From: Petr Machata <redacted>
Date: Sat, 27 Jun 2020 01:45:24 +0300

The Spectrum hardware allows execution of one of several actions as a
result of queue management decisions: tail-dropping, early-dropping,
marking a packet, or passing a configured latency threshold or buffer
size. Such packets can be mirrored, trapped, or sampled.

Modeling the action to be taken as simply a TC action is very attractive,
but it is not obvious where to put these actions. At least with ECN marking
one could imagine a tree of qdiscs and classifiers that effectively
accomplishes this task, albeit in an impractically complex manner. But
there is just no way to match on dropped-ness of a packet, let alone
dropped-ness due to a particular reason.

To allow configuring user-defined actions as a result of inner workings of
a qdisc, this patch set introduces a concept of qevents. Those are attach
points for TC blocks, where filters can be put that are executed as the
packet hits well-defined points in the qdisc algorithms. The attached
blocks can be shared, in a manner similar to clsact ingress and egress
blocks, arbitrary classifiers with arbitrary actions can be put on them,
etc.

 ...

Series applied, thank you.