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/*

 * This is the 1999 rewrite of IP Firewalling, aiming for kernel 2.3.x.

 *

 * Copyright (C) 1999 Paul `Rusty' Russell & Michael J. Neuling

 */

#include <linux/module.h>

#include <linux/netfilter_ipv4/ip_tables.h>

#define FILTER_VALID_HOOKS ((1 << NF_IP_LOCAL_IN) | (1 << NF_IP_FORWARD) | (1 << NF_IP_LOCAL_OUT))

/* Standard entry. */

struct ipt_standard

{

        struct ipt_entry entry;

        struct ipt_standard_target target;

};

struct ipt_error_target

{

        struct ipt_entry_target target;

        char errorname[IPT_FUNCTION_MAXNAMELEN];

};

struct ipt_error

{

        struct ipt_entry entry;

        struct ipt_error_target target;

};

static struct

{

        struct ipt_replace repl;

        struct ipt_standard entries[3];

        struct ipt_error term;

} initial_table __initdata

= { { "filter", FILTER_VALID_HOOKS, 4,

      sizeof(struct ipt_standard) * 3 + sizeof(struct ipt_error),

      { [NF_IP_LOCAL_IN] 0,

        [NF_IP_FORWARD] sizeof(struct ipt_standard),

        [NF_IP_LOCAL_OUT] sizeof(struct ipt_standard) * 2 },

      { [NF_IP_LOCAL_IN] 0,

        [NF_IP_FORWARD] sizeof(struct ipt_standard),

        [NF_IP_LOCAL_OUT] sizeof(struct ipt_standard) * 2 },

      0, NULL, { } },

    {

            /* LOCAL_IN */

            { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },

                0,

                sizeof(struct ipt_entry),

                sizeof(struct ipt_standard),

                0, { 0, 0 }, { } },

              { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },

                -NF_ACCEPT - 1 } },

            /* FORWARD */

            { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },

                0,

                sizeof(struct ipt_entry),

                sizeof(struct ipt_standard),

                0, { 0, 0 }, { } },

              { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },

                -NF_ACCEPT - 1 } },

            /* LOCAL_OUT */

            { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },

                0,

                sizeof(struct ipt_entry),

                sizeof(struct ipt_standard),

                0, { 0, 0 }, { } },

              { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },

                -NF_ACCEPT - 1 } }

    },

    /* ERROR */

    { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },

        0,

        sizeof(struct ipt_entry),

        sizeof(struct ipt_error),

        0, { 0, 0 }, { } },

      { { { { IPT_ALIGN(sizeof(struct ipt_error_target)), IPT_ERROR_TARGET } },

          { } },

        "ERROR"

      }

    }

};

static struct ipt_table packet_filter

= { { NULL, NULL }, "filter", &initial_table.repl,

    FILTER_VALID_HOOKS, RW_LOCK_UNLOCKED, NULL, THIS_MODULE };

/* The work comes in here from netfilter.c. */

static unsigned int

ipt_hook(unsigned int hook,

         struct sk_buff **pskb,

         const struct net_device *in,

         const struct net_device *out,

         int (*okfn)(struct sk_buff *))

{

        return ipt_do_table(pskb, hook, in, out, &packet_filter, NULL);

}

static unsigned int

ipt_local_out_hook(unsigned int hook,

                   struct sk_buff **pskb,

                   const struct net_device *in,

                   const struct net_device *out,

                   int (*okfn)(struct sk_buff *))

{

        /* root is playing with raw sockets. */

        if ((*pskb)->len < sizeof(struct iphdr)

            || (*pskb)->nh.iph->ihl * 4 < sizeof(struct iphdr)) {

                if (net_ratelimit())

                        printk("ipt_hook: happy cracking.\n");

                return NF_ACCEPT;

        }

        return ipt_do_table(pskb, hook, in, out, &packet_filter, NULL);

}

static struct nf_hook_ops ipt_ops[]

= { { { NULL, NULL }, ipt_hook, PF_INET, NF_IP_LOCAL_IN, NF_IP_PRI_FILTER },

    { { NULL, NULL }, ipt_hook, PF_INET, NF_IP_FORWARD, NF_IP_PRI_FILTER },

    { { NULL, NULL }, ipt_local_out_hook, PF_INET, NF_IP_LOCAL_OUT,

                NF_IP_PRI_FILTER }

};

/* Default to forward because I got too much mail already. */

static int forward = NF_ACCEPT;

MODULE_PARM(forward, "i");

static int __init 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;

        /* Register table */

        ret = ipt_register_table(&packet_filter);

        if (ret < 0)

                return ret;

        /* Register hooks */

        ret = nf_register_hook(&ipt_ops[0]);

        if (ret < 0)

                goto cleanup_table;

        ret = nf_register_hook(&ipt_ops[1]);

        if (ret < 0)

                goto cleanup_hook0;

        ret = nf_register_hook(&ipt_ops[2]);

        if (ret < 0)

                goto cleanup_hook1;

        return ret;

 cleanup_hook1:

        nf_unregister_hook(&ipt_ops[1]);

 cleanup_hook0:

        nf_unregister_hook(&ipt_ops[0]);

 cleanup_table:

        ipt_unregister_table(&packet_filter);

        return ret;

}

static void __exit fini(void)

{

        unsigned int i;

        for (i = 0; i < sizeof(ipt_ops)/sizeof(struct nf_hook_ops); i++)

                nf_unregister_hook(&ipt_ops[i]);

        ipt_unregister_table(&packet_filter);

}

module_init(init);

module_exit(fini);

MODULE_LICENSE("GPL");