Adding upstream version 4.0.upstream/4.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 368 insertions, 0 deletions

diff --git a/smooth.c b/smooth.c
new file mode 100644
index 0000000..4c350e9
--- /dev/null
+++ b/smooth.c
@@ -0,0 +1,368 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2015
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  Routines implementing time smoothing.
+
+  */
+
+#include "config.h"
+
+#include "sysincl.h"
+
+#include "conf.h"
+#include "local.h"
+#include "logging.h"
+#include "reference.h"
+#include "smooth.h"
+#include "util.h"
+
+/*
+  Time smoothing determines an offset that needs to be applied to the cooked
+  time to make it smooth for external observers.  Observed offset and frequency
+  change slowly and there are no discontinuities.  This can be used on an NTP
+  server to make it easier for the clients to track the time and keep their
+  clocks close together even when large offset or frequency corrections are
+  applied to the server's clock (e.g. after being offline for longer time).
+
+  Accumulated offset and frequency are smoothed out in three stages.  In the
+  first stage, the frequency is changed at a constant rate (wander) up to a
+  maximum, in the second stage the frequency stays at the maximum for as long
+  as needed and in the third stage the frequency is brought back to zero.
+
+              |
+    max_freq  +-------/--------\-------------
+              |      /|        |\
+        freq  |     / |        | \
+              |    /  |        |  \
+              |   /   |        |   \
+           0  +--/----+--------+----\--------
+              | /     |        |    |    time
+              |/      |        |    |
+
+        stage     1       2      3
+
+  Integral of this function is the smoothed out offset.  It's a continuous
+  piecewise polynomial with two quadratic parts and one linear.
+*/
+
+struct stage {
+  double wander;
+  double length;
+};
+
+#define NUM_STAGES 3
+
+static struct stage stages[NUM_STAGES];
+
+/* Enabled/disabled smoothing */
+static int enabled;
+
+/* Enabled/disabled mode where only leap seconds are smoothed out and normal
+   offset/frequency changes are ignored */
+static int leap_only_mode;
+
+/* Maximum skew/max_wander ratio to start updating offset and frequency */
+#define UNLOCK_SKEW_WANDER_RATIO 10000
+
+static int locked;
+
+/* Maximum wander and frequency offset */
+static double max_wander;
+static double max_freq;
+
+/* Frequency offset, time offset and the time of the last smoothing update */
+static double smooth_freq;
+static double smooth_offset;
+static struct timespec last_update;
+
+
+static void
+get_smoothing(struct timespec *now, double *poffset, double *pfreq,
+              double *pwander)
+{
+  double elapsed, length, offset, freq, wander;
+  int i;
+
+  elapsed = UTI_DiffTimespecsToDouble(now, &last_update);
+
+  offset = smooth_offset;
+  freq = smooth_freq;
+  wander = 0.0;
+
+  for (i = 0; i < NUM_STAGES; i++) {
+    if (elapsed <= 0.0)
+      break;
+
+    length = stages[i].length;
+    if (length >= elapsed)
+      length = elapsed;
+
+    wander = stages[i].wander;
+    offset -= length * (2.0 * freq + wander * length) / 2.0;
+    freq += wander * length;
+    elapsed -= length;
+  }
+
+  if (elapsed > 0.0) {
+    wander = 0.0;
+    offset -= elapsed * freq;
+  }
+
+  *poffset = offset;
+  *pfreq = freq;
+  if (pwander)
+    *pwander = wander;
+}
+
+static void
+update_stages(void)
+{
+  double s1, s2, s, l1, l2, l3, lc, f, f2, l1t[2], l3t[2], err[2];
+  int i, dir;
+
+  /* Prepare the three stages so that the integral of the frequency offset
+     is equal to the offset that should be smoothed out */
+
+  s1 = smooth_offset / max_wander;
+  s2 = SQUARE(smooth_freq) / (2.0 * SQUARE(max_wander));
+  
+  /* Calculate the lengths of the 1st and 3rd stage assuming there is no
+     frequency limit.  The direction of the 1st stage is selected so that
+     the lengths will not be negative.  With extremely small offsets both
+     directions may give a negative length due to numerical errors, so select
+     the one which gives a smaller error. */
+
+  for (i = 0, dir = -1; i <= 1; i++, dir += 2) {
+    err[i] = 0.0;
+    s = dir * s1 + s2;
+
+    if (s < 0.0) {
+      err[i] += -s;
+      s = 0.0;
+    }
+
+    l3t[i] = sqrt(s);
+    l1t[i] = l3t[i] - dir * smooth_freq / max_wander;
+
+    if (l1t[i] < 0.0) {
+      err[i] += l1t[i] * l1t[i];
+      l1t[i] = 0.0;
+    }
+  }
+
+  if (err[0] < err[1]) {
+    l1 = l1t[0];
+    l3 = l3t[0];
+    dir = -1;
+  } else {
+    l1 = l1t[1];
+    l3 = l3t[1];
+    dir = 1;
+  }
+
+  l2 = 0.0;
+
+  /* If the limit was reached, shorten 1st+3rd stages and set a 2nd stage */
+  f = dir * smooth_freq + l1 * max_wander - max_freq;
+  if (f > 0.0) {
+    lc = f / max_wander;
+
+    /* No 1st stage if the frequency is already above the maximum */
+    if (lc > l1) {
+      lc = l1;
+      f2 = dir * smooth_freq;
+    } else {
+      f2 = max_freq;
+    }
+
+    l2 = lc * (2.0 + f / f2);
+    l1 -= lc;
+    l3 -= lc;
+  }
+
+  stages[0].wander = dir * max_wander;
+  stages[0].length = l1;
+  stages[1].wander = 0.0;
+  stages[1].length = l2;
+  stages[2].wander = -dir * max_wander;
+  stages[2].length = l3;
+
+  for (i = 0; i < NUM_STAGES; i++) {
+    DEBUG_LOG("Smooth stage %d wander %e length %f",
+              i + 1, stages[i].wander, stages[i].length);
+  }
+}
+
+static void
+update_smoothing(struct timespec *now, double offset, double freq)
+{
+  /* Don't accept offset/frequency until the clock has stabilized */
+  if (locked) {
+    if (REF_GetSkew() / max_wander < UNLOCK_SKEW_WANDER_RATIO || leap_only_mode)
+      SMT_Activate(now);
+    return;
+  }
+
+  get_smoothing(now, &smooth_offset, &smooth_freq, NULL);
+  smooth_offset += offset;
+  smooth_freq = (smooth_freq - freq) / (1.0 - freq);
+  last_update = *now;
+
+  update_stages();
+
+  DEBUG_LOG("Smooth offset %e freq %e", smooth_offset, smooth_freq);
+}
+
+static void
+handle_slew(struct timespec *raw, struct timespec *cooked, double dfreq,
+            double doffset, LCL_ChangeType change_type, void *anything)
+{
+  double delta;
+
+  if (change_type == LCL_ChangeAdjust) {
+    if (leap_only_mode)
+      update_smoothing(cooked, 0.0, 0.0);
+    else
+      update_smoothing(cooked, doffset, dfreq);
+  }
+
+  if (!UTI_IsZeroTimespec(&last_update))
+    UTI_AdjustTimespec(&last_update, cooked, &last_update, &delta, dfreq, doffset);
+}
+
+void SMT_Initialise(void)
+{
+  CNF_GetSmooth(&max_freq, &max_wander, &leap_only_mode);
+  if (max_freq <= 0.0 || max_wander <= 0.0) {
+      enabled = 0;
+      return;
+  }
+
+  enabled = 1;
+  locked = 1;
+
+  /* Convert from ppm */
+  max_freq *= 1e-6;
+  max_wander *= 1e-6;
+
+  UTI_ZeroTimespec(&last_update);
+
+  LCL_AddParameterChangeHandler(handle_slew, NULL);
+}
+
+void SMT_Finalise(void)
+{
+  if (!enabled)
+    return;
+
+  LCL_RemoveParameterChangeHandler(handle_slew, NULL);
+}
+
+int SMT_IsEnabled(void)
+{
+  return enabled;
+}
+
+double
+SMT_GetOffset(struct timespec *now)
+{
+  double offset, freq;
+
+  if (!enabled)
+    return 0.0;
+  
+  get_smoothing(now, &offset, &freq, NULL);
+
+  return offset;
+}
+
+void
+SMT_Activate(struct timespec *now)
+{
+  if (!enabled || !locked)
+    return;
+
+  LOG(LOGS_INFO, "Time smoothing activated%s", leap_only_mode ?
+      " (leap seconds only)" : "");
+  locked = 0;
+  last_update = *now;
+}
+
+void
+SMT_Reset(struct timespec *now)
+{
+  int i;
+
+  if (!enabled)
+    return;
+
+  smooth_offset = 0.0;
+  smooth_freq = 0.0;
+  last_update = *now;
+
+  for (i = 0; i < NUM_STAGES; i++)
+    stages[i].wander = stages[i].length = 0.0;
+}
+
+void
+SMT_Leap(struct timespec *now, int leap)
+{
+  /* When the leap-only mode is disabled, the leap second will be accumulated
+     in handle_slew() as a normal offset */
+  if (!enabled || !leap_only_mode)
+    return;
+
+  update_smoothing(now, leap, 0.0);
+}
+
+int
+SMT_GetSmoothingReport(RPT_SmoothingReport *report, struct timespec *now)
+{
+  double length, elapsed;
+  int i;
+
+  if (!enabled)
+    return 0;
+
+  report->active = !locked;
+  report->leap_only = leap_only_mode;
+
+  get_smoothing(now, &report->offset, &report->freq_ppm, &report->wander_ppm);
+
+  /* Convert to ppm and negate (positive values mean faster/speeding up) */
+  report->freq_ppm *= -1.0e6;
+  report->wander_ppm *= -1.0e6;
+
+  elapsed = UTI_DiffTimespecsToDouble(now, &last_update);
+  if (!locked && elapsed >= 0.0) {
+    for (i = 0, length = 0.0; i < NUM_STAGES; i++)
+      length += stages[i].length;
+    report->last_update_ago = elapsed;
+    report->remaining_time = elapsed < length ? length - elapsed : 0.0;
+  } else {
+    report->last_update_ago = 0.0;
+    report->remaining_time = 0.0;
+  }
+
+  return 1;
+}