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>
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
12 #include <linux/types.h>
13 #include <linux/netfilter.h>
14 #include <linux/module.h>
15 #include <linux/skbuff.h>
16 #include <linux/vmalloc.h>
17 #include <linux/stddef.h>
18 #include <linux/random.h>
19 #include <linux/err.h>
20 #include <linux/kernel.h>
21 #include <linux/netdevice.h>
22 #include <linux/rculist.h>
23 #include <linux/rtnetlink.h>
25 #include <net/netfilter/nf_conntrack.h>
26 #include <net/netfilter/nf_conntrack_l3proto.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 = true;
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 1)");
46 static struct ctl_table helper_sysctl_table[] = {
48 .procname = "nf_conntrack_helper",
49 .data = &init_net.ct.sysctl_auto_assign_helper,
50 .maxlen = sizeof(unsigned int),
52 .proc_handler = proc_dointvec,
57 static int nf_conntrack_helper_init_sysctl(struct net *net)
59 struct ctl_table *table;
61 table = kmemdup(helper_sysctl_table, sizeof(helper_sysctl_table),
66 table[0].data = &net->ct.sysctl_auto_assign_helper;
68 /* Don't export sysctls to unprivileged users */
69 if (net->user_ns != &init_user_ns)
70 table[0].procname = NULL;
72 net->ct.helper_sysctl_header =
73 register_net_sysctl(net, "net/netfilter", table);
75 if (!net->ct.helper_sysctl_header) {
76 pr_err("nf_conntrack_helper: can't register to sysctl.\n");
87 static void nf_conntrack_helper_fini_sysctl(struct net *net)
89 struct ctl_table *table;
91 table = net->ct.helper_sysctl_header->ctl_table_arg;
92 unregister_net_sysctl_table(net->ct.helper_sysctl_header);
96 static int nf_conntrack_helper_init_sysctl(struct net *net)
101 static void nf_conntrack_helper_fini_sysctl(struct net *net)
104 #endif /* CONFIG_SYSCTL */
106 /* Stupid hash, but collision free for the default registrations of the
107 * helpers currently in the kernel. */
108 static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
110 return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
111 (__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
114 static struct nf_conntrack_helper *
115 __nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
117 struct nf_conntrack_helper *helper;
118 struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
119 struct hlist_node *n;
122 if (!nf_ct_helper_count)
125 h = helper_hash(tuple);
126 hlist_for_each_entry_rcu(helper, n, &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;
137 struct hlist_node *n;
140 for (i = 0; i < nf_ct_helper_hsize; i++) {
141 hlist_for_each_entry_rcu(h, n, &nf_ct_helper_hash[i], hnode) {
142 if (!strcmp(h->name, name) &&
143 h->tuple.src.l3num == l3num &&
144 h->tuple.dst.protonum == protonum)
150 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find);
152 struct nf_conntrack_helper *
153 nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
155 struct nf_conntrack_helper *h;
157 h = __nf_conntrack_helper_find(name, l3num, protonum);
158 #ifdef CONFIG_MODULES
160 if (request_module("nfct-helper-%s", name) == 0)
161 h = __nf_conntrack_helper_find(name, l3num, protonum);
164 if (h != NULL && !try_module_get(h->me))
169 EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);
171 struct nf_conn_help *
172 nf_ct_helper_ext_add(struct nf_conn *ct,
173 struct nf_conntrack_helper *helper, gfp_t gfp)
175 struct nf_conn_help *help;
177 help = nf_ct_ext_add_length(ct, NF_CT_EXT_HELPER,
178 helper->data_len, gfp);
180 INIT_HLIST_HEAD(&help->expectations);
182 pr_debug("failed to add helper extension area");
185 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
187 int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
190 struct nf_conntrack_helper *helper = NULL;
191 struct nf_conn_help *help;
192 struct net *net = nf_ct_net(ct);
195 /* We already got a helper explicitly attached. The function
196 * nf_conntrack_alter_reply - in case NAT is in use - asks for looking
197 * the helper up again. Since now the user is in full control of
198 * making consistent helper configurations, skip this automatic
199 * re-lookup, otherwise we'll lose the helper.
201 if (test_bit(IPS_HELPER_BIT, &ct->status))
205 help = nfct_help(tmpl);
207 helper = help->helper;
208 set_bit(IPS_HELPER_BIT, &ct->status);
212 help = nfct_help(ct);
213 if (net->ct.sysctl_auto_assign_helper && helper == NULL) {
214 helper = __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
215 if (unlikely(!net->ct.auto_assign_helper_warned && helper)) {
216 pr_info("nf_conntrack: automatic helper "
217 "assignment is deprecated and it will "
218 "be removed soon. Use the iptables CT target "
219 "to attach helpers instead.\n");
220 net->ct.auto_assign_helper_warned = true;
224 if (helper == NULL) {
226 RCU_INIT_POINTER(help->helper, NULL);
231 help = nf_ct_helper_ext_add(ct, helper, flags);
237 /* We only allow helper re-assignment of the same sort since
238 * we cannot reallocate the helper extension area.
