xref: /openbmc/linux/net/netfilter/nfnetlink.c (revision 11a163f2) 
1 /* Netfilter messages via netlink socket. Allows for user space
2  * protocol helpers and general trouble making from userspace.
3  *
4  * (C) 2001 by Jay Schulist <jschlst@samba.org>,
5  * (C) 2002-2005 by Harald Welte <laforge@gnumonks.org>
6  * (C) 2005-2017 by Pablo Neira Ayuso <pablo@netfilter.org>
7  *
8  * Initial netfilter messages via netlink development funded and
9  * generally made possible by Network Robots, Inc. (www.networkrobots.com)
10  *
11  * Further development of this code funded by Astaro AG (http://www.astaro.com)
12  *
13  * This software may be used and distributed according to the terms
14  * of the GNU General Public License, incorporated herein by reference.
15  */
16 
17 #include <linux/module.h>
18 #include <linux/types.h>
19 #include <linux/socket.h>
20 #include <linux/kernel.h>
21 #include <linux/string.h>
22 #include <linux/sockios.h>
23 #include <linux/net.h>
24 #include <linux/skbuff.h>
25 #include <linux/uaccess.h>
26 #include <net/sock.h>
27 #include <linux/init.h>
28 #include <linux/sched/signal.h>
29 
30 #include <net/netlink.h>
31 #include <linux/netfilter/nfnetlink.h>
32 
33 MODULE_LICENSE("GPL");
34 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
35 MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER);
36 MODULE_DESCRIPTION("Netfilter messages via netlink socket");
37 
38 #define nfnl_dereference_protected(id) \
39 	rcu_dereference_protected(table[(id)].subsys, \
40 				  lockdep_nfnl_is_held((id)))
41 
42 #define NFNL_MAX_ATTR_COUNT	32
43 
44 static struct {
45 	struct mutex				mutex;
46 	const struct nfnetlink_subsystem __rcu	*subsys;
47 } table[NFNL_SUBSYS_COUNT];
48 
49 static struct lock_class_key nfnl_lockdep_keys[NFNL_SUBSYS_COUNT];
50 
51 static const char *const nfnl_lockdep_names[NFNL_SUBSYS_COUNT] = {
52 	[NFNL_SUBSYS_NONE] = "nfnl_subsys_none",
53 	[NFNL_SUBSYS_CTNETLINK] = "nfnl_subsys_ctnetlink",
54 	[NFNL_SUBSYS_CTNETLINK_EXP] = "nfnl_subsys_ctnetlink_exp",
55 	[NFNL_SUBSYS_QUEUE] = "nfnl_subsys_queue",
56 	[NFNL_SUBSYS_ULOG] = "nfnl_subsys_ulog",
57 	[NFNL_SUBSYS_OSF] = "nfnl_subsys_osf",
58 	[NFNL_SUBSYS_IPSET] = "nfnl_subsys_ipset",
59 	[NFNL_SUBSYS_ACCT] = "nfnl_subsys_acct",
60 	[NFNL_SUBSYS_CTNETLINK_TIMEOUT] = "nfnl_subsys_cttimeout",
61 	[NFNL_SUBSYS_CTHELPER] = "nfnl_subsys_cthelper",
62 	[NFNL_SUBSYS_NFTABLES] = "nfnl_subsys_nftables",
63 	[NFNL_SUBSYS_NFT_COMPAT] = "nfnl_subsys_nftcompat",
64 };
65 
66 static const int nfnl_group2type[NFNLGRP_MAX+1] = {
67 	[NFNLGRP_CONNTRACK_NEW]		= NFNL_SUBSYS_CTNETLINK,
68 	[NFNLGRP_CONNTRACK_UPDATE]	= NFNL_SUBSYS_CTNETLINK,
69 	[NFNLGRP_CONNTRACK_DESTROY]	= NFNL_SUBSYS_CTNETLINK,
70 	[NFNLGRP_CONNTRACK_EXP_NEW]	= NFNL_SUBSYS_CTNETLINK_EXP,
71 	[NFNLGRP_CONNTRACK_EXP_UPDATE]	= NFNL_SUBSYS_CTNETLINK_EXP,
72 	[NFNLGRP_CONNTRACK_EXP_DESTROY] = NFNL_SUBSYS_CTNETLINK_EXP,
73 	[NFNLGRP_NFTABLES]		= NFNL_SUBSYS_NFTABLES,
74 	[NFNLGRP_ACCT_QUOTA]		= NFNL_SUBSYS_ACCT,
75 	[NFNLGRP_NFTRACE]		= NFNL_SUBSYS_NFTABLES,
76 };
77 
78 void nfnl_lock(__u8 subsys_id)
79 {
