netdev - Re: Bad TCP timestamps on non-PC platforms

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Date:	Mon, 10 Jan 2011 08:07:56 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Alex Dubov <oakad@...oo.com>
Cc:	Stephen Hemminger <shemminger@...tta.com>, netdev@...r.kernel.org,
	David Miller <davem@...emloft.net>
Subject: Re: Bad TCP timestamps on non-PC platforms

Le dimanche 09 janvier 2011 à 22:33 -0800, Alex Dubov a écrit :
> > > Any ideas where this particular problem may
> > originate?
> > 
> > Is there a bug in checksum offload in the driver?
> > Does the hardware correctly handle checksum of packets that
> > are
> > unaligned or whose length is an odd number of bytes?
> > 
> > If the hardware can't do checksum correctly, the driver
> > should either
> > disable checksum offload or in worst case copy the packet
> > to a new
> > buffer that is in a known safe place.
> 
> I managed to work around the issue by clearing the NETIF_F_IP_CSUM
> feature flag of the gianfar network driver, so it appears the bug is
> indeed somewhere there.
> 

Its incredible how TCP timestamps can be "usual suspects" ;)



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