Adding upstream version 4.5.upstream/4.5

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

1 files changed, 1441 insertions, 0 deletions

diff --git a/reference.c b/reference.c
new file mode 100644
index 0000000..97dfbe9
--- /dev/null
+++ b/reference.c
@@ -0,0 +1,1441 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Richard P. Curnow  1997-2003
+ * Copyright (C) Miroslav Lichvar  2009-2018, 2020, 2022
+ * 
+ * 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.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  This module keeps track of the source which we are claiming to be
+  our reference, for the purposes of generating outgoing NTP packets */
+
+#include "config.h"
+
+#include "sysincl.h"
+
+#include "memory.h"
+#include "reference.h"
+#include "util.h"
+#include "conf.h"
+#include "logging.h"
+#include "local.h"
+#include "sched.h"
+
+/* ================================================== */
+
+/* The minimum allowed skew */
+#define MIN_SKEW 1.0e-12
+
+/* The update interval of the reference in the local reference mode */
+#define LOCAL_REF_UPDATE_INTERVAL 64.0
+
+/* Interval between updates of the drift file */
+#define MAX_DRIFTFILE_AGE 3600.0
+
+static int are_we_synchronised;
+static int enable_local_stratum;
+static int local_stratum;
+static int local_orphan;
+static double local_distance;
+static struct timespec local_ref_time;
+static NTP_Leap our_leap_status;
+static int our_leap_sec;
+static int our_tai_offset;
+static int our_stratum;
+static uint32_t our_ref_id;
+static IPAddr our_ref_ip;
+static struct timespec our_ref_time;
+static double our_skew;
+static double our_residual_freq;
+static double our_root_delay;
+static double our_root_dispersion;
+static double our_offset_sd;
+static double our_frequency_sd;
+
+static double max_update_skew;
+
+static double last_offset;
+static double avg2_offset;
+static int avg2_moving;
+
+static double correction_time_ratio;
+
+/* Flag indicating that we are initialised */
+static int initialised = 0;
+
+/* Current operating mode */
+static REF_Mode mode;
+
+/* Threshold and update limit for stepping clock */
+static int make_step_limit;
+static double make_step_threshold;
+
+/* Number of updates before offset checking, number of ignored updates
+   before exiting and the maximum allowed offset */
+static int max_offset_delay;
+static int max_offset_ignore;
+static double max_offset;
+
+/* Threshold for logging clock changes to syslog */
+static double log_change_threshold;
+
+/* Flag, threshold and user for sending mail notification on large clock changes */
+static int do_mail_change;
+static double mail_change_threshold;
+static char *mail_change_user;
+
+/* Handler for mode ending */
+static REF_ModeEndHandler mode_end_handler = NULL;
+
+/* Filename of the drift file. */
+static char *drift_file=NULL;
+static double drift_file_age;
+
+static void update_drift_file(double, double);
+
+/* Leap second handling mode */
+static REF_LeapMode leap_mode;
+
+/* Time of UTC midnight of the upcoming or previous leap second */
+static time_t leap_when;
+
+/* Flag indicating the clock was recently corrected for leap second and it may
+   not have correct time yet (missing 23:59:60 in the UTC time scale) */
+static int leap_in_progress;
+
+/* Timer for the leap second handler */
+static SCH_TimeoutID leap_timeout_id;
+
+/* Name of a system timezone containing leap seconds occuring at midnight */
+static char *leap_tzname;
+
+/* ================================================== */
+
+static LOG_FileID logfileid;
+
+/* ================================================== */
+
+/* Exponential moving averages of absolute clock frequencies
+   used as a fallback when synchronisation is lost. */
+
+struct fb_drift {
+  double freq;
+  double secs;
+};
+
+static int fb_drift_min;
+static int fb_drift_max;
+
+static struct fb_drift *fb_drifts = NULL;
+static int next_fb_drift;
+static SCH_TimeoutID fb_drift_timeout_id;
+
+/* Monotonic timestamp of the last reference update */
+static double last_ref_update;
+static double last_ref_update_interval;
+
+static double last_ref_adjustment;
+static int ref_adjustments;
+
+/* ================================================== */
+
+static NTP_Leap get_tz_leap(time_t when, int *tai_offset);
+static void update_leap_status(NTP_Leap leap, time_t now, int reset);
+
+/* ================================================== */
+
+static void
+handle_slew(struct timespec *raw,
+            struct timespec *cooked,
+            double dfreq,
+            double doffset,
+            LCL_ChangeType change_type,
+            void *anything)
+{
+  double delta;
+  struct timespec now;
+
+  if (!UTI_IsZeroTimespec(&our_ref_time))
+    UTI_AdjustTimespec(&our_ref_time, cooked, &our_ref_time, &delta, dfreq, doffset);
+
+  if (change_type == LCL_ChangeUnknownStep) {
+    last_ref_update = 0.0;
+    REF_SetUnsynchronised();
+  }
+
+  /* When the clock was stepped, check if that doesn't change our leap status
