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;
161 h = __nf_conntrack_helper_find(name, l3num, protonum);
162 #ifdef CONFIG_MODULES
164 if (request_module("nfct-helper-%s", name) == 0)
165 h = __nf_conntrack_helper_find(name, l3num, protonum);
168 if (h != NULL && !try_module_get(h->me))
173 EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);
175 struct nf_conn_help *
176 nf_ct_helper_ext_add(struct nf_conn *ct,
177 struct nf_conntrack_helper *helper, gfp_t gfp)
179 struct nf_conn_help *help;
181 help = nf_ct_ext_add_length(ct, NF_CT_EXT_HELPER,
182 helper->data_len, gfp);
184 INIT_HLIST_HEAD(&help->expectations);
186 pr_debug("failed to add helper extension area");
189 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
191 static struct nf_conntrack_helper *
192 nf_ct_lookup_helper(struct nf_conn *ct, struct net *net)
194 if (!net->ct.sysctl_auto_assign_helper) {
195 if (net->ct.auto_assign_helper_warned)
197 if (!__nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple))
199 pr_info("nf_conntrack: default automatic helper assignment "
200 "has been turned off for security reasons and CT-based "
201 " firewall rule not found. Use the iptables CT target "
202 "to attach helpers instead.\n");
203 net->ct.auto_assign_helper_warned = 1;
207 return __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
211 int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
214 struct nf_conntrack_helper *helper = NULL;
215 struct nf_conn_help *help;
216 struct net *net = nf_ct_net(ct);
218 /* We already got a helper explicitly attached. The function
219 * nf_conntrack_alter_reply - in case NAT is in use - asks for looking
220 * the helper up again. Since now the user is in full control of
221 * making consistent helper configurations, skip this automatic
222 * re-lookup, otherwise we'll lose the helper.
224 if (test_bit(IPS_HELPER_BIT, &ct->status))
228 help = nfct_help(tmpl);
230 helper = help->helper;
231 set_bit(IPS_HELPER_BIT, &ct->status);
235 help = nfct_help(ct);
237 if (helper == NULL) {
238 helper = nf_ct_lookup_helper(ct, net);
239 if (helper == NULL) {
241 RCU_INIT_POINTER(help->helper, NULL);
247 help = nf_ct_helper_ext_add(ct, helper, flags);
251 /* We only allow helper re-assignment of the same sort since
252 * we cannot reallocate the helper extension area.
254 struct nf_conntrack_helper *tmp = rcu_dereference(help->helper);
256 if (tmp && tmp->help != helper->help) {
257 RCU_INIT_POINTER(help->helper, NULL);
262 rcu_assign_pointer(help->helper, helper);
266 EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
268 /* appropriate ct lock protecting must be taken by caller */
269 static inline int unhelp(struct nf_conntrack_tuple_hash *i,
270 const struct nf_conntrack_helper *me)
272 struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
273 struct nf_conn_help *help = nfct_help(ct);
275 if (help && rcu_dereference_raw(help->helper) == me) {
276 nf_conntrack_event(IPCT_HELPER, ct);
277 RCU_INIT_POINTER(help->helper, NULL);
282 void nf_ct_helper_destroy(struct nf_conn *ct)
284 struct nf_conn_help *help = nfct_help(ct);
285 struct nf_conntrack_helper *helper;
289 helper = rcu_dereference(help->helper);
290 if (helper && helper->destroy)
296 static LIST_HEAD(nf_ct_helper_expectfn_list);
298 void nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn *n)
300 spin_lock_bh(&nf_conntrack_expect_lock);
301 list_add_rcu(&n->head, &nf_ct_helper_expectfn_list);
302 spin_unlock_bh(&nf_conntrack_expect_lock);
304 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_register);
306 void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn *n)
308 spin_lock_bh(&nf_conntrack_expect_lock);
309 list_del_rcu(&n->head);
310 spin_unlock_bh(&nf_conntrack_expect_lock);
312 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_unregister);
314 struct nf_ct_helper_expectfn *
315 nf_ct_helper_expectfn_find_by_name(const char *name)
317 struct nf_ct_helper_expectfn *cur;
321 list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
322 if (!strcmp(cur->name, name)) {
328 return found ? cur : NULL;
330 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name);
332 struct nf_ct_helper_expectfn *
333 nf_ct_helper_expectfn_find_by_symbol(const void *symbol)
335 struct nf_ct_helper_expectfn *cur;
339 list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
340 if (cur->expectfn == symbol) {
346 return found ? cur : NULL;
348 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_symbol);
351 void nf_ct_helper_log(struct sk_buff *skb, const struct nf_conn *ct,
352 const char *fmt, ...)
