[B.A.T.M.A.N.] Add VLAN tag size to MTU recommendation?

["Linus Lüssing" <linus.luessing@c0d3.blue>]

Hi,

First of all, just wanted to forward this awesome diagram
regarding MTUs in Gluon-Setups which Freifunk Hamburg created
:D :

https://twitter.com/ohrensesselnet/status/789176399655350272

Which might be helpful for anyone new to understand how the
encapsulation in batman-adv works and how the MTU recommendations
of the underlying hard interfaces are calculated.

(I need to ask Leo for the sources, maybe a version without the
fastd overhead might be interesting for an MTU-explained page in
the open-mesh.org wiki :)?)


While checking the calculations Freifunk Hamburg did, I was
wondering whether the batadv_hardif_min_mtu() function should add
an extra 4 bytes for VLAN tagged, encapsulated payload to the MTU
calculations and the kmesg recommendations, especially since
Antonio's great work made TT fully VLAN-aware?

Open-Mesh.com/Cloudtrax routers are using the VLAN awareness, right?
Is the wifi interface MTU there just set to +4 bytes over the kmesg
recommedation?

Regards, Linus