iwlwifi: OFMDA Sniffer not capturing actual data

iwlwifi: OFMDA Sniffer not capturing actual data

[Milo Garcia]

Hi buddies,

I am using the Intel AX200 to capture OFDMA DL traffic. I used the
next command to sniff 11ax OFDMA packets
echo [AID] [MAC AP] > /sys/kernel/debug/iwlwifi/*/iwlmvm/he_sniffer_params

I am able to see HE_MU packets but they don't contain the actual data
in the RUs. Wireshark says "NOT CAPTURED BY CAPTURE SOFTWARE"

Is it possible to get the possible RU Data from iwlwifi?

Regards, Milo Garcia

Re: iwlwifi: OFMDA Sniffer not capturing actual data

[Johannes Berg]

On Mon, 2021-08-16 at 17:34 +0200, Milo Garcia wrote:
> 
> I am able to see HE_MU packets but they don't contain the actual data
> in the RUs. Wireshark says "NOT CAPTURED BY CAPTURE SOFTWARE"

That *should* work, for the AID you specified.

What exactly are you seeing?

johannes

Re: iwlwifi: OFMDA Sniffer not capturing actual data

[Milo Garcia]

> What exactly are you seeing?
https://imgur.com/N7DdDS3

I was expecting to see the data in the RU but Wireshark only shows
packet length of 86 bytes

El lun, 16 ago 2021 a las 17:44, Johannes Berg
(<johannes@sipsolutions.net>) escribió:
>
> On Mon, 2021-08-16 at 17:34 +0200, Milo Garcia wrote:
> >
> > I am able to see HE_MU packets but they don't contain the actual data
> > in the RUs. Wireshark says "NOT CAPTURED BY CAPTURE SOFTWARE"
>
> That *should* work, for the AID you specified.
>
> What exactly are you seeing?
>
> johannes
>

Re: iwlwifi: OFMDA Sniffer not capturing actual data

[Johannes Berg]

On Mon, 2021-08-16 at 18:04 +0200, Milo Garcia wrote:
> > What exactly are you seeing?
> https://imgur.com/N7DdDS3
> 
> I was expecting to see the data in the RU but Wireshark only shows
> packet length of 86 bytes

oh, but that's not the *data*, that's the RU allocation information.

Looks like we don't report that for 0-length PSDU, not sure, probably
the DSP doesn't propagate it if there was nothing for the AID you
configured, or so.

johannes

Re: iwlwifi: OFMDA Sniffer not capturing actual data

[Milo Garcia]

> oh, but that's not the *data*, that's the RU allocation information.
>
> Looks like we don't report that for 0-length PSDU, not sure, probably
> the DSP doesn't propagate it if there was nothing for the AID you
> configured, or so.
ok, so if that is the allocation and we are getting 0-length PSDU,
then it means that I am sniffing with the wrong AID?

In practice then I will just need to select an AID to which data is
being sent and then I will be able to see the HE_MU Data?

My goal is to see DL OFDMA data in wireshark. Thank a lot for your help :D

El lun, 16 ago 2021 a las 18:10, Johannes Berg
(<johannes@sipsolutions.net>) escribió:
>
> On Mon, 2021-08-16 at 18:04 +0200, Milo Garcia wrote:
> > > What exactly are you seeing?
> > https://imgur.com/N7DdDS3
> >
> > I was expecting to see the data in the RU but Wireshark only shows
> > packet length of 86 bytes
>
> oh, but that's not the *data*, that's the RU allocation information.
>
> Looks like we don't report that for 0-length PSDU, not sure, probably
> the DSP doesn't propagate it if there was nothing for the AID you
> configured, or so.
>
> johannes
>

Re: iwlwifi: OFMDA Sniffer not capturing actual data

[Johannes Berg]

On Mon, 2021-08-16 at 18:26 +0200, Milo Garcia wrote:
> > oh, but that's not the *data*, that's the RU allocation information.
> > 
> > Looks like we don't report that for 0-length PSDU, not sure,
> > probably
> > the DSP doesn't propagate it if there was nothing for the AID you
> > configured, or so.
> ok, so if that is the allocation and we are getting 0-length PSDU,
> then it means that I am sniffing with the wrong AID?
> 
> In practice then I will just need to select an AID to which data is
> being sent and then I will be able to see the HE_MU Data?

I think so. And also the data that was sent to that AID.

All only as long as the NIC is actually in sniffer mode, of course.

johannes