Split traffic between the Linux stack and DPDK application

[Stephen Hemminger]

On Mon, 29 Jan 2024 18:09:28 +0200
Pavel Vazharov <freakpv at gmail.com> wrote:

> Hi there,
> 
> A DPDK can run on top of XDP sockets and use custom XDP program to split
> the traffic between the Linux stack and the DPDK application. This way
> still allows zero copy between the kernel and the DPDK application.
> Is there another zero-copy way to achieve redirecting some part of the
> traffic to the Linux kernel and another to a DPDK application?
> For example, AFAIK I can run the DPDK application and redirect packets from
> inside to the Linux stack via the DPDK KNI functionality but it'll be much
> slower because it'll require packets copying and context switch (if I'm not
> mistaken).
> 
> Regards,
> Pavel.

There is no generic solution. It is possible with some hardware drivers
like Mlx. Intel was working on bifurication as well but seems to have abandoned it.

KNI is no longer part of DPDK, and it did a copy (hidden in kernel).
The problem with zero copy from kernel point of view is how to deal with packet
lifetime.