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/*
* ebt_arp
*
* Authors:
* Bart De Schuymer <bart.de.schuymer@pandora.be>
* Tim Gardner <timg@tpi.com>
*
* April, 2002
*
*/
#include <linux/netfilter_bridge/ebtables.h>
#include <linux/netfilter_bridge/ebt_arp.h>
#include <linux/if_arp.h>
#include <linux/module.h>
static int ebt_filter_arp(const struct sk_buff *skb, const struct net_device *in,
const struct net_device *out, const void *data, unsigned int datalen)
{
struct ebt_arp_info *info = (struct ebt_arp_info *)data;
if (info->bitmask & EBT_ARP_OPCODE && FWINV(info->opcode !=
((*skb).nh.arph)->ar_op, EBT_ARP_OPCODE))
return EBT_NOMATCH;
if (info->bitmask & EBT_ARP_HTYPE && FWINV(info->htype !=
((*skb).nh.arph)->ar_hrd, EBT_ARP_HTYPE))
return EBT_NOMATCH;
if (info->bitmask & EBT_ARP_PTYPE && FWINV(info->ptype !=
((*skb).nh.arph)->ar_pro, EBT_ARP_PTYPE))
return EBT_NOMATCH;
if (info->bitmask & (EBT_ARP_SRC_IP | EBT_ARP_DST_IP))
{
uint32_t arp_len = sizeof(struct arphdr) +
(2 * (((*skb).nh.arph)->ar_hln)) +
(2 * (((*skb).nh.arph)->ar_pln));
uint32_t dst;
uint32_t src;
// Make sure the packet is long enough.
if ((((*skb).nh.raw) + arp_len) > (*skb).tail)
return EBT_NOMATCH;
// IPv4 addresses are always 4 bytes.
if (((*skb).nh.arph)->ar_pln != sizeof(uint32_t))
return EBT_NOMATCH;
if (info->bitmask & EBT_ARP_SRC_IP) {
memcpy(&src, ((*skb).nh.raw) + sizeof(struct arphdr) +
((*skb).nh.arph)->ar_hln, sizeof(uint32_t));
if (FWINV(info->saddr != (src & info->smsk),
EBT_ARP_SRC_IP))
return EBT_NOMATCH;
}
if (info->bitmask & EBT_ARP_DST_IP) {
memcpy(&dst, ((*skb).nh.raw)+sizeof(struct arphdr) +
(2*(((*skb).nh.arph)->ar_hln)) +
(((*skb).nh.arph)->ar_pln), sizeof(uint32_t));
if (FWINV(info->daddr != (dst & info->dmsk),
EBT_ARP_DST_IP))
return EBT_NOMATCH;
}
}
return EBT_MATCH;
}
static int ebt_arp_check(const char *tablename, unsigned int hookmask,
const struct ebt_entry *e, void *data, unsigned int datalen)
{
struct ebt_arp_info *info = (struct ebt_arp_info *)data;
if (datalen != sizeof(struct ebt_arp_info))
return -EINVAL;
if ((e->ethproto != __constant_htons(ETH_P_ARP) &&
e->ethproto != __constant_htons(ETH_P_RARP)) ||
e->invflags & EBT_IPROTO)
return -EINVAL;
if (info->bitmask & ~EBT_ARP_MASK || info->invflags & ~EBT_ARP_MASK)
return -EINVAL;
return 0;
}
static struct ebt_match filter_arp =
{
{NULL, NULL}, EBT_ARP_MATCH, ebt_filter_arp, ebt_arp_check, NULL,
THIS_MODULE
};
static int __init init(void)
{
return ebt_register_match(&filter_arp);
}
static void __exit fini(void)
{
ebt_unregister_match(&filter_arp);
}
module_init(init);
module_exit(fini);
MODULE_LICENSE("GPL");
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