[RFC net-next] llc: jumbo frame support

Hi all,


this is a somewhat random stab at 802.1AC / jumbo frame support for LLC.
It kinda fell out as a side effect from poking at FRRouting's IS-IS
socket use.  Unfortunately even if this gets picked up right now, it'll
be quite a bit of time before we can even consider using it there.  (And
it's not clear that it'll go that way.)

Regardless, it's a tiny change & my messing around with things
effectively got me the selftest too.

The fact that AF_LLC can't be used in a network namespace is a bit of a
problem though (haven't looked at how much work that would be, unlike
the jumbo frame support this didn't fall out "for free"), and so is the
fact that AF_LLC is on limited maintenance...

It's an RFC.  Comments appreciated.

Cheers,


equi (David)

(waves from netdevconf in Rome)