80 	mutex_lock(&table[subsys_id].mutex);
81 }
82 EXPORT_SYMBOL_GPL(nfnl_lock);
83 
84 void nfnl_unlock(__u8 subsys_id)
85 {
86 	mutex_unlock(&table[subsys_id].mutex);
87 }
88 EXPORT_SYMBOL_GPL(nfnl_unlock);
89 
90 #ifdef CONFIG_PROVE_LOCKING
91 bool lockdep_nfnl_is_held(u8 subsys_id)
92 {
93 	return lockdep_is_held(&table[subsys_id].mutex);
94 }
95 EXPORT_SYMBOL_GPL(lockdep_nfnl_is_held);
96 #endif
97 
98 int nfnetlink_subsys_register(const struct nfnetlink_subsystem *n)
99 {
100 	u8 cb_id;
101 
102 	/* Sanity-check attr_count size to avoid stack buffer overflow. */
103 	for (cb_id = 0; cb_id < n->cb_count; cb_id++)
104 		if (WARN_ON(n->cb[cb_id].attr_count > NFNL_MAX_ATTR_COUNT))
105 			return -EINVAL;
106 
107 	nfnl_lock(n->subsys_id);
108 	if (table[n->subsys_id].subsys) {
109 		nfnl_unlock(n->subsys_id);
110 		return -EBUSY;
111 	}
112 	rcu_assign_pointer(table[n->subsys_id].subsys, n);
113 	nfnl_unlock(n->subsys_id);
114 
115 	return 0;
116 }
117 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
118 
119 int nfnetlink_subsys_unregister(const struct nfnetlink_subsystem *n)
120 {
121 	nfnl_lock(n->subsys_id);
122 	table[n->subsys_id].subsys = NULL;
123 	nfnl_unlock(n->subsys_id);
124 	synchronize_rcu();
125 	return 0;
126 }
127 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
128 
129 static inline const struct nfnetlink_subsystem *nfnetlink_get_subsys(u16 type)
130 {
131 	u8 subsys_id = NFNL_SUBSYS_ID(type);
132 
133 	if (subsys_id >= NFNL_SUBSYS_COUNT)
134 		return NULL;
135 
136 	return rcu_dereference(table[subsys_id].subsys);
137 }
138 
139 static inline const struct nfnl_callback *
140 nfnetlink_find_client(u16 type, const struct nfnetlink_subsystem *ss)
141 {
142 	u8 cb_id = NFNL_MSG_TYPE(type);
143 
144 	if (cb_id >= ss->cb_count)
145 		return NULL;
146 
147 	return &ss->cb[cb_id];
148 }
149 
150 int nfnetlink_has_listeners(struct net *net, unsigned int group)
151 {
152 	return netlink_has_listeners(net->nfnl, group);
153 }
154 EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
155 
156 int nfnetlink_send(struct sk_buff *skb, struct net *net, u32 portid,
157 		   unsigned int group, int echo, gfp_t flags)
158 {
159 	return nlmsg_notify(net->nfnl, skb, portid, group, echo, flags);
160 }
161 EXPORT_SYMBOL_GPL(nfnetlink_send);
162 
163 int nfnetlink_set_err(struct net *net, u32 portid, u32 group, int error)
164 {
165 	return netlink_set_err(net->nfnl, portid, group, error);
166 }
167 EXPORT_SYMBOL_GPL(nfnetlink_set_err);
168 
169 int nfnetlink_unicast(struct sk_buff *skb, struct net *net, u32 portid)
170 {
171 	int err;
172 
173 	err = nlmsg_unicast(net->nfnl, skb, portid);
174 	if (err == -EAGAIN)
175 		err = -ENOBUFS;
176 
177 	return err;
178 }
179 EXPORT_SYMBOL_GPL(nfnetlink_unicast);
180 
181 /* Process one complete nfnetlink message. */
182 static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
183 			     struct netlink_ext_ack *extack)
184 {
185 	struct net *net = sock_net(skb->sk);
186 	const struct nfnl_callback *nc;
187 	const struct nfnetlink_subsystem *ss;
188 	int type, err;
189 
190 	/* All the messages must at least contain nfgenmsg */
191 	if (nlmsg_len(nlh) < sizeof(struct nfgenmsg))
192 		return 0;
193 
194 	type = nlh->nlmsg_type;
195 replay:
196 	rcu_read_lock();
197 	ss = nfnetlink_get_subsys(type);
198 	if (!ss) {
199 #ifdef CONFIG_MODULES
200 		rcu_read_unlock();
201 		request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
202 		rcu_read_lock();
203 		ss = nfnetlink_get_subsys(type);
204 		if (!ss)
205 #endif
206 		{
207 			rcu_read_unlock();
208 			return -EINVAL;
209 		}
210 	}
211 
212 	nc = nfnetlink_find_client(type, ss);
213 	if (!nc) {
214 		rcu_read_unlock();
215 		return -EINVAL;
216 	}
217 
218 	{
219 		int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
220 		u8 cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
221 		struct nlattr *cda[NFNL_MAX_ATTR_COUNT + 1];
222 		struct nlattr *attr = (void *)nlh + min_len;
223 		int attrlen = nlh->nlmsg_len - min_len;
224 		__u8 subsys_id = NFNL_SUBSYS_ID(type);
225 
226 		/* Sanity-check NFNL_MAX_ATTR_COUNT */
227 		if (ss->cb[cb_id].attr_count > NFNL_MAX_ATTR_COUNT) {
228 			rcu_read_unlock();
229 			return -ENOMEM;
230 		}
231 
232 		err = nla_parse_deprecated(cda, ss->cb[cb_id].attr_count,
233 					   attr, attrlen,
234 					   ss->cb[cb_id].policy, extack);
235 		if (err < 0) {
236 			rcu_read_unlock();
237 			return err;
238 		}
239 
240 		if (nc->call_rcu) {
241 			err = nc->call_rcu(net, net->nfnl, skb, nlh,
242 					   (const struct nlattr **)cda,
243 					   extack);
244 			rcu_read_unlock();
245 		} else {
246 			rcu_read_unlock();
247 			nfnl_lock(subsys_id);
248 			if (nfnl_dereference_protected(subsys_id) != ss ||
249 			    nfnetlink_find_client(type, ss) != nc)
250 				err = -EAGAIN;
251 			else if (nc->call)
252 				err = nc->call(net, net->nfnl, skb, nlh,
253 					       (const struct nlattr **)cda,
254 					       extack);
255 			else
256 				err = -EINVAL;
257 			nfnl_unlock(subsys_id);
258 		}
259 		if (err == -EAGAIN)
260 			goto replay;
261 		return err;
262 	}
263 }
264 
265 struct nfnl_err {
266 	struct list_head	head;
267 	struct nlmsghdr		*nlh;
268 	int			err;
269 	struct netlink_ext_ack	extack;
270 };
271 
272 static int nfnl_err_add(struct list_head *list, struct nlmsghdr *nlh, int err,
273 			const struct netlink_ext_ack *extack)
274 {
275 	struct nfnl_err *nfnl_err;
276 
277 	nfnl_err = kmalloc(sizeof(struct nfnl_err), GFP_KERNEL);
278 	if (nfnl_err == NULL)
279 		return -ENOMEM;
280 
281 	nfnl_err->nlh = nlh;
282 	nfnl_err->err = err;
283 	nfnl_err->extack = *extack;
284 	list_add_tail(&nfnl_err->head, list);
285 
286 	return 0;
287 }
288 
289 static void nfnl_err_del(struct nfnl_err *nfnl_err)
290 {
291 	list_del(&nfnl_err->head);
292 	kfree(nfnl_err);
293 }
294 
295 static void nfnl_err_reset(struct list_head *err_list)
296 {
297 	struct nfnl_err *nfnl_err, *next;
298 
299 	list_for_each_entry_safe(nfnl_err, next, err_list, head)
300 		nfnl_err_del(nfnl_err);
301 }
302 
303 static void nfnl_err_deliver(struct list_head *err_list, struct sk_buff *skb)
304 {
305 	struct nfnl_err *nfnl_err, *next;
306 
307 	list_for_each_entry_safe(nfnl_err, next, err_list, head) {
