I was having serious network issues using GRE and I have been tracking it for a
few weeks. Finally, I solved the issue but it needs a proper fix. To summarize,
I need a way to set MTU settings of br-int and br-tun interfaces, enable MQ
support in libvirt, and run "ethtool -L eth0 combined N" command in VMs.
The detailed bug report and the explanation for the issue is here:
There is a blueprint  on MQ support but it wasn't accepted.
What can we do about this performance problem and a possible fix? Most people
complain about GRE/VXLAN performance and the solution appears to be working. I
created a bug report and let the list know to work on a better, flexible, and
working solution. Please ignore the ugly patches as they are just proof of concept.
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