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_log.h>
30 
31 static DEFINE_MUTEX(nf_ct_helper_mutex);
32 struct hlist_head *nf_ct_helper_hash __read_mostly;
33 EXPORT_SYMBOL_GPL(nf_ct_helper_hash);
34 unsigned int nf_ct_helper_hsize __read_mostly;
35 EXPORT_SYMBOL_GPL(nf_ct_helper_hsize);
36 static unsigned int nf_ct_helper_count __read_mostly;
37 
38 static bool nf_ct_auto_assign_helper __read_mostly = false;
39 module_param_named(nf_conntrack_helper, nf_ct_auto_assign_helper, bool, 0644);
40 MODULE_PARM_DESC(nf_conntrack_helper,
41 		 "Enable automatic conntrack helper assignment (default 0)");
42 
43 static DEFINE_MUTEX(nf_ct_nat_helpers_mutex);
44 static struct list_head nf_ct_nat_helpers __read_mostly;
45 
46 /* Stupid hash, but collision free for the default registrations of the
47  * helpers currently in the kernel. */
helper_hash(const struct nf_conntrack_tuple * tuple)48 static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
49 {
50 	return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
51 		(__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
52 }
53 
54 static struct nf_conntrack_helper *
__nf_ct_helper_find(const struct nf_conntrack_tuple * tuple)55 __nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
56 {
57 	struct nf_conntrack_helper *helper;
58 	struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
59 	unsigned int h;
60 
61 	if (!nf_ct_helper_count)
62 		return NULL;
63 
64 	h = helper_hash(tuple);
65 	hlist_for_each_entry_rcu(helper, &nf_ct_helper_hash[h], hnode) {
66 		if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
67 			return helper;
68 	}
69 	return NULL;
70 }
71 
72 struct nf_conntrack_helper *
__nf_conntrack_helper_find(const char * name,u16 l3num,u8 protonum)73 __nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum)
74 {
75 	struct nf_conntrack_helper *h;
76 	unsigned int i;
77 
78 	for (i = 0; i < nf_ct_helper_hsize; i++) {
79 		hlist_for_each_entry_rcu(h, &nf_ct_helper_hash[i], hnode) {
80 			if (strcmp(h->name, name))
81 				continue;
82 
83 			if (h->tuple.src.l3num != NFPROTO_UNSPEC &&
84 			    h->tuple.src.l3num != l3num)
85 				continue;
86 
87 			if (h->tuple.dst.protonum == protonum)
88 				return h;
89 		}
90 	}
91 	return NULL;
92 }
93 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find);
94 
95 struct nf_conntrack_helper *
nf_conntrack_helper_try_module_get(const char * name,u16 l3num,u8 protonum)96 nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
97 {
98 	struct nf_conntrack_helper *h;
99 
100 	rcu_read_lock();
101 
102 	h = __nf_conntrack_helper_find(name, l3num, protonum);
103 #ifdef CONFIG_MODULES
104 	if (h == NULL) {
105 		rcu_read_unlock();
106 		if (request_module("nfct-helper-%s", name) == 0) {
107 			rcu_read_lock();
108 			h = __nf_conntrack_helper_find(name, l3num, protonum);
109 		} else {
110 			return h;
111 		}
112 	}
113 #endif
114 	if (h != NULL && !try_module_get(h->me))
115 		h = NULL;
116 	if (h != NULL && !refcount_inc_not_zero(&h->refcnt)) {
117 		module_put(h->me);
118 		h = NULL;
119 	}
120 
121 	rcu_read_unlock();
122 
123 	return h;
124 }
125 EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);
126 
nf_conntrack_helper_put(struct nf_conntrack_helper * helper)127 void nf_conntrack_helper_put(struct nf_conntrack_helper *helper)
128 {
129 	refcount_dec(&helper->refcnt);
130 	module_put(helper->me);
131 }
132 EXPORT_SYMBOL_GPL(nf_conntrack_helper_put);
133 
134 static struct nf_conntrack_nat_helper *
nf_conntrack_nat_helper_find(const char * mod_name)135 nf_conntrack_nat_helper_find(const char *mod_name)
136 {
137 	struct nf_conntrack_nat_helper *cur;
138 	bool found = false;
139 
140 	list_for_each_entry_rcu(cur, &nf_ct_nat_helpers, list) {
141 		if (!strcmp(cur->mod_name, mod_name)) {
142 			found = true;
143 			break;
144 		}
145 	}
146 	return found ? cur : NULL;
147 }
148 
149 int
