Re: [PATCH net-next] bridge: Make the FDB consider inner tag for Q-in-Q

[Vladimir Oltean]

On Wed, Dec 04, 2024 at 12:37:24AM -0800, Andrew Strohman wrote:
> > What stops you from changing the 802.1ad bridge port pvids to unique
> > values, like 3, 4, 5... instead of 3, 3, 3, and making each other
> > j != i bridge port be a non-pvid member of port i's pvid?
> 
> I'm not sure if I understand this suggestion.
> 
> I tried to draw out what you described here:
> https://docs.google.com/drawings/d/1UcOpENFgr-s6p8Ypwo-l4yTvtUZFM6vSLxLiX2FOMLU
> 
> I'm not sure how host A can communicate with B with this configuration.
> 
> Consider host A transmitting towards host B. When the frame leaves
> ".1q bridge 3",
> it will be tagged with .1q tag vid 7. When the frame leaves the .1ad bridge
> heading toward ".1q bridge 2", it will be tagged again with an outer
> .1ad tag vid 3.
> 
> So ".1q bridge 2" will see the frame as having an outer tag of .1ad vid 3 and
> inner tag of .1q vid 7.
> 
> Is that what you are thinking, or something else?

I didn't say "tagged". I just said "not PVID". There are 2 independent
bridge VLAN attributes: "pvid" and [egress-]"untagged". I am suggesting
that packets in VID 3, 4, 5 all exit the 802.1ad bridge untagged, but
every bridge port has a unique PVID from this range.

bridge vlan add dev port1 vid 3 pvid untagged
bridge vlan add dev port1 vid 4 untagged
bridge vlan add dev port1 vid 5 untagged

bridge vlan add dev port1 vid 3 untagged
bridge vlan add dev port1 vid 4 pvid untagged
bridge vlan add dev port1 vid 5 untagged

bridge vlan add dev port1 vid 3 untagged
bridge vlan add dev port1 vid 4 untagged
bridge vlan add dev port1 vid 5 pvid untagged