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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_core.h>
25#include <net/netfilter/nf_conntrack_ecache.h>
26#include <net/netfilter/nf_conntrack_extend.h>
27#include <net/netfilter/nf_conntrack_helper.h>
28#include <net/netfilter/nf_conntrack_l4proto.h>
29#include <net/netfilter/nf_log.h>
30
31static DEFINE_MUTEX(nf_ct_helper_mutex);
32struct hlist_head *nf_ct_helper_hash __read_mostly;
33EXPORT_SYMBOL_GPL(nf_ct_helper_hash);
34unsigned int nf_ct_helper_hsize __read_mostly;
35EXPORT_SYMBOL_GPL(nf_ct_helper_hsize);
36static unsigned int nf_ct_helper_count __read_mostly;
37
38static bool nf_ct_auto_assign_helper __read_mostly = false;
39module_param_named(nf_conntrack_helper, nf_ct_auto_assign_helper, bool, 0644);
40MODULE_PARM_DESC(nf_conntrack_helper,
41 "Enable automatic conntrack helper assignment (default 0)");
42
43static DEFINE_MUTEX(nf_ct_nat_helpers_mutex);
44static struct list_head nf_ct_nat_helpers __read_mostly;
45
46
47
48static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
49{
50 return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
51 (__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
52}
53
54static struct nf_conntrack_helper *
55__nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
56{
57 struct nf_conntrack_helper *helper;
58 struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
59 unsigned int h;
60
61 if (!nf_ct_helper_count)
62 return NULL;
63
64 h = helper_hash(tuple);
65 hlist_for_each_entry_rcu(helper, &nf_ct_helper_hash[h], hnode) {
66 if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
67 return helper;
68 }
69 return NULL;
70}
71
72struct nf_conntrack_helper *
73__nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum)
74{
75 struct nf_conntrack_helper *h;
76 unsigned int i;
77
78 for (i = 0; i < nf_ct_helper_hsize; i++) {
79 hlist_for_each_entry_rcu(h, &nf_ct_helper_hash[i], hnode) {
80 if (strcmp(h->name, name))
81 continue;
82
83 if (h->tuple.src.l3num != NFPROTO_UNSPEC &&
84 h->tuple.src.l3num != l3num)
85 continue;
86
87 if (h->tuple.dst.protonum == protonum)
88 return h;
89 }
90 }
91 return NULL;
92}
93EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find);
94
95struct nf_conntrack_helper *
96nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
97{
98 struct nf_conntrack_helper *h;
99
100 rcu_read_lock();
101
102 h = __nf_conntrack_helper_find(name, l3num, protonum);
103#ifdef CONFIG_MODULES
104 if (h == NULL) {
105 rcu_read_unlock();
106 if (request_module("nfct-helper-%s", name) == 0) {
107 rcu_read_lock();
108 h = __nf_conntrack_helper_find(name, l3num, protonum);
109 } else {
110 return h;
111 }
112 }
113#endif
114 if (h != NULL && !try_module_get(h->me))
115 h = NULL;
116 if (h != NULL && !refcount_inc_not_zero(&h->refcnt)) {
117 module_put(h->me);
118 h = NULL;
119 }
120
121 rcu_read_unlock();
122
123 return h;
124}
125EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);
126
127void nf_conntrack_helper_put(struct nf_conntrack_helper *helper)
128{
129 refcount_dec(&helper->refcnt);
130 module_put(helper->me);
131}
132EXPORT_SYMBOL_GPL(nf_conntrack_helper_put);
133
134static struct nf_conntrack_nat_helper *
135nf_conntrack_nat_helper_find(const char *mod_name)
136{
137 struct nf_conntrack_nat_helper *cur;
138 bool found = false;
139
140 list_for_each_entry_rcu(cur, &nf_ct_nat_helpers, list) {
141 if (!strcmp(cur->mod_name, mod_name)) {
142 found = true;
143 break;
144 }
145 }
146 return found ? cur : NULL;
147}
148
149int
150nf_nat_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
151{
152 struct nf_conntrack_helper *h;
153 struct nf_conntrack_nat_helper *nat;
154 char mod_name[NF_CT_HELPER_NAME_LEN];
155 int ret = 0;
156
157 rcu_read_lock();
158 h = __nf_conntrack_helper_find(name, l3num, protonum);
159 if (!h) {
160 rcu_read_unlock();
161 return -ENOENT;
162 }
163
164 nat = nf_conntrack_nat_helper_find(h->nat_mod_name);
165 if (!nat) {
166 snprintf(mod_name, sizeof(mod_name), "%s", h->nat_mod_name);
167 rcu_read_unlock();
168 request_module(mod_name);
169
170 rcu_read_lock();
171 nat = nf_conntrack_nat_helper_find(mod_name);
172 if (!nat) {
173 rcu_read_unlock();
174 return -ENOENT;
175 }
176 }
177
178 if (!try_module_get(nat->module))
179 ret = -ENOENT;
180
181 rcu_read_unlock();
182 return ret;
183}
184EXPORT_SYMBOL_GPL(nf_nat_helper_try_module_get);
185
186void nf_nat_helper_put(struct nf_conntrack_helper *helper)
187{
188 struct nf_conntrack_nat_helper *nat;
189
