The sdl_nlen member will be 5 and the sdl_alen member will be 8. This requires 21 bytes, so the size is rounded up to 24 bytes (p.89 of TCPv2), assuming a 32-bit architecture.
18.2
The kernel's response is never sent to this socket. This socket option determines whether the kernel sends its reply to the sending process, as discussed on pp.649 “650 of TCPv2. It defaults to ON, since most processes want replies. But, disabling the option prevents replies from being sent to the sender.
