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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

 *

 * Extended to all five netfilter hooks by Brad Chapman & Harald Welte

 */

#include <linux/config.h>

#include <linux/module.h>

#include <linux/netfilter_ipv4/ip_tables.h>

#include <linux/netdevice.h>

#include <linux/skbuff.h>

#include <net/sock.h>

#include <net/route.h>

#include <linux/ip.h>

#define MANGLE_VALID_HOOKS ((1 << NF_IP_PRE_ROUTING) | \

                            (1 << NF_IP_LOCAL_IN) | \

                            (1 << NF_IP_FORWARD) | \

                            (1 << NF_IP_LOCAL_OUT) | \

                            (1 << NF_IP_POST_ROUTING))

/* 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;

};

/* Ouch - five different hooks? Maybe this should be a config option..... -- BC */

static struct

{

        struct ipt_replace repl;

        struct ipt_standard entries[5];

        struct ipt_error term;

} initial_table __initdata

= { { "mangle", MANGLE_VALID_HOOKS, 6,

      sizeof(struct ipt_standard) * 5 + sizeof(struct ipt_error),

      { [NF_IP_PRE_ROUTING]     0,

        [NF_IP_LOCAL_IN]        sizeof(struct ipt_standard),

        [NF_IP_FORWARD]         sizeof(struct ipt_standard) * 2,

        [NF_IP_LOCAL_OUT]       sizeof(struct ipt_standard) * 3,

        [NF_IP_POST_ROUTING]    sizeof(struct ipt_standard) * 4 },

      { [NF_IP_PRE_ROUTING]     0,

        [NF_IP_LOCAL_IN]        sizeof(struct ipt_standard),

        [NF_IP_FORWARD]         sizeof(struct ipt_standard) * 2,

        [NF_IP_LOCAL_OUT]       sizeof(struct ipt_standard) * 3,

        [NF_IP_POST_ROUTING]    sizeof(struct ipt_standard) * 4 },

      0, NULL, { } },

    {

            /* PRE_ROUTING */

            { { { { 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_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 } },

            /* POST_ROUTING */

            { { { { 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_mangler

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

    MANGLE_VALID_HOOKS, RW_LOCK_UNLOCKED, NULL, THIS_MODULE };

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

static unsigned int

ipt_route_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_mangler, NULL);

}

static unsigned int

ipt_local_hook(unsigned int hook,

                   struct sk_buff **pskb,

                   const struct net_device *in,

                   const struct net_device *out,

                   int (*okfn)(struct sk_buff *))

{

        unsigned int ret;

        u_int8_t tos;

        u_int32_t saddr, daddr;

        unsigned long nfmark;

        /* 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;

        }

        /* Save things which could affect route */

        nfmark = (*pskb)->nfmark;

        saddr = (*pskb)->nh.iph->saddr;

        daddr = (*pskb)->nh.iph->daddr;

        tos = (*pskb)->nh.iph->tos;

        ret = ipt_do_table(pskb, hook, in, out, &packet_mangler, NULL);

        /* Reroute for ANY change. */

        if (ret != NF_DROP && ret != NF_STOLEN && ret != NF_QUEUE

            && ((*pskb)->nh.iph->saddr != saddr

                || (*pskb)->nh.iph->daddr != daddr

                || (*pskb)->nfmark != nfmark

                || (*pskb)->nh.iph->tos != tos))

                return ip_route_me_harder(pskb) == 0 ? ret : NF_DROP;

        return ret;

}

static struct nf_hook_ops ipt_ops[]

= { { { NULL, NULL }, ipt_route_hook, PF_INET, NF_IP_PRE_ROUTING,

        NF_IP_PRI_MANGLE },

    { { NULL, NULL }, ipt_route_hook, PF_INET, NF_IP_LOCAL_IN,

        NF_IP_PRI_MANGLE },

    { { NULL, NULL }, ipt_route_hook, PF_INET, NF_IP_FORWARD,

        NF_IP_PRI_MANGLE },

    { { NULL, NULL }, ipt_local_hook, PF_INET, NF_IP_LOCAL_OUT,

        NF_IP_PRI_MANGLE },

    { { NULL, NULL }, ipt_route_hook, PF_INET, NF_IP_POST_ROUTING,

        NF_IP_PRI_MANGLE }

};

static int __init init(void)

{

        int ret;

        /* Register table */

        ret = ipt_register_table(&packet_mangler);

        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;

        ret = nf_register_hook(&ipt_ops[3]);

        if (ret < 0)

                goto cleanup_hook2;

        ret = nf_register_hook(&ipt_ops[4]);

        if (ret < 0)

                goto cleanup_hook3;

        return ret;

 cleanup_hook3:

        nf_unregister_hook(&ipt_ops[3]);

 cleanup_hook2:

        nf_unregister_hook(&ipt_ops[2]);

 cleanup_hook1:

        nf_unregister_hook(&ipt_ops[1]);

 cleanup_hook0:

        nf_unregister_hook(&ipt_ops[0]);

 cleanup_table:

        ipt_unregister_table(&packet_mangler);

        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_mangler);

}

module_init(init);

module_exit(fini);

MODULE_LICENSE("GPL");