/*
   * 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.
   */
  
  #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_core.h>
  #include <net/netfilter/nf_tables.h>
  #include <net/netfilter/nft_fib.h>
  
  #include <net/ip_fib.h>
  #include <net/route.h>
  
  /* don't try to find route from mcast/bcast/zeronet */
  static __be32 get_saddr(__be32 addr)
  {
  	if (ipv4_is_multicast(addr) || ipv4_is_lbcast(addr) ||
  	    ipv4_is_zeronet(addr))
  		return 0;
  	return addr;
  }

  #define DSCP_BITS     0xfc
  
  void nft_fib4_eval_type(const struct nft_expr *expr, struct nft_regs *regs,
  			const struct nft_pktinfo *pkt)
  {
  	const struct nft_fib *priv = nft_expr_priv(expr);
  	u32 *dst = &regs->data[priv->dreg];
  	const struct net_device *dev = NULL;
  	const struct iphdr *iph;
  	__be32 addr;
  
  	if (priv->flags & NFTA_FIB_F_IIF)

  		dev = nft_in(pkt);

  	else if (priv->flags & NFTA_FIB_F_OIF)

  		dev = nft_out(pkt);

  
  	iph = ip_hdr(pkt->skb);
  	if (priv->flags & NFTA_FIB_F_DADDR)
  		addr = iph->daddr;
  	else
  		addr = iph->saddr;

  	*dst = inet_dev_addr_type(nft_net(pkt), dev, addr);

  }
  EXPORT_SYMBOL_GPL(nft_fib4_eval_type);
  
  static int get_ifindex(const struct net_device *dev)
  {
  	return dev ? dev->ifindex : 0;
  }
  
  void nft_fib4_eval(const struct nft_expr *expr, struct nft_regs *regs,
  		   const struct nft_pktinfo *pkt)
  {
  	const struct nft_fib *priv = nft_expr_priv(expr);
  	u32 *dest = &regs->data[priv->dreg];
  	const struct iphdr *iph;
  	struct fib_result res;
  	struct flowi4 fl4 = {
  		.flowi4_scope = RT_SCOPE_UNIVERSE,
  		.flowi4_iif = LOOPBACK_IFINDEX,
  	};
  	const struct net_device *oif;
  	struct net_device *found;
  #ifdef CONFIG_IP_ROUTE_MULTIPATH
  	int i;
  #endif
  
  	/*
  	 * Do not set flowi4_oif, it restricts results (for example, asking
  	 * for oif 3 will get RTN_UNICAST result even if the daddr exits
  	 * on another interface.
  	 *
  	 * Search results for the desired outinterface instead.
  	 */
  	if (priv->flags & NFTA_FIB_F_OIF)

  		oif = nft_out(pkt);

  	else if (priv->flags & NFTA_FIB_F_IIF)

  		oif = nft_in(pkt);

  	else
  		oif = NULL;

  	if (nft_hook(pkt) == NF_INET_PRE_ROUTING &&
  	    nft_fib_is_loopback(pkt->skb, nft_in(pkt))) {

  		nft_fib_store_result(dest, priv, pkt,

  				     nft_in(pkt)->ifindex);

  		return;
  	}
  
  	iph = ip_hdr(pkt->skb);

  	if (ipv4_is_zeronet(iph->saddr)) {
  		if (ipv4_is_lbcast(iph->daddr) ||
  		    ipv4_is_local_multicast(iph->daddr)) {

  			nft_fib_store_result(dest, priv, pkt,

  					     get_ifindex(pkt->skb->dev));
  			return;
  		}

  	}
  
  	if (priv->flags & NFTA_FIB_F_MARK)
  		fl4.flowi4_mark = pkt->skb->mark;
  
  	fl4.flowi4_tos = iph->tos & DSCP_BITS;
  
  	if (priv->flags & NFTA_FIB_F_DADDR) {
  		fl4.daddr = iph->daddr;
  		fl4.saddr = get_saddr(iph->saddr);
  	} else {
  		fl4.daddr = iph->saddr;
  		fl4.saddr = get_saddr(iph->daddr);
  	}

