pyflop creates SSH tunnels using dummy interfaces (so multiple tunnels may use the same port).

This is achieved by adding a dummy interface (pyflopX) with an IPv4 IP in the range 10.10.0.0/24 and SSH to create the actual tunnels.

It might be desired to allow users to bind to restricted ports to make this even more usable. You can either do this system wide:

echo 'net.ipv4.ip_unprivileged_port_start=0' > /etc/sysctl.d/50-unprivileged-ports.conf
sysctl --system

Or just allow SSH to bind to privileged ports:

setcap CAP_NET_BIND_SERVICE=+eip /your/ssh/binary