max_linkhdr defaults to 16, too short ?

[Luigi Rizzo]

just noticed that sys/kern/uipc_domain.c still sets max_linkhdr=16
as a default.
The value is often used to reserve head space in mbufs for
the MAC header. As such, 16 is too short for systems that make
use of vlans, and the effect might be that we would need
additional mbuf entries or at least move stuff down
as the vlan tag is added.

Any objection to bumping the default to 20 ?

cheers
luigi