/lib/udev/rules.d/xen-backend.rules is in xen-utils-common 4.1.4-3+deb7u9.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 | SUBSYSTEM=="xen-backend", KERNEL=="tap*", RUN+="/etc/xen/scripts/blktap $env{ACTION}"
SUBSYSTEM=="xen-backend", KERNEL=="vbd*", RUN+="/etc/xen/scripts/block $env{ACTION}"
SUBSYSTEM=="xen-backend", KERNEL=="vtpm*", RUN+="/etc/xen/scripts/vtpm $env{ACTION}"
SUBSYSTEM=="xen-backend", KERNEL=="vif2-*", RUN+="/etc/xen/scripts/vif2 $env{ACTION}"
SUBSYSTEM=="xen-backend", KERNEL=="vif-*", ACTION=="online", RUN+="/etc/xen/scripts/vif-setup online type_if=vif"
SUBSYSTEM=="xen-backend", KERNEL=="vif-*", ACTION=="offline", RUN+="/etc/xen/scripts/vif-setup offline type_if=vif"
SUBSYSTEM=="xen-backend", KERNEL=="vscsi*", RUN+="/etc/xen/scripts/vscsi $env{ACTION}"
SUBSYSTEM=="xen-backend", ACTION=="remove", RUN+="/etc/xen/scripts/xen-hotplug-cleanup"
SUBSYSTEM=="net", KERNEL=="vif*-emu", ACTION=="add", RUN+="/etc/xen/scripts/vif-setup $env{ACTION} type_if=tap"
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