Adding upstream version 4.5.upstream/4.5upstream

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

1 files changed, 1876 insertions, 0 deletions

diff --git a/sources.c b/sources.c
new file mode 100644
index 0000000..e7ec4b8
--- /dev/null
+++ b/sources.c
@@ -0,0 +1,1876 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Richard P. Curnow  1997-2003
+ * Copyright (C) Miroslav Lichvar  2011-2016, 2018, 2020-2023
+ * 
+ * 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.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  The routines in this file manage the complete pool of sources that
+  we might be synchronizing to.  This includes NTP sources and others
+  (e.g. local reference clocks, eyeball + wristwatch etc).
+
+  */
+
+#include "config.h"
+
+#include "sysincl.h"
+
+#include "sources.h"
+#include "sourcestats.h"
+#include "memory.h"
+#include "ntp.h" /* For NTP_Leap */
+#include "ntp_sources.h"
+#include "local.h"
+#include "reference.h"
+#include "util.h"
+#include "conf.h"
+#include "logging.h"
+#include "reports.h"
+#include "nameserv.h"
+#include "sched.h"
+#include "regress.h"
+
+/* ================================================== */
+/* Flag indicating that we are initialised */
+static int initialised = 0;
+
+/* ================================================== */
+/* Structure used to hold info for selecting between sources */
+struct SelectInfo {
+  int select_ok;
+  double std_dev;
+  double root_distance;
+  double lo_limit;
+  double hi_limit;
+  double last_sample_ago;
+};
+
+/* ================================================== */
+/* This enum contains the flag values that are used to label
+   each source */
+typedef enum {
+  SRC_OK,               /* OK so far, not a final status! */
+  SRC_UNSELECTABLE,     /* Has noselect option set */
+  SRC_UNSYNCHRONISED,   /* Provides samples but not unsynchronised */
+  SRC_BAD_STATS,        /* Doesn't have valid stats data */
+  SRC_BAD_DISTANCE,     /* Has root distance longer than allowed maximum */
+  SRC_JITTERY,          /* Had std dev larger than allowed maximum */
+  SRC_WAITS_STATS,      /* Others have bad stats, selection postponed */
+  SRC_STALE,            /* Has older samples than others */
+  SRC_ORPHAN,           /* Has stratum equal or larger than orphan stratum */
+  SRC_UNTRUSTED,        /* Overlaps trusted sources */
+  SRC_FALSETICKER,      /* Doesn't agree with others */
+  SRC_WAITS_SOURCES,    /* Not enough sources, selection postponed */
+  SRC_NONPREFERRED,     /* Others have prefer option */
+  SRC_WAITS_UPDATE,     /* No updates, selection postponed */
+  SRC_DISTANT,          /* Others have shorter root distance */
+  SRC_OUTLIER,          /* Outlier in clustering (not used yet) */
+  SRC_UNSELECTED,       /* Used for synchronisation, not system peer */
+  SRC_SELECTED,         /* Used for synchronisation, selected as system peer */
+} SRC_Status;
+
+/* ================================================== */
+/* Define the instance structure used to hold information about each
+   source */
+struct SRC_Instance_Record {
+  SST_Stats stats;
+  int index;                    /* Index back into the array of source */
+  uint32_t ref_id;              /* The reference ID of this source
+                                   (i.e. from its IP address, NOT the
+                                   reference _it_ is sync'd to) */
+  IPAddr *ip_addr;              /* Its IP address if NTP source */
+
+  /* Flag indicating that the source is updating reachability */
+  int active;
+
+  /* Reachability register */
+  int reachability;
+
+  /* Number of set bits in the reachability register */
+  int reachability_size;
+
+  /* Updates since last reference update */
+  int updates;
+
+  /* Updates left before allowing combining */
+  int distant;
+
+  /* Updates with a status requiring source replacement */
+  int bad;
+
+  /* Flag indicating the status of the source */
+  SRC_Status status;
+
+  /* Type of the source */
+  SRC_Type type;
+
+  /* Flag indicating that the source is authenticated */
+  int authenticated;
+
+  /* Configured selection options */
+  int conf_sel_options;
+
+  /* Effective selection options */
+  int sel_options;
+
+  /* Score against currently selected source */
+  double sel_score;
+
+  struct SelectInfo sel_info;
+
+  /* Current stratum */
+  int stratum;
+
+  /* Current leap status */
+  NTP_Leap leap;
+
+  /* Flag indicating the source has a leap second vote */
+  int leap_vote;
+
+  /* Flag indicating the source was already reported as
+     a falseticker since the last selection change */
+  int reported_falseticker;
+};
+
+/* ================================================== */
+/* Structure used to build the sort list for finding falsetickers */
+struct Sort_Element {
+  int index;
+  double offset;
+  enum {
+    LOW = -1,
+    HIGH = 1
+  } tag;
+};
+
+/* ================================================== */
+/* Table of sources */