+     and also reset the leap timeout to undo the shift in the scheduler */
+  if (change_type != LCL_ChangeAdjust && our_leap_sec && !leap_in_progress) {
+    LCL_ReadRawTime(&now);
+    update_leap_status(our_leap_status, now.tv_sec, 1);
+  }
+}
+
+/* ================================================== */
+
+void
+REF_Initialise(void)
+{
+  FILE *in;
+  double file_freq_ppm, file_skew_ppm;
+  double our_frequency_ppm;
+  int tai_offset;
+
+  mode = REF_ModeNormal;
+  are_we_synchronised = 0;
+  our_leap_status = LEAP_Unsynchronised;
+  our_leap_sec = 0;
+  our_tai_offset = 0;
+  initialised = 1;
+  our_root_dispersion = 1.0;
+  our_root_delay = 1.0;
+  our_frequency_ppm = 0.0;
+  our_skew = 1.0; /* i.e. rather bad */
+  our_residual_freq = 0.0;
+  our_frequency_sd = 0.0;
+  our_offset_sd = 0.0;
+  drift_file_age = 0.0;
+
+  /* Now see if we can get the drift file opened */
+  drift_file = CNF_GetDriftFile();
+  if (drift_file) {
+    in = UTI_OpenFile(NULL, drift_file, NULL, 'r', 0);
+    if (in) {
+      if (fscanf(in, "%lf%lf", &file_freq_ppm, &file_skew_ppm) == 2) {
+        /* We have read valid data */
+        our_frequency_ppm = file_freq_ppm;
+        our_skew = 1.0e-6 * file_skew_ppm;
+        if (our_skew < MIN_SKEW)
+          our_skew = MIN_SKEW;
+        LOG(LOGS_INFO, "Frequency %.3f +/- %.3f ppm read from %s",
+            file_freq_ppm, file_skew_ppm, drift_file);
+        LCL_SetAbsoluteFrequency(our_frequency_ppm);
+      } else {
+        LOG(LOGS_WARN, "Could not read valid frequency and skew from driftfile %s",
+            drift_file);
+      }
+      fclose(in);
+    }
+  }
+    
+  if (our_frequency_ppm == 0.0) {
+    our_frequency_ppm = LCL_ReadAbsoluteFrequency();
+    if (our_frequency_ppm != 0.0) {
+      LOG(LOGS_INFO, "Initial frequency %.3f ppm", our_frequency_ppm);
+    }
+  }
+
+  logfileid = CNF_GetLogTracking() ? LOG_FileOpen("tracking",
+      "   Date (UTC) Time     IP Address   St   Freq ppm   Skew ppm     Offset L Co  Offset sd Rem. corr. Root delay Root disp. Max. error")
+    : -1;
+
+  max_update_skew = fabs(CNF_GetMaxUpdateSkew()) * 1.0e-6;
+
+  correction_time_ratio = CNF_GetCorrectionTimeRatio();
+
+  enable_local_stratum = CNF_AllowLocalReference(&local_stratum, &local_orphan, &local_distance);
+  UTI_ZeroTimespec(&local_ref_time);
+
+  leap_when = 0;
+  leap_timeout_id = 0;
+  leap_in_progress = 0;
+  leap_mode = CNF_GetLeapSecMode();
+  /* Switch to step mode if the system driver doesn't support leap */
+  if (leap_mode == REF_LeapModeSystem && !LCL_CanSystemLeap())
+    leap_mode = REF_LeapModeStep;
+
+  leap_tzname = CNF_GetLeapSecTimezone();
+  if (leap_tzname) {
+    /* Check that the timezone has good data for Jun 30 2012 and Dec 31 2012 */
+    if (get_tz_leap(1341014400, &tai_offset) == LEAP_InsertSecond && tai_offset == 34 &&
+        get_tz_leap(1356912000, &tai_offset) == LEAP_Normal && tai_offset == 35) {
+      LOG(LOGS_INFO, "Using %s timezone to obtain leap second data", leap_tzname);
+    } else {
+      LOG(LOGS_WARN, "Timezone %s failed leap second check, ignoring", leap_tzname);
+      leap_tzname = NULL;
+    }
+  }
+
+  CNF_GetMakeStep(&make_step_limit, &make_step_threshold);
+  CNF_GetMaxChange(&max_offset_delay, &max_offset_ignore, &max_offset);
+  CNF_GetMailOnChange(&do_mail_change, &mail_change_threshold, &mail_change_user);
+  log_change_threshold = CNF_GetLogChange();
+
+  CNF_GetFallbackDrifts(&fb_drift_min, &fb_drift_max);
+
+  if (fb_drift_max >= fb_drift_min && fb_drift_min > 0) {
+    fb_drifts = MallocArray(struct fb_drift, fb_drift_max - fb_drift_min + 1);
+    memset(fb_drifts, 0, sizeof (struct fb_drift) * (fb_drift_max - fb_drift_min + 1));
+    next_fb_drift = 0;
+    fb_drift_timeout_id = 0;
+  }
+
+  UTI_ZeroTimespec(&our_ref_time);
+  last_ref_update = 0.0;
+  last_ref_update_interval = 0.0;
+  last_ref_adjustment = 0.0;
+  ref_adjustments = 0;
+
+  LCL_AddParameterChangeHandler(handle_slew, NULL);
+
+  /* Make first entry in tracking log */
+  REF_SetUnsynchronised();
+}
+
+/* ================================================== */
+
+void
+REF_Finalise(void)
+{
+  update_leap_status(LEAP_Unsynchronised, 0, 0);
+
+  if (drift_file) {
+    update_drift_file(LCL_ReadAbsoluteFrequency(), our_skew);
+  }
+
+  LCL_RemoveParameterChangeHandler(handle_slew, NULL);
+
+  Free(fb_drifts);
+
+  initialised = 0;
+}
+
+/* ================================================== */
+
+void REF_SetMode(REF_Mode new_mode)
+{
+  mode = new_mode;
+}
+
+/* ================================================== */
+
+REF_Mode
+REF_GetMode(void)
+{
+  return mode;
+}
+
+/* ================================================== */
+
+void
+REF_SetModeEndHandler(REF_ModeEndHandler handler)
+{
+  mode_end_handler = handler;
+}
+
+/* ================================================== */
+
+REF_LeapMode
+REF_GetLeapMode(void)
+{
+  return leap_mode;
+}
+
+/* ================================================== */
+/* Update the drift coefficients to the file. */
+
+static void
+update_drift_file(double freq_ppm, double skew)
