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

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Date:   Fri, 19 Aug 2022 11:51:11 +0200
From:   netdev@...io-technology.com
To:     Ido Schimmel <idosch@...dia.com>
Cc:     Vladimir Oltean <olteanv@...il.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 2022-08-14 16:55, Ido Schimmel wrote:
> On Fri, Aug 12, 2022 at 02:29:48PM +0200, netdev@...io-technology.com 
> wrote:
>> On 2022-08-11 13:28, Ido Schimmel wrote:
>> 
>> > > > I'm talking about roaming, not forwarding. Let's say you have a locked
>> > > > entry with MAC X pointing to port Y. Now you get a packet with SMAC X
>> > > > from port Z which is unlocked. Will the FDB entry roam to port Z? I
>> > > > think it should, but at least in current implementation it seems that
>> > > > the "locked" flag will not be reset and having locked entries pointing
>> > > > to an unlocked port looks like a bug.

I have made the locked entries sticky in the bridge, so that they don't 
move to other ports.

>> > > >
>> > >
>> 
>> In general I have been thinking that the said setup is a network
>> configuration error as I was arguing in an earlier conversation with
>> Vladimir. In this setup we must remember that SMAC X becomes DMAC X in 
>> the
>> return traffic on the open port. But the question arises to me why MAC 
>> X
>> would be behind the locked port without getting authed while being 
>> behind an
>> open port too?
>> In a real life setup, I don't think you would want random hosts behind 
>> a
>> locked port in the MAB case, but only the hosts you will let through. 
>> Other
>> hosts should be regarded as intruders.
>> 
>> If we are talking about a station move, then the locked entry will age 
>> out
>> and MAC X will function normally on the open port after the timeout, 
>> which
>> was a case that was taken up in earlier discussions.
>> 
>> But I will anyhow do some testing with this 'edge case' (of being 
>> behind
>> both a locked and an unlocked port) if I may call it so, and see to 
>> that the
>> offloaded and non-offloaded cases correspond to each other, and will 
>> work
>> satisfactory.
> 
> It would be best to implement these as additional test cases in the
> current selftest. Then you can easily test with both veth pairs and
> loopbacks and see that the hardware and software data paths behave the
> same.
> 

How many loops would be needed to have a selftest with a HUB and a MAC 
on both a locked and an unlocked port?

>> 
>> I think it will be good to have a flag to enable the mac-auth/MAB 
>> feature,
>> and I suggest just calling the flag 'mab', as it is short.

I have now created the flag to enable Mac-Auth/MAB with iproute2:
bridge link set dev DEV macauth on|off

with the example output from 'bridge -d link show dev DEV' when macauth 
is enabled:
1: ethX: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master br0 state 
forwarding priority 32 cost 19
     hairpin off guard off root_block off fastleave off learning on flood 
off mcast_flood on bcast_flood on mcast_router 1 mcast_to_unicast off 
neigh_suppress off vlan_tunnel off isolated off locked mab on

The flag itself in the code is called BR_PORT_MACAUTH.

> 
> Fine by me, but I'm not sure everyone agrees.