nf_nat_helper_try_module_get(const char * name,u16 l3num,u8 protonum)150 nf_nat_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
151 {
152 	struct nf_conntrack_helper *h;
153 	struct nf_conntrack_nat_helper *nat;
154 	char mod_name[NF_CT_HELPER_NAME_LEN];
155 	int ret = 0;
156 
157 	rcu_read_lock();
158 	h = __nf_conntrack_helper_find(name, l3num, protonum);
159 	if (!h) {
160 		rcu_read_unlock();
161 		return -ENOENT;
162 	}
163 
164 	nat = nf_conntrack_nat_helper_find(h->nat_mod_name);
165 	if (!nat) {
166 		snprintf(mod_name, sizeof(mod_name), "%s", h->nat_mod_name);
167 		rcu_read_unlock();
168 		request_module(mod_name);
169 
170 		rcu_read_lock();
171 		nat = nf_conntrack_nat_helper_find(mod_name);
172 		if (!nat) {
173 			rcu_read_unlock();
174 			return -ENOENT;
175 		}
176 	}
177 
178 	if (!try_module_get(nat->module))
179 		ret = -ENOENT;
180 
181 	rcu_read_unlock();
182 	return ret;
183 }
184 EXPORT_SYMBOL_GPL(nf_nat_helper_try_module_get);
185 
nf_nat_helper_put(struct nf_conntrack_helper * helper)186 void nf_nat_helper_put(struct nf_conntrack_helper *helper)
187 {
188 	struct nf_conntrack_nat_helper *nat;
189 
190 	nat = nf_conntrack_nat_helper_find(helper->nat_mod_name);
191 	if (WARN_ON_ONCE(!nat))
192 		return;
193 
194 	module_put(nat->module);
195 }
196 EXPORT_SYMBOL_GPL(nf_nat_helper_put);
197 
198 struct nf_conn_help *
nf_ct_helper_ext_add(struct nf_conn * ct,gfp_t gfp)199 nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
200 {
201 	struct nf_conn_help *help;
202 
203 	help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
204 	if (help)
205 		INIT_HLIST_HEAD(&help->expectations);
206 	else
207 		pr_debug("failed to add helper extension area");
208 	return help;
209 }
210 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
211 
212 static struct nf_conntrack_helper *
nf_ct_lookup_helper(struct nf_conn * ct,struct net * net)213 nf_ct_lookup_helper(struct nf_conn *ct, struct net *net)
214 {
215 	struct nf_conntrack_net *cnet = nf_ct_pernet(net);
216 
217 	if (!cnet->sysctl_auto_assign_helper) {
218 		if (cnet->auto_assign_helper_warned)
219 			return NULL;
220 		if (!__nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple))
221 			return NULL;
222 		pr_info("nf_conntrack: default automatic helper assignment "
223 			"has been turned off for security reasons and CT-based "
224 			"firewall rule not found. Use the iptables CT target "
225 			"to attach helpers instead.\n");
226 		cnet->auto_assign_helper_warned = true;
227 		return NULL;
228 	}
229 
230 	return __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
231 }
232 
__nf_ct_try_assign_helper(struct nf_conn * ct,struct nf_conn * tmpl,gfp_t flags)233 int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
234 			      gfp_t flags)
235 {
236 	struct nf_conntrack_helper *helper = NULL;
237 	struct nf_conn_help *help;
238 	struct net *net = nf_ct_net(ct);
239 
240 	/* We already got a helper explicitly attached. The function
241 	 * nf_conntrack_alter_reply - in case NAT is in use - asks for looking
242 	 * the helper up again. Since now the user is in full control of
243 	 * making consistent helper configurations, skip this automatic
244 	 * re-lookup, otherwise we'll lose the helper.
245 	 */
246 	if (test_bit(IPS_HELPER_BIT, &ct->status))
247 		return 0;
248 
249 	if (tmpl != NULL) {
250 		help = nfct_help(tmpl);
251 		if (help != NULL) {
252 			helper = help->helper;
253 			set_bit(IPS_HELPER_BIT, &ct->status);
254 		}
255 	}
256 
257 	help = nfct_help(ct);
258 
259 	if (helper == NULL) {
260 		helper = nf_ct_lookup_helper(ct, net);
261 		if (helper == NULL) {
262 			if (help)
263 				RCU_INIT_POINTER(help->helper, NULL);
264 			return 0;
265 		}
266 	}
267 
268 	if (help == NULL) {
269 		help = nf_ct_helper_ext_add(ct, flags);
270 		if (help == NULL)
271 			return -ENOMEM;
272 	} else {
273 		/* We only allow helper re-assignment of the same sort since
274 		 * we cannot reallocate the helper extension area.
