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[NETFILTER]: ebt_arp: add gratuitous arp filtering 

The attached patch adds gratuitous arp filtering, more precisely: it
allows checking that the IPv4 source address matches the IPv4
destination address inside the ARP header. It also adds a check for the
hardware address type when matching MAC addresses (nothing critical,
just for better consistency).

Signed-off-by: Bart De Schuymer <bdschuym@pandora.be>
Acked-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Bart De Schuymer 2007-04-12 22:15:06 -07:00 committed by David S. Miller
parent 516299d2f5
commit c15bf6e699
2 changed files with 25 additions and 27 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/linux/netfilter_bridge/ebt_arp.h
View File

@ -8,8 +8,10 @@
#define EBT_ARP_DST_IP 0x10
#define EBT_ARP_SRC_MAC 0x20
#define EBT_ARP_DST_MAC 0x40
#define EBT_ARP_GRAT 0x80
#define EBT_ARP_MASK (EBT_ARP_OPCODE | EBT_ARP_HTYPE | EBT_ARP_PTYPE | \
EBT_ARP_SRC_IP | EBT_ARP_DST_IP | EBT_ARP_SRC_MAC | EBT_ARP_DST_MAC)
EBT_ARP_SRC_IP | EBT_ARP_DST_IP | EBT_ARP_SRC_MAC | EBT_ARP_DST_MAC | \
EBT_ARP_GRAT)
#define EBT_ARP_MATCH "arp"
struct ebt_arp_info

40
net/bridge/netfilter/ebt_arp.c
View File

@ -35,40 +35,36 @@ static int ebt_filter_arp(const struct sk_buff *skb, const struct net_device *in
return EBT_NOMATCH;
if (info->bitmask & (EBT_ARP_SRC_IP | EBT_ARP_DST_IP)) {
__be32 _addr, *ap;
__be32 saddr, daddr, *sap, *dap;
/* IPv4 addresses are always 4 bytes */
if (ah->ar_pln != sizeof(__be32))
if (ah->ar_pln != sizeof(__be32) || ah->ar_pro != htons(ETH_P_IP))
return EBT_NOMATCH;
if (info->bitmask & EBT_ARP_SRC_IP) {
ap = skb_header_pointer(skb, sizeof(struct arphdr) +
ah->ar_hln, sizeof(_addr),
&_addr);
if (ap == NULL)
sap = skb_header_pointer(skb, sizeof(struct arphdr) +
ah->ar_hln, sizeof(saddr),
&saddr);
if (sap == NULL)
return EBT_NOMATCH;
if (FWINV(info->saddr != (*ap & info->smsk),
EBT_ARP_SRC_IP))
dap = skb_header_pointer(skb, sizeof(struct arphdr) +
2*ah->ar_hln+sizeof(saddr),
sizeof(daddr), &daddr);
if (dap == NULL)
return EBT_NOMATCH;
}
if (info->bitmask & EBT_ARP_DST_IP) {
ap = skb_header_pointer(skb, sizeof(struct arphdr) +
2*ah->ar_hln+sizeof(__be32),
sizeof(_addr), &_addr);
if (ap == NULL)
if (info->bitmask & EBT_ARP_SRC_IP &&
FWINV(info->saddr != (*sap & info->smsk), EBT_ARP_SRC_IP))
return EBT_NOMATCH;
if (FWINV(info->daddr != (*ap & info->dmsk),
EBT_ARP_DST_IP))
if (info->bitmask & EBT_ARP_DST_IP &&
FWINV(info->daddr != (*dap & info->dmsk), EBT_ARP_DST_IP))
return EBT_NOMATCH;
if (info->bitmask & EBT_ARP_GRAT &&
FWINV(*dap != *sap, EBT_ARP_GRAT))
return EBT_NOMATCH;
}
}
if (info->bitmask & (EBT_ARP_SRC_MAC | EBT_ARP_DST_MAC)) {
unsigned char _mac[ETH_ALEN], *mp;
uint8_t verdict, i;
/* MAC addresses are 6 bytes */
if (ah->ar_hln != ETH_ALEN)
if (ah->ar_hln != ETH_ALEN || ah->ar_hrd != htons(ARPHRD_ETHER))
return EBT_NOMATCH;
if (info->bitmask & EBT_ARP_SRC_MAC) {
mp = skb_header_pointer(skb, sizeof(struct arphdr),