[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>

11 files changed, 38 insertions, 28 deletions

diff --git a/net/ipv4/tcp_bic.c b/net/ipv4/tcp_bic.c
index 519de091a94d..4586211e3757 100644
--- a/net/ipv4/tcp_bic.c
+++ b/net/ipv4/tcp_bic.c
@@ -206,7 +206,7 @@ static void bictcp_state(struct sock *sk, u8 new_state)
 /* Track delayed acknowledgment ratio using sliding window
  * ratio = (15*ratio + sample) / 16
  */
-static void bictcp_acked(struct sock *sk, u32 cnt, ktime_t last)
+static void bictcp_acked(struct sock *sk, u32 cnt, s32 rtt)
 {
         const struct inet_connection_sock *icsk = inet_csk(sk);
 
diff --git a/net/ipv4/tcp_cubic.c b/net/ipv4/tcp_cubic.c
index d17da30d82d6..0c44bb67a671 100644
--- a/net/ipv4/tcp_cubic.c
+++ b/net/ipv4/tcp_cubic.c
@@ -334,7 +334,7 @@ static void bictcp_state(struct sock *sk, u8 new_state)
 /* Track delayed acknowledgment ratio using sliding window
  * ratio = (15*ratio + sample) / 16
  */
-static void bictcp_acked(struct sock *sk, u32 cnt, ktime_t last)
+static void bictcp_acked(struct sock *sk, u32 cnt, s32 rtt_us)
 {
         const struct inet_connection_sock *icsk = inet_csk(sk);
 
diff --git a/net/ipv4/tcp_htcp.c b/net/ipv4/tcp_htcp.c
index 08a02e6045c9..fa61663ace3b 100644
--- a/net/ipv4/tcp_htcp.c
+++ b/net/ipv4/tcp_htcp.c
@@ -98,7 +98,7 @@ static inline void measure_rtt(struct sock *sk)
         }
 }
 
-static void measure_achieved_throughput(struct sock *sk, u32 pkts_acked, ktime_t last)
+static void measure_achieved_throughput(struct sock *sk, u32 pkts_acked, s32 rtt)
 {
         const struct inet_connection_sock *icsk = inet_csk(sk);
         const struct tcp_sock *tp = tcp_sk(sk);
diff --git a/net/ipv4/tcp_illinois.c b/net/ipv4/tcp_illinois.c
index cc5de6f69d46..64f1cbaf96e8 100644
--- a/net/ipv4/tcp_illinois.c
+++ b/net/ipv4/tcp_illinois.c
@@ -83,18 +83,16 @@ static void tcp_illinois_init(struct sock *sk)
 }
 
 /* Measure RTT for each ack. */
-static void tcp_illinois_acked(struct sock *sk, u32 pkts_acked, ktime_t last)
+static void tcp_illinois_acked(struct sock *sk, u32 pkts_acked, s32 rtt)
 {
         struct illinois *ca = inet_csk_ca(sk);
-        u32 rtt;
 
         ca->acked = pkts_acked;
 
-        if (ktime_equal(last, net_invalid_timestamp()))
+        /* dup ack, no rtt sample */
+        if (rtt < 0)
                 return;
 
-        rtt = ktime_to_us(net_timedelta(last));
-
         /* ignore bogus values, this prevents wraparound in alpha math */
         if (rtt > RTT_MAX)
                 rtt = RTT_MAX;
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index fec8a7a4dbaf..4b255fe999d9 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2490,12 +2490,23 @@ static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p)
                 tcp_ack_update_rtt(sk, acked, seq_rtt);
                 tcp_ack_packets_out(sk);
 
-                /* Is the ACK triggering packet unambiguous? */
-                if (acked & FLAG_RETRANS_DATA_ACKED)
-                        last_ackt = net_invalid_timestamp();
+                if (ca_ops->pkts_acked) {
+                        s32 rtt_us = -1;
+
+                        /* Is the ACK triggering packet unambiguous? */
+                        if (!(acked & FLAG_RETRANS_DATA_ACKED)) {
+                                /* High resolution needed and available? */
+                                if (ca_ops->flags & TCP_CONG_RTT_STAMP &&
+                                    !ktime_equal(last_ackt,
+                                                 net_invalid_timestamp()))
+                                        rtt_us = ktime_us_delta(ktime_get_real(),
+                                                                last_ackt);
+                                else if (seq_rtt > 0)
+                                        rtt_us = jiffies_to_usecs(seq_rtt);
+                        }
 
-                if (ca_ops->pkts_acked)
-                        ca_ops->pkts_acked(sk, pkts_acked, last_ackt);
+                        ca_ops->pkts_acked(sk, pkts_acked, rtt_us);
+                }
         }
 
 #if FASTRETRANS_DEBUG > 0
diff --git a/net/ipv4/tcp_lp.c b/net/ipv4/tcp_lp.c
index 80e140e3ec2d..e7f5ef92cbd8 100644
--- a/net/ipv4/tcp_lp.c
+++ b/net/ipv4/tcp_lp.c
@@ -260,13 +260,13 @@ static void tcp_lp_rtt_sample(struct sock *sk, u32 rtt)
  * newReno in increase case.
  * We work it out by following the idea from TCP-LP's paper directly
  */
-static void tcp_lp_pkts_acked(struct sock *sk, u32 num_acked, ktime_t last)
+static void tcp_lp_pkts_acked(struct sock *sk, u32 num_acked, s32 rtt_us)
 {
         struct tcp_sock *tp = tcp_sk(sk);
         struct lp *lp = inet_csk_ca(sk);
 