275 		 */
276 		struct nf_conntrack_helper *tmp = rcu_dereference(help->helper);
277 
278 		if (tmp && tmp->help != helper->help) {
279 			RCU_INIT_POINTER(help->helper, NULL);
280 			return 0;
281 		}
282 	}
283 
284 	rcu_assign_pointer(help->helper, helper);
285 
286 	return 0;
287 }
288 EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
289 
290 /* appropriate ct lock protecting must be taken by caller */
unhelp(struct nf_conn * ct,void * me)291 static int unhelp(struct nf_conn *ct, void *me)
292 {
293 	struct nf_conn_help *help = nfct_help(ct);
294 
295 	if (help && rcu_dereference_raw(help->helper) == me) {
296 		nf_conntrack_event(IPCT_HELPER, ct);
297 		RCU_INIT_POINTER(help->helper, NULL);
298 	}
299 
300 	/* We are not intended to delete this conntrack. */
301 	return 0;
302 }
303 
nf_ct_helper_destroy(struct nf_conn * ct)304 void nf_ct_helper_destroy(struct nf_conn *ct)
305 {
306 	struct nf_conn_help *help = nfct_help(ct);
307 	struct nf_conntrack_helper *helper;
308 
309 	if (help) {
310 		rcu_read_lock();
311 		helper = rcu_dereference(help->helper);
312 		if (helper && helper->destroy)
313 			helper->destroy(ct);
314 		rcu_read_unlock();
315 	}
316 }
317 
318 static LIST_HEAD(nf_ct_helper_expectfn_list);
319 
nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn * n)320 void nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn *n)
321 {
322 	spin_lock_bh(&nf_conntrack_expect_lock);
323 	list_add_rcu(&n->head, &nf_ct_helper_expectfn_list);
324 	spin_unlock_bh(&nf_conntrack_expect_lock);
325 }
326 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_register);
327 
nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn * n)328 void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn *n)
329 {
330 	spin_lock_bh(&nf_conntrack_expect_lock);
331 	list_del_rcu(&n->head);
332 	spin_unlock_bh(&nf_conntrack_expect_lock);
333 }
334 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_unregister);
335 
336 /* Caller should hold the rcu lock */
337 struct nf_ct_helper_expectfn *
nf_ct_helper_expectfn_find_by_name(const char * name)338 nf_ct_helper_expectfn_find_by_name(const char *name)
339 {
340 	struct nf_ct_helper_expectfn *cur;
341 	bool found = false;
342 
343 	list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
344 		if (!strcmp(cur->name, name)) {
345 			found = true;
346 			break;
347 		}
348 	}
349 	return found ? cur : NULL;
350 }
351 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name);
352 
353 /* Caller should hold the rcu lock */
354 struct nf_ct_helper_expectfn *
nf_ct_helper_expectfn_find_by_symbol(const void * symbol)355 nf_ct_helper_expectfn_find_by_symbol(const void *symbol)
356 {
357 	struct nf_ct_helper_expectfn *cur;
358 	bool found = false;
359 
360 	list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
361 		if (cur->expectfn == symbol) {
362 			found = true;
363 			break;
364 		}
365 	}
366 	return found ? cur : NULL;
367 }
368 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_symbol);
369 
370 __printf(3, 4)
nf_ct_helper_log(struct sk_buff * skb,const struct nf_conn * ct,const char * fmt,...)371 void nf_ct_helper_log(struct sk_buff *skb, const struct nf_conn *ct,
372 		      const char *fmt, ...)
