Linux Ethernet Bridging - Aug 2022 - [Bridge] [PATCH v5 net-next 6/6] selftests: forwarding: add test of MAC-Auth Bypass to locked port tests

On Sun, Aug 28, 2022 at 02:00:29PM +0200, netdev at kapio-technology.com
wrote:
> On 2022-08-27 20:21, Ido Schimmel wrote:
> > On Fri, Aug 26, 2022 at 01:45:38PM +0200, Hans Schultz wrote:
> > > +locked_port_mab()
> > > +{
> > > +	RET=0
> > > +	check_locked_port_support || return 0
> > > +
> > > +	ping_do $h1 192.0.2.2
> > > +	check_err $? "MAB: Ping did not work before locking
port"
> > > +
> > > +	bridge link set dev $swp1 locked on
> > > +	bridge link set dev $swp1 learning on
> > 
> > "locked on learning on" is counter intuitive and IMO very
much a
> > misconfiguration that we should have disallowed when the
"locked" option
> > was introduced. It is my understanding that the only reason we are
even
> > talking about it is because mv88e6xxx needs it for MAB for some
reason.
> 
> As the way mv88e6xxx implements "learning off" is to remove port
association
> for ingress packets on a port, but that breaks many other things such as
> refreshing ATU entries and violation interrupts, so it is needed and the
> question is then what is the worst to have 'learning on' on a
locked port or
> to have the locked port enabling learning in the driver silently?
> 
> Opinions seem to differ. Note that even on locked ports without MAB, port
> association on ingress is still needed in future as I have a dynamic ATU
> patch set coming, that uses age out violation and hardware refreshing to
let
> the hardware keep the dynamic entries as long as the authorized station is
> sending, but will age the entry out if the station keeps silent for the
> ageing time. But that patch set is dependent on this patch set, and I
don't
> think I can send it before this is accepted...
Can you explain how you envision user space to work once everything is
merged? I want to make sure we have the full picture before more stuff
is merged. From what you describe, I expect the following:

1. Create topology, assuming two unauthorized ports:

# ip link add name br0 type bridge no_linklocal_learn 1 (*)
# ip link set dev swp1 master br0
# ip link set dev swp2 master br0
# bridge link set dev swp1 learning on locked on
# bridge link set dev swp2 learning on locked on
# ip link set dev swp1 up
# ip link set dev swp2 up
# ip link set dev br0 up

2. Assuming h1 behind swp1 was authorized using 802.1X:

# bridge fdb replace $H1_MAC dev swp1 master dynamic

3. Assuming 802.1X authentication failed for h2 behind swp2, enable MAB:

# bridge link set dev swp2 mab on

4. Assuming $H2_MAC is in our allow list:

# bridge fdb replace $H2_MAC dev swp2 master dynamic

Learning is on in order to refresh the dynamic entries that user space
installed.

(*) Need to add support for this option in iproute2. Already exposed
over netlink (see 'IFLA_BR_MULTI_BOOLOPT').

