net: tcp: allow tcp_timewait_sock to validate skbs before handing to device

Provide a callback to validate skb's originating from tcp timewait
socks before passing to the device layer. Full socks have a
sk_validate_xmit_skb member for checking that a device is capable of
performing offloads required for transmitting an skb. With psp, tcp
timewait socks will inherit the crypto state from their corresponding
full socks. Any ACKs or RSTs that originate from a tcp timewait sock
carrying psp state should be psp encapsulated.

Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Daniel Zahka <daniel.zahka@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250917000954.859376-8-daniel.zahka@gmail.com


Signed-off-by: Paolo Abeni <pabeni@redhat.com>