1 /* Helper handling for netfilter. */
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>
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.
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>
26 #include <net/netfilter/nf_conntrack.h>
27 #include <net/netfilter/nf_conntrack_l4proto.h>
28 #include <net/netfilter/nf_conntrack_helper.h>
29 #include <net/netfilter/nf_conntrack_core.h>
30 #include <net/netfilter/nf_conntrack_extend.h>
31 #include <net/netfilter/nf_log.h>
33 static DEFINE_MUTEX(nf_ct_helper_mutex);
34 struct hlist_head *nf_ct_helper_hash __read_mostly;
35 EXPORT_SYMBOL_GPL(nf_ct_helper_hash);
36 unsigned int nf_ct_helper_hsize __read_mostly;
37 EXPORT_SYMBOL_GPL(nf_ct_helper_hsize);
38 static unsigned int nf_ct_helper_count __read_mostly;
40 static bool nf_ct_auto_assign_helper __read_mostly = false;
41 module_param_named(nf_conntrack_helper, nf_ct_auto_assign_helper, bool, 0644);
42 MODULE_PARM_DESC(nf_conntrack_helper,
43 "Enable automatic conntrack helper assignment (default 0)");
45 static DEFINE_MUTEX(nf_ct_nat_helpers_mutex);
46 static struct list_head nf_ct_nat_helpers __read_mostly;
48 /* Stupid hash, but collision free for the default registrations of the
49 * helpers currently in the kernel. */
50 static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
52 return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
53 (__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
56 static struct nf_conntrack_helper *
57 __nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
59 struct nf_conntrack_helper *helper;
60 struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
63 if (!nf_ct_helper_count)
66 h = helper_hash(tuple);
67 hlist_for_each_entry_rcu(helper, &nf_ct_helper_hash[h], hnode) {
68 if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
74 struct nf_conntrack_helper *
75 __nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum)
77 struct nf_conntrack_helper *h;
80 for (i = 0; i < nf_ct_helper_hsize; i++) {
81 hlist_for_each_entry_rcu(h, &nf_ct_helper_hash[i], hnode) {
82 if (strcmp(h->name, name))
85 if (h->tuple.src.l3num != NFPROTO_UNSPEC &&
86 h->tuple.src.l3num != l3num)
89 if (h->tuple.dst.protonum == protonum)
95 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find);
97 struct nf_conntrack_helper *
98 nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
100 struct nf_conntrack_helper *h;
104 h = __nf_conntrack_helper_find(name, l3num, protonum);
105 #ifdef CONFIG_MODULES
108 if (request_module("nfct-helper-%s", name) == 0) {
110 h = __nf_conntrack_helper_find(name, l3num, protonum);
116 if (h != NULL && !try_module_get(h->me))
118 if (h != NULL && !refcount_inc_not_zero(&h->refcnt)) {
127 EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);
129 void nf_conntrack_helper_put(struct nf_conntrack_helper *helper)
131 refcount_dec(&helper->refcnt);
132 module_put(helper->me);
134 EXPORT_SYMBOL_GPL(nf_conntrack_helper_put);
136 static struct nf_conntrack_nat_helper *
137 nf_conntrack_nat_helper_find(const char *mod_name)
139 struct nf_conntrack_nat_helper *cur;
142 list_for_each_entry_rcu(cur, &nf_ct_nat_helpers, list) {
143 if (!strcmp(cur->mod_name, mod_name)) {
148 return found ? cur : NULL;
152 nf_nat_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
154 struct nf_conntrack_helper *h;
155 struct nf_conntrack_nat_helper *nat;
156 char mod_name[NF_CT_HELPER_NAME_LEN];
160 h = __nf_conntrack_helper_find(name, l3num, protonum);
166 nat = nf_conntrack_nat_helper_find(h->nat_mod_name);
168 snprintf(mod_name, sizeof(mod_name), "%s", h->nat_mod_name);
170 request_module(mod_name);
173 nat = nf_conntrack_nat_helper_find(mod_name);
180 if (!try_module_get(nat->module))
186 EXPORT_SYMBOL_GPL(nf_nat_helper_try_module_get);
188 void nf_nat_helper_put(struct nf_conntrack_helper *helper)
190 struct nf_conntrack_nat_helper *nat;
192 nat = nf_conntrack_nat_helper_find(helper->nat_mod_name);
193 if (WARN_ON_ONCE(!nat))
196 module_put(nat->module);
198 EXPORT_SYMBOL_GPL(nf_nat_helper_put);
200 struct nf_conn_help *
201 nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
203 struct nf_conn_help *help;
205 help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
207 INIT_HLIST_HEAD(&help->expectations);
209 pr_debug("failed to add helper extension area");
212 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
214 static struct nf_conntrack_helper *
215 nf_ct_lookup_helper(struct nf_conn *ct, struct net *net)
217 if (!net->ct.sysctl_auto_assign_helper) {
218 if (net->ct.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 net->ct.auto_assign_helper_warned = 1;
230 return __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
234 int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
237 struct nf_conntrack_helper *helper = NULL;
238 struct nf_conn_help *help;
239 struct net *net = nf_ct_net(ct);
241 /* We already got a helper explicitly attached. The function
242 * nf_conntrack_alter_reply - in case NAT is in use - asks for looking
243 * the helper up again. Since now the user is in full control of
244 * making consistent helper configurations, skip this automatic
245 * re-lookup, otherwise we'll lose the helper.
