On Tue, 10 Jul 2018 at 12:16, Denis Kenzior [off-list ref] wrote:

I think we had this conversation before.  Up to 802.11-2012, PTK Rekey
was not really explicitly mentioned as possible.  There were hints and
stuff, but no explicit language.

I think in 802.11-2016 they finally explicitly say that this is possible.

However, we seem to have networks that perform PTK Rekey and even full
802.1X re-auth every hour (eduroam for example).  How is this working?
Or is it a case of it not always working?

It's ... buggy. Right now I'm hitting race conditions (which someone
is actively working on now, yay!) where frames are going out in a
narrow window between the hardware key being rekeyed (and the RX PN
being set to 0) and an older frame going out with a larger PN with the
new key. The receiver sees the frame with the old, large PN but the
new key and .. well, subsequent traffic hangs. I know it's buggy on
ath9k (what we're using at work.) ath10k seems to fare better - it at
least is doing key programming and PN assignment in firmware, so it
has a chance to keep it in sync.



-adrian