/*
   * (C) 2012-2013 by Pablo Neira Ayuso <pablo@netfilter.org>
   *
   * 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.
   *
   * This software has been sponsored by Sophos Astaro <http://www.sophos.com>
   */
  
  #include <linux/kernel.h>
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/netlink.h>
  #include <linux/netfilter.h>
  #include <linux/netfilter/nfnetlink.h>
  #include <linux/netfilter/nf_tables.h>
  #include <linux/netfilter/nf_tables_compat.h>
  #include <linux/netfilter/x_tables.h>
  #include <linux/netfilter_ipv4/ip_tables.h>
  #include <linux/netfilter_ipv6/ip6_tables.h>

  #include <linux/netfilter_bridge/ebtables.h>

  #include <linux/netfilter_arp/arp_tables.h>

  #include <net/netfilter/nf_tables.h>

  struct nft_xt {
  	struct list_head	head;
  	struct nft_expr_ops	ops;
  	unsigned int		refcnt;

  
  	/* Unlike other expressions, ops doesn't have static storage duration.
  	 * nft core assumes they do.  We use kfree_rcu so that nft core can
  	 * can check expr->ops->size even after nft_compat->destroy() frees
  	 * the nft_xt struct that holds the ops structure.
  	 */
  	struct rcu_head		rcu_head;

  };

  /* Used for matches where *info is larger than X byte */
  #define NFT_MATCH_LARGE_THRESH	192
  
  struct nft_xt_match_priv {
  	void *info;
  };

  static bool nft_xt_put(struct nft_xt *xt)

  {
  	if (--xt->refcnt == 0) {
  		list_del(&xt->head);

  		kfree_rcu(xt, rcu_head);
  		return true;

  	}

  
  	return false;

  }

  static int nft_compat_chain_validate_dependency(const char *tablename,
  						const struct nft_chain *chain)
  {

  	const struct nft_base_chain *basechain;

  	if (!tablename ||
  	    !nft_is_base_chain(chain))

  		return 0;

  	basechain = nft_base_chain(chain);

  	if (strcmp(tablename, "nat") == 0 &&
  	    basechain->type->type != NFT_CHAIN_T_NAT)

  		return -EINVAL;
  
  	return 0;
  }

  union nft_entry {
  	struct ipt_entry e4;
  	struct ip6t_entry e6;

  	struct ebt_entry ebt;

  	struct arpt_entry arp;

  };
  
  static inline void
  nft_compat_set_par(struct xt_action_param *par, void *xt, const void *xt_info)
  {
  	par->target	= xt;
  	par->targinfo	= xt_info;
  	par->hotdrop	= false;
  }

  static void nft_target_eval_xt(const struct nft_expr *expr,

  			       struct nft_regs *regs,

  			       const struct nft_pktinfo *pkt)

  {
  	void *info = nft_expr_priv(expr);
  	struct xt_target *target = expr->ops->data;
  	struct sk_buff *skb = pkt->skb;
  	int ret;
  
  	nft_compat_set_par((struct xt_action_param *)&pkt->xt, target, info);
  
  	ret = target->target(skb, &pkt->xt);
  
  	if (pkt->xt.hotdrop)
  		ret = NF_DROP;

  	switch (ret) {

  	case XT_CONTINUE:

  		regs->verdict.code = NFT_CONTINUE;

  		break;
  	default:

  		regs->verdict.code = ret;

  		break;
  	}

  }
  
  static void nft_target_eval_bridge(const struct nft_expr *expr,

  				   struct nft_regs *regs,

  				   const struct nft_pktinfo *pkt)
  {
  	void *info = nft_expr_priv(expr);
  	struct xt_target *target = expr->ops->data;
  	struct sk_buff *skb = pkt->skb;
  	int ret;
  
  	nft_compat_set_par((struct xt_action_param *)&pkt->xt, target, info);
  
  	ret = target->target(skb, &pkt->xt);
  
  	if (pkt->xt.hotdrop)
  		ret = NF_DROP;
  
  	switch (ret) {
  	case EBT_ACCEPT:

  		regs->verdict.code = NF_ACCEPT;

  		break;
  	case EBT_DROP:

  		regs->verdict.code = NF_DROP;

  		break;
  	case EBT_CONTINUE:

  		regs->verdict.code = NFT_CONTINUE;

