How to configure monitor devices for HT80?

How to configure monitor devices for HT80?

[Ben Greear]

I'm trying to sniff using a monitor interface on ath10k, on channel 36.

I'm seeing lots of packets, but not all that the AP claims to be sending
(when sniffing vap0).  I am not not certain the monitor interface is
using HT80 or not.

Anyone have a working example of the proper iw commands to create
a monitor interface on channel 36 for HT80?

Thanks,
Ben

-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com

Re: How to configure monitor devices for HT80?

[Johannes Berg]

On Mon, 2014-05-05 at 12:06 -0700, Ben Greear wrote:
> I'm trying to sniff using a monitor interface on ath10k, on channel 36.
> 
> I'm seeing lots of packets, but not all that the AP claims to be sending
> (when sniffing vap0).  I am not not certain the monitor interface is
> using HT80 or not.
> 
> Anyone have a working example of the proper iw commands to create
> a monitor interface on channel 36 for HT80?

...
iw wlan0 set freq 5180 80 5210

johannes

Re: How to configure monitor devices for HT80?

[Ben Greear]

On 05/05/2014 12:22 PM, Johannes Berg wrote:
> On Mon, 2014-05-05 at 12:06 -0700, Ben Greear wrote:
>> I'm trying to sniff using a monitor interface on ath10k, on channel 36.
>>
>> I'm seeing lots of packets, but not all that the AP claims to be sending
>> (when sniffing vap0).  I am not not certain the monitor interface is
>> using HT80 or not.
>>
>> Anyone have a working example of the proper iw commands to create
>> a monitor interface on channel 36 for HT80?
> 
> ...
> iw wlan0 set freq 5180 80 5210

Thanks, this works at least most of the time.

But, it seems if I have another vif up, it will fail, even if that
vif is (should be?) using the exact same frequency.

./local/sbin/iw phy wiphy0 interface add moni0 type monitor
./local/sbin/ip link set dev moni0 up
./local/sbin/iw dev moni0 set freq 5180 80 5210
-> yields error:
command failed: Device or resource busy (-16)


I'm not absolutely certain the monitor device still works
properly or not, but it at least mostly works.

Thanks,
Ben

-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com

Re: How to configure monitor devices for HT80?

[Johannes Berg]

On Tue, 2014-05-06 at 10:56 -0700, Ben Greear wrote:

> But, it seems if I have another vif up, it will fail, even if that
> vif is (should be?) using the exact same frequency.
> 
> ./local/sbin/iw phy wiphy0 interface add moni0 type monitor
> ./local/sbin/ip link set dev moni0 up
> ./local/sbin/iw dev moni0 set freq 5180 80 5210
> -> yields error:
> command failed: Device or resource busy (-16)

You can't set the monitor frequency if you're using the hardware for
something else already. We could potentially allow that if the chandefs
are compatible, but that's getting into really messy territory so I'm
not sure I want to go there - if for example the other interface
switches bandwidth or even channel the monitor would usually simply
follow around.

johannes

Re: How to configure monitor devices for HT80?

[Ben Greear]

On 05/07/2014 02:01 AM, Johannes Berg wrote:
> On Tue, 2014-05-06 at 10:56 -0700, Ben Greear wrote:
>
>> But, it seems if I have another vif up, it will fail, even if that
>> vif is (should be?) using the exact same frequency.
>>
>> ./local/sbin/iw phy wiphy0 interface add moni0 type monitor
>> ./local/sbin/ip link set dev moni0 up
>> ./local/sbin/iw dev moni0 set freq 5180 80 5210
>> -> yields error:
>> command failed: Device or resource busy (-16)
>
> You can't set the monitor frequency if you're using the hardware for
> something else already. We could potentially allow that if the chandefs
> are compatible, but that's getting into really messy territory so I'm
> not sure I want to go there - if for example the other interface
> switches bandwidth or even channel the monitor would usually simply
> follow around.

Ok, as long as I know why then the failure is not so concerning.

Another question:  if I create a monitor interface first, and
successfully set it's frequency, what do I need to do to allow
a station to move to a different frequency later?

Thanks,
Ben

>
> johannes
>

-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com

Re: How to configure monitor devices for HT80?

[Johannes Berg]

On Wed, 2014-05-07 at 05:41 -0700, Ben Greear wrote:

> Another question:  if I create a monitor interface first, and
> successfully set it's frequency, what do I need to do to allow
> a station to move to a different frequency later?

Nothing - the monitor frequency is always just a hint that you want, if
you start doing other things it gets lost automatically.

johannes