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Re: [Xen-users] DNAT TCP checksum error

Im not an expert on this either, I have just had to deal with it myself very 
recently.  A post went out on the devel list earlier
talking about theoretical reasons as to why the tcpchecksum code is disabled 
for virtual interfaces.  I have posed the question back to
the devel list asking for a clarification as to why that is done and if it 
could just be removed since it seems to impact a lot of
people (everyone that isn't bridging as far as I can tell). As for fixing it in the kernel, you can edit the file drivers/xen/netback/interface.c . look for the line dev->features = NETIF_F_NO_CSUM;

and replace it with

dev->features        = 0; /*NETIF_F_NO_CSUM; */

which as I understand it will re-enable checksums at the virtual interface 
level and worked very well for me.  If I hear something back on why this code 
is set to
disable checksums, I will post it to here.

The place where you made your stand never mattered,
only that you were there... and still on your feet

On Sat, 1 Apr 2006, Javier Guerra wrote:

On Saturday 01 April 2006 1:15 pm, jean-luc.voisin wrote:
the "ethtool -K eth0 tx off" corrects the problem, but how to solve the
problem within the kernel ?

i don't understand fully why this is sometimes needed.  does it makes the
driver not to write checksums? or not to rely on hardware checksumming?

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