Userspace networking is pretty common. The chair of the IETF even wrote one: https://github.com/NTAP/quant https://github.com/NTAP/quant "Quant uses the warpco

Userspace networking is pretty common. The chair of the IETF even wrote one: https://github.com/NTAP/quant https://github.com/NTAP/quant "Quant uses the warpcore zero-copy userspace UDP/IP stack, which in addition to running on on top of the standard Socket API has support for the netmap fast packet I/O framework, as well as the Particle and RIOT IoT stacks. Quant hence supports traditional POSIX platforms (Linux, MacOS, FreeBSD, etc.) as well as embedded systems."