013cdf69fe29a58ed5b360e6bc59b3d80a916489
[~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         struct hlist_node *n;
120         unsigned int h;
121
122         if (!nf_ct_helper_count)
123                 return NULL;
124
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))
128                         return helper;
129         }
130         return NULL;
131 }
132
133 struct nf_conntrack_helper *
134 __nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum)
135 {
136         struct nf_conntrack_helper *h;
137         struct hlist_node *n;
138         unsigned int i;
139
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)
145                                 return h;
146                 }
147         }
148         return NULL;
149 }
150 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find);
151
152 struct nf_conntrack_helper *
153 nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
154 {
155         struct nf_conntrack_helper *h;
156
157         h = __nf_conntrack_helper_find(name, l3num, protonum);
158 #ifdef CONFIG_MODULES
159         if (h == NULL) {
160                 if (request_module("nfct-helper-%s", name) == 0)
161                         h = __nf_conntrack_helper_find(name, l3num, protonum);
162         }
163 #endif
164         if (h != NULL && !try_module_get(h->me))
165                 h = NULL;
166
167         return h;
168 }
169 EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);
170
171 struct nf_conn_help *
172 nf_ct_helper_ext_add(struct nf_conn *ct,
173                      struct nf_conntrack_helper *helper, gfp_t gfp)
174 {
175         struct nf_conn_help *help;
176
177         help = nf_ct_ext_add_length(ct, NF_CT_EXT_HELPER,
178                                     helper->data_len, gfp);
179         if (help)
180                 INIT_HLIST_HEAD(&help->expectations);
181         else
182                 pr_debug("failed to add helper extension area");
183         return help;
184 }
185 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
186
187 int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
188                               gfp_t flags)
189 {
190         struct nf_conntrack_helper *helper = NULL;
191         struct nf_conn_help *help;
192         struct net *net = nf_ct_net(ct);
193         int ret = 0;
194
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.
200          */
201         if (test_bit(IPS_HELPER_BIT, &ct->status))
202                 return 0;
203
204         if (tmpl != NULL) {
205                 help = nfct_help(tmpl);
206                 if (help != NULL) {
207                         helper = help->helper;
208                         set_bit(IPS_HELPER_BIT, &ct->status);
209                 }
210         }
211
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;
221                 }
222         }
223
224         if (helper == NULL) {
225                 if (help)
226                         RCU_INIT_POINTER(help->helper, NULL);
227                 goto out;
228         }
229
230         if (help == NULL) {
231                 help = nf_ct_helper_ext_add(ct, helper, flags);
232                 if (help == NULL) {
233                         ret = -ENOMEM;
234                         goto out;
235                 }
236         } else {
237                 /* We only allow helper re-assignment of the same sort since
238                  * we cannot reallocate the helper extension area.
239                  */
240                 struct nf_conntrack_helper *tmp = rcu_dereference(help->helper);
241
242                 if (tmp && tmp->help != helper->help) {
243                         RCU_INIT_POINTER(help->helper, NULL);
244                         goto out;
245                 }
246         }
247
248         rcu_assign_pointer(help->helper, helper);
249 out:
250         return ret;
251 }
252 EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
253
254 static inline int unhelp(struct nf_conntrack_tuple_hash *i,
255                          const struct nf_conntrack_helper *me)
256 {
257         struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
258         struct nf_conn_help *help = nfct_help(ct);
259
260         if (help && rcu_dereference_protected(
261                         help->helper,
262                         lockdep_is_held(&nf_conntrack_lock)
263                         ) == me) {
264                 nf_conntrack_event(IPCT_HELPER, ct);
265                 RCU_INIT_POINTER(help->helper, NULL);
266         }
267         return 0;
268 }
269
270 void nf_ct_helper_destroy(struct nf_conn *ct)
271 {
272         struct nf_conn_help *help = nfct_help(ct);
273         struct nf_conntrack_helper *helper;
274
275         if (help) {
276                 rcu_read_lock();
277                 helper = rcu_dereference(help->helper);
278                 if (helper && helper->destroy)
279                         helper->destroy(ct);
280                 rcu_read_unlock();
281         }
282 }
283
284 static LIST_HEAD(nf_ct_helper_expectfn_list);
285
286 void nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn *n)
287 {
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);
291 }
292 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_register);
293
294 void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn *n)
295 {
296         spin_lock_bh(&nf_conntrack_lock);
297         list_del_rcu(&n->head);
298         spin_unlock_bh(&nf_conntrack_lock);
299 }
300 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_unregister);
301
302 struct nf_ct_helper_expectfn *
303 nf_ct_helper_expectfn_find_by_name(const char *name)
304 {
305         struct nf_ct_helper_expectfn *cur;
306         bool found = false;
307
308         rcu_read_lock();
309         list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
310                 if (!strcmp(cur->name, name)) {
311                         found = true;
312                         break;
313                 }
314         }
315         rcu_read_unlock();
316         return found ? cur : NULL;
317 }
318 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name);
319
320 struct nf_ct_helper_expectfn *
321 nf_ct_helper_expectfn_find_by_symbol(const void *symbol)
322 {
323         struct nf_ct_helper_expectfn *cur;
324         bool found = false;
325
326         rcu_read_lock();
327         list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
328                 if (cur->expectfn == symbol) {
329                         found = true;
330                         break;
331                 }
332         }
333         rcu_read_unlock();
334         return found ? cur : NULL;
335 }
336 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_symbol);
337
338 __printf(3, 4)
339 void nf_ct_helper_log(struct sk_buff *skb, const struct nf_conn *ct,
340                       const char *fmt, ...)