190 nat = nf_conntrack_nat_helper_find(helper->nat_mod_name);
191 if (WARN_ON_ONCE(!nat))
192 return;
193
194 module_put(nat->module);
195}
196EXPORT_SYMBOL_GPL(nf_nat_helper_put);
197
198struct nf_conn_help *
199nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
200{
201 struct nf_conn_help *help;
202
203 help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
204 if (help)
205 INIT_HLIST_HEAD(&help->expectations);
206 else
207 pr_debug("failed to add helper extension area");
208 return help;
209}
210EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
211
212static struct nf_conntrack_helper *
213nf_ct_lookup_helper(struct nf_conn *ct, struct net *net)
214{
215 if (!net->ct.sysctl_auto_assign_helper) {
216 if (net->ct.auto_assign_helper_warned)
217 return NULL;
218 if (!__nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple))
219 return NULL;
220 pr_info("nf_conntrack: default automatic helper assignment "
221 "has been turned off for security reasons and CT-based "
222 " firewall rule not found. Use the iptables CT target "
223 "to attach helpers instead.\n");
224 net->ct.auto_assign_helper_warned = 1;
225 return NULL;
226 }
227
228 return __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
229}
230
231
232int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
233 gfp_t flags)
234{
235 struct nf_conntrack_helper *helper = NULL;
236 struct nf_conn_help *help;
237 struct net *net = nf_ct_net(ct);
238
239
240
241
242
243
244
245 if (test_bit(IPS_HELPER_BIT, &ct->status))
246 return 0;
247
248 if (tmpl != NULL) {
249 help = nfct_help(tmpl);
250 if (help != NULL) {
251 helper = help->helper;
252 set_bit(IPS_HELPER_BIT, &ct->status);
253 }
254 }
255
256 help = nfct_help(ct);
257
258 if (helper == NULL) {
259 helper = nf_ct_lookup_helper(ct, net);
260 if (helper == NULL) {
261 if (help)
262 RCU_INIT_POINTER(help->helper, NULL);
263 return 0;
264 }
265 }
266
267 if (help == NULL) {
268 help = nf_ct_helper_ext_add(ct, flags);
269 if (help == NULL)
270 return -ENOMEM;
271 } else {
272
273
274
275 struct nf_conntrack_helper *tmp = rcu_dereference(help->helper);
276
277 if (tmp && tmp->help != helper->help) {
278 RCU_INIT_POINTER(help->helper, NULL);
279 return 0;
280 }
281 }
282
283 rcu_assign_pointer(help->helper, helper);
284
285 return 0;
286}
287EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
288
289
290static int unhelp(struct nf_conn *ct, void *me)
291{
292 struct nf_conn_help *help = nfct_help(ct);
293
294 if (help && rcu_dereference_raw(help->helper) == me) {
295 nf_conntrack_event(IPCT_HELPER, ct);
296 RCU_INIT_POINTER(help->helper, NULL);
297 }
298
299
300 return 0;
301}
302
303void nf_ct_helper_destroy(struct nf_conn *ct)
304{
305 struct nf_conn_help *help = nfct_help(ct);
306 struct nf_conntrack_helper *helper;
307
308 if (help) {
309 rcu_read_lock();
310 helper = rcu_dereference(help->helper);
311 if (helper && helper->destroy)
312 helper->destroy(ct);
313 rcu_read_unlock();
314 }
315}
316
317static LIST_HEAD(nf_ct_helper_expectfn_list);
318
319void nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn *n)
320{
321 spin_lock_bh(&nf_conntrack_expect_lock);
322 list_add_rcu(&n->head, &nf_ct_helper_expectfn_list);
323 spin_unlock_bh(&nf_conntrack_expect_lock);
324}
325EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_register);
326
327void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn *n)
328{
329 spin_lock_bh(&nf_conntrack_expect_lock);
330 list_del_rcu(&n->head);
331 spin_unlock_bh(&nf_conntrack_expect_lock);
332}
333EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_unregister);
334
335
336struct nf_ct_helper_expectfn *
337nf_ct_helper_expectfn_find_by_name(const char *name)
338{
339 struct nf_ct_helper_expectfn *cur;
340 bool found = false;
341
342 list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
343 if (!strcmp(cur->name, name)) {
344 found = true;
345 break;
346 }
347 }
348 return found ? cur : NULL;
349}
350EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name);
351
352
353struct nf_ct_helper_expectfn *
354nf_ct_helper_expectfn_find_by_symbol(const void *symbol)
355{
356 struct nf_ct_helper_expectfn *cur;
357 bool found = false;
358
359 list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
360 if (cur->expectfn == symbol) {
361 found = true;
362 break;
363 }
364 }
365 return found ? cur : NULL;
366}
367EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_symbol);
368
369__printf(3, 4)
370void nf_ct_helper_log(struct sk_buff *skb, const struct nf_conn *ct,
371 const char *fmt, ...)
