There are 2 repositories under userspace-networking topic.
Libtpa(Transport Protocol Acceleration), a DPDK based userspace TCP stack implementation.
User-Space TCP/IP Stack Implemented in C++20.
seqs: the hottest, most idiomatic userspace TCP/IP implementation on the internet. lwip in go basically
User-space Wireguard gateway allowing sharing network connection from environment where usual routing rules are inaccessible.
Android application to route incoming connections from Wireguard tunnels to device's network
Performance Evaluation of AF_XDP Communication Patterns
Create networks of virtual switches and virtual machines without root privileges
A client-server code to bench-mark dpdk in different configurations
Example to integrate Netronome SmartNICs with userspace driver