[TCP]: Fix and simplify microsecond rtt sampling

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@psc.edu>
Acked-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 85c96631666826ac1057659fe91a025d557fd180..3f884cea14ff439651b876ffce4f351289640681 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2239,13 +2239,12 @@ static int tcp_tso_acked(struct sock *sk, struct sk_buff *skb,
        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. */
@@ -2260,6 +2259,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p)
        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) {
@@ -2308,8 +2308,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p)
                                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);
@@ -2322,8 +2321,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p)
                        }
                } 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);
@@ -2335,6 +2333,8 @@ static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p)
        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);