On Sun. 26 Jun 2022 at 19:57, Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx> wrote: > On 26.06.2022 12:31:59, Oliver Hartkopp wrote: > > > What I was thinking is that tools such as tcpdump are able to get TX > > > packets of ethernet interfaces even if not normally visible (because > > > contrary to CAN, there is no default loopback). I was wondering if the > > > same could be done with error queues, but as you can guess my research > > > did lead anywhere. I also guess there is no official support but then, > > > I am wondering how hard it would be to hack the error queues to expose > > > them to the privileged processes. > > > > I wonder whether error queues are the right mechanism or if control messages > > needed to be extended here - like for (hardware) rx timestamps. > > I think error queues are the official way for TX timestamps. Nonetheless > tcpdump support for TX timestamps would be interesting. Yes, the error queues are the only official method. If we were to do it in a non standard way, the easiest would be to put it in the second entry of struct scm_timestamping which used to hold SOF_TIMESTAMPING_SYS_HARDWARE but which is now deprecated. c.f. https://docs.kernel.org/networking/timestamping.html#timestamp-reporting Yours sincerely, Vincent Mailhol