  		break;
  	case EBT_RETURN:

  		regs->verdict.code = NFT_RETURN;

  		break;
  	default:

  		regs->verdict.code = ret;

  		break;
  	}

  }
  
  static const struct nla_policy nft_target_policy[NFTA_TARGET_MAX + 1] = {
  	[NFTA_TARGET_NAME]	= { .type = NLA_NUL_STRING },
  	[NFTA_TARGET_REV]	= { .type = NLA_U32 },
  	[NFTA_TARGET_INFO]	= { .type = NLA_BINARY },
  };
  
  static void
  nft_target_set_tgchk_param(struct xt_tgchk_param *par,
  			   const struct nft_ctx *ctx,
  			   struct xt_target *target, void *info,

  			   union nft_entry *entry, u16 proto, bool inv)

  {

  	par->net	= ctx->net;

  	par->table	= ctx->table->name;
  	switch (ctx->afi->family) {
  	case AF_INET:
  		entry->e4.ip.proto = proto;
  		entry->e4.ip.invflags = inv ? IPT_INV_PROTO : 0;
  		break;
  	case AF_INET6:

  		if (proto)
  			entry->e6.ipv6.flags |= IP6T_F_PROTO;

  		entry->e6.ipv6.proto = proto;
  		entry->e6.ipv6.invflags = inv ? IP6T_INV_PROTO : 0;
  		break;

  	case NFPROTO_BRIDGE:

  		entry->ebt.ethproto = (__force __be16)proto;

  		entry->ebt.invflags = inv ? EBT_IPROTO : 0;
  		break;

  	case NFPROTO_ARP:
  		break;

  	}
  	par->entryinfo	= entry;
  	par->target	= target;
  	par->targinfo	= info;

  	if (nft_is_base_chain(ctx->chain)) {

  		const struct nft_base_chain *basechain =
  						nft_base_chain(ctx->chain);

  		const struct nf_hook_ops *ops = &basechain->ops[0];

  
  		par->hook_mask = 1 << ops->hooknum;

  	} else {
  		par->hook_mask = 0;

  	}
  	par->family	= ctx->afi->family;

  	par->nft_compat = true;

  }
  
  static void target_compat_from_user(struct xt_target *t, void *in, void *out)
  {

  	int pad;

  	memcpy(out, in, t->targetsize);
  	pad = XT_ALIGN(t->targetsize) - t->targetsize;
  	if (pad > 0)
  		memset(out + t->targetsize, 0, pad);

  }
  
  static const struct nla_policy nft_rule_compat_policy[NFTA_RULE_COMPAT_MAX + 1] = {
  	[NFTA_RULE_COMPAT_PROTO]	= { .type = NLA_U32 },
  	[NFTA_RULE_COMPAT_FLAGS]	= { .type = NLA_U32 },
  };

  static int nft_parse_compat(const struct nlattr *attr, u16 *proto, bool *inv)

  {
  	struct nlattr *tb[NFTA_RULE_COMPAT_MAX+1];
  	u32 flags;
  	int err;
  
  	err = nla_parse_nested(tb, NFTA_RULE_COMPAT_MAX, attr,

  			       nft_rule_compat_policy, NULL);

  	if (err < 0)
  		return err;
  
  	if (!tb[NFTA_RULE_COMPAT_PROTO] || !tb[NFTA_RULE_COMPAT_FLAGS])
  		return -EINVAL;
  
  	flags = ntohl(nla_get_be32(tb[NFTA_RULE_COMPAT_FLAGS]));
  	if (flags & ~NFT_RULE_COMPAT_F_MASK)
  		return -EINVAL;
  	if (flags & NFT_RULE_COMPAT_F_INV)
  		*inv = true;

  	*proto = ntohl(nla_get_be32(tb[NFTA_RULE_COMPAT_PROTO]));
  	return 0;

  }
  
  static int
  nft_target_init(const struct nft_ctx *ctx, const struct nft_expr *expr,
  		const struct nlattr * const tb[])
  {
  	void *info = nft_expr_priv(expr);
  	struct xt_target *target = expr->ops->data;
  	struct xt_tgchk_param par;
  	size_t size = XT_ALIGN(nla_len(tb[NFTA_TARGET_INFO]));

  	struct nft_xt *nft_xt;

  	u16 proto = 0;

  	bool inv = false;
  	union nft_entry e = {};
  	int ret;
  
  	target_compat_from_user(target, nla_data(tb[NFTA_TARGET_INFO]), info);

  	if (ctx->nla[NFTA_RULE_COMPAT]) {
  		ret = nft_parse_compat(ctx->nla[NFTA_RULE_COMPAT], &proto, &inv);
  		if (ret < 0)

  			return ret;

