1// SPDX-License-Identifier: GPL-2.0-only
2/* Helper handling for netfilter. */
3
4/* (C) 1999-2001 Paul `Rusty' Russell
5 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
6 * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
7 * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
8 */
9
10#include <linux/types.h>
11#include <linux/netfilter.h>
12#include <linux/module.h>
13#include <linux/skbuff.h>
14#include <linux/vmalloc.h>
15#include <linux/stddef.h>
16#include <linux/random.h>
17#include <linux/err.h>
18#include <linux/kernel.h>
19#include <linux/netdevice.h>
20#include <linux/rculist.h>
21#include <linux/rtnetlink.h>
22
23#include <net/netfilter/nf_conntrack.h>
24#include <net/netfilter/nf_conntrack_core.h>
25#include <net/netfilter/nf_conntrack_ecache.h>
26#include <net/netfilter/nf_conntrack_extend.h>
27#include <net/netfilter/nf_conntrack_helper.h>
28#include <net/netfilter/nf_conntrack_l4proto.h>
29#include <net/netfilter/nf_conntrack_seqadj.h>
30#include <net/netfilter/nf_log.h>
31#include <net/ip.h>
32
33static DEFINE_MUTEX(nf_ct_helper_mutex);
34struct hlist_head *nf_ct_helper_hash __read_mostly;
35EXPORT_SYMBOL_GPL(nf_ct_helper_hash);
36unsigned int nf_ct_helper_hsize __read_mostly;
37EXPORT_SYMBOL_GPL(nf_ct_helper_hsize);
38static unsigned int nf_ct_helper_count __read_mostly;
39
40static DEFINE_MUTEX(nf_ct_nat_helpers_mutex);
41static struct list_head nf_ct_nat_helpers __read_mostly;
42
43/* Stupid hash, but collision free for the default registrations of the
44 * helpers currently in the kernel. */
45static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
46{
47 return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
48 (__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
49}
50
51struct nf_conntrack_helper *
52__nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum)
53{
54 struct nf_conntrack_helper *h;
55 unsigned int i;
56
57 for (i = 0; i < nf_ct_helper_hsize; i++) {
58 hlist_for_each_entry_rcu(h, &nf_ct_helper_hash[i], hnode) {
59 if (strcmp(h->name, name))
60 continue;
61
62 if (h->tuple.src.l3num != NFPROTO_UNSPEC &&
63 h->tuple.src.l3num != l3num)
64 continue;
65
66 if (h->tuple.dst.protonum == protonum)
67 return h;
68 }
69 }
70 return NULL;
71}
72EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find);
73
74struct nf_conntrack_helper *
75nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
76{
77 struct nf_conntrack_helper *h;
78
79 rcu_read_lock();
80
81 h = __nf_conntrack_helper_find(name, l3num, protonum);
82#ifdef CONFIG_MODULES
83 if (h == NULL) {
84 rcu_read_unlock();
85 if (request_module("nfct-helper-%s", name) == 0) {
86 rcu_read_lock();
87 h = __nf_conntrack_helper_find(name, l3num, protonum);
88 } else {
89 return h;
90 }
91 }
92#endif
93 if (h != NULL && !try_module_get(module: h->me))
94 h = NULL;
95 if (h != NULL && !refcount_inc_not_zero(r: &h->refcnt)) {
96 module_put(module: h->me);
97 h = NULL;
98 }
99
100 rcu_read_unlock();
101
102 return h;
103}
104EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);
105
106void nf_conntrack_helper_put(struct nf_conntrack_helper *helper)
107{
108 refcount_dec(r: &helper->refcnt);
109 module_put(module: helper->me);
110}
111EXPORT_SYMBOL_GPL(nf_conntrack_helper_put);
112
113static struct nf_conntrack_nat_helper *
114nf_conntrack_nat_helper_find(const char *mod_name)
115{
116 struct nf_conntrack_nat_helper *cur;
117 bool found = false;
118
119 list_for_each_entry_rcu(cur, &nf_ct_nat_helpers, list) {
120 if (!strcmp(cur->mod_name, mod_name)) {
121 found = true;
122 break;
123 }
124 }
125 return found ? cur : NULL;
126}
127
128int
129nf_nat_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
130{
131 struct nf_conntrack_helper *h;
132 struct nf_conntrack_nat_helper *nat;
133 char mod_name[NF_CT_HELPER_NAME_LEN];
134 int ret = 0;
135
136 rcu_read_lock();
137 h = __nf_conntrack_helper_find(name, l3num, protonum);
138 if (!h) {
