root/net/ipv4/netfilter/ipt_REDIRECT.c

DEFINITIONS

1. redirect_tg_check
2. redirect_tg
3. redirect_tg_init
4. redirect_tg_exit

/* Redirect.  Simple mapping which alters dst to a local IP address. */
/* (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2006 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/types.h>
#include <linux/ip.h>
#include <linux/timer.h>
#include <linux/module.h>
#include <linux/netfilter.h>
#include <linux/netdevice.h>
#include <linux/if.h>
#include <linux/inetdevice.h>
#include <net/protocol.h>
#include <net/checksum.h>
#include <linux/netfilter_ipv4.h>
#include <linux/netfilter/x_tables.h>
#include <net/netfilter/nf_nat_rule.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
MODULE_DESCRIPTION("Xtables: Connection redirection to localhost");

/* FIXME: Take multiple ranges --RR */
static bool redirect_tg_check(const struct xt_tgchk_param *par)
{
        const struct nf_nat_multi_range_compat *mr = par->targinfo;

        if (mr->range[0].flags & IP_NAT_RANGE_MAP_IPS) {
                pr_debug("redirect_check: bad MAP_IPS.\n");
                return false;
        }
        if (mr->rangesize != 1) {
                pr_debug("redirect_check: bad rangesize %u.\n", mr->rangesize);
                return false;
        }
        return true;
}

static unsigned int
redirect_tg(struct sk_buff *skb, const struct xt_target_param *par)
{
        struct nf_conn *ct;
        enum ip_conntrack_info ctinfo;
        __be32 newdst;
        const struct nf_nat_multi_range_compat *mr = par->targinfo;
        struct nf_nat_range newrange;

        NF_CT_ASSERT(par->hooknum == NF_INET_PRE_ROUTING ||
                     par->hooknum == NF_INET_LOCAL_OUT);

        ct = nf_ct_get(skb, &ctinfo);
        NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));

        /* Local packets: make them go to loopback */
        if (par->hooknum == NF_INET_LOCAL_OUT)
                newdst = htonl(0x7F000001);
        else {
                struct in_device *indev;
                struct in_ifaddr *ifa;

                newdst = 0;

                rcu_read_lock();
                indev = __in_dev_get_rcu(skb->dev);
                if (indev && (ifa = indev->ifa_list))
                        newdst = ifa->ifa_local;
                rcu_read_unlock();

                if (!newdst)
                        return NF_DROP;
        }

        /* Transfer from original range. */
        newrange = ((struct nf_nat_range)
                { mr->range[0].flags | IP_NAT_RANGE_MAP_IPS,
                  newdst, newdst,
                  mr->range[0].min, mr->range[0].max });

        /* Hand modified range to generic setup. */
        return nf_nat_setup_info(ct, &newrange, IP_NAT_MANIP_DST);
}

static struct xt_target redirect_tg_reg __read_mostly = {
        .name           = "REDIRECT",
        .family         = NFPROTO_IPV4,
        .target         = redirect_tg,
        .targetsize     = sizeof(struct nf_nat_multi_range_compat),
        .table          = "nat",
        .hooks          = (1 << NF_INET_PRE_ROUTING) | (1 << NF_INET_LOCAL_OUT),
        .checkentry     = redirect_tg_check,
        .me             = THIS_MODULE,
};

static int __init redirect_tg_init(void)
{
        return xt_register_target(&redirect_tg_reg);
}

static void __exit redirect_tg_exit(void)
{
        xt_unregister_target(&redirect_tg_reg);
}

module_init(redirect_tg_init);
module_exit(redirect_tg_exit);