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_l3proto.h>
28 #include <net/netfilter/nf_conntrack_l4proto.h>
29 #include <net/netfilter/nf_conntrack_helper.h>
30 #include <net/netfilter/nf_conntrack_core.h>
31 #include <net/netfilter/nf_conntrack_extend.h>
32 #include <net/netfilter/nf_log.h>
34 static DEFINE_MUTEX(nf_ct_helper_mutex);
35 struct hlist_head *nf_ct_helper_hash __read_mostly;
36 EXPORT_SYMBOL_GPL(nf_ct_helper_hash);
37 unsigned int nf_ct_helper_hsize __read_mostly;
38 EXPORT_SYMBOL_GPL(nf_ct_helper_hsize);
39 static unsigned int nf_ct_helper_count __read_mostly;
41 static bool nf_ct_auto_assign_helper __read_mostly = false;
42 module_param_named(nf_conntrack_helper, nf_ct_auto_assign_helper, bool, 0644);
43 MODULE_PARM_DESC(nf_conntrack_helper,
44 "Enable automatic conntrack helper assignment (default 0)");
47 static struct ctl_table helper_sysctl_table[] = {
49 .procname = "nf_conntrack_helper",
50 .data = &init_net.ct.sysctl_auto_assign_helper,
51 .maxlen = sizeof(unsigned int),
53 .proc_handler = proc_dointvec,
58 static int nf_conntrack_helper_init_sysctl(struct net *net)
60 struct ctl_table *table;
62 table = kmemdup(helper_sysctl_table, sizeof(helper_sysctl_table),
67 table[0].data = &net->ct.sysctl_auto_assign_helper;
69 /* Don't export sysctls to unprivileged users */
70 if (net->user_ns != &init_user_ns)
71 table[0].procname = NULL;
73 net->ct.helper_sysctl_header =
74 register_net_sysctl(net, "net/netfilter", table);
76 if (!net->ct.helper_sysctl_header) {
77 pr_err("nf_conntrack_helper: can't register to sysctl.\n");
88 static void nf_conntrack_helper_fini_sysctl(struct net *net)
90 struct ctl_table *table;
92 table = net->ct.helper_sysctl_header->ctl_table_arg;
93 unregister_net_sysctl_table(net->ct.helper_sysctl_header);
97 static int nf_conntrack_helper_init_sysctl(struct net *net)
102 static void nf_conntrack_helper_fini_sysctl(struct net *net)
105 #endif /* CONFIG_SYSCTL */
107 /* Stupid hash, but collision free for the default registrations of the
108 * helpers currently in the kernel. */
109 static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
111 return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
112 (__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
115 static struct nf_conntrack_helper *
116 __nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
118 struct nf_conntrack_helper *helper;
119 struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
122 if (!nf_ct_helper_count)
125 h = helper_hash(tuple);
126 hlist_for_each_entry_rcu(helper, &nf_ct_helper_hash[h], hnode) {
127 if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
133 struct nf_conntrack_helper *
134 __nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum)
136 struct nf_conntrack_helper *h;
139 for (i = 0; i < nf_ct_helper_hsize; i++) {
140 hlist_for_each_entry_rcu(h, &nf_ct_helper_hash[i], hnode) {
141 if (strcmp(h->name, name))
144 if (h->tuple.src.l3num != NFPROTO_UNSPEC &&
145 h->tuple.src.l3num != l3num)
148 if (h->tuple.dst.protonum == protonum)
154 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find);
156 struct nf_conntrack_helper *
157 nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
159 struct nf_conntrack_helper *h;
163 h = __nf_conntrack_helper_find(name, l3num, protonum);
164 #ifdef CONFIG_MODULES
167 if (request_module("nfct-helper-%s", name) == 0) {
169 h = __nf_conntrack_helper_find(name, l3num, protonum);
175 if (h != NULL && !try_module_get(h->me))
177 if (h != NULL && !refcount_inc_not_zero(&h->refcnt)) {
186 EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);
188 void nf_conntrack_helper_put(struct nf_conntrack_helper *helper)
190 refcount_dec(&helper->refcnt);
191 module_put(helper->me);
193 EXPORT_SYMBOL_GPL(nf_conntrack_helper_put);
195 struct nf_conn_help *
196 nf_ct_helper_ext_add(struct nf_conn *ct,
197 struct nf_conntrack_helper *helper, gfp_t gfp)
199 struct nf_conn_help *help;
201 help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
203 INIT_HLIST_HEAD(&help->expectations);
205 pr_debug("failed to add helper extension area");
208 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
210 static struct nf_conntrack_helper *
211 nf_ct_lookup_helper(struct nf_conn *ct, struct net *net)
213 if (!net->ct.sysctl_auto_assign_helper) {
214 if (net->ct.auto_assign_helper_warned)
216 if (!__nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple))
218 pr_info("nf_conntrack: default automatic helper assignment "
219 "has been turned off for security reasons and CT-based "
220 " firewall rule not found. Use the iptables CT target "
221 "to attach helpers instead.\n");
222 net->ct.auto_assign_helper_warned = 1;
226 return __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
230 int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
233 struct nf_conntrack_helper *helper = NULL;
234 struct nf_conn_help *help;
235 struct net *net = nf_ct_net(ct);
237 /* We already got a helper explicitly attached. The function
238 * nf_conntrack_alter_reply - in case NAT is in use - asks for looking
239 * the helper up again. Since now the user is in full control of
240 * making consistent helper configurations, skip this automatic
241 * re-lookup, otherwise we'll lose the helper.
