[IPV4]: Make tcp_input_metrics() get minimum RTO via tcp_rto_min()

tcp_input_metrics() refers to the built-time constant TCP_RTO_MIN
regardless of configured minimum RTO with iproute2.
Signed-off-by: NSatoru SATOH <satoru.satoh@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/tcp_input.c

@@ -923,7 +923,7 @@ static void tcp_init_metrics(struct sock *sk)
 	}
 	if (dst_metric(dst, RTAX_RTTVAR) > tp->mdev) {
 		tp->mdev = dst_metric(dst, RTAX_RTTVAR);
-		tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN);
+		tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk));
 	}
 	tcp_set_rto(sk);
 	tcp_bound_rto(sk);