netdev - Re: [PATCH] net: Check skb->rxhash in gro

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Message-ID: <1389753816.3720.184.camel@deadeye.wl.decadent.org.uk>
Date:	Wed, 15 Jan 2014 02:43:36 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>, therbert@...gle.com,
	netdev@...r.kernel.org
Subject: Re: [PATCH] net: Check skb->rxhash in gro_receive

On Tue, 2014-01-14 at 18:27 -0800, Eric Dumazet wrote:
> On Wed, 2014-01-15 at 01:31 +0000, Ben Hutchings wrote:
> 
> > When I investigated the scope of this for Debian, I tried sending a
> > 'packet of death' to a VM and actually triggered the lockup in the TX
> > path of the *host*, running Debian unstable with Linux 3.11.  I didn't
> > track down exactly why that was but I think that libvirt's default
> > networking configuration includes multiqueue devices that use flow
> > dissector.
> 
> OK, I take that majority of debian hosts are running some VM then,
> nice to know, time to update my hosts and usages I guess.

I said that common configurations use flow dissector - not the majority.

> Anyway, current flow dissector needs care if we really use it in
> unprotected areas.
> 
> Hostile packets can force flow dissection of MTU bytes,
> bringing host to abysmal performance.
[...]

Yes.  I think the number of times it can loop should be limited to some
small number.

Ben.

-- 
Ben Hutchings
Life is what happens to you while you're busy making other plans.
                                                               - John Lennon

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