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 void nf_ct_helper_destroy(struct nf_conn *ct)
140 {
141 struct nf_conn_help *help = nfct_help(ct);
142 struct nf_conntrack_helper *helper;
143
144 if (help) {
145 rcu_read_lock();
146 helper = rcu_dereference(help->helper);
147 if (helper && helper->destroy)
148 helper->destroy(ct);
149 rcu_read_unlock();
150 }
151 }
152
153 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
154 {
155 unsigned int h = helper_hash(&me->tuple);
156
157 BUG_ON(me->expect_policy == NULL);
158 BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
159 BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
160
161 mutex_lock(&nf_ct_helper_mutex);
162 hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
163 nf_ct_helper_count++;
164 mutex_unlock(&nf_ct_helper_mutex);
165
166 return 0;
167 }
168 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
169
170 static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
171 struct net *net)
172 {
173 struct nf_conntrack_tuple_hash *h;
174 struct nf_conntrack_expect *exp;
175 const struct hlist_node *n, *next;
176 const struct hlist_nulls_node *nn;
177 unsigned int i;
178
179 /* Get rid of expectations */
180 for (i = 0; i < nf_ct_expect_hsize; i++) {
181 hlist_for_each_entry_safe(exp, n, next,
182 &net->ct.expect_hash[i], hnode) {
183 struct nf_conn_help *help = nfct_help(exp->master);
184 if ((help->helper == me || exp->helper == me) &&
185 del_timer(&exp->timeout)) {
186 nf_ct_unlink_expect(exp);
187 nf_ct_expect_put(exp);
188 }
189 }
190 }
191
192 /* Get rid of expecteds, set helpers to NULL. */
193 hlist_nulls_for_each_entry(h, nn, &net->ct.unconfirmed, hnnode)
194 unhelp(h, me);
195 for (i = 0; i < nf_conntrack_htable_size; i++) {
196 hlist_nulls_for_each_entry(h, nn, &net->ct.hash[i], hnnode)
197 unhelp(h, me);
198 }
199 }
200
201 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
202 {
203 struct net *net;
204
205 mutex_lock(&nf_ct_helper_mutex);
206 hlist_del_rcu(&me->hnode);
207 nf_ct_helper_count--;
208 mutex_unlock(&nf_ct_helper_mutex);
209
210 /* Make sure every nothing is still using the helper unless its a
211 * connection in the hash.
212 */
213 synchronize_rcu();
214
215 rtnl_lock();
216 spin_lock_bh(&nf_conntrack_lock);
217 for_each_net(net)
218 __nf_conntrack_helper_unregister(me, net);
219 spin_unlock_bh(&nf_conntrack_lock);
220 rtnl_unlock();
221 }
222 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
223
224 static struct nf_ct_ext_type helper_extend __read_mostly = {
225 .len = sizeof(struct nf_conn_help),
226 .align = __alignof__(struct nf_conn_help),
227 .id = NF_CT_EXT_HELPER,
228 };
229
230 int nf_conntrack_helper_init(void)
231 {
232 int err;
233
234 nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
235 nf_ct_helper_hash = nf_ct_alloc_hashtable(&nf_ct_helper_hsize,
236 &nf_ct_helper_vmalloc, 0);
237 if (!nf_ct_helper_hash)
238 return -ENOMEM;
239
240 err = nf_ct_extend_register(&helper_extend);
241 if (err < 0)
242 goto err1;
243
244 return 0;
245
246 err1:
247 nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
248 nf_ct_helper_hsize);
249 return err;
250 }
251
252 void nf_conntrack_helper_fini(void)
253 {
254 nf_ct_extend_unregister(&helper_extend);
255 nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
256 nf_ct_helper_hsize);
257 }
258
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