On 29.07.21 09:32, François Legal wrote: > Le Mardi, Juillet 27, 2021 18:44 CEST, Jan Kiszka <jan.kis...@siemens.com> a > écrit: > >> On 27.07.21 14:13, François Legal wrote: >>> Le Lundi, Juillet 26, 2021 14:01 CEST, Jan Kiszka <jan.kis...@siemens.com> >>> a écrit: >>> >>>> On 17.05.21 11:44, François Legal via Xenomai wrote: >>>>> This patch enables retrieving, in realtime application, of RTNET enabled >>>>> adapters packet timestamps. >>>>> It uses the linux semantic SO_TIMESTAMPNS, and the linux code to put the >>>>> timestamp in the control_msg structure. >>>>> >>>>> I tested this patch with af_packet sockets only. UDP & TCP might be a >>>>> little bit trickier as many fragment/segments get reassembled in a single >>>>> recvmsg. I believe the linux code I used to put the timestamps in the >>>>> control structure should be OK though. >>>> >>>> One of my question on v1 is still open: How does Linux handle stamping >>>> the context of fragmented UDP and TCP packets? And given that you enable >>>> it for those protocols as well, we should likely test that too. >>> >>> I thought I already gave an answer to this. Sorry. >>> Linux does not handle time stamping of UDP and TCP as far as I understand. >> >> Does Linux return an error when you try to enable this for UDP or TCP >> sockets? > > Alright so I rechecked everything again. Linux does not return an error when > requesting timestamping for UDP or TCP (or any other kind of socket it seems). > > Despite my previous assertion, timestamping is supported for UDP and if I > understood the code correctly, only one timestamp is returned in any case > (the time stamp of the last received datagram). This is done in reassembly > queues, where the queue always keep the timestamp of the last received > datagram, and when doing the reassembly, this last timestamp is reported to > the re created skb. > > For TCP it is definitely not supported. > > So I should modify the patch to make it comply with what linux does I guess ? >
Yes, unless there is any good (RT/Xenomai-specific) reason speaking against alignment, we should do this - least surprise. Jan -- Siemens AG, T RDA IOT Corporate Competence Center Embedded Linux
