Trying to start domU with latest xen, I'm seeing this in /var/log/xend.log:

  VmError: Device 0 (vif) could not be connected. Hotplug scripts not working.

With such a helpful error message, the problem was obvious of course :-)


Issue is that the network-bridge script has been changed around a bit, and it
was failing with:

  error: "net.bridge.bridge-nf-call-arptables" is an unknown key

The bridge module wasn't being loaded.

Seems that brctl was previously being run before this point, and the ioctl is
uses would cause the bridge module to be loaded.

Attaching a fixed version of xen-network-iptables-bridge.patch which tweaks the
kernel params after starting the bridge.