308 		netlink_ack(skb, nfnl_err->nlh, nfnl_err->err,
309 			    &nfnl_err->extack);
310 		nfnl_err_del(nfnl_err);
311 	}
312 }
313 
314 enum {
315 	NFNL_BATCH_FAILURE	= (1 << 0),
316 	NFNL_BATCH_DONE		= (1 << 1),
317 	NFNL_BATCH_REPLAY	= (1 << 2),
318 };
319 
320 static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh,
321 				u16 subsys_id, u32 genid)
322 {
323 	struct sk_buff *oskb = skb;
324 	struct net *net = sock_net(skb->sk);
325 	const struct nfnetlink_subsystem *ss;
326 	const struct nfnl_callback *nc;
327 	struct netlink_ext_ack extack;
328 	LIST_HEAD(err_list);
329 	u32 status;
330 	int err;
331 
332 	if (subsys_id >= NFNL_SUBSYS_COUNT)
333 		return netlink_ack(skb, nlh, -EINVAL, NULL);
334 replay:
335 	status = 0;
336 
337 	skb = netlink_skb_clone(oskb, GFP_KERNEL);
338 	if (!skb)
339 		return netlink_ack(oskb, nlh, -ENOMEM, NULL);
340 
341 	nfnl_lock(subsys_id);
342 	ss = nfnl_dereference_protected(subsys_id);
343 	if (!ss) {
344 #ifdef CONFIG_MODULES
345 		nfnl_unlock(subsys_id);
346 		request_module("nfnetlink-subsys-%d", subsys_id);
347 		nfnl_lock(subsys_id);
348 		ss = nfnl_dereference_protected(subsys_id);
349 		if (!ss)
350 #endif
351 		{
352 			nfnl_unlock(subsys_id);
353 			netlink_ack(oskb, nlh, -EOPNOTSUPP, NULL);
354 			return kfree_skb(skb);
355 		}
356 	}
357 
358 	if (!ss->valid_genid || !ss->commit || !ss->abort) {
359 		nfnl_unlock(subsys_id);
360 		netlink_ack(oskb, nlh, -EOPNOTSUPP, NULL);
361 		return kfree_skb(skb);
362 	}
363 
364 	if (!try_module_get(ss->owner)) {
365 		nfnl_unlock(subsys_id);
366 		netlink_ack(oskb, nlh, -EOPNOTSUPP, NULL);
367 		return kfree_skb(skb);
368 	}
369 
370 	if (!ss->valid_genid(net, genid)) {
371 		module_put(ss->owner);
372 		nfnl_unlock(subsys_id);
373 		netlink_ack(oskb, nlh, -ERESTART, NULL);
374 		return kfree_skb(skb);
375 	}
376 
377 	nfnl_unlock(subsys_id);
378 
379 	while (skb->len >= nlmsg_total_size(0)) {
380 		int msglen, type;
381 
382 		if (fatal_signal_pending(current)) {
383 			nfnl_err_reset(&err_list);
384 			err = -EINTR;
385 			status = NFNL_BATCH_FAILURE;
386 			goto done;
387 		}
388 
389 		memset(&extack, 0, sizeof(extack));
390 		nlh = nlmsg_hdr(skb);
391 		err = 0;
392 
393 		if (nlh->nlmsg_len < NLMSG_HDRLEN ||
394 		    skb->len < nlh->nlmsg_len ||
395 		    nlmsg_len(nlh) < sizeof(struct nfgenmsg)) {
396 			nfnl_err_reset(&err_list);
397 			status |= NFNL_BATCH_FAILURE;
398 			goto done;
399 		}
400 
401 		/* Only requests are handled by the kernel */
402 		if (!(nlh->nlmsg_flags & NLM_F_REQUEST)) {
403 			err = -EINVAL;
404 			goto ack;
405 		}
406 
407 		type = nlh->nlmsg_type;
408 		if (type == NFNL_MSG_BATCH_BEGIN) {
409 			/* Malformed: Batch begin twice */
410 			nfnl_err_reset(&err_list);
411 			status |= NFNL_BATCH_FAILURE;
412 			goto done;
413 		} else if (type == NFNL_MSG_BATCH_END) {
414 			status |= NFNL_BATCH_DONE;
415 			goto done;
416 		} else if (type < NLMSG_MIN_TYPE) {
417 			err = -EINVAL;
418 			goto ack;
419 		}
420 
421 		/* We only accept a batch with messages for the same
422 		 * subsystem.
