m, err := c.fd.Read(buf)
	if err != nil {
		return 0, nil, err
	}
	if m < udpHeaderSize {
		return 0, nil, errors.New("short read reading UDP header")
	}
	buf = buf[:m]

	h, buf := unmarshalUDPHeader(buf)
	n := copy(b, buf)
	*addr = UDPAddr{IP: h.raddr, Port: int(h.rport)}
	return n, addr, nil
}

func (c *UDPConn) readFromAddrPort(b []byte) (int, netip.AddrPort, error) {