Re: DPDK Pdump tool is not able to attach to DPDK test pmd primary application

[Stephen Hemminger <stephen@networkplumber.org>]

On Wed, 14 Feb 2024 22:44:46 +0000
Sameer Vaze <svaze@qti.qualcomm.com> wrote:

> Hey Folks,
> 
> I see the following message when I attempt to attach pdump to the testpmd sample application:
> 
> Pdump output:
> EAL: Failed to hotplug add device
> EAL: Error - exiting with code: 1
>   Cause: vdev creation failed:create_mp_ring_vdev:695
> 
> Testpmd output:
> Reached maximum number of Ethernet ports
> EAL: Driver cannot attach the device (net_pcap_rx_0)
> EAL: Failed to hotplug add device on primary
> 
> The primary and secondary applications were run using the following commands:
> 
> Primary: sudo ./dpdk-testpmd --proc-type=primary --file-prefix=test -d /path/to/pmd
> Secondary: sudo ./dpdk-pdump --proc-type=secondary --file-prefix=test -d /path/to/pmd -- --pdump 'port=0,queue=1,rx-dev=./rx.pcap,tx-dev=./tx.pcap'
> 
> DPDK version: 22.11.1
> 
> Is this a known issue? Is there any known fix for this?
> 
> Thanks
> Sameer Vaze

pdump and dumpcap can't work where the actual data transmit/receive is done in secondary
process. The problem is in the design using callbacks and the way the pdump/dumpcap is
initialized.

The pdump/dumpcap works as an additional secondary process.
At startup pdump/dumpcap communicates with primary process to enable callbacks on rx/tx but
these work only in the primary process. In secondary process, there are no rx/tx callbacks.