QEMU

https://blog.wikichoon.com/2016/01/qemusystem-vs-qemusession.html

Add bridges into /etc/qemu/bridge.conf for unprivileged sessions

There is an option for qemu:///session VMs to use a privileged networking setup, via the setuid qemu-bridge-helper. Basically the host admin sets up a bridge, adds it to a whitelist at /etc/qemu/bridge.conf, then it's available for unprivileged qemu instances. By default on Fedora this contains 'virbr0' which is the default virtual network bridge provided by the system libvirtd instance, and what qemu:///system VMs typically use.