/usr/include/c/sidl_rmi_UnknownHostException.h is in libsidl-dev 1.4.0.dfsg-8.2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/include/c/../sidl_rmi_UnknownHostException.h
/usr/include/c/../sidl_rmi_UnknownHostException.h