243 if (test_bit(IPS_HELPER_BIT, &ct->status))
247 help = nfct_help(tmpl);
249 helper = help->helper;
250 set_bit(IPS_HELPER_BIT, &ct->status);
254 help = nfct_help(ct);
256 if (helper == NULL) {
257 helper = nf_ct_lookup_helper(ct, net);
258 if (helper == NULL) {
260 RCU_INIT_POINTER(help->helper, NULL);
266 help = nf_ct_helper_ext_add(ct, helper, flags);
270 /* We only allow helper re-assignment of the same sort since
271 * we cannot reallocate the helper extension area.
273 struct nf_conntrack_helper *tmp = rcu_dereference(help->helper);
275 if (tmp && tmp->help != helper->help) {
276 RCU_INIT_POINTER(help->helper, NULL);
281 rcu_assign_pointer(help->helper, helper);
285 EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
287 /* appropriate ct lock protecting must be taken by caller */
288 static inline int unhelp(struct nf_conntrack_tuple_hash *i,
289 const struct nf_conntrack_helper *me)
291 struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
292 struct nf_conn_help *help = nfct_help(ct);
294 if (help && rcu_dereference_raw(help->helper) == me) {
295 nf_conntrack_event(IPCT_HELPER, ct);
296 RCU_INIT_POINTER(help->helper, NULL);
301 void nf_ct_helper_destroy(struct nf_conn *ct)
303 struct nf_conn_help *help = nfct_help(ct);
304 struct nf_conntrack_helper *helper;
308 helper = rcu_dereference(help->helper);
309 if (helper && helper->destroy)
315 static LIST_HEAD(nf_ct_helper_expectfn_list);
317 void nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn *n)
319 spin_lock_bh(&nf_conntrack_expect_lock);
320 list_add_rcu(&n->head, &nf_ct_helper_expectfn_list);
321 spin_unlock_bh(&nf_conntrack_expect_lock);
323 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_register);
325 void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn *n)
327 spin_lock_bh(&nf_conntrack_expect_lock);
328 list_del_rcu(&n->head);
329 spin_unlock_bh(&nf_conntrack_expect_lock);
331 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_unregister);
333 /* Caller should hold the rcu lock */
334 struct nf_ct_helper_expectfn *
335 nf_ct_helper_expectfn_find_by_name(const char *name)
337 struct nf_ct_helper_expectfn *cur;
340 list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
341 if (!strcmp(cur->name, name)) {
346 return found ? cur : NULL;
348 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name);
350 /* Caller should hold the rcu lock */
351 struct nf_ct_helper_expectfn *
352 nf_ct_helper_expectfn_find_by_symbol(const void *symbol)
354 struct nf_ct_helper_expectfn *cur;
357 list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
358 if (cur->expectfn == symbol) {
363 return found ? cur : NULL;
365 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_symbol);
368 void nf_ct_helper_log(struct sk_buff *skb, const struct nf_conn *ct,
369 const char *fmt, ...)
371 const struct nf_conn_help *help;
372 const struct nf_conntrack_helper *helper;
373 struct va_format vaf;
381 /* Called from the helper function, this call never fails */
382 help = nfct_help(ct);
384 /* rcu_read_lock()ed by nf_hook_thresh */
385 helper = rcu_dereference(help->helper);
387 nf_log_packet(nf_ct_net(ct), nf_ct_l3num(ct), 0, skb, NULL, NULL, NULL,
388 "nf_ct_%s: dropping packet: %pV ", helper->name, &vaf);
392 EXPORT_SYMBOL_GPL(nf_ct_helper_log);
394 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
396 struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
397 unsigned int h = helper_hash(&me->tuple);
398 struct nf_conntrack_helper *cur;
401 BUG_ON(me->expect_policy == NULL);
402 BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
403 BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
405 if (me->expect_policy->max_expected > NF_CT_EXPECT_MAX_CNT)
408 mutex_lock(&nf_ct_helper_mutex);
409 for (i = 0; i < nf_ct_helper_hsize; i++) {
410 hlist_for_each_entry(cur, &nf_ct_helper_hash[i], hnode) {
411 if (!strcmp(cur->name, me->name) &&
412 (cur->tuple.src.l3num == NFPROTO_UNSPEC ||
413 cur->tuple.src.l3num == me->tuple.src.l3num) &&
414 cur->tuple.dst.protonum == me->tuple.dst.protonum) {
421 /* avoid unpredictable behaviour for auto_assign_helper */
422 if (!(me->flags & NF_CT_HELPER_F_USERSPACE)) {
423 hlist_for_each_entry(cur, &nf_ct_helper_hash[h], hnode) {
424 if (nf_ct_tuple_src_mask_cmp(&cur->tuple, &me->tuple,
431 refcount_set(&me->refcnt, 1);
432 hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
433 nf_ct_helper_count++;
435 mutex_unlock(&nf_ct_helper_mutex);
438 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
440 static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
443 struct nf_conntrack_tuple_hash *h;
444 const struct hlist_nulls_node *nn;
447 /* Get rid of expecteds, set helpers to NULL. */
448 for_each_possible_cpu(cpu) {
449 struct ct_pcpu *pcpu = per_cpu_ptr(net->ct.pcpu_lists, cpu);
451 spin_lock_bh(&pcpu->lock);
452 hlist_nulls_for_each_entry(h, nn, &pcpu->unconfirmed, hnnode)
454 spin_unlock_bh(&pcpu->lock);
458 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
460 struct nf_conntrack_tuple_hash *h;
461 struct nf_conntrack_expect *exp;
462 const struct hlist_node *next;
463 const struct hlist_nulls_node *nn;
464 unsigned int last_hsize;
469 mutex_lock(&nf_ct_helper_mutex);
470 hlist_del_rcu(&me->hnode);
471 nf_ct_helper_count--;
472 mutex_unlock(&nf_ct_helper_mutex);
474 /* Make sure every nothing is still using the helper unless its a
475 * connection in the hash.
