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// SPDX-License-Identifier: GPL-2.0-only
/*
* ebt_arp
*
* Authors:
* Bart De Schuymer <bdschuym@pandora.be>
* Tim Gardner <timg@tpi.com>
*
* April, 2002
*
*/
#include <linux/if_arp.h>
#include <linux/if_ether.h>
#include <linux/module.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_bridge/ebtables.h>
#include <linux/netfilter_bridge/ebt_arp.h>
static bool
ebt_arp_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
const struct ebt_arp_info *info = par->matchinfo;
const struct arphdr *ah;
struct arphdr _arph;
ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
if (ah == NULL)
return false;
if ((info->bitmask & EBT_ARP_OPCODE) &&
NF_INVF(info, EBT_ARP_OPCODE, info->opcode != ah->ar_op))
return false;
if ((info->bitmask & EBT_ARP_HTYPE) &&
NF_INVF(info, EBT_ARP_HTYPE, info->htype != ah->ar_hrd))
return false;
if ((info->bitmask & EBT_ARP_PTYPE) &&
NF_INVF(info, EBT_ARP_PTYPE, info->ptype != ah->ar_pro))
return false;
if (info->bitmask & (EBT_ARP_SRC_IP | EBT_ARP_DST_IP | EBT_ARP_GRAT)) {
const __be32 *sap, *dap;
__be32 saddr, daddr;
if (ah->ar_pln != sizeof(__be32) || ah->ar_pro != htons(ETH_P_IP))
return false;
sap = skb_header_pointer(skb, sizeof(struct arphdr) +
ah->ar_hln, sizeof(saddr),
&saddr);
if (sap == NULL)
return false;
dap = skb_header_pointer(skb, sizeof(struct arphdr) +
2*ah->ar_hln+sizeof(saddr),
sizeof(daddr), &daddr);
if (dap == NULL)
return false;
if ((info->bitmask & EBT_ARP_SRC_IP) &&
NF_INVF(info, EBT_ARP_SRC_IP,
info->saddr != (*sap & info->smsk)))
return false;
if ((info->bitmask & EBT_ARP_DST_IP) &&
NF_INVF(info, EBT_ARP_DST_IP,
info->daddr != (*dap & info->dmsk)))
return false;
if ((info->bitmask & EBT_ARP_GRAT) &&
NF_INVF(info, EBT_ARP_GRAT, *dap != *sap))
return false;
}
if (info->bitmask & (EBT_ARP_SRC_MAC | EBT_ARP_DST_MAC)) {
const unsigned char *mp;
unsigned char _mac[ETH_ALEN];
if (ah->ar_hln != ETH_ALEN || ah->ar_hrd != htons(ARPHRD_ETHER))
return false;
if (info->bitmask & EBT_ARP_SRC_MAC) {
mp = skb_header_pointer(skb, sizeof(struct arphdr),
sizeof(_mac), &_mac);
if (mp == NULL)
return false;
if (NF_INVF(info, EBT_ARP_SRC_MAC,
!ether_addr_equal_masked(mp, info->smaddr,
info->smmsk)))
return false;
}
if (info->bitmask & EBT_ARP_DST_MAC) {
mp = skb_header_pointer(skb, sizeof(struct arphdr) +
ah->ar_hln + ah->ar_pln,
sizeof(_mac), &_mac);
if (mp == NULL)
return false;
if (NF_INVF(info, EBT_ARP_DST_MAC,
!ether_addr_equal_masked(mp, info->dmaddr,
info->dmmsk)))
return false;
}
}
return true;
}
static int ebt_arp_mt_check(const struct xt_mtchk_param *par)
{
const struct ebt_arp_info *info = par->matchinfo;
const struct ebt_entry *e = par->entryinfo;
if ((e->ethproto != htons(ETH_P_ARP) &&
e->ethproto != 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 xt_match ebt_arp_mt_reg __read_mostly = {
.name = "arp",
.revision = 0,
.family = NFPROTO_BRIDGE,
.match = ebt_arp_mt,
.checkentry = ebt_arp_mt_check,
.matchsize = sizeof(struct ebt_arp_info),
.me = THIS_MODULE,
};
static int __init ebt_arp_init(void)
{
return xt_register_match(&ebt_arp_mt_reg);
}
static void __exit ebt_arp_fini(void)
{
xt_unregister_match(&ebt_arp_mt_reg);
}
module_init(ebt_arp_init);
module_exit(ebt_arp_fini);
MODULE_DESCRIPTION("Ebtables: ARP protocol packet match");
MODULE_LICENSE("GPL");
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