[patch 57/67] TCP: Fix and simplify microsecond rtt sampling

[Greg KH]

-stable review patch.  If anyone has any objections, please let us know.

------------------
From: David Miller <davem@xxxxxxxxxxxxx>

This changes the microsecond RTT sampling so that samples are taken in
the same way that RTT samples are taken for the RTO calculator: on the
last segment acknowledged, and only when the segment hasn't been
retransmitted.

Signed-off-by: John Heffner <jheffner@xxxxxxx>
Acked-by: Stephen Hemminger <shemminger@xxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 net/ipv4/tcp_input.c |   16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

--- linux-2.6.18.orig/net/ipv4/tcp_input.c
+++ linux-2.6.18/net/ipv4/tcp_input.c
@@ -2237,13 +2237,12 @@ static int tcp_tso_acked(struct sock *sk
 	return acked;
 }
 
-static u32 tcp_usrtt(const struct sk_buff *skb)
+static u32 tcp_usrtt(struct timeval *tv)
 {
-	struct timeval tv, now;
+	struct timeval now;
 
 	do_gettimeofday(&now);
-	skb_get_timestamp(skb, &tv);
-	return (now.tv_sec - tv.tv_sec) * 1000000 + (now.tv_usec - tv.tv_usec);
+	return (now.tv_sec - tv->tv_sec) * 1000000 + (now.tv_usec - tv->tv_usec);
 }
 
 /* Remove acknowledged frames from the retransmission queue. */
@@ -2258,6 +2257,7 @@ static int tcp_clean_rtx_queue(struct so
 	u32 pkts_acked = 0;
 	void (*rtt_sample)(struct sock *sk, u32 usrtt)
 		= icsk->icsk_ca_ops->rtt_sample;
+	struct timeval tv;
 
 	while ((skb = skb_peek(&sk->sk_write_queue)) &&
 	       skb != sk->sk_send_head) {
@@ -2306,8 +2306,7 @@ static int tcp_clean_rtx_queue(struct so
 				seq_rtt = -1;
 			} else if (seq_rtt < 0) {
 				seq_rtt = now - scb->when;
-				if (rtt_sample)
-					(*rtt_sample)(sk, tcp_usrtt(skb));
+				skb_get_timestamp(skb, &tv);
 			}
 			if (sacked & TCPCB_SACKED_ACKED)
 				tp->sacked_out -= tcp_skb_pcount(skb);
@@ -2320,8 +2319,7 @@ static int tcp_clean_rtx_queue(struct so
 			}
 		} else if (seq_rtt < 0) {
 			seq_rtt = now - scb->when;
-			if (rtt_sample)
-				(*rtt_sample)(sk, tcp_usrtt(skb));
+			skb_get_timestamp(skb, &tv);
 		}
 		tcp_dec_pcount_approx(&tp->fackets_out, skb);
 		tcp_packets_out_dec(tp, skb);
@@ -2333,6 +2331,8 @@ static int tcp_clean_rtx_queue(struct so
 	if (acked&FLAG_ACKED) {
 		tcp_ack_update_rtt(sk, acked, seq_rtt);
 		tcp_ack_packets_out(sk, tp);
+		if (rtt_sample && !(acked & FLAG_RETRANS_DATA_ACKED))
+			(*rtt_sample)(sk, tcp_usrtt(&tv));
 
 		if (icsk->icsk_ca_ops->pkts_acked)
 			icsk->icsk_ca_ops->pkts_acked(sk, pkts_acked);

--
-
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