479 /* Get rid of expectations */
480 spin_lock_bh(&nf_conntrack_expect_lock);
481 for (i = 0; i < nf_ct_expect_hsize; i++) {
482 hlist_for_each_entry_safe(exp, next,
483 &nf_ct_expect_hash[i], hnode) {
484 struct nf_conn_help *help = nfct_help(exp->master);
485 if ((rcu_dereference_protected(
487 lockdep_is_held(&nf_conntrack_expect_lock)
488 ) == me || exp->helper == me))
489 nf_ct_remove_expect(exp);
492 spin_unlock_bh(&nf_conntrack_expect_lock);
496 __nf_conntrack_helper_unregister(me, net);
501 last_hsize = nf_conntrack_htable_size;
502 for (i = 0; i < last_hsize; i++) {
503 lock = &nf_conntrack_locks[i % CONNTRACK_LOCKS];
504 nf_conntrack_lock(lock);
505 if (last_hsize != nf_conntrack_htable_size) {
509 hlist_nulls_for_each_entry(h, nn, &nf_conntrack_hash[i], hnnode)
515 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
517 void nf_ct_helper_init(struct nf_conntrack_helper *helper,
518 u16 l3num, u16 protonum, const char *name,
519 u16 default_port, u16 spec_port, u32 id,
520 const struct nf_conntrack_expect_policy *exp_pol,
521 u32 expect_class_max,
522 int (*help)(struct sk_buff *skb, unsigned int protoff,
524 enum ip_conntrack_info ctinfo),
525 int (*from_nlattr)(struct nlattr *attr,
527 struct module *module)
529 helper->tuple.src.l3num = l3num;
530 helper->tuple.dst.protonum = protonum;
531 helper->tuple.src.u.all = htons(spec_port);
532 helper->expect_policy = exp_pol;
533 helper->expect_class_max = expect_class_max;
535 helper->from_nlattr = from_nlattr;
538 if (spec_port == default_port)
539 snprintf(helper->name, sizeof(helper->name), "%s", name);
541 snprintf(helper->name, sizeof(helper->name), "%s-%u", name, id);
543 EXPORT_SYMBOL_GPL(nf_ct_helper_init);
545 int nf_conntrack_helpers_register(struct nf_conntrack_helper *helper,
551 for (i = 0; i < n; i++) {
552 err = nf_conntrack_helper_register(&helper[i]);
560 nf_conntrack_helpers_unregister(helper, i);
563 EXPORT_SYMBOL_GPL(nf_conntrack_helpers_register);
565 void nf_conntrack_helpers_unregister(struct nf_conntrack_helper *helper,
569 nf_conntrack_helper_unregister(&helper[n]);
571 EXPORT_SYMBOL_GPL(nf_conntrack_helpers_unregister);
573 static const struct nf_ct_ext_type helper_extend = {
574 .len = sizeof(struct nf_conn_help),
575 .align = __alignof__(struct nf_conn_help),
576 .id = NF_CT_EXT_HELPER,
579 int nf_conntrack_helper_pernet_init(struct net *net)
581 net->ct.auto_assign_helper_warned = false;
582 net->ct.sysctl_auto_assign_helper = nf_ct_auto_assign_helper;
583 return nf_conntrack_helper_init_sysctl(net);
586 void nf_conntrack_helper_pernet_fini(struct net *net)
588 nf_conntrack_helper_fini_sysctl(net);
591 int nf_conntrack_helper_init(void)
594 nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
596 nf_ct_alloc_hashtable(&nf_ct_helper_hsize, 0);
597 if (!nf_ct_helper_hash)
600 ret = nf_ct_extend_register(&helper_extend);
602 pr_err("nf_ct_helper: Unable to register helper extension.\n");
608 nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize);
612 void nf_conntrack_helper_fini(void)
614 nf_ct_extend_unregister(&helper_extend);
615 nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize);