RE: [Xen-users] Re: Dom0 to DomU and reverse works but Outside world toDomU only ping works

["James Harper" <james.harper@xxxxxxxxxxxxxxxx>]

> 
> For others who might get stuck in the similar situation, the solution
> was to stop tx checsum in the DomU
> 
> $ethtool -K eth0 tx off
> 
> I am wondering why do I need to do this ?
> 

This is a common problem, and appears to be related to bugs in one or
more of:
. Xen frontend network driver (unlikely)
. Xen backend network driver
. Linux bridge code
. Linux routing code
. Linux physical NIC adapter

I suspect it is the last one, but it's complicated enough that the bug
could lie elsewhere but only show up on certain NIC's.

You can be thankful that your problem was consistent. I have a setup
where the packets from DomU are routed in Dom0 to one of 6 GRE tunnels,
and occasionally for 30 minutes or so TCP packets stopped working. Took
me ages to figure out that turning off tx checksum offload in the DomU
would resolve the problem. It was made harder because by the time I
could connect to the client to investigate, it had started working again
so all I could do was to set up tcpdumps of some fairly high volume
links and wade through those based on the times that the problem was
occurring...

James

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