1343a4bb4031c6e83a6d28d131fbdcad77355f86
[~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
32 static DEFINE_MUTEX(nf_ct_helper_mutex);
33 struct hlist_head *nf_ct_helper_hash __read_mostly;
34 EXPORT_SYMBOL_GPL(nf_ct_helper_hash);
35 unsigned int nf_ct_helper_hsize __read_mostly;
36 EXPORT_SYMBOL_GPL(nf_ct_helper_hsize);
37 static unsigned int nf_ct_helper_count __read_mostly;
38
39 static bool nf_ct_auto_assign_helper __read_mostly = true;
40 module_param_named(nf_conntrack_helper, nf_ct_auto_assign_helper, bool, 0644);
41 MODULE_PARM_DESC(nf_conntrack_helper,
42                  "Enable automatic conntrack helper assignment (default 1)");
43
44 #ifdef CONFIG_SYSCTL
45 static struct ctl_table helper_sysctl_table[] = {
46         {
47                 .procname       = "nf_conntrack_helper",
48                 .data           = &init_net.ct.sysctl_auto_assign_helper,
49                 .maxlen         = sizeof(unsigned int),
50                 .mode           = 0644,
51                 .proc_handler   = proc_dointvec,
52         },
53         {}
54 };
55
56 static int nf_conntrack_helper_init_sysctl(struct net *net)
57 {
58         struct ctl_table *table;
59
60         table = kmemdup(helper_sysctl_table, sizeof(helper_sysctl_table),
61                         GFP_KERNEL);
62         if (!table)
63                 goto out;
64
65         table[0].data = &net->ct.sysctl_auto_assign_helper;
66
67         /* Don't export sysctls to unprivileged users */
68         if (net->user_ns != &init_user_ns)
69                 table[0].procname = NULL;
70
71         net->ct.helper_sysctl_header =
72                 register_net_sysctl(net, "net/netfilter", table);
73
74         if (!net->ct.helper_sysctl_header) {
75                 pr_err("nf_conntrack_helper: can't register to sysctl.\n");
76                 goto out_register;
77         }
78         return 0;
79
80 out_register:
81         kfree(table);
82 out:
83         return -ENOMEM;
84 }
85
86 static void nf_conntrack_helper_fini_sysctl(struct net *net)
87 {
88         struct ctl_table *table;
89
90         table = net->ct.helper_sysctl_header->ctl_table_arg;
91         unregister_net_sysctl_table(net->ct.helper_sysctl_header);
92         kfree(table);
93 }
94 #else
95 static int nf_conntrack_helper_init_sysctl(struct net *net)
96 {
97         return 0;
98 }
99
100 static void nf_conntrack_helper_fini_sysctl(struct net *net)
101 {
102 }
103 #endif /* CONFIG_SYSCTL */
104
105 /* Stupid hash, but collision free for the default registrations of the
106  * helpers currently in the kernel. */
107 static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
108 {
109         return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
110                 (__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
111 }
112
113 static struct nf_conntrack_helper *
114 __nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
115 {
116         struct nf_conntrack_helper *helper;
117         struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
118         struct hlist_node *n;
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, n, &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         struct hlist_node *n;
137         unsigned int i;
138
139         for (i = 0; i < nf_ct_helper_hsize; i++) {
140                 hlist_for_each_entry_rcu(h, n, &nf_ct_helper_hash[i], hnode) {
141                         if (!strcmp(h->name, name) &&
142                             h->tuple.src.l3num == l3num &&
143                             h->tuple.dst.protonum == protonum)
144                                 return h;
145                 }
146         }
147         return NULL;
148 }
149 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find);
150
151 struct nf_conntrack_helper *
152 nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
153 {
154         struct nf_conntrack_helper *h;
155
156         h = __nf_conntrack_helper_find(name, l3num, protonum);
157 #ifdef CONFIG_MODULES
158         if (h == NULL) {
159                 if (request_module("nfct-helper-%s", name) == 0)
160                         h = __nf_conntrack_helper_find(name, l3num, protonum);
161         }
162 #endif
163         if (h != NULL && !try_module_get(h->me))
164                 h = NULL;
165
166         return h;
167 }
168 EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);
169
170 struct nf_conn_help *
171 nf_ct_helper_ext_add(struct nf_conn *ct,
172                      struct nf_conntrack_helper *helper, gfp_t gfp)
173 {
174         struct nf_conn_help *help;
175
176         help = nf_ct_ext_add_length(ct, NF_CT_EXT_HELPER,
177                                     helper->data_len, gfp);
178         if (help)
179                 INIT_HLIST_HEAD(&help->expectations);
180         else
181                 pr_debug("failed to add helper extension area");
182         return help;
183 }
184 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
185
186 int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
187                               gfp_t flags)
188 {
189         struct nf_conntrack_helper *helper = NULL;
190         struct nf_conn_help *help;
191         struct net *net = nf_ct_net(ct);
192         int ret = 0;
193
194         /* We already got a helper explicitly attached. The function
195          * nf_conntrack_alter_reply - in case NAT is in use - asks for looking
196          * the helper up again. Since now the user is in full control of
197          * making consistent helper configurations, skip this automatic
198          * re-lookup, otherwise we'll lose the helper.
