net/netfilter/nft_ct.c - linux - Git at Google

 /*
  * Copyright (c) 2008-2009 Patrick McHardy <kaber@trash.net>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  *
  * Development of this code funded by Astaro AG (http://www.astaro.com/)
  */

 #include <linux/kernel.h>
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/netlink.h>
 #include <linux/netfilter.h>
 #include <linux/netfilter/nf_tables.h>
 #include <net/netfilter/nf_tables.h>
 #include <net/netfilter/nf_conntrack.h>
 #include <net/netfilter/nf_conntrack_tuple.h>
 #include <net/netfilter/nf_conntrack_helper.h>
 #include <net/netfilter/nf_conntrack_ecache.h>

 struct nft_ct {
 	enum nft_ct_keys	key:8;
 	enum ip_conntrack_dir	dir:8;
 	union{
 		enum nft_registers	dreg:8;
 		enum nft_registers	sreg:8;
 	};
 	uint8_t			family;
 };

 static void nft_ct_get_eval(const struct nft_expr *expr,
 			    struct nft_data data[NFT_REG_MAX + 1],
 			    const struct nft_pktinfo *pkt)
 {
 	const struct nft_ct *priv = nft_expr_priv(expr);
 	struct nft_data *dest = &data[priv->dreg];
 	enum ip_conntrack_info ctinfo;
 	const struct nf_conn *ct;
 	const struct nf_conn_help *help;
 	const struct nf_conntrack_tuple *tuple;
 	const struct nf_conntrack_helper *helper;
 	long diff;
 	unsigned int state;

 	ct = nf_ct_get(pkt->skb, &ctinfo);

 	switch (priv->key) {
 	case NFT_CT_STATE:
 		if (ct == NULL)
 			state = NF_CT_STATE_INVALID_BIT;
 		else if (nf_ct_is_untracked(ct))
 			state = NF_CT_STATE_UNTRACKED_BIT;
 		else
 			state = NF_CT_STATE_BIT(ctinfo);
 		dest->data[0] = state;
 		return;
 	}

 	if (ct == NULL)
 		goto err;

 	switch (priv->key) {
 	case NFT_CT_DIRECTION:
 		dest->data[0] = CTINFO2DIR(ctinfo);
 		return;
 	case NFT_CT_STATUS:
 		dest->data[0] = ct->status;
 		return;
 #ifdef CONFIG_NF_CONNTRACK_MARK
 	case NFT_CT_MARK:
 		dest->data[0] = ct->mark;
 		return;
 #endif
 #ifdef CONFIG_NF_CONNTRACK_SECMARK
 	case NFT_CT_SECMARK:
 		dest->data[0] = ct->secmark;
 		return;
 #endif
 	case NFT_CT_EXPIRATION:
 		diff = (long)jiffies - (long)ct->timeout.expires;
 		if (diff < 0)
 			diff = 0;
 		dest->data[0] = jiffies_to_msecs(diff);
 		return;
 	case NFT_CT_HELPER:
 		if (ct->master == NULL)
 			goto err;
 		help = nfct_help(ct->master);
 		if (help == NULL)
 			goto err;
 		helper = rcu_dereference(help->helper);
 		if (helper == NULL)
 			goto err;
 		if (strlen(helper->name) >= sizeof(dest->data))
 			goto err;
 		strncpy((char *)dest->data, helper->name, sizeof(dest->data));
 		return;
 	}

 	tuple = &ct->tuplehash[priv->dir].tuple;
 	switch (priv->key) {
 	case NFT_CT_L3PROTOCOL:
 		dest->data[0] = nf_ct_l3num(ct);
 		return;
 	case NFT_CT_SRC:
 		memcpy(dest->data, tuple->src.u3.all,
 		       nf_ct_l3num(ct) == NFPROTO_IPV4 ? 4 : 16);
 		return;
 	case NFT_CT_DST:
 		memcpy(dest->data, tuple->dst.u3.all,
 		       nf_ct_l3num(ct) == NFPROTO_IPV4 ? 4 : 16);
 		return;
 	case NFT_CT_PROTOCOL:
 		dest->data[0] = nf_ct_protonum(ct);
 		return;
 	case NFT_CT_PROTO_SRC:
 		dest->data[0] = (__force __u16)tuple->src.u.all;
 		return;
 	case NFT_CT_PROTO_DST:
 		dest->data[0] = (__force __u16)tuple->dst.u.all;
 		return;
 	}
 	return;
 err:
 	data[NFT_REG_VERDICT].verdict = NFT_BREAK;
 }

