xref: /openbmc/linux/net/netfilter/nft_compat.c (revision 4949009e)
1 /*
2  * (C) 2012-2013 by Pablo Neira Ayuso <pablo@netfilter.org>
3  *
4  * This program is free software; you can redistribute it and/or modify
5  * it under the terms of the GNU General Public License version 2 as
6  * published by the Free Software Foundation.
7  *
8  * This software has been sponsored by Sophos Astaro <http://www.sophos.com>
9  */
10 
11 #include <linux/kernel.h>
12 #include <linux/init.h>
13 #include <linux/module.h>
14 #include <linux/netlink.h>
15 #include <linux/netfilter.h>
16 #include <linux/netfilter/nfnetlink.h>
17 #include <linux/netfilter/nf_tables.h>
18 #include <linux/netfilter/nf_tables_compat.h>
19 #include <linux/netfilter/x_tables.h>
20 #include <linux/netfilter_ipv4/ip_tables.h>
21 #include <linux/netfilter_ipv6/ip6_tables.h>
22 #include <net/netfilter/nf_tables.h>
23 
24 static int nft_compat_chain_validate_dependency(const char *tablename,
25 						const struct nft_chain *chain)
26 {
27 	const struct nft_base_chain *basechain;
28 
29 	if (!tablename || !(chain->flags & NFT_BASE_CHAIN))
30 		return 0;
31 
32 	basechain = nft_base_chain(chain);
33 	if (strcmp(tablename, "nat") == 0 &&
34 	    basechain->type->type != NFT_CHAIN_T_NAT)
35 		return -EINVAL;
36 
37 	return 0;
38 }
39 
40 union nft_entry {
41 	struct ipt_entry e4;
42 	struct ip6t_entry e6;
43 };
44 
45 static inline void
46 nft_compat_set_par(struct xt_action_param *par, void *xt, const void *xt_info)
47 {
48 	par->target	= xt;
49 	par->targinfo	= xt_info;
50 	par->hotdrop	= false;
51 }
52 
53 static void nft_target_eval(const struct nft_expr *expr,
54 			    struct nft_data data[NFT_REG_MAX + 1],
55 			    const struct nft_pktinfo *pkt)
56 {
57 	void *info = nft_expr_priv(expr);
58 	struct xt_target *target = expr->ops->data;
59 	struct sk_buff *skb = pkt->skb;
60 	int ret;
61 
62 	nft_compat_set_par((struct xt_action_param *)&pkt->xt, target, info);
63 
64 	ret = target->target(skb, &pkt->xt);
65 
66 	if (pkt->xt.hotdrop)
67 		ret = NF_DROP;
68 
69 	switch(ret) {
70 	case XT_CONTINUE:
71 		data[NFT_REG_VERDICT].verdict = NFT_CONTINUE;
72 		break;
73 	default:
74 		data[NFT_REG_VERDICT].verdict = ret;
75 		break;
76 	}
77 	return;
78 }
79 
80 static const struct nla_policy nft_target_policy[NFTA_TARGET_MAX + 1] = {
81 	[NFTA_TARGET_NAME]	= { .type = NLA_NUL_STRING },
82 	[NFTA_TARGET_REV]	= { .type = NLA_U32 },
83 	[NFTA_TARGET_INFO]	= { .type = NLA_BINARY },
84 };
85 
86 static void
87 nft_target_set_tgchk_param(struct xt_tgchk_param *par,
88 			   const struct nft_ctx *ctx,
89 			   struct xt_target *target, void *info,
90 			   union nft_entry *entry, u8 proto, bool inv)
91 {
92 	par->net	= ctx->net;
93 	par->table	= ctx->table->name;
94 	switch (ctx->afi->family) {
95 	case AF_INET:
96 		entry->e4.ip.proto = proto;
97 		entry->e4.ip.invflags = inv ? IPT_INV_PROTO : 0;
98 		break;
99 	case AF_INET6:
100 		entry->e6.ipv6.proto = proto;
101 		entry->e6.ipv6.invflags = inv ? IP6T_INV_PROTO : 0;
102 		break;
103 	}
104 	par->entryinfo	= entry;
105 	par->target	= target;
