// SPDX-License-Identifier: GPL-2.0-only

  /*
   * Copyright (c) 2008-2009 Patrick McHardy <kaber@trash.net>
   * Copyright (c) 2012 Pablo Neira Ayuso <pablo@netfilter.org>
   * Copyright (c) 2012 Intel Corporation

   */
  
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/skbuff.h>
  #include <linux/ip.h>
  #include <linux/string.h>
  #include <linux/netlink.h>
  #include <linux/netfilter.h>
  #include <linux/netfilter_ipv4.h>
  #include <linux/netfilter/nfnetlink.h>
  #include <linux/netfilter/nf_tables.h>
  #include <net/netfilter/nf_conntrack.h>
  #include <net/netfilter/nf_nat.h>

  #include <net/netfilter/nf_tables.h>

  #include <net/ip.h>
  
  struct nft_nat {

  	u8			sreg_addr_min;
  	u8			sreg_addr_max;
  	u8			sreg_proto_min;
  	u8			sreg_proto_max;

  	enum nf_nat_manip_type  type:8;
  	u8			family;

  	u16			flags;

  };

  static void nft_nat_setup_addr(struct nf_nat_range2 *range,
  			       const struct nft_regs *regs,
  			       const struct nft_nat *priv)
  {
  	switch (priv->family) {
  	case AF_INET:
  		range->min_addr.ip = (__force __be32)
  				regs->data[priv->sreg_addr_min];
  		range->max_addr.ip = (__force __be32)
  				regs->data[priv->sreg_addr_max];
  		break;
  	case AF_INET6:
  		memcpy(range->min_addr.ip6, &regs->data[priv->sreg_addr_min],
  		       sizeof(range->min_addr.ip6));
  		memcpy(range->max_addr.ip6, &regs->data[priv->sreg_addr_max],
  		       sizeof(range->max_addr.ip6));
  		break;
  	}
  }
  
  static void nft_nat_setup_proto(struct nf_nat_range2 *range,
  				const struct nft_regs *regs,
  				const struct nft_nat *priv)
  {
  	range->min_proto.all = (__force __be16)
  		nft_reg_load16(&regs->data[priv->sreg_proto_min]);
  	range->max_proto.all = (__force __be16)
  		nft_reg_load16(&regs->data[priv->sreg_proto_max]);
  }

  static void nft_nat_setup_netmap(struct nf_nat_range2 *range,
  				 const struct nft_pktinfo *pkt,
  				 const struct nft_nat *priv)
  {
  	struct sk_buff *skb = pkt->skb;
  	union nf_inet_addr new_addr;
  	__be32 netmask;
  	int i, len = 0;
  
  	switch (priv->type) {
  	case NFT_NAT_SNAT:
  		if (nft_pf(pkt) == NFPROTO_IPV4) {
  			new_addr.ip = ip_hdr(skb)->saddr;
  			len = sizeof(struct in_addr);
  		} else {
  			new_addr.in6 = ipv6_hdr(skb)->saddr;
  			len = sizeof(struct in6_addr);
  		}
  		break;
  	case NFT_NAT_DNAT:
  		if (nft_pf(pkt) == NFPROTO_IPV4) {
  			new_addr.ip = ip_hdr(skb)->daddr;
  			len = sizeof(struct in_addr);
  		} else {
  			new_addr.in6 = ipv6_hdr(skb)->daddr;
  			len = sizeof(struct in6_addr);
  		}
  		break;
  	}
  
  	for (i = 0; i < len / sizeof(__be32); i++) {
  		netmask = ~(range->min_addr.ip6[i] ^ range->max_addr.ip6[i]);
  		new_addr.ip6[i] &= ~netmask;
  		new_addr.ip6[i] |= range->min_addr.ip6[i] & netmask;
  	}
  
  	range->min_addr = new_addr;
  	range->max_addr = new_addr;
  }

  static void nft_nat_eval(const struct nft_expr *expr,

  			 struct nft_regs *regs,

  			 const struct nft_pktinfo *pkt)
  {
  	const struct nft_nat *priv = nft_expr_priv(expr);
  	enum ip_conntrack_info ctinfo;
  	struct nf_conn *ct = nf_ct_get(pkt->skb, &ctinfo);

  	struct nf_nat_range2 range;

  
  	memset(&range, 0, sizeof(range));

  
  	if (priv->sreg_addr_min) {

  		nft_nat_setup_addr(&range, regs, priv);

  		if (priv->flags & NF_NAT_RANGE_NETMAP)
  			nft_nat_setup_netmap(&range, pkt, priv);
  	}

  	if (priv->sreg_proto_min)
  		nft_nat_setup_proto(&range, regs, priv);

  	range.flags = priv->flags;

  	regs->verdict.code = nf_nat_setup_info(ct, &range, priv->type);