 static void nft_ct_set_eval(const struct nft_expr *expr,
 			    struct nft_data data[NFT_REG_MAX + 1],
 			    const struct nft_pktinfo *pkt)
 {
 	const struct nft_ct *priv = nft_expr_priv(expr);
 	struct sk_buff *skb = pkt->skb;
 #ifdef CONFIG_NF_CONNTRACK_MARK
 	u32 value = data[priv->sreg].data[0];
 #endif
 	enum ip_conntrack_info ctinfo;
 	struct nf_conn *ct;

 	ct = nf_ct_get(skb, &ctinfo);
 	if (ct == NULL)
 		return;

 	switch (priv->key) {
 #ifdef CONFIG_NF_CONNTRACK_MARK
 	case NFT_CT_MARK:
 		if (ct->mark != value) {
 			ct->mark = value;
 			nf_conntrack_event_cache(IPCT_MARK, ct);
 		}
 		break;
 #endif
 	}
 }

 static const struct nla_policy nft_ct_policy[NFTA_CT_MAX + 1] = {
 	[NFTA_CT_DREG]		= { .type = NLA_U32 },
 	[NFTA_CT_KEY]		= { .type = NLA_U32 },
 	[NFTA_CT_DIRECTION]	= { .type = NLA_U8 },
 	[NFTA_CT_SREG]		= { .type = NLA_U32 },
 };

 static int nft_ct_l3proto_try_module_get(uint8_t family)
 {
 	int err;

 	if (family == NFPROTO_INET) {
 		err = nf_ct_l3proto_try_module_get(NFPROTO_IPV4);
 		if (err < 0)
 			goto err1;
 		err = nf_ct_l3proto_try_module_get(NFPROTO_IPV6);
 		if (err < 0)
 			goto err2;
 	} else {
 		err = nf_ct_l3proto_try_module_get(family);
 		if (err < 0)
 			goto err1;
 	}
 	return 0;

 err2:
 	nf_ct_l3proto_module_put(NFPROTO_IPV4);
 err1:
 	return err;
 }

 static void nft_ct_l3proto_module_put(uint8_t family)
 {
 	if (family == NFPROTO_INET) {
 		nf_ct_l3proto_module_put(NFPROTO_IPV4);
 		nf_ct_l3proto_module_put(NFPROTO_IPV6);
 	} else
 		nf_ct_l3proto_module_put(family);
 }

 static int nft_ct_init_validate_get(const struct nft_expr *expr,
 				    const struct nlattr * const tb[])
 {
 	struct nft_ct *priv = nft_expr_priv(expr);

 	if (tb[NFTA_CT_DIRECTION] != NULL) {
 		priv->dir = nla_get_u8(tb[NFTA_CT_DIRECTION]);
 		switch (priv->dir) {
 		case IP_CT_DIR_ORIGINAL:
 		case IP_CT_DIR_REPLY:
 			break;
 		default:
 			return -EINVAL;
 		}
 	}

 	switch (priv->key) {
 	case NFT_CT_STATE:
 	case NFT_CT_DIRECTION:
 	case NFT_CT_STATUS:
 #ifdef CONFIG_NF_CONNTRACK_MARK
 	case NFT_CT_MARK:
 #endif
 #ifdef CONFIG_NF_CONNTRACK_SECMARK
 	case NFT_CT_SECMARK:
 #endif
 	case NFT_CT_EXPIRATION:
 	case NFT_CT_HELPER:
 		if (tb[NFTA_CT_DIRECTION] != NULL)
 			return -EINVAL;
 		break;
 	case NFT_CT_PROTOCOL:
 	case NFT_CT_SRC:
 	case NFT_CT_DST:
 	case NFT_CT_PROTO_SRC:
 	case NFT_CT_PROTO_DST:
 		if (tb[NFTA_CT_DIRECTION] == NULL)
 			return -EINVAL;
 		break;
 	default:
 		return -EOPNOTSUPP;
 	}

 	return 0;
 }

 static int nft_ct_init_validate_set(uint32_t key)
 {
 	switch (key) {
 	case NFT_CT_MARK:
 		break;
 	default:
 		return -EOPNOTSUPP;
 	}

