nova/releasenotes/notes/vhost-user-mtu-23d0af36a8adfa56.yaml
Sean Mooney adf7ba61dd stop setting mtu when plugging vhost-user ports
vhost-user is a userspace protocol to establish connectivity
between a virto-net frontend typically qemu and a
userspace virtio backend such as ovs with dpdk.

vhost-user interfaces exist only in userspace from the host perspective
and are not represented in the linux networking stack as kernel netdevs.
As a result attempting to set the mtu on a vhost-user interface
using ifconfig or ip link will fail with a device not found error.

- this change removes a call to _set_device_mtu when plugging
  vhost-user interfaces.
- this change prevents the device not found error from occurring
  which stopped vms booting with vhost-user interfaces
  due to an uncaught exception resulting in a failure to set the
  interface type in ovs.
- this change make creating vhost-user interface
  an atomic action.

This latent bug is only triggered when the mtu value is set to a
value other than 0 which was the default proir to mitaka.

Change-Id: I2e17723d5052d57cd1557bd8a173c06ea0dcb2d4
Closes-Bug: #1533876
2016-03-18 14:56:44 +00:00

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YAML

---
fixes:
- When plugging virtual interfaces of type vhost-user the MTU value will
not be applied to the interface by nova. vhost-user ports exist only in
userspace and are not backed by kernel netdevs, for this reason it is
not possible to set the mtu on a vhost-user interface using standard
tools such as ifconfig or ip link.