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Date:      Mon, 8 Sep 2014 15:17:08 -0700
From:      Adrian Chadd <adrian@freebsd.org>
To:        Nathan Whitehorn <nwhitehorn@freebsd.org>
Cc:        "freebsd-wireless@freebsd.org" <freebsd-wireless@freebsd.org>
Subject:   Re: Issues with urtwn
Message-ID:  <CAJ-VmongioOZQS561Qq5S1T0UVnBifxrQf8P0rr8jEWzk=dumQ@mail.gmail.com>
In-Reply-To: <540E2A2D.4090301@freebsd.org>
References:  <540C751F.6050202@freebsd.org> <CAJ-VmokyPcS077wHiP4Mdetms=meqk47v29fKA1edidhorVQpg@mail.gmail.com> <540C92D6.4030106@freebsd.org> <CAJ-VmomMwJOSz7hyAfeEgPE=qBfYm7fTOo5km8JJk4g62JxTkg@mail.gmail.com> <540CC53A.90600@freebsd.org> <CAJ-Vmokt_kgxW3aPEDcNwg_ZVrCotqF_tOP1YjZCtO=nCZ8z5Q@mail.gmail.com> <540E2A2D.4090301@freebsd.org>

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Please compile your kernel with IEEE80211_DEBUG, then enable debugging
- wlandebug +state +power

You can disable powersave with 'ifconfig wlan0 -powersave', but it
shouldn't be enabled by default.



-a


On 8 September 2014 15:14, Nathan Whitehorn <nwhitehorn@freebsd.org> wrote:
> 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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