+{
+  FILE *out;
+
+  /* Create a temporary file with a '.tmp' extension. */
+  out = UTI_OpenFile(NULL, drift_file, ".tmp", 'w', 0644);
+  if (!out)
+    return;
+
+  /* Write the frequency and skew parameters in ppm */
+  fprintf(out, "%20.6f %20.6f\n", freq_ppm, 1.0e6 * skew);
+  fclose(out);
+
+  /* Rename the temporary file to the correct location */
+  if (!UTI_RenameTempFile(NULL, drift_file, ".tmp", NULL))
+    ;
+}
+
+/* ================================================== */
+
+static void
+update_fb_drifts(double freq_ppm, double update_interval)
+{
+  int i, secs;
+
+  assert(are_we_synchronised);
+
+  if (next_fb_drift > 0) {
+#if 0
+    /* Reset drifts that were used when we were unsynchronised */
+    for (i = 0; i < next_fb_drift - fb_drift_min; i++)
+      fb_drifts[i].secs = 0.0;
+#endif
+    next_fb_drift = 0;
+  }
+
+  SCH_RemoveTimeout(fb_drift_timeout_id);
+  fb_drift_timeout_id = 0;
+
+  if (update_interval < 1.0 || update_interval > last_ref_update_interval * 4.0)
+    return;
+
+  for (i = 0; i < fb_drift_max - fb_drift_min + 1; i++) {
+    secs = 1 << (i + fb_drift_min);
+    if (fb_drifts[i].secs < secs) {
+      /* Calculate average over 2 * secs interval before switching to
+         exponential updating */
+      fb_drifts[i].freq = (fb_drifts[i].freq * fb_drifts[i].secs +
+          update_interval * 0.5 * freq_ppm) / (update_interval * 0.5 + fb_drifts[i].secs);
+      fb_drifts[i].secs += update_interval * 0.5;
+    } else {
+      /* Update exponential moving average. The smoothing factor for update
+         interval equal to secs is about 0.63, for half interval about 0.39,
+         for double interval about 0.86. */
+      fb_drifts[i].freq += (1 - 1.0 / exp(update_interval / secs)) *
+        (freq_ppm - fb_drifts[i].freq);
+    }
+
+    DEBUG_LOG("Fallback drift %d updated: %f ppm %f seconds",
+              i + fb_drift_min, fb_drifts[i].freq, fb_drifts[i].secs);
+  }
+}
+
+/* ================================================== */
+
+static void
+fb_drift_timeout(void *arg)
+{
+  assert(next_fb_drift >= fb_drift_min && next_fb_drift <= fb_drift_max);
+
+  fb_drift_timeout_id = 0;
+
+  DEBUG_LOG("Fallback drift %d active: %f ppm",
+            next_fb_drift, fb_drifts[next_fb_drift - fb_drift_min].freq);
+  LCL_SetAbsoluteFrequency(fb_drifts[next_fb_drift - fb_drift_min].freq);
+  REF_SetUnsynchronised();
+}
+
+/* ================================================== */
+
+static void
+schedule_fb_drift(void)
+{
+  int i, c, secs;
+  double unsynchronised, now;
+
+  if (fb_drift_timeout_id)
+    return; /* already scheduled */
+
+  now = SCH_GetLastEventMonoTime();
+  unsynchronised = now - last_ref_update;
+
+  for (c = secs = 0, i = fb_drift_min; i <= fb_drift_max; i++) {
+    secs = 1 << i;
+
+    if (fb_drifts[i - fb_drift_min].secs < secs)
+      continue;
+
+    if (unsynchronised < secs && i > next_fb_drift)
+      break;
+
+    c = i;
+  }
+
+  if (c > next_fb_drift) {
+    LCL_SetAbsoluteFrequency(fb_drifts[c - fb_drift_min].freq);
+    next_fb_drift = c;
+    DEBUG_LOG("Fallback drift %d set", c);
+  }
+
+  if (i <= fb_drift_max) {
+    next_fb_drift = i;
+    fb_drift_timeout_id = SCH_AddTimeoutByDelay(secs - unsynchronised, fb_drift_timeout, NULL);
+    DEBUG_LOG("Fallback drift %d scheduled", i);
+  }
+}
+
+/* ================================================== */
+
+static void
+end_ref_mode(int result)
+{
+  mode = REF_ModeIgnore;
+
+  /* Dispatch the handler */
+  if (mode_end_handler)
+    (mode_end_handler)(result);
+}
+
+/* ================================================== */
+
+#define BUFLEN 255
+#define S_MAX_USER_LEN "128"
+
+static void
+maybe_log_offset(double offset, time_t now)
+{
+  double abs_offset;
+  FILE *p;
+  char buffer[BUFLEN], host[BUFLEN];
+  struct tm *tm;
+
+  abs_offset = fabs(offset);
+
+  if (abs_offset > log_change_threshold) {
+    LOG(LOGS_WARN, "System clock wrong by %.6f seconds", -offset);
+  }
+
+  if (do_mail_change &&
+      (abs_offset > mail_change_threshold)) {
+    snprintf(buffer, sizeof (buffer), "%s -t", MAIL_PROGRAM);
+    p = popen(buffer, "w");
+    if (p) {
+      if (gethostname(host, sizeof(host)) < 0) {
+        strcpy(host, "<UNKNOWN>");
+      }
+      host[sizeof (host) - 1] = '\0';
+
+      fprintf(p, "To: %s\n", mail_change_user);
+      fprintf(p, "Subject: chronyd reports change to system clock on node [%s]\n", host);
+      fputs("\n", p);
+
+      tm = localtime(&now);
+      if (tm) {
+        strftime(buffer, sizeof (buffer),
+                 "On %A, %d %B %Y\n  with the system clock reading %H:%M:%S (%Z)", tm);
+        fputs(buffer, p);
+      }
+
+      /* If offset < 0 the local clock is slow, so we are applying a
+         positive change to it to bring it into line, hence the
+         negation of 'offset' in the next statement (and earlier) */
+      fprintf(p,
+              "\n\nchronyd started to apply an adjustment of %.3f seconds to it,\n"
+              "  which exceeded the reporting threshold of %.3f seconds\n\n",