  }
  
  static const struct nla_policy nft_nat_policy[NFTA_NAT_MAX + 1] = {
  	[NFTA_NAT_TYPE]		 = { .type = NLA_U32 },
  	[NFTA_NAT_FAMILY]	 = { .type = NLA_U32 },
  	[NFTA_NAT_REG_ADDR_MIN]	 = { .type = NLA_U32 },
  	[NFTA_NAT_REG_ADDR_MAX]	 = { .type = NLA_U32 },
  	[NFTA_NAT_REG_PROTO_MIN] = { .type = NLA_U32 },
  	[NFTA_NAT_REG_PROTO_MAX] = { .type = NLA_U32 },

  	[NFTA_NAT_FLAGS]	 = { .type = NLA_U32 },

  };

  static int nft_nat_validate(const struct nft_ctx *ctx,
  			    const struct nft_expr *expr,
  			    const struct nft_data **data)

  {
  	struct nft_nat *priv = nft_expr_priv(expr);
  	int err;

  	err = nft_chain_validate_dependency(ctx->chain, NFT_CHAIN_T_NAT);
  	if (err < 0)
  		return err;

  	switch (priv->type) {
  	case NFT_NAT_SNAT:
  		err = nft_chain_validate_hooks(ctx->chain,
  					       (1 << NF_INET_POST_ROUTING) |
  					       (1 << NF_INET_LOCAL_IN));
  		break;
  	case NFT_NAT_DNAT:
  		err = nft_chain_validate_hooks(ctx->chain,
  					       (1 << NF_INET_PRE_ROUTING) |
  					       (1 << NF_INET_LOCAL_OUT));
  		break;
  	}
  
  	return err;
  }
  
  static int nft_nat_init(const struct nft_ctx *ctx, const struct nft_expr *expr,
  			const struct nlattr * const tb[])
  {
  	struct nft_nat *priv = nft_expr_priv(expr);

  	unsigned int alen, plen;

  	u32 family;
  	int err;

  	if (tb[NFTA_NAT_TYPE] == NULL ||
  	    (tb[NFTA_NAT_REG_ADDR_MIN] == NULL &&
  	     tb[NFTA_NAT_REG_PROTO_MIN] == NULL))

  		return -EINVAL;
  
  	switch (ntohl(nla_get_be32(tb[NFTA_NAT_TYPE]))) {
  	case NFT_NAT_SNAT:
  		priv->type = NF_NAT_MANIP_SRC;
  		break;
  	case NFT_NAT_DNAT:
  		priv->type = NF_NAT_MANIP_DST;
  		break;
  	default:

  		return -EOPNOTSUPP;

  	}
  
  	if (tb[NFTA_NAT_FAMILY] == NULL)
  		return -EINVAL;

  	family = ntohl(nla_get_be32(tb[NFTA_NAT_FAMILY]));

  	if (ctx->family != NFPROTO_INET && ctx->family != family)

  		return -EOPNOTSUPP;

  
  	switch (family) {
  	case NFPROTO_IPV4:

  		alen = sizeof_field(struct nf_nat_range, min_addr.ip);

  		break;
  	case NFPROTO_IPV6:

  		alen = sizeof_field(struct nf_nat_range, min_addr.ip6);

  		break;
  	default:

  		if (tb[NFTA_NAT_REG_ADDR_MIN])
  			return -EAFNOSUPPORT;
  		break;

  	}

  	priv->family = family;

  
  	if (tb[NFTA_NAT_REG_ADDR_MIN]) {

  		err = nft_parse_register_load(tb[NFTA_NAT_REG_ADDR_MIN],
  					      &priv->sreg_addr_min, alen);

  		if (err < 0)
  			return err;

  		if (tb[NFTA_NAT_REG_ADDR_MAX]) {

  			err = nft_parse_register_load(tb[NFTA_NAT_REG_ADDR_MAX],
  						      &priv->sreg_addr_max,
  						      alen);

  			if (err < 0)
  				return err;
  		} else {
  			priv->sreg_addr_max = priv->sreg_addr_min;
  		}

  
  		priv->flags |= NF_NAT_RANGE_MAP_IPS;

  	}

  	plen = sizeof_field(struct nf_nat_range, min_addr.all);

  	if (tb[NFTA_NAT_REG_PROTO_MIN]) {

  		err = nft_parse_register_load(tb[NFTA_NAT_REG_PROTO_MIN],
  					      &priv->sreg_proto_min, plen);

  		if (err < 0)
  			return err;

  		if (tb[NFTA_NAT_REG_PROTO_MAX]) {

  			err = nft_parse_register_load(tb[NFTA_NAT_REG_PROTO_MAX],
  						      &priv->sreg_proto_max,
  						      plen);

  			if (err < 0)
  				return err;
  		} else {
  			priv->sreg_proto_max = priv->sreg_proto_min;
  		}

  
  		priv->flags |= NF_NAT_RANGE_PROTO_SPECIFIED;

  	}

  	if (tb[NFTA_NAT_FLAGS]) {

  		priv->flags |= ntohl(nla_get_be32(tb[NFTA_NAT_FLAGS]));

  		if (priv->flags & ~NF_NAT_RANGE_MASK)

  			return -EOPNOTSUPP;

  	}

  	return nf_ct_netns_get(ctx->net, family);

