// SPDX-License-Identifier: GPL-2.0-only
/*
 * This is the 1999 rewrite of IP Firewalling, aiming for kernel 2.3.x.
 *
 * Copyright (C) 1999 Paul `Rusty' Russell & Michael J. Neuling
 * Copyright (C) 2000-2004 Netfilter Core Team <coreteam@netfilter.org>
 */

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

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
MODULE_DESCRIPTION("iptables filter table");

#define FILTER_VALID_HOOKS ((1 << NF_INET_LOCAL_IN) | \
                            (1 << NF_INET_FORWARD) | \
                            (1 << NF_INET_LOCAL_OUT))

static const struct xt_table packet_filter = {
        .name           = "filter",
        .valid_hooks    = FILTER_VALID_HOOKS,
        .me             = THIS_MODULE,
        .af             = NFPROTO_IPV4,
        .priority       = NF_IP_PRI_FILTER,
};

static struct nf_hook_ops *filter_ops __read_mostly;

/* Default to forward because I got too much mail already. */
static bool forward __read_mostly = true;
module_param(forward, bool, 0000);

static int iptable_filter_table_init(struct net *net)
{
        struct ipt_replace *repl;
        int err;

        repl = ipt_alloc_initial_table(&packet_filter);
        if (repl == NULL)
                return -ENOMEM;
        /* Entry 1 is the FORWARD hook */
        ((struct ipt_standard *)repl->entries)[1].target.verdict =
                forward ? -NF_ACCEPT - 1 : NF_DROP - 1;

        err = ipt_register_table(net, &packet_filter, repl, filter_ops);
        kfree(repl);
        return err;
}

static int __net_init iptable_filter_net_init(struct net *net)
{
        if (!forward)
                return iptable_filter_table_init(net);

        return 0;
}

static void __net_exit iptable_filter_net_pre_exit(struct net *net)
{
        ipt_unregister_table_pre_exit(net, "filter");
}

static void __net_exit iptable_filter_net_exit(struct net *net)
{
        ipt_unregister_table_exit(net, "filter");
}

static struct pernet_operations iptable_filter_net_ops = {
        .init = iptable_filter_net_init,
        .pre_exit = iptable_filter_net_pre_exit,
        .exit = iptable_filter_net_exit,
};

static int __init iptable_filter_init(void)
{
        int ret = xt_register_template(&packet_filter,
                                       iptable_filter_table_init);

        if (ret < 0)
                return ret;

        filter_ops = xt_hook_ops_alloc(&packet_filter, ipt_do_table);
        if (IS_ERR(filter_ops)) {
                xt_unregister_template(&packet_filter);
                return PTR_ERR(filter_ops);
        }

        ret = register_pernet_subsys(&iptable_filter_net_ops);
        if (ret < 0) {
                xt_unregister_template(&packet_filter);
                kfree(filter_ops);
                return ret;
        }

        return 0;
}

static void __exit iptable_filter_fini(void)
{
        unregister_pernet_subsys(&iptable_filter_net_ops);
        xt_unregister_template(&packet_filter);
        kfree(filter_ops);
}

module_init(iptable_filter_init);
module_exit(iptable_filter_fini);