before tagging them. This can help to work around brain-damage in some
switches that fail to pad a frame after untagging it if its length drops
below the minimum. This option is blessed by IEEE Std 802.1Q (2003 Ed.),
paragraph C.4.4.3.b. It's controlled by sysctl net.link.vlan.soft_pad.
Idea by: az
MFC after: 1 week