On Mon, 2019-08-19 at 21:57 +0200, Alexander Wetzel wrote: > > > + > > > + /* The new Tx API does not allow to pass the key or keyid of a MPDU to > > > + * the hw, preventing us to control which key(id) to use per MPDU. > > > + * Till that's fixed we can't use Extended Key ID for the newer cards. > > > > Technically we still don't need per MPDU, we just need to switch which > > one to use for TX after installing it for RX already. > > The Extended Key ID API we finally merged in mac80211 is not notifying > the driver when to switch the key over to the other id.
Oh, right, good point. > The current API provides the key/keyid per MPDU and let's mac80211 have > the full control what's the correct key for each frame. Yeah, but as you noticed we no longer have that control per MPDU with the new TX API in iwlmvm. > That's especially critical for drivers setting > IEEE80211_KEY_FLAG_GENERATE_IV and/or supporting A-MPDU's. Allowing the > driver to override the mac80211 decision is only safe when the > driver/card generates the PNs itself and also handles the A-MPDU key > borders correctly. Sure, the device does generate the PN itself now with the new TX API too. It doesn't care about A-MPDU key borders, but it probably could when taught to care about extended key ID. > While less desirable we still could get that working: The mvm driver > would have to detect the key borders and then tell the firmware to > switch over to the other key. But we would have to make sure to not > re-enable A-MPDU aggregation till the card really has switched. I'm not entirely sure off the top of my head how it works, but it seems possible that if we just assign a new PN to retransmits of the same frame but in a new A-MPDU after key switching, it wouldn't actually matter? But then again maybe somewhere it's stated that we must use the same key for all transmit attempts of a single frame? Not sure. I'm also not sure if we could actually assign a PN from the new key for the retransmit, the hardware has to store those back into memory normally. So probably you're right, and we'd have to disable A-MPDUs until we have no outstanding old-key-retransmits, but that seems manageable. johannes
