PS5MC (PPSA99420) stops at start-up on sendfile. It follows FreeBSD 11:
headers, the file range and trailers go to a connected stream socket, the
file offset does not move, a non-blocking socket fails with EAGAIN after
a partial send, and *sbytes reports what was sent. The checks and the
point where *sbytes is written follow kern_sendfile.c.
DariusHQ