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10#include <linux/types.h>
11#include <linux/netfilter.h>
12#include <linux/module.h>
13#include <linux/skbuff.h>
14#include <linux/vmalloc.h>
15#include <linux/stddef.h>
16#include <linux/random.h>
17#include <linux/err.h>
18#include <linux/kernel.h>
19#include <linux/netdevice.h>
20#include <linux/rculist.h>
21#include <linux/rtnetlink.h>
22
23#include <net/netfilter/nf_conntrack.h>
24#include <net/netfilter/nf_conntrack_l4proto.h>
25#include <net/netfilter/nf_conntrack_helper.h>
26#include <net/netfilter/nf_conntrack_core.h>
27#include <net/netfilter/nf_conntrack_extend.h>
28#include <net/netfilter/nf_log.h>
29
30static DEFINE_MUTEX(nf_ct_helper_mutex);
31struct hlist_head *nf_ct_helper_hash __read_mostly;
32EXPORT_SYMBOL_GPL(nf_ct_helper_hash);
33unsigned int nf_ct_helper_hsize __read_mostly;
34EXPORT_SYMBOL_GPL(nf_ct_helper_hsize);
35static unsigned int nf_ct_helper_count __read_mostly;
36
37static bool nf_ct_auto_assign_helper __read_mostly = false;
38module_param_named(nf_conntrack_helper, nf_ct_auto_assign_helper, bool, 0644);
39MODULE_PARM_DESC(nf_conntrack_helper,
40 "Enable automatic conntrack helper assignment (default 0)");
41
42static DEFINE_MUTEX(nf_ct_nat_helpers_mutex);
43static struct list_head nf_ct_nat_helpers __read_mostly;
44
45
46
47static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
48{
49 return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
50 (__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
51}
52
53static struct nf_conntrack_helper *
54__nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
55{
56 struct nf_conntrack_helper *helper;
57 struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
58 unsigned int h;
59
60 if (!nf_ct_helper_count)
61 return NULL;
62
63 h = helper_hash(tuple);
64 hlist_for_each_entry_rcu(helper, &nf_ct_helper_hash[h], hnode) {
65 if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
66 return helper;
67 }
68 return NULL;
69}
70
71struct nf_conntrack_helper *
72__nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum)
73{
74 struct nf_conntrack_helper *h;
75 unsigned int i;
76
77 for (i = 0; i < nf_ct_helper_hsize; i++) {
78 hlist_for_each_entry_rcu(h, &nf_ct_helper_hash[i], hnode) {
79 if (strcmp(h->name, name))
80 continue;
81
82 if (h->tuple.src.l3num != NFPROTO_UNSPEC &&
83 h->tuple.src.l3num != l3num)
84 continue;
85
86 if (h->tuple.dst.protonum == protonum)
87 return h;
88 }
89 }
90 return NULL;
91}
92EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find);
93
94struct nf_conntrack_helper *
95nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
96{
97 struct nf_conntrack_helper *h;
98
99 rcu_read_lock();
100
101 h = __nf_conntrack_helper_find(name, l3num, protonum);
102#ifdef CONFIG_MODULES
103 if (h == NULL) {
104 rcu_read_unlock();
105 if (request_module("nfct-helper-%s", name) == 0) {
106 rcu_read_lock();
107 h = __nf_conntrack_helper_find(name, l3num, protonum);
108 } else {
109 return h;
110 }
111 }
112#endif
113 if (h != NULL && !try_module_get(h->me))
114 h = NULL;
115 if (h != NULL && !refcount_inc_not_zero(&h->refcnt)) {
116 module_put(h->me);
117 h = NULL;
118 }
119
120 rcu_read_unlock();
121
122 return h;
123}
124EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);
125
126void nf_conntrack_helper_put(struct nf_conntrack_helper *helper)
127{
128 refcount_dec(&helper->refcnt);
129 module_put(helper->me);
130}
131EXPORT_SYMBOL_GPL(nf_conntrack_helper_put);
132
133static struct nf_conntrack_nat_helper *
134nf_conntrack_nat_helper_find(const char *mod_name)
135{
136 struct nf_conntrack_nat_helper *cur;
137 bool found = false;
138
139 list_for_each_entry_rcu(cur, &nf_ct_nat_helpers, list) {
140 if (!strcmp(cur->mod_name, mod_name)) {
141 found = true;
142 break;
143 }
144 }
145 return found ? cur : NULL;
146}
