xen vs bridges

[der Mouse <mouse%Rodents-Montreal.ORG@localhost>]

I can't seem to bridge a xennet interface with a vlan interface whose
parent is a different xennet interface; the second brconfig add
complains EINVAL.

This appears to be because the vlan interface's mtu is 1496.  I infer
from this that xennet is not marked ETHERCAP_VLAN_MTU.  Is this just an
oversight, or does the Xen network stuff really not support VLAN MTUs?
If the latter, what would be involved in fixing it?  It's being
problematic for me.

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