  	*dest = 0;

  	if (fib_lookup(nft_net(pkt), &fl4, &res, FIB_LOOKUP_IGNORE_LINKSTATE))

  		return;
  
  	switch (res.type) {
  	case RTN_UNICAST:
  		break;

  	case RTN_LOCAL: /* Should not see RTN_LOCAL here */

  		return;
  	default:
  		break;
  	}
  
         if (!oif) {
                 found = FIB_RES_DEV(res);
                 goto ok;
         }
  
  #ifdef CONFIG_IP_ROUTE_MULTIPATH
  	for (i = 0; i < res.fi->fib_nhs; i++) {
  		struct fib_nh *nh = &res.fi->fib_nh[i];
  
  		if (nh->nh_dev == oif) {
  			found = nh->nh_dev;
  			goto ok;
  		}
  	}
  	return;
  #else
  	found = FIB_RES_DEV(res);
  	if (found != oif)
  		return;
  #endif
  ok:
  	switch (priv->result) {
  	case NFT_FIB_RESULT_OIF:
  		*dest = found->ifindex;
  		break;
  	case NFT_FIB_RESULT_OIFNAME:
  		strncpy((char *)dest, found->name, IFNAMSIZ);
  		break;
  	default:
  		WARN_ON_ONCE(1);
  		break;
  	}
  }
  EXPORT_SYMBOL_GPL(nft_fib4_eval);
  
  static struct nft_expr_type nft_fib4_type;
  
  static const struct nft_expr_ops nft_fib4_type_ops = {
  	.type		= &nft_fib4_type,
  	.size		= NFT_EXPR_SIZE(sizeof(struct nft_fib)),
  	.eval		= nft_fib4_eval_type,
  	.init		= nft_fib_init,
  	.dump		= nft_fib_dump,
  	.validate	= nft_fib_validate,
  };
  
  static const struct nft_expr_ops nft_fib4_ops = {
  	.type		= &nft_fib4_type,
  	.size		= NFT_EXPR_SIZE(sizeof(struct nft_fib)),
  	.eval		= nft_fib4_eval,
  	.init		= nft_fib_init,
  	.dump		= nft_fib_dump,
  	.validate	= nft_fib_validate,
  };
  
  static const struct nft_expr_ops *
  nft_fib4_select_ops(const struct nft_ctx *ctx,
  		    const struct nlattr * const tb[])
  {
  	enum nft_fib_result result;
  
  	if (!tb[NFTA_FIB_RESULT])
  		return ERR_PTR(-EINVAL);

  	result = ntohl(nla_get_be32(tb[NFTA_FIB_RESULT]));

  
  	switch (result) {
  	case NFT_FIB_RESULT_OIF:
  		return &nft_fib4_ops;
  	case NFT_FIB_RESULT_OIFNAME:
  		return &nft_fib4_ops;
  	case NFT_FIB_RESULT_ADDRTYPE:
  		return &nft_fib4_type_ops;
  	default:
  		return ERR_PTR(-EOPNOTSUPP);
  	}
  }
  
  static struct nft_expr_type nft_fib4_type __read_mostly = {
  	.name		= "fib",

  	.select_ops	= nft_fib4_select_ops,

  	.policy		= nft_fib_policy,
  	.maxattr	= NFTA_FIB_MAX,
  	.family		= NFPROTO_IPV4,
  	.owner		= THIS_MODULE,
  };
  
  static int __init nft_fib4_module_init(void)
  {
  	return nft_register_expr(&nft_fib4_type);
  }
  
  static void __exit nft_fib4_module_exit(void)
  {
  	nft_unregister_expr(&nft_fib4_type);
  }
  
  module_init(nft_fib4_module_init);
  module_exit(nft_fib4_module_exit);
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Florian Westphal <fw@strlen.de>");
  MODULE_ALIAS_NFT_AF_EXPR(2, "fib");