On Thu, Mar 17, 2022 at 05:07:15PM +0100, Hans Schultz wrote: > On tor, mar 17, 2022 at 17:36, Vladimir Oltean <olteanv@xxxxxxxxx> wrote: > > On Thu, Mar 17, 2022 at 03:19:46PM +0100, Andrew Lunn wrote: > >> On Thu, Mar 17, 2022 at 09:52:15AM +0100, Hans Schultz wrote: > >> > On tor, mar 17, 2022 at 01:34, Vladimir Oltean <olteanv@xxxxxxxxx> wrote: > >> > > On Mon, Mar 14, 2022 at 11:46:51AM +0100, Hans Schultz wrote: > >> > >> >> @@ -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. > > >> > 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. > > > > 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. > > > > 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? > >> > > 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
