1 // SPDX-License-Identifier: GPL-2.0-only
2 /* Helper handling for netfilter. */
4 /* (C) 1999-2001 Paul `Rusty' Russell
5 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
6 * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
7 * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
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>
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>
31 static DEFINE_MUTEX(nf_ct_helper_mutex);
32 struct hlist_head *nf_ct_helper_hash __read_mostly;
33 EXPORT_SYMBOL_GPL(nf_ct_helper_hash);
34 unsigned int nf_ct_helper_hsize __read_mostly;
35 EXPORT_SYMBOL_GPL(nf_ct_helper_hsize);
36 static unsigned int nf_ct_helper_count __read_mostly;
38 static bool nf_ct_auto_assign_helper __read_mostly = false;
39 module_param_named(nf_conntrack_helper, nf_ct_auto_assign_helper, bool, 0644);
40 MODULE_PARM_DESC(nf_conntrack_helper,
41 "Enable automatic conntrack helper assignment (default 0)");
43 static DEFINE_MUTEX(nf_ct_nat_helpers_mutex);
44 static struct list_head nf_ct_nat_helpers __read_mostly;
46 /* Stupid hash, but collision free for the default registrations of the
47 * helpers currently in the kernel. */
48 static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
50 return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
51 (__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
54 static struct nf_conntrack_helper *
55 __nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
57 struct nf_conntrack_helper *helper;
58 struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
61 if (!nf_ct_helper_count)
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))
72 struct nf_conntrack_helper *
73 __nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum)
75 struct nf_conntrack_helper *h;
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))
83 if (h->tuple.src.l3num != NFPROTO_UNSPEC &&
84 h->tuple.src.l3num != l3num)
87 if (h->tuple.dst.protonum == protonum)
93 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find);
95 struct nf_conntrack_helper *
96 nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
98 struct nf_conntrack_helper *h;
102 h = __nf_conntrack_helper_find(name, l3num, protonum);
103 #ifdef CONFIG_MODULES
106 if (request_module("nfct-helper-%s", name) == 0) {
108 h = __nf_conntrack_helper_find(name, l3num, protonum);
114 if (h != NULL && !try_module_get(h->me))
116 if (h != NULL && !refcount_inc_not_zero(&h->refcnt)) {
125 EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);
127 void nf_conntrack_helper_put(struct nf_conntrack_helper *helper)
129 refcount_dec(&helper->refcnt);
130 module_put(helper->me);
132 EXPORT_SYMBOL_GPL(nf_conntrack_helper_put);
134 static struct nf_conntrack_nat_helper *
135 nf_conntrack_nat_helper_find(const char *mod_name)
137 struct nf_conntrack_nat_helper *cur;
140 list_for_each_entry_rcu(cur, &nf_ct_nat_helpers, list) {
141 if (!strcmp(cur->mod_name, mod_name)) {
146 return found ? cur : NULL;
150 nf_nat_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
152 struct nf_conntrack_helper *h;
153 struct nf_conntrack_nat_helper *nat;
154 char mod_name[NF_CT_HELPER_NAME_LEN];
158 h = __nf_conntrack_helper_find(name, l3num, protonum);
164 nat = nf_conntrack_nat_helper_find(h->nat_mod_name);
166 snprintf(mod_name, sizeof(mod_name), "%s", h->nat_mod_name);
168 request_module(mod_name);
171 nat = nf_conntrack_nat_helper_find(mod_name);
178 if (!try_module_get(nat->module))
184 EXPORT_SYMBOL_GPL(nf_nat_helper_try_module_get);
186 void nf_nat_helper_put(struct nf_conntrack_helper *helper)
188 struct nf_conntrack_nat_helper *nat;
190 nat = nf_conntrack_nat_helper_find(helper->nat_mod_name);
191 if (WARN_ON_ONCE(!nat))
194 module_put(nat->module);
196 EXPORT_SYMBOL_GPL(nf_nat_helper_put);
198 struct nf_conn_help *
199 nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
201 struct nf_conn_help *help;
203 help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
205 INIT_HLIST_HEAD(&help->expectations);
207 pr_debug("failed to add helper extension area");
210 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
212 static struct nf_conntrack_helper *
213 nf_ct_lookup_helper(struct nf_conn *ct, struct net *net)
215 if (!net->ct.sysctl_auto_assign_helper) {
216 if (net->ct.auto_assign_helper_warned)
218 if (!__nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple))
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;
228 return __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
231 int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
234 struct nf_conntrack_helper *helper = NULL;
235 struct nf_conn_help *help;
236 struct net *net = nf_ct_net(ct);
238 /* We already got a helper explicitly attached. The function
239 * nf_conntrack_alter_reply - in case NAT is in use - asks for looking
240 * the helper up again. Since now the user is in full control of
241 * making consistent helper configurations, skip this automatic
242 * re-lookup, otherwise we'll lose the helper.
244 if (test_bit(IPS_HELPER_BIT, &ct->status))
248 help = nfct_help(tmpl);
250 helper = help->helper;
251 set_bit(IPS_HELPER_BIT, &ct->status);
255 help = nfct_help(ct);
257 if (helper == NULL) {
258 helper = nf_ct_lookup_helper(ct, net);
259 if (helper == NULL) {
261 RCU_INIT_POINTER(help->helper, NULL);
267 help = nf_ct_helper_ext_add(ct, flags);
271 /* We only allow helper re-assignment of the same sort since
272 * we cannot reallocate the helper extension area.
