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gre: fix hard header destination address checking 

ipgre_header() can be called with zero daddr when the gre device is
configured as multipoint tunnel and still has the NOARP flag set (which is
typically cleared by the userspace arp daemon).  If the NOARP packets are
not dropped, ipgre_tunnel_xmit() will take rt->rt_gateway (= NBMA IP) and
use that for route look up (and may lead to bogus xfrm acquires).

The multicast address check is removed as sending to multicast group should
be ok.  In fact, if gre device has a multicast address as destination
ipgre_header is always called with multicast address.

Signed-off-by: Timo Teras <timo.teras@iki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Timo Teräs 2010-03-03 04:01:13 +00:00 committed by David S. Miller
parent c839d30a41
commit 6d55cb91a0
1 changed files with 2 additions and 5 deletions
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7
net/ipv4/ip_gre.c
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@ -1144,12 +1144,9 @@ static int ipgre_header(struct sk_buff *skb, struct net_device *dev,
if (saddr)
memcpy(&iph->saddr, saddr, 4);
if (daddr) {
if (daddr)
memcpy(&iph->daddr, daddr, 4);
return t->hlen;
}
if (iph->daddr && !ipv4_is_multicast(iph->daddr))
if (iph->daddr)
return t->hlen;
return -t->hlen;