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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 = true; |
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 1)"); |
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 | /* appropiate 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 | int ret = 0; |
365 | struct nf_conntrack_helper *cur; |
366 | unsigned int h = helper_hash(&me->tuple); |
367 | |
368 | BUG_ON(me->expect_policy == NULL); |
369 | BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES); |
370 | BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1); |
371 | |
372 | mutex_lock(&nf_ct_helper_mutex); |
373 | hlist_for_each_entry(cur, &nf_ct_helper_hash[h], hnode) { |
374 | if (strncmp(cur->name, me->name, NF_CT_HELPER_NAME_LEN) == 0 && |
375 | cur->tuple.src.l3num == me->tuple.src.l3num && |
376 | cur->tuple.dst.protonum == me->tuple.dst.protonum) { |
377 | ret = -EEXIST; |
378 | goto out; |
379 | } |
380 | } |
381 | hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]); |
382 | nf_ct_helper_count++; |
383 | out: |
384 | mutex_unlock(&nf_ct_helper_mutex); |
385 | return ret; |
386 | } |
387 | EXPORT_SYMBOL_GPL(nf_conntrack_helper_register); |
388 | |
389 | static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me, |
390 | struct net *net) |
391 | { |
392 | struct nf_conntrack_tuple_hash *h; |
393 | struct nf_conntrack_expect *exp; |
394 | const struct hlist_node *next; |
395 | const struct hlist_nulls_node *nn; |
396 | unsigned int i; |
397 | int cpu; |
398 | |
399 | /* Get rid of expectations */ |
400 | spin_lock_bh(&nf_conntrack_expect_lock); |
401 | for (i = 0; i < nf_ct_expect_hsize; i++) { |
402 | hlist_for_each_entry_safe(exp, next, |
403 | &net->ct.expect_hash[i], hnode) { |
404 | struct nf_conn_help *help = nfct_help(exp->master); |
405 | if ((rcu_dereference_protected( |
406 | help->helper, |
407 | lockdep_is_held(&nf_conntrack_expect_lock) |
408 | ) == me || exp->helper == me) && |
409 | del_timer(&exp->timeout)) { |
410 | nf_ct_unlink_expect(exp); |
411 | nf_ct_expect_put(exp); |
412 | } |
413 | } |
414 | } |
415 | spin_unlock_bh(&nf_conntrack_expect_lock); |
416 | |
417 | /* Get rid of expecteds, set helpers to NULL. */ |
418 | for_each_possible_cpu(cpu) { |
419 | struct ct_pcpu *pcpu = per_cpu_ptr(net->ct.pcpu_lists, cpu); |
420 | |
421 | spin_lock_bh(&pcpu->lock); |
422 | hlist_nulls_for_each_entry(h, nn, &pcpu->unconfirmed, hnnode) |
423 | unhelp(h, me); |
424 | spin_unlock_bh(&pcpu->lock); |
425 | } |
426 | local_bh_disable(); |
427 | for (i = 0; i < net->ct.htable_size; i++) { |
428 | spin_lock(&nf_conntrack_locks[i % CONNTRACK_LOCKS]); |
429 | if (i < net->ct.htable_size) { |
430 | hlist_nulls_for_each_entry(h, nn, &net->ct.hash[i], hnnode) |
431 | unhelp(h, me); |
432 | } |
433 | spin_unlock(&nf_conntrack_locks[i % CONNTRACK_LOCKS]); |
434 | } |
435 | local_bh_enable(); |
436 | } |
437 | |
438 | void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me) |
439 | { |
440 | struct net *net; |
441 | |
442 | mutex_lock(&nf_ct_helper_mutex); |
443 | hlist_del_rcu(&me->hnode); |
444 | nf_ct_helper_count--; |
445 | mutex_unlock(&nf_ct_helper_mutex); |
446 | |
447 | /* Make sure every nothing is still using the helper unless its a |
448 | * connection in the hash. |
449 | */ |
450 | synchronize_rcu(); |
451 | |
452 | rtnl_lock(); |
453 | for_each_net(net) |
454 | __nf_conntrack_helper_unregister(me, net); |
455 | rtnl_unlock(); |
456 | } |
457 | EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister); |
458 | |
459 | static struct nf_ct_ext_type helper_extend __read_mostly = { |
460 | .len = sizeof(struct nf_conn_help), |
461 | .align = __alignof__(struct nf_conn_help), |
462 | .id = NF_CT_EXT_HELPER, |
463 | }; |
464 | |
465 | int nf_conntrack_helper_pernet_init(struct net *net) |
466 | { |
467 | net->ct.auto_assign_helper_warned = false; |
468 | net->ct.sysctl_auto_assign_helper = nf_ct_auto_assign_helper; |
469 | return nf_conntrack_helper_init_sysctl(net); |
470 | } |
471 | |
472 | void nf_conntrack_helper_pernet_fini(struct net *net) |
473 | { |
474 | nf_conntrack_helper_fini_sysctl(net); |
475 | } |
476 | |
477 | int nf_conntrack_helper_init(void) |
478 | { |
479 | int ret; |
480 | nf_ct_helper_hsize = 1; /* gets rounded up to use one page */ |
481 | nf_ct_helper_hash = |
482 | nf_ct_alloc_hashtable(&nf_ct_helper_hsize, 0); |
483 | if (!nf_ct_helper_hash) |
484 | return -ENOMEM; |
485 | |
486 | ret = nf_ct_extend_register(&helper_extend); |
487 | if (ret < 0) { |
488 | pr_err("nf_ct_helper: Unable to register helper extension.\n"); |
489 | goto out_extend; |
490 | } |
491 | |
492 | return 0; |
493 | out_extend: |
494 | nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize); |
495 | return ret; |
496 | } |
497 | |
498 | void nf_conntrack_helper_fini(void) |
499 | { |
500 | nf_ct_extend_unregister(&helper_extend); |
501 | nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize); |
502 | } |
503 |
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