After reading both nspwan and machinectl documentation, I couldn't find instructions on how to limit network bandwidth on a nspawn container through nspawn itself (or machinectl).
Doesn nspawn and/or machinectl offer such an option and, if not, is it a problem to use external tools like "tc" (traffic control) or wondershaper? If tc or wondershaper aren't a good option, what do you recommend? Paulo Coghi