247 if (test_bit(IPS_HELPER_BIT, &ct->status))
251 help = nfct_help(tmpl);
253 helper = help->helper;
254 set_bit(IPS_HELPER_BIT, &ct->status);
258 help = nfct_help(ct);
260 if (helper == NULL) {
261 helper = nf_ct_lookup_helper(ct, net);
262 if (helper == NULL) {
264 RCU_INIT_POINTER(help->helper, NULL);
270 help = nf_ct_helper_ext_add(ct, flags);
274 /* We only allow helper re-assignment of the same sort since
275 * we cannot reallocate the helper extension area.
277 struct nf_conntrack_helper *tmp = rcu_dereference(help->helper);
279 if (tmp && tmp->help != helper->help) {
280 RCU_INIT_POINTER(help->helper, NULL);
285 rcu_assign_pointer(help->helper, helper);
289 EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
291 /* appropriate ct lock protecting must be taken by caller */
292 static int unhelp(struct nf_conn *ct, void *me)
294 struct nf_conn_help *help = nfct_help(ct);
296 if (help && rcu_dereference_raw(help->helper) == me) {
297 nf_conntrack_event(IPCT_HELPER, ct);
298 RCU_INIT_POINTER(help->helper, NULL);
301 /* We are not intended to delete this conntrack. */
305 void nf_ct_helper_destroy(struct nf_conn *ct)
307 struct nf_conn_help *help = nfct_help(ct);
308 struct nf_conntrack_helper *helper;
312 helper = rcu_dereference(help->helper);
313 if (helper && helper->destroy)
319 static LIST_HEAD(nf_ct_helper_expectfn_list);
321 void nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn *n)
323 spin_lock_bh(&nf_conntrack_expect_lock);
324 list_add_rcu(&n->head, &nf_ct_helper_expectfn_list);
325 spin_unlock_bh(&nf_conntrack_expect_lock);
327 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_register);
329 void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn *n)
331 spin_lock_bh(&nf_conntrack_expect_lock);
332 list_del_rcu(&n->head);
333 spin_unlock_bh(&nf_conntrack_expect_lock);
335 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_unregister);
337 /* Caller should hold the rcu lock */
338 struct nf_ct_helper_expectfn *
339 nf_ct_helper_expectfn_find_by_name(const char *name)
341 struct nf_ct_helper_expectfn *cur;
344 list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
345 if (!strcmp(cur->name, name)) {
350 return found ? cur : NULL;
352 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name);
354 /* Caller should hold the rcu lock */
355 struct nf_ct_helper_expectfn *
356 nf_ct_helper_expectfn_find_by_symbol(const void *symbol)
358 struct nf_ct_helper_expectfn *cur;
361 list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
362 if (cur->expectfn == symbol) {
367 return found ? cur : NULL;
369 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_symbol);
372 void nf_ct_helper_log(struct sk_buff *skb, const struct nf_conn *ct,
373 const char *fmt, ...)