423 		 */
424 		if (NFNL_SUBSYS_ID(type) != subsys_id) {
425 			err = -EINVAL;
426 			goto ack;
427 		}
428 
429 		nc = nfnetlink_find_client(type, ss);
430 		if (!nc) {
431 			err = -EINVAL;
432 			goto ack;
433 		}
434 
435 		{
436 			int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
437 			u8 cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
438 			struct nlattr *cda[NFNL_MAX_ATTR_COUNT + 1];
439 			struct nlattr *attr = (void *)nlh + min_len;
440 			int attrlen = nlh->nlmsg_len - min_len;
441 
442 			/* Sanity-check NFTA_MAX_ATTR */
443 			if (ss->cb[cb_id].attr_count > NFNL_MAX_ATTR_COUNT) {
444 				err = -ENOMEM;
445 				goto ack;
446 			}
447 
448 			err = nla_parse_deprecated(cda,
449 						   ss->cb[cb_id].attr_count,
450 						   attr, attrlen,
451 						   ss->cb[cb_id].policy, NULL);
452 			if (err < 0)
453 				goto ack;
454 
455 			if (nc->call_batch) {
456 				err = nc->call_batch(net, net->nfnl, skb, nlh,
457 						     (const struct nlattr **)cda,
458 						     &extack);
459 			}
460 
461 			/* The lock was released to autoload some module, we
462 			 * have to abort and start from scratch using the
463 			 * original skb.
464 			 */
465 			if (err == -EAGAIN) {
466 				status |= NFNL_BATCH_REPLAY;
467 				goto done;
468 			}
469 		}
470 ack:
471 		if (nlh->nlmsg_flags & NLM_F_ACK || err) {
472 			/* Errors are delivered once the full batch has been
473 			 * processed, this avoids that the same error is
474 			 * reported several times when replaying the batch.
475 			 */
476 			if (nfnl_err_add(&err_list, nlh, err, &extack) < 0) {
477 				/* We failed to enqueue an error, reset the
478 				 * list of errors and send OOM to userspace
479 				 * pointing to the batch header.
480 				 */
481 				nfnl_err_reset(&err_list);
482 				netlink_ack(oskb, nlmsg_hdr(oskb), -ENOMEM,
483 					    NULL);
484 				status |= NFNL_BATCH_FAILURE;
485 				goto done;
486 			}
487 			/* We don't stop processing the batch on errors, thus,
488 			 * userspace gets all the errors that the batch
489 			 * triggers.
490 			 */
491 			if (err)
492 				status |= NFNL_BATCH_FAILURE;
493 		}
494 
495 		msglen = NLMSG_ALIGN(nlh->nlmsg_len);
496 		if (msglen > skb->len)
497 			msglen = skb->len;
498 		skb_pull(skb, msglen);
499 	}
500 done:
501 	if (status & NFNL_BATCH_REPLAY) {
502 		ss->abort(net, oskb, true);
503 		nfnl_err_reset(&err_list);
504 		kfree_skb(skb);
505 		module_put(ss->owner);
506 		goto replay;
507 	} else if (status == NFNL_BATCH_DONE) {
508 		err = ss->commit(net, oskb);
509 		if (err == -EAGAIN) {
510 			status |= NFNL_BATCH_REPLAY;
511 			goto done;
512 		} else if (err) {
513 			ss->abort(net, oskb, false);
514 			netlink_ack(oskb, nlmsg_hdr(oskb), err, NULL);
515 		}
516 	} else {
517 		ss->abort(net, oskb, false);
518 	}
519 	if (ss->cleanup)
520 		ss->cleanup(net);
521 
522 	nfnl_err_deliver(&err_list, oskb);
523 	kfree_skb(skb);
524 	module_put(ss->owner);
525 }
526 
527 static const struct nla_policy nfnl_batch_policy[NFNL_BATCH_MAX + 1] = {
528 	[NFNL_BATCH_GENID]	= { .type = NLA_U32 },
529 };
530 
531 static void nfnetlink_rcv_skb_batch(struct sk_buff *skb, struct nlmsghdr *nlh)
532 {
533 	int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
534 	struct nlattr *attr = (void *)nlh + min_len;
535 	struct nlattr *cda[NFNL_BATCH_MAX + 1];
536 	int attrlen = nlh->nlmsg_len - min_len;