199          */
200         if (test_bit(IPS_HELPER_BIT, &ct->status))
201                 return 0;
202
203         if (tmpl != NULL) {
204                 help = nfct_help(tmpl);
205                 if (help != NULL) {
206                         helper = help->helper;
207                         set_bit(IPS_HELPER_BIT, &ct->status);
208                 }
209         }
210
211         help = nfct_help(ct);
212         if (net->ct.sysctl_auto_assign_helper && helper == NULL) {
213                 helper = __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
214                 if (unlikely(!net->ct.auto_assign_helper_warned && helper)) {
215                         pr_info("nf_conntrack: automatic helper "
216                                 "assignment is deprecated and it will "
217                                 "be removed soon. Use the iptables CT target "
218                                 "to attach helpers instead.\n");
219                         net->ct.auto_assign_helper_warned = true;
220                 }
221         }
222
223         if (helper == NULL) {
224                 if (help)
225                         RCU_INIT_POINTER(help->helper, NULL);
226                 goto out;
227         }
228
229         if (help == NULL) {
230                 help = nf_ct_helper_ext_add(ct, helper, flags);
231                 if (help == NULL) {
232                         ret = -ENOMEM;
233                         goto out;
234                 }
235         } else {
236                 /* We only allow helper re-assignment of the same sort since
237                  * we cannot reallocate the helper extension area.
238                  */
239                 struct nf_conntrack_helper *tmp = rcu_dereference(help->helper);
240
241                 if (tmp && tmp->help != helper->help) {
242                         RCU_INIT_POINTER(help->helper, NULL);
243                         goto out;
244                 }
245         }
246
247         rcu_assign_pointer(help->helper, helper);
248 out:
249         return ret;
250 }
251 EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
252
253 static inline int unhelp(struct nf_conntrack_tuple_hash *i,
254                          const struct nf_conntrack_helper *me)
255 {
256         struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
257         struct nf_conn_help *help = nfct_help(ct);
258
259         if (help && rcu_dereference_protected(
260                         help->helper,
261                         lockdep_is_held(&nf_conntrack_lock)
262                         ) == me) {
263                 nf_conntrack_event(IPCT_HELPER, ct);
264                 RCU_INIT_POINTER(help->helper, NULL);
265         }
266         return 0;
267 }
268
269 void nf_ct_helper_destroy(struct nf_conn *ct)
270 {
271         struct nf_conn_help *help = nfct_help(ct);
272         struct nf_conntrack_helper *helper;
273
274         if (help) {
275                 rcu_read_lock();
276                 helper = rcu_dereference(help->helper);
277                 if (helper && helper->destroy)
278                         helper->destroy(ct);
279                 rcu_read_unlock();
280         }
281 }
282
283 static LIST_HEAD(nf_ct_helper_expectfn_list);
284
285 void nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn *n)
286 {
287         spin_lock_bh(&nf_conntrack_lock);
288         list_add_rcu(&n->head, &nf_ct_helper_expectfn_list);
289         spin_unlock_bh(&nf_conntrack_lock);
290 }
291 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_register);
292
293 void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn *n)
294 {
295         spin_lock_bh(&nf_conntrack_lock);
296         list_del_rcu(&n->head);
297         spin_unlock_bh(&nf_conntrack_lock);
298 }
299 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_unregister);
300
301 struct nf_ct_helper_expectfn *
302 nf_ct_helper_expectfn_find_by_name(const char *name)
303 {
304         struct nf_ct_helper_expectfn *cur;
305         bool found = false;
306
307         rcu_read_lock();
308         list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
309                 if (!strcmp(cur->name, name)) {
310                         found = true;
311                         break;
312                 }
313         }
314         rcu_read_unlock();
315         return found ? cur : NULL;
316 }
317 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name);
318
319 struct nf_ct_helper_expectfn *
320 nf_ct_helper_expectfn_find_by_symbol(const void *symbol)
321 {
322         struct nf_ct_helper_expectfn *cur;
323         bool found = false;
324
325         rcu_read_lock();
326         list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
327                 if (cur->expectfn == symbol) {
328                         found = true;
329                         break;
330                 }
331         }
332         rcu_read_unlock();
333         return found ? cur : NULL;
334 }
