[Click] Problem sending VLAN tagged packets

[Jens Mueller]

Hi,

> OK, I'm trying to add a VLAN tag on all packets.  Of course, for MTU
> packets, this adds 4 bytes.
> 
> So I'm getting a bunch of 
> ToDevice(eth5) send: Message too long
> errors from these now "overlength" packets.
> However, these are NOT overlength, as MTU for ethernet is +4 bytes for
> VLAN tagged packets.  Suggestions?

I can confirm this behaviour. My device's MTU is 1500:

1514 | 02020202 02020002 b3327519 08001111 11111111 11111111
1518 | 02020202 02020002 b3327519 81000000 08001111 11111111
ToDevice(eth1) send: Message too long

I suppose my tagged packet above is correct according to 802.1Q and
rejected by the kernel. Can you point me to the spec, where it says that
MTU is increased by 4 for VLAN packets? I haved looked at the 802.1Q spec
(http://standards.ieee.org/getieee802/download/802.1Q-2003.pdf), but
could not find it myself.

Kind regards,
Jens