372{
373 const struct nf_conn_help *help;
374 const struct nf_conntrack_helper *helper;
375 struct va_format vaf;
376 va_list args;
377
378 va_start(args, fmt);
379
380 vaf.fmt = fmt;
381 vaf.va = &args;
382
383
384 help = nfct_help(ct);
385
386
387 helper = rcu_dereference(help->helper);
388
389 nf_log_packet(nf_ct_net(ct), nf_ct_l3num(ct), 0, skb, NULL, NULL, NULL,
390 "nf_ct_%s: dropping packet: %pV ", helper->name, &vaf);
391
392 va_end(args);
393}
394EXPORT_SYMBOL_GPL(nf_ct_helper_log);
395
396int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
397{
398 struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
399 unsigned int h = helper_hash(&me->tuple);
400 struct nf_conntrack_helper *cur;
401 int ret = 0, i;
402
403 BUG_ON(me->expect_policy == NULL);
404 BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
405 BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
406
407 if (me->expect_policy->max_expected > NF_CT_EXPECT_MAX_CNT)
408 return -EINVAL;
409
410 mutex_lock(&nf_ct_helper_mutex);
411 for (i = 0; i < nf_ct_helper_hsize; i++) {
412 hlist_for_each_entry(cur, &nf_ct_helper_hash[i], hnode) {
413 if (!strcmp(cur->name, me->name) &&
414 (cur->tuple.src.l3num == NFPROTO_UNSPEC ||
415 cur->tuple.src.l3num == me->tuple.src.l3num) &&
416 cur->tuple.dst.protonum == me->tuple.dst.protonum) {
417 ret = -EEXIST;
418 goto out;
419 }
420 }
421 }
422
423
424 if (!(me->flags & NF_CT_HELPER_F_USERSPACE)) {
425 hlist_for_each_entry(cur, &nf_ct_helper_hash[h], hnode) {
426 if (nf_ct_tuple_src_mask_cmp(&cur->tuple, &me->tuple,
427 &mask)) {
428 ret = -EEXIST;
429 goto out;
430 }
431 }
432 }
433 refcount_set(&me->refcnt, 1);
434 hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
435 nf_ct_helper_count++;
436out:
437 mutex_unlock(&nf_ct_helper_mutex);
438 return ret;
439}
440EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
441
442static bool expect_iter_me(struct nf_conntrack_expect *exp, void *data)
443{
444 struct nf_conn_help *help = nfct_help(exp->master);
445 const struct nf_conntrack_helper *me = data;
446 const struct nf_conntrack_helper *this;
447
448 if (exp->helper == me)
449 return true;
450
451 this = rcu_dereference_protected(help->helper,
452 lockdep_is_held(&nf_conntrack_expect_lock));
453 return this == me;
454}
455
456void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
457{
458 mutex_lock(&nf_ct_helper_mutex);
459 hlist_del_rcu(&me->hnode);
460 nf_ct_helper_count--;
461 mutex_unlock(&nf_ct_helper_mutex);
462
463
464
465
466 synchronize_rcu();
467
468 nf_ct_expect_iterate_destroy(expect_iter_me, NULL);
469 nf_ct_iterate_destroy(unhelp, me);
470
471
472
473
474 synchronize_rcu();
475}
476EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
477
478void nf_ct_helper_init(struct nf_conntrack_helper *helper,
479 u16 l3num, u16 protonum, const char *name,
480 u16 default_port, u16 spec_port, u32 id,
481 const struct nf_conntrack_expect_policy *exp_pol,
482 u32 expect_class_max,
483 int (*help)(struct sk_buff *skb, unsigned int protoff,
