No beacon activity

[Lara Deek]

Hello Jouni,

Thank you very much for your help! My problems are solved :)

I did have an older mac80211 version, which I updated with a newer one
(by installing the most recent compat-wireless package) and which
solved my beacon problem. My AP is now able to receive beacon frames
from other APs.

My card with the AR5416 chipset is sending beacons. I tried the most
basic approach of first reinstalling hostapd, which seemed to do the
trick, so I think I had done it incorrectly somehow :( The beacon
counter is now incrementing periodically.

Thank you for your time and efforts!
Lara

On Wed, Feb 09, 2011 at 03:19:28PM -0800, Lara Deek wrote:
> The beacons I would like machine A to capture are those of its neighboring
> APs, to identify which APs can potentially conflict with it if they are on
> the same channel. A does not capture any beacons, but only captures probe
> request (broadcast) and response messages.

Which kernel (mac80211) version are you using? Until very recently,
mac80211 filtered out received Beacon frames in AP mode. That was
changed by commit 771bbd09f7febb854dd7c30f983aa57535f9e8c9 (Feb 1). I'm
not sure I understood the setup you are using, but if this device is
indeed in AP mode, that change would be needed to receive the Beacon
frames from other APs.

> Yes, I have used another device in monitor mode (with an Ubiquiti SRC
> 802.11a/b/g MCX card with an AR5004 chipset), which captures beacons from
> sources but never from A. A has an AirMagnet
> card<http://www.airmagnet.com/assets/AirMagnet_802.11abgn_WirelessPCcard_TechSpec.pdf>which
> has an AR5416+AR5133 ath9k supported chipset. I am not sure whether
> the issues I am facing are actually due to limitations of the 802.11n PC
> card I am using. Unfortunately, the card has no online support.

I'm not aware of any special limits like that, i.e., any AR5416-based
card should be able to work in AP mode and send out Beacon frames.

> Otherwise, I am correctly configuring hostapd on A to run in master mode.
> After running hostapd, running iwconfig on A indicates that it is in master
> mode. The only problem is that there is no beacon activity. I would
> appreciate any insight on what the problem could be.

Please verify that the driver is seeing software beacon alert (SWBA)
interrupts when hostapd is running. There is a counter for this which is
available in debugfs, e.g., in the following file
/sys/kernel/debug/ieee80211/phy0/ath9k/interrupts

The SWBA counter should be increasing by one for every Beacon frame sent
out.

--
Jouni Malinen                                            PGP id EFC895FA

On Fri, Feb 11, 2011 at 5:32 PM, Lara Deek <laradeek at cs.ucsb.edu> wrote:
> Hi,
> I was able to figure out one of my problems. The devices in master mode
> using hostapd now transmit periodic beacon messages. I followed the
> directions of setting up hostapd to the dot, and that worked out. I am not
> sure which part made the difference. Here are the links for whomever might
> have the same
> problem: http://acx100.erley.org/stable.html, http://www.robert-heyward.com/rjh/?page_id=12
> However, I still have the problem that the sniffer (monitor interface)
> running on the same device that is running hostapd in master mode does not
> capture beacon messages. I had two devices, with the same hostapd
> configuration and PC card, run on the same channel, and they wouldn't
> capture each others beacon messages. I had another device with a different
> PC card run in monitor mode, and it did receive beacon messages from the
> mentioned two devices.
> I then ran one of the devices with only a monitoring interface, and it was
> able to capture beacon messages from the other. Why is it that the monitor
> interface stops capturing beacon messages when hostapd (i.e. another
> interface in master/AP mode) is running on the same machine?
> I would greatly appreciate any insight.
> Thank you for your time,
> Lara
>
> On Wed, Feb 9, 2011 at 3:19 PM, Lara Deek <laradeek at cs.ucsb.edu> wrote:
>>
>> Thank you for your reply Jouni.
>>
>>>
>>> Date: Sun, 6 Feb 2011 13:13:12 +0200
>>> From: Jouni Malinen <j at w1.fi>
>>> Subject: Re: No beacon activity
>>> To: hostap at lists.shmoo.com
>>>
>>> On Thu, Feb 03, 2011 at 10:53:50AM -0800, Lara Deek wrote:
>>> > 1) I am running a sniffer on the same machine A that is running
>>> > hostapd. The
>>> > sniffer does not capture beacon messages (only captures probe request
>>> > and
>>> > response packets, both broadcast and unicast). I ran a sniffer from
>>> > another
>>> > machine B (with a different card) in monitor mode, and B does in fact
>>> > capture beacon messages (but never from A). Is there any reason why I
>>> > do not
>>> > sniff beacon frames on A? How can I fix this?
>>>
>>> The actual Beacon frame transmission is not done by mac80211 and there
>>> is no mechanism for the driver to indicate that a Beacon frame was
>>> transmitted since this is not normally needed for anything. What would
>>> you be using the Beacon frames for in the local sniffer?
>>>
>>
>> The beacons I would like machine A to capture are those of its neighboring
>> APs, to identify which APs can potentially conflict with it if they are on
>> the same channel. A does not capture any beacons, but only captures probe
>> request (broadcast) and response messages.
>>
>>>
>>> > 2) I understand that hostapd only configures mac80211 with a template
>>> > and
>>> > beacon interval, but does not actually send beacons. Is enabling beacon
>>> > transmission related to the firmware or driver? I have an AirMagnet
>>> > C1060 PC
>>> > card with an an Atheros, ath9k support, chipset that is not sending
>>> > beacon
>>> > messages. How should enable beacon transmission?
>>>
>>> The driver is responsible for configuring Beacon frame transmissions.
>>>
>>> How exactly did you verify that the card is not sending out Beacon
>>> frames? Have you used another device in monitor mode to check that?
>>>
>>
>> Yes, I have used another device in monitor mode (with an Ubiquiti SRC
>> 802.11a/b/g MCX card with an AR5004 chipset), which captures beacons from
>> sources but never from A. A has an AirMagnet card which has an AR5416+AR5133
>> ath9k supported chipset. I am not sure whether the issues I am facing are
>> actually due to limitations of the 802.11n PC card I am
>> using. Unfortunately, the card has no online support.
>> Otherwise, I am correctly configuring hostapd on A to run in master mode.
>> After running hostapd, running iwconfig on A indicates that it is in master
>> mode. The only problem is that there is no beacon activity. I would
>> appreciate any insight on what the problem could be.
>> Thank you,
>> Lara
>>
>>>
>>> --
>>> Jouni Malinen                                            PGP id EFC895FA
>
>