 	return 0;
 }

 static int nft_ct_init(const struct nft_ctx *ctx,
 		       const struct nft_expr *expr,
 		       const struct nlattr * const tb[])
 {
 	struct nft_ct *priv = nft_expr_priv(expr);
 	int err;

 	priv->key = ntohl(nla_get_be32(tb[NFTA_CT_KEY]));

 	if (tb[NFTA_CT_DREG]) {
 		err = nft_ct_init_validate_get(expr, tb);
 		if (err < 0)
 			return err;

 		priv->dreg = ntohl(nla_get_be32(tb[NFTA_CT_DREG]));
 		err = nft_validate_output_register(priv->dreg);
 		if (err < 0)
 			return err;

 		err = nft_validate_data_load(ctx, priv->dreg, NULL,
 					     NFT_DATA_VALUE);
 		if (err < 0)
 			return err;
 	} else {
 		err = nft_ct_init_validate_set(priv->key);
 		if (err < 0)
 			return err;

 		priv->sreg = ntohl(nla_get_be32(tb[NFTA_CT_SREG]));
 		err = nft_validate_input_register(priv->sreg);
 		if (err < 0)
 			return err;
 	}

 	err = nft_ct_l3proto_try_module_get(ctx->afi->family);
 	if (err < 0)
 		return err;

 	priv->family = ctx->afi->family;

 	return 0;
 }

 static void nft_ct_destroy(const struct nft_expr *expr)
 {
 	struct nft_ct *priv = nft_expr_priv(expr);

 	nft_ct_l3proto_module_put(priv->family);
 }

 static int nft_ct_get_dump(struct sk_buff *skb, const struct nft_expr *expr)
 {
 	const struct nft_ct *priv = nft_expr_priv(expr);

 	if (nla_put_be32(skb, NFTA_CT_DREG, htonl(priv->dreg)))
 		goto nla_put_failure;
 	if (nla_put_be32(skb, NFTA_CT_KEY, htonl(priv->key)))
 		goto nla_put_failure;
 	if (nla_put_u8(skb, NFTA_CT_DIRECTION, priv->dir))
 		goto nla_put_failure;
 	return 0;

 nla_put_failure:
 	return -1;
 }

 static int nft_ct_set_dump(struct sk_buff *skb, const struct nft_expr *expr)
 {
 	const struct nft_ct *priv = nft_expr_priv(expr);

 	if (nla_put_be32(skb, NFTA_CT_SREG, htonl(priv->sreg)))
 		goto nla_put_failure;
 	if (nla_put_be32(skb, NFTA_CT_KEY, htonl(priv->key)))
 		goto nla_put_failure;
 	return 0;

 nla_put_failure:
 	return -1;
 }

 static struct nft_expr_type nft_ct_type;
 static const struct nft_expr_ops nft_ct_get_ops = {
 	.type		= &nft_ct_type,
 	.size		= NFT_EXPR_SIZE(sizeof(struct nft_ct)),
 	.eval		= nft_ct_get_eval,
 	.init		= nft_ct_init,
 	.destroy	= nft_ct_destroy,
 	.dump		= nft_ct_get_dump,
 };

 static const struct nft_expr_ops nft_ct_set_ops = {
 	.type		= &nft_ct_type,
 	.size		= NFT_EXPR_SIZE(sizeof(struct nft_ct)),
 	.eval		= nft_ct_set_eval,
 	.init		= nft_ct_init,
 	.destroy	= nft_ct_destroy,
 	.dump		= nft_ct_set_dump,
 };

 static const struct nft_expr_ops *
 nft_ct_select_ops(const struct nft_ctx *ctx,
 		    const struct nlattr * const tb[])
 {
 	if (tb[NFTA_CT_KEY] == NULL)
 		return ERR_PTR(-EINVAL);

 	if (tb[NFTA_CT_DREG] && tb[NFTA_CT_SREG])
 		return ERR_PTR(-EINVAL);

 	if (tb[NFTA_CT_DREG])
 		return &nft_ct_get_ops;

 	if (tb[NFTA_CT_SREG])
 		return &nft_ct_set_ops;

 	return ERR_PTR(-EINVAL);
 }

 static struct nft_expr_type nft_ct_type __read_mostly = {
 	.name		= "ct",
 	.select_ops	= &nft_ct_select_ops,
 	.policy		= nft_ct_policy,
 	.maxattr	= NFTA_CT_MAX,
 	.owner		= THIS_MODULE,
 };

 static int __init nft_ct_module_init(void)
 {
 	return nft_register_expr(&nft_ct_type);
 }

 static void __exit nft_ct_module_exit(void)
 {
 	nft_unregister_expr(&nft_ct_type);
 }

 module_init(nft_ct_module_init);
 module_exit(nft_ct_module_exit);