  	}

  
  	nft_target_set_tgchk_param(&par, ctx, target, info, &e, proto, inv);
  
  	ret = xt_check_target(&par, size, proto, inv);
  	if (ret < 0)

  		return ret;

  
  	/* The standard target cannot be used */

  	if (!target->target)
  		return -EINVAL;

  	nft_xt = container_of(expr->ops, struct nft_xt, ops);
  	nft_xt->refcnt++;

  	return 0;

  }
  
  static void

  nft_target_destroy(const struct nft_ctx *ctx, const struct nft_expr *expr)

  {
  	struct xt_target *target = expr->ops->data;

  	void *info = nft_expr_priv(expr);
  	struct xt_tgdtor_param par;
  
  	par.net = ctx->net;
  	par.target = target;
  	par.targinfo = info;
  	par.family = ctx->afi->family;
  	if (par.target->destroy != NULL)
  		par.target->destroy(&par);

  	if (nft_xt_put(container_of(expr->ops, struct nft_xt, ops)))
  		module_put(target->me);

  }

  static int nft_target_dump(struct sk_buff *skb, const struct nft_expr *expr)
  {
  	const struct xt_target *target = expr->ops->data;
  	void *info = nft_expr_priv(expr);
  
  	if (nla_put_string(skb, NFTA_TARGET_NAME, target->name) ||
  	    nla_put_be32(skb, NFTA_TARGET_REV, htonl(target->revision)) ||

  	    nla_put(skb, NFTA_TARGET_INFO, XT_ALIGN(target->targetsize), info))

  		goto nla_put_failure;
  
  	return 0;
  
  nla_put_failure:
  	return -1;
  }
  
  static int nft_target_validate(const struct nft_ctx *ctx,
  			       const struct nft_expr *expr,
  			       const struct nft_data **data)
  {
  	struct xt_target *target = expr->ops->data;
  	unsigned int hook_mask = 0;

  	int ret;

  	if (nft_is_base_chain(ctx->chain)) {

  		const struct nft_base_chain *basechain =
  						nft_base_chain(ctx->chain);

  		const struct nf_hook_ops *ops = &basechain->ops[0];

  
  		hook_mask = 1 << ops->hooknum;

  		if (target->hooks && !(hook_mask & target->hooks))

  			return -EINVAL;

  		ret = nft_compat_chain_validate_dependency(target->table,
  							   ctx->chain);
  		if (ret < 0)
  			return ret;

  	}
  	return 0;
  }

  static void __nft_match_eval(const struct nft_expr *expr,
  			     struct nft_regs *regs,
  			     const struct nft_pktinfo *pkt,
  			     void *info)

  {

  	struct xt_match *match = expr->ops->data;
  	struct sk_buff *skb = pkt->skb;
  	bool ret;
  
  	nft_compat_set_par((struct xt_action_param *)&pkt->xt, match, info);
  
  	ret = match->match(skb, (struct xt_action_param *)&pkt->xt);
  
  	if (pkt->xt.hotdrop) {

  		regs->verdict.code = NF_DROP;

  		return;
  	}

  	switch (ret ? 1 : 0) {
  	case 1:

  		regs->verdict.code = NFT_CONTINUE;

  		break;

  	case 0:

  		regs->verdict.code = NFT_BREAK;

  		break;
  	}
  }

  static void nft_match_large_eval(const struct nft_expr *expr,
  				 struct nft_regs *regs,
  				 const struct nft_pktinfo *pkt)
  {
  	struct nft_xt_match_priv *priv = nft_expr_priv(expr);
  
  	__nft_match_eval(expr, regs, pkt, priv->info);
  }

  static void nft_match_eval(const struct nft_expr *expr,
  			   struct nft_regs *regs,
  			   const struct nft_pktinfo *pkt)
  {
  	__nft_match_eval(expr, regs, pkt, nft_expr_priv(expr));
  }

  static const struct nla_policy nft_match_policy[NFTA_MATCH_MAX + 1] = {
  	[NFTA_MATCH_NAME]	= { .type = NLA_NUL_STRING },
  	[NFTA_MATCH_REV]	= { .type = NLA_U32 },
  	[NFTA_MATCH_INFO]	= { .type = NLA_BINARY },
  };
  