+              -offset, mail_change_threshold);
+      pclose(p);
+    } else {
+      LOG(LOGS_ERR, "Could not send mail notification to user %s\n",
+          mail_change_user);
+    }
+  }
+
+}
+
+/* ================================================== */
+
+static int
+is_step_limit_reached(double offset, double offset_correction)
+{
+  if (make_step_limit == 0) {
+    return 0;
+  } else if (make_step_limit > 0) {
+    make_step_limit--;
+  }
+  return fabs(offset - offset_correction) > make_step_threshold;
+}
+
+/* ================================================== */
+
+static int
+is_offset_ok(double offset)
+{
+  if (max_offset_delay < 0)
+    return 1;
+
+  if (max_offset_delay > 0) {
+    max_offset_delay--;
+    return 1;
+  }
+
+  if (fabs(offset) > max_offset) {
+    LOG(LOGS_WARN, 
+        "Adjustment of %.3f seconds exceeds the allowed maximum of %.3f seconds (%s) ",
+        -offset, max_offset, !max_offset_ignore ? "exiting" : "ignored");
+    if (!max_offset_ignore)
+      end_ref_mode(0);
+    else if (max_offset_ignore > 0)
+      max_offset_ignore--;
+    return 0;
+  }
+  return 1;
+}
+
+/* ================================================== */
+
+static int
+is_leap_second_day(time_t when)
+{
+  struct tm *stm;
+
+  stm = gmtime(&when);
+  if (!stm)
+    return 0;
+
+  /* Allow leap second only on the last day of June and December */
+  return (stm->tm_mon == 5 && stm->tm_mday == 30) ||
+         (stm->tm_mon == 11 && stm->tm_mday == 31);
+}
+
+/* ================================================== */
+
+static NTP_Leap
+get_tz_leap(time_t when, int *tai_offset)
+{
+  static time_t last_tz_leap_check;
+  static NTP_Leap tz_leap;
+  static int tz_tai_offset;
+
+  struct tm stm, *tm;
+  time_t t;
+  char *tz_env, tz_orig[128];
+
+  *tai_offset = tz_tai_offset;
+
+  /* Do this check at most twice a day */
+  when = when / (12 * 3600) * (12 * 3600);
+  if (last_tz_leap_check == when)
+      return tz_leap;
+
+  last_tz_leap_check = when;
+  tz_leap = LEAP_Normal;
+  tz_tai_offset = 0;
+
+  tm = gmtime(&when);
+  if (!tm)
+    return tz_leap;
+
+  stm = *tm;
+
+  /* Temporarily switch to the timezone containing leap seconds */
+  tz_env = getenv("TZ");
+  if (tz_env) {
+    if (strlen(tz_env) >= sizeof (tz_orig))
+      return tz_leap;
+    strcpy(tz_orig, tz_env);
+  }
+  setenv("TZ", leap_tzname, 1);
+  tzset();
+
+  /* Get the TAI-UTC offset, which started at the epoch at 10 seconds */
+  t = mktime(&stm);
+  if (t != -1)
+    tz_tai_offset = t - when + 10;
+
+  /* Set the time to 23:59:60 and see how it overflows in mktime() */
+  stm.tm_sec = 60;
+  stm.tm_min = 59;
+  stm.tm_hour = 23;
+
+  t = mktime(&stm);
+
+  if (tz_env)
+    setenv("TZ", tz_orig, 1);
+  else
+    unsetenv("TZ");
+  tzset();
+
+  if (t == -1)
+    return tz_leap;
+
+  if (stm.tm_sec == 60)
+    tz_leap = LEAP_InsertSecond;
+  else if (stm.tm_sec == 1)
+    tz_leap = LEAP_DeleteSecond;
+
+  *tai_offset = tz_tai_offset;
+
+  return tz_leap;
+}
+
+/* ================================================== */
+
+static void
+leap_end_timeout(void *arg)
+{
+  leap_timeout_id = 0;
+  leap_in_progress = 0;
+
+  if (our_tai_offset)
+    our_tai_offset += our_leap_sec;
+  our_leap_sec = 0;
+
+  if (leap_mode == REF_LeapModeSystem)
+    LCL_SetSystemLeap(our_leap_sec, our_tai_offset);
+
+  if (our_leap_status == LEAP_InsertSecond ||
+      our_leap_status == LEAP_DeleteSecond)
+    our_leap_status = LEAP_Normal;
+}
+
+/* ================================================== */
+
+static void
+leap_start_timeout(void *arg)
+{
+  leap_in_progress = 1;
+
+  switch (leap_mode) {
+    case REF_LeapModeSystem:
+      DEBUG_LOG("Waiting for system clock leap second correction");
+      break;
+    case REF_LeapModeSlew:
+      LCL_NotifyLeap(our_leap_sec);
+      LCL_AccumulateOffset(our_leap_sec, 0.0);
+      LOG(LOGS_WARN, "Adjusting system clock for leap second");
+      break;
+    case REF_LeapModeStep:
+      LCL_NotifyLeap(our_leap_sec);
+      LCL_ApplyStepOffset(our_leap_sec);
+      LOG(LOGS_WARN, "System clock was stepped for leap second");
+      break;
+    case REF_LeapModeIgnore:
+      LOG(LOGS_WARN, "Ignoring leap second");
+      break;
+    default:
+      break;
+  }
+
+  /* Wait until the leap second is over with some extra room to be safe */
+  leap_timeout_id = SCH_AddTimeoutByDelay(2.0, leap_end_timeout, NULL);
+}
+
+/* ================================================== */
+
+static void
+set_leap_timeout(time_t now)
+{
+  struct timespec when;
+
+  /* Stop old timer if there is one */
+  SCH_RemoveTimeout(leap_timeout_id);
+  leap_timeout_id = 0;
+  leap_in_progress = 0;
+
+  if (!our_leap_sec)
+    return;
+
+  leap_when = (now / (24 * 3600) + 1) * (24 * 3600);
+
+  /* Insert leap second at 0:00:00 UTC, delete at 23:59:59 UTC.  If the clock
+     will be corrected by the system, timeout slightly sooner to be sure it
+     will happen before the system correction. */
+  when.tv_sec = leap_when;
