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

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Message-ID: <20131220140617.09a672f7@nehalam.linuxnetplumber.net>
Date:	Fri, 20 Dec 2013 14:06:17 -0800
From:	Stephen Hemminger <stephen@...workplumber.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>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	netdev@...r.kernel.org
Subject: Re: [PATCH 1/1] ipv4: arp: Always update neighbour address when a
 gratuitous arp is received

On Fri, 20 Dec 2013 10:59:22 -0800
Salam Noureddine <noureddine@...stanetworks.com> 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.
> 
> Signed-off-by: Salam Noureddine <noureddine@...stanetworks.com>

Doesn't this make the system more vulnerable to ARP spoofing?
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