linux-kernel - Re: [PATCH v4 net-next 3/6] drivers: net: dsa: add locked fdb entry flag to drivers

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Date:   Sun, 17 Jul 2022 15:09:10 +0200
From:   netdev@...io-technology.com
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Ido Schimmel <idosch@...dia.com>, 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>,
        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>,
        linux-kernel@...r.kernel.org, bridge@...ts.linux-foundation.org,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v4 net-next 3/6] drivers: net: dsa: add locked fdb entry
 flag to drivers

On 2022-07-17 14:57, Vladimir Oltean wrote:
> On Sun, Jul 17, 2022 at 02:21:47PM +0200, netdev@...io-technology.com 
> wrote:
>> On 2022-07-13 14:39, Ido Schimmel wrote:
>> > On Wed, Jul 13, 2022 at 09:09:58AM +0200, netdev@...io-technology.com
>> > wrote:
>> 
>> >
>> > What are "Storm Prevention" and "zero-DPV" FDB entries?
>> 
>> They are both FDB entries that at the HW level drops all packets 
>> having a
>> specific SA, thus using minimum resources.
>> (thus the name "Storm Prevention" aka, protection against DOS attacks. 
>> We
>> must remember that we operate with CPU based learning.)
> 
> DPV means Destination Port Vector, and an ATU entry with a DPV of 0
> essentially means a FDB entry pointing nowhere, so it will drop the
> packet. That's a slight problem with Hans' implementation, the bridge
> thinks that the locked FDB entry belongs to port X, but in reality it
> matches on all bridged ports (since it matches by FID). FID allocation
> in mv88e6xxx is slightly strange, all VLAN-unaware bridge ports,
> belonging to any bridge, share the same FID, so the FDB databases are
> not exactly isolated from each other.

But if the locked port is vlan aware and has a pvid, it should not block 
other ports. Besides the fid will be zero with vlan unaware afaik, and 
all with zero fid do not create locked entries.