netdev - Re: net/arp: ARP cache aging failed.

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Date:   Fri, 25 Nov 2016 10:18:40 +0200 (EET)
From:   Julian Anastasov <ja@....bg>
To:     Hannes Frederic Sowa <hannes@...essinduktion.org>
cc:     YueHaibing <yuehaibing@...wei.com>,
        Eric Dumazet <eric.dumazet@...il.com>, davem@...emloft.net,
        netdev@...r.kernel.org
Subject: Re: net/arp: ARP cache aging failed.


	Hello,

On Thu, 24 Nov 2016, Hannes Frederic Sowa wrote:

> I think some people are thinking about it already (me also ;) ).
> 
> But it is not easy to come up with a solution. First of all, we need to
> look up the L2 address again in the neighbor cache and confirm the
> appropriate neighbor. Secondly we should only do that for packets which
> we can actually confirm (that means passing the TCP recv tests or some
> other kind of confirmation besides simply spamming the box etc). Also it
> needs to be fast.

	Another option would be to add similar bit to
struct sock (sk_dst_pending_confirm), may be ip_finish_output2
can propagate it to dst_neigh_output via new arg and then to
reset it. Or to change n->confirmed via some new inline sock
function instead of changing dst_neigh_output. At this place 
skb->sk is optional, may be we need (skb->sk && dst ==
skb->sk->sk_dst_cache) check. Also, when sk_dst_cache changes
we should clear this flag.

Regards

--
Julian Anastasov <ja@....bg>