/usr/lib/x86_64-linux-gnu/libjacknet.so.0 is in libjack-jackd2-0 1.9.8~dfsg.4+20120529git007cdc37-5.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libjacknet.so.0.1.0
/usr/lib/x86_64-linux-gnu/libjacknet.so.0.1.0