// 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);
}

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)
{
        const struct nf_nat_ipv4_multi_range_compat *mr = par->targinfo;
        struct nf_nat_range2 range = {
                .flags       = mr->range[0].flags,
                .min_proto   = mr->range[0].min,
                .max_proto   = mr->range[0].max,
        };

        return nf_nat_redirect_ipv4(skb, &range, 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");