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