  /* struct xt_mtchk_param and xt_tgchk_param look very similar */
  static void
  nft_match_set_mtchk_param(struct xt_mtchk_param *par, const struct nft_ctx *ctx,
  			  struct xt_match *match, void *info,

  			  union nft_entry *entry, u16 proto, bool inv)

  {

  	par->net	= ctx->net;

  	par->table	= ctx->table->name;
  	switch (ctx->afi->family) {
  	case AF_INET:
  		entry->e4.ip.proto = proto;
  		entry->e4.ip.invflags = inv ? IPT_INV_PROTO : 0;
  		break;
  	case AF_INET6:

  		if (proto)
  			entry->e6.ipv6.flags |= IP6T_F_PROTO;

  		entry->e6.ipv6.proto = proto;
  		entry->e6.ipv6.invflags = inv ? IP6T_INV_PROTO : 0;
  		break;

  	case NFPROTO_BRIDGE:

  		entry->ebt.ethproto = (__force __be16)proto;

  		entry->ebt.invflags = inv ? EBT_IPROTO : 0;
  		break;

  	case NFPROTO_ARP:
  		break;

  	}
  	par->entryinfo	= entry;
  	par->match	= match;
  	par->matchinfo	= info;

  	if (nft_is_base_chain(ctx->chain)) {

  		const struct nft_base_chain *basechain =
  						nft_base_chain(ctx->chain);

  		const struct nf_hook_ops *ops = &basechain->ops[0];

  
  		par->hook_mask = 1 << ops->hooknum;

  	} else {
  		par->hook_mask = 0;

  	}
  	par->family	= ctx->afi->family;

  	par->nft_compat = true;

  }
  
  static void match_compat_from_user(struct xt_match *m, void *in, void *out)
  {

  	int pad;
  
  	memcpy(out, in, m->matchsize);
  	pad = XT_ALIGN(m->matchsize) - m->matchsize;
  	if (pad > 0)
  		memset(out + m->matchsize, 0, pad);

  }
  
  static int

  __nft_match_init(const struct nft_ctx *ctx, const struct nft_expr *expr,
  		 const struct nlattr * const tb[],
  		 void *info)

  {

  	struct xt_match *match = expr->ops->data;
  	struct xt_mtchk_param par;
  	size_t size = XT_ALIGN(nla_len(tb[NFTA_MATCH_INFO]));

  	struct nft_xt *nft_xt;

  	u16 proto = 0;

  	bool inv = false;
  	union nft_entry e = {};
  	int ret;
  
  	match_compat_from_user(match, nla_data(tb[NFTA_MATCH_INFO]), info);

  	if (ctx->nla[NFTA_RULE_COMPAT]) {
  		ret = nft_parse_compat(ctx->nla[NFTA_RULE_COMPAT], &proto, &inv);
  		if (ret < 0)

  			return ret;

  	}

  
  	nft_match_set_mtchk_param(&par, ctx, match, info, &e, proto, inv);
  
  	ret = xt_check_match(&par, size, proto, inv);
  	if (ret < 0)

  		return ret;

  	nft_xt = container_of(expr->ops, struct nft_xt, ops);
  	nft_xt->refcnt++;

  	return 0;

  }

  static int
  nft_match_init(const struct nft_ctx *ctx, const struct nft_expr *expr,
  	       const struct nlattr * const tb[])
  {
  	return __nft_match_init(ctx, expr, tb, nft_expr_priv(expr));
  }

  static int
  nft_match_large_init(const struct nft_ctx *ctx, const struct nft_expr *expr,
  		     const struct nlattr * const tb[])
  {
  	struct nft_xt_match_priv *priv = nft_expr_priv(expr);
  	struct xt_match *m = expr->ops->data;
  	int ret;
  
  	priv->info = kmalloc(XT_ALIGN(m->matchsize), GFP_KERNEL);
  	if (!priv->info)
  		return -ENOMEM;
  
  	ret = __nft_match_init(ctx, expr, tb, priv->info);
  	if (ret)
  		kfree(priv->info);
  	return ret;
  }

  static void

  __nft_match_destroy(const struct nft_ctx *ctx, const struct nft_expr *expr,
  		    void *info)

  {
  	struct xt_match *match = expr->ops->data;

  	struct module *me = match->me;

  	struct xt_mtdtor_param par;
  
  	par.net = ctx->net;
  	par.match = match;
  	par.matchinfo = info;
  	par.family = ctx->afi->family;
  	if (par.match->destroy != NULL)
  		par.match->destroy(&par);

  	if (nft_xt_put(container_of(expr->ops, struct nft_xt, ops)))

  		module_put(me);

