[TCP]: congestion control API pass RTT in microseconds

This patch changes the API for the callback that is done after an ACK is
received. It solves a couple of issues:

  * Some congestion controls want higher resolution value of RTT
    (controlled by TCP_CONG_RTT_SAMPLE flag). These don't really want a ktime, but
    all compute a RTT in microseconds.

  * Other congestion control could use RTT at jiffies resolution.

To keep API consistent the units should be the same for both cases, just the
resolution should change.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 3 deletions

diff --git a/net/ipv4/tcp_westwood.c b/net/ipv4/tcp_westwood.c
index e61e09dd513..20151d6a624 100644
--- a/net/ipv4/tcp_westwood.c
+++ b/net/ipv4/tcp_westwood.c
@@ -100,11 +100,12 @@ static void westwood_filter(struct westwood *w, u32 delta)
  * Called after processing group of packets.
  * but all westwood needs is the last sample of srtt.
  */
-static void tcp_westwood_pkts_acked(struct sock *sk, u32 cnt, ktime_t last)
+static void tcp_westwood_pkts_acked(struct sock *sk, u32 cnt, s32 rtt)
 {
         struct westwood *w = inet_csk_ca(sk);
-        if (cnt > 0)
-                w->rtt = tcp_sk(sk)->srtt >> 3;
+
+        if (rtt > 0)
+                w->rtt = usecs_to_jiffies(rtt);
 }
 
 /*