So it's definitely to do with powersave. Here's a bunch of iterations of ifconfig list sta on my laptop:
ADDR               AID CHAN RATE RSSI IDLE  TXSEQ  RXSEQ CAPS FLAG
54:78:1a:a0:91:22 149 1 54M 37.0 0 4385 37104 EPS A HTCAP RSN WME
ADDR               AID CHAN RATE RSSI IDLE  TXSEQ  RXSEQ CAPS FLAG
54:78:1a:a0:91:22 149 1 54M 37.5 0 4412 39360 EPS A HTCAP RSN WME
ADDR               AID CHAN RATE RSSI IDLE  TXSEQ  RXSEQ CAPS FLAG
54:78:1a:a0:91:22 149 1 54M 37.5 0 4417 39360 EPS AP HTCAP RSN WME
ADDR               AID CHAN RATE RSSI IDLE  TXSEQ  RXSEQ CAPS FLAG
54:78:1a:a0:91:22 149 1 54M 37.5 0 4417 39360 EPS AP HTCAP RSN WME
ADDR               AID CHAN RATE RSSI IDLE  TXSEQ  RXSEQ CAPS FLAG
54:78:1a:a0:91:22 149 1 54M 37.5 0 4417 39360 EPS AP HTCAP RSN WME


You can see the connection die on the third line, when the txseq and rxseq counters stop incrementing and 'P' gets added to the FLAG field. Does this mean the AP has turned on powersave on its end?
-Nathan

On 09/07/14 14:07, Adrian Chadd wrote:
Hi,

The way it's supposed to work in the legacy 802.11 powersave world is
that you send a/any data frame with the powermgt bit in the 802.11
header set to 0 and the AP goes "oh they're awake!" and sends you your
buffered frames.

By default powersave isn't enabled, so we should never be _telling_
the AP that we're going to sleep and the stack always sends data
frames with pwrmgt=0.

You can ensure it's disabled by ifconfig wlan0 -powersave

The code in -HEAD that manages that is in ieee80211_power.c. I added
an explicit powersave support mode for NICs that need it done for them
- and the only one it's enabled for right now is ath(4).

The only reason net80211 sends pwrmgt changes outside of having
net80211 power save enabled is the background scan code.

I'd compile in IEEE80211_DEBUG in your kernel, then I'd use wlandebug
+scan to see if somehow there's some scanning going on; and wlandebug
+power to see if any power save transitions occur.

Are you absolutely sure it's a receive side buffering problem, rather
than a send side problem?

It's also possible that the NIC stops receiving and the AP treats that
as "oh ok, they've gone to sleep for a while." ath(4) now does this in
hostap mode.


-a


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