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

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?
>> Thus learning is off for locked ports, which of course includes MAB.
>> 
>> So the 'learning' is based on authorizing MAC,vlan addresses,
which
>> is done by userspace daemons, e.g. hostapd or what could be called
>> mabd.

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.