Cleanup restores the system network configuration to its original state in case the Tailscale daemon terminated without closing the router.

New returns a new Router for the current platform, using the provided tun device.

NewFake returns a Router that does nothing when called and always returns nil errors.

CallbackRouter is an implementation of both Router and dns.OSConfigurator.

Config is the subset of Tailscale configuration that is relevant to the OS's network stack.

Router is responsible for managing the system network stack.