106 	par->targinfo	= info;
107 	if (ctx->chain->flags & NFT_BASE_CHAIN) {
108 		const struct nft_base_chain *basechain =
109 						nft_base_chain(ctx->chain);
110 		const struct nf_hook_ops *ops = &basechain->ops[0];
111 
112 		par->hook_mask = 1 << ops->hooknum;
113 	} else {
114 		par->hook_mask = 0;
115 	}
116 	par->family	= ctx->afi->family;
117 }
118 
119 static void target_compat_from_user(struct xt_target *t, void *in, void *out)
120 {
121 	int pad;
122 
123 	memcpy(out, in, t->targetsize);
124 	pad = XT_ALIGN(t->targetsize) - t->targetsize;
125 	if (pad > 0)
126 		memset(out + t->targetsize, 0, pad);
127 }
128 
129 static const struct nla_policy nft_rule_compat_policy[NFTA_RULE_COMPAT_MAX + 1] = {
130 	[NFTA_RULE_COMPAT_PROTO]	= { .type = NLA_U32 },
131 	[NFTA_RULE_COMPAT_FLAGS]	= { .type = NLA_U32 },
132 };
133 
134 static int nft_parse_compat(const struct nlattr *attr, u8 *proto, bool *inv)
135 {
136 	struct nlattr *tb[NFTA_RULE_COMPAT_MAX+1];
137 	u32 flags;
138 	int err;
139 
140 	err = nla_parse_nested(tb, NFTA_RULE_COMPAT_MAX, attr,
141 			       nft_rule_compat_policy);
142 	if (err < 0)
143 		return err;
144 
145 	if (!tb[NFTA_RULE_COMPAT_PROTO] || !tb[NFTA_RULE_COMPAT_FLAGS])
146 		return -EINVAL;
147 
148 	flags = ntohl(nla_get_be32(tb[NFTA_RULE_COMPAT_FLAGS]));
149 	if (flags & ~NFT_RULE_COMPAT_F_MASK)
150 		return -EINVAL;
151 	if (flags & NFT_RULE_COMPAT_F_INV)
152 		*inv = true;
153 
154 	*proto = ntohl(nla_get_be32(tb[NFTA_RULE_COMPAT_PROTO]));
155 	return 0;
156 }
157 
158 static int
159 nft_target_init(const struct nft_ctx *ctx, const struct nft_expr *expr,
160 		const struct nlattr * const tb[])
161 {
162 	void *info = nft_expr_priv(expr);
163 	struct xt_target *target = expr->ops->data;
164 	struct xt_tgchk_param par;
165 	size_t size = XT_ALIGN(nla_len(tb[NFTA_TARGET_INFO]));
166 	u8 proto = 0;
167 	bool inv = false;
168 	union nft_entry e = {};
169 	int ret;
170 
171 	ret = nft_compat_chain_validate_dependency(target->table, ctx->chain);
172 	if (ret < 0)
173 		goto err;
174 
175 	target_compat_from_user(target, nla_data(tb[NFTA_TARGET_INFO]), info);
176 
177 	if (ctx->nla[NFTA_RULE_COMPAT]) {
178 		ret = nft_parse_compat(ctx->nla[NFTA_RULE_COMPAT], &proto, &inv);
179 		if (ret < 0)
180 			goto err;
181 	}
182 
183 	nft_target_set_tgchk_param(&par, ctx, target, info, &e, proto, inv);
184 
185 	ret = xt_check_target(&par, size, proto, inv);
186 	if (ret < 0)
187 		goto err;
188 
189 	/* The standard target cannot be used */
190 	if (target->target == NULL) {
191 		ret = -EINVAL;
192 		goto err;
193 	}
194 
195 	return 0;
196 err:
197 	module_put(target->me);
198 	return ret;
199 }
200 
201 static void
202 nft_target_destroy(const struct nft_ctx *ctx, const struct nft_expr *expr)
203 {
204 	struct xt_target *target = expr->ops->data;
205 	void *info = nft_expr_priv(expr);
206 	struct xt_tgdtor_param par;
207 
208 	par.net = ctx->net;
209 	par.target = target;
210 	par.targinfo = info;
211 	par.family = ctx->afi->family;
212 	if (par.target->destroy != NULL)
213 		par.target->destroy(&par);
214 