 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
 MODULE_ALIAS_NFT_EXPR("ct");
	/*
	* Copyright (c) 2008-2009 Patrick McHardy <kaber@trash.net>
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 as
	* published by the Free Software Foundation.
	*
	* Development of this code funded by Astaro AG (http://www.astaro.com/)
	*/

	#include <linux/kernel.h>
	#include <linux/init.h>
	#include <linux/module.h>
	#include <linux/netlink.h>
	#include <linux/netfilter.h>
	#include <linux/netfilter/nf_tables.h>
	#include <net/netfilter/nf_tables.h>
	#include <net/netfilter/nf_conntrack.h>
	#include <net/netfilter/nf_conntrack_tuple.h>
	#include <net/netfilter/nf_conntrack_helper.h>
	#include <net/netfilter/nf_conntrack_ecache.h>

	struct nft_ct {
	enum nft_ct_keys key:8;
	enum ip_conntrack_dir dir:8;
	union{
	enum nft_registers dreg:8;
	enum nft_registers sreg:8;
	};
	uint8_t family;
	};

	static void nft_ct_get_eval(const struct nft_expr *expr,
	struct nft_data data[NFT_REG_MAX + 1],
	const struct nft_pktinfo *pkt)
	{
	const struct nft_ct *priv = nft_expr_priv(expr);
	struct nft_data *dest = &data[priv->dreg];
	enum ip_conntrack_info ctinfo;
	const struct nf_conn *ct;
	const struct nf_conn_help *help;
	const struct nf_conntrack_tuple *tuple;
	const struct nf_conntrack_helper *helper;
	long diff;
	unsigned int state;

	ct = nf_ct_get(pkt->skb, &ctinfo);

	switch (priv->key) {
	case NFT_CT_STATE:
	if (ct == NULL)
	state = NF_CT_STATE_INVALID_BIT;
	else if (nf_ct_is_untracked(ct))
	state = NF_CT_STATE_UNTRACKED_BIT;
	else
	state = NF_CT_STATE_BIT(ctinfo);
	dest->data[0] = state;
	return;
	}

	if (ct == NULL)
	goto err;

	switch (priv->key) {
	case NFT_CT_DIRECTION:
	dest->data[0] = CTINFO2DIR(ctinfo);
	return;
	case NFT_CT_STATUS:
	dest->data[0] = ct->status;
	return;
	#ifdef CONFIG_NF_CONNTRACK_MARK
	case NFT_CT_MARK:
	dest->data[0] = ct->mark;
	return;
	#endif
	#ifdef CONFIG_NF_CONNTRACK_SECMARK
	case NFT_CT_SECMARK:
	dest->data[0] = ct->secmark;
	return;
	#endif
	case NFT_CT_EXPIRATION:
	diff = (long)jiffies - (long)ct->timeout.expires;
	if (diff < 0)
	diff = 0;
	dest->data[0] = jiffies_to_msecs(diff);
	return;
	case NFT_CT_HELPER:
	if (ct->master == NULL)
	goto err;
	help = nfct_help(ct->master);
	if (help == NULL)
	goto err;
	helper = rcu_dereference(help->helper);
	if (helper == NULL)
	goto err;
	if (strlen(helper->name) >= sizeof(dest->data))
	goto err;
	strncpy((char *)dest->data, helper->name, sizeof(dest->data));
	return;
	}

	tuple = &ct->tuplehash[priv->dir].tuple;
	switch (priv->key) {
	case NFT_CT_L3PROTOCOL:
	dest->data[0] = nf_ct_l3num(ct);
	return;
	case NFT_CT_SRC:
	memcpy(dest->data, tuple->src.u3.all,
	nf_ct_l3num(ct) == NFPROTO_IPV4 ? 4 : 16);
	return;
	case NFT_CT_DST:
	memcpy(dest->data, tuple->dst.u3.all,
	nf_ct_l3num(ct) == NFPROTO_IPV4 ? 4 : 16);
	return;
	case NFT_CT_PROTOCOL:
	dest->data[0] = nf_ct_protonum(ct);
	return;
	case NFT_CT_PROTO_SRC:
	dest->data[0] = (__force __u16)tuple->src.u.all;
	return;
	case NFT_CT_PROTO_DST:
	dest->data[0] = (__force __u16)tuple->dst.u.all;
	return;
	}
	return;
	err:
	data[NFT_REG_VERDICT].verdict = NFT_BREAK;
	}