  }

  static void
  nft_match_destroy(const struct nft_ctx *ctx, const struct nft_expr *expr)
  {
  	__nft_match_destroy(ctx, expr, nft_expr_priv(expr));
  }

  static void
  nft_match_large_destroy(const struct nft_ctx *ctx, const struct nft_expr *expr)
  {
  	struct nft_xt_match_priv *priv = nft_expr_priv(expr);
  
  	__nft_match_destroy(ctx, expr, priv->info);
  	kfree(priv->info);
  }

  static int __nft_match_dump(struct sk_buff *skb, const struct nft_expr *expr,
  			    void *info)

  {

  	struct xt_match *match = expr->ops->data;
  
  	if (nla_put_string(skb, NFTA_MATCH_NAME, match->name) ||
  	    nla_put_be32(skb, NFTA_MATCH_REV, htonl(match->revision)) ||

  	    nla_put(skb, NFTA_MATCH_INFO, XT_ALIGN(match->matchsize), info))

  		goto nla_put_failure;
  
  	return 0;
  
  nla_put_failure:
  	return -1;
  }

  static int nft_match_dump(struct sk_buff *skb, const struct nft_expr *expr)
  {
  	return __nft_match_dump(skb, expr, nft_expr_priv(expr));
  }

  static int nft_match_large_dump(struct sk_buff *skb, const struct nft_expr *e)
  {
  	struct nft_xt_match_priv *priv = nft_expr_priv(e);
  
  	return __nft_match_dump(skb, e, priv->info);
  }

  static int nft_match_validate(const struct nft_ctx *ctx,
  			      const struct nft_expr *expr,
  			      const struct nft_data **data)
  {
  	struct xt_match *match = expr->ops->data;
  	unsigned int hook_mask = 0;

  	int ret;

  	if (nft_is_base_chain(ctx->chain)) {

  		const struct nft_base_chain *basechain =
  						nft_base_chain(ctx->chain);

  		const struct nf_hook_ops *ops = &basechain->ops[0];

  
  		hook_mask = 1 << ops->hooknum;

  		if (match->hooks && !(hook_mask & match->hooks))

  			return -EINVAL;

  		ret = nft_compat_chain_validate_dependency(match->table,

  							   ctx->chain);
  		if (ret < 0)
  			return ret;

  	}
  	return 0;
  }
  
  static int
  nfnl_compat_fill_info(struct sk_buff *skb, u32 portid, u32 seq, u32 type,
  		      int event, u16 family, const char *name,
  		      int rev, int target)
  {
  	struct nlmsghdr *nlh;
  	struct nfgenmsg *nfmsg;
  	unsigned int flags = portid ? NLM_F_MULTI : 0;

  	event = nfnl_msg_type(NFNL_SUBSYS_NFT_COMPAT, event);

  	nlh = nlmsg_put(skb, portid, seq, event, sizeof(*nfmsg), flags);
  	if (nlh == NULL)
  		goto nlmsg_failure;
  
  	nfmsg = nlmsg_data(nlh);
  	nfmsg->nfgen_family = family;
  	nfmsg->version = NFNETLINK_V0;
  	nfmsg->res_id = 0;
  
  	if (nla_put_string(skb, NFTA_COMPAT_NAME, name) ||
  	    nla_put_be32(skb, NFTA_COMPAT_REV, htonl(rev)) ||
  	    nla_put_be32(skb, NFTA_COMPAT_TYPE, htonl(target)))
  		goto nla_put_failure;
  
  	nlmsg_end(skb, nlh);
  	return skb->len;
  
  nlmsg_failure:
  nla_put_failure:
  	nlmsg_cancel(skb, nlh);
  	return -1;
  }

  static int nfnl_compat_get(struct net *net, struct sock *nfnl,
  			   struct sk_buff *skb, const struct nlmsghdr *nlh,

  			   const struct nlattr * const tb[],
  			   struct netlink_ext_ack *extack)

