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 struct nf_conntrack_net *cnet = nf_ct_pernet(net);
217 if (!cnet->sysctl_auto_assign_helper) {
218 if (cnet->auto_assign_helper_warned)
220 if (!__nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple))
222 pr_info("nf_conntrack: default automatic helper assignment "
223 "has been turned off for security reasons and CT-based "
224 "firewall rule not found. Use the iptables CT target "
225 "to attach helpers instead.\n");
226 cnet->auto_assign_helper_warned = true;
230 return __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
233 int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
236 struct nf_conntrack_helper *helper = NULL;
237 struct nf_conn_help *help;
238 struct net *net = nf_ct_net(ct);
240 /* We already got a helper explicitly attached. The function
241 * nf_conntrack_alter_reply - in case NAT is in use - asks for looking
242 * the helper up again. Since now the user is in full control of
243 * making consistent helper configurations, skip this automatic
244 * re-lookup, otherwise we'll lose the helper.
246 if (test_bit(IPS_HELPER_BIT, &ct->status))
250 help = nfct_help(tmpl);
252 helper = help->helper;
253 set_bit(IPS_HELPER_BIT, &ct->status);
257 help = nfct_help(ct);
259 if (helper == NULL) {
260 helper = nf_ct_lookup_helper(ct, net);
261 if (helper == NULL) {
263 RCU_INIT_POINTER(help->helper, NULL);
269 help = nf_ct_helper_ext_add(ct, flags);
273 /* We only allow helper re-assignment of the same sort since
274 * we cannot reallocate the helper extension area.
276 struct nf_conntrack_helper *tmp = rcu_dereference(help->helper);
278 if (tmp && tmp->help != helper->help) {
279 RCU_INIT_POINTER(help->helper, NULL);
284 rcu_assign_pointer(help->helper, helper);
288 EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
290 /* appropriate ct lock protecting must be taken by caller */
291 static int unhelp(struct nf_conn *ct, void *me)
293 struct nf_conn_help *help = nfct_help(ct);
295 if (help && rcu_dereference_raw(help->helper) == me) {
296 nf_conntrack_event(IPCT_HELPER, ct);
297 RCU_INIT_POINTER(help->helper, NULL);
300 /* We are not intended to delete this conntrack. */
304 void nf_ct_helper_destroy(struct nf_conn *ct)
306 struct nf_conn_help *help = nfct_help(ct);
307 struct nf_conntrack_helper *helper;
311 helper = rcu_dereference(help->helper);
312 if (helper && helper->destroy)
318 static LIST_HEAD(nf_ct_helper_expectfn_list);
320 void nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn *n)
322 spin_lock_bh(&nf_conntrack_expect_lock);
323 list_add_rcu(&n->head, &nf_ct_helper_expectfn_list);
324 spin_unlock_bh(&nf_conntrack_expect_lock);
326 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_register);
328 void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn *n)
330 spin_lock_bh(&nf_conntrack_expect_lock);
331 list_del_rcu(&n->head);
332 spin_unlock_bh(&nf_conntrack_expect_lock);
334 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_unregister);
336 /* Caller should hold the rcu lock */
337 struct nf_ct_helper_expectfn *
338 nf_ct_helper_expectfn_find_by_name(const char *name)
340 struct nf_ct_helper_expectfn *cur;
343 list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
344 if (!strcmp(cur->name, name)) {
349 return found ? cur : NULL;
351 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name);
353 /* Caller should hold the rcu lock */
354 struct nf_ct_helper_expectfn *
355 nf_ct_helper_expectfn_find_by_symbol(const void *symbol)
357 struct nf_ct_helper_expectfn *cur;
360 list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
361 if (cur->expectfn == symbol) {
366 return found ? cur : NULL;
368 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_symbol);
371 void nf_ct_helper_log(struct sk_buff *skb, const struct nf_conn *ct,
372 const char *fmt, ...)