On 2022-08-29 09:40, Ido Schimmel wrote:
> On Sun, Aug 28, 2022 at 02:00:29PM +0200, netdev at kapio-technology.com 
> wrote:
>> On 2022-08-27 20:21, Ido Schimmel wrote:
>> > On Fri, Aug 26, 2022 at 01:45:38PM +0200, Hans Schultz wrote:
>> > > +locked_port_mab()
>> > > +{
>> > > +	RET=0
>> > > +	check_locked_port_support || return 0
>> > > +
>> > > +	ping_do $h1 192.0.2.2
>> > > +	check_err $? "MAB: Ping did not work before locking
port"
>> > > +
>> > > +	bridge link set dev $swp1 locked on
>> > > +	bridge link set dev $swp1 learning on
>> >
>> > "locked on learning on" is counter intuitive and IMO
very much a
>> > misconfiguration that we should have disallowed when the
"locked" option
>> > was introduced. It is my understanding that the only reason we are
even
>> > talking about it is because mv88e6xxx needs it for MAB for some
reason.
>> 
>> As the way mv88e6xxx implements "learning off" is to remove
port
>> association
>> for ingress packets on a port, but that breaks many other things such 
>> as
>> refreshing ATU entries and violation interrupts, so it is needed and 
>> the
>> question is then what is the worst to have 'learning on' on a
locked
>> port or
>> to have the locked port enabling learning in the driver silently?
>> 
>> Opinions seem to differ. Note that even on locked ports without MAB, 
>> port
>> association on ingress is still needed in future as I have a dynamic 
>> ATU
>> patch set coming, that uses age out violation and hardware refreshing 
>> to let
>> the hardware keep the dynamic entries as long as the authorized 
>> station is
>> sending, but will age the entry out if the station keeps silent for 
>> the
>> ageing time. But that patch set is dependent on this patch set, and I 
>> don't
>> think I can send it before this is accepted...
> 
> Can you explain how you envision user space to work once everything is
> merged? I want to make sure we have the full picture before more stuff
> is merged. From what you describe, I expect the following:
> 
> 1. Create topology, assuming two unauthorized ports:
> 
> # ip link add name br0 type bridge no_linklocal_learn 1 (*)
> # ip link set dev swp1 master br0
> # ip link set dev swp2 master br0
> # bridge link set dev swp1 learning on locked on
> # bridge link set dev swp2 learning on locked on
The final decision on this rests with you I would say. Actually I forgot 
to remove the port association in the driver in this version.
> # ip link set dev swp1 up
> # ip link set dev swp2 up
> # ip link set dev br0 up
> 
> 2. Assuming h1 behind swp1 was authorized using 802.1X:
> 
> # bridge fdb replace $H1_MAC dev swp1 master dynamic
With the new MAB flag 'replace' is not needed when MAB is not enabled.
> 
> 3. Assuming 802.1X authentication failed for h2 behind swp2, enable 
> MAB:
> 
> # bridge link set dev swp2 mab on
> 
> 4. Assuming $H2_MAC is in our allow list:
> 
> # bridge fdb replace $H2_MAC dev swp2 master dynamic
> 
> Learning is on in order to refresh the dynamic entries that user space
> installed.
Yes, port association is needed for those reasons. :-)
> 
> (*) Need to add support for this option in iproute2. Already exposed
> over netlink (see 'IFLA_BR_MULTI_BOOLOPT').
Should I do that in this patch set?

On 2022-08-29 09:40, Ido Schimmel wrote:
> On Sun, Aug 28, 2022 at 02:00:29PM +0200, netdev at kapio-technology.com 
> wrote:
>> On 2022-08-27 20:21, Ido Schimmel wrote:
>> > "locked on learning on" is counter intuitive and IMO
very much a
>> > misconfiguration that we should have disallowed when the
"locked" option
>> > was introduced. It is my understanding that the only reason we are
even
>> > talking about it is because mv88e6xxx needs it for MAB for some
reason.
>> 
>> As the way mv88e6xxx implements "learning off" is to remove
port
>> association
>> for ingress packets on a port, but that breaks many other things such 
>> as
>> refreshing ATU entries and violation interrupts, so it is needed and 
>> the
>> question is then what is the worst to have 'learning on' on a
locked
>> port or
>> to have the locked port enabling learning in the driver silently?
>> 
>> Opinions seem to differ. Note that even on locked ports without MAB, 
>> port
>> association on ingress is still needed in future as I have a dynamic 
>> ATU
>> patch set coming, that uses age out violation and hardware refreshing 
>> to let
>> the hardware keep the dynamic entries as long as the authorized 
>> station is
>> sending, but will age the entry out if the station keeps silent for 
>> the
>> ageing time. But that patch set is dependent on this patch set, and I 
>> don't
>> think I can send it before this is accepted...
> 
> # bridge link set dev swp1 learning on locked on
> # bridge link set dev swp2 learning on locked on
As we must think in how most drivers work, which I am not knowledgeable 
of, I think that it is probably the best to think of the way mv88e6xxx 
works as an outlier.
If that is true, then I think the best option is to go with:
#bridge link set dev $swp1 learning off locked on
#bridge link set dev $swp2 learning off locked on

Then the cleanup side will just be:
#bridge link set dev $swp1 locked off
#bridge link set dev $swp2 locked off

The state 'learning off' is then consistent with the behavior of both 
the bridge and driver after the cleanup.