/usr/include/ is in libpsocksxx-dev 1.1.0-1.2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/psocksxx/
/usr/include/psocksxx/udpnsockstream.h
/usr/include/psocksxx/tcpnsockstream.h
/usr/include/psocksxx/nsockstream.h
/usr/include/psocksxx/lsockstream.h
/usr/include/psocksxx/iosockstream.h
/usr/include/psocksxx/osockstream.h
/usr/include/psocksxx/isockstream.h
/usr/include/psocksxx/iosocks.h
/usr/include/psocksxx/sockstreambuf.h
/usr/include/psocksxx/nsockaddr.h
/usr/include/psocksxx/lsockaddr.h
/usr/include/psocksxx/sockaddr.h
/usr/include/psocksxx/socktimeoutexception.h
/usr/include/psocksxx/sockexception.h