TAP device deletes VLAN tag? (netgraph related)

From: Peter <pmc_at_citylink.dinoex.sub.org>
Date: Sat, 31 Jul 2021 23:51:58 UTC
Sending here since "stable" still doesn't work...

Hi all,                                                                         
  I found a problem when connecting tap devices.                                
In the most straightforward way I would do                                      
# ngctl connect tap1: fxp0: lower lower                                         
Then doing tcpdump on both netifs, the originating (in my case tap0)            
has the VLAN tag, and the receiving doesn't show it anymore.                    
The same happens when attaching a tap device to a ng_bridge or ng_hub:          
the tap device (and the bhyve behind it) will not see the VLAN tags             
arriving from elsewhere on the bridge.                                          
The tap device itself seems to support vlan tags. So the problem                
appears to be most likely related to the netgraph hook of the tap               
device (the lower, in my case).                                                 
This is Rel. 12.2 running. Is this a known problem? Is there a patch            
or workaround known?