215 	module_put(target->me);
216 }
217 
218 static int nft_target_dump(struct sk_buff *skb, const struct nft_expr *expr)
219 {
220 	const struct xt_target *target = expr->ops->data;
221 	void *info = nft_expr_priv(expr);
222 
223 	if (nla_put_string(skb, NFTA_TARGET_NAME, target->name) ||
224 	    nla_put_be32(skb, NFTA_TARGET_REV, htonl(target->revision)) ||
225 	    nla_put(skb, NFTA_TARGET_INFO, XT_ALIGN(target->targetsize), info))
226 		goto nla_put_failure;
227 
228 	return 0;
229 
230 nla_put_failure:
231 	return -1;
232 }
233 
234 static int nft_target_validate(const struct nft_ctx *ctx,
235 			       const struct nft_expr *expr,
236 			       const struct nft_data **data)
237 {
238 	struct xt_target *target = expr->ops->data;
239 	unsigned int hook_mask = 0;
240 	int ret;
241 
242 	if (ctx->chain->flags & NFT_BASE_CHAIN) {
243 		const struct nft_base_chain *basechain =
244 						nft_base_chain(ctx->chain);
245 		const struct nf_hook_ops *ops = &basechain->ops[0];
246 
247 		hook_mask = 1 << ops->hooknum;
248 		if (!(hook_mask & target->hooks))
249 			return -EINVAL;
250 
251 		ret = nft_compat_chain_validate_dependency(target->table,
252 							   ctx->chain);
253 		if (ret < 0)
254 			return ret;
255 	}
256 	return 0;
257 }
258 
259 static void nft_match_eval(const struct nft_expr *expr,
260 			   struct nft_data data[NFT_REG_MAX + 1],
261 			   const struct nft_pktinfo *pkt)
262 {
263 	void *info = nft_expr_priv(expr);
264 	struct xt_match *match = expr->ops->data;
265 	struct sk_buff *skb = pkt->skb;
266 	bool ret;
267 
268 	nft_compat_set_par((struct xt_action_param *)&pkt->xt, match, info);
269 
270 	ret = match->match(skb, (struct xt_action_param *)&pkt->xt);
271 
272 	if (pkt->xt.hotdrop) {
273 		data[NFT_REG_VERDICT].verdict = NF_DROP;
274 		return;
275 	}
276 
277 	switch(ret) {
278 	case true:
279 		data[NFT_REG_VERDICT].verdict = NFT_CONTINUE;
280 		break;
281 	case false:
282 		data[NFT_REG_VERDICT].verdict = NFT_BREAK;
283 		break;
284 	}
285 }
286 
287 static const struct nla_policy nft_match_policy[NFTA_MATCH_MAX + 1] = {
288 	[NFTA_MATCH_NAME]	= { .type = NLA_NUL_STRING },
289 	[NFTA_MATCH_REV]	= { .type = NLA_U32 },
290 	[NFTA_MATCH_INFO]	= { .type = NLA_BINARY },
291 };
292 
293 /* struct xt_mtchk_param and xt_tgchk_param look very similar */
294 static void
295 nft_match_set_mtchk_param(struct xt_mtchk_param *par, const struct nft_ctx *ctx,
296 			  struct xt_match *match, void *info,
297 			  union nft_entry *entry, u8 proto, bool inv)
298 {
299 	par->net	= ctx->net;
300 	par->table	= ctx->table->name;
301 	switch (ctx->afi->family) {
302 	case AF_INET:
303 		entry->e4.ip.proto = proto;
304 		entry->e4.ip.invflags = inv ? IPT_INV_PROTO : 0;
305 		break;
306 	case AF_INET6:
307 		entry->e6.ipv6.proto = proto;
308 		entry->e6.ipv6.invflags = inv ? IP6T_INV_PROTO : 0;
309 		break;
310 	}
311 	par->entryinfo	= entry;
312 	par->match	= match;
313 	par->matchinfo	= info;
314 	if (ctx->chain->flags & NFT_BASE_CHAIN) {
315 		const struct nft_base_chain *basechain =
316 						nft_base_chain(ctx->chain);
