[PATCH 7/8] GAS: End remain-on-channel due to delayed GAS comeback request

Jouni Malinen j at w1.fi
Sun Dec 20 12:35:42 PST 2015

On Sun, Dec 20, 2015 at 07:55:48PM +0200, Jouni Malinen wrote:
> I fixed that by keeping the query->offchannel_tx_started tracking
> up-to-date with patch 7/8 behavior and using the longer wait time for
> the first comeback request if the initial wait time had been canceled
> (which it really is in every single case now, but that could be modified
> to consider the fragmentation-without-wait case with very short
> comeback delay to skip stopping the initial ROC). This provides
> significant further speedup when both patches 7 and 8 are applied.

That special case of fragmentation (comeback delay 1) is now handled
without stopping the initial ROC.

> To make it acceptable to test with shorter wait time first, I added a
> mechanism to retry full GAS sequence if any waits for a comeback
> response fail. This second attempt will use the old timeout of 1000 ms.
> With this, the end result is actually more robust than the previous
> design and significantly faster for the fragmented case with drivers
> that cannot extend pending ROC. I haven't yet pushed this into the
> master branch, but if nothing unexpected shows up, I'll probably do so.

I pushed this with a fixed patch 8/8 into the master branch. It is not
exactly perfect since an exchange taking more than 850 ms will end up in
the state where each new TX operation hits the issue of the pending ROC
ending up sooner. That said, this is significantly faster than what was
there previously and I'm not sure there would be sufficient
justification for the extra complexity within wpa_supplicant to try to
track the remaining ROC duration within kernel (i.e., if someone wants
to optimize that, it might be better to spend the effort working on
kernel side making it possible to extend the ongoing ROC and/or
providing more convenient events to user space to indicate when the wait
for an offloaded TX operation has completed in a way that would benefit
from wpa_supplicant requesting a longer duration for the next TX
Jouni Malinen                                            PGP id EFC895FA

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