[dpdk-dev] mlx5 & pdump: convert HW timestamps to nanoseconds

[PATRICK KEROULAS <patrick.keroulas@radio-canada.ca>]

Hello,

I'm trying to build an accurate capture device based on Mellanox
Connect-X5 with following requirements:
- capture every incoming packets with hardware timestamps
- output: pcap with timestamps in nanoseconds
My problem is that the packets forwarded to `dpdk-pdump` carry raw
timestamps from NIC clock.

mlx5 part of libibverbs includes a ts-to-ns converter which takes the
instantaneous clock info. It's unused in dpdk so far. I've tested it in the
device/port init routine and the result looks reliable. Since this approach
looks very simple, compared to the time sync mechanism, I'm trying to
integrate.

The conversion should occur in the primary process (testpmd) I suppose.
1) The needed clock info derives from ethernet device. Is it possible to
   access that struct from a rx callback?
2) how to attach the nanosecond to mbuf so that `pdump` catches it?
   (workaround: copy `mbuf->udata64` in forwarded packets.)
3) any other idea?

Regards,

Patrick