netdev - Re: [RFC] net: ipv4: drop unicast encapsulated in L2 multicast

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Date:	Wed, 27 Aug 2014 13:29:27 +0200
From:	Johannes Berg <johannes@...solutions.net>
To:	Julian Anastasov <ja@....bg>
Cc:	David Miller <davem@...emloft.net>, linux-wireless@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: [RFC] net: ipv4: drop unicast encapsulated in L2 multicast

On Wed, 2014-08-27 at 13:23 +0300, Julian Anastasov wrote:

> 	CLUSTERIP works in LOCAL_IN. My preference is to
> add checks in every protocol where it is missing but if
> you prefer a global check, ip_local_deliver_finish() is
> a good place: CLUSTERIP already changed pkt_type to
> PACKET_HOST. For example:
> 
> 	if (!(skb_rtable(skb)->rt_flags &
> 	      (RTCF_BROADCAST | RTCF_MULTICAST)) &&
> 	    (skb->pkt_type == PACKET_BROADCAST ||
> 	     skb->pkt_type == PACKET_MULTICAST)) {
> 		kfree_skb(skb);
> 		return;
> 	}
> 
> 	By this way we protect the local stack globally.

I suppose that'd work then?

> BTW, what kind of packets (protocol) we want to drop? UDP?

All IP protocols, this comes either from the IPv4 RFC (1122) or from the
wireless issue which affects all protocols.

> 	As for ip_forward(), there is already check for
> PACKET_HOST.
> 
> 	Not sure, may be a MIB counter for such drops
> would be useful.

Yeah, maybe, not sure.

johannes


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