Question on setting key right after the EAPOL 4/4 is sent.

[Ben Greear]

On 06/08/2017 04:36 PM, Denis Kenzior wrote:
> Hi Ben,
>
>> The problem I see is that sometimes (and quite often when I am using lots
>> of vdevs and thus the NIC is busy), the keys are set before the EAPOL 4/4
>> hits the air.  When the key is set, the NIC will no longer transmit the
>> frame because of key-length issues in the tx-descriptor (ath10k wave-2
>> in this case).
>
> We have encountered something similar.  In our case we were seeing PAE packets (e.g. 4WayHandshake packet 1 of 4) before seeing the connect events on nl80211.
>
>> I suspect that there is a fundamental race between the EAPOL packet-tx
>> logic and the key-set logic, but supplicant appears to act as though
>> they are natually synchronized.
>
> Fundamentally there is a race between the genl/nl80211 socket to the kernel and the PAE socket that handles the authentication aspects.  I think the only way to
> fix this is to make sure that PAE flows over the genl/nl80211 socket to preserve the proper order of events.  However there are lots of dragons in the kernel
> side of this and we haven't been brave enough to venture into the depths yet :)

I think that would just push the problem lower.  Probably a real fix would be to somehow propagate
the tx-status for the specific packet back to the supplicant and only then it would know that the
key could be set.

Thanks,
Ben

-- 
Ben Greear <greearb at candelatech.com>
Candela Technologies Inc  http://www.candelatech.com