2024-04-22, 22:55:02 -0700, Rahul Rameshbabu wrote: > On Mon, 22 Apr, 2024 11:23:05 +0200 Sabrina Dubroca <sd@xxxxxxxxxxxxxxx> wrote: > > 2024-04-19, 11:01:20 -0700, Rahul Rameshbabu wrote: > >> On Fri, 19 Apr, 2024 17:05:52 +0200 Sabrina Dubroca <sd@xxxxxxxxxxxxxxx> wrote: > >> > 2024-04-18, 18:17:16 -0700, Rahul Rameshbabu wrote: > >> <snip> > >> >> + /* This datapath is insecure because it is unable to > >> >> + * enforce isolation of broadcast/multicast traffic and > >> >> + * unicast traffic with promiscuous mode on the macsec > >> >> + * netdev. Since the core stack has no mechanism to > >> >> + * check that the hardware did indeed receive MACsec > >> >> + * traffic, it is possible that the response handling > >> >> + * done by the MACsec port was to a plaintext packet. > >> >> + * This violates the MACsec protocol standard. > >> >> + */ > >> >> + DEBUG_NET_WARN_ON_ONCE(true); > >> > > >> > If you insist on this warning (and I'm not convinced it's useful, > >> > since if the HW is already built and cannot inform the driver, there's > >> > nothing the driver implementer can do), I would move it somewhere into > >> > the config path. macsec_update_offload would be a better location for > >> > this kind of warning (maybe with a pr_warn (not limited to debug > >> > configs) saying something like "MACsec offload on devices that don't > >> > support md_dst are insecure: they do not provide proper isolation of > >> > traffic"). The comment can stay here. > >> > > >> > >> I do not like the warning either. I left it mainly if it needed further > >> discussion on the mailing list. Will remove it in my next revision. That > >> said, it may make sense to advertise rx_uses_md_dst over netlink to > >> annotate what macsec offload path a device uses? Just throwing out an > >> idea here. > > > > Maybe. I was also thinking about adding a way to restrict offloading > > only to devices with rx_uses_md_dst. > > That's an option. Basically, devices that do not support rx_uses_md_dst > really only just do SW MACsec but do not return an error if the offload > parameter is passed over netlink so user scripts do not break? Forcing a fallback to SW could be considered a breakage because of the performance regression, so I don't think we can turn this on by default. Then I would simply reject offload on those devices. We could have a compat mode that does the SW fallback you suggest. I don't know if it would be used. > > (Slightly related) I also find it annoying that users have to tell the > > kernel whether to use PHY or MAC offload, but have no way to know > > which one their HW supports. That should probably have been an > > implementation detail that didn't need to be part of uapi :/ > > We could leave the phy / mac netlink keywords and introduce an "on" > option. We deduce whether the device is a phydev or not when on is > passed and set the macsec->offload flag based on that. The phy and mac > options for offload in ip-macsec can then be deprecated. I thought about doing exactly that, and then dropped the idea because it would only help with newer kernels. -- Sabrina