	static void nft_ct_set_eval(const struct nft_expr *expr,
	struct nft_data data[NFT_REG_MAX + 1],
	const struct nft_pktinfo *pkt)
	{
	const struct nft_ct *priv = nft_expr_priv(expr);
	struct sk_buff *skb = pkt->skb;
	#ifdef CONFIG_NF_CONNTRACK_MARK
	u32 value = data[priv->sreg].data[0];
	#endif
	enum ip_conntrack_info ctinfo;
	struct nf_conn *ct;

	ct = nf_ct_get(skb, &ctinfo);
	if (ct == NULL)
	return;

	switch (priv->key) {
	#ifdef CONFIG_NF_CONNTRACK_MARK
	case NFT_CT_MARK:
	if (ct->mark != value) {
	ct->mark = value;
	nf_conntrack_event_cache(IPCT_MARK, ct);
	}
	break;
	#endif
	}
	}

	static const struct nla_policy nft_ct_policy[NFTA_CT_MAX + 1] = {
	[NFTA_CT_DREG] = { .type = NLA_U32 },
	[NFTA_CT_KEY] = { .type = NLA_U32 },
	[NFTA_CT_DIRECTION] = { .type = NLA_U8 },
	[NFTA_CT_SREG] = { .type = NLA_U32 },
	};

	static int nft_ct_l3proto_try_module_get(uint8_t family)
	{
	int err;

	if (family == NFPROTO_INET) {
	err = nf_ct_l3proto_try_module_get(NFPROTO_IPV4);
	if (err < 0)
	goto err1;
	err = nf_ct_l3proto_try_module_get(NFPROTO_IPV6);
	if (err < 0)
	goto err2;
	} else {
	err = nf_ct_l3proto_try_module_get(family);
	if (err < 0)
	goto err1;
	}
	return 0;

	err2:
	nf_ct_l3proto_module_put(NFPROTO_IPV4);
	err1:
	return err;
	}

	static void nft_ct_l3proto_module_put(uint8_t family)
	{
	if (family == NFPROTO_INET) {
	nf_ct_l3proto_module_put(NFPROTO_IPV4);
	nf_ct_l3proto_module_put(NFPROTO_IPV6);
	} else
	nf_ct_l3proto_module_put(family);
	}

	static int nft_ct_init_validate_get(const struct nft_expr *expr,
	const struct nlattr * const tb[])
	{
	struct nft_ct *priv = nft_expr_priv(expr);

	if (tb[NFTA_CT_DIRECTION] != NULL) {
	priv->dir = nla_get_u8(tb[NFTA_CT_DIRECTION]);
	switch (priv->dir) {
	case IP_CT_DIR_ORIGINAL:
	case IP_CT_DIR_REPLY:
	break;
	default:
	return -EINVAL;
	}
	}

	switch (priv->key) {
	case NFT_CT_STATE:
	case NFT_CT_DIRECTION:
	case NFT_CT_STATUS:
	#ifdef CONFIG_NF_CONNTRACK_MARK
	case NFT_CT_MARK:
	#endif
	#ifdef CONFIG_NF_CONNTRACK_SECMARK
	case NFT_CT_SECMARK:
	#endif
	case NFT_CT_EXPIRATION:
	case NFT_CT_HELPER:
	if (tb[NFTA_CT_DIRECTION] != NULL)
	return -EINVAL;
	break;
	case NFT_CT_PROTOCOL:
	case NFT_CT_SRC:
	case NFT_CT_DST:
	case NFT_CT_PROTO_SRC:
	case NFT_CT_PROTO_DST:
	if (tb[NFTA_CT_DIRECTION] == NULL)
	return -EINVAL;
	break;
	default:
	return -EOPNOTSUPP;
	}

	return 0;
	}

	static int nft_ct_init_validate_set(uint32_t key)
	{
	switch (key) {
	case NFT_CT_MARK:
	break;
	default:
	return -EOPNOTSUPP;
	}

	return 0;
	}

	static int nft_ct_init(const struct nft_ctx *ctx,
	const struct nft_expr *expr,
	const struct nlattr * const tb[])
	{
	struct nft_ct *priv = nft_expr_priv(expr);
	int err;

