ebt_dnat.c

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/*
 *  ebt_dnat
 *
 *  Authors:
 *  Bart De Schuymer <[email protected]>
 *
 *  June, 2002
 *
 */
#include <linux/module.h>
#include <net/sock.h>
#include <linux/netfilter.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_bridge/ebtables.h>
#include <linux/netfilter_bridge/ebt_nat.h>

static unsigned int
ebt_dnat_tg(struct sk_buff *skb, const struct xt_action_param *par)
{
    const struct ebt_nat_info *info = par->targinfo;

    if (!skb_make_writable(skb, 0))
        return EBT_DROP;

    memcpy(eth_hdr(skb)->h_dest, info->mac, ETH_ALEN);
    return info->target;
}

static int ebt_dnat_tg_check(const struct xt_tgchk_param *par)
{
    const struct ebt_nat_info *info = par->targinfo;
    unsigned int hook_mask;

    if (BASE_CHAIN && info->target == EBT_RETURN)
        return -EINVAL;

    hook_mask = par->hook_mask & ~(1 << NF_BR_NUMHOOKS);
    if ((strcmp(par->table, "nat") != 0 ||
        (hook_mask & ~((1 << NF_BR_PRE_ROUTING) |
        (1 << NF_BR_LOCAL_OUT)))) &&
        (strcmp(par->table, "broute") != 0 ||
        hook_mask & ~(1 << NF_BR_BROUTING)))
        return -EINVAL;
    if (INVALID_TARGET)
        return -EINVAL;
    return 0;
}

static struct xt_target ebt_dnat_tg_reg __read_mostly = {
    .name       = "dnat",
    .revision   = 0,
    .family     = NFPROTO_BRIDGE,
    .hooks      = (1 << NF_BR_NUMHOOKS) | (1 << NF_BR_PRE_ROUTING) |
              (1 << NF_BR_LOCAL_OUT) | (1 << NF_BR_BROUTING),
    .target     = ebt_dnat_tg,
    .checkentry = ebt_dnat_tg_check,
    .targetsize = sizeof(struct ebt_nat_info),
    .me     = THIS_MODULE,
};

static int __init ebt_dnat_init(void)
{
    return xt_register_target(&ebt_dnat_tg_reg);
}

static void __exit ebt_dnat_fini(void)
{
    xt_unregister_target(&ebt_dnat_tg_reg);
}

module_init(ebt_dnat_init);
module_exit(ebt_dnat_fini);
MODULE_DESCRIPTION("Ebtables: Destination MAC address translation");
MODULE_LICENSE("GPL");