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 * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
11 */
12
13 #include <linux/types.h>
14 #include <linux/netfilter.h>
15 #include <linux/module.h>
16 #include <linux/skbuff.h>
17 #include <linux/vmalloc.h>
18 #include <linux/stddef.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 #include <net/netfilter/nf_log.h>
33
34 static DEFINE_MUTEX(nf_ct_helper_mutex);
35 struct hlist_head *nf_ct_helper_hash __read_mostly;
36 EXPORT_SYMBOL_GPL(nf_ct_helper_hash);
37 unsigned int nf_ct_helper_hsize __read_mostly;
38 EXPORT_SYMBOL_GPL(nf_ct_helper_hsize);
39 static unsigned int nf_ct_helper_count __read_mostly;
40
41 static bool nf_ct_auto_assign_helper __read_mostly = false;
42 module_param_named(nf_conntrack_helper, nf_ct_auto_assign_helper, bool, 0644);
43 MODULE_PARM_DESC(nf_conntrack_helper,
44 "Enable automatic conntrack helper assignment (default 0)");
45
46 #ifdef CONFIG_SYSCTL
47 static struct ctl_table helper_sysctl_table[] = {
48 {
49 .procname = "nf_conntrack_helper",
50 .data = &init_net.ct.sysctl_auto_assign_helper,
51 .maxlen = sizeof(unsigned int),
52 .mode = 0644,
53 .proc_handler = proc_dointvec,
54 },
55 {}
56 };
57
58 static int nf_conntrack_helper_init_sysctl(struct net *net)
59 {
60 struct ctl_table *table;
61
62 table = kmemdup(helper_sysctl_table, sizeof(helper_sysctl_table),
63 GFP_KERNEL);
64 if (!table)
65 goto out;
66
67 table[0].data = &net->ct.sysctl_auto_assign_helper;
68
69 /* Don't export sysctls to unprivileged users */
70 if (net->user_ns != &init_user_ns)
71 table[0].procname = NULL;
72
73 net->ct.helper_sysctl_header =
74 register_net_sysctl(net, "net/netfilter", table);
75
76 if (!net->ct.helper_sysctl_header) {
77 pr_err("nf_conntrack_helper: can't register to sysctl.\n");
78 goto out_register;
79 }
80 return 0;
81
82 out_register:
83 kfree(table);
84 out:
85 return -ENOMEM;
86 }
87
88 static void nf_conntrack_helper_fini_sysctl(struct net *net)
89 {
90 struct ctl_table *table;
91
92 table = net->ct.helper_sysctl_header->ctl_table_arg;
93 unregister_net_sysctl_table(net->ct.helper_sysctl_header);
94 kfree(table);
95 }
96 #else
97 static int nf_conntrack_helper_init_sysctl(struct net *net)
98 {
99 return 0;
100 }
101
102 static void nf_conntrack_helper_fini_sysctl(struct net *net)
103 {
104 }
105 #endif /* CONFIG_SYSCTL */
106
107 /* Stupid hash, but collision free for the default registrations of the
108 * helpers currently in the kernel. */
109 static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
110 {
111 return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
112 (__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
113 }
114
115 static struct nf_conntrack_helper *
116 __nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
117 {
118 struct nf_conntrack_helper *helper;
119 struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
120 unsigned int h;
121
122 if (!nf_ct_helper_count)
123 return NULL;
124
125 h = helper_hash(tuple);
126 hlist_for_each_entry_rcu(helper, &nf_ct_helper_hash[h], hnode) {
127 if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