373 {
374 	const struct nf_conn_help *help;
375 	const struct nf_conntrack_helper *helper;
376 	struct va_format vaf;
377 	va_list args;
378 
379 	va_start(args, fmt);
380 
381 	vaf.fmt = fmt;
382 	vaf.va = &args;
383 
384 	/* Called from the helper function, this call never fails */
385 	help = nfct_help(ct);
386 
387 	/* rcu_read_lock()ed by nf_hook_thresh */
388 	helper = rcu_dereference(help->helper);
389 
390 	nf_log_packet(nf_ct_net(ct), nf_ct_l3num(ct), 0, skb, NULL, NULL, NULL,
391 		      "nf_ct_%s: dropping packet: %pV ", helper->name, &vaf);
392 
393 	va_end(args);
394 }
395 EXPORT_SYMBOL_GPL(nf_ct_helper_log);
396 
nf_conntrack_helper_register(struct nf_conntrack_helper * me)397 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
398 {
399 	struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
400 	unsigned int h = helper_hash(&me->tuple);
401 	struct nf_conntrack_helper *cur;
402 	int ret = 0, i;
403 
404 	BUG_ON(me->expect_policy == NULL);
405 	BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
406 	BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
407 
408 	if (me->expect_policy->max_expected > NF_CT_EXPECT_MAX_CNT)
409 		return -EINVAL;
410 
411 	mutex_lock(&nf_ct_helper_mutex);
412 	for (i = 0; i < nf_ct_helper_hsize; i++) {
413 		hlist_for_each_entry(cur, &nf_ct_helper_hash[i], hnode) {
414 			if (!strcmp(cur->name, me->name) &&
415 			    (cur->tuple.src.l3num == NFPROTO_UNSPEC ||
416 			     cur->tuple.src.l3num == me->tuple.src.l3num) &&
417 			    cur->tuple.dst.protonum == me->tuple.dst.protonum) {
418 				ret = -EEXIST;
419 				goto out;
420 			}
421 		}
422 	}
423 
424 	/* avoid unpredictable behaviour for auto_assign_helper */
425 	if (!(me->flags & NF_CT_HELPER_F_USERSPACE)) {
426 		hlist_for_each_entry(cur, &nf_ct_helper_hash[h], hnode) {
427 			if (nf_ct_tuple_src_mask_cmp(&cur->tuple, &me->tuple,
428 						     &mask)) {
429 				ret = -EEXIST;
430 				goto out;
431 			}
432 		}
433 	}
434 	refcount_set(&me->refcnt, 1);
435 	hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
436 	nf_ct_helper_count++;
437 out:
438 	mutex_unlock(&nf_ct_helper_mutex);
439 	return ret;
440 }
441 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
442 
expect_iter_me(struct nf_conntrack_expect * exp,void * data)443 static bool expect_iter_me(struct nf_conntrack_expect *exp, void *data)
444 {
445 	struct nf_conn_help *help = nfct_help(exp->master);
446 	const struct nf_conntrack_helper *me = data;
447 	const struct nf_conntrack_helper *this;
448 
449 	if (exp->helper == me)
450 		return true;
451 
452 	this = rcu_dereference_protected(help->helper,
453 					 lockdep_is_held(&nf_conntrack_expect_lock));
454 	return this == me;
455 }
456 
nf_conntrack_helper_unregister(struct nf_conntrack_helper * me)457 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
458 {
459 	mutex_lock(&nf_ct_helper_mutex);
460 	hlist_del_rcu(&me->hnode);
461 	nf_ct_helper_count--;
462 	mutex_unlock(&nf_ct_helper_mutex);
463 
464 	/* Make sure every nothing is still using the helper unless its a
465 	 * connection in the hash.
466 	 */
467 	synchronize_rcu();
468 
469 	nf_ct_expect_iterate_destroy(expect_iter_me, NULL);
470 	nf_ct_iterate_destroy(unhelp, me);
471 
472 	/* Maybe someone has gotten the helper already when unhelp above.
473 	 * So need to wait it.
