tcp: Fix tcp_prequeue() to get correct rto_min value

tcp_prequeue() refers to the constant value (TCP_RTO_MIN) regardless of
the actual value might be tuned. The following patches fix this and make
tcp_prequeue get the actual value returns from tcp_rto_min().
Signed-off-by: Satoru SATOH <satoru.satoh@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/tcp.h

@@ -41,6 +41,7 @@
 #include <net/ip.h>
 #include <net/tcp_states.h>
 #include <net/inet_ecn.h>
+#include <net/dst.h>
 
 #include <linux/seq_file.h>
 
@@ -530,6 +531,17 @@ static inline void tcp_fast_path_check(struct sock *sk)
 		tcp_fast_path_on(tp);
 }
 
+/* Compute the actual rto_min value */
+static inline u32 tcp_rto_min(struct sock *sk)
+{
+	struct dst_entry *dst = __sk_dst_get(sk);
+	u32 rto_min = TCP_RTO_MIN;
+
+	if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
+		rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
+	return rto_min;
+}
+
 /* Compute the actual receive window we are currently advertising.
  * Rcv_nxt can be after the window if our peer push more data
  * than the offered window.
@@ -895,7 +907,7 @@ static inline int tcp_prequeue(struct sock *sk, struct sk_buff *skb)
 			wake_up_interruptible(sk->sk_sleep);
 			if (!inet_csk_ack_scheduled(sk))
 				inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
-						          (3 * TCP_RTO_MIN) / 4,
+						          (3 * tcp_rto_min(sk)) / 4,
 							  TCP_RTO_MAX);
 		}
 		return 1;

net/ipv4/tcp_input.c

@@ -597,16 +597,6 @@ static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb)
 		tcp_grow_window(sk, skb);
 }
 
-static u32 tcp_rto_min(struct sock *sk)
-{
-	struct dst_entry *dst = __sk_dst_get(sk);
-	u32 rto_min = TCP_RTO_MIN;
-
-	if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
-		rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
-	return rto_min;
-}
-
 /* Called to compute a smoothed rtt estimate. The data fed to this
  * routine either comes from timestamps, or from segments that were
  * known _not_ to have been retransmitted [see Karn/Partridge