/usr/share/common-lisp/source/usocket/ is in cl-usocket 0.6.3.2-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/common-lisp/source/usocket/backend/
/usr/share/common-lisp/source/usocket/backend/abcl.lisp
/usr/share/common-lisp/source/usocket/backend/allegro.lisp
/usr/share/common-lisp/source/usocket/backend/clisp.lisp
/usr/share/common-lisp/source/usocket/backend/clozure.lisp
/usr/share/common-lisp/source/usocket/backend/cmucl.lisp
/usr/share/common-lisp/source/usocket/backend/ecl.lisp
/usr/share/common-lisp/source/usocket/backend/lispworks.lisp
/usr/share/common-lisp/source/usocket/backend/mcl.lisp
/usr/share/common-lisp/source/usocket/backend/mocl.lisp
/usr/share/common-lisp/source/usocket/backend/openmcl.lisp
/usr/share/common-lisp/source/usocket/backend/sbcl.lisp
/usr/share/common-lisp/source/usocket/backend/scl.lisp
/usr/share/common-lisp/source/usocket/condition.lisp
/usr/share/common-lisp/source/usocket/option.lisp
/usr/share/common-lisp/source/usocket/package.lisp
/usr/share/common-lisp/source/usocket/server.lisp
/usr/share/common-lisp/source/usocket/test/
/usr/share/common-lisp/source/usocket/test/package.lisp
/usr/share/common-lisp/source/usocket/test/test-condition.lisp
/usr/share/common-lisp/source/usocket/test/test-datagram.lisp
/usr/share/common-lisp/source/usocket/test/test-usocket.lisp
/usr/share/common-lisp/source/usocket/test/wait-for-input.lisp
/usr/share/common-lisp/source/usocket/usocket.asd
/usr/share/common-lisp/source/usocket/usocket.lisp
/usr/share/common-lisp/source/usocket/vendor/
/usr/share/common-lisp/source/usocket/vendor/OpenTransportUDP.lisp
/usr/share/common-lisp/source/usocket/vendor/kqueue.lisp
/usr/share/common-lisp/source/usocket/vendor/spawn-thread.lisp
/usr/share/common-lisp/source/usocket/vendor/split-sequence.lisp