/usr/include/pion/ is in libpion-dev 5.0.5+dfsg-1+b1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/pion/admin_rights.hpp
/usr/include/pion/algorithm.hpp
/usr/include/pion/config.hpp
/usr/include/pion/error.hpp
/usr/include/pion/hash_map.hpp
/usr/include/pion/http/
/usr/include/pion/http/auth.hpp
/usr/include/pion/http/basic_auth.hpp
/usr/include/pion/http/cookie_auth.hpp
/usr/include/pion/http/message.hpp
/usr/include/pion/http/parser.hpp
/usr/include/pion/http/plugin_server.hpp
/usr/include/pion/http/plugin_service.hpp
/usr/include/pion/http/reader.hpp
/usr/include/pion/http/request.hpp
/usr/include/pion/http/request_reader.hpp
/usr/include/pion/http/request_writer.hpp
/usr/include/pion/http/response.hpp
/usr/include/pion/http/response_reader.hpp
/usr/include/pion/http/response_writer.hpp
/usr/include/pion/http/server.hpp
/usr/include/pion/http/types.hpp
/usr/include/pion/http/writer.hpp
/usr/include/pion/logger.hpp
/usr/include/pion/plugin.hpp
/usr/include/pion/plugin_manager.hpp
/usr/include/pion/plugins/
/usr/include/pion/plugins/AllowNothingService.hpp
/usr/include/pion/plugins/CookieService.hpp
/usr/include/pion/plugins/EchoService.hpp
/usr/include/pion/plugins/FileService.hpp
/usr/include/pion/plugins/HelloService.hpp
/usr/include/pion/plugins/LogService.hpp
/usr/include/pion/process.hpp
/usr/include/pion/scheduler.hpp
/usr/include/pion/spdy/
/usr/include/pion/spdy/decompressor.hpp
/usr/include/pion/spdy/parser.hpp
/usr/include/pion/spdy/types.hpp
/usr/include/pion/tcp/
/usr/include/pion/tcp/connection.hpp
/usr/include/pion/tcp/server.hpp
/usr/include/pion/tcp/stream.hpp
/usr/include/pion/tcp/timer.hpp
/usr/include/pion/test/
/usr/include/pion/test/unit_test.hpp
/usr/include/pion/user.hpp