Merge branch 'master' of git://1984.lsi.us.es/nf
[~shefty/rdma-dev.git] / net / netfilter / nf_conntrack_helper.c
1 /* Helper handling for netfilter. */
2
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  *
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.
10  */
11
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>
24
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>
32
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;
39
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)");
44
45 #ifdef CONFIG_SYSCTL
46 static struct ctl_table helper_sysctl_table[] = {
47         {
48                 .procname       = "nf_conntrack_helper",
49                 .data           = &init_net.ct.sysctl_auto_assign_helper,
50                 .maxlen         = sizeof(unsigned int),
51                 .mode           = 0644,
52                 .proc_handler   = proc_dointvec,
53         },
54         {}
55 };
56
57 static int nf_conntrack_helper_init_sysctl(struct net *net)
58 {
59         struct ctl_table *table;
60
61         table = kmemdup(helper_sysctl_table, sizeof(helper_sysctl_table),
62                         GFP_KERNEL);
63         if (!table)
64                 goto out;
65
66         table[0].data = &net->ct.sysctl_auto_assign_helper;
67
68         /* Don't export sysctls to unprivileged users */
69         if (net->user_ns != &init_user_ns)
70                 table[0].procname = NULL;
71
72         net->ct.helper_sysctl_header =
73                 register_net_sysctl(net, "net/netfilter", table);
74
75         if (!net->ct.helper_sysctl_header) {
76                 pr_err("nf_conntrack_helper: can't register to sysctl.\n");
77                 goto out_register;
78         }
79         return 0;
80
81 out_register:
82         kfree(table);
83 out:
84         return -ENOMEM;
85 }
86
87 static void nf_conntrack_helper_fini_sysctl(struct net *net)
88 {
89         struct ctl_table *table;
90
91         table = net->ct.helper_sysctl_header->ctl_table_arg;
92         unregister_net_sysctl_table(net->ct.helper_sysctl_header);
93         kfree(table);
94 }
95 #else
96 static int nf_conntrack_helper_init_sysctl(struct net *net)
97 {
98         return 0;
99 }
100
101 static void nf_conntrack_helper_fini_sysctl(struct net *net)
102 {
103 }
104 #endif /* CONFIG_SYSCTL */
105
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)
109 {
110         return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
111                 (__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
112 }
113
114 static struct nf_conntrack_helper *
115 __nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
116 {
117         struct nf_conntrack_helper *helper;
118         struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
119         unsigned int h;
120
121         if (!nf_ct_helper_count)
122                 return NULL;
123
124         h = helper_hash(tuple);
125         hlist_for_each_entry_rcu(helper, &nf_ct_helper_hash[h], hnode) {
126                 if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
127                         return helper;
128         }
129         return NULL;
130 }
131
132 struct nf_conntrack_helper *
133 __nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum)
134 {
135         struct nf_conntrack_helper *h;
136         unsigned int i;
137
138         for (i = 0; i < nf_ct_helper_hsize; i++) {
139                 hlist_for_each_entry_rcu(h, &nf_ct_helper_hash[i], hnode) {
140                         if (!strcmp(h->name, name) &&
141                             h->tuple.src.l3num == l3num &&
142                             h->tuple.dst.protonum == protonum)
143                                 return h;
144                 }
145         }
146         return NULL;
147 }
148 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find);
149
150 struct nf_conntrack_helper *
151 nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
152 {
153         struct nf_conntrack_helper *h;
154
155         h = __nf_conntrack_helper_find(name, l3num, protonum);
156 #ifdef CONFIG_MODULES
157         if (h == NULL) {
158                 if (request_module("nfct-helper-%s", name) == 0)
159                         h = __nf_conntrack_helper_find(name, l3num, protonum);
160         }
161 #endif
162         if (h != NULL && !try_module_get(h->me))
163                 h = NULL;
164
165         return h;
166 }
167 EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);
168
169 struct nf_conn_help *
170 nf_ct_helper_ext_add(struct nf_conn *ct,
171                      struct nf_conntrack_helper *helper, gfp_t gfp)
172 {
173         struct nf_conn_help *help;
174
175         help = nf_ct_ext_add_length(ct, NF_CT_EXT_HELPER,
176                                     helper->data_len, gfp);
177         if (help)
178                 INIT_HLIST_HEAD(&help->expectations);
179         else
180                 pr_debug("failed to add helper extension area");
181         return help;
182 }
183 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
184
185 int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
186                               gfp_t flags)
187 {
188         struct nf_conntrack_helper *helper = NULL;
189         struct nf_conn_help *help;
190         struct net *net = nf_ct_net(ct);
191         int ret = 0;
192
193         /* We already got a helper explicitly attached. The function
194          * nf_conntrack_alter_reply - in case NAT is in use - asks for looking
195          * the helper up again. Since now the user is in full control of
196          * making consistent helper configurations, skip this automatic
197          * re-lookup, otherwise we'll lose the helper.
