[Xen-users] Race condition in sending gratuitous ARP for live migration ?

[Sylvain Munaut <s.munaut@xxxxxxxxxxxxxxxxxxxx>]

Hi,


So, the issue is a fairly common one: Network doesn't work for like a
minute or so after a live migration.
The setup is a debian wheezy dom0 with xen 4.1.2 running 3.6.11
kernel. The domU is a Ubuntu 12.04 with a 3.2 kernel. The networking
setup uses bridges on the dom0. I also made sure that the bridge
forwarding delay is set to 0.

The VM doesn't initiate any network activity on its own, so it's
solely relying on the gratuitous ARP to be sent for the various place
(switch and dom0 bridges) to be updated.

I confirmed that the gratuitous ARP is sent by the domU after
migration by using tcpdump. I can also see it on the vif on the dom0.
But I can't see it on the bridge interface in the dom0, nor on the
network itself. I also confirmed that it I make the domU send
gratuitous ARP continuously using arping, the it works fine.

So I think the gratuitous ARP is sent a bit too early, before it's
ready to be forwarded around with the dom0.

Any idea how I can check and correct this ?


Cheers,

     Sylvain

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