On Wed, Sep 1, 2021 at 10:46 AM Martin KaFai Lau [off-list ref] wrote:

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Another idea. Rather than work with qdisc objects which creates all
these issues with how to work with existing interfaces, filters, etc.
Why not create an sk_buff map? Then this can be used from the existing
egress/ingress hooks independent of the actual qdisc being used.

I agree. In fact, I'm working on doing just this for XDP, and I see no
reason why the map type couldn't be reused for skbs as well. Doing it
this way has a couple of benefits:

- It leaves more flexibility to BPF: want a simple FIFO queue? just
  implement that with a single queue map. Or do you want to build a full
  hierarchical queueing structure? Just instantiate as many queue maps
  as you need to achieve this. Etc.

Agree.  Regardless how the interface may look like,
I even think being able to queue/dequeue an skb into different bpf maps
should be the first thing to do here.  Looking forward to your patches.

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- The behaviour is defined entirely by BPF program behaviour, and does
  not require setting up a qdisc hierarchy in addition to writing BPF
  code.

Interesting idea.  If it does not need to use the qdisc object/interface
and be able to do the qdisc hierarchy setup in a programmable way, it may
be nice.  It will be useful for the future patches to come with some
bpf prog examples to do that.

Wow. When core developers think along the same lines and
build/refine the idea together it's simply awesome.