netdev - Re: [PATCH V3 net-next 3/4] net: dsa: mv88e6xxx: mac-auth/MAB implementation

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Date:   Wed, 6 Jul 2022 15:48:16 +0200
From:   Hans S <schultz.hans@...il.com>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        Hans Schultz <schultz.hans+netdev@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>, Jiri Pirko <jiri@...nulli.us>,
        Ivan Vecera <ivecera@...hat.com>,
        Roopa Prabhu <roopa@...dia.com>,
        Nikolay Aleksandrov <razor@...ckwall.org>,
        Shuah Khan <shuah@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Ido Schimmel <idosch@...dia.com>, linux-kernel@...r.kernel.org,
        bridge@...ts.linux-foundation.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH V3 net-next 3/4] net: dsa: mv88e6xxx: mac-auth/MAB implementation

On Wed, Jul 6, 2022 at 3:28 PM Vladimir Oltean <olteanv@...il.com> wrote:
>
> On Tue, Jul 05, 2022 at 05:05:52PM +0200, Hans S wrote:
> > Hi, does anybody know what it going on with this variable?
> > struct dsa_port *dp ->ageing_time;
> >
> > I experience that it changes value like a factor ~10 at times.
>
> Could you be a bit more specific? Are you talking about STP Topology
> Change Notification BPDUs, which trigger this code path?
>
> diff --git a/net/bridge/br_stp.c b/net/bridge/br_stp.c
> index 7d27b2e6038f..9b25bc2dcb3e 100644
> --- a/net/bridge/br_stp.c
> +++ b/net/bridge/br_stp.c
> @@ -671,10 +671,10 @@ void __br_set_topology_change(struct net_bridge *br, unsigned char val)
>
>                 if (val) {
>                         t = 2 * br->forward_delay;
> -                       br_debug(br, "decreasing ageing time to %lu\n", t);
> +                       br_info(br, "decreasing ageing time to %lu\n", t);
>                 } else {
>                         t = br->bridge_ageing_time;
> -                       br_debug(br, "restoring ageing time to %lu\n", t);
> +                       br_info(br, "restoring ageing time to %lu\n", t);
>                 }
>
>                 err = __set_ageing_time(br->dev, t);
>
> Coincidentally the default values of 2 * br->forward_delay and br->bridge_ageing_time
> are 1 order of magnitude apart from each other.
>
> [  139.998310] br0: topology change detected, propagating
> [  140.003490] br0: decreasing ageing time to 3000
> [  175.193054] br0: restoring ageing time to 30000
>
> What's the problem anyway?

It might be a topology change as you indicate, though I am not sure.
So I am not using that variable any more for determining the ageing
time for the locked FDB entries, but instead I have made a function to
read the time from the chip instead.

The problem with that, I have mentioned in my latest reply to the
mac-auth patch set...