netdev - Re: [PATCH net-next 04/20] net: Add ndo_{peer,unpeer}

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Message-ID: <3715920a-a8b6-4025-9f8f-ba847a5eb7f5@iogearbox.net>
Date: Tue, 23 Sep 2025 18:26:15 +0200
From: Daniel Borkmann <daniel@...earbox.net>
To: David Wei <dw@...idwei.uk>, Jakub Kicinski <kuba@...nel.org>
Cc: netdev@...r.kernel.org, bpf@...r.kernel.org, davem@...emloft.net,
 razor@...ckwall.org, pabeni@...hat.com, willemb@...gle.com, sdf@...ichev.me,
 john.fastabend@...il.com, martin.lau@...nel.org, jordan@...fe.io,
 maciej.fijalkowski@...el.com, magnus.karlsson@...el.com
Subject: Re: [PATCH net-next 04/20] net: Add ndo_{peer,unpeer}_queues callback

On 9/23/25 6:06 PM, David Wei wrote:
> On 2025-09-22 18:23, Jakub Kicinski wrote:
>> On Fri, 19 Sep 2025 23:31:37 +0200 Daniel Borkmann wrote:
>>> Add ndo_{peer,unpeer}_queues() callback which can be used by virtual drivers
>>> that implement rxq mapping to a real rxq to update their internal state or
>>> exposed capability flags from the set of rxq mappings.
>>
>> Why is this something that virtual drivers implement?
>> I'd think that queue forwarding can be almost entirely implemented
>> in the core.
> 
> I believe Daniel needs it for AF_XDP.

Yes, in case of af_xdp we basically need to propagate related capabilities
of the netdev, so that we can expose the given xdp flags in this case
further to netkit which implements ndo_bpf etc. Thinking about it, maybe
an alternative could be that netkit always exposes NETDEV_XDP_ACT_XSK etc
and we catch it in netkit's ndo_bpf + ndo_xsk_wakeup implementation when
checking peer queue's dev, and let it fail there instead. I'll play a bit
with this idea instead, perhaps this simplifies things.