From: "Chen, Stephen" <scchen@qca.qualcomm.com>
To: Marco Fonseca <marco@tampabay.rr.com>
CC: Christian Lamparter <chunkeey@googlemail.com>,
	Johannes Berg <johannes@sipsolutions.net>,
	"linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>
Subject: RE: carl9170: Unintentional transmission in monitor mode?
Date: Fri, 17 Aug 2012 02:59:40 +0000
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To be honest, I have no idea why the device was transmitting invalid frame.
If the device is not in monitor mode, will it still transmit invalid frame in your setup?


Thank you.
Stephen


-----Original Message-----
From: Marco Fonseca [mailto:marco@tampabay.rr.com] 
Sent: Friday, August 17, 2012 10:30 AM
To: Chen, Stephen
Cc: Christian Lamparter; Johannes Berg; linux-wireless@vger.kernel.org
Subject: Re: carl9170: Unintentional transmission in monitor mode?

In my setup I had used a secondary sniffer in order to see what was going on.
I was able to reproduce the problem with a single ping with a payload of 2000 (less to look at in wireshark), but I was never able to capture a valid frame from the AR9170.  I do know it was transmitting though, as I could see it on the spectrum analyzer.  I just assumed whatever was going out wasn't a valid
frame...(?)

Marco


On Fri, Aug 17, 2012 at 02:03:00AM +0000, Chen, Stephen wrote:
> Can we tell what kind of unexpected frame are been transmitted? (Data 
> frame or which kind of control frame?) That may give us a clue.
> 
> 
> Thank you.
> Stephen
> 
> -----Original Message-----
> From: Christian Lamparter [mailto:chunkeey@googlemail.com]
> Sent: Friday, August 17, 2012 3:35 AM
> To: Johannes Berg
> Cc: Marco Fonseca; linux-wireless@vger.kernel.org; Chen, Stephen
> Subject: Re: carl9170: Unintentional transmission in monitor mode?
> 
> On Thursday, August 16, 2012 09:20:55 PM Johannes Berg wrote:
> > On Thu, 2012-08-09 at 21:43 +0200, Christian Lamparter wrote:
> > > On Thursday, August 09, 2012 06:54:34 PM Marco Fonseca wrote:
> > > > Hello All,
> > > > 
> > > > I've noticed unexpected transmissions from the AR9170 while in 
> > > > monitor mode and using tcpdump (and sometimes without tcpdump 
> > > > running).  These transmissions degrade (pretty significantly) 
> > > > performance of other STA/AP on the channel (as seen by iperf 
> > > > going from 60mbit/s to almost nill).  As best I can tell these 
> > > > transmissions never coalesces into an actual frame in the air 
> > > > (at least not one I'm able to pick up with a second different adapter in monitor mode).
> > > > 
> > > > Are there any known reasons/bugs on this?  Is there anyway to 
> > > > completely silence the transmitter of the AR9170 while still allowing reception?
> > > > 
> > > yes. <http://www.spinics.net/lists/linux-wireless/msg88896.html>
> > > 
> > > a solution is described in:
> > > <http://www.spinics.net/lists/linux-wireless/msg89279.html>
> > > 
> > > (iw dev wlanX set monitor none - if I'm not mistaken)
> > 
> > I've seen this before too -- what flag causes the issue, and why?
> Well that would be:
> FIF_OTHER_BSS or FIF_PROMISC_IN_BSS
> 
> either one of these will set following flags for the hardware:
> 
> AR9170_MAC_RX_CTRL_ACK_IN_SNIFFER
> AR9170_MAC_SNIFFER_ENABLE_PROMISC
> 
> About the issue, I'm really can't tell w/o schematics of the hardware. It could be that ACK_IN_SNIFFER is more of a debug/test flag than a real feature?
> 
> (Anyway, I cc'd Stephen. Maybe he knows more)
> 
> Regards,
> 	Chr