linux-kernel - Re: [PATCH v5 net-next 6/6] selftests: forwarding: add test of MAC-Auth Bypass to locked port tests

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Date:   Wed, 07 Sep 2022 23:10:07 +0200
From:   netdev@...io-technology.com
To:     Ido Schimmel <idosch@...dia.com>
Cc:     davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Kurt Kanzenbach <kurt@...utronix.de>,
        Hauke Mehrtens <hauke@...ke-m.de>,
        Woojung Huh <woojung.huh@...rochip.com>,
        UNGLinuxDriver@...rochip.com, Sean Wang <sean.wang@...iatek.com>,
        Landen Chao <Landen.Chao@...iatek.com>,
        DENG Qingfang <dqfext@...il.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.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>,
        Christian Marangi <ansuelsmth@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Yuwei Wang <wangyuweihx@...il.com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        bridge@...ts.linux-foundation.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v5 net-next 6/6] selftests: forwarding: add test of
 MAC-Auth Bypass to locked port tests

On 2022-09-03 16:47, Ido Schimmel wrote:
> On Mon, Aug 29, 2022 at 06:13:14PM +0200, netdev@...io-technology.com 
> wrote:
>> On 2022-08-29 18:03, Ido Schimmel wrote:
>> > On Mon, Aug 29, 2022 at 05:08:23PM +0200, netdev@...io-technology.com
>> > wrote:
>> > > On 2022-08-29 16:37, Ido Schimmel wrote:
>> > > > On Mon, Aug 29, 2022 at 02:04:42PM +0200, netdev@...io-technology.com
>> > > > wrote:
>> > > > > On 2022-08-29 13:32, Ido Schimmel wrote:
>> > > > > Port association is needed for MAB to work at all on mv88e6xxx, but
>> > > > > for
>> > > > > 802.1X port association is only needed for dynamic ATU entries.
>> > > >
>> > > > Ageing of dynamic entries in the bridge requires learning to be on as
>> > > > well, but in these test cases you are only using static entries and
>> > > > there is no reason to enable learning in the bridge for that. I prefer
>> > > > not to leak this mv88e6xxx implementation detail to user space and
>> > > > instead have the driver enable port association based on whether
>> > > > "learning" or "mab" is on.
>> > > >
>> > >
>> > > Then it makes most sense to have the mv88e6xxx driver enable port
>> > > association when then port is locked, as it does now.
>> >
>> > As you wish, but like you wrote "802.1X port association is only needed
>> > for dynamic ATU entries" and in this case user space needs to enable
>> > learning (for refresh only) so you can really key off learning on
>> > "learning || mab". User space can decide to lock the port and work with
>> > static entries and then learning is not required.
>> 
>> I will of course remove all "learning on" in the selftests, which is 
>> what I
>> think you are referring to. In the previous I am referring to the code 
>> in
>> the driver itself which I understand shall turn on port association 
>> with
>> locked ports, e.g. no need for "learning on" when using the feature in
>> general outside selftests...
> 
> "learning on" is needed when dynamic FDB entries are used to authorize
> hosts. Without learning being enabled, the bridge driver (or the
> underlying hardware) will not refresh the entries during forwarding and
> they will age out, resulting in packet loss until the hosts are
> re-authorized.
> 
> Given the current test cases only use static entries, there is no need
> to enable learning on locked ports. This will change when test cases 
> are
> added with dynamic entries.
> 
> Regarding mv88e6xxx, my understanding is that you also need learning
> enabled for MAB (I assume for the violation interrupts). Therefore, for
> mv88e6xxx, learning can be enabled if learning is on or MAB is on.
> Enabling it based on whether the port is locked or not seems 
> inaccurate.

Given that 'learning on' is needed for hardware refreshing of ATU 
entries (mv88e6xxx), and that will in the future be needed in general, I 
think it is best to enable it when a port is locked. Also the matter is 
that the locked feature needs to modify the register that contains the 
PAV. So I see it as natural that it is done there, as it will eventually 
have to be done there.
That the selftests do not need it besides when activating MAB, I think, 
is a special case.

I am at the blackhole driver implementation now, as I suppose that the 
iproute2 command should work with the mv88e6xxx driver when adding 
blackhole entries (with a added selftest)?
I decided to add the blackhole feature as new ops for drivers with 
functions blackhole_fdb_add() and blackhole_fdb_del(). Do you agree with 
that approach?