317 		const struct nf_hook_ops *ops = &basechain->ops[0];
318 
319 		par->hook_mask = 1 << ops->hooknum;
320 	} else {
321 		par->hook_mask = 0;
322 	}
323 	par->family	= ctx->afi->family;
324 }
325 
326 static void match_compat_from_user(struct xt_match *m, void *in, void *out)
327 {
328 	int pad;
329 
330 	memcpy(out, in, m->matchsize);
331 	pad = XT_ALIGN(m->matchsize) - m->matchsize;
332 	if (pad > 0)
333 		memset(out + m->matchsize, 0, pad);
334 }
335 
336 static int
337 nft_match_init(const struct nft_ctx *ctx, const struct nft_expr *expr,
338 		const struct nlattr * const tb[])
339 {
340 	void *info = nft_expr_priv(expr);
341 	struct xt_match *match = expr->ops->data;
342 	struct xt_mtchk_param par;
343 	size_t size = XT_ALIGN(nla_len(tb[NFTA_MATCH_INFO]));
344 	u8 proto = 0;
345 	bool inv = false;
346 	union nft_entry e = {};
347 	int ret;
348 
349 	ret = nft_compat_chain_validate_dependency(match->table, ctx->chain);
350 	if (ret < 0)
351 		goto err;
352 
353 	match_compat_from_user(match, nla_data(tb[NFTA_MATCH_INFO]), info);
354 
355 	if (ctx->nla[NFTA_RULE_COMPAT]) {
356 		ret = nft_parse_compat(ctx->nla[NFTA_RULE_COMPAT], &proto, &inv);
357 		if (ret < 0)
358 			goto err;
359 	}
360 
361 	nft_match_set_mtchk_param(&par, ctx, match, info, &e, proto, inv);
362 
363 	ret = xt_check_match(&par, size, proto, inv);
364 	if (ret < 0)
365 		goto err;
366 
367 	return 0;
368 err:
369 	module_put(match->me);
370 	return ret;
371 }
372 
373 static void
374 nft_match_destroy(const struct nft_ctx *ctx, const struct nft_expr *expr)
375 {
376 	struct xt_match *match = expr->ops->data;
377 	void *info = nft_expr_priv(expr);
378 	struct xt_mtdtor_param par;
379 
380 	par.net = ctx->net;
381 	par.match = match;
382 	par.matchinfo = info;
383 	par.family = ctx->afi->family;
384 	if (par.match->destroy != NULL)
385 		par.match->destroy(&par);
386 
387 	module_put(match->me);
388 }
389 
390 static int nft_match_dump(struct sk_buff *skb, const struct nft_expr *expr)
391 {
392 	void *info = nft_expr_priv(expr);
393 	struct xt_match *match = expr->ops->data;
394 
395 	if (nla_put_string(skb, NFTA_MATCH_NAME, match->name) ||
396 	    nla_put_be32(skb, NFTA_MATCH_REV, htonl(match->revision)) ||
397 	    nla_put(skb, NFTA_MATCH_INFO, XT_ALIGN(match->matchsize), info))
398 		goto nla_put_failure;
399 
400 	return 0;
401 
402 nla_put_failure:
403 	return -1;
404 }
405 
406 static int nft_match_validate(const struct nft_ctx *ctx,
407 			      const struct nft_expr *expr,
408 			      const struct nft_data **data)
409 {
410 	struct xt_match *match = expr->ops->data;
411 	unsigned int hook_mask = 0;
412 	int ret;
413 
414 	if (ctx->chain->flags & NFT_BASE_CHAIN) {
415 		const struct nft_base_chain *basechain =
416 						nft_base_chain(ctx->chain);
417 		const struct nf_hook_ops *ops = &basechain->ops[0];
418 
419 		hook_mask = 1 << ops->hooknum;
420 		if (!(hook_mask & match->hooks))
421 			return -EINVAL;
422 
423 		ret = nft_compat_chain_validate_dependency(match->table,
424 							   ctx->chain);
425 		if (ret < 0)
426 			return ret;
427 	}
428 	return 0;