274 struct nf_conntrack_helper *tmp = rcu_dereference(help->helper);
276 if (tmp && tmp->help != helper->help) {
277 RCU_INIT_POINTER(help->helper, NULL);
282 rcu_assign_pointer(help->helper, helper);
286 EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
288 /* appropriate ct lock protecting must be taken by caller */
289 static int unhelp(struct nf_conn *ct, void *me)
291 struct nf_conn_help *help = nfct_help(ct);
293 if (help && rcu_dereference_raw(help->helper) == me) {
294 nf_conntrack_event(IPCT_HELPER, ct);
295 RCU_INIT_POINTER(help->helper, NULL);
298 /* We are not intended to delete this conntrack. */
302 void nf_ct_helper_destroy(struct nf_conn *ct)
304 struct nf_conn_help *help = nfct_help(ct);
305 struct nf_conntrack_helper *helper;
309 helper = rcu_dereference(help->helper);
310 if (helper && helper->destroy)
316 static LIST_HEAD(nf_ct_helper_expectfn_list);
318 void nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn *n)
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);
324 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_register);
326 void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn *n)
328 spin_lock_bh(&nf_conntrack_expect_lock);
329 list_del_rcu(&n->head);
330 spin_unlock_bh(&nf_conntrack_expect_lock);
332 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_unregister);
334 /* Caller should hold the rcu lock */
335 struct nf_ct_helper_expectfn *
336 nf_ct_helper_expectfn_find_by_name(const char *name)
338 struct nf_ct_helper_expectfn *cur;
341 list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
342 if (!strcmp(cur->name, name)) {
347 return found ? cur : NULL;
349 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name);
351 /* Caller should hold the rcu lock */
352 struct nf_ct_helper_expectfn *
353 nf_ct_helper_expectfn_find_by_symbol(const void *symbol)
355 struct nf_ct_helper_expectfn *cur;
358 list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
359 if (cur->expectfn == symbol) {
364 return found ? cur : NULL;
366 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_symbol);
369 void nf_ct_helper_log(struct sk_buff *skb, const struct nf_conn *ct,
370 const char *fmt, ...)
372 const struct nf_conn_help *help;
373 const struct nf_conntrack_helper *helper;
374 struct va_format vaf;
382 /* Called from the helper function, this call never fails */
383 help = nfct_help(ct);
385 /* rcu_read_lock()ed by nf_hook_thresh */
386 helper = rcu_dereference(help->helper);
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);
393 EXPORT_SYMBOL_GPL(nf_ct_helper_log);
395 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
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;
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);
406 if (me->expect_policy->max_expected > NF_CT_EXPECT_MAX_CNT)
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) {
422 /* avoid unpredictable behaviour for auto_assign_helper */
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,
432 refcount_set(&me->refcnt, 1);
433 hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
434 nf_ct_helper_count++;
436 mutex_unlock(&nf_ct_helper_mutex);
439 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
441 static bool expect_iter_me(struct nf_conntrack_expect *exp, void *data)
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;
447 if (exp->helper == me)
450 this = rcu_dereference_protected(help->helper,
451 lockdep_is_held(&nf_conntrack_expect_lock));
455 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
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);
462 /* Make sure every nothing is still using the helper unless its a
463 * connection in the hash.
467 nf_ct_expect_iterate_destroy(expect_iter_me, NULL);
468 nf_ct_iterate_destroy(unhelp, me);
470 /* Maybe someone has gotten the helper already when unhelp above.
471 * So need to wait it.
475 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
477 void 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,
484 enum ip_conntrack_info ctinfo),
485 int (*from_nlattr)(struct nlattr *attr,
487 struct module *module)
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;
495 helper->from_nlattr = from_nlattr;
497 snprintf(helper->nat_mod_name, sizeof(helper->nat_mod_name),
498 NF_NAT_HELPER_PREFIX "%s", name);
500 if (spec_port == default_port)
501 snprintf(helper->name, sizeof(helper->name), "%s", name);
503 snprintf(helper->name, sizeof(helper->name), "%s-%u", name, id);
505 EXPORT_SYMBOL_GPL(nf_ct_helper_init);
507 int nf_conntrack_helpers_register(struct nf_conntrack_helper *helper,
513 for (i = 0; i < n; i++) {
514 err = nf_conntrack_helper_register(&helper[i]);
522 nf_conntrack_helpers_unregister(helper, i);
525 EXPORT_SYMBOL_GPL(nf_conntrack_helpers_register);
527 void nf_conntrack_helpers_unregister(struct nf_conntrack_helper *helper,
531 nf_conntrack_helper_unregister(&helper[n]);
533 EXPORT_SYMBOL_GPL(nf_conntrack_helpers_unregister);
535 void nf_nat_helper_register(struct nf_conntrack_nat_helper *nat)
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);
541 EXPORT_SYMBOL_GPL(nf_nat_helper_register);
543 void nf_nat_helper_unregister(struct nf_conntrack_nat_helper *nat)
545 mutex_lock(&nf_ct_nat_helpers_mutex);
546 list_del_rcu(&nat->list);
547 mutex_unlock(&nf_ct_nat_helpers_mutex);
549 EXPORT_SYMBOL_GPL(nf_nat_helper_unregister);
551 static 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,
557 void nf_conntrack_helper_pernet_init(struct net *net)
559 net->ct.auto_assign_helper_warned = false;
560 net->ct.sysctl_auto_assign_helper = nf_ct_auto_assign_helper;
563 int nf_conntrack_helper_init(void)
566 nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
568 nf_ct_alloc_hashtable(&nf_ct_helper_hsize, 0);
569 if (!nf_ct_helper_hash)
572 ret = nf_ct_extend_register(&helper_extend);
574 pr_err("nf_ct_helper: Unable to register helper extension.\n");
578 INIT_LIST_HEAD(&nf_ct_nat_helpers);
581 kvfree(nf_ct_helper_hash);
585 void nf_conntrack_helper_fini(void)
587 nf_ct_extend_unregister(&helper_extend);
588 kvfree(nf_ct_helper_hash);