+  when.tv_nsec = 0;
+  if (our_leap_sec < 0)
+    when.tv_sec--;
+  if (leap_mode == REF_LeapModeSystem) {
+    when.tv_sec--;
+    when.tv_nsec = 500000000;
+  }
+
+  leap_timeout_id = SCH_AddTimeout(&when, leap_start_timeout, NULL);
+}
+
+/* ================================================== */
+
+static void
+update_leap_status(NTP_Leap leap, time_t now, int reset)
+{
+  NTP_Leap tz_leap;
+  int leap_sec, tai_offset;
+
+  leap_sec = 0;
+  tai_offset = 0;
+
+  if (leap_tzname && now) {
+    tz_leap = get_tz_leap(now, &tai_offset);
+    if (leap == LEAP_Normal)
+      leap = tz_leap;
+  }
+
+  if (leap == LEAP_InsertSecond || leap == LEAP_DeleteSecond) {
+    /* Check that leap second is allowed today */
+
+    if (is_leap_second_day(now)) {
+      if (leap == LEAP_InsertSecond) {
+        leap_sec = 1;
+      } else {
+        leap_sec = -1;
+      }
+    } else {
+      leap = LEAP_Normal;
+    }
+  }
+  
+  if ((leap_sec != our_leap_sec || tai_offset != our_tai_offset)
+      && !REF_IsLeapSecondClose(NULL, 0.0)) {
+    our_leap_sec = leap_sec;
+    our_tai_offset = tai_offset;
+
+    switch (leap_mode) {
+      case REF_LeapModeSystem:
+        LCL_SetSystemLeap(our_leap_sec, our_tai_offset);
+        /* Fall through */
+      case REF_LeapModeSlew:
+      case REF_LeapModeStep:
+      case REF_LeapModeIgnore:
+        set_leap_timeout(now);
+        break;
+      default:
+        assert(0);
+        break;
+    }
+  } else if (reset) {
+    set_leap_timeout(now);
+  }
+
+  our_leap_status = leap;
+}
+
+/* ================================================== */
+
+static double
+get_root_dispersion(struct timespec *ts)
+{
+  if (UTI_IsZeroTimespec(&our_ref_time))
+    return 1.0;
+
+  return our_root_dispersion +
+         fabs(UTI_DiffTimespecsToDouble(ts, &our_ref_time)) *
+         (our_skew + fabs(our_residual_freq) + LCL_GetMaxClockError());
+}
+
+/* ================================================== */
+
+static void
+update_sync_status(struct timespec *now)
+{
+  double elapsed;
+
+  elapsed = fabs(UTI_DiffTimespecsToDouble(now, &our_ref_time));
+
+  LCL_SetSyncStatus(are_we_synchronised,
+                    our_offset_sd + elapsed * our_frequency_sd,
+                    our_root_delay / 2.0 + get_root_dispersion(now));
+}
+
+/* ================================================== */
+
+static void
+write_log(struct timespec *now, int combined_sources, double freq,
+          double offset, double offset_sd, double uncorrected_offset,
+          double orig_root_distance)
+{
+  const char leap_codes[4] = {'N', '+', '-', '?'};
+  double root_dispersion, max_error;
+  static double last_sys_offset = 0.0;
+
+  if (logfileid == -1)
+    return;
+
+  max_error = orig_root_distance + fabs(last_sys_offset);
+  root_dispersion = get_root_dispersion(now);
+  last_sys_offset = offset - uncorrected_offset;
+
+  LOG_FileWrite(logfileid,
+                "%s %-15s %2d %10.3f %10.3f %10.3e %1c %2d %10.3e %10.3e %10.3e %10.3e %10.3e",
+                UTI_TimeToLogForm(now->tv_sec),
+                our_ref_ip.family != IPADDR_UNSPEC ?
+                  UTI_IPToString(&our_ref_ip) : UTI_RefidToString(our_ref_id),
+                our_stratum, freq, 1.0e6 * our_skew, offset,
+                leap_codes[our_leap_status], combined_sources, offset_sd,
+                uncorrected_offset, our_root_delay, root_dispersion, max_error);
+}
+
+/* ================================================== */
+
+static void
+special_mode_sync(int valid, double offset)
+{
+  int step;
+
+  switch (mode) {
+    case REF_ModeInitStepSlew:
+      if (!valid) {
+        LOG(LOGS_WARN, "No suitable source for initstepslew");
+        end_ref_mode(0);
+        break;
+      }
+
+      step = fabs(offset) >= CNF_GetInitStepThreshold();
+
+      LOG(LOGS_INFO, "System's initial offset : %.6f seconds %s of true (%s)",
+          fabs(offset), offset >= 0 ? "fast" : "slow", step ? "step" : "slew");
+
+      if (step)
+        LCL_ApplyStepOffset(offset);
+      else
+        LCL_AccumulateOffset(offset, 0.0);
+
+      end_ref_mode(1);
+
+      break;
+    case REF_ModeUpdateOnce:
+    case REF_ModePrintOnce:
+      if (!valid) {
+        LOG(LOGS_WARN, "No suitable source for synchronisation");
+        end_ref_mode(0);
+        break;
+      }
+
+      step = mode == REF_ModeUpdateOnce;
+
+      LOG(LOGS_INFO, "System clock wrong by %.6f seconds (%s)",
+          -offset, step ? "step" : "ignored");
+
+      if (step)
+        LCL_ApplyStepOffset(offset);
+
+      end_ref_mode(1);
+
+      break;
+    case REF_ModeIgnore:
+      /* Do nothing until the mode is changed */
+      break;
+    default:
+      assert(0);
+  }
+}
+
+/* ================================================== */
+
+static void
+get_clock_estimates(int manual,
+                    double measured_freq, double measured_skew,
+                    double *estimated_freq, double *estimated_skew,
+                    double *residual_freq)
+{
+  double gain, expected_freq, expected_skew, extra_skew;