429 }
430 
431 static int
432 nfnl_compat_fill_info(struct sk_buff *skb, u32 portid, u32 seq, u32 type,
433 		      int event, u16 family, const char *name,
434 		      int rev, int target)
435 {
436 	struct nlmsghdr *nlh;
437 	struct nfgenmsg *nfmsg;
438 	unsigned int flags = portid ? NLM_F_MULTI : 0;
439 
440 	event |= NFNL_SUBSYS_NFT_COMPAT << 8;
441 	nlh = nlmsg_put(skb, portid, seq, event, sizeof(*nfmsg), flags);
442 	if (nlh == NULL)
443 		goto nlmsg_failure;
444 
445 	nfmsg = nlmsg_data(nlh);
446 	nfmsg->nfgen_family = family;
447 	nfmsg->version = NFNETLINK_V0;
448 	nfmsg->res_id = 0;
449 
450 	if (nla_put_string(skb, NFTA_COMPAT_NAME, name) ||
451 	    nla_put_be32(skb, NFTA_COMPAT_REV, htonl(rev)) ||
452 	    nla_put_be32(skb, NFTA_COMPAT_TYPE, htonl(target)))
453 		goto nla_put_failure;
454 
455 	nlmsg_end(skb, nlh);
456 	return skb->len;
457 
458 nlmsg_failure:
459 nla_put_failure:
460 	nlmsg_cancel(skb, nlh);
461 	return -1;
462 }
463 
464 static int
465 nfnl_compat_get(struct sock *nfnl, struct sk_buff *skb,
466 		const struct nlmsghdr *nlh, const struct nlattr * const tb[])
467 {
468 	int ret = 0, target;
469 	struct nfgenmsg *nfmsg;
470 	const char *fmt;
471 	const char *name;
472 	u32 rev;
473 	struct sk_buff *skb2;
474 
475 	if (tb[NFTA_COMPAT_NAME] == NULL ||
476 	    tb[NFTA_COMPAT_REV] == NULL ||
477 	    tb[NFTA_COMPAT_TYPE] == NULL)
478 		return -EINVAL;
479 
480 	name = nla_data(tb[NFTA_COMPAT_NAME]);
481 	rev = ntohl(nla_get_be32(tb[NFTA_COMPAT_REV]));
482 	target = ntohl(nla_get_be32(tb[NFTA_COMPAT_TYPE]));
483 
484 	nfmsg = nlmsg_data(nlh);
485 
486 	switch(nfmsg->nfgen_family) {
487 	case AF_INET:
488 		fmt = "ipt_%s";
489 		break;
490 	case AF_INET6:
491 		fmt = "ip6t_%s";
492 		break;
493 	default:
494 		pr_err("nft_compat: unsupported protocol %d\n",
495 			nfmsg->nfgen_family);
496 		return -EINVAL;
497 	}
498 
499 	try_then_request_module(xt_find_revision(nfmsg->nfgen_family, name,
500 						 rev, target, &ret),
501 						 fmt, name);
502 
503 	if (ret < 0)
504 		return ret;
505 
506 	skb2 = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
507 	if (skb2 == NULL)
508 		return -ENOMEM;
509 
510 	/* include the best revision for this extension in the message */
511 	if (nfnl_compat_fill_info(skb2, NETLINK_CB(skb).portid,
512 				  nlh->nlmsg_seq,
513 				  NFNL_MSG_TYPE(nlh->nlmsg_type),
514 				  NFNL_MSG_COMPAT_GET,
515 				  nfmsg->nfgen_family,
516 				  name, ret, target) <= 0) {
517 		kfree_skb(skb2);
518 		return -ENOSPC;
519 	}
520 
521 	ret = netlink_unicast(nfnl, skb2, NETLINK_CB(skb).portid,
522 				MSG_DONTWAIT);
523 	if (ret > 0)
524 		ret = 0;
525 
526 	return ret == -EAGAIN ? -ENOBUFS : ret;
527 }
528 
529 static const struct nla_policy nfnl_compat_policy_get[NFTA_COMPAT_MAX+1] = {
530 	[NFTA_COMPAT_NAME]	= { .type = NLA_NUL_STRING,
531 				    .len = NFT_COMPAT_NAME_MAX-1 },
532 	[NFTA_COMPAT_REV]	= { .type = NLA_U32 },
533 	[NFTA_COMPAT_TYPE]	= { .type = NLA_U32 },
534 };
535 
536 static const struct nfnl_callback nfnl_nft_compat_cb[NFNL_MSG_COMPAT_MAX] = {
