`sendto()` and `recvfrom()` are not currently special-cased for AF_UNIX sockets, and they work correctly. They flow to the same functions as `send()` and `recv()` respectively, specifically `WS2_sendto()` and `WS2_recv_base()`.
They don't work correctly if there's an address passed, though. Unless that address is ignored—for both functions—when TCP sockets are used, but we don't have tests for this, and if it is the case then that address conversion code is also unused and hence should just be removed.