335 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_symbol);
336
337 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
338 {
339         int ret = 0;
340         struct nf_conntrack_helper *cur;
341         struct hlist_node *n;
342         unsigned int h = helper_hash(&me->tuple);
343
344         BUG_ON(me->expect_policy == NULL);
345         BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
346         BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
347
348         mutex_lock(&nf_ct_helper_mutex);
349         hlist_for_each_entry(cur, n, &nf_ct_helper_hash[h], hnode) {
350                 if (strncmp(cur->name, me->name, NF_CT_HELPER_NAME_LEN) == 0 &&
351                     cur->tuple.src.l3num == me->tuple.src.l3num &&
352                     cur->tuple.dst.protonum == me->tuple.dst.protonum) {
353                         ret = -EEXIST;
354                         goto out;
355                 }
356         }
357         hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
358         nf_ct_helper_count++;
359 out:
360         mutex_unlock(&nf_ct_helper_mutex);
361         return ret;
362 }
363 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
364
365 static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
366                                              struct net *net)
367 {
368         struct nf_conntrack_tuple_hash *h;
369         struct nf_conntrack_expect *exp;
370         const struct hlist_node *n, *next;
371         const struct hlist_nulls_node *nn;
372         unsigned int i;
373
374         /* Get rid of expectations */
375         for (i = 0; i < nf_ct_expect_hsize; i++) {
376                 hlist_for_each_entry_safe(exp, n, next,
377                                           &net->ct.expect_hash[i], hnode) {
378                         struct nf_conn_help *help = nfct_help(exp->master);
379                         if ((rcu_dereference_protected(
380                                         help->helper,
381                                         lockdep_is_held(&nf_conntrack_lock)
382                                         ) == me || exp->helper == me) &&
383                             del_timer(&exp->timeout)) {
384                                 nf_ct_unlink_expect(exp);
385                                 nf_ct_expect_put(exp);
386                         }
387                 }
388         }
389
390         /* Get rid of expecteds, set helpers to NULL. */
391         hlist_nulls_for_each_entry(h, nn, &net->ct.unconfirmed, hnnode)
392                 unhelp(h, me);
393         for (i = 0; i < net->ct.htable_size; i++) {
394                 hlist_nulls_for_each_entry(h, nn, &net->ct.hash[i], hnnode)
395                         unhelp(h, me);
396         }
397 }
398
399 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
400 {
401         struct net *net;
402
403         mutex_lock(&nf_ct_helper_mutex);
404         hlist_del_rcu(&me->hnode);
405         nf_ct_helper_count--;
406         mutex_unlock(&nf_ct_helper_mutex);
407
408         /* Make sure every nothing is still using the helper unless its a
409          * connection in the hash.
410          */
411         synchronize_rcu();
412
413         rtnl_lock();
414         spin_lock_bh(&nf_conntrack_lock);
415         for_each_net(net)
416                 __nf_conntrack_helper_unregister(me, net);
417         spin_unlock_bh(&nf_conntrack_lock);
418         rtnl_unlock();
419 }
420 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
421
422 static struct nf_ct_ext_type helper_extend __read_mostly = {
423         .len    = sizeof(struct nf_conn_help),
424         .align  = __alignof__(struct nf_conn_help),
425         .id     = NF_CT_EXT_HELPER,
426 };
427
428 int nf_conntrack_helper_pernet_init(struct net *net)
429 {
430         net->ct.auto_assign_helper_warned = false;
431         net->ct.sysctl_auto_assign_helper = nf_ct_auto_assign_helper;
432         return nf_conntrack_helper_init_sysctl(net);
433 }
434
435 void nf_conntrack_helper_pernet_fini(struct net *net)
436 {
437         nf_conntrack_helper_fini_sysctl(net);
438 }
439
440 int nf_conntrack_helper_init(void)
441 {
442         int ret;
443         nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
444         nf_ct_helper_hash =
445                 nf_ct_alloc_hashtable(&nf_ct_helper_hsize, 0);
446         if (!nf_ct_helper_hash)
447                 return -ENOMEM;
448
449         ret = nf_ct_extend_register(&helper_extend);
450         if (ret < 0) {
451                 pr_err("nf_ct_helper: Unable to register helper extension.\n");
452                 goto out_extend;
453         }
454
455         return 0;
456 out_extend:
457         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize);
458         return ret;
459 }
460
461 void nf_conntrack_helper_fini(void)
462 {
463         nf_ct_extend_unregister(&helper_extend);
464         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize);
465 }