netdev - Re: [PATCH v2 net-next 0/2] Allow unknown unicast traffic to CPU for Felix DSA

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Date:   Tue, 25 Feb 2020 15:08:40 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     "Allan W. Nielsen" <allan.nielsen@...rochip.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Horatiu Vultur <horatiu.vultur@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Joergen Andreasen <joergen.andreasen@...rochip.com>,
        Alexandru Marginean <alexandru.marginean@....com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Xiaoliang Yang <xiaoliang.yang_1@....com>,
        "Y.b. Lu" <yangbo.lu@....com>, netdev <netdev@...r.kernel.org>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>
Subject: Re: [PATCH v2 net-next 0/2] Allow unknown unicast traffic to CPU for
 Felix DSA

Hi Allan,

On Tue, 25 Feb 2020 at 15:02, Allan W. Nielsen
<allan.nielsen@...rochip.com> wrote:
>
> On 24.02.2020 23:34, Vladimir Oltean wrote:
> >From: Vladimir Oltean <vladimir.oltean@....com>
> >
> >This is the continuation of the previous "[PATCH net-next] net: mscc:
> >ocelot: Workaround to allow traffic to CPU in standalone mode":
> >
> >https://www.spinics.net/lists/netdev/msg631067.html
> >
> >Following the feedback received from Allan Nielsen, the Ocelot and Felix
> >drivers were made to use the CPU port module in the same way (patch 1),
> >and Felix was made to additionally allow unknown unicast frames towards
> >the CPU port module (patch 2).
> >
> >Vladimir Oltean (2):
> >  net: mscc: ocelot: eliminate confusion between CPU and NPI port
> >  net: dsa: felix: Allow unknown unicast traffic towards the CPU port
> >    module
> >
> > drivers/net/dsa/ocelot/felix.c           | 16 ++++--
> > drivers/net/ethernet/mscc/ocelot.c       | 62 +++++++++++++---------
> > drivers/net/ethernet/mscc/ocelot.h       | 10 ----
> > drivers/net/ethernet/mscc/ocelot_board.c |  5 +-
> > include/soc/mscc/ocelot.h                | 67 ++++++++++++++++++++++--
> > net/dsa/tag_ocelot.c                     |  3 +-
> > 6 files changed, 117 insertions(+), 46 deletions(-)
>
> Hi Vladimer,
>
> Did this fix you original issue with the spamming of the CPU?
>
> /Allan

No, the entire handling of unknown unicast packets still leaves a lot
to be desired, but at least now the CPU gets those frames, which is
better than it not getting them.
For one thing, an unknown unicast packet received by a standalone
Felix port will still consume CPU cycles dropping it, whereas the same
thing cannot be said for a different DSA switch setup, say a sja1105
switch inheriting the MAC address from the DSA master, because the DSA
master drops that.
Secondly, even traffic that the CPU _intends_ to terminate remains
"unknown" from the switch's perspective, due to the
no-learning-from-injected-traffic issue. So that traffic is still
going to be flooded, potentially to unwanted ports as well.

Regards,
-Vladimir