/usr/include/ is in libp8-platform-dev 2.1.0.1+dfsg1-1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/p8-platform/
/usr/include/p8-platform/os.h
/usr/include/p8-platform/posix/
/usr/include/p8-platform/posix/os-socket.h
/usr/include/p8-platform/posix/os-threads.h
/usr/include/p8-platform/posix/os-types.h
/usr/include/p8-platform/sockets/
/usr/include/p8-platform/sockets/cdevsocket.h
/usr/include/p8-platform/sockets/socket.h
/usr/include/p8-platform/sockets/tcp.h
/usr/include/p8-platform/threads/
/usr/include/p8-platform/threads/atomics.h
/usr/include/p8-platform/threads/mutex.h
/usr/include/p8-platform/threads/threads.h
/usr/include/p8-platform/util/
/usr/include/p8-platform/util/StdString.h
/usr/include/p8-platform/util/StringUtils.h
/usr/include/p8-platform/util/atomic.h
/usr/include/p8-platform/util/buffer.h
/usr/include/p8-platform/util/timeutils.h
/usr/include/p8-platform/util/util.h