net: tcp2: Ack any data received in FIN_WAIT_1 state

If we receive any data in FIN_WAIT_1, then ack it even if we
are discarding it.

Fixes #33986

Signed-off-by: Jukka Rissanen <[email protected]>
Signed-off-by: Jim Paris <[email protected]>

Author: jukkar

subsys/net/ip/tcp2.c

@@ -1893,6 +1893,9 @@ static void tcp_in(struct tcp *conn, struct net_pkt *pkt)
 		do_close = true;
 		break;
 	case TCP_FIN_WAIT_1:
+		/* Acknowledge but drop any data */
+		conn_ack(conn, + len);
+
 		if (th && FL(&fl, ==, (FIN | ACK), th_seq(th) == conn->ack)) {
 			tcp_send_timer_cancel(conn);
 			conn_ack(conn, + 1);