537 	struct nfgenmsg *nfgenmsg;
538 	int msglen, err;
539 	u32 gen_id = 0;
540 	u16 res_id;
541 
542 	msglen = NLMSG_ALIGN(nlh->nlmsg_len);
543 	if (msglen > skb->len)
544 		msglen = skb->len;
545 
546 	if (skb->len < NLMSG_HDRLEN + sizeof(struct nfgenmsg))
547 		return;
548 
549 	err = nla_parse_deprecated(cda, NFNL_BATCH_MAX, attr, attrlen,
550 				   nfnl_batch_policy, NULL);
551 	if (err < 0) {
552 		netlink_ack(skb, nlh, err, NULL);
553 		return;
554 	}
555 	if (cda[NFNL_BATCH_GENID])
556 		gen_id = ntohl(nla_get_be32(cda[NFNL_BATCH_GENID]));
557 
558 	nfgenmsg = nlmsg_data(nlh);
559 	skb_pull(skb, msglen);
560 	/* Work around old nft using host byte order */
561 	if (nfgenmsg->res_id == NFNL_SUBSYS_NFTABLES)
562 		res_id = NFNL_SUBSYS_NFTABLES;
563 	else
564 		res_id = ntohs(nfgenmsg->res_id);
565 
566 	nfnetlink_rcv_batch(skb, nlh, res_id, gen_id);
567 }
568 
569 static void nfnetlink_rcv(struct sk_buff *skb)
570 {
571 	struct nlmsghdr *nlh = nlmsg_hdr(skb);
572 
573 	if (skb->len < NLMSG_HDRLEN ||
574 	    nlh->nlmsg_len < NLMSG_HDRLEN ||
575 	    skb->len < nlh->nlmsg_len)
576 		return;
577 
578 	if (!netlink_net_capable(skb, CAP_NET_ADMIN)) {
579 		netlink_ack(skb, nlh, -EPERM, NULL);
580 		return;
581 	}
582 
583 	if (nlh->nlmsg_type == NFNL_MSG_BATCH_BEGIN)
584 		nfnetlink_rcv_skb_batch(skb, nlh);
585 	else
586 		netlink_rcv_skb(skb, nfnetlink_rcv_msg);
587 }
588 
589 #ifdef CONFIG_MODULES
590 static int nfnetlink_bind(struct net *net, int group)
591 {
592 	const struct nfnetlink_subsystem *ss;
593 	int type;
594 
595 	if (group <= NFNLGRP_NONE || group > NFNLGRP_MAX)
596 		return 0;
597 
598 	type = nfnl_group2type[group];
599 
600 	rcu_read_lock();
601 	ss = nfnetlink_get_subsys(type << 8);
602 	rcu_read_unlock();
603 	if (!ss)
604 		request_module_nowait("nfnetlink-subsys-%d", type);
605 	return 0;
606 }
607 #endif
608 
609 static int __net_init nfnetlink_net_init(struct net *net)
610 {
611 	struct sock *nfnl;
612 	struct netlink_kernel_cfg cfg = {
613 		.groups	= NFNLGRP_MAX,
614 		.input	= nfnetlink_rcv,
615 #ifdef CONFIG_MODULES
616 		.bind	= nfnetlink_bind,
617 #endif
618 	};
619 
620 	nfnl = netlink_kernel_create(net, NETLINK_NETFILTER, &cfg);
621 	if (!nfnl)
622 		return -ENOMEM;
623 	net->nfnl_stash = nfnl;
624 	rcu_assign_pointer(net->nfnl, nfnl);
625 	return 0;
626 }
627 
628 static void __net_exit nfnetlink_net_exit_batch(struct list_head *net_exit_list)
629 {
630 	struct net *net;
631 
632 	list_for_each_entry(net, net_exit_list, exit_list)
633 		RCU_INIT_POINTER(net->nfnl, NULL);
634 	synchronize_net();
635 	list_for_each_entry(net, net_exit_list, exit_list)
636 		netlink_kernel_release(net->nfnl_stash);
637 }
638 
639 static struct pernet_operations nfnetlink_net_ops = {
640 	.init		= nfnetlink_net_init,
641 	.exit_batch	= nfnetlink_net_exit_batch,
642 };
643 
644 static int __init nfnetlink_init(void)
645 {
646 	int i;
647 
648 	for (i = NFNLGRP_NONE + 1; i <= NFNLGRP_MAX; i++)
649 		BUG_ON(nfnl_group2type[i] == NFNL_SUBSYS_NONE);
650 
651 	for (i=0; i<NFNL_SUBSYS_COUNT; i++)
652 		__mutex_init(&table[i].mutex, nfnl_lockdep_names[i], &nfnl_lockdep_keys[i]);
653 
654 	return register_pernet_subsys(&nfnetlink_net_ops);
655 }
656 
657 static void __exit nfnetlink_exit(void)
658 {
659 	unregister_pernet_subsys(&nfnetlink_net_ops);
660 }
661 module_init(nfnetlink_init);
662 module_exit(nfnetlink_exit);
663