128 return helper;
129 }
130 return NULL;
131 }
132
133 struct nf_conntrack_helper *
134 __nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum)
135 {
136 struct nf_conntrack_helper *h;
137 unsigned int i;
138
139 for (i = 0; i < nf_ct_helper_hsize; i++) {
140 hlist_for_each_entry_rcu(h, &nf_ct_helper_hash[i], hnode) {
141 if (!strcmp(h->name, name) &&
142 h->tuple.src.l3num == l3num &&
143 h->tuple.dst.protonum == protonum)
144 return h;
145 }
146 }
147 return NULL;
148 }
149 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find);
150
151 struct nf_conntrack_helper *
152 nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
153 {
154 struct nf_conntrack_helper *h;
155
156 h = __nf_conntrack_helper_find(name, l3num, protonum);
157 #ifdef CONFIG_MODULES
158 if (h == NULL) {
159 if (request_module("nfct-helper-%s", name) == 0)
160 h = __nf_conntrack_helper_find(name, l3num, protonum);
161 }
162 #endif
163 if (h != NULL && !try_module_get(h->me))
164 h = NULL;
165
166 return h;
167 }
168 EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);
169
170 struct nf_conn_help *
171 nf_ct_helper_ext_add(struct nf_conn *ct,
172 struct nf_conntrack_helper *helper, gfp_t gfp)
173 {
174 struct nf_conn_help *help;
175
176 help = nf_ct_ext_add_length(ct, NF_CT_EXT_HELPER,
177 helper->data_len, gfp);
178 if (help)
179 INIT_HLIST_HEAD(&help->expectations);
180 else
181 pr_debug("failed to add helper extension area");
182 return help;
183 }
184 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
185
186 int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
187 gfp_t flags)
188 {
189 struct nf_conntrack_helper *helper = NULL;
190 struct nf_conn_help *help;
191 struct net *net = nf_ct_net(ct);
192 int ret = 0;
193
194 /* We already got a helper explicitly attached. The function
195 * nf_conntrack_alter_reply - in case NAT is in use - asks for looking
196 * the helper up again. Since now the user is in full control of
197 * making consistent helper configurations, skip this automatic
198 * re-lookup, otherwise we'll lose the helper.
199 */
200 if (test_bit(IPS_HELPER_BIT, &ct->status))
201 return 0;
202
203 if (tmpl != NULL) {
204 help = nfct_help(tmpl);
205 if (help != NULL) {
206 helper = help->helper;
207 set_bit(IPS_HELPER_BIT, &ct->status);
208 }
209 }
210
211 help = nfct_help(ct);
212 if (net->ct.sysctl_auto_assign_helper && helper == NULL) {
213 helper = __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
214 if (unlikely(!net->ct.auto_assign_helper_warned && helper)) {
215 pr_info("nf_conntrack: automatic helper "
216 "assignment is deprecated and it will "
217 "be removed soon. Use the iptables CT target "
218 "to attach helpers instead.\n");
219 net->ct.auto_assign_helper_warned = true;
220 }
221 }
222
223 if (helper == NULL) {
224 if (help)
225 RCU_INIT_POINTER(help->helper, NULL);
226 goto out;
227 }
228
229 if (help == NULL) {
230 help = nf_ct_helper_ext_add(ct, helper, flags);
231 if (help == NULL) {
232 ret = -ENOMEM;
233 goto out;
234 }
235 } else {
236 /* We only allow helper re-assignment of the same sort since
237 * we cannot reallocate the helper extension area.