139 rcu_read_unlock();
140 return -ENOENT;
141 }
142
143 nat = nf_conntrack_nat_helper_find(mod_name: h->nat_mod_name);
144 if (!nat) {
145 snprintf(buf: mod_name, size: sizeof(mod_name), fmt: "%s", h->nat_mod_name);
146 rcu_read_unlock();
147 request_module("%s", mod_name);
148
149 rcu_read_lock();
150 nat = nf_conntrack_nat_helper_find(mod_name);
151 if (!nat) {
152 rcu_read_unlock();
153 return -ENOENT;
154 }
155 }
156
157 if (!try_module_get(module: nat->module))
158 ret = -ENOENT;
159
160 rcu_read_unlock();
161 return ret;
162}
163EXPORT_SYMBOL_GPL(nf_nat_helper_try_module_get);
164
165void nf_nat_helper_put(struct nf_conntrack_helper *helper)
166{
167 struct nf_conntrack_nat_helper *nat;
168
169 nat = nf_conntrack_nat_helper_find(mod_name: helper->nat_mod_name);
170 if (WARN_ON_ONCE(!nat))
171 return;
172
173 module_put(module: nat->module);
174}
175EXPORT_SYMBOL_GPL(nf_nat_helper_put);
176
177struct nf_conn_help *
178nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
179{
180 struct nf_conn_help *help;
181
182 help = nf_ct_ext_add(ct, id: NF_CT_EXT_HELPER, gfp);
183 if (help)
184 INIT_HLIST_HEAD(&help->expectations);
185 else
186 pr_debug("failed to add helper extension area");
187 return help;
188}
189EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
190
191int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
192 gfp_t flags)
193{
194 struct nf_conntrack_helper *helper = NULL;
195 struct nf_conn_help *help;
196
197 /* We already got a helper explicitly attached (e.g. nft_ct) */
198 if (test_bit(IPS_HELPER_BIT, &ct->status))
199 return 0;
200
201 if (WARN_ON_ONCE(!tmpl))
202 return 0;
203
204 help = nfct_help(ct: tmpl);
205 if (help != NULL) {
206 helper = rcu_dereference(help->helper);
207 set_bit(nr: IPS_HELPER_BIT, addr: &ct->status);
208 }
209
210 help = nfct_help(ct);
211
212 if (helper == NULL) {
213 if (help)
214 RCU_INIT_POINTER(help->helper, NULL);
215 return 0;
216 }
217
218 if (help == NULL) {
219 help = nf_ct_helper_ext_add(ct, flags);
220 if (help == NULL)
221 return -ENOMEM;
222 } else {
223 /* We only allow helper re-assignment of the same sort since
224 * we cannot reallocate the helper extension area.
225 */
226 struct nf_conntrack_helper *tmp = rcu_dereference(help->helper);
227
228 if (tmp && tmp->help != helper->help) {
229 RCU_INIT_POINTER(help->helper, NULL);
230 return 0;
231 }
232 }
233
234 rcu_assign_pointer(help->helper, helper);
235
236 return 0;
237}
238EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
239
240/* appropriate ct lock protecting must be taken by caller */
241static int unhelp(struct nf_conn *ct, void *me)
242{
243 struct nf_conn_help *help = nfct_help(ct);
244
245 if (help && rcu_dereference_raw(help->helper) == me) {
246 nf_conntrack_event(event: IPCT_HELPER, ct);
247 RCU_INIT_POINTER(help->helper, NULL);
248 }
249
250 /* We are not intended to delete this conntrack. */
251 return 0;
252}
253
254void nf_ct_helper_destroy(struct nf_conn *ct)
255{
256 struct nf_conn_help *help = nfct_help(ct);
257 struct nf_conntrack_helper *helper;
258
259 if (help) {
260 rcu_read_lock();
261 helper = rcu_dereference(help->helper);
262 if (helper && helper->destroy)
263 helper->destroy(ct);
264 rcu_read_unlock();
265 }
266}
267
268static LIST_HEAD(nf_ct_helper_expectfn_list);
269
270void nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn *n)
271{
272 spin_lock_bh(lock: &nf_conntrack_expect_lock);
273 list_add_rcu(new: &n->head, head: &nf_ct_helper_expectfn_list);
274 spin_unlock_bh(lock: &nf_conntrack_expect_lock);
275}
276EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_register);
277
278void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn *n)
279{
280 spin_lock_bh(lock: &nf_conntrack_expect_lock);
281 list_del_rcu(entry: &n->head);
282 spin_unlock_bh(lock: &nf_conntrack_expect_lock);
283}
284EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_unregister);
