Re: [RFC PATCH] doc: clarify VLAN and QinQ stripping behaviour

[Patrick Robb <probb@iol.unh.edu>]

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On Tue, Jul 15, 2025 at 3:47 AM Bruce Richardson <bruce.richardson@intel.com>
wrote:

>
>
> Thanks. Let me know how the testing otherwise goes. If only Intel NICs are
> supporting QinQ, then it can't be that widely used a feature yet, so we may
> be able to tweak things a bit if it diverges from what is expected.
>

Yeah, there seems to be fairly broad support for VLAN strip, but much less
for QinQ strip. So, we can verify "correct" VLAN stripping behavior given
the various packet profiles we discussed previously like double vlan,
vlan + qinq, single qinq etc.

For QinQ strip like Dean said, most PMDs dont support this currently, with
Intel PMDs being an exception among the NICs we have at UNH. We took a look
at the DPDK networking drivers support table which reflects this (see the
QinQ offload row). https://doc.dpdk.org/guides/nics/overview.html

So, it looks like there are a few (ZTE DXDH is an example) that are also
supporting QinQ Offload, but not many right now.



> I also wonder if the definition of expected behaviour is preventing other
> NICs from implementing the feature?
>
> Can you also check with VLAN stripping enabled? My biggest issue with the
> behaviour description of QinQ strip only removing outer tag is that it
> implies for QinQ traffoc that VLAN strip alone should strip inner tag
> without
> removing outer.


Sure, we can check this case. across the NICs at UNH. I have a sync
wth Dean tomorrow morning for this, at the end of which we'll share back to
you what we have.


> That doesn't make sense to me - and I'm not sure if NIC
> hardware supports such features of removing inner headers while leaving
> outer.
>
> /Bruce
>

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