tcp: refresh tcp_mstamp from timers callbacks

Only the retransmit timer currently refreshes tcp_mstamp

We should do the same for delayed acks and keepalives.

Even if RFC 7323 does not request it, this is consistent to what linux
did in the past, when TS values were based on jiffies.

Fixes: 385e20706fac ("tcp: use tp->tcp_mstamp in output path")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Soheil Hassas Yeganeh <soheil@google.com>
Cc: Mike Maloney <maloney@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by:  Mike Maloney <maloney@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/tcp_timer.c

@@ -264,6 +264,7 @@ void tcp_delack_timer_handler(struct sock *sk)
 			icsk->icsk_ack.pingpong = 0;
 			icsk->icsk_ack.ato      = TCP_ATO_MIN;
 		}
+		tcp_mstamp_refresh(tcp_sk(sk));
 		tcp_send_ack(sk);
 		__NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKS);
 	}
@@ -632,6 +633,7 @@ static void tcp_keepalive_timer (struct timer_list *t)
 		goto out;
 	}
 
+	tcp_mstamp_refresh(tp);
 	if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) {
 		if (tp->linger2 >= 0) {
 			const int tmo = tcp_fin_time(sk) - TCP_TIMEWAIT_LEN;