147
148int
149nf_nat_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
150{
151 struct nf_conntrack_helper *h;
152 struct nf_conntrack_nat_helper *nat;
153 char mod_name[NF_CT_HELPER_NAME_LEN];
154 int ret = 0;
155
156 rcu_read_lock();
157 h = __nf_conntrack_helper_find(name, l3num, protonum);
158 if (!h) {
159 rcu_read_unlock();
160 return -ENOENT;
161 }
162
163 nat = nf_conntrack_nat_helper_find(h->nat_mod_name);
164 if (!nat) {
165 snprintf(mod_name, sizeof(mod_name), "%s", h->nat_mod_name);
166 rcu_read_unlock();
167 request_module(mod_name);
168
169 rcu_read_lock();
170 nat = nf_conntrack_nat_helper_find(mod_name);
171 if (!nat) {
172 rcu_read_unlock();
173 return -ENOENT;
174 }
175 }
176
177 if (!try_module_get(nat->module))
178 ret = -ENOENT;
179
180 rcu_read_unlock();
181 return ret;
182}
183EXPORT_SYMBOL_GPL(nf_nat_helper_try_module_get);
184
185void nf_nat_helper_put(struct nf_conntrack_helper *helper)
186{
187 struct nf_conntrack_nat_helper *nat;
188
189 nat = nf_conntrack_nat_helper_find(helper->nat_mod_name);
190 if (WARN_ON_ONCE(!nat))
191 return;
192
193 module_put(nat->module);
194}
195EXPORT_SYMBOL_GPL(nf_nat_helper_put);
196
197struct nf_conn_help *
198nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
199{
200 struct nf_conn_help *help;
201
202 help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
203 if (help)
204 INIT_HLIST_HEAD(&help->expectations);
205 else
206 pr_debug("failed to add helper extension area");
207 return help;
208}
209EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
210
211static struct nf_conntrack_helper *
212nf_ct_lookup_helper(struct nf_conn *ct, struct net *net)
213{
214 if (!net->ct.sysctl_auto_assign_helper) {
215 if (net->ct.auto_assign_helper_warned)
216 return NULL;
217 if (!__nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple))
218 return NULL;
219 pr_info("nf_conntrack: default automatic helper assignment "
220 "has been turned off for security reasons and CT-based "
221 " firewall rule not found. Use the iptables CT target "
222 "to attach helpers instead.\n");
223 net->ct.auto_assign_helper_warned = 1;
224 return NULL;
225 }
226
227 return __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
228}
229
230
231int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
232 gfp_t flags)
233{
234 struct nf_conntrack_helper *helper = NULL;
235 struct nf_conn_help *help;
236 struct net *net = nf_ct_net(ct);
237
238
239
240
241
242
243
244 if (test_bit(IPS_HELPER_BIT, &ct->status))
245 return 0;
246
247 if (tmpl != NULL) {
248 help = nfct_help(tmpl);
249 if (help != NULL) {
250 helper = help->helper;
251 set_bit(IPS_HELPER_BIT, &ct->status);
252 }
253 }
254
255 help = nfct_help(ct);
256
257 if (helper == NULL) {
258 helper = nf_ct_lookup_helper(ct, net);
259 if (helper == NULL) {
260 if (help)
261 RCU_INIT_POINTER(help->helper, NULL);
262 return 0;
263 }
264 }
265
266 if (help == NULL) {
267 help = nf_ct_helper_ext_add(ct, flags);
268 if (help == NULL)
269 return -ENOMEM;
270 } else {
271
272
273
274 struct nf_conntrack_helper *tmp = rcu_dereference(help->helper);
275
276 if (tmp && tmp->help != helper->help) {
277 RCU_INIT_POINTER(help->helper, NULL);
278 return 0;
279 }
280 }
281
282 rcu_assign_pointer(help->helper, helper);
283
284 return 0;
285}
286EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
287
288
289static int unhelp(struct nf_conn *ct, void *me)
290{
291 struct nf_conn_help *help = nfct_help(ct);
292
293 if (help && rcu_dereference_raw(help->helper) == me) {
294 nf_conntrack_event(IPCT_HELPER, ct);
295 RCU_INIT_POINTER(help->helper, NULL);
296 }
297
298
299 return 0;
300}
301
302void nf_ct_helper_destroy(struct nf_conn *ct)
303{
304 struct nf_conn_help *help = nfct_help(ct);
305 struct nf_conntrack_helper *helper;
306
307 if (help) {
308 rcu_read_lock();
309 helper = rcu_dereference(help->helper);