  {
  	int ret = 0, target;
  	struct nfgenmsg *nfmsg;
  	const char *fmt;
  	const char *name;
  	u32 rev;
  	struct sk_buff *skb2;
  
  	if (tb[NFTA_COMPAT_NAME] == NULL ||
  	    tb[NFTA_COMPAT_REV] == NULL ||
  	    tb[NFTA_COMPAT_TYPE] == NULL)
  		return -EINVAL;
  
  	name = nla_data(tb[NFTA_COMPAT_NAME]);
  	rev = ntohl(nla_get_be32(tb[NFTA_COMPAT_REV]));
  	target = ntohl(nla_get_be32(tb[NFTA_COMPAT_TYPE]));
  
  	nfmsg = nlmsg_data(nlh);
  
  	switch(nfmsg->nfgen_family) {
  	case AF_INET:
  		fmt = "ipt_%s";
  		break;
  	case AF_INET6:
  		fmt = "ip6t_%s";
  		break;

  	case NFPROTO_BRIDGE:
  		fmt = "ebt_%s";
  		break;

  	case NFPROTO_ARP:
  		fmt = "arpt_%s";
  		break;

  	default:
  		pr_err("nft_compat: unsupported protocol %d
  ",
  			nfmsg->nfgen_family);
  		return -EINVAL;
  	}
  
  	try_then_request_module(xt_find_revision(nfmsg->nfgen_family, name,
  						 rev, target, &ret),
  						 fmt, name);
  
  	if (ret < 0)
  		return ret;
  
  	skb2 = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
  	if (skb2 == NULL)
  		return -ENOMEM;
  
  	/* include the best revision for this extension in the message */
  	if (nfnl_compat_fill_info(skb2, NETLINK_CB(skb).portid,
  				  nlh->nlmsg_seq,
  				  NFNL_MSG_TYPE(nlh->nlmsg_type),
  				  NFNL_MSG_COMPAT_GET,
  				  nfmsg->nfgen_family,
  				  name, ret, target) <= 0) {
  		kfree_skb(skb2);
  		return -ENOSPC;
  	}
  
  	ret = netlink_unicast(nfnl, skb2, NETLINK_CB(skb).portid,
  				MSG_DONTWAIT);
  	if (ret > 0)
  		ret = 0;
  
  	return ret == -EAGAIN ? -ENOBUFS : ret;
  }
  
  static const struct nla_policy nfnl_compat_policy_get[NFTA_COMPAT_MAX+1] = {
  	[NFTA_COMPAT_NAME]	= { .type = NLA_NUL_STRING,
  				    .len = NFT_COMPAT_NAME_MAX-1 },
  	[NFTA_COMPAT_REV]	= { .type = NLA_U32 },
  	[NFTA_COMPAT_TYPE]	= { .type = NLA_U32 },
  };
  
  static const struct nfnl_callback nfnl_nft_compat_cb[NFNL_MSG_COMPAT_MAX] = {
  	[NFNL_MSG_COMPAT_GET]		= { .call = nfnl_compat_get,
  					    .attr_count = NFTA_COMPAT_MAX,
  					    .policy = nfnl_compat_policy_get },
  };
  
  static const struct nfnetlink_subsystem nfnl_compat_subsys = {
  	.name		= "nft-compat",
  	.subsys_id	= NFNL_SUBSYS_NFT_COMPAT,
  	.cb_count	= NFNL_MSG_COMPAT_MAX,
  	.cb		= nfnl_nft_compat_cb,
  };
  
  static LIST_HEAD(nft_match_list);

  static struct nft_expr_type nft_match_type;

  static bool nft_match_cmp(const struct xt_match *match,
  			  const char *name, u32 rev, u32 family)
  {
  	return strcmp(match->name, name) == 0 && match->revision == rev &&
  	       (match->family == NFPROTO_UNSPEC || match->family == family);
  }

  static const struct nft_expr_ops *
  nft_match_select_ops(const struct nft_ctx *ctx,
  		     const struct nlattr * const tb[])
  {
  	struct nft_xt *nft_match;
  	struct xt_match *match;

  	unsigned int matchsize;

  	char *mt_name;

  	u32 rev, family;

  	int err;

  
  	if (tb[NFTA_MATCH_NAME] == NULL ||
  	    tb[NFTA_MATCH_REV] == NULL ||
  	    tb[NFTA_MATCH_INFO] == NULL)
  		return ERR_PTR(-EINVAL);
  
  	mt_name = nla_data(tb[NFTA_MATCH_NAME]);
  	rev = ntohl(nla_get_be32(tb[NFTA_MATCH_REV]));
  	family = ctx->afi->family;
  