354 const struct nf_conn_help *help;
355 const struct nf_conntrack_helper *helper;
356 struct va_format vaf;
364 /* Called from the helper function, this call never fails */
365 help = nfct_help(ct);
367 /* rcu_read_lock()ed by nf_hook_thresh */
368 helper = rcu_dereference(help->helper);
370 nf_log_packet(nf_ct_net(ct), nf_ct_l3num(ct), 0, skb, NULL, NULL, NULL,
371 "nf_ct_%s: dropping packet: %pV ", helper->name, &vaf);
375 EXPORT_SYMBOL_GPL(nf_ct_helper_log);
377 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
379 struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
380 unsigned int h = helper_hash(&me->tuple);
381 struct nf_conntrack_helper *cur;
384 BUG_ON(me->expect_policy == NULL);
385 BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
386 BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
388 mutex_lock(&nf_ct_helper_mutex);
389 for (i = 0; i < nf_ct_helper_hsize; i++) {
390 hlist_for_each_entry(cur, &nf_ct_helper_hash[i], hnode) {
391 if (!strcmp(cur->name, me->name) &&
392 (cur->tuple.src.l3num == NFPROTO_UNSPEC ||
393 cur->tuple.src.l3num == me->tuple.src.l3num) &&
394 cur->tuple.dst.protonum == me->tuple.dst.protonum) {
401 /* avoid unpredictable behaviour for auto_assign_helper */
402 if (!(me->flags & NF_CT_HELPER_F_USERSPACE)) {
403 hlist_for_each_entry(cur, &nf_ct_helper_hash[h], hnode) {
404 if (nf_ct_tuple_src_mask_cmp(&cur->tuple, &me->tuple,
411 hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
412 nf_ct_helper_count++;
414 mutex_unlock(&nf_ct_helper_mutex);
417 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
419 static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
422 struct nf_conntrack_tuple_hash *h;
423 const struct hlist_nulls_node *nn;
426 /* Get rid of expecteds, set helpers to NULL. */
427 for_each_possible_cpu(cpu) {
428 struct ct_pcpu *pcpu = per_cpu_ptr(net->ct.pcpu_lists, cpu);
430 spin_lock_bh(&pcpu->lock);
431 hlist_nulls_for_each_entry(h, nn, &pcpu->unconfirmed, hnnode)
433 spin_unlock_bh(&pcpu->lock);
437 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
439 struct nf_conntrack_tuple_hash *h;
440 struct nf_conntrack_expect *exp;
441 const struct hlist_node *next;
442 const struct hlist_nulls_node *nn;
443 unsigned int last_hsize;
448 mutex_lock(&nf_ct_helper_mutex);
449 hlist_del_rcu(&me->hnode);
450 nf_ct_helper_count--;
451 mutex_unlock(&nf_ct_helper_mutex);
453 /* Make sure every nothing is still using the helper unless its a
454 * connection in the hash.
458 /* Get rid of expectations */
459 spin_lock_bh(&nf_conntrack_expect_lock);
460 for (i = 0; i < nf_ct_expect_hsize; i++) {
461 hlist_for_each_entry_safe(exp, next,
462 &nf_ct_expect_hash[i], hnode) {
463 struct nf_conn_help *help = nfct_help(exp->master);
464 if ((rcu_dereference_protected(
466 lockdep_is_held(&nf_conntrack_expect_lock)
467 ) == me || exp->helper == me) &&
468 del_timer(&exp->timeout)) {
469 nf_ct_unlink_expect(exp);
470 nf_ct_expect_put(exp);
474 spin_unlock_bh(&nf_conntrack_expect_lock);
478 __nf_conntrack_helper_unregister(me, net);
483 last_hsize = nf_conntrack_htable_size;
484 for (i = 0; i < last_hsize; i++) {
485 lock = &nf_conntrack_locks[i % CONNTRACK_LOCKS];
486 nf_conntrack_lock(lock);
487 if (last_hsize != nf_conntrack_htable_size) {
491 hlist_nulls_for_each_entry(h, nn, &nf_conntrack_hash[i], hnnode)
497 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
499 void nf_ct_helper_init(struct nf_conntrack_helper *helper,
500 u16 l3num, u16 protonum, const char *name,
501 u16 default_port, u16 spec_port, u32 id,
502 const struct nf_conntrack_expect_policy *exp_pol,
503 u32 expect_class_max, u32 data_len,
504 int (*help)(struct sk_buff *skb, unsigned int protoff,
506 enum ip_conntrack_info ctinfo),
507 int (*from_nlattr)(struct nlattr *attr,
509 struct module *module)
511 helper->tuple.src.l3num = l3num;
512 helper->tuple.dst.protonum = protonum;
513 helper->tuple.src.u.all = htons(spec_port);
514 helper->expect_policy = exp_pol;
515 helper->expect_class_max = expect_class_max;
516 helper->data_len = data_len;
518 helper->from_nlattr = from_nlattr;
521 if (spec_port == default_port)
522 snprintf(helper->name, sizeof(helper->name), "%s", name);
524 snprintf(helper->name, sizeof(helper->name), "%s-%u", name, id);
526 EXPORT_SYMBOL_GPL(nf_ct_helper_init);
528 int nf_conntrack_helpers_register(struct nf_conntrack_helper *helper,
534 for (i = 0; i < n; i++) {
535 err = nf_conntrack_helper_register(&helper[i]);
543 nf_conntrack_helpers_unregister(helper, i);
546 EXPORT_SYMBOL_GPL(nf_conntrack_helpers_register);
548 void nf_conntrack_helpers_unregister(struct nf_conntrack_helper *helper,
552 nf_conntrack_helper_unregister(&helper[n]);
554 EXPORT_SYMBOL_GPL(nf_conntrack_helpers_unregister);
556 static struct nf_ct_ext_type helper_extend __read_mostly = {
557 .len = sizeof(struct nf_conn_help),
558 .align = __alignof__(struct nf_conn_help),
559 .id = NF_CT_EXT_HELPER,
562 int nf_conntrack_helper_pernet_init(struct net *net)
564 net->ct.auto_assign_helper_warned = false;
565 net->ct.sysctl_auto_assign_helper = nf_ct_auto_assign_helper;
566 return nf_conntrack_helper_init_sysctl(net);
569 void nf_conntrack_helper_pernet_fini(struct net *net)
571 nf_conntrack_helper_fini_sysctl(net);
574 int nf_conntrack_helper_init(void)
577 nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
579 nf_ct_alloc_hashtable(&nf_ct_helper_hsize, 0);
580 if (!nf_ct_helper_hash)
583 ret = nf_ct_extend_register(&helper_extend);
585 pr_err("nf_ct_helper: Unable to register helper extension.\n");
591 nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize);
595 void nf_conntrack_helper_fini(void)
597 nf_ct_extend_unregister(&helper_extend);
598 nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize);