tcp_cubic: fix clock dependency

The hystart code was written with assumption that HZ=1000.
Replace the use of jiffies with bictcp_clock as a millisecond
real time clock.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Reported-by: Lucas Nussbaum <lucas.nussbaum@loria.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 19 insertions, 12 deletions

diff --git a/net/ipv4/tcp_cubic.c b/net/ipv4/tcp_cubic.c
index 66d3b00233ec..f4fb2d4b90ad 100644
--- a/net/ipv4/tcp_cubic.c
+++ b/net/ipv4/tcp_cubic.c
@@ -88,7 +88,7 @@ struct bictcp {
         u32     last_time;      /* time when updated last_cwnd */
         u32     bic_origin_point;/* origin point of bic function */
         u32     bic_K;          /* time to origin point from the beginning of the current epoch */
-        u32     delay_min;      /* min delay */
+        u32     delay_min;      /* min delay (msec << 3) */
         u32     epoch_start;    /* beginning of an epoch */
         u32     ack_cnt;        /* number of acks */
         u32     tcp_cwnd;       /* estimated tcp cwnd */
@@ -98,7 +98,7 @@ struct bictcp {
         u8      found;          /* the exit point is found? */
         u32     round_start;    /* beginning of each round */
         u32     end_seq;        /* end_seq of the round */
-        u32     last_jiffies;   /* last time when the ACK spacing is close */
+        u32     last_ack;       /* last time when the ACK spacing is close */
         u32     curr_rtt;       /* the minimum rtt of current round */
 };
 
@@ -119,12 +119,21 @@ static inline void bictcp_reset(struct bictcp *ca)
         ca->found = 0;
 }
 
+static inline u32 bictcp_clock(void)
+{
+#if HZ < 1000
+        return ktime_to_ms(ktime_get_real());
+#else
+        return jiffies_to_msecs(jiffies);
+#endif
+}
+
 static inline void bictcp_hystart_reset(struct sock *sk)
 {
         struct tcp_sock *tp = tcp_sk(sk);
         struct bictcp *ca = inet_csk_ca(sk);
 
-        ca->round_start = ca->last_jiffies = jiffies;
+        ca->round_start = ca->last_ack = bictcp_clock();
         ca->end_seq = tp->snd_nxt;
         ca->curr_rtt = 0;
         ca->sample_cnt = 0;
@@ -239,8 +248,8 @@ static inline void bictcp_update(struct bictcp *ca, u32 cwnd)
          */
 
         /* change the unit from HZ to bictcp_HZ */
-        t = ((tcp_time_stamp + (ca->delay_min>>3) - ca->epoch_start)
-             << BICTCP_HZ) / HZ;
+        t = ((tcp_time_stamp + msecs_to_jiffies(ca->delay_min>>3)
+              - ca->epoch_start) << BICTCP_HZ) / HZ;
 
         if (t < ca->bic_K)              /* t - K */
                 offs = ca->bic_K - t;
@@ -342,14 +351,12 @@ static void hystart_update(struct sock *sk, u32 delay)
         struct bictcp *ca = inet_csk_ca(sk);
 
         if (!(ca->found & hystart_detect)) {
-                u32 curr_jiffies = jiffies;
+                u32 now = bictcp_clock();
 
                 /* first detection parameter - ack-train detection */
-                if ((s32)(curr_jiffies - ca->last_jiffies) <=
-                    msecs_to_jiffies(hystart_ack_delta)) {
-                        ca->last_jiffies = curr_jiffies;
-                        if ((s32) (curr_jiffies - ca->round_start) >
-                            ca->delay_min >> 4)
+                if ((s32)(now - ca->last_ack) <= hystart_ack_delta) {
+                        ca->last_ack = now;
+                        if ((s32)(now - ca->round_start) > ca->delay_min >> 4)
                                 ca->found |= HYSTART_ACK_TRAIN;
                 }
 
@@ -396,7 +403,7 @@ static void bictcp_acked(struct sock *sk, u32 cnt, s32 rtt_us)
         if ((s32)(tcp_time_stamp - ca->epoch_start) < HZ)
                 return;
 
-        delay = usecs_to_jiffies(rtt_us) << 3;
+        delay = (rtt_us << 3) / USEC_PER_MSEC;
         if (delay == 0)
                 delay = 1;