netdev - Re: [PATCH 1/1] ipv4: arp: update neighbour address when a gratuitous arp is received and arp

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Message-ID: <20131225113710.GR14073@order.stressinduktion.org>
Date:	Wed, 25 Dec 2013 12:37:10 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Salam Noureddine <noureddine@...stanetworks.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Patrick McHardy <kaber@...sh.net>, netdev@...r.kernel.org
Subject: Re: [PATCH 1/1] ipv4: arp: update neighbour address when a gratuitous arp is received and arp_accept is set

On Tue, Dec 24, 2013 at 02:17:02PM -0800, Salam Noureddine wrote:
> Gratuitous arp packets are useful in switchover scenarios to update
> client arp tables as quickly as possible. Currently, the mac address
> of a neighbour is only updated after a locktime period has elapsed
> since the last update. In most use cases such delays are unacceptable
> for network admins. Moreover, the "updated" field of the neighbour
> stucture doesn't record the last time the address of a neighbour
> changed but records any change that happens to the neighbour. This is
> clearly a bug since locktime uses that field as meaning "addr_updated".
> With this observation, I was able to perpetuate a stale address by
> sending a stream of gratuitous arp packets spaced less than locktime
> apart. With this change the address is updated when a gratuitous arp
> is received and the arp_accept sysctl is set.
> 
> Signed-off-by: Salam Noureddine <noureddine@...stanetworks.com>

Acked-by: Hannes Frederic Sowa <hannes@...essinduktion.org>

Thanks!

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