netfilter: limit the length of the helper name
[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_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 }
82 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find_byname);
83
84 struct 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 }
95 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
96
97 int __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);
121 out:
122         return ret;
123 }
124 EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
125
126 static 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
139 int 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 }
154 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
155
156 static 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
186 void 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 }
207 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
208
209 static 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
215 int 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
231 err1:
232         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
233                              nf_ct_helper_hsize);
234         return err;
235 }
236
237 void 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 }