537 	[NFNL_MSG_COMPAT_GET]		= { .call = nfnl_compat_get,
538 					    .attr_count = NFTA_COMPAT_MAX,
539 					    .policy = nfnl_compat_policy_get },
540 };
541 
542 static const struct nfnetlink_subsystem nfnl_compat_subsys = {
543 	.name		= "nft-compat",
544 	.subsys_id	= NFNL_SUBSYS_NFT_COMPAT,
545 	.cb_count	= NFNL_MSG_COMPAT_MAX,
546 	.cb		= nfnl_nft_compat_cb,
547 };
548 
549 static LIST_HEAD(nft_match_list);
550 
551 struct nft_xt {
552 	struct list_head	head;
553 	struct nft_expr_ops	ops;
554 };
555 
556 static struct nft_expr_type nft_match_type;
557 
558 static const struct nft_expr_ops *
559 nft_match_select_ops(const struct nft_ctx *ctx,
560 		     const struct nlattr * const tb[])
561 {
562 	struct nft_xt *nft_match;
563 	struct xt_match *match;
564 	char *mt_name;
565 	__u32 rev, family;
566 
567 	if (tb[NFTA_MATCH_NAME] == NULL ||
568 	    tb[NFTA_MATCH_REV] == NULL ||
569 	    tb[NFTA_MATCH_INFO] == NULL)
570 		return ERR_PTR(-EINVAL);
571 
572 	mt_name = nla_data(tb[NFTA_MATCH_NAME]);
573 	rev = ntohl(nla_get_be32(tb[NFTA_MATCH_REV]));
574 	family = ctx->afi->family;
575 
576 	/* Re-use the existing match if it's already loaded. */
577 	list_for_each_entry(nft_match, &nft_match_list, head) {
578 		struct xt_match *match = nft_match->ops.data;
579 
580 		if (strcmp(match->name, mt_name) == 0 &&
581 		    match->revision == rev && match->family == family)
582 			return &nft_match->ops;
583 	}
584 
585 	match = xt_request_find_match(family, mt_name, rev);
586 	if (IS_ERR(match))
587 		return ERR_PTR(-ENOENT);
588 
589 	/* This is the first time we use this match, allocate operations */
590 	nft_match = kzalloc(sizeof(struct nft_xt), GFP_KERNEL);
591 	if (nft_match == NULL)
592 		return ERR_PTR(-ENOMEM);
593 
594 	nft_match->ops.type = &nft_match_type;
595 	nft_match->ops.size = NFT_EXPR_SIZE(XT_ALIGN(match->matchsize));
596 	nft_match->ops.eval = nft_match_eval;
597 	nft_match->ops.init = nft_match_init;
598 	nft_match->ops.destroy = nft_match_destroy;
599 	nft_match->ops.dump = nft_match_dump;
600 	nft_match->ops.validate = nft_match_validate;
601 	nft_match->ops.data = match;
602 
603 	list_add(&nft_match->head, &nft_match_list);
604 
605 	return &nft_match->ops;
606 }
607 
608 static void nft_match_release(void)
609 {
610 	struct nft_xt *nft_match, *tmp;
611 
612 	list_for_each_entry_safe(nft_match, tmp, &nft_match_list, head)
613 		kfree(nft_match);
614 }
615 
616 static struct nft_expr_type nft_match_type __read_mostly = {
617 	.name		= "match",
618 	.select_ops	= nft_match_select_ops,
619 	.policy		= nft_match_policy,
620 	.maxattr	= NFTA_MATCH_MAX,
621 	.owner		= THIS_MODULE,
622 };
623 
624 static LIST_HEAD(nft_target_list);
625 
626 static struct nft_expr_type nft_target_type;
627 
628 static const struct nft_expr_ops *
629 nft_target_select_ops(const struct nft_ctx *ctx,
630 		      const struct nlattr * const tb[])
631 {
632 	struct nft_xt *nft_target;
633 	struct xt_target *target;
634 	char *tg_name;
635 	__u32 rev, family;
636 
637 	if (tb[NFTA_TARGET_NAME] == NULL ||
638 	    tb[NFTA_TARGET_REV] == NULL ||