310 if (helper && helper->destroy)
311 helper->destroy(ct);
312 rcu_read_unlock();
313 }
314}
315
316static LIST_HEAD(nf_ct_helper_expectfn_list);
317
318void nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn *n)
319{
320 spin_lock_bh(&nf_conntrack_expect_lock);
321 list_add_rcu(&n->head, &nf_ct_helper_expectfn_list);
322 spin_unlock_bh(&nf_conntrack_expect_lock);
323}
324EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_register);
325
326void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn *n)
327{
328 spin_lock_bh(&nf_conntrack_expect_lock);
329 list_del_rcu(&n->head);
330 spin_unlock_bh(&nf_conntrack_expect_lock);
331}
332EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_unregister);
333
334
335struct nf_ct_helper_expectfn *
336nf_ct_helper_expectfn_find_by_name(const char *name)
337{
338 struct nf_ct_helper_expectfn *cur;
339 bool found = false;
340
341 list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
342 if (!strcmp(cur->name, name)) {
343 found = true;
344 break;
345 }
346 }
347 return found ? cur : NULL;
348}
349EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name);
350
351
352struct nf_ct_helper_expectfn *
353nf_ct_helper_expectfn_find_by_symbol(const void *symbol)
354{
355 struct nf_ct_helper_expectfn *cur;
356 bool found = false;
357
358 list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
359 if (cur->expectfn == symbol) {
360 found = true;
361 break;
362 }
363 }
364 return found ? cur : NULL;
365}
366EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_symbol);
367
368__printf(3, 4)
369void nf_ct_helper_log(struct sk_buff *skb, const struct nf_conn *ct,
370 const char *fmt, ...)
371{
372 const struct nf_conn_help *help;
373 const struct nf_conntrack_helper *helper;
374 struct va_format vaf;
375 va_list args;
376
377 va_start(args, fmt);
378
379 vaf.fmt = fmt;
380 vaf.va = &args;
381
382
383 help = nfct_help(ct);
384
385
386 helper = rcu_dereference(help->helper);
387
388 nf_log_packet(nf_ct_net(ct), nf_ct_l3num(ct), 0, skb, NULL, NULL, NULL,
389 "nf_ct_%s: dropping packet: %pV ", helper->name, &vaf);
390
391 va_end(args);
392}
393EXPORT_SYMBOL_GPL(nf_ct_helper_log);
394
395int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
396{
397 struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
398 unsigned int h = helper_hash(&me->tuple);
399 struct nf_conntrack_helper *cur;
400 int ret = 0, i;
401
402 BUG_ON(me->expect_policy == NULL);
403 BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
404 BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
405
406 if (me->expect_policy->max_expected > NF_CT_EXPECT_MAX_CNT)
407 return -EINVAL;
408
409 mutex_lock(&nf_ct_helper_mutex);
410 for (i = 0; i < nf_ct_helper_hsize; i++) {
411 hlist_for_each_entry(cur, &nf_ct_helper_hash[i], hnode) {
412 if (!strcmp(cur->name, me->name) &&
413 (cur->tuple.src.l3num == NFPROTO_UNSPEC ||
414 cur->tuple.src.l3num == me->tuple.src.l3num) &&
415 cur->tuple.dst.protonum == me->tuple.dst.protonum) {
416 ret = -EEXIST;
417 goto out;
418 }
419 }
420 }
421
422
423 if (!(me->flags & NF_CT_HELPER_F_USERSPACE)) {
424 hlist_for_each_entry(cur, &nf_ct_helper_hash[h], hnode) {
425 if (nf_ct_tuple_src_mask_cmp(&cur->tuple, &me->tuple,
426 &mask)) {
427 ret = -EEXIST;
428 goto out;
429 }
430 }
431 }
432 refcount_set(&me->refcnt, 1);
433 hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
434 nf_ct_helper_count++;
435out:
436 mutex_unlock(&nf_ct_helper_mutex);
437 return ret;
438}
439EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
440
441static bool expect_iter_me(struct nf_conntrack_expect *exp, void *data)
442{
443 struct nf_conn_help *help = nfct_help(exp->master);
444 const struct nf_conntrack_helper *me = data;
445 const struct nf_conntrack_helper *this;
446
447 if (exp->helper == me)
448 return true;
449
