[nrf fromtree] net: tcp: Reschedule FIN timer when entering FIN state

The FIN timer was not set when we entered the FIN_WAIT_1 state.
This could cause issues if we did not receive proper packets
from peer. With this fix, the connection is always terminated
even if peer does not respond.

Signed-off-by: Robert Lubos <[email protected]>
Signed-off-by: Jukka Rissanen <[email protected]>
(cherry picked from commit b214207)

Author: jukkar

subsys/net/ip/tcp.c

@@ -2681,6 +2681,10 @@ static enum net_verdict tcp_in(struct tcp *conn, struct net_pkt *pkt)
 				tcp_send_timer_cancel(conn);
 				next = TCP_FIN_WAIT_1;
 
+				k_work_reschedule_for_queue(&tcp_work_q,
+							    &conn->fin_timer,
+							    FIN_TIMEOUT);
+
 				tcp_out(conn, FIN | ACK);
 				conn_seq(conn, + 1);
 				verdict = NET_OK;