	priv->key = ntohl(nla_get_be32(tb[NFTA_CT_KEY]));

	if (tb[NFTA_CT_DREG]) {
	err = nft_ct_init_validate_get(expr, tb);
	if (err < 0)
	return err;

	priv->dreg = ntohl(nla_get_be32(tb[NFTA_CT_DREG]));
	err = nft_validate_output_register(priv->dreg);
	if (err < 0)
	return err;

	err = nft_validate_data_load(ctx, priv->dreg, NULL,
	NFT_DATA_VALUE);
	if (err < 0)
	return err;
	} else {
	err = nft_ct_init_validate_set(priv->key);
	if (err < 0)
	return err;

	priv->sreg = ntohl(nla_get_be32(tb[NFTA_CT_SREG]));
	err = nft_validate_input_register(priv->sreg);
	if (err < 0)
	return err;
	}

	err = nft_ct_l3proto_try_module_get(ctx->afi->family);
	if (err < 0)
	return err;

	priv->family = ctx->afi->family;

	return 0;
	}

	static void nft_ct_destroy(const struct nft_expr *expr)
	{
	struct nft_ct *priv = nft_expr_priv(expr);

	nft_ct_l3proto_module_put(priv->family);
	}

	static int nft_ct_get_dump(struct sk_buff skb, const struct nft_expr expr)
	{
	const struct nft_ct *priv = nft_expr_priv(expr);

	if (nla_put_be32(skb, NFTA_CT_DREG, htonl(priv->dreg)))
	goto nla_put_failure;
	if (nla_put_be32(skb, NFTA_CT_KEY, htonl(priv->key)))
	goto nla_put_failure;
	if (nla_put_u8(skb, NFTA_CT_DIRECTION, priv->dir))
	goto nla_put_failure;
	return 0;

	nla_put_failure:
	return -1;
	}

	static int nft_ct_set_dump(struct sk_buff skb, const struct nft_expr expr)
	{
	const struct nft_ct *priv = nft_expr_priv(expr);

	if (nla_put_be32(skb, NFTA_CT_SREG, htonl(priv->sreg)))
	goto nla_put_failure;
	if (nla_put_be32(skb, NFTA_CT_KEY, htonl(priv->key)))
	goto nla_put_failure;
	return 0;

	nla_put_failure:
	return -1;
	}

	static struct nft_expr_type nft_ct_type;
	static const struct nft_expr_ops nft_ct_get_ops = {
	.type = &nft_ct_type,
	.size = NFT_EXPR_SIZE(sizeof(struct nft_ct)),
	.eval = nft_ct_get_eval,
	.init = nft_ct_init,
	.destroy = nft_ct_destroy,
	.dump = nft_ct_get_dump,
	};

	static const struct nft_expr_ops nft_ct_set_ops = {
	.type = &nft_ct_type,
	.size = NFT_EXPR_SIZE(sizeof(struct nft_ct)),
	.eval = nft_ct_set_eval,
	.init = nft_ct_init,
	.destroy = nft_ct_destroy,
	.dump = nft_ct_set_dump,
	};

	static const struct nft_expr_ops *
	nft_ct_select_ops(const struct nft_ctx *ctx,
	const struct nlattr * const tb[])
	{
	if (tb[NFTA_CT_KEY] == NULL)
	return ERR_PTR(-EINVAL);

	if (tb[NFTA_CT_DREG] && tb[NFTA_CT_SREG])
	return ERR_PTR(-EINVAL);

	if (tb[NFTA_CT_DREG])
	return &nft_ct_get_ops;

	if (tb[NFTA_CT_SREG])
	return &nft_ct_set_ops;

	return ERR_PTR(-EINVAL);
	}

	static struct nft_expr_type nft_ct_type __read_mostly = {
	.name = "ct",
	.select_ops = &nft_ct_select_ops,
	.policy = nft_ct_policy,
	.maxattr = NFTA_CT_MAX,
	.owner = THIS_MODULE,
	};

	static int __init nft_ct_module_init(void)
	{
	return nft_register_expr(&nft_ct_type);
	}

	static void __exit nft_ct_module_exit(void)
	{
	nft_unregister_expr(&nft_ct_type);
	}

	module_init(nft_ct_module_init);
	module_exit(nft_ct_module_exit);

	MODULE_LICENSE("GPL");
	MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
	MODULE_ALIAS_NFT_EXPR("ct");