450 this = rcu_dereference_protected(help->helper,
451 lockdep_is_held(&nf_conntrack_expect_lock));
452 return this == me;
453}
454
455void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
456{
457 mutex_lock(&nf_ct_helper_mutex);
458 hlist_del_rcu(&me->hnode);
459 nf_ct_helper_count--;
460 mutex_unlock(&nf_ct_helper_mutex);
461
462
463
464
465 synchronize_rcu();
466
467 nf_ct_expect_iterate_destroy(expect_iter_me, NULL);
468 nf_ct_iterate_destroy(unhelp, me);
469
470
471
472
473 synchronize_rcu();
474}
475EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
476
477void nf_ct_helper_init(struct nf_conntrack_helper *helper,
478 u16 l3num, u16 protonum, const char *name,
479 u16 default_port, u16 spec_port, u32 id,
480 const struct nf_conntrack_expect_policy *exp_pol,
481 u32 expect_class_max,
482 int (*help)(struct sk_buff *skb, unsigned int protoff,
483 struct nf_conn *ct,
484 enum ip_conntrack_info ctinfo),
485 int (*from_nlattr)(struct nlattr *attr,
486 struct nf_conn *ct),
487 struct module *module)
488{
489 helper->tuple.src.l3num = l3num;
490 helper->tuple.dst.protonum = protonum;
491 helper->tuple.src.u.all = htons(spec_port);
492 helper->expect_policy = exp_pol;
493 helper->expect_class_max = expect_class_max;
494 helper->help = help;
495 helper->from_nlattr = from_nlattr;
496 helper->me = module;
497 snprintf(helper->nat_mod_name, sizeof(helper->nat_mod_name),
498 NF_NAT_HELPER_PREFIX "%s", name);
499
500 if (spec_port == default_port)
501 snprintf(helper->name, sizeof(helper->name), "%s", name);
502 else
503 snprintf(helper->name, sizeof(helper->name), "%s-%u", name, id);
504}
505EXPORT_SYMBOL_GPL(nf_ct_helper_init);
506
507int nf_conntrack_helpers_register(struct nf_conntrack_helper *helper,
508 unsigned int n)
509{
510 unsigned int i;
511 int err = 0;
512
513 for (i = 0; i < n; i++) {
514 err = nf_conntrack_helper_register(&helper[i]);
515 if (err < 0)
516 goto err;
517 }
518
519 return err;
520err:
521 if (i > 0)
522 nf_conntrack_helpers_unregister(helper, i);
523 return err;
524}
525EXPORT_SYMBOL_GPL(nf_conntrack_helpers_register);
526
527void nf_conntrack_helpers_unregister(struct nf_conntrack_helper *helper,
528 unsigned int n)
529{
530 while (n-- > 0)
531 nf_conntrack_helper_unregister(&helper[n]);
532}
533EXPORT_SYMBOL_GPL(nf_conntrack_helpers_unregister);
534
535void nf_nat_helper_register(struct nf_conntrack_nat_helper *nat)
536{
537 mutex_lock(&nf_ct_nat_helpers_mutex);
538 list_add_rcu(&nat->list, &nf_ct_nat_helpers);
539 mutex_unlock(&nf_ct_nat_helpers_mutex);
540}
541EXPORT_SYMBOL_GPL(nf_nat_helper_register);
542
543void nf_nat_helper_unregister(struct nf_conntrack_nat_helper *nat)
544{
545 mutex_lock(&nf_ct_nat_helpers_mutex);
546 list_del_rcu(&nat->list);
547 mutex_unlock(&nf_ct_nat_helpers_mutex);
548}
549EXPORT_SYMBOL_GPL(nf_nat_helper_unregister);
550
551static const struct nf_ct_ext_type helper_extend = {
552 .len = sizeof(struct nf_conn_help),
553 .align = __alignof__(struct nf_conn_help),
554 .id = NF_CT_EXT_HELPER,
555};
556
557void nf_conntrack_helper_pernet_init(struct net *net)
558{
559 net->ct.auto_assign_helper_warned = false;
560 net->ct.sysctl_auto_assign_helper = nf_ct_auto_assign_helper;
561}
562
563int nf_conntrack_helper_init(void)
564{
565 int ret;
566 nf_ct_helper_hsize = 1;
567 nf_ct_helper_hash =
568 nf_ct_alloc_hashtable(&nf_ct_helper_hsize, 0);
569 if (!nf_ct_helper_hash)
570 return -ENOMEM;
571
572 ret = nf_ct_extend_register(&helper_extend);
573 if (ret < 0) {
574 pr_err("nf_ct_helper: Unable to register helper extension.\n");
575 goto out_extend;
576 }
577
578 INIT_LIST_HEAD(&nf_ct_nat_helpers);
579 return 0;
580out_extend:
581 kvfree(nf_ct_helper_hash);
582 return ret;
583}
584
585void nf_conntrack_helper_fini(void)
586{
587 nf_ct_extend_unregister(&helper_extend);
588 kvfree(nf_ct_helper_hash);
589}
590