198          */
199         if (test_bit(IPS_HELPER_BIT, &ct->status))
200                 return 0;
201
202         if (tmpl != NULL) {
203                 help = nfct_help(tmpl);
204                 if (help != NULL) {
205                         helper = help->helper;
206                         set_bit(IPS_HELPER_BIT, &ct->status);
207                 }
208         }
209
210         help = nfct_help(ct);
211         if (net->ct.sysctl_auto_assign_helper && helper == NULL) {
212                 helper = __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
213                 if (unlikely(!net->ct.auto_assign_helper_warned && helper)) {
214                         pr_info("nf_conntrack: automatic helper "
215                                 "assignment is deprecated and it will "
216                                 "be removed soon. Use the iptables CT target "
217                                 "to attach helpers instead.\n");
218                         net->ct.auto_assign_helper_warned = true;
219                 }
220         }
221
222         if (helper == NULL) {
223                 if (help)
224                         RCU_INIT_POINTER(help->helper, NULL);
225                 goto out;
226         }
227
228         if (help == NULL) {
229                 help = nf_ct_helper_ext_add(ct, helper, flags);
230                 if (help == NULL) {
231                         ret = -ENOMEM;
232                         goto out;
233                 }
234         } else {
235                 /* We only allow helper re-assignment of the same sort since
236                  * we cannot reallocate the helper extension area.
237                  */
238                 struct nf_conntrack_helper *tmp = rcu_dereference(help->helper);
239
240                 if (tmp && tmp->help != helper->help) {
241                         RCU_INIT_POINTER(help->helper, NULL);
242                         goto out;
243                 }
244         }
245
246         rcu_assign_pointer(help->helper, helper);
247 out:
248         return ret;
249 }
250 EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
251
252 static inline int unhelp(struct nf_conntrack_tuple_hash *i,
253                          const struct nf_conntrack_helper *me)
254 {
255         struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
256         struct nf_conn_help *help = nfct_help(ct);
257
258         if (help && rcu_dereference_protected(
259                         help->helper,
260                         lockdep_is_held(&nf_conntrack_lock)
261                         ) == me) {
262                 nf_conntrack_event(IPCT_HELPER, ct);
263                 RCU_INIT_POINTER(help->helper, NULL);
264         }
265         return 0;
266 }
267
268 void nf_ct_helper_destroy(struct nf_conn *ct)
269 {
270         struct nf_conn_help *help = nfct_help(ct);
271         struct nf_conntrack_helper *helper;
272
273         if (help) {
274                 rcu_read_lock();
275                 helper = rcu_dereference(help->helper);
276                 if (helper && helper->destroy)
277                         helper->destroy(ct);
278                 rcu_read_unlock();
279         }
280 }
281
282 static LIST_HEAD(nf_ct_helper_expectfn_list);
283
284 void nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn *n)
285 {
286         spin_lock_bh(&nf_conntrack_lock);
287         list_add_rcu(&n->head, &nf_ct_helper_expectfn_list);
288         spin_unlock_bh(&nf_conntrack_lock);
289 }
290 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_register);
291
292 void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn *n)
293 {
294         spin_lock_bh(&nf_conntrack_lock);
295         list_del_rcu(&n->head);
296         spin_unlock_bh(&nf_conntrack_lock);
297 }
298 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_unregister);
299
300 struct nf_ct_helper_expectfn *
301 nf_ct_helper_expectfn_find_by_name(const char *name)
302 {
303         struct nf_ct_helper_expectfn *cur;
304         bool found = false;
305
306         rcu_read_lock();
307         list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
308                 if (!strcmp(cur->name, name)) {
309                         found = true;
310                         break;
311                 }
312         }
313         rcu_read_unlock();
314         return found ? cur : NULL;
315 }
316 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name);
317
318 struct nf_ct_helper_expectfn *
319 nf_ct_helper_expectfn_find_by_symbol(const void *symbol)
320 {
321         struct nf_ct_helper_expectfn *cur;
322         bool found = false;
323
324         rcu_read_lock();
325         list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
326                 if (cur->expectfn == symbol) {
327                         found = true;
328                         break;
329                 }
330         }
331         rcu_read_unlock();
332         return found ? cur : NULL;
333 }
334 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_symbol);
335
336 __printf(3, 4)
337 void nf_ct_helper_log(struct sk_buff *skb, const struct nf_conn *ct,
338                       const char *fmt, ...)
