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Date: Sat, 22 Oct 2022 16:11:56 +0200 From: netdev@...io-technology.com To: Ido Schimmel <idosch@...dia.com> Cc: Vladimir Oltean <olteanv@...il.com>, davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org, Oleksandr Mazur <oleksandr.mazur@...ision.eu>, Florian Fainelli <f.fainelli@...il.com>, Andrew Lunn <andrew@...n.ch>, Vivien Didelot <vivien.didelot@...il.com>, Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Kurt Kanzenbach <kurt@...utronix.de>, Hauke Mehrtens <hauke@...ke-m.de>, Woojung Huh <woojung.huh@...rochip.com>, UNGLinuxDriver@...rochip.com, Sean Wang <sean.wang@...iatek.com>, Landen Chao <Landen.Chao@...iatek.com>, DENG Qingfang <dqfext@...il.com>, Matthias Brugger <matthias.bgg@...il.com>, Claudiu Manoil <claudiu.manoil@....com>, Alexandre Belloni <alexandre.belloni@...tlin.com>, Jiri Pirko <jiri@...nulli.us>, Ivan Vecera <ivecera@...hat.com>, Roopa Prabhu <roopa@...dia.com>, Nikolay Aleksandrov <razor@...ckwall.org>, Shuah Khan <shuah@...nel.org>, Russell King <linux@...linux.org.uk>, Christian Marangi <ansuelsmth@...il.com>, Daniel Borkmann <daniel@...earbox.net>, Yuwei Wang <wangyuweihx@...il.com>, Petr Machata <petrm@...dia.com>, Florent Fourcot <florent.fourcot@...irst.fr>, Hans Schultz <schultz.hans@...il.com>, Joachim Wiberg <troglobit@...il.com>, Amit Cohen <amcohen@...dia.com>, linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org, bridge@...ts.linux-foundation.org, linux-kselftest@...r.kernel.org Subject: Re: [PATCH v8 net-next 10/12] net: dsa: mv88e6xxx: mac-auth/MAB implementation On 2022-10-22 15:49, Ido Schimmel wrote: > On Fri, Oct 21, 2022 at 09:14:11PM +0300, Vladimir Oltean wrote: >> On Fri, Oct 21, 2022 at 07:39:34PM +0200, netdev@...io-technology.com >> wrote: >> > Well, with this change, to have MAB working, the bridge would need learning on >> > of course, but how things work with the bridge according to the flags, they >> > should also work in the offloaded case if you ask me. There should be no >> > difference between the two, thus MAB in drivers would have to be with >> > learning on. >> >> Am I proposing for things to work differently in the offload and >> software case, and not realizing it? :-/ >> >> The essence of my proposal was to send a bug fix now which denies >> BR_LEARNING to be set together with BR_PORT_LOCKED. The fact that >> link-local traffic is learned by the software bridge is something >> unintended as far as I understand. >> >> You tried to fix it here, and as far as I could search in my inbox, >> that >> didn't go anywhere: >> https://lore.kernel.org/netdev/47d8d747-54ef-df52-3b9c-acb9a77fa14a@blackwall.org/T/#u >> >> I thought only mv88e6xxx offloads BR_PORT_LOCKED, but now, after >> searching, I also see prestera has support for it, so let me add >> Oleksandr Mazur to the discussion as well. I wonder how they deal with >> this? Has somebody come to rely on learning being enabled on a locked >> port? >> >> >> MAB in offloading drivers will have to be with learning on (same as in >> software). When BR_PORT_LOCKED | BR_LEARNING will be allowed together >> back in net-next (to denote the MAB configuration), offloading drivers >> (mv88e6xxx and prestera) will be patched to reject them. They will >> only >> accept the two together when they implement MAB support. >> >> Future drivers after this mess has been cleaned up will have to look >> at >> the BR_PORT_LOCKED and BR_LEARNING flag in combination, to see which >> kind of learning is desired on a port (secure, CPU based learning or >> autonomous learning). >> >> Am I not making sense? > > I will try to summarize what I learned from past discussions because I > think it is not properly explained in the commit messages. > > If you look at the hostapd fork by Westermo [1], you will see that they > are authorizing hosts by adding dynamic FDB entries from user space, > not Those dynamic FDB entries are to be dynamic ATU entries by a patch set that I have ready, but which I have not submitted as I was expecting to submit it after this patch set was accepted. The important aspect of Dynamic ATU entries is that the HW refreshes the ATU entries with an active host. > static ones. Someone from Westermo will need to confirm this, but I I represent WesterMo in the upstreaming of these patches, and can confirm that both for hostapd and the MAB solution, WesterMo authorizes by using dynamic entries. > guess the reasons are that a) They want hosts that became silent to > lose > their authentication after the aging time b) They want hosts to lose > their authentication when the carrier of the bridge port goes down. > This > will cause the bridge driver to flush dynamic FDB entries, but not > static ones. Otherwise, an attacker with physical access to the switch > and knowledge of the MAC address of the authenticated host can connect > a > different (malicious) host that will be able to communicate through the > bridge. Seems correct, only that it must be specified that it must be the switchcore and not the bridge that ages the entries, thus ATU entries. > > In the above scenario, learning does not need to be on for the bridge > to > populate its FDB, but rather for the bridge to refresh the dynamic FDB > entries installed by hostapd. This seems like a valid use case and one > needs a good reason to break it in future kernels. > > Regarding learning from link-local frames, this can be mitigated by [2] > without adding additional checks in the bridge. I don't know why this > bridge option was originally added, but if it wasn't for this use case, > then now it has another use case. > > Regarding MAB, from the above you can see that a pure 802.1X > implementation that does not involve MAB can benefit from locked bridge > ports with learning enabled. It is therefore not accurate to say that > one wants MAB merely by enabling learning on a locked port. Given that > MAB is a proprietary extension and much less secure than 802.1X, we can > assume that there will be deployments out there that do not use MAB and > do not care about notifications regarding locked FDB entries. I > therefore think that MAB needs to be enabled by a separate bridge port > flag that is rejected unless the bridge port is locked and has learning > enabled. > > Regarding hardware offload, I have an idea (needs testing) on how to > make mlxsw work in a similar way to mv88e6xxx. That is, does not > involve > injecting frames that incurred a miss to the Rx path. If you guys want, > I'm willing to take a subset of the patches here, improve the commit > message, do some small changes and submit them along with an mlxsw > implementation. My intention is not to discredit anyone (I will keep > the > original authorship), but to help push this forward and give another > example of hardware offload. You are very welcome to help pushing this forward for my sake, I just need to know how it will affect this patch set. :-) > > [1] > https://github.com/westermo/hostapd/commit/10c584b875a63a9e58b0ad39835282545351c30e#diff-338b6fad34b4bdb015d7d96930974bd96796b754257473b6c91527789656d6ed > [2] > https://git.kernel.org/pub/scm/network/iproute2/iproute2-next.git/commit/?id=c74a8bc9cf5d6b6c9d8c64d5a80c5740165f315a
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