  }
  
  static int nft_nat_dump(struct sk_buff *skb, const struct nft_expr *expr)
  {
  	const struct nft_nat *priv = nft_expr_priv(expr);
  
  	switch (priv->type) {
  	case NF_NAT_MANIP_SRC:
  		if (nla_put_be32(skb, NFTA_NAT_TYPE, htonl(NFT_NAT_SNAT)))
  			goto nla_put_failure;
  		break;
  	case NF_NAT_MANIP_DST:
  		if (nla_put_be32(skb, NFTA_NAT_TYPE, htonl(NFT_NAT_DNAT)))
  			goto nla_put_failure;
  		break;
  	}
  
  	if (nla_put_be32(skb, NFTA_NAT_FAMILY, htonl(priv->family)))
  		goto nla_put_failure;

  
  	if (priv->sreg_addr_min) {

  		if (nft_dump_register(skb, NFTA_NAT_REG_ADDR_MIN,
  				      priv->sreg_addr_min) ||
  		    nft_dump_register(skb, NFTA_NAT_REG_ADDR_MAX,
  				      priv->sreg_addr_max))

  			goto nla_put_failure;
  	}

  	if (priv->sreg_proto_min) {

  		if (nft_dump_register(skb, NFTA_NAT_REG_PROTO_MIN,
  				      priv->sreg_proto_min) ||
  		    nft_dump_register(skb, NFTA_NAT_REG_PROTO_MAX,
  				      priv->sreg_proto_max))

  			goto nla_put_failure;
  	}

  
  	if (priv->flags != 0) {
  		if (nla_put_be32(skb, NFTA_NAT_FLAGS, htonl(priv->flags)))
  			goto nla_put_failure;
  	}

  	return 0;
  
  nla_put_failure:
  	return -1;
  }

  static void
  nft_nat_destroy(const struct nft_ctx *ctx, const struct nft_expr *expr)
  {
  	const struct nft_nat *priv = nft_expr_priv(expr);
  
  	nf_ct_netns_put(ctx->net, priv->family);
  }

  static struct nft_expr_type nft_nat_type;
  static const struct nft_expr_ops nft_nat_ops = {
  	.type           = &nft_nat_type,
  	.size           = NFT_EXPR_SIZE(sizeof(struct nft_nat)),
  	.eval           = nft_nat_eval,
  	.init           = nft_nat_init,

  	.destroy        = nft_nat_destroy,

  	.dump           = nft_nat_dump,

  	.validate	= nft_nat_validate,

  };
  
  static struct nft_expr_type nft_nat_type __read_mostly = {
  	.name           = "nat",
  	.ops            = &nft_nat_ops,
  	.policy         = nft_nat_policy,
  	.maxattr        = NFTA_NAT_MAX,
  	.owner          = THIS_MODULE,
  };

  #ifdef CONFIG_NF_TABLES_INET
  static void nft_nat_inet_eval(const struct nft_expr *expr,
  			      struct nft_regs *regs,
  			      const struct nft_pktinfo *pkt)
  {
  	const struct nft_nat *priv = nft_expr_priv(expr);

  	if (priv->family == nft_pf(pkt) ||
  	    priv->family == NFPROTO_INET)

  		nft_nat_eval(expr, regs, pkt);
  }
  
  static const struct nft_expr_ops nft_nat_inet_ops = {
  	.type           = &nft_nat_type,
  	.size           = NFT_EXPR_SIZE(sizeof(struct nft_nat)),
  	.eval           = nft_nat_inet_eval,
  	.init           = nft_nat_init,
  	.destroy        = nft_nat_destroy,
  	.dump           = nft_nat_dump,
  	.validate	= nft_nat_validate,
  };
  
  static struct nft_expr_type nft_inet_nat_type __read_mostly = {
  	.name           = "nat",
  	.family		= NFPROTO_INET,
  	.ops            = &nft_nat_inet_ops,
  	.policy         = nft_nat_policy,
  	.maxattr        = NFTA_NAT_MAX,
  	.owner          = THIS_MODULE,
  };
  
  static int nft_nat_inet_module_init(void)
  {
  	return nft_register_expr(&nft_inet_nat_type);
  }
  
  static void nft_nat_inet_module_exit(void)
  {
  	nft_unregister_expr(&nft_inet_nat_type);
  }
  #else
  static int nft_nat_inet_module_init(void) { return 0; }
  static void nft_nat_inet_module_exit(void) { }
  #endif

  static int __init nft_nat_module_init(void)
  {

  	int ret = nft_nat_inet_module_init();
  
  	if (ret)
  		return ret;
  
  	ret = nft_register_expr(&nft_nat_type);
  	if (ret)
  		nft_nat_inet_module_exit();
  
  	return ret;

  }
  
  static void __exit nft_nat_module_exit(void)
  {

  	nft_nat_inet_module_exit();

  	nft_unregister_expr(&nft_nat_type);
  }
  
  module_init(nft_nat_module_init);
  module_exit(nft_nat_module_exit);
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Tomasz Bursztyka <tomasz.bursztyka@linux.intel.com>");
  MODULE_ALIAS_NFT_EXPR("nat");

  MODULE_DESCRIPTION("Network Address Translation support");