  	/* Re-use the existing match if it's already loaded. */
  	list_for_each_entry(nft_match, &nft_match_list, head) {
  		struct xt_match *match = nft_match->ops.data;

  		if (nft_match_cmp(match, mt_name, rev, family))

  			return &nft_match->ops;
  	}
  
  	match = xt_request_find_match(family, mt_name, rev);
  	if (IS_ERR(match))
  		return ERR_PTR(-ENOENT);

  	if (match->matchsize > nla_len(tb[NFTA_MATCH_INFO])) {
  		err = -EINVAL;
  		goto err;
  	}

  	/* This is the first time we use this match, allocate operations */
  	nft_match = kzalloc(sizeof(struct nft_xt), GFP_KERNEL);

  	if (nft_match == NULL) {
  		err = -ENOMEM;
  		goto err;
  	}

  	nft_match->refcnt = 0;

  	nft_match->ops.type = &nft_match_type;

  	nft_match->ops.eval = nft_match_eval;
  	nft_match->ops.init = nft_match_init;
  	nft_match->ops.destroy = nft_match_destroy;
  	nft_match->ops.dump = nft_match_dump;
  	nft_match->ops.validate = nft_match_validate;
  	nft_match->ops.data = match;

  	matchsize = NFT_EXPR_SIZE(XT_ALIGN(match->matchsize));
  	if (matchsize > NFT_MATCH_LARGE_THRESH) {
  		matchsize = NFT_EXPR_SIZE(sizeof(struct nft_xt_match_priv));
  
  		nft_match->ops.eval = nft_match_large_eval;
  		nft_match->ops.init = nft_match_large_init;
  		nft_match->ops.destroy = nft_match_large_destroy;
  		nft_match->ops.dump = nft_match_large_dump;
  	}
  
  	nft_match->ops.size = matchsize;

  	list_add(&nft_match->head, &nft_match_list);
  
  	return &nft_match->ops;

  err:
  	module_put(match->me);
  	return ERR_PTR(err);

  }

  static struct nft_expr_type nft_match_type __read_mostly = {
  	.name		= "match",
  	.select_ops	= nft_match_select_ops,
  	.policy		= nft_match_policy,
  	.maxattr	= NFTA_MATCH_MAX,
  	.owner		= THIS_MODULE,
  };
  
  static LIST_HEAD(nft_target_list);
  
  static struct nft_expr_type nft_target_type;

  static bool nft_target_cmp(const struct xt_target *tg,
  			   const char *name, u32 rev, u32 family)
  {
  	return strcmp(tg->name, name) == 0 && tg->revision == rev &&
  	       (tg->family == NFPROTO_UNSPEC || tg->family == family);
  }

  static const struct nft_expr_ops *
  nft_target_select_ops(const struct nft_ctx *ctx,
  		      const struct nlattr * const tb[])
  {
  	struct nft_xt *nft_target;
  	struct xt_target *target;
  	char *tg_name;

  	u32 rev, family;

  	int err;

  
  	if (tb[NFTA_TARGET_NAME] == NULL ||
  	    tb[NFTA_TARGET_REV] == NULL ||
  	    tb[NFTA_TARGET_INFO] == NULL)
  		return ERR_PTR(-EINVAL);
  
  	tg_name = nla_data(tb[NFTA_TARGET_NAME]);
  	rev = ntohl(nla_get_be32(tb[NFTA_TARGET_REV]));
  	family = ctx->afi->family;

  	if (strcmp(tg_name, XT_ERROR_TARGET) == 0 ||
  	    strcmp(tg_name, XT_STANDARD_TARGET) == 0 ||
  	    strcmp(tg_name, "standard") == 0)
  		return ERR_PTR(-EINVAL);

