root/net/bridge/netfilter/ebt_snat.c

DEFINITIONS

1. ebt_snat_tg
2. ebt_snat_tg_check
3. ebt_snat_init
4. ebt_snat_fini

/*
 *  ebt_snat
 *
 *      Authors:
 *      Bart De Schuymer <bdschuym@pandora.be>
 *
 *  June, 2002
 *
 */
#include <linux/module.h>
#include <net/sock.h>
#include <linux/if_arp.h>
#include <net/arp.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_snat_tg(struct sk_buff *skb, const struct xt_target_param *par)
{
        const struct ebt_nat_info *info = par->targinfo;

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

        memcpy(eth_hdr(skb)->h_source, info->mac, ETH_ALEN);
        if (!(info->target & NAT_ARP_BIT) &&
            eth_hdr(skb)->h_proto == htons(ETH_P_ARP)) {
                const struct arphdr *ap;
                struct arphdr _ah;

                ap = skb_header_pointer(skb, 0, sizeof(_ah), &_ah);
                if (ap == NULL)
                        return EBT_DROP;
                if (ap->ar_hln != ETH_ALEN)
                        goto out;
                if (skb_store_bits(skb, sizeof(_ah), info->mac,ETH_ALEN))
                        return EBT_DROP;
        }
out:
        return info->target | ~EBT_VERDICT_BITS;
}

static bool ebt_snat_tg_check(const struct xt_tgchk_param *par)
{
        const struct ebt_nat_info *info = par->targinfo;
        int tmp;

        tmp = info->target | ~EBT_VERDICT_BITS;
        if (BASE_CHAIN && tmp == EBT_RETURN)
                return false;

        if (tmp < -NUM_STANDARD_TARGETS || tmp >= 0)
                return false;
        tmp = info->target | EBT_VERDICT_BITS;
        if ((tmp & ~NAT_ARP_BIT) != ~NAT_ARP_BIT)
                return false;
        return true;
}

static struct xt_target ebt_snat_tg_reg __read_mostly = {
        .name           = "snat",
        .revision       = 0,
        .family         = NFPROTO_BRIDGE,
        .table          = "nat",
        .hooks          = (1 << NF_BR_NUMHOOKS) | (1 << NF_BR_POST_ROUTING),
        .target         = ebt_snat_tg,
        .checkentry     = ebt_snat_tg_check,
        .targetsize     = XT_ALIGN(sizeof(struct ebt_nat_info)),
        .me             = THIS_MODULE,
};

static int __init ebt_snat_init(void)
{
        return xt_register_target(&ebt_snat_tg_reg);
}

static void __exit ebt_snat_fini(void)
{
        xt_unregister_target(&ebt_snat_tg_reg);
}

module_init(ebt_snat_init);
module_exit(ebt_snat_fini);
MODULE_DESCRIPTION("Ebtables: Source MAC address translation");
MODULE_LICENSE("GPL");