Forwards udev events into a given network namespace. You must provide the path
to a file suitable for use with setns(2), e.g.
ip netns add my-namespace
udevfw /run/netns/my-namespace
udevfw must be run as root, or with CAP_NET_ADMIN rights.
This program is somewhat hacky because systemd's libudev library does not
export the necessary function to send udev messages. As a result, it relies
upon the specific implementation details of the udev message format.