text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   * (C) 1999-2001 Paul `Rusty' Russell
   * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
   * Copyright (c) 2011 Patrick McHardy <kaber@trash.net>
   *
   * Based on Rusty Russell's IPv4 REDIRECT target. Development of IPv6
   * NAT funded by Astaro.
   */
  
  #include <linux/if.h>
  #include <linux/inetdevice.h>
  #include <linux/ip.h>
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/netdevice.h>
  #include <linux/netfilter.h>
  #include <linux/types.h>
  #include <linux/netfilter_ipv4.h>
  #include <linux/netfilter_ipv6.h>
  #include <linux/netfilter/x_tables.h>
  #include <net/addrconf.h>
  #include <net/checksum.h>
  #include <net/protocol.h>
  #include <net/netfilter/nf_nat.h>
  #include <net/netfilter/nf_nat_redirect.h>
  
  static unsigned int
  redirect_tg6(struct sk_buff *skb, const struct xt_action_param *par)
  {
  	return nf_nat_redirect_ipv6(skb, par->targinfo, xt_hooknum(par));
  }
  
  static int redirect_tg6_checkentry(const struct xt_tgchk_param *par)
  {
  	const struct nf_nat_range2 *range = par->targinfo;
  
  	if (range->flags & NF_NAT_RANGE_MAP_IPS)
  		return -EINVAL;
  
  	return nf_ct_netns_get(par->net, par->family);
  }
  
  static void redirect_tg_destroy(const struct xt_tgdtor_param *par)
  {
  	nf_ct_netns_put(par->net, par->family);
  }
  
  /* FIXME: Take multiple ranges --RR */
  static int redirect_tg4_check(const struct xt_tgchk_param *par)
  {
  	const struct nf_nat_ipv4_multi_range_compat *mr = par->targinfo;
  
  	if (mr->range[0].flags & NF_NAT_RANGE_MAP_IPS) {
  		pr_debug("bad MAP_IPS.\n");
  		return -EINVAL;
  	}
  	if (mr->rangesize != 1) {
  		pr_debug("bad rangesize %u.\n", mr->rangesize);
  		return -EINVAL;
  	}
  	return nf_ct_netns_get(par->net, par->family);
  }
  
  static unsigned int
  redirect_tg4(struct sk_buff *skb, const struct xt_action_param *par)
  {
  	return nf_nat_redirect_ipv4(skb, par->targinfo, xt_hooknum(par));
  }
  
  static struct xt_target redirect_tg_reg[] __read_mostly = {
  	{
  		.name       = "REDIRECT",
  		.family     = NFPROTO_IPV6,
  		.revision   = 0,
  		.table      = "nat",
  		.checkentry = redirect_tg6_checkentry,
  		.destroy    = redirect_tg_destroy,
  		.target     = redirect_tg6,
  		.targetsize = sizeof(struct nf_nat_range),
  		.hooks      = (1 << NF_INET_PRE_ROUTING) |
  		              (1 << NF_INET_LOCAL_OUT),
  		.me         = THIS_MODULE,
  	},
  	{
  		.name       = "REDIRECT",
  		.family     = NFPROTO_IPV4,
  		.revision   = 0,
  		.table      = "nat",
  		.target     = redirect_tg4,
  		.checkentry = redirect_tg4_check,
  		.destroy    = redirect_tg_destroy,
  		.targetsize = sizeof(struct nf_nat_ipv4_multi_range_compat),
  		.hooks      = (1 << NF_INET_PRE_ROUTING) |
  		              (1 << NF_INET_LOCAL_OUT),
  		.me         = THIS_MODULE,
  	},
  };
  
  static int __init redirect_tg_init(void)
  {
  	return xt_register_targets(redirect_tg_reg,
  				   ARRAY_SIZE(redirect_tg_reg));
  }
  
  static void __exit redirect_tg_exit(void)
  {
  	xt_unregister_targets(redirect_tg_reg, ARRAY_SIZE(redirect_tg_reg));
  }
  
  module_init(redirect_tg_init);
  module_exit(redirect_tg_exit);
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
  MODULE_DESCRIPTION("Xtables: Connection redirection to localhost");
  MODULE_ALIAS("ip6t_REDIRECT");
  MODULE_ALIAS("ipt_REDIRECT");
  