238 */
239 struct nf_conntrack_helper *tmp = rcu_dereference(help->helper);
240
241 if (tmp && tmp->help != helper->help) {
242 RCU_INIT_POINTER(help->helper, NULL);
243 goto out;
244 }
245 }
246
247 rcu_assign_pointer(help->helper, helper);
248 out:
249 return ret;
250 }
251 EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
252
253 /* appropriate ct lock protecting must be taken by caller */
254 static inline int unhelp(struct nf_conntrack_tuple_hash *i,
255 const struct nf_conntrack_helper *me)
256 {
257 struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
258 struct nf_conn_help *help = nfct_help(ct);
259
260 if (help && rcu_dereference_raw(help->helper) == me) {
261 nf_conntrack_event(IPCT_HELPER, ct);
262 RCU_INIT_POINTER(help->helper, NULL);
263 }
264 return 0;
265 }
266
267 void nf_ct_helper_destroy(struct nf_conn *ct)
268 {
269 struct nf_conn_help *help = nfct_help(ct);
270 struct nf_conntrack_helper *helper;
271
272 if (help) {
273 rcu_read_lock();
274 helper = rcu_dereference(help->helper);
275 if (helper && helper->destroy)
276 helper->destroy(ct);
277 rcu_read_unlock();
278 }
279 }
280
281 static LIST_HEAD(nf_ct_helper_expectfn_list);
282
283 void nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn *n)
284 {
285 spin_lock_bh(&nf_conntrack_expect_lock);
286 list_add_rcu(&n->head, &nf_ct_helper_expectfn_list);
287 spin_unlock_bh(&nf_conntrack_expect_lock);
288 }
289 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_register);
290
291 void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn *n)
292 {
293 spin_lock_bh(&nf_conntrack_expect_lock);
294 list_del_rcu(&n->head);
295 spin_unlock_bh(&nf_conntrack_expect_lock);
296 }
297 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_unregister);
298
299 struct nf_ct_helper_expectfn *
300 nf_ct_helper_expectfn_find_by_name(const char *name)
301 {
302 struct nf_ct_helper_expectfn *cur;
303 bool found = false;
304
305 rcu_read_lock();
306 list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
307 if (!strcmp(cur->name, name)) {
308 found = true;
309 break;
310 }
311 }
312 rcu_read_unlock();
313 return found ? cur : NULL;
314 }
315 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name);
316
317 struct nf_ct_helper_expectfn *
318 nf_ct_helper_expectfn_find_by_symbol(const void *symbol)
319 {
320 struct nf_ct_helper_expectfn *cur;
321 bool found = false;
322
323 rcu_read_lock();
324 list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
325 if (cur->expectfn == symbol) {
326 found = true;
327 break;
328 }
329 }
330 rcu_read_unlock();
331 return found ? cur : NULL;
332 }
333 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_symbol);
334
335 __printf(3, 4)
336 void nf_ct_helper_log(struct sk_buff *skb, const struct nf_conn *ct,
337 const char *fmt, ...)
338 {
339 const struct nf_conn_help *help;
340 const struct nf_conntrack_helper *helper;
341 struct va_format vaf;
342 va_list args;
343
344 va_start(args, fmt);
345
346 vaf.fmt = fmt;
347 vaf.va = &args;
348
349 /* Called from the helper function, this call never fails */
350 help = nfct_help(ct);
351
352 /* rcu_read_lock()ed by nf_hook_slow */
353 helper = rcu_dereference(help->helper);
354
355 nf_log_packet(nf_ct_net(ct), nf_ct_l3num(ct), 0, skb, NULL, NULL, NULL,
356 "nf_ct_%s: dropping packet: %pV ", helper->name, &vaf);
357
358 va_end(args);
359 }
360 EXPORT_SYMBOL_GPL(nf_ct_helper_log);
361
362 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
363 {
364 struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
365 unsigned int h = helper_hash(&me->tuple);
366 struct nf_conntrack_helper *cur;
367 int ret = 0;
368
369 BUG_ON(me->expect_policy == NULL);
370 BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
371 BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