339 {
340         const struct nf_conn_help *help;
341         const struct nf_conntrack_helper *helper;
342         struct va_format vaf;
343         va_list args;
344
345         va_start(args, fmt);
346
347         vaf.fmt = fmt;
348         vaf.va = &args;
349
350         /* Called from the helper function, this call never fails */
351         help = nfct_help(ct);
352
353         /* rcu_read_lock()ed by nf_hook_slow */
354         helper = rcu_dereference(help->helper);
355
356         nf_log_packet(nf_ct_l3num(ct), 0, skb, NULL, NULL, NULL,
357                       "nf_ct_%s: dropping packet: %pV ", helper->name, &vaf);
358
359         va_end(args);
360 }
361 EXPORT_SYMBOL_GPL(nf_ct_helper_log);
362
363 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
364 {
365         int ret = 0;
366         struct nf_conntrack_helper *cur;
367         unsigned int h = helper_hash(&me->tuple);
368
369         BUG_ON(me->expect_policy == NULL);
370         BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
371         BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
372
373         mutex_lock(&nf_ct_helper_mutex);
374         hlist_for_each_entry(cur, &nf_ct_helper_hash[h], hnode) {
375                 if (strncmp(cur->name, me->name, NF_CT_HELPER_NAME_LEN) == 0 &&
376                     cur->tuple.src.l3num == me->tuple.src.l3num &&
377                     cur->tuple.dst.protonum == me->tuple.dst.protonum) {
378                         ret = -EEXIST;
379                         goto out;
380                 }
381         }
382         hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
383         nf_ct_helper_count++;
384 out:
385         mutex_unlock(&nf_ct_helper_mutex);
386         return ret;
387 }
388 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
389
390 static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
391                                              struct net *net)
392 {
393         struct nf_conntrack_tuple_hash *h;
394         struct nf_conntrack_expect *exp;
395         const struct hlist_node *next;
396         const struct hlist_nulls_node *nn;
397         unsigned int i;
398
399         /* Get rid of expectations */
400         for (i = 0; i < nf_ct_expect_hsize; i++) {
401                 hlist_for_each_entry_safe(exp, next,
402                                           &net->ct.expect_hash[i], hnode) {
403                         struct nf_conn_help *help = nfct_help(exp->master);
404                         if ((rcu_dereference_protected(
405                                         help->helper,
406                                         lockdep_is_held(&nf_conntrack_lock)
407                                         ) == me || exp->helper == me) &&
408                             del_timer(&exp->timeout)) {
409                                 nf_ct_unlink_expect(exp);
410                                 nf_ct_expect_put(exp);
411                         }
412                 }
413         }
414
415         /* Get rid of expecteds, set helpers to NULL. */
416         hlist_nulls_for_each_entry(h, nn, &net->ct.unconfirmed, hnnode)
417                 unhelp(h, me);
418         for (i = 0; i < net->ct.htable_size; i++) {
419                 hlist_nulls_for_each_entry(h, nn, &net->ct.hash[i], hnnode)
420                         unhelp(h, me);
421         }
422 }
423
424 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
425 {
426         struct net *net;
427
428         mutex_lock(&nf_ct_helper_mutex);
429         hlist_del_rcu(&me->hnode);
430         nf_ct_helper_count--;
431         mutex_unlock(&nf_ct_helper_mutex);
432
433         /* Make sure every nothing is still using the helper unless its a
434          * connection in the hash.
435          */
436         synchronize_rcu();
437
438         rtnl_lock();
439         spin_lock_bh(&nf_conntrack_lock);
440         for_each_net(net)
441                 __nf_conntrack_helper_unregister(me, net);
442         spin_unlock_bh(&nf_conntrack_lock);
443         rtnl_unlock();
444 }
445 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
446
447 static struct nf_ct_ext_type helper_extend __read_mostly = {
448         .len    = sizeof(struct nf_conn_help),
449         .align  = __alignof__(struct nf_conn_help),
450         .id     = NF_CT_EXT_HELPER,
451 };
452
453 int nf_conntrack_helper_pernet_init(struct net *net)
454 {
455         net->ct.auto_assign_helper_warned = false;
456         net->ct.sysctl_auto_assign_helper = nf_ct_auto_assign_helper;
457         return nf_conntrack_helper_init_sysctl(net);
458 }
459
460 void nf_conntrack_helper_pernet_fini(struct net *net)
461 {
462         nf_conntrack_helper_fini_sysctl(net);
463 }
464
465 int nf_conntrack_helper_init(void)
466 {
467         int ret;
468         nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
469         nf_ct_helper_hash =
470                 nf_ct_alloc_hashtable(&nf_ct_helper_hsize, 0);
471         if (!nf_ct_helper_hash)
472                 return -ENOMEM;
473
474         ret = nf_ct_extend_register(&helper_extend);
475         if (ret < 0) {
476                 pr_err("nf_ct_helper: Unable to register helper extension.\n");
477                 goto out_extend;
478         }
479
480         return 0;
481 out_extend:
482         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize);
483         return ret;
484 }
485
486 void nf_conntrack_helper_fini(void)
487 {
488         nf_ct_extend_unregister(&helper_extend);
489         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize);
490 }