/lib/udev/rules.d/40-libvirt-bin.rules is in libvirt-bin 0.9.8-2ubuntu17.23.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | # cat /etc/udev/rules.d/61-virbr-querier.rules
ACTION=="add", SUBSYSTEM=="net", RUN+="/lib/udev/libvirt_vnet_querier_enable"
|