+
+  /* We assume that the local clock is running according to our previously
+     determined value */
+  expected_freq = 0.0;
+  expected_skew = our_skew;
+
+  /* Set new frequency based on weighted average of the expected and measured
+     skew.  Disable updates that are based on totally unreliable frequency
+     information unless it is a manual reference. */
+  if (manual) {
+    gain = 1.0;
+  } else if (fabs(measured_skew) > max_update_skew) {
+    DEBUG_LOG("Skew %f too large to track", measured_skew);
+    gain = 0.0;
+  } else {
+    gain = 3.0 * SQUARE(expected_skew) /
+           (3.0 * SQUARE(expected_skew) + SQUARE(measured_skew));
+  }
+
+  gain = CLAMP(0.0, gain, 1.0);
+
+  *estimated_freq = expected_freq + gain * (measured_freq - expected_freq);
+  *residual_freq = measured_freq - *estimated_freq;
+
+  extra_skew = sqrt(SQUARE(expected_freq - *estimated_freq) * (1.0 - gain) +
+                    SQUARE(measured_freq - *estimated_freq) * gain);
+
+  *estimated_skew = expected_skew + gain * (measured_skew - expected_skew) + extra_skew;
+}
+
+/* ================================================== */
+
+static void
+fuzz_ref_time(struct timespec *ts)
+{
+  uint32_t rnd;
+
+  /* Add a random value from interval [-1.0, 0.0] */
+  UTI_GetRandomBytes(&rnd, sizeof (rnd));
+  UTI_AddDoubleToTimespec(ts, -(double)rnd / (uint32_t)-1, ts);
+}
+
+/* ================================================== */
+
+static double
+get_correction_rate(double offset_sd, double update_interval)
+{
+  /* We want to correct the offset quickly, but we also want to keep the
+     frequency error caused by the correction itself low.
+
+     Define correction rate as the area of the region bounded by the graph of
+     offset corrected in time.  Set the rate so that the time needed to correct
+     an offset equal to the current sourcestats stddev will be equal to the
+     update interval multiplied by the correction time ratio (assuming linear
+     adjustment).  The offset and the time needed to make the correction are
+     inversely proportional.
+
+     This is only a suggestion and it's up to the system driver how the
+     adjustment will be executed. */
+
+  return correction_time_ratio * 0.5 * offset_sd * update_interval;
+}
+
+/* ================================================== */
+
+void
+REF_SetReference(int stratum, NTP_Leap leap, int combined_sources,
+                 uint32_t ref_id, IPAddr *ref_ip, struct timespec *ref_time,
+                 double offset, double offset_sd,
+                 double frequency, double frequency_sd, double skew,
+                 double root_delay, double root_dispersion)
+{
+  double uncorrected_offset, accumulate_offset, step_offset;
+  double residual_frequency, local_abs_frequency;
+  double elapsed, mono_now, update_interval, orig_root_distance;
+  struct timespec now, raw_now;
+  int manual;
+
+  assert(initialised);
+
+  /* Special modes are implemented elsewhere */
+  if (mode != REF_ModeNormal) {
+    special_mode_sync(1, offset);
+    return;
+  }
+
+  manual = leap == LEAP_Unsynchronised;
+
+  mono_now = SCH_GetLastEventMonoTime();
+  LCL_ReadRawTime(&raw_now);
+  LCL_GetOffsetCorrection(&raw_now, &uncorrected_offset, NULL);
+  UTI_AddDoubleToTimespec(&raw_now, uncorrected_offset, &now);
+
+  elapsed = UTI_DiffTimespecsToDouble(&now, ref_time);
+  offset += elapsed * frequency;
+
+  if (last_ref_update != 0.0) {
+    update_interval = mono_now - last_ref_update;
+  } else {
+    update_interval = 0.0;
+  }
+
+  /* Get new estimates of the frequency and skew including the new data */
+  get_clock_estimates(manual, frequency, skew,
+                      &frequency, &skew, &residual_frequency);
+
+  if (!is_offset_ok(offset))
+    return;
+
+  orig_root_distance = our_root_delay / 2.0 + get_root_dispersion(&now);
+
+  are_we_synchronised = leap != LEAP_Unsynchronised;
+  our_stratum = stratum + 1;
+  our_ref_id = ref_id;
+  if (ref_ip)
+    our_ref_ip = *ref_ip;
+  else
+    our_ref_ip.family = IPADDR_UNSPEC;
+  our_ref_time = *ref_time;
+  our_skew = skew;
+  our_residual_freq = residual_frequency;
+  our_root_delay = root_delay;
+  our_root_dispersion = root_dispersion;
+  our_frequency_sd = frequency_sd;
+  our_offset_sd = offset_sd;
+  last_ref_update = mono_now;
+  last_ref_update_interval = update_interval;
+  last_offset = offset;
+
+  /* Check if the clock should be stepped */
+  if (is_step_limit_reached(offset, uncorrected_offset)) {
+    /* Cancel the uncorrected offset and correct the total offset by step */
+    accumulate_offset = uncorrected_offset;
+    step_offset = offset - uncorrected_offset;
+  } else {
+    accumulate_offset = offset;
+    step_offset = 0.0;
+  }
+
+  /* Adjust the clock */
+  LCL_AccumulateFrequencyAndOffset(frequency, accumulate_offset,
+                                   get_correction_rate(offset_sd, update_interval));
+    
+  maybe_log_offset(offset, raw_now.tv_sec);
+
+  if (step_offset != 0.0) {
+    if (LCL_ApplyStepOffset(step_offset))
