/*
 * 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>
 *
 * 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/module.h>
#include <linux/moduleparam.h>
#include <linux/netfilter_ipv4/ip_tables.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 struct
{
        struct ipt_replace repl;
        struct ipt_standard entries[3];
        struct ipt_error term;
} initial_table __net_initdata = {
        .repl = {
                .name = "filter",
                .valid_hooks = FILTER_VALID_HOOKS,
                .num_entries = 4,
                .size = sizeof(struct ipt_standard) * 3 + sizeof(struct ipt_error),
                .hook_entry = {
                        [NF_INET_LOCAL_IN] = 0,
                        [NF_INET_FORWARD] = sizeof(struct ipt_standard),
                        [NF_INET_LOCAL_OUT] = sizeof(struct ipt_standard) * 2,
                },
                .underflow = {
                        [NF_INET_LOCAL_IN] = 0,
                        [NF_INET_FORWARD] = sizeof(struct ipt_standard),
                        [NF_INET_LOCAL_OUT] = sizeof(struct ipt_standard) * 2,
                },
        },
        .entries = {
                IPT_STANDARD_INIT(NF_ACCEPT),   /* LOCAL_IN */
                IPT_STANDARD_INIT(NF_ACCEPT),   /* FORWARD */
                IPT_STANDARD_INIT(NF_ACCEPT),   /* LOCAL_OUT */
        },
        .term = IPT_ERROR_INIT,                 /* ERROR */
};

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

/* The work comes in here from netfilter.c. */
static unsigned int
ipt_local_in_hook(unsigned int hook,
                  struct sk_buff *skb,
                  const struct net_device *in,
                  const struct net_device *out,
                  int (*okfn)(struct sk_buff *))
{
        return ipt_do_table(skb, hook, in, out,
                            dev_net(in)->ipv4.iptable_filter);
}

static unsigned int
ipt_hook(unsigned int hook,
         struct sk_buff *skb,
         const struct net_device *in,
         const struct net_device *out,
         int (*okfn)(struct sk_buff *))
{
        return ipt_do_table(skb, hook, in, out,
                            dev_net(in)->ipv4.iptable_filter);
}

static unsigned int
ipt_local_out_hook(unsigned int hook,
                   struct sk_buff *skb,
                   const struct net_device *in,
                   const struct net_device *out,
                   int (*okfn)(struct sk_buff *))
{
        /* root is playing with raw sockets. */
        if (skb->len < sizeof(struct iphdr) ||
            ip_hdrlen(skb) < sizeof(struct iphdr))
                return NF_ACCEPT;
        return ipt_do_table(skb, hook, in, out,
                            dev_net(out)->ipv4.iptable_filter);
}

static struct nf_hook_ops ipt_ops[] __read_mostly = {
        {
                .hook           = ipt_local_in_hook,
                .owner          = THIS_MODULE,
                .pf             = NFPROTO_IPV4,
                .hooknum        = NF_INET_LOCAL_IN,
                .priority       = NF_IP_PRI_FILTER,
        },
        {
                .hook           = ipt_hook,
                .owner          = THIS_MODULE,
                .pf             = NFPROTO_IPV4,
                .hooknum        = NF_INET_FORWARD,
                .priority       = NF_IP_PRI_FILTER,
        },
        {
                .hook           = ipt_local_out_hook,
                .owner          = THIS_MODULE,
                .pf             = NFPROTO_IPV4,
                .hooknum        = NF_INET_LOCAL_OUT,
                .priority       = NF_IP_PRI_FILTER,
        },
};

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

static int __net_init iptable_filter_net_init(struct net *net)
{
        /* Register table */
        net->ipv4.iptable_filter =
                ipt_register_table(net, &packet_filter, &initial_table.repl);
        if (IS_ERR(net->ipv4.iptable_filter))
                return PTR_ERR(net->ipv4.iptable_filter);
        return 0;
}

static void __net_exit iptable_filter_net_exit(struct net *net)
{
        ipt_unregister_table(net->ipv4.iptable_filter);
}

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

static int __init iptable_filter_init(void)
{
        int ret;

        if (forward < 0 || forward > NF_MAX_VERDICT) {
                printk("iptables forward must be 0 or 1\n");
                return -EINVAL;
        }

        /* Entry 1 is the FORWARD hook */
        initial_table.entries[1].target.verdict = -forward - 1;

        ret = register_pernet_subsys(&iptable_filter_net_ops);
        if (ret < 0)
                return ret;

        /* Register hooks */
        ret = nf_register_hooks(ipt_ops, ARRAY_SIZE(ipt_ops));
        if (ret < 0)
                goto cleanup_table;

        return ret;

 cleanup_table:
        unregister_pernet_subsys(&iptable_filter_net_ops);
        return ret;
}

static void __exit iptable_filter_fini(void)
{
        nf_unregister_hooks(ipt_ops, ARRAY_SIZE(ipt_ops));
        unregister_pernet_subsys(&iptable_filter_net_ops);
}

module_init(iptable_filter_init);
module_exit(iptable_filter_fini);