375 const struct nf_conn_help *help;
376 const struct nf_conntrack_helper *helper;
377 struct va_format vaf;
385 /* Called from the helper function, this call never fails */
386 help = nfct_help(ct);
388 /* rcu_read_lock()ed by nf_hook_thresh */
389 helper = rcu_dereference(help->helper);
391 nf_log_packet(nf_ct_net(ct), nf_ct_l3num(ct), 0, skb, NULL, NULL, NULL,
392 "nf_ct_%s: dropping packet: %pV ", helper->name, &vaf);
396 EXPORT_SYMBOL_GPL(nf_ct_helper_log);
398 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
400 struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
401 unsigned int h = helper_hash(&me->tuple);
402 struct nf_conntrack_helper *cur;
405 BUG_ON(me->expect_policy == NULL);
406 BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
407 BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
409 if (me->expect_policy->max_expected > NF_CT_EXPECT_MAX_CNT)
412 mutex_lock(&nf_ct_helper_mutex);
413 for (i = 0; i < nf_ct_helper_hsize; i++) {
414 hlist_for_each_entry(cur, &nf_ct_helper_hash[i], hnode) {
415 if (!strcmp(cur->name, me->name) &&
416 (cur->tuple.src.l3num == NFPROTO_UNSPEC ||
417 cur->tuple.src.l3num == me->tuple.src.l3num) &&
418 cur->tuple.dst.protonum == me->tuple.dst.protonum) {
425 /* avoid unpredictable behaviour for auto_assign_helper */
426 if (!(me->flags & NF_CT_HELPER_F_USERSPACE)) {
427 hlist_for_each_entry(cur, &nf_ct_helper_hash[h], hnode) {
428 if (nf_ct_tuple_src_mask_cmp(&cur->tuple, &me->tuple,
435 refcount_set(&me->refcnt, 1);
436 hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
437 nf_ct_helper_count++;
439 mutex_unlock(&nf_ct_helper_mutex);
442 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
444 static bool expect_iter_me(struct nf_conntrack_expect *exp, void *data)
446 struct nf_conn_help *help = nfct_help(exp->master);
447 const struct nf_conntrack_helper *me = data;
448 const struct nf_conntrack_helper *this;
450 if (exp->helper == me)
453 this = rcu_dereference_protected(help->helper,
454 lockdep_is_held(&nf_conntrack_expect_lock));
458 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
460 mutex_lock(&nf_ct_helper_mutex);
461 hlist_del_rcu(&me->hnode);
462 nf_ct_helper_count--;
463 mutex_unlock(&nf_ct_helper_mutex);
465 /* Make sure every nothing is still using the helper unless its a
466 * connection in the hash.
470 nf_ct_expect_iterate_destroy(expect_iter_me, NULL);
471 nf_ct_iterate_destroy(unhelp, me);
473 /* Maybe someone has gotten the helper already when unhelp above.
474 * So need to wait it.
478 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
480 void nf_ct_helper_init(struct nf_conntrack_helper *helper,
481 u16 l3num, u16 protonum, const char *name,
482 u16 default_port, u16 spec_port, u32 id,
483 const struct nf_conntrack_expect_policy *exp_pol,
484 u32 expect_class_max,
485 int (*help)(struct sk_buff *skb, unsigned int protoff,
487 enum ip_conntrack_info ctinfo),
488 int (*from_nlattr)(struct nlattr *attr,
490 struct module *module)
492 helper->tuple.src.l3num = l3num;
493 helper->tuple.dst.protonum = protonum;
494 helper->tuple.src.u.all = htons(spec_port);
495 helper->expect_policy = exp_pol;
496 helper->expect_class_max = expect_class_max;
498 helper->from_nlattr = from_nlattr;
500 snprintf(helper->nat_mod_name, sizeof(helper->nat_mod_name),
501 NF_NAT_HELPER_PREFIX "%s", name);
503 if (spec_port == default_port)
504 snprintf(helper->name, sizeof(helper->name), "%s", name);
506 snprintf(helper->name, sizeof(helper->name), "%s-%u", name, id);
508 EXPORT_SYMBOL_GPL(nf_ct_helper_init);
510 int nf_conntrack_helpers_register(struct nf_conntrack_helper *helper,
516 for (i = 0; i < n; i++) {
517 err = nf_conntrack_helper_register(&helper[i]);
525 nf_conntrack_helpers_unregister(helper, i);
528 EXPORT_SYMBOL_GPL(nf_conntrack_helpers_register);
530 void nf_conntrack_helpers_unregister(struct nf_conntrack_helper *helper,
534 nf_conntrack_helper_unregister(&helper[n]);
536 EXPORT_SYMBOL_GPL(nf_conntrack_helpers_unregister);
538 void nf_nat_helper_register(struct nf_conntrack_nat_helper *nat)
540 mutex_lock(&nf_ct_nat_helpers_mutex);
541 list_add_rcu(&nat->list, &nf_ct_nat_helpers);
542 mutex_unlock(&nf_ct_nat_helpers_mutex);
544 EXPORT_SYMBOL_GPL(nf_nat_helper_register);
546 void nf_nat_helper_unregister(struct nf_conntrack_nat_helper *nat)
548 mutex_lock(&nf_ct_nat_helpers_mutex);
549 list_del_rcu(&nat->list);
550 mutex_unlock(&nf_ct_nat_helpers_mutex);
552 EXPORT_SYMBOL_GPL(nf_nat_helper_unregister);
554 static const struct nf_ct_ext_type helper_extend = {
555 .len = sizeof(struct nf_conn_help),
556 .align = __alignof__(struct nf_conn_help),
557 .id = NF_CT_EXT_HELPER,
560 void nf_conntrack_helper_pernet_init(struct net *net)
562 net->ct.auto_assign_helper_warned = false;
563 net->ct.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);