On 09/26/2018 11:26 AM, Johannes Berg wrote:
On Wed, 2018-09-26 at 11:04 -0700, Ben Greear wrote:
I have been running with mac80211/mlme.c's max_nullfunc_tries set to 5 for many years.
Long ago it helped with connectivity issues with lots of vdevs and and/orloaded APs
if I recall correctly.
That's different, that's the number of distinct frames mac80211 will
send.
I thought you were asking about *retries*.
Well, it retries the probe action 5 times in my case.
I am also asking about total amount of retried frames on the air.
In fact, I see 62 frames captured on air all with the same sequence number
in the test I just did, and subsequent frames with the next seq-no are sent
immediately after the first one. The frames are all right after each other, so
I guess this is probably firmware doing lots of HW retransmits and then *also*
doing software retransmits in the firmware (my reading of mlme.c indicates it should
only probe every 500ms).
Yes.
I think I'll start by making sure the firmware does not do software retransmits
for frames from the driver (self-gen frames are OK to be retransmitted I guess).
You do want it to be doing retries for frames from the driver, since you
want it to recover from temporary collisions with a microwave and
whatnot ... just not *that many*, I guess.
From what I can tell so far, my firmware has this sort of logic:
frame from stack to the driver
-> send to firmware
-> in firmware, hardware will do up to X retries (maybe 16 or so, need to check)
-> On failure, the firmware may re-queue the packet (firmware-software retry)
-> back to hardware retries (~32 frames on air at this point)
...
Eventually tx-fail notification is sent back to the driver one way or another.
I am thinking it would be best to have the software retry in the firmware
disabled.
Then, when mac80211 sends a null-data frame, you would see at most about
16 of them on air, every 500ms or so until it recovers or considers the
connection lost.
Thanks,
Ben
--
Ben Greear <greearb@xxxxxxxxxxxxxxx>
Candela Technologies Inc http://www.candelatech.com