+      LOG(LOGS_WARN, "System clock was stepped by %.6f seconds", -step_offset);
+  }
+
+  update_leap_status(leap, raw_now.tv_sec, 0);
+  update_sync_status(&now);
+
+  /* Add a random error of up to one second to the reference time to make it
+     less useful when disclosed to NTP and cmdmon clients for estimating
+     receive timestamps in the interleaved symmetric NTP mode */
+  fuzz_ref_time(&our_ref_time);
+
+  local_abs_frequency = LCL_ReadAbsoluteFrequency();
+
+  write_log(&now, combined_sources, local_abs_frequency,
+            offset, offset_sd, uncorrected_offset, orig_root_distance);
+
+  if (drift_file) {
+    /* Update drift file at most once per hour */
+    drift_file_age += update_interval;
+    if (drift_file_age >= MAX_DRIFTFILE_AGE) {
+      update_drift_file(local_abs_frequency, our_skew);
+      drift_file_age = 0.0;
+    }
+  }
+
+  /* Update fallback drifts */
+  if (fb_drifts && are_we_synchronised) {
+    update_fb_drifts(local_abs_frequency, update_interval);
+    schedule_fb_drift();
+  }
+
+  /* Update the moving average of squares of offset, quickly on start */
+  if (avg2_moving) {
+    avg2_offset += 0.1 * (SQUARE(offset) - avg2_offset);
+  } else {
+    if (avg2_offset > 0.0 && avg2_offset < SQUARE(offset))
+      avg2_moving = 1;
+    avg2_offset = SQUARE(offset);
+  }
+
+  ref_adjustments = 0;
+}
+
+/* ================================================== */
+
+int
+REF_AdjustReference(double offset, double frequency)
+{
+  double adj_corr_rate, ref_corr_rate, mono_now;
+
+  mono_now = SCH_GetLastEventMonoTime();
+  ref_adjustments++;
+
+  adj_corr_rate = get_correction_rate(fabs(offset), mono_now - last_ref_adjustment);
+  ref_corr_rate = get_correction_rate(our_offset_sd, last_ref_update_interval) /
+                  ref_adjustments;
+  last_ref_adjustment = mono_now;
+
+  return LCL_AccumulateFrequencyAndOffsetNoHandlers(frequency, offset,
+                                                    MAX(adj_corr_rate, ref_corr_rate));
+}
+
+/* ================================================== */
+
+void
+REF_SetManualReference
+(
+ struct timespec *ref_time,
+ double offset,
+ double frequency,
+ double skew
+)
+{
+  /* We are not synchronised to an external source, as such.  This is
+     only supposed to be used with the local source option, really.
+     Log as MANU in the tracking log, packets will have NTP_REFID_LOCAL. */
+  REF_SetReference(0, LEAP_Unsynchronised, 1, 0x4D414E55UL, NULL,
+                   ref_time, offset, 0.0, frequency, skew, skew, 0.0, 0.0);
+}
+
+/* ================================================== */
+
+void
+REF_SetUnsynchronised(void)
+{
+  /* Variables required for logging to statistics log */
+  struct timespec now, now_raw;
+  double uncorrected_offset;
+
+  assert(initialised);
+
+  /* Special modes are implemented elsewhere */
+  if (mode != REF_ModeNormal) {
+    special_mode_sync(0, 0.0);
+    return;
+  }
+
+  LCL_ReadRawTime(&now_raw);
+  LCL_GetOffsetCorrection(&now_raw, &uncorrected_offset, NULL);
+  UTI_AddDoubleToTimespec(&now_raw, uncorrected_offset, &now);
+
+  if (fb_drifts) {
+    schedule_fb_drift();
+  }
+
+  update_leap_status(LEAP_Unsynchronised, 0, 0);
+  our_ref_ip.family = IPADDR_INET4;
+  our_ref_ip.addr.in4 = 0;
+  our_stratum = 0;
+  are_we_synchronised = 0;
+
+  LCL_SetSyncStatus(0, 0.0, 0.0);
+
+  write_log(&now, 0, LCL_ReadAbsoluteFrequency(), 0.0, 0.0, uncorrected_offset,
+            our_root_delay / 2.0 + get_root_dispersion(&now));
+}
+
+/* ================================================== */
+
+void
+REF_UpdateLeapStatus(NTP_Leap leap)
+{
+  struct timespec raw_now, now;
+
+  /* Wait for a full reference update if not already synchronised */
+  if (!are_we_synchronised)
+    return;
+
+  SCH_GetLastEventTime(&now, NULL, &raw_now);
+
+  update_leap_status(leap, raw_now.tv_sec, 0);
+
+  /* Update also the synchronisation status */
+  update_sync_status(&now);
+}
+
+/* ================================================== */
+
+void
+REF_GetReferenceParams
+(
+ struct timespec *local_time,
+ int *is_synchronised,
+ NTP_Leap *leap_status,
+ int *stratum,
+ uint32_t *ref_id,
+ struct timespec *ref_time,
+ double *root_delay,
+ double *root_dispersion
+)
+{
+  double dispersion, delta;
+
+  assert(initialised);
+
+  if (are_we_synchronised) {
+    dispersion = get_root_dispersion(local_time);
+  } else {
+    dispersion = 0.0;
+  }
+
+  /* Local reference is active when enabled and the clock is not synchronised
+     or the root distance exceeds the threshold */
+
+  if (are_we_synchronised &&
+      !(enable_local_stratum && our_root_delay / 2 + dispersion > local_distance)) {
+
+    *is_synchronised = 1;
+
+    *stratum = our_stratum;
+
+    *leap_status = !leap_in_progress ? our_leap_status : LEAP_Unsynchronised;
+    *ref_id = our_ref_id;
+    *ref_time = our_ref_time;
+    *root_delay = our_root_delay;
+    *root_dispersion = dispersion;
+
+  } else if (enable_local_stratum) {
+
+    *is_synchronised = 0;
+
+    *stratum = local_stratum;