  	/* Re-use the existing target if it's already loaded. */

  	list_for_each_entry(nft_target, &nft_target_list, head) {

  		struct xt_target *target = nft_target->ops.data;

  		if (!target->target)
  			continue;

  		if (nft_target_cmp(target, tg_name, rev, family))

  			return &nft_target->ops;
  	}
  
  	target = xt_request_find_target(family, tg_name, rev);
  	if (IS_ERR(target))
  		return ERR_PTR(-ENOENT);

  	if (!target->target) {
  		err = -EINVAL;
  		goto err;
  	}

  	if (target->targetsize > nla_len(tb[NFTA_TARGET_INFO])) {
  		err = -EINVAL;
  		goto err;
  	}

  	/* This is the first time we use this target, allocate operations */
  	nft_target = kzalloc(sizeof(struct nft_xt), GFP_KERNEL);

  	if (nft_target == NULL) {
  		err = -ENOMEM;
  		goto err;
  	}

  	nft_target->refcnt = 0;

  	nft_target->ops.type = &nft_target_type;

  	nft_target->ops.size = NFT_EXPR_SIZE(XT_ALIGN(target->targetsize));

  	nft_target->ops.init = nft_target_init;
  	nft_target->ops.destroy = nft_target_destroy;
  	nft_target->ops.dump = nft_target_dump;
  	nft_target->ops.validate = nft_target_validate;
  	nft_target->ops.data = target;

  	if (family == NFPROTO_BRIDGE)
  		nft_target->ops.eval = nft_target_eval_bridge;
  	else
  		nft_target->ops.eval = nft_target_eval_xt;

  	list_add(&nft_target->head, &nft_target_list);
  
  	return &nft_target->ops;

  err:
  	module_put(target->me);
  	return ERR_PTR(err);

  }

  static struct nft_expr_type nft_target_type __read_mostly = {
  	.name		= "target",
  	.select_ops	= nft_target_select_ops,
  	.policy		= nft_target_policy,
  	.maxattr	= NFTA_TARGET_MAX,
  	.owner		= THIS_MODULE,
  };
  
  static int __init nft_compat_module_init(void)
  {
  	int ret;
  
  	ret = nft_register_expr(&nft_match_type);
  	if (ret < 0)
  		return ret;
  
  	ret = nft_register_expr(&nft_target_type);
  	if (ret < 0)
  		goto err_match;
  
  	ret = nfnetlink_subsys_register(&nfnl_compat_subsys);
  	if (ret < 0) {
  		pr_err("nft_compat: cannot register with nfnetlink.
  ");
  		goto err_target;
  	}
  
  	pr_info("nf_tables_compat: (c) 2012 Pablo Neira Ayuso <pablo@netfilter.org>
  ");
  
  	return ret;
  
  err_target:
  	nft_unregister_expr(&nft_target_type);
  err_match:
  	nft_unregister_expr(&nft_match_type);
  	return ret;
  }
  
  static void __exit nft_compat_module_exit(void)
  {

  	struct nft_xt *xt, *next;
  
  	/* list should be empty here, it can be non-empty only in case there
  	 * was an error that caused nft_xt expr to not be initialized fully
  	 * and noone else requested the same expression later.
  	 *
  	 * In this case, the lists contain 0-refcount entries that still
  	 * hold module reference.
  	 */
  	list_for_each_entry_safe(xt, next, &nft_target_list, head) {
  		struct xt_target *target = xt->ops.data;
  
  		if (WARN_ON_ONCE(xt->refcnt))
  			continue;
  		module_put(target->me);
  		kfree(xt);
  	}
  
  	list_for_each_entry_safe(xt, next, &nft_match_list, head) {
  		struct xt_match *match = xt->ops.data;
  
  		if (WARN_ON_ONCE(xt->refcnt))
  			continue;
  		module_put(match->me);
  		kfree(xt);
  	}

  	nfnetlink_subsys_unregister(&nfnl_compat_subsys);
  	nft_unregister_expr(&nft_target_type);
  	nft_unregister_expr(&nft_match_type);

  }
  
  MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_NFT_COMPAT);
  
  module_init(nft_compat_module_init);
  module_exit(nft_compat_module_exit);
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
  MODULE_ALIAS_NFT_EXPR("match");
  MODULE_ALIAS_NFT_EXPR("target");