474 	 */
475 	synchronize_rcu();
476 }
477 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
478 
nf_ct_helper_init(struct nf_conntrack_helper * helper,u16 l3num,u16 protonum,const char * name,u16 default_port,u16 spec_port,u32 id,const struct nf_conntrack_expect_policy * exp_pol,u32 expect_class_max,int (* help)(struct sk_buff * skb,unsigned int protoff,struct nf_conn * ct,enum ip_conntrack_info ctinfo),int (* from_nlattr)(struct nlattr * attr,struct nf_conn * ct),struct module * module)479 void nf_ct_helper_init(struct nf_conntrack_helper *helper,
480 		       u16 l3num, u16 protonum, const char *name,
481 		       u16 default_port, u16 spec_port, u32 id,
482 		       const struct nf_conntrack_expect_policy *exp_pol,
483 		       u32 expect_class_max,
484 		       int (*help)(struct sk_buff *skb, unsigned int protoff,
485 				   struct nf_conn *ct,
486 				   enum ip_conntrack_info ctinfo),
487 		       int (*from_nlattr)(struct nlattr *attr,
488 					  struct nf_conn *ct),
489 		       struct module *module)
490 {
491 	helper->tuple.src.l3num = l3num;
492 	helper->tuple.dst.protonum = protonum;
493 	helper->tuple.src.u.all = htons(spec_port);
494 	helper->expect_policy = exp_pol;
495 	helper->expect_class_max = expect_class_max;
496 	helper->help = help;
497 	helper->from_nlattr = from_nlattr;
498 	helper->me = module;
499 	snprintf(helper->nat_mod_name, sizeof(helper->nat_mod_name),
500 		 NF_NAT_HELPER_PREFIX "%s", name);
501 
502 	if (spec_port == default_port)
503 		snprintf(helper->name, sizeof(helper->name), "%s", name);
504 	else
505 		snprintf(helper->name, sizeof(helper->name), "%s-%u", name, id);
506 }
507 EXPORT_SYMBOL_GPL(nf_ct_helper_init);
508 
nf_conntrack_helpers_register(struct nf_conntrack_helper * helper,unsigned int n)509 int nf_conntrack_helpers_register(struct nf_conntrack_helper *helper,
510 				  unsigned int n)
511 {
512 	unsigned int i;
513 	int err = 0;
514 
515 	for (i = 0; i < n; i++) {
516 		err = nf_conntrack_helper_register(&helper[i]);
517 		if (err < 0)
518 			goto err;
519 	}
520 
521 	return err;
522 err:
523 	if (i > 0)
524 		nf_conntrack_helpers_unregister(helper, i);
525 	return err;
526 }
527 EXPORT_SYMBOL_GPL(nf_conntrack_helpers_register);
528 
nf_conntrack_helpers_unregister(struct nf_conntrack_helper * helper,unsigned int n)529 void nf_conntrack_helpers_unregister(struct nf_conntrack_helper *helper,
530 				unsigned int n)
531 {
532 	while (n-- > 0)
533 		nf_conntrack_helper_unregister(&helper[n]);
534 }
535 EXPORT_SYMBOL_GPL(nf_conntrack_helpers_unregister);
536 
nf_nat_helper_register(struct nf_conntrack_nat_helper * nat)537 void nf_nat_helper_register(struct nf_conntrack_nat_helper *nat)
538 {
539 	mutex_lock(&nf_ct_nat_helpers_mutex);
540 	list_add_rcu(&nat->list, &nf_ct_nat_helpers);
541 	mutex_unlock(&nf_ct_nat_helpers_mutex);
542 }
543 EXPORT_SYMBOL_GPL(nf_nat_helper_register);
544 
nf_nat_helper_unregister(struct nf_conntrack_nat_helper * nat)545 void nf_nat_helper_unregister(struct nf_conntrack_nat_helper *nat)
546 {
547 	mutex_lock(&nf_ct_nat_helpers_mutex);
548 	list_del_rcu(&nat->list);
549 	mutex_unlock(&nf_ct_nat_helpers_mutex);
550 }
551 EXPORT_SYMBOL_GPL(nf_nat_helper_unregister);
552 
553 static const struct nf_ct_ext_type helper_extend = {
554 	.len	= sizeof(struct nf_conn_help),
555 	.align	= __alignof__(struct nf_conn_help),
556 	.id	= NF_CT_EXT_HELPER,
557 };
558 
nf_conntrack_helper_pernet_init(struct net * net)559 void nf_conntrack_helper_pernet_init(struct net *net)
560 {
561 	struct nf_conntrack_net *cnet = nf_ct_pernet(net);
562 
563 	cnet->sysctl_auto_assign_helper = nf_ct_auto_assign_helper;
564 }
565 
nf_conntrack_helper_init(void)566 int nf_conntrack_helper_init(void)
567 {
568 	int ret;
569 	nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
570 	nf_ct_helper_hash =
571 		nf_ct_alloc_hashtable(&nf_ct_helper_hsize, 0);
572 	if (!nf_ct_helper_hash)
573 		return -ENOMEM;
574 
575 	ret = nf_ct_extend_register(&helper_extend);
576 	if (ret < 0) {
577 		pr_err("nf_ct_helper: Unable to register helper extension.\n");
578 		goto out_extend;
579 	}
580 
581 	INIT_LIST_HEAD(&nf_ct_nat_helpers);
582 	return 0;
583 out_extend:
584 	kvfree(nf_ct_helper_hash);
585 	return ret;
586 }
587 
nf_conntrack_helper_fini(void)588 void nf_conntrack_helper_fini(void)
589 {
590 	nf_ct_extend_unregister(&helper_extend);
591 	kvfree(nf_ct_helper_hash);
592 }
593