linux-kernel - Re: [PATCH v2 net-next 2/4] net: switchdev: add support for offloading of fdb locked flag

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Date:   Fri, 25 Mar 2022 10:24:17 +0100
From:   Hans Schultz <schultz.hans@...il.com>
To:     Vladimir Oltean <olteanv@...il.com>,
        Hans Schultz <schultz.hans@...il.com>
Cc:     davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.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 v2 net-next 2/4] net: switchdev: add support for
 offloading of fdb locked flag

On tor, mar 24, 2022 at 16:27, Vladimir Oltean <olteanv@...il.com> wrote:
> On Thu, Mar 24, 2022 at 12:23:39PM +0100, Hans Schultz wrote:
>> On tor, mar 24, 2022 at 13:09, Vladimir Oltean <olteanv@...il.com> wrote:
>> > On Thu, Mar 24, 2022 at 11:32:08AM +0100, Hans Schultz wrote:
>> >> On ons, mar 23, 2022 at 16:43, Vladimir Oltean <olteanv@...il.com> wrote:
>> >> > On Wed, Mar 23, 2022 at 01:49:32PM +0100, Hans Schultz wrote:
>> >> >> >> Does someone have an idea why there at this point is no option to add a
>> >> >> >> dynamic fdb entry?
>> >> >> >> 
>> >> >> >> The fdb added entries here do not age out, while the ATU entries do
>> >> >> >> (after 5 min), resulting in unsynced ATU vs fdb.
>> >> >> >
>> >> >> > I think the expectation is to use br_fdb_external_learn_del() if the
>> >> >> > externally learned entry expires. The bridge should not age by itself
>> >> >> > FDB entries learned externally.
>> >> >> >
>> >> >> 
>> >> >> It seems to me that something is missing then?
>> >> >> My tests using trafgen that I gave a report on to Lunn generated massive
>> >> >> amounts of fdb entries, but after a while the ATU was clean and the fdb
>> >> >> was still full of random entries...
>> >> >
>> >> > I'm no longer sure where you are, sorry..
>> >> > I think we discussed that you need to enable ATU age interrupts in order
>> >> > to keep the ATU in sync with the bridge FDB? Which means either to
>> >> > delete the locked FDB entries from the bridge when they age out in the
>> >> > ATU, or to keep refreshing locked ATU entries.
>> >> > So it seems that you're doing neither of those 2 things if you end up
>> >> > with bridge FDB entries which are no longer in the ATU.
>> >> 
>> >> Any idea why G2 offset 5 ATUAgeIntEn (bit 10) is set? There is no define
>> >> for it, so I assume it is something default?
>> >
>> > No idea, but I can confirm that the out-of-reset value I see for
>> > MV88E6XXX_G2_SWITCH_MGMT on 6190 and 6390 is 0x400. It's best not to
>> > rely on any reset defaults though.
>> 
>> I see no age out interrupts, even though the ports Age Out Int is on
>> (PAV bit 14) on the locked port, and the ATU entries do age out (HoldAt1
>> is off). Any idea why that can be?
>> 
>> I combination with this I think it would be nice to have an ability to
>> set the AgeOut time even though it is not per port but global.
>
> Sorry, I just don't know. Looking at the documentation for IntOnAgeOut,
> I see it says that for an ATU entry to trigger an age out interrupt, the
> port it's associated with must have IntOnAgeOut set.
> But your locked ATU entries aren't associated with any port, they have
> DPV=0, right? So will they never trigger any age out interrupt according
> to this? I'm not clear.

If it could be possible to add a dynamic entry to the bridge module from
the driver, that would be a solution, and since in the ATU in this case
ages out entries learned, I don't see why __br_fdb_add() insists that an
external learned entry must be permanent?