484 struct nf_conn *ct,
485 enum ip_conntrack_info ctinfo),
486 int (*from_nlattr)(struct nlattr *attr,
487 struct nf_conn *ct),
488 struct module *module)
489{
490 helper->tuple.src.l3num = l3num;
491 helper->tuple.dst.protonum = protonum;
492 helper->tuple.src.u.all = htons(spec_port);
493 helper->expect_policy = exp_pol;
494 helper->expect_class_max = expect_class_max;
495 helper->help = help;
496 helper->from_nlattr = from_nlattr;
497 helper->me = module;
498 snprintf(helper->nat_mod_name, sizeof(helper->nat_mod_name),
499 NF_NAT_HELPER_PREFIX "%s", name);
500
501 if (spec_port == default_port)
502 snprintf(helper->name, sizeof(helper->name), "%s", name);
503 else
504 snprintf(helper->name, sizeof(helper->name), "%s-%u", name, id);
505}
506EXPORT_SYMBOL_GPL(nf_ct_helper_init);
507
508int nf_conntrack_helpers_register(struct nf_conntrack_helper *helper,
509 unsigned int n)
510{
511 unsigned int i;
512 int err = 0;
513
514 for (i = 0; i < n; i++) {
515 err = nf_conntrack_helper_register(&helper[i]);
516 if (err < 0)
517 goto err;
518 }
519
520 return err;
521err:
522 if (i > 0)
523 nf_conntrack_helpers_unregister(helper, i);
524 return err;
525}
526EXPORT_SYMBOL_GPL(nf_conntrack_helpers_register);
527
528void nf_conntrack_helpers_unregister(struct nf_conntrack_helper *helper,
529 unsigned int n)
530{
531 while (n-- > 0)
532 nf_conntrack_helper_unregister(&helper[n]);
533}
534EXPORT_SYMBOL_GPL(nf_conntrack_helpers_unregister);
535
536void nf_nat_helper_register(struct nf_conntrack_nat_helper *nat)
537{
538 mutex_lock(&nf_ct_nat_helpers_mutex);
539 list_add_rcu(&nat->list, &nf_ct_nat_helpers);
540 mutex_unlock(&nf_ct_nat_helpers_mutex);
541}
542EXPORT_SYMBOL_GPL(nf_nat_helper_register);
543
544void nf_nat_helper_unregister(struct nf_conntrack_nat_helper *nat)
545{
546 mutex_lock(&nf_ct_nat_helpers_mutex);
547 list_del_rcu(&nat->list);
548 mutex_unlock(&nf_ct_nat_helpers_mutex);
549}
550EXPORT_SYMBOL_GPL(nf_nat_helper_unregister);
551
552static const struct nf_ct_ext_type helper_extend = {
553 .len = sizeof(struct nf_conn_help),
554 .align = __alignof__(struct nf_conn_help),
555 .id = NF_CT_EXT_HELPER,
556};
557
558void nf_conntrack_helper_pernet_init(struct net *net)
559{
560 net->ct.auto_assign_helper_warned = false;
561 net->ct.sysctl_auto_assign_helper = nf_ct_auto_assign_helper;
562}
563
564int nf_conntrack_helper_init(void)
565{
566 int ret;
567 nf_ct_helper_hsize = 1;
568 nf_ct_helper_hash =
569 nf_ct_alloc_hashtable(&nf_ct_helper_hsize, 0);
570 if (!nf_ct_helper_hash)
571 return -ENOMEM;
572
573 ret = nf_ct_extend_register(&helper_extend);
574 if (ret < 0) {
575 pr_err("nf_ct_helper: Unable to register helper extension.\n");
576 goto out_extend;
577 }
578
579 INIT_LIST_HEAD(&nf_ct_nat_helpers);
580 return 0;
581out_extend:
582 kvfree(nf_ct_helper_hash);
583 return ret;
584}
585
586void nf_conntrack_helper_fini(void)
587{
588 nf_ct_extend_unregister(&helper_extend);
589 kvfree(nf_ct_helper_hash);
590}
591