-        if (!ktime_equal(last, net_invalid_timestamp()))
-                tcp_lp_rtt_sample(sk,  ktime_to_us(net_timedelta(last)));
+        if (rtt_us > 0)
+                tcp_lp_rtt_sample(sk, rtt_us);
 
         /* calc inference */
         if (tcp_time_stamp > tp->rx_opt.rcv_tsecr)
diff --git a/net/ipv4/tcp_vegas.c b/net/ipv4/tcp_vegas.c
index 914e0307f7af..b49dedcda52d 100644
--- a/net/ipv4/tcp_vegas.c
+++ b/net/ipv4/tcp_vegas.c
@@ -112,16 +112,16 @@ EXPORT_SYMBOL_GPL(tcp_vegas_init);
  *   o min-filter RTT samples from a much longer window (forever for now)
  *     to find the propagation delay (baseRTT)
  */
-void tcp_vegas_pkts_acked(struct sock *sk, u32 cnt, ktime_t last)
+void tcp_vegas_pkts_acked(struct sock *sk, u32 cnt, s32 rtt_us)
 {
         struct vegas *vegas = inet_csk_ca(sk);
         u32 vrtt;
 
-        if (ktime_equal(last, net_invalid_timestamp()))
+        if (rtt_us < 0)
                 return;
 
         /* Never allow zero rtt or baseRTT */
-        vrtt = ktime_to_us(net_timedelta(last)) + 1;
+        vrtt = rtt_us + 1;
 
         /* Filter to find propagation delay: */
         if (vrtt < vegas->baseRTT)
diff --git a/net/ipv4/tcp_vegas.h b/net/ipv4/tcp_vegas.h
index 502fa8183634..6c0eea2f8249 100644
--- a/net/ipv4/tcp_vegas.h
+++ b/net/ipv4/tcp_vegas.h
@@ -17,7 +17,7 @@ struct vegas {
 
 extern void tcp_vegas_init(struct sock *sk);
 extern void tcp_vegas_state(struct sock *sk, u8 ca_state);
-extern void tcp_vegas_pkts_acked(struct sock *sk, u32 cnt, ktime_t last);
+extern void tcp_vegas_pkts_acked(struct sock *sk, u32 cnt, s32 rtt_us);
 extern void tcp_vegas_cwnd_event(struct sock *sk, enum tcp_ca_event event);
 extern void tcp_vegas_get_info(struct sock *sk, u32 ext, struct sk_buff *skb);
 
diff --git a/net/ipv4/tcp_veno.c b/net/ipv4/tcp_veno.c
index 7a55ddf86032..8fb2aee0b1a4 100644
--- a/net/ipv4/tcp_veno.c
+++ b/net/ipv4/tcp_veno.c
@@ -69,16 +69,16 @@ static void tcp_veno_init(struct sock *sk)
 }
 
 /* Do rtt sampling needed for Veno. */
-static void tcp_veno_pkts_acked(struct sock *sk, u32 cnt, ktime_t last)
+static void tcp_veno_pkts_acked(struct sock *sk, u32 cnt, s32 rtt_us)
 {
         struct veno *veno = inet_csk_ca(sk);
         u32 vrtt;
 
-        if (ktime_equal(last, net_invalid_timestamp()))
+        if (rtt_us < 0)
                 return;
 
         /* Never allow zero rtt or baseRTT */
-        vrtt = ktime_to_us(net_timedelta(last)) + 1;
+        vrtt = rtt_us + 1;
 
         /* Filter to find propagation delay: */
         if (vrtt < veno->basertt)
diff --git a/net/ipv4/tcp_westwood.c b/net/ipv4/tcp_westwood.c
index e61e09dd513e..20151d6a6241 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);
 }
 
 /*
diff --git a/net/ipv4/tcp_yeah.c b/net/ipv4/tcp_yeah.c
index c04b7c6ec702..c107fba7430e 100644
--- a/net/ipv4/tcp_yeah.c
+++ b/net/ipv4/tcp_yeah.c
@@ -58,7 +58,7 @@ static void tcp_yeah_init(struct sock *sk)
 }
 
 
-static void tcp_yeah_pkts_acked(struct sock *sk, u32 pkts_acked, ktime_t last)
+static void tcp_yeah_pkts_acked(struct sock *sk, u32 pkts_acked, s32 rtt_us)
 {
         const struct inet_connection_sock *icsk = inet_csk(sk);
         struct yeah *yeah = inet_csk_ca(sk);
@@ -66,7 +66,7 @@ static void tcp_yeah_pkts_acked(struct sock *sk, u32 pkts_acked, ktime_t last)
         if (icsk->icsk_ca_state == TCP_CA_Open)
                 yeah->pkts_acked = pkts_acked;
 
-        tcp_vegas_pkts_acked(sk, pkts_acked, last);
+        tcp_vegas_pkts_acked(sk, pkts_acked, rtt_us);
 }
 
 static void tcp_yeah_cong_avoid(struct sock *sk, u32 ack,