+    *ref_id = NTP_REFID_LOCAL;
+
+    /* Keep the reference timestamp up to date.  Adjust the timestamp to make
+       sure that the transmit timestamp cannot come before this (which might
+       fail a test of an NTP client). */
+    delta = UTI_DiffTimespecsToDouble(local_time, &local_ref_time);
+    if (delta > LOCAL_REF_UPDATE_INTERVAL || delta < 1.0) {
+      UTI_AddDoubleToTimespec(local_time, -1.0, &local_ref_time);
+      fuzz_ref_time(&local_ref_time);
+    }
+
+    *ref_time = local_ref_time;
+
+    /* Not much else we can do for leap second bits - maybe need to
+       have a way for the administrator to feed leap bits in */
+    *leap_status = LEAP_Normal;
+    
+    *root_delay = 0.0;
+    *root_dispersion = 0.0;
+    
+  } else {
+
+    *is_synchronised = 0;
+
+    *leap_status = LEAP_Unsynchronised;
+    *stratum = NTP_MAX_STRATUM;
+    *ref_id = NTP_REFID_UNSYNC;
+    UTI_ZeroTimespec(ref_time);
+    /* These values seem to be standard for a client, and
+       any peer or client of ours will ignore them anyway because
+       we don't claim to be synchronised */
+    *root_dispersion = 1.0;
+    *root_delay = 1.0;
+
+  }
+}
+
+/* ================================================== */
+
+int
+REF_GetOurStratum(void)
+{
+  struct timespec now_cooked, ref_time;
+  int synchronised, stratum;
+  NTP_Leap leap_status;
+  uint32_t ref_id;
+  double root_delay, root_dispersion;
+
+  SCH_GetLastEventTime(&now_cooked, NULL, NULL);
+  REF_GetReferenceParams(&now_cooked, &synchronised, &leap_status, &stratum,
+                         &ref_id, &ref_time, &root_delay, &root_dispersion);
+
+  return stratum;
+}
+
+/* ================================================== */
+
+int
+REF_GetOrphanStratum(void)
+{
+  if (!enable_local_stratum || !local_orphan || mode != REF_ModeNormal)
+    return NTP_MAX_STRATUM;
+  return local_stratum;
+}
+
+/* ================================================== */
+
+double
+REF_GetSkew(void)
+{
+  return our_skew;
+}
+
+/* ================================================== */
+
+void
+REF_ModifyMaxupdateskew(double new_max_update_skew)
+{
+  max_update_skew = new_max_update_skew * 1.0e-6;
+  LOG(LOGS_INFO, "New maxupdateskew %f ppm", new_max_update_skew);
+}
+
+/* ================================================== */
+
+void
+REF_ModifyMakestep(int limit, double threshold)
+{
+  make_step_limit = limit;
+  make_step_threshold = threshold;
+  LOG(LOGS_INFO, "New makestep %f %d", threshold, limit);
+}
+
+/* ================================================== */
+
+void
+REF_EnableLocal(int stratum, double distance, int orphan)
+{
+  enable_local_stratum = 1;
+  local_stratum = CLAMP(1, stratum, NTP_MAX_STRATUM - 1);
+  local_distance = distance;
+  local_orphan = !!orphan;
+  LOG(LOGS_INFO, "%s local reference mode", "Enabled");
+}
+
+/* ================================================== */
+
+void
+REF_DisableLocal(void)
+{
+  enable_local_stratum = 0;
+  LOG(LOGS_INFO, "%s local reference mode", "Disabled");
+}
+
+/* ================================================== */
+
+#define LEAP_SECOND_CLOSE 5
+
+static int
+is_leap_close(time_t t)
+{
+  return leap_when != 0 &&
+         t >= leap_when - LEAP_SECOND_CLOSE && t < leap_when + LEAP_SECOND_CLOSE;
+}
+
+/* ================================================== */
+
+int REF_IsLeapSecondClose(struct timespec *ts, double offset)
+{
+  struct timespec now, now_raw;
+
+  SCH_GetLastEventTime(&now, NULL, &now_raw);
+
+  if (is_leap_close(now.tv_sec) || is_leap_close(now_raw.tv_sec))
+    return 1;
+
+  if (ts && (is_leap_close(ts->tv_sec) || is_leap_close(ts->tv_sec + offset)))
+    return 1;
+
+  return 0;
+}
+
+/* ================================================== */
+
+int
+REF_GetTaiOffset(struct timespec *ts)
+{
+  int tai_offset;
+
+  get_tz_leap(ts->tv_sec, &tai_offset);
+
+  return tai_offset;
+}
+
+/* ================================================== */
+
+void
+REF_GetTrackingReport(RPT_TrackingReport *rep)
+{
+  struct timespec now_raw, now_cooked;
+  double correction;
+  int synchronised;
+
+  LCL_ReadRawTime(&now_raw);
+  LCL_GetOffsetCorrection(&now_raw, &correction, NULL);
+  UTI_AddDoubleToTimespec(&now_raw, correction, &now_cooked);
+
+  REF_GetReferenceParams(&now_cooked, &synchronised,
+                         &rep->leap_status, &rep->stratum,
+                         &rep->ref_id, &rep->ref_time,
+                         &rep->root_delay, &rep->root_dispersion);
+
+  if (rep->stratum == NTP_MAX_STRATUM && !synchronised)
+    rep->stratum = 0;
+
+  rep->ip_addr.family = IPADDR_UNSPEC;
+  rep->current_correction = correction;
+  rep->freq_ppm = LCL_ReadAbsoluteFrequency();
+  rep->resid_freq_ppm = 0.0;
+  rep->skew_ppm = 0.0;
+  rep->last_update_interval = last_ref_update_interval;
+  rep->last_offset = last_offset;
+  rep->rms_offset = sqrt(avg2_offset);
+
+  if (synchronised) {
+    rep->ip_addr = our_ref_ip;
+    rep->resid_freq_ppm = 1.0e6 * our_residual_freq;
+    rep->skew_ppm = 1.0e6 * our_skew;
+  }
+}