374 const struct nf_conn_help *help;
375 const struct nf_conntrack_helper *helper;
376 struct va_format vaf;
384 /* Called from the helper function, this call never fails */
385 help = nfct_help(ct);
387 /* rcu_read_lock()ed by nf_hook_thresh */
388 helper = rcu_dereference(help->helper);
390 nf_log_packet(nf_ct_net(ct), nf_ct_l3num(ct), 0, skb, NULL, NULL, NULL,
391 "nf_ct_%s: dropping packet: %pV ", helper->name, &vaf);
395 EXPORT_SYMBOL_GPL(nf_ct_helper_log);
397 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
399 struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
400 unsigned int h = helper_hash(&me->tuple);
401 struct nf_conntrack_helper *cur;
404 BUG_ON(me->expect_policy == NULL);
405 BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
406 BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
408 if (me->expect_policy->max_expected > NF_CT_EXPECT_MAX_CNT)
411 mutex_lock(&nf_ct_helper_mutex);
412 for (i = 0; i < nf_ct_helper_hsize; i++) {
413 hlist_for_each_entry(cur, &nf_ct_helper_hash[i], hnode) {
414 if (!strcmp(cur->name, me->name) &&
415 (cur->tuple.src.l3num == NFPROTO_UNSPEC ||
416 cur->tuple.src.l3num == me->tuple.src.l3num) &&
417 cur->tuple.dst.protonum == me->tuple.dst.protonum) {
424 /* avoid unpredictable behaviour for auto_assign_helper */
425 if (!(me->flags & NF_CT_HELPER_F_USERSPACE)) {
426 hlist_for_each_entry(cur, &nf_ct_helper_hash[h], hnode) {
427 if (nf_ct_tuple_src_mask_cmp(&cur->tuple, &me->tuple,
434 refcount_set(&me->refcnt, 1);
435 hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
436 nf_ct_helper_count++;
438 mutex_unlock(&nf_ct_helper_mutex);
441 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
443 static bool expect_iter_me(struct nf_conntrack_expect *exp, void *data)
445 struct nf_conn_help *help = nfct_help(exp->master);
446 const struct nf_conntrack_helper *me = data;
447 const struct nf_conntrack_helper *this;
449 if (exp->helper == me)
452 this = rcu_dereference_protected(help->helper,
453 lockdep_is_held(&nf_conntrack_expect_lock));
457 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
459 mutex_lock(&nf_ct_helper_mutex);
460 hlist_del_rcu(&me->hnode);
461 nf_ct_helper_count--;
462 mutex_unlock(&nf_ct_helper_mutex);
464 /* Make sure every nothing is still using the helper unless its a
465 * connection in the hash.
469 nf_ct_expect_iterate_destroy(expect_iter_me, NULL);
470 nf_ct_iterate_destroy(unhelp, me);
472 /* Maybe someone has gotten the helper already when unhelp above.
473 * So need to wait it.
477 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
479 void nf_ct_helper_init(struct nf_conntrack_helper *helper,
480 u16 l3num, u16 protonum, const char *name,
481 u16 default_port, u16 spec_port, u32 id,
482 const struct nf_conntrack_expect_policy *exp_pol,
483 u32 expect_class_max,
484 int (*help)(struct sk_buff *skb, unsigned int protoff,
486 enum ip_conntrack_info ctinfo),
487 int (*from_nlattr)(struct nlattr *attr,
489 struct module *module)
491 helper->tuple.src.l3num = l3num;
492 helper->tuple.dst.protonum = protonum;
493 helper->tuple.src.u.all = htons(spec_port);
494 helper->expect_policy = exp_pol;
495 helper->expect_class_max = expect_class_max;
497 helper->from_nlattr = from_nlattr;
499 snprintf(helper->nat_mod_name, sizeof(helper->nat_mod_name),
500 NF_NAT_HELPER_PREFIX "%s", name);
502 if (spec_port == default_port)
503 snprintf(helper->name, sizeof(helper->name), "%s", name);
505 snprintf(helper->name, sizeof(helper->name), "%s-%u", name, id);
507 EXPORT_SYMBOL_GPL(nf_ct_helper_init);
509 int nf_conntrack_helpers_register(struct nf_conntrack_helper *helper,
515 for (i = 0; i < n; i++) {
516 err = nf_conntrack_helper_register(&helper[i]);
524 nf_conntrack_helpers_unregister(helper, i);
527 EXPORT_SYMBOL_GPL(nf_conntrack_helpers_register);
529 void nf_conntrack_helpers_unregister(struct nf_conntrack_helper *helper,
533 nf_conntrack_helper_unregister(&helper[n]);
535 EXPORT_SYMBOL_GPL(nf_conntrack_helpers_unregister);
537 void nf_nat_helper_register(struct nf_conntrack_nat_helper *nat)
539 mutex_lock(&nf_ct_nat_helpers_mutex);
540 list_add_rcu(&nat->list, &nf_ct_nat_helpers);
541 mutex_unlock(&nf_ct_nat_helpers_mutex);
543 EXPORT_SYMBOL_GPL(nf_nat_helper_register);
545 void nf_nat_helper_unregister(struct nf_conntrack_nat_helper *nat)
547 mutex_lock(&nf_ct_nat_helpers_mutex);
548 list_del_rcu(&nat->list);
549 mutex_unlock(&nf_ct_nat_helpers_mutex);
551 EXPORT_SYMBOL_GPL(nf_nat_helper_unregister);
553 static const struct nf_ct_ext_type helper_extend = {
554 .len = sizeof(struct nf_conn_help),
555 .align = __alignof__(struct nf_conn_help),
556 .id = NF_CT_EXT_HELPER,
559 void nf_conntrack_helper_pernet_init(struct net *net)
561 struct nf_conntrack_net *cnet = nf_ct_pernet(net);
563 cnet->sysctl_auto_assign_helper = nf_ct_auto_assign_helper;
566 int nf_conntrack_helper_init(void)
569 nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
571 nf_ct_alloc_hashtable(&nf_ct_helper_hsize, 0);
572 if (!nf_ct_helper_hash)
575 ret = nf_ct_extend_register(&helper_extend);
577 pr_err("nf_ct_helper: Unable to register helper extension.\n");
581 INIT_LIST_HEAD(&nf_ct_nat_helpers);
584 kvfree(nf_ct_helper_hash);
588 void nf_conntrack_helper_fini(void)
590 nf_ct_extend_unregister(&helper_extend);
591 kvfree(nf_ct_helper_hash);