netdev - Re: [GIT net-next] Open vSwitch

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Message-Id: <20140803.212131.1256448650945676000.davem@davemloft.net>
Date:	Sun, 03 Aug 2014 21:21:31 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	pshelar@...ira.com
Cc:	netdev@...r.kernel.org
Subject: Re: [GIT net-next] Open vSwitch

From: Pravin Shelar <pshelar@...ira.com>
Date: Sun, 3 Aug 2014 12:20:32 -0700

> On Sat, Aug 2, 2014 at 3:16 PM, David Miller <davem@...emloft.net> wrote:
>> From: Pravin B Shelar <pshelar@...ira.com>
>> Date: Thu, 31 Jul 2014 16:57:37 -0700
>>
>>> Following patch adds mask cache so that we do not need to iterate over
>>> all entries in mask list on every packet. We have seen good performance
>>> improvement with this patch.
>>
>> How much have you thought about the DoS'ability of openvswitch's
>> datastructures?
>>
> This cache is populated by flow lookup in fast path. The mask cache is
> fixed in size. Userspace or number of packets can not change its size.
> Memory is statically allocated, no garbage collection. So DoS attack
> can not exploit this cache to increase ovs memory footprint.

An attacker can construct a packet sequence such that every mask cache
lookup misses, making the cache effectively useless.
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