Linux Ethernet Bridging - Oct 2022 - [Bridge] [PATCH v8 net-next 10/12] net: dsa: mv88e6xxx: mac-auth/MAB implementation

On Fri, Oct 21, 2022 at 08:47:42AM +0200, netdev at kapio-technology.com
wrote:
> On 2022-10-21 00:57, Vladimir Oltean wrote:
> > On Thu, Oct 20, 2022 at 10:20:50PM +0200, netdev at
kapio-technology.com
> > wrote:
> > > In general locked ports block traffic from a host based on if
there
> > > is a
> > > FDB entry or not. In the non-offloaded case, there is only CPU
> > > assisted
> > > learning, so the normal learning mechanism has to be disabled as
any
> > > learned entry will open the port for the learned MAC,vlan.
> > 
> > Does it have to be that way? Why can't BR_LEARNING on a
BR_PORT_LOCKED
> > cause the learned FDB entries to have BR_FDB_LOCKED, and everything
> > would be ok in that case (the port will not be opened for the learned
> > MAC/VLAN)?
> 
> I suppose you are right that basing it solely on BR_FDB_LOCKED is possible.
> 
> The question is then maybe if the common case where you don't need
learned
> entries for the scheme to work, e.g. with EAPOL link local packets,
requires
> less CPU load to work and is cleaner than if using BR_FDB_LOCKED entries?
I suppose the real question is what does the bridge currently do with
BR_LEARNING + BR_PORT_LOCKED, and if that is sane and useful in any case?
It isn't a configuration that's rejected, for sure. The configuration
could be rejected via a bug fix patch, then in net-next it could be made
to learn these addresses with the BR_FDB_LOCKED flag.

To your question regarding the common case (no MAB): that can be supported
just fine when BR_LEARNING is off and BR_PORT_LOCKED is on, no?
No BR_FDB_LOCKED entries will be learned.

On 2022-10-21 13:22, Vladimir Oltean wrote:
> On Fri, Oct 21, 2022 at 08:47:42AM +0200, netdev at kapio-technology.com 
> wrote:
>> On 2022-10-21 00:57, Vladimir Oltean wrote:
>> > On Thu, Oct 20, 2022 at 10:20:50PM +0200, netdev at
kapio-technology.com
>> > wrote:
>> > > In general locked ports block traffic from a host based on if
there
>> > > is a
>> > > FDB entry or not. In the non-offloaded case, there is only
CPU
>> > > assisted
>> > > learning, so the normal learning mechanism has to be disabled
as any
>> > > learned entry will open the port for the learned MAC,vlan.
>> >
>> > Does it have to be that way? Why can't BR_LEARNING on a
BR_PORT_LOCKED
>> > cause the learned FDB entries to have BR_FDB_LOCKED, and
everything
>> > would be ok in that case (the port will not be opened for the
learned
>> > MAC/VLAN)?
>> 
>> I suppose you are right that basing it solely on BR_FDB_LOCKED is 
>> possible.
>> 
>> The question is then maybe if the common case where you don't need 
>> learned
>> entries for the scheme to work, e.g. with EAPOL link local packets, 
>> requires
>> less CPU load to work and is cleaner than if using BR_FDB_LOCKED 
>> entries?
> 
> I suppose the real question is what does the bridge currently do with
> BR_LEARNING + BR_PORT_LOCKED, and if that is sane and useful in any 
> case?
> It isn't a configuration that's rejected, for sure. The
configuration
> could be rejected via a bug fix patch, then in net-next it could be 
> made
> to learn these addresses with the BR_FDB_LOCKED flag.
> 
> To your question regarding the common case (no MAB): that can be 
> supported
> just fine when BR_LEARNING is off and BR_PORT_LOCKED is on, no?
> No BR_FDB_LOCKED entries will be learned.
As it is now in the bridge, the locked port part is handled before 
learning
in the ingress data path, so with BR_LEARNING and BR_PORT_LOCKED, I 
think it
will work as it does now except link local packages.

If your suggestion of BR_LEARNING causing BR_FDB_LOCKED on a locked 
port, I
guess it would be implemented under br_fdb_update() and BR_LEARNING +
BR_PORT_LOCKED would go together, forcing BR_LEARNING in this case, thus 
also
for all drivers?