veth interface and testpmd

Question

I am trying to see if we can attach linux veth interface to testpmd app

https://doc.dpdk.org/guides/testpmd_app_ug/testpmd_funcs.html#port-functions

From the above link, it shows how it to attach a NIC to testpmd by moving NIC to a poll mode driver and there by it allowd the NIC to attach to testpmd app.

Similarly, do we have a driver that support poll mode for veth ? Please let me know iof anyody had tried this

Answer 1

There are multiple questions and a few assumptions that needs correction embedded to the current query. hence please find the answers to the same below

[Question-1] do we have a driver that support poll mode for veth ?

[Answer] Currently no, there is no Poll Mode Driver (PMD). Which uses LINUX veth interface. Please refer to current available PMD for both Physical and Virtual Interface

[Question-2] https://doc.dpdk.org/guides/testpmd_app_ug/testpmd_funcs.html#port-functions. From the above link, it shows how it to attach a NIC to testpmd by moving NIC to a poll mode driver and there by it allowd the NIC to attach to testpmd app`

[Answer] DPDK is not supported all vendor NIC, one has to implement the Polling Library using uio driver for physical. Here are the list of NIC which are supported via user space driver.

For Physical NIC that are not supported there are 1 known alternative method to attach and use. Use of PCAP based PMD to act as port representation via PCAP PMD. Using the virtual device intialization via eal command line argument --vdev 'net_pcap0,iface=<interface name> one can read and write packets to the NIC interface.

With respect to the link shared https://doc.dpdk.org/guides/testpmd_app_ug/testpmd_funcs.html#port-functions, for your requirement it could be port attach net_pcap0,iface=<your kernel interface>. But my recommendation is to start testpmd with ./dpdk-testpmd --no-pci --vdev=net_pcap0,iface=<your kernel interface> -- -i. This will start the testpmd with no PCI device, but virtual PCAP PMD device where PCAP library is used to interface with the kernel NIC port (assumption you have installed libpcap-dev and built dpdk accordingly).

[Question-3] if we can attach linux veth interface to testpmd app

[Answer] At least with DPDK 18.11 LTS, 19.11 LTS, and 20.11 LTS I have used net_pcap PMD to interface with 1 of veth interface (for namespace and dockers).

Note: Since DPDK version, libpcap version, veth steps are not shared; it is hard to know whether you have followed the right steps. Hence my recommendation is to share details next time with new question if you face issue.