Subject: Re: ACK matching [was: TX status reporting with help of an ack
	queue]
From: Mattias Nissler <mattias.nissler@gmx.de>
To: Johannes Berg <johannes@sipsolutions.net>
Cc: Mikko =?ISO-8859-1?Q?Virkkil=E4?= <mikko.virkkila@bluegiga.com>,
	Ivo van Doorn <ivdoorn@gmail.com>,
	rt2400-devel@lists.sourceforge.net,
	"John W. Linville" <linville@tuxdriver.com>,
	linux-wireless <linux-wireless@vger.kernel.org>, dsd@gentoo.org,
	kune@deine-taler.de
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Date: Fri, 19 Sep 2008 12:19:39 +0200
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On Fri, 2008-09-19 at 11:54 +0200, Johannes Berg wrote:
> On Fri, 2008-09-19 at 11:46 +0200, Mattias Nissler wrote:
> 
> > This brings up the question whether we can do without tx status
> > reporting. Does anyone know why hostapd requires the tx status? As far
> > as I understand, mac80211 only uses the tx status reporting only for the
> > tx rate control. Rate control algos that don't use tx status are
> > definitely feasible (and in fact we'll need one for rt73).
> 
> mac80211 also uses it for reporting the sent frame to userspace on
> monitor interfaces.

Yeah, that's what hostapd relies on. But mac80211 really does not care
to much how userspace uses the information.

> 
> > I'll look into hostapd to figure out whether the tx status reporting is
> > really required when I find some time.
> 
> hostapd requires this because it needs to know whether a station
> acknowledged a frame or not to proceed its state machine, it's just how
> it has to work. If the hardware can't deal with that I guess you can't
> implement AP mode properly.

Well, maybe we can work around this requirement? I still need to learn
about the details, but what happens for example if the STA sends the ACK
and then resets due to a crash? I guess the AP is able to cope with
that, no? So maybe we can relax the rules a bit (unless we become really
incompliant with the standard of course).

Mattias