[lwip-devel] [task #9033] Support IEEE 802.1q tagged frame (VLAN)

[Simon Goldschmidt]

Follow-up Comment #3, task #9033 (project lwip):

> I'm not so sure: is it right to accept packets for a VLAN that 
> you have not been configured to be part of? If it is, that's 
> fine, I'm just not sure what the correct behaviour is.

As far as I know (and have been using it), there are three possibilities:

a) your device gets all traffic
b) your device only gets traffic for the VLAN it is configured for
b1) including VLAN header
b2) VLAN header is stripped of by the switch

In case a), it is of course not correct to accept packets for the wrong VLAN.
However in case b1), it is. Case b2) already works since it is no difference
from a normal LAN. Maybe we should add a check for a configured VLAN?

> The other problem I can see is that we won't deal with nested 
> VLAN packets very well - it assumes that the IP hdr follows a 
> single VLAN tag.

Is that allowd? I didn't know that. I though whoever addes a VLAN header has
to replace an existing one: otherwise you can't guarantee a maximum packet
length in your network... I'll try to check what the RFC says about that.

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