Monitor mode TX retry reporting

[Michal Kazior]

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.

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