As the ecosystem around P4 continues to develop, more and more programmable targets are emerging. The P4 compiler has already support for the next-generation Linux datapath such as eBPF/XDP. However, in certain settings, it is necessary to extend user-space packet processing applications at run time. This can be achieved by using the user-space BPF (uBPF) Virtual Machine, which is a re-implementation of in-kernel eBPF VM, and provides a user-space execution environment that is extensible at runtime.
More information is available in a blog post by Tomasz Osiński.