285
286/* Caller should hold the rcu lock */
287struct nf_ct_helper_expectfn *
288nf_ct_helper_expectfn_find_by_name(const char *name)
289{
290 struct nf_ct_helper_expectfn *cur;
291 bool found = false;
292
293 list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
294 if (!strcmp(cur->name, name)) {
295 found = true;
296 break;
297 }
298 }
299 return found ? cur : NULL;
300}
301EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name);
302
303/* Caller should hold the rcu lock */
304struct nf_ct_helper_expectfn *
305nf_ct_helper_expectfn_find_by_symbol(const void *symbol)
306{
307 struct nf_ct_helper_expectfn *cur;
308 bool found = false;
309
310 list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
311 if (cur->expectfn == symbol) {
312 found = true;
313 break;
314 }
315 }
316 return found ? cur : NULL;
317}
318EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_symbol);
319
320__printf(3, 4)
321void nf_ct_helper_log(struct sk_buff *skb, const struct nf_conn *ct,
322 const char *fmt, ...)
323{
324 const struct nf_conn_help *help;
325 const struct nf_conntrack_helper *helper;
326 struct va_format vaf;
327 va_list args;
328
329 va_start(args, fmt);
330
331 vaf.fmt = fmt;
332 vaf.va = &args;
333
334 /* Called from the helper function, this call never fails */
335 help = nfct_help(ct);
336
337 /* rcu_read_lock()ed by nf_hook_thresh */
338 helper = rcu_dereference(help->helper);
339
340 nf_log_packet(net: nf_ct_net(ct), pf: nf_ct_l3num(ct), hooknum: 0, skb, NULL, NULL, NULL,
341 fmt: "nf_ct_%s: dropping packet: %pV ", helper->name, &vaf);
342
343 va_end(args);
344}
345EXPORT_SYMBOL_GPL(nf_ct_helper_log);
346
347int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
348{
349 struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
350 unsigned int h = helper_hash(tuple: &me->tuple);
351 struct nf_conntrack_helper *cur;
352 int ret = 0, i;
353
354 BUG_ON(me->expect_policy == NULL);
355 BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
356 BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
357
358 if (!nf_ct_helper_hash)
359 return -ENOENT;
360
361 if (me->expect_policy->max_expected > NF_CT_EXPECT_MAX_CNT)
362 return -EINVAL;
363
364 mutex_lock(lock: &nf_ct_helper_mutex);
365 for (i = 0; i < nf_ct_helper_hsize; i++) {
366 hlist_for_each_entry(cur, &nf_ct_helper_hash[i], hnode) {
367 if (!strcmp(cur->name, me->name) &&
368 (cur->tuple.src.l3num == NFPROTO_UNSPEC ||
369 cur->tuple.src.l3num == me->tuple.src.l3num) &&
370 cur->tuple.dst.protonum == me->tuple.dst.protonum) {
371 ret = -EBUSY;
372 goto out;
373 }
374 }
375 }
376
377 /* avoid unpredictable behaviour for auto_assign_helper */
378 if (!(me->flags & NF_CT_HELPER_F_USERSPACE)) {
379 hlist_for_each_entry(cur, &nf_ct_helper_hash[h], hnode) {
380 if (nf_ct_tuple_src_mask_cmp(t1: &cur->tuple, t2: &me->tuple,
381 mask: &mask)) {
382 ret = -EBUSY;
383 goto out;
384 }
385 }
386 }
387 refcount_set(r: &me->refcnt, n: 1);
388 hlist_add_head_rcu(n: &me->hnode, h: &nf_ct_helper_hash[h]);
389 nf_ct_helper_count++;
390out:
391 mutex_unlock(lock: &nf_ct_helper_mutex);
392 return ret;
393}
394EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
395
396static bool expect_iter_me(struct nf_conntrack_expect *exp, void *data)
397{
398 struct nf_conn_help *help = nfct_help(ct: exp->master);
399 const struct nf_conntrack_helper *me = data;
400 const struct nf_conntrack_helper *this;
401
402 if (exp->helper == me)
403 return true;
404
405 this = rcu_dereference_protected(help->helper,
406 lockdep_is_held(&nf_conntrack_expect_lock));
407 return this == me;
408}
409
410void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
411{
412 mutex_lock(lock: &nf_ct_helper_mutex);
413 hlist_del_rcu(n: &me->hnode);
414 nf_ct_helper_count--;
415 mutex_unlock(lock: &nf_ct_helper_mutex);
416
417 /* Make sure every nothing is still using the helper unless its a
418 * connection in the hash.