341 {
342         const struct nf_conn_help *help;
343         const struct nf_conntrack_helper *helper;
344
345         /* Called from the helper function, this call never fails */
346         help = nfct_help(ct);
347
348         /* rcu_read_lock()ed by nf_hook_slow */
349         helper = rcu_dereference(help->helper);
350
351         nf_log_packet(nf_ct_l3num(ct), 0, skb, NULL, NULL, NULL,
352                       "nf_ct_%s: dropping packet: %s ", helper->name, fmt);
353 }
354 EXPORT_SYMBOL_GPL(nf_ct_helper_log);
355
356 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
357 {
358         int ret = 0;
359         struct nf_conntrack_helper *cur;
360         struct hlist_node *n;
361         unsigned int h = helper_hash(&me->tuple);
362
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);
366
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) {
372                         ret = -EEXIST;
373                         goto out;
374                 }
375         }
376         hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
377         nf_ct_helper_count++;
378 out:
379         mutex_unlock(&nf_ct_helper_mutex);
380         return ret;
381 }
382 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
383
384 static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
385                                              struct net *net)
386 {
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;
391         unsigned int i;
392
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(
399                                         help->helper,
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);
405                         }
406                 }
407         }
408
409         /* Get rid of expecteds, set helpers to NULL. */
410         hlist_nulls_for_each_entry(h, nn, &net->ct.unconfirmed, hnnode)
411                 unhelp(h, me);
412         for (i = 0; i < net->ct.htable_size; i++) {
413                 hlist_nulls_for_each_entry(h, nn, &net->ct.hash[i], hnnode)
414                         unhelp(h, me);
415         }
416 }
417
418 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
419 {
420         struct net *net;
421
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);
426
427         /* Make sure every nothing is still using the helper unless its a
428          * connection in the hash.
429          */
430         synchronize_rcu();
431
432         rtnl_lock();
433         spin_lock_bh(&nf_conntrack_lock);
434         for_each_net(net)
435                 __nf_conntrack_helper_unregister(me, net);
436         spin_unlock_bh(&nf_conntrack_lock);
437         rtnl_unlock();
438 }
439 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
440
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,
445 };
446
447 int nf_conntrack_helper_pernet_init(struct net *net)
448 {
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);
452 }
453
454 void nf_conntrack_helper_pernet_fini(struct net *net)
455 {
456         nf_conntrack_helper_fini_sysctl(net);
457 }
458
459 int nf_conntrack_helper_init(void)
460 {
461         int ret;
462         nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
463         nf_ct_helper_hash =
464                 nf_ct_alloc_hashtable(&nf_ct_helper_hsize, 0);
465         if (!nf_ct_helper_hash)
466                 return -ENOMEM;
467
468         ret = nf_ct_extend_register(&helper_extend);
469         if (ret < 0) {
470                 pr_err("nf_ct_helper: Unable to register helper extension.\n");
471                 goto out_extend;
472         }
473
474         return 0;
475 out_extend:
476         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize);
477         return ret;
478 }
479
480 void nf_conntrack_helper_fini(void)
481 {
482         nf_ct_extend_unregister(&helper_extend);
483         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize);
484 }