[Make-wifi-fast] [PATCH v7] mac80211: Move reorder-sensitive TX handlers to after TXQ dequeue.

Toke Høiland-Jørgensen toke at toke.dk
Mon Sep 5 13:59:06 EDT 2016

Felix Fietkau <nbd at nbd.name> writes:

> On 2016-09-05 13:30, Toke Høiland-Jørgensen wrote:
>> The TXQ intermediate queues can cause packet reordering when more than
>> one flow is active to a single station. Since some of the wifi-specific
>> packet handling (notably sequence number and encryption handling) is
>> sensitive to re-ordering, things break if they are applied before the
>> TXQ.
>> This splits up the TX handlers and fast_xmit logic into two parts: An
>> early part and a late part. The former is applied before TXQ enqueue,
>> and the latter after dequeue. The non-TXQ path just applies both parts
>> at once.
>> Because fragments shouldn't be split up or reordered, the fragmentation
>> handler is run after dequeue. Any fragments are then kept in the TXQ and
>> on subsequent dequeues they take precedence over dequeueing from the FQ
>> structure.
>> This approach avoids having to scatter special cases for when TXQ is
>> enabled, at the cost of making the fast_xmit and TX handler code
>> slightly more complex.
> In my test, this one completely breaks ath9k with the txq patch.
> One or two packets go through, then tx stalls completely.

I assume you are testing on LEDE? It requires a change to work with the
patch in the LEDE tree that puts hdrlen into ieee80211_tx_data. Did you
fix that? Otherwise multicast (and possibly other things) will break

I have a version that should work with LEDE here:



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