/usr/include/asio/detail/impl/ is in libasio-dev 1:1.10.8-1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/asio/detail/impl/buffer_sequence_adapter.ipp
/usr/include/asio/detail/impl/descriptor_ops.ipp
/usr/include/asio/detail/impl/dev_poll_reactor.hpp
/usr/include/asio/detail/impl/dev_poll_reactor.ipp
/usr/include/asio/detail/impl/epoll_reactor.hpp
/usr/include/asio/detail/impl/epoll_reactor.ipp
/usr/include/asio/detail/impl/eventfd_select_interrupter.ipp
/usr/include/asio/detail/impl/handler_tracking.ipp
/usr/include/asio/detail/impl/kqueue_reactor.hpp
/usr/include/asio/detail/impl/kqueue_reactor.ipp
/usr/include/asio/detail/impl/pipe_select_interrupter.ipp
/usr/include/asio/detail/impl/posix_event.ipp
/usr/include/asio/detail/impl/posix_mutex.ipp
/usr/include/asio/detail/impl/posix_thread.ipp
/usr/include/asio/detail/impl/posix_tss_ptr.ipp
/usr/include/asio/detail/impl/reactive_descriptor_service.ipp
/usr/include/asio/detail/impl/reactive_serial_port_service.ipp
/usr/include/asio/detail/impl/reactive_socket_service_base.ipp
/usr/include/asio/detail/impl/resolver_service_base.ipp
/usr/include/asio/detail/impl/select_reactor.hpp
/usr/include/asio/detail/impl/select_reactor.ipp
/usr/include/asio/detail/impl/service_registry.hpp
/usr/include/asio/detail/impl/service_registry.ipp
/usr/include/asio/detail/impl/signal_set_service.ipp
/usr/include/asio/detail/impl/socket_ops.ipp
/usr/include/asio/detail/impl/socket_select_interrupter.ipp
/usr/include/asio/detail/impl/strand_service.hpp
/usr/include/asio/detail/impl/strand_service.ipp
/usr/include/asio/detail/impl/task_io_service.hpp
/usr/include/asio/detail/impl/task_io_service.ipp
/usr/include/asio/detail/impl/throw_error.ipp
/usr/include/asio/detail/impl/timer_queue_ptime.ipp
/usr/include/asio/detail/impl/timer_queue_set.ipp
/usr/include/asio/detail/impl/win_event.ipp
/usr/include/asio/detail/impl/win_iocp_handle_service.ipp
/usr/include/asio/detail/impl/win_iocp_io_service.hpp
/usr/include/asio/detail/impl/win_iocp_io_service.ipp
/usr/include/asio/detail/impl/win_iocp_serial_port_service.ipp
/usr/include/asio/detail/impl/win_iocp_socket_service_base.ipp
/usr/include/asio/detail/impl/win_mutex.ipp
/usr/include/asio/detail/impl/win_object_handle_service.ipp
/usr/include/asio/detail/impl/win_static_mutex.ipp
/usr/include/asio/detail/impl/win_thread.ipp
/usr/include/asio/detail/impl/win_tss_ptr.ipp
/usr/include/asio/detail/impl/winrt_ssocket_service_base.ipp
/usr/include/asio/detail/impl/winrt_timer_scheduler.hpp
/usr/include/asio/detail/impl/winrt_timer_scheduler.ipp
/usr/include/asio/detail/impl/winsock_init.ipp