/lib/udev/rules.d/68-azure-nm-unmanaged.rules is in walinuxagent 2.2.21+really2.2.20-0ubuntu3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 | # When WALinuxAgent is installed, then don't allow for network-manager
# to manage the interface.
#
ENV{INTERFACE}=="eth[0-9]*", ENV{ID_NET_DRIVER}=="hv_netvsc", ENV{NM_UNMANAGED}="1"
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