/lib/x86_64-linux-gnu/libnsl.so.1 is in libc6 2.23-0ubuntu10.
This file is owned by root:root, with mode 0o777.
It is a symlink to /lib/x86_64-linux-gnu/libnsl-2.23.so
/lib/x86_64-linux-gnu/libnsl-2.23.so