// SPDX-License-Identifier: GPL-2.0-only
/* (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
 * (C) 2011 Patrick McHardy <kaber@trash.net>
 */

#include <linux/module.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/ip.h>
#include <net/ip.h>

#include <net/netfilter/nf_nat.h>

struct iptable_nat_pernet {
        struct nf_hook_ops *nf_nat_ops;
};

static unsigned int iptable_nat_net_id __read_mostly;

static const struct xt_table nf_nat_ipv4_table = {
        .name           = "nat",
        .valid_hooks    = (1 << NF_INET_PRE_ROUTING) |
                          (1 << NF_INET_POST_ROUTING) |
                          (1 << NF_INET_LOCAL_OUT) |
                          (1 << NF_INET_LOCAL_IN),
        .me             = THIS_MODULE,
        .af             = NFPROTO_IPV4,
};

static const struct nf_hook_ops nf_nat_ipv4_ops[] = {
        {
                .hook           = ipt_do_table,
                .pf             = NFPROTO_IPV4,
                .hooknum        = NF_INET_PRE_ROUTING,
                .priority       = NF_IP_PRI_NAT_DST,
        },
        {
                .hook           = ipt_do_table,
                .pf             = NFPROTO_IPV4,
                .hooknum        = NF_INET_POST_ROUTING,
                .priority       = NF_IP_PRI_NAT_SRC,
        },
        {
                .hook           = ipt_do_table,
                .pf             = NFPROTO_IPV4,
                .hooknum        = NF_INET_LOCAL_OUT,
                .priority       = NF_IP_PRI_NAT_DST,
        },
        {
                .hook           = ipt_do_table,
                .pf             = NFPROTO_IPV4,
                .hooknum        = NF_INET_LOCAL_IN,
                .priority       = NF_IP_PRI_NAT_SRC,
        },
};

static int ipt_nat_register_lookups(struct net *net)
{
        struct iptable_nat_pernet *xt_nat_net;
        struct nf_hook_ops *ops;
        struct xt_table *table;
        int i, ret;

        xt_nat_net = net_generic(net, iptable_nat_net_id);
        table = xt_find_table(net, NFPROTO_IPV4, "nat");
        if (WARN_ON_ONCE(!table))
                return -ENOENT;

        ops = kmemdup(nf_nat_ipv4_ops, sizeof(nf_nat_ipv4_ops), GFP_KERNEL);
        if (!ops)
                return -ENOMEM;

        for (i = 0; i < ARRAY_SIZE(nf_nat_ipv4_ops); i++) {
                ops[i].priv = table;
                ret = nf_nat_ipv4_register_fn(net, &ops[i]);
                if (ret) {
                        while (i)
                                nf_nat_ipv4_unregister_fn(net, &ops[--i]);

                        kfree(ops);
                        return ret;
                }
        }

        xt_nat_net->nf_nat_ops = ops;
        return 0;
}

static void ipt_nat_unregister_lookups(struct net *net)
{
        struct iptable_nat_pernet *xt_nat_net = net_generic(net, iptable_nat_net_id);
        struct nf_hook_ops *ops = xt_nat_net->nf_nat_ops;
        int i;

        if (!ops)
                return;

        for (i = 0; i < ARRAY_SIZE(nf_nat_ipv4_ops); i++)
                nf_nat_ipv4_unregister_fn(net, &ops[i]);

        kfree(ops);
}

static int iptable_nat_table_init(struct net *net)
{
        struct ipt_replace *repl;
        int ret;

        repl = ipt_alloc_initial_table(&nf_nat_ipv4_table);
        if (repl == NULL)
                return -ENOMEM;

        ret = ipt_register_table(net, &nf_nat_ipv4_table, repl, NULL);
        if (ret < 0) {
                kfree(repl);
                return ret;
        }

        ret = ipt_nat_register_lookups(net);
        if (ret < 0)
                ipt_unregister_table_exit(net, "nat");

        kfree(repl);
        return ret;
}

static void __net_exit iptable_nat_net_pre_exit(struct net *net)
{
        ipt_nat_unregister_lookups(net);
}

static void __net_exit iptable_nat_net_exit(struct net *net)
{
        ipt_unregister_table_exit(net, "nat");
}

static struct pernet_operations iptable_nat_net_ops = {
        .pre_exit = iptable_nat_net_pre_exit,
        .exit   = iptable_nat_net_exit,
        .id     = &iptable_nat_net_id,
        .size   = sizeof(struct iptable_nat_pernet),
};

static int __init iptable_nat_init(void)
{
        int ret;

        /* net->gen->ptr[iptable_nat_net_id] must be allocated
         * before calling iptable_nat_table_init().
         */
        ret = register_pernet_subsys(&iptable_nat_net_ops);
        if (ret < 0)
                return ret;

        ret = xt_register_template(&nf_nat_ipv4_table,
                                   iptable_nat_table_init);
        if (ret < 0)
                unregister_pernet_subsys(&iptable_nat_net_ops);

        return ret;
}

static void __exit iptable_nat_exit(void)
{
        xt_unregister_template(&nf_nat_ipv4_table);
        unregister_pernet_subsys(&iptable_nat_net_ops);
}

module_init(iptable_nat_init);
module_exit(iptable_nat_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("iptables legacy nat table");