639 	    tb[NFTA_TARGET_INFO] == NULL)
640 		return ERR_PTR(-EINVAL);
641 
642 	tg_name = nla_data(tb[NFTA_TARGET_NAME]);
643 	rev = ntohl(nla_get_be32(tb[NFTA_TARGET_REV]));
644 	family = ctx->afi->family;
645 
646 	/* Re-use the existing target if it's already loaded. */
647 	list_for_each_entry(nft_target, &nft_target_list, head) {
648 		struct xt_target *target = nft_target->ops.data;
649 
650 		if (strcmp(target->name, tg_name) == 0 &&
651 		    target->revision == rev && target->family == family)
652 			return &nft_target->ops;
653 	}
654 
655 	target = xt_request_find_target(family, tg_name, rev);
656 	if (IS_ERR(target))
657 		return ERR_PTR(-ENOENT);
658 
659 	/* This is the first time we use this target, allocate operations */
660 	nft_target = kzalloc(sizeof(struct nft_xt), GFP_KERNEL);
661 	if (nft_target == NULL)
662 		return ERR_PTR(-ENOMEM);
663 
664 	nft_target->ops.type = &nft_target_type;
665 	nft_target->ops.size = NFT_EXPR_SIZE(XT_ALIGN(target->targetsize));
666 	nft_target->ops.eval = nft_target_eval;
667 	nft_target->ops.init = nft_target_init;
668 	nft_target->ops.destroy = nft_target_destroy;
669 	nft_target->ops.dump = nft_target_dump;
670 	nft_target->ops.validate = nft_target_validate;
671 	nft_target->ops.data = target;
672 
673 	list_add(&nft_target->head, &nft_target_list);
674 
675 	return &nft_target->ops;
676 }
677 
678 static void nft_target_release(void)
679 {
680 	struct nft_xt *nft_target, *tmp;
681 
682 	list_for_each_entry_safe(nft_target, tmp, &nft_target_list, head)
683 		kfree(nft_target);
684 }
685 
686 static struct nft_expr_type nft_target_type __read_mostly = {
687 	.name		= "target",
688 	.select_ops	= nft_target_select_ops,
689 	.policy		= nft_target_policy,
690 	.maxattr	= NFTA_TARGET_MAX,
691 	.owner		= THIS_MODULE,
692 };
693 
694 static int __init nft_compat_module_init(void)
695 {
696 	int ret;
697 
698 	ret = nft_register_expr(&nft_match_type);
699 	if (ret < 0)
700 		return ret;
701 
702 	ret = nft_register_expr(&nft_target_type);
703 	if (ret < 0)
704 		goto err_match;
705 
706 	ret = nfnetlink_subsys_register(&nfnl_compat_subsys);
707 	if (ret < 0) {
708 		pr_err("nft_compat: cannot register with nfnetlink.\n");
709 		goto err_target;
710 	}
711 
712 	pr_info("nf_tables_compat: (c) 2012 Pablo Neira Ayuso <pablo@netfilter.org>\n");
713 
714 	return ret;
715 
716 err_target:
717 	nft_unregister_expr(&nft_target_type);
718 err_match:
719 	nft_unregister_expr(&nft_match_type);
720 	return ret;
721 }
722 
723 static void __exit nft_compat_module_exit(void)
724 {
725 	nfnetlink_subsys_unregister(&nfnl_compat_subsys);
726 	nft_unregister_expr(&nft_target_type);
727 	nft_unregister_expr(&nft_match_type);
728 	nft_match_release();
729 	nft_target_release();
730 }
731 
732 MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_NFT_COMPAT);
733 
734 module_init(nft_compat_module_init);
735 module_exit(nft_compat_module_exit);
736 
737 MODULE_LICENSE("GPL");
738 MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
739 MODULE_ALIAS_NFT_EXPR("match");
740 MODULE_ALIAS_NFT_EXPR("target");
741