helper == me || exp->helper == me) &&
215                             del_timer(&exp->timeout)) {
216                                 nf_ct_unlink_expect(exp);
217                                 nf_ct_expect_put(exp);
218                         }
219                 }
220         }
221
222         /* Get rid of expecteds, set helpers to NULL. */
223         hlist_nulls_for_each_entry(h, nn, &net->ct.unconfirmed, hnnode)
224                 unhelp(h, me);
225         for (i = 0; i < net->ct.htable_size; i++) {
226                 hlist_nulls_for_each_entry(h, nn, &net->ct.hash[i], hnnode)
227                         unhelp(h, me);
228         }
229 }
230
231 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
232 {
233         struct net *net;
234
235         mutex_lock(&nf_ct_helper_mutex);
236         hlist_del_rcu(&me->hnode);
237         nf_ct_helper_count--;
238         mutex_unlock(&nf_ct_helper_mutex);
239
240         /* Make sure every nothing is still using the helper unless its a
241          * connection in the hash.
242          */
243         synchronize_rcu();
244
245         rtnl_lock();
246         spin_lock_bh(&nf_conntrack_lock);
247         for_each_net(net)
248                 __nf_conntrack_helper_unregister(me, net);
249         spin_unlock_bh(&nf_conntrack_lock);
250         rtnl_unlock();
251 }
252 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
253
254 static struct nf_ct_ext_type helper_extend __read_mostly = {
255         .len    = sizeof(struct nf_conn_help),
256         .align  = __alignof__(struct nf_conn_help),
257         .id     = NF_CT_EXT_HELPER,
258 };
259
260 int nf_conntrack_helper_init(void)
261 {
262         int err;
263
264         nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
265         nf_ct_helper_hash = nf_ct_alloc_hashtable(&nf_ct_helper_hsize,
266                                                   &nf_ct_helper_vmalloc, 0);
267         if (!nf_ct_helper_hash)
268                 return -ENOMEM;
269
270         err = nf_ct_extend_register(&helper_extend);
271         if (err < 0)
272                 goto err1;
273
274         return 0;
275
276 err1:
277         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
278                              nf_ct_helper_hsize);
279         return err;
280 }
281
282 void nf_conntrack_helper_fini(void)
283 {
284         nf_ct_extend_unregister(&helper_extend);
285         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
286                              nf_ct_helper_hsize);
287 }