240 struct nf_conntrack_helper *tmp = rcu_dereference(help->helper);
242 if (tmp && tmp->help != helper->help) {
243 RCU_INIT_POINTER(help->helper, NULL);
248 rcu_assign_pointer(help->helper, helper);
252 EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
254 static inline int unhelp(struct nf_conntrack_tuple_hash *i,
255 const struct nf_conntrack_helper *me)
257 struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
258 struct nf_conn_help *help = nfct_help(ct);
260 if (help && rcu_dereference_protected(
262 lockdep_is_held(&nf_conntrack_lock)
264 nf_conntrack_event(IPCT_HELPER, ct);
265 RCU_INIT_POINTER(help->helper, NULL);
270 void nf_ct_helper_destroy(struct nf_conn *ct)
272 struct nf_conn_help *help = nfct_help(ct);
273 struct nf_conntrack_helper *helper;
277 helper = rcu_dereference(help->helper);
278 if (helper && helper->destroy)
284 static LIST_HEAD(nf_ct_helper_expectfn_list);
286 void nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn *n)
288 spin_lock_bh(&nf_conntrack_lock);
289 list_add_rcu(&n->head, &nf_ct_helper_expectfn_list);
290 spin_unlock_bh(&nf_conntrack_lock);
292 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_register);
294 void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn *n)
296 spin_lock_bh(&nf_conntrack_lock);
297 list_del_rcu(&n->head);
298 spin_unlock_bh(&nf_conntrack_lock);
300 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_unregister);
302 struct nf_ct_helper_expectfn *
303 nf_ct_helper_expectfn_find_by_name(const char *name)
305 struct nf_ct_helper_expectfn *cur;
309 list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
310 if (!strcmp(cur->name, name)) {
316 return found ? cur : NULL;
318 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name);
320 struct nf_ct_helper_expectfn *
321 nf_ct_helper_expectfn_find_by_symbol(const void *symbol)
323 struct nf_ct_helper_expectfn *cur;
327 list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
328 if (cur->expectfn == symbol) {
334 return found ? cur : NULL;
336 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_symbol);
339 void nf_ct_helper_log(struct sk_buff *skb, const struct nf_conn *ct,
340 const char *fmt, ...)
342 const struct nf_conn_help *help;
343 const struct nf_conntrack_helper *helper;
345 /* Called from the helper function, this call never fails */
346 help = nfct_help(ct);
348 /* rcu_read_lock()ed by nf_hook_slow */
349 helper = rcu_dereference(help->helper);
351 nf_log_packet(nf_ct_l3num(ct), 0, skb, NULL, NULL, NULL,
352 "nf_ct_%s: dropping packet: %s ", helper->name, fmt);
354 EXPORT_SYMBOL_GPL(nf_ct_helper_log);
356 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
359 struct nf_conntrack_helper *cur;
360 struct hlist_node *n;
361 unsigned int h = helper_hash(&me->tuple);
363 BUG_ON(me->expect_policy == NULL);
364 BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
365 BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
367 mutex_lock(&nf_ct_helper_mutex);
368 hlist_for_each_entry(cur, n, &nf_ct_helper_hash[h], hnode) {
369 if (strncmp(cur->name, me->name, NF_CT_HELPER_NAME_LEN) == 0 &&
370 cur->tuple.src.l3num == me->tuple.src.l3num &&
371 cur->tuple.dst.protonum == me->tuple.dst.protonum) {
376 hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
377 nf_ct_helper_count++;
379 mutex_unlock(&nf_ct_helper_mutex);
382 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
384 static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
387 struct nf_conntrack_tuple_hash *h;
388 struct nf_conntrack_expect *exp;
389 const struct hlist_node *n, *next;
390 const struct hlist_nulls_node *nn;
393 /* Get rid of expectations */
394 for (i = 0; i < nf_ct_expect_hsize; i++) {
395 hlist_for_each_entry_safe(exp, n, next,
396 &net->ct.expect_hash[i], hnode) {
397 struct nf_conn_help *help = nfct_help(exp->master);
398 if ((rcu_dereference_protected(
400 lockdep_is_held(&nf_conntrack_lock)
401 ) == me || exp->helper == me) &&
402 del_timer(&exp->timeout)) {
403 nf_ct_unlink_expect(exp);
404 nf_ct_expect_put(exp);
409 /* Get rid of expecteds, set helpers to NULL. */
410 hlist_nulls_for_each_entry(h, nn, &net->ct.unconfirmed, hnnode)
412 for (i = 0; i < net->ct.htable_size; i++) {
413 hlist_nulls_for_each_entry(h, nn, &net->ct.hash[i], hnnode)
418 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
422 mutex_lock(&nf_ct_helper_mutex);
423 hlist_del_rcu(&me->hnode);
424 nf_ct_helper_count--;
425 mutex_unlock(&nf_ct_helper_mutex);
427 /* Make sure every nothing is still using the helper unless its a
428 * connection in the hash.
433 spin_lock_bh(&nf_conntrack_lock);
435 __nf_conntrack_helper_unregister(me, net);
436 spin_unlock_bh(&nf_conntrack_lock);
439 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
441 static struct nf_ct_ext_type helper_extend __read_mostly = {
442 .len = sizeof(struct nf_conn_help),
443 .align = __alignof__(struct nf_conn_help),
444 .id = NF_CT_EXT_HELPER,
447 int nf_conntrack_helper_pernet_init(struct net *net)
449 net->ct.auto_assign_helper_warned = false;
450 net->ct.sysctl_auto_assign_helper = nf_ct_auto_assign_helper;
451 return nf_conntrack_helper_init_sysctl(net);
454 void nf_conntrack_helper_pernet_fini(struct net *net)
456 nf_conntrack_helper_fini_sysctl(net);
459 int nf_conntrack_helper_init(void)
462 nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
464 nf_ct_alloc_hashtable(&nf_ct_helper_hsize, 0);
465 if (!nf_ct_helper_hash)
468 ret = nf_ct_extend_register(&helper_extend);
470 pr_err("nf_ct_helper: Unable to register helper extension.\n");
476 nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize);
480 void nf_conntrack_helper_fini(void)
482 nf_ct_extend_unregister(&helper_extend);
483 nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize);