[PATCH] mac80211: always use mac80211 loss detection

Felix Fietkau nbd at nbd.name
Fri Jun 23 03:47:17 PDT 2023

On 23.06.23 12:29, David Bauer wrote:
> Hi Felix,
> On 6/23/23 08:55, Felix Fietkau wrote:
>> On 18.05.23 11:19, David Bauer wrote:
>>> ath10k does not report excessive loss in case of broken block-ack
>>> sessions. The loss is communicated to the host-os, but ath10k does not
>>> trigger a low-ack events by itself.
>>> The mac80211 framework for loss detection however detects this
>>> circumstance well in case of ath10k. So use it regardless of ath10k's
>>> own loss detection mechanism.
>>> Signed-off-by: David Bauer <mail at david-bauer.net>
>> Please make a patch for ath10k instead of turning the flag into a no-op in mac80211.
> The rationale for removal was in fact to avoid patching ath1xk separately, given these
> are the only drivers using this flag.
> I'm aware this is not the nicest approach, do you have any insight if there's a downside
> to always keeping mac80211 loss detection active?
> I however still respect the preferation of keeping this limited to specific drivers, I'm
> just interested if there's a deeper rationale / problem i did not spot :)
> Just to outline the issue this is trying to avoid - Intel clients started dropping their
> BA sessions sometimes in late 2020 without notifying the AP. The ath10k firmware keeps
> retransmitting exclusive to the device at the lowest rate while not indicating a low-ack
> situation to the host-os, avoiding station kickout. This results in very low throughput
> for all connected stations (aql enabled) up to DoS of the AP (aql disabled).

My rationale is this: changes to the driver dropping that flag can be 
upstreamed, because your description implies that it fixes a real bug.
A mac80211 patch turning the flag into an no-op will be rejected, since 
it doesn't make any sense to keep the flag around.
If it turns out that all ath drivers can't use this flag because of the 
issue you're describing, we can remove it upstream from mac80211 
entirely instead of turning it into a dummy no-op.

- Felix

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