/usr/src/xtables-addons-3.0/extensions/pknock/ is in xtables-addons-dkms 3.0-0.1.
This file is owned by root:root, with mode 0o755.
..
/usr/src/xtables-addons-3.0/extensions/pknock/Kbuild
/usr/src/xtables-addons-3.0/extensions/pknock/Makefile
/usr/src/xtables-addons-3.0/extensions/pknock/Makefile.am
/usr/src/xtables-addons-3.0/extensions/pknock/Makefile.in
/usr/src/xtables-addons-3.0/extensions/pknock/Mbuild
/usr/src/xtables-addons-3.0/extensions/pknock/gen_hmac.py
/usr/src/xtables-addons-3.0/extensions/pknock/knock.sh
/usr/src/xtables-addons-3.0/extensions/pknock/libxt_pknock.c
/usr/src/xtables-addons-3.0/extensions/pknock/libxt_pknock.man
/usr/src/xtables-addons-3.0/extensions/pknock/pknlusr.c
/usr/src/xtables-addons-3.0/extensions/pknock/xt_pknock.c
/usr/src/xtables-addons-3.0/extensions/pknock/xt_pknock.h