On tor, mar 17, 2022 at 18:18, Vladimir Oltean [off-list ref] wrote:

On Thu, Mar 17, 2022 at 05:07:15PM +0100, Hans Schultz wrote:

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On tor, mar 17, 2022 at 17:36, Vladimir Oltean [off-list ref] wrote:

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On Thu, Mar 17, 2022 at 03:19:46PM +0100, Andrew Lunn wrote:

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On Thu, Mar 17, 2022 at 09:52:15AM +0100, Hans Schultz wrote:

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On tor, mar 17, 2022 at 01:34, Vladimir Oltean [off-list ref] wrote:

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On Mon, Mar 14, 2022 at 11:46:51AM +0100, Hans Schultz wrote:

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@@ -396,6 +414,13 @@ static irqreturn_t mv88e6xxx_g1_atu_prob_irq_thread_fn(int irq, void *dev_id)
 				    "ATU miss violation for %pM portvec %x spid %d\n",
 				    entry.mac, entry.portvec, spid);
 		chip->ports[spid].atu_miss_violation++;
+		if (mv88e6xxx_port_is_locked(chip, chip->ports[spid].port))
+			err = mv88e6xxx_switchdev_handle_atu_miss_violation(chip,
+									    chip->ports[spid].port,
+									    &entry,
+									    fid);

Do we want to suppress the ATU miss violation warnings if we're going to
notify the bridge, or is it better to keep them for some reason?
My logic is that they're part of normal operation, so suppressing makes
sense.

I have been seeing many ATU member violations after the miss violation is
handled (using ping), and I think it could be considered to suppress the ATU member
violations interrupts by setting the IgnoreWrongData bit for the
port (sect 4.4.7). This would be something to do whenever a port is set in locked mode?

So the first packet with a given MAC SA triggers an ATU miss violation
interrupt.

You program that MAC SA into the ATU with a destination port mask of all
zeroes. This suppresses further ATU miss interrupts for this MAC SA, but
now generates ATU member violations, because the MAC SA _is_ present in
the ATU, but not towards the expected port (in fact, towards _no_ port).

Especially if user space decides it doesn't want to authorize this MAC
SA, it really becomes a problem because this is now a vector for denial
of service, with every packet triggering an ATU member violation
interrupt.

So your suggestion is to set the IgnoreWrongData bit on locked ports,
and this will suppress the actual member violation interrupts for
traffic coming from these ports.

So if the user decides to unplug a previously authorized printer from
switch port 1 and move it to port 2, how is this handled? If there isn't
a mechanism in place to delete the locked FDB entry when the printer
goes away, then by setting IgnoreWrongData you're effectively also
suppressing migration notifications.

I don't think such a scenario is so realistic, as changing port is not
just something done casually, besides port 2 then must also be a locked
port to have the same policy.

I think it is very realistic. It is also something which does not work
is going to cause a lot of confusion. People will blame the printer,
when in fact they should be blaming the switch. They will be rebooting
the printer, when in fact, they need to reboot the switch etc.

I expect there is a way to cleanly support this, you just need to
figure it out.

Hans, why must port 2 also be a locked port? The FDB entry with no
destinations is present in the ATU, and static, why would just locked
ports match it?

You are right of course, but it was more from a policy standpoint as I
pointed out. If the FDB entry is removed after some timeout and the
device in the meantime somehow is on another port that is not locked
with full access, the device will of course get full access.
But since it was not given access in the first instance, the policy is
not consistent.

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The other aspect is that the user space daemon that authorizes catches
the fdb add entry events and checks if it is a locked entry. So it will
be up to said daemon to decide the policy, like remove the fdb entry
after a timeout.

When you say 'timeout', what is the moment when the timer starts counting?
The last reception of the user space daemon of a packet with this MAC SA,
or the moment when the FDB entry originally became unlocked?

I think that if the device is not given access, a timer should be
started at that moment. No further FDB add events with the same MAC
address will come of course until the FDB entry is removed, which I
think would be done based on the said timer.

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I expect that once a device is authorized, and forwarding towards the
devices that it wants to talk to is handled in hardware, that the CPU no
longer receives packets from this device. In other words, are you saying
that you're going to break networking for the printer every 5 minutes,
as a keepalive measure?

No, I don't think that would be a good idea, but as we are in userspace,
that is a policy decision of those creating the daemon. The kernel just
facilitates, it does not make those decisions as far as I think.

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I still think there should be a functional fast path for authorized
station migrations.

I am not sure in what way you are suggesting that should be, if the
kernel should actively do something there? If a station is authorized,
and somehow is transferred to another port, if that port is not locked it
will get access, if the port is locked a miss violation will occur etc...

Wait, if the new port is locked and the device was previously
authorized, why will the new port trigger a miss violation? This is the
part I'm not following. The authorization is still present in the form
of an ATU entry on the old locked port, is it not?

I am sure (have not tested) that a miss violation will occur. It might
be a member violation in this instance though.
When thinking of it, afaik there is no way today of having fine control
over the DPV when adding a FDB entry.
If the DPV could be finer controlled the entry could cover several
possible ports and the fast (immediate migration) will be accomplished?

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Oh, btw, my question was: could you consider suppressing the _prints_ on
an ATU miss violation on a locked port?

As there will only be such on the first packet, I think it should be
logged and those prints serve that purpose, so I think it is best to
keep the print.
If in the future some tests or other can argue for suppressing the
prints, it is an easy thing to do.

Please use a traffic generator and try to DOS one of your own
switches. Can you?

	  Andrew