netdev - Re: [RFC PATCH net-next 0/3] TC: Introduce qevents

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Message-ID: <871rn5uyzd.fsf@mellanox.com>
Date:   Wed, 27 May 2020 18:25:10 +0200
From:   Petr Machata <petrm@...lanox.com>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     netdev <netdev@...r.kernel.org>, Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Jiri Pirko <jiri@...lanox.com>,
        Ido Schimmel <idosch@...lanox.com>
Subject: Re: [RFC PATCH net-next 0/3] TC: Introduce qevents

Vladimir Oltean <olteanv@...il.com> writes:

> I only took a cursory glance at your patches. Can these "qevents" be
> added to code outside of the packet scheduler, like to the bridge, for
> example? Or can the bridge mark the packets somehow, and then any
> generic qdisc be able to recognize this mark without specific code?
> A very common use case which is currently not possible to implement is
> to rate-limit flooded (broadcast, unknown unicast, unknown multicast)
> traffic. Can your "qevents" be used to describe this, or must it be
> described separately?

You mean something like a "flood" qevent? In principle nothing prevents
this, but it does not strike me as a very good fit. These events are
meant to be used on qdiscs, hence the "q" in the name. I am not sure it
makes sense to reuse them for bridge traffic policing.

Peeking in 802.1Q, I see "Managed objects for per-stream filtering and
policing". If that's related, it seems like it would be conservative to
model the policing directly in the bridge, instead of this round-about
through TC.