root/net/bridge/netfilter/ebt_arpreply.c

DEFINITIONS

1. ebt_arpreply_tg
2. ebt_arpreply_tg_check
3. ebt_arpreply_init
4. ebt_arpreply_fini

/*
 *  ebt_arpreply
 *
 *      Authors:
 *      Grzegorz Borowiak <grzes@gnu.univ.gda.pl>
 *      Bart De Schuymer <bdschuym@pandora.be>
 *
 *  August, 2003
 *
 */
#include <linux/if_arp.h>
#include <net/arp.h>
#include <linux/module.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_bridge/ebtables.h>
#include <linux/netfilter_bridge/ebt_arpreply.h>

static unsigned int
ebt_arpreply_tg(struct sk_buff *skb, const struct xt_target_param *par)
{
        const struct ebt_arpreply_info *info = par->targinfo;
        const __be32 *siptr, *diptr;
        __be32 _sip, _dip;
        const struct arphdr *ap;
        struct arphdr _ah;
        const unsigned char *shp;
        unsigned char _sha[ETH_ALEN];

        ap = skb_header_pointer(skb, 0, sizeof(_ah), &_ah);
        if (ap == NULL)
                return EBT_DROP;

        if (ap->ar_op != htons(ARPOP_REQUEST) ||
            ap->ar_hln != ETH_ALEN ||
            ap->ar_pro != htons(ETH_P_IP) ||
            ap->ar_pln != 4)
                return EBT_CONTINUE;

        shp = skb_header_pointer(skb, sizeof(_ah), ETH_ALEN, &_sha);
        if (shp == NULL)
                return EBT_DROP;

        siptr = skb_header_pointer(skb, sizeof(_ah) + ETH_ALEN,
                                   sizeof(_sip), &_sip);
        if (siptr == NULL)
                return EBT_DROP;

        diptr = skb_header_pointer(skb,
                                   sizeof(_ah) + 2 * ETH_ALEN + sizeof(_sip),
                                   sizeof(_dip), &_dip);
        if (diptr == NULL)
                return EBT_DROP;

        arp_send(ARPOP_REPLY, ETH_P_ARP, *siptr, (struct net_device *)par->in,
                 *diptr, shp, info->mac, shp);

        return info->target;
}

static bool ebt_arpreply_tg_check(const struct xt_tgchk_param *par)
{
        const struct ebt_arpreply_info *info = par->targinfo;
        const struct ebt_entry *e = par->entryinfo;

        if (BASE_CHAIN && info->target == EBT_RETURN)
                return false;
        if (e->ethproto != htons(ETH_P_ARP) ||
            e->invflags & EBT_IPROTO)
                return false;
        return true;
}

static struct xt_target ebt_arpreply_tg_reg __read_mostly = {
        .name           = "arpreply",
        .revision       = 0,
        .family         = NFPROTO_BRIDGE,
        .table          = "nat",
        .hooks          = (1 << NF_BR_NUMHOOKS) | (1 << NF_BR_PRE_ROUTING),
        .target         = ebt_arpreply_tg,
        .checkentry     = ebt_arpreply_tg_check,
        .targetsize     = XT_ALIGN(sizeof(struct ebt_arpreply_info)),
        .me             = THIS_MODULE,
};

static int __init ebt_arpreply_init(void)
{
        return xt_register_target(&ebt_arpreply_tg_reg);
}

static void __exit ebt_arpreply_fini(void)
{
        xt_unregister_target(&ebt_arpreply_tg_reg);
}

module_init(ebt_arpreply_init);
module_exit(ebt_arpreply_fini);
MODULE_DESCRIPTION("Ebtables: ARP reply target");
MODULE_LICENSE("GPL");