/usr/lib/x86_64-linux-gnu/lua/5.1/rrd.so is in lua-rrd 1.7.0-1build1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/lua/5.1/../../liblua5.1-rrd.so.0.0.0
/usr/lib/x86_64-linux-gnu/lua/5.1/../../liblua5.1-rrd.so.0.0.0