372
373 mutex_lock(&nf_ct_helper_mutex);
374 hlist_for_each_entry(cur, &nf_ct_helper_hash[h], hnode) {
375 if (nf_ct_tuple_src_mask_cmp(&cur->tuple, &me->tuple, &mask)) {
376 ret = -EEXIST;
377 goto out;
378 }
379 }
380 hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
381 nf_ct_helper_count++;
382 out:
383 mutex_unlock(&nf_ct_helper_mutex);
384 return ret;
385 }
386 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
387
388 static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
389 struct net *net)
390 {
391 struct nf_conntrack_tuple_hash *h;
392 struct nf_conntrack_expect *exp;
393 const struct hlist_node *next;
394 const struct hlist_nulls_node *nn;
395 unsigned int i;
396 int cpu;
397
398 /* Get rid of expectations */
399 spin_lock_bh(&nf_conntrack_expect_lock);
400 for (i = 0; i < nf_ct_expect_hsize; i++) {
401 hlist_for_each_entry_safe(exp, next,
402 &nf_ct_expect_hash[i], hnode) {
403 struct nf_conn_help *help = nfct_help(exp->master);
404 if ((rcu_dereference_protected(
405 help->helper,
406 lockdep_is_held(&nf_conntrack_expect_lock)
407 ) == me || exp->helper == me) &&
408 del_timer(&exp->timeout)) {
409 nf_ct_unlink_expect(exp);
410 nf_ct_expect_put(exp);
411 }
412 }
413 }
414 spin_unlock_bh(&nf_conntrack_expect_lock);
415
416 /* Get rid of expecteds, set helpers to NULL. */
417 for_each_possible_cpu(cpu) {
418 struct ct_pcpu *pcpu = per_cpu_ptr(net->ct.pcpu_lists, cpu);
419
420 spin_lock_bh(&pcpu->lock);
421 hlist_nulls_for_each_entry(h, nn, &pcpu->unconfirmed, hnnode)
422 unhelp(h, me);
423 spin_unlock_bh(&pcpu->lock);
424 }
425 local_bh_disable();
426 for (i = 0; i < nf_conntrack_htable_size; i++) {
427 nf_conntrack_lock(&nf_conntrack_locks[i % CONNTRACK_LOCKS]);
428 if (i < nf_conntrack_htable_size) {
429 hlist_nulls_for_each_entry(h, nn, &nf_conntrack_hash[i], hnnode)
430 unhelp(h, me);
431 }
432 spin_unlock(&nf_conntrack_locks[i % CONNTRACK_LOCKS]);
433 }
434 local_bh_enable();
435 }
436
437 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
438 {
439 struct net *net;
440
441 mutex_lock(&nf_ct_helper_mutex);
442 hlist_del_rcu(&me->hnode);
443 nf_ct_helper_count--;
444 mutex_unlock(&nf_ct_helper_mutex);
445
446 /* Make sure every nothing is still using the helper unless its a
447 * connection in the hash.
448 */
449 synchronize_rcu();
450
451 rtnl_lock();
452 for_each_net(net)
453 __nf_conntrack_helper_unregister(me, net);
454 rtnl_unlock();
455 }
456 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
457
458 static struct nf_ct_ext_type helper_extend __read_mostly = {
459 .len = sizeof(struct nf_conn_help),
460 .align = __alignof__(struct nf_conn_help),
461 .id = NF_CT_EXT_HELPER,
462 };
463
464 int nf_conntrack_helper_pernet_init(struct net *net)
465 {
466 net->ct.auto_assign_helper_warned = false;
467 net->ct.sysctl_auto_assign_helper = nf_ct_auto_assign_helper;
468 return nf_conntrack_helper_init_sysctl(net);
469 }
470
471 void nf_conntrack_helper_pernet_fini(struct net *net)
472 {
473 nf_conntrack_helper_fini_sysctl(net);
474 }
475
476 int nf_conntrack_helper_init(void)
477 {
478 int ret;
479 nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
480 nf_ct_helper_hash =
481 nf_ct_alloc_hashtable(&nf_ct_helper_hsize, 0);
482 if (!nf_ct_helper_hash)
483 return -ENOMEM;
484
485 ret = nf_ct_extend_register(&helper_extend);
486 if (ret < 0) {
487 pr_err("nf_ct_helper: Unable to register helper extension.\n");
488 goto out_extend;
489 }
490
491 return 0;
492 out_extend:
493 nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize);
494 return ret;
495 }
496
497 void nf_conntrack_helper_fini(void)
498 {
499 nf_ct_extend_unregister(&helper_extend);
500 nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize);
501 }
502
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