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Date:      Sun, 7 Sep 2014 14:07:45 -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-Vmokt_kgxW3aPEDcNwg_ZVrCotqF_tOP1YjZCtO=nCZ8z5Q@mail.gmail.com>
In-Reply-To: <540CC53A.90600@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>

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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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