Comment 1 for bug 1761534

For qemu and upstream DPDK, support is present for the VIRTIO_NET_F_STATUS capability, and as such should not experience the "UNKNOWN" operstate issue; jvosburgh checked qemu and don't see this issue when running it, but haven't set up DPDK to verify it's behavior.

The opencontrail vrouter source code does not support VIRTIO_NET_F_STATUS, which dovetails with the prior analysis that suggests that this lack of support would lead to the operstate UNKNOWN.

jvosburgh also examined the virtio specification itself. It indicates that if VIRTIO_NET_F_STATUS is not available, the "link should be assumed active."