ebt_arpreply.c
/*
* 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_action_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 int 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 -EINVAL;
if (e->ethproto != htons(ETH_P_ARP) ||
e->invflags & EBT_IPROTO)
return -EINVAL;
return 0;
}
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 = 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");