Configure timestamp source for dpdk-pdump on E810 and DPDK 19.11

[Stephen Hemminger]

On Fri, 6 May 2022 07:46:39 +0000
Mikael R Carlsson <Mikael.R.Carlsson at tietoevry.com> wrote:

> Hi!
> 
> I am using a Intel E810-XXVDA4 and DPDK version 19.11. During troubleshooting we have captures outgoing traffic with dpdk-pdump:
> 
> dpdk-pdump -- --pdump 'port=1,queue=*,tx-dev=/tmp/tx.pcap
> 
> I have opened the pcap-file in wireshark and I can see that some packets are delayed. However, system behavior indicates that the delays I see in the pcap file are not correct, they are too big. My questions is, how is the timestamp on packets in the pcap from dpdk-pdump created, like NIC HW generated, CPU time at disk write etc. or something else? Are there any run-time or build-time options to change the source of the timestamps?
> 
>   / Mikael
> 
> 
> 

The timestamp for packet capture in DPDK is done when packet is queued to
the device. It is not possible with current driver architecture to get
timestamp when/after the packet was transmitted.