Monitor mode TX retry reporting

[Jussi Haakana]

On 29 July 2015 at 8:23, Michal Kazior <michal.kazior at tieto.com> wrote:
> On 28 July 2015 at 14:21, Jussi Haakana <jussi.haakana at 7signal.com> wrote:
> > Hi,
> >
> > I have the following test setup:
> > - 1 interface in managed mode
> > - 1 interface in monitor mode
> > - attach to AP
> > - start tcpdump on monitor interface
> > - upload e.g. 200MB by using managed mode interface
> > - check captured frames
> >
> > For some reason, on TX frames, I cannot see a single frame that has
> retry bit set
> > on frame control of 802.11 headers. For RX, retries seem to be reported
> normally.
> > I'd say that it is unlikely that retransmissions do not happen with
> 200MB payload?
> > Any ideas what could be causing this?
> 
> You can't sniff your own retransmissions because they are performed by
> device and tcpdump sees only a single frame that was submitted through
> the networking stack.
> 
> I guess you could emulate this by posting skbuff copies as Rx based on
> tx retry series (which aren't available now due to ath10k firmware
> limitation). However I'm not aware if there's any driver that does
> that.

Ok, understood. I've verified that sniffing TX retransmissions is possible with
ath9k driver, but it seems not to be the case with ath10k.

> If you want to sniff your client retransmissions you'll have to use a
> separate device to act as a sniffer or listen on the other endpoint
> (i.e. AP).
> 
> 
> Michał

Thanks,
Jussi