[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>
diff --git a/net/bridge/netfilter/ebt_arp.c b/net/bridge/netfilter/ebt_arp.c
index 9c59980..1a46952 100644
--- a/net/bridge/netfilter/ebt_arp.c
+++ b/net/bridge/netfilter/ebt_arp.c
@@ -35,40 +35,36 @@
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)
- return EBT_NOMATCH;
- if (FWINV(info->saddr != (*ap & info->smsk),
- EBT_ARP_SRC_IP))
- 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)
- return EBT_NOMATCH;
- if (FWINV(info->daddr != (*ap & info->dmsk),
- EBT_ARP_DST_IP))
- return EBT_NOMATCH;
- }
+ sap = skb_header_pointer(skb, sizeof(struct arphdr) +
+ ah->ar_hln, sizeof(saddr),
+ &saddr);
+ if (sap == NULL)
+ return EBT_NOMATCH;
+ 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_SRC_IP &&
+ FWINV(info->saddr != (*sap & info->smsk), EBT_ARP_SRC_IP))
+ return EBT_NOMATCH;
+ 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),