Linux Ethernet Bridging - Aug 2022 - [Bridge] [PATCH v4 net-next 3/6] drivers: net: dsa: add locked fdb entry flag to drivers

On Fri, Aug 12, 2022 at 02:29:48PM +0200, netdev at kapio-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.
> > > >
> > > 
> 
> 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.
> 
> 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.
Fine by me, but I'm not sure everyone agrees.
> 
> Otherwise I don't see any major issues with the whole feature as it is.
Will review and test the next version.

Thanks

On 2022-08-14 16:55, Ido Schimmel wrote:
> On Fri, Aug 12, 2022 at 02:29:48PM +0200, netdev at kapio-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.