Tested with GENERIC (thus DEBUG enabled), with a bhyve VM connected to a tap0 device configured with an IP address.
The tap0 device has not been bridged to a bridge(4) device.
Netperf tests between the vtnet0 interface in the VM and the tap0 shows 9-10 Gbps in both directions.
Without TSO/LRO support, the same tests show ~3Gbps.
In order to test this patch, the related patches an additional follow-up patch is needed for bhyve to configure the virtio-net header in the if_tap(4) backend.