419 */
420 synchronize_rcu();
421
422 nf_ct_expect_iterate_destroy(iter: expect_iter_me, NULL);
423 nf_ct_iterate_destroy(iter: unhelp, data: me);
424}
425EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
426
427void nf_ct_helper_init(struct nf_conntrack_helper *helper,
428 u16 l3num, u16 protonum, const char *name,
429 u16 default_port, u16 spec_port, u32 id,
430 const struct nf_conntrack_expect_policy *exp_pol,
431 u32 expect_class_max,
432 int (*help)(struct sk_buff *skb, unsigned int protoff,
433 struct nf_conn *ct,
434 enum ip_conntrack_info ctinfo),
435 int (*from_nlattr)(struct nlattr *attr,
436 struct nf_conn *ct),
437 struct module *module)
438{
439 helper->tuple.src.l3num = l3num;
440 helper->tuple.dst.protonum = protonum;
441 helper->tuple.src.u.all = htons(spec_port);
442 helper->expect_policy = exp_pol;
443 helper->expect_class_max = expect_class_max;
444 helper->help = help;
445 helper->from_nlattr = from_nlattr;
446 helper->me = module;
447 snprintf(buf: helper->nat_mod_name, size: sizeof(helper->nat_mod_name),
448 NF_NAT_HELPER_PREFIX "%s", name);
449
450 if (spec_port == default_port)
451 snprintf(buf: helper->name, size: sizeof(helper->name), fmt: "%s", name);
452 else
453 snprintf(buf: helper->name, size: sizeof(helper->name), fmt: "%s-%u", name, id);
454}
455EXPORT_SYMBOL_GPL(nf_ct_helper_init);
456
457int nf_conntrack_helpers_register(struct nf_conntrack_helper *helper,
458 unsigned int n)
459{
460 unsigned int i;
461 int err = 0;
462
463 for (i = 0; i < n; i++) {
464 err = nf_conntrack_helper_register(&helper[i]);
465 if (err < 0)
466 goto err;
467 }
468
469 return err;
470err:
471 if (i > 0)
472 nf_conntrack_helpers_unregister(helper, i);
473 return err;
474}
475EXPORT_SYMBOL_GPL(nf_conntrack_helpers_register);
476
477void nf_conntrack_helpers_unregister(struct nf_conntrack_helper *helper,
478 unsigned int n)
479{
480 while (n-- > 0)
481 nf_conntrack_helper_unregister(&helper[n]);
482}
483EXPORT_SYMBOL_GPL(nf_conntrack_helpers_unregister);
484
485void nf_nat_helper_register(struct nf_conntrack_nat_helper *nat)
486{
487 mutex_lock(lock: &nf_ct_nat_helpers_mutex);
488 list_add_rcu(new: &nat->list, head: &nf_ct_nat_helpers);
489 mutex_unlock(lock: &nf_ct_nat_helpers_mutex);
490}
491EXPORT_SYMBOL_GPL(nf_nat_helper_register);
492
493void nf_nat_helper_unregister(struct nf_conntrack_nat_helper *nat)
494{
495 mutex_lock(lock: &nf_ct_nat_helpers_mutex);
496 list_del_rcu(entry: &nat->list);
497 mutex_unlock(lock: &nf_ct_nat_helpers_mutex);
498}
499EXPORT_SYMBOL_GPL(nf_nat_helper_unregister);
500
501int nf_conntrack_helper_init(void)
502{
503 nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
504 nf_ct_helper_hash =
505 nf_ct_alloc_hashtable(sizep: &nf_ct_helper_hsize, nulls: 0);
506 if (!nf_ct_helper_hash)
507 return -ENOMEM;
508
509 INIT_LIST_HEAD(list: &nf_ct_nat_helpers);
510 return 0;
511}
512
513void nf_conntrack_helper_fini(void)
514{
515 kvfree(addr: nf_ct_helper_hash);
516 nf_ct_helper_hash = NULL;
517}
518