+static struct SRC_Instance_Record **sources;
+static struct Sort_Element *sort_list;
+static int *sel_sources;
+static int n_sources; /* Number of sources currently in the table */
+static int max_n_sources; /* Capacity of the table */
+
+#define INVALID_SOURCE (-1)
+static int selected_source_index; /* Which source index is currently
+                                     selected (set to INVALID_SOURCE
+                                     if no current valid reference) */
+static int reported_no_majority;  /* Flag to avoid repeated log message
+                                     about no majority */
+static int report_selection_loss; /* Flag to force logging a message if
+                                     selection is lost in a transient state
+                                     (SRC_WAITS_STATS, SRC_WAITS_UPDATE) */
+
+/* Score needed to replace the currently selected source */
+#define SCORE_LIMIT 10.0
+
+/* Number of updates needed to reset the distant status */
+#define DISTANT_PENALTY 32
+
+/* Number of updates needed to trigger handling of bad sources */
+#define BAD_HANDLE_THRESHOLD 4
+
+static double max_distance;
+static double max_jitter;
+static double reselect_distance;
+static double stratum_weight;
+static double combine_limit;
+
+static SRC_Instance last_updated_inst;
+
+static LOG_FileID logfileid;
+
+/* Identifier of the dump file */
+#define DUMP_IDENTIFIER "SRC0\n"
+
+/* ================================================== */
+/* Forward prototype */
+
+static void update_sel_options(void);
+static void unselect_selected_source(LOG_Severity severity, const char *format,
+                                     const char *arg);
+static void slew_sources(struct timespec *raw, struct timespec *cooked, double dfreq,
+                         double doffset, LCL_ChangeType change_type, void *anything);
+static void add_dispersion(double dispersion, void *anything);
+static char *source_to_string(SRC_Instance inst);
+static char get_status_char(SRC_Status status);
+
+/* ================================================== */
+/* Initialisation function */
+void SRC_Initialise(void) {
+  sources = NULL;
+  sort_list = NULL;
+  sel_sources = NULL;
+  n_sources = 0;
+  max_n_sources = 0;
+  selected_source_index = INVALID_SOURCE;
+  max_distance = CNF_GetMaxDistance();
+  max_jitter = CNF_GetMaxJitter();
+  reselect_distance = CNF_GetReselectDistance();
+  stratum_weight = CNF_GetStratumWeight();
+  combine_limit = CNF_GetCombineLimit();
+  initialised = 1;
+
+  LCL_AddParameterChangeHandler(slew_sources, NULL);
+  LCL_AddDispersionNotifyHandler(add_dispersion, NULL);
+
+  last_updated_inst = NULL;
+
+  logfileid = CNF_GetLogSelection() ? LOG_FileOpen("selection",
+              "   Date (UTC) Time     IP Address   S EOpts Reach Score Last sample  Low end   High end")
+              : -1;
+}
+
+/* ================================================== */
+/* Finalisation function */
+void SRC_Finalise(void)
+{
+  LCL_RemoveParameterChangeHandler(slew_sources, NULL);
+  LCL_RemoveDispersionNotifyHandler(add_dispersion, NULL);
+
+  Free(sources);
+  Free(sort_list);
+  Free(sel_sources);
+
+  initialised = 0;
+}
+
+/* ================================================== */
+/* Function to create a new instance.  This would be called by one of
+   the individual source-type instance creation routines. */
+
+SRC_Instance SRC_CreateNewInstance(uint32_t ref_id, SRC_Type type, int authenticated,
+                                   int sel_options, IPAddr *addr, int min_samples,
+                                   int max_samples, double min_delay, double asymmetry)
+{
+  SRC_Instance result;
+
+  assert(initialised);
+
+  if (min_samples == SRC_DEFAULT_MINSAMPLES)
+    min_samples = CNF_GetMinSamples();
+  if (max_samples == SRC_DEFAULT_MAXSAMPLES)
+    max_samples = CNF_GetMaxSamples();
+
+  result = MallocNew(struct SRC_Instance_Record);
+  result->stats = SST_CreateInstance(ref_id, addr, min_samples, max_samples,
+                                     min_delay, asymmetry);
+
+  if (n_sources == max_n_sources) {
+    /* Reallocate memory */
+    max_n_sources = max_n_sources > 0 ? 2 * max_n_sources : 4;
+    if (sources) {
+      sources = ReallocArray(struct SRC_Instance_Record *, max_n_sources, sources);
+      sort_list = ReallocArray(struct Sort_Element, 3*max_n_sources, sort_list);
+      sel_sources = ReallocArray(int, max_n_sources, sel_sources);
+    } else {
+      sources = MallocArray(struct SRC_Instance_Record *, max_n_sources);
+      sort_list = MallocArray(struct Sort_Element, 3*max_n_sources);
+      sel_sources = MallocArray(int, max_n_sources);
+    }
+  }
+
+  sources[n_sources] = result;
+
+  result->index = n_sources;
+  result->type = type;
+  result->authenticated = authenticated;
+  result->conf_sel_options = sel_options;
+  result->sel_options = sel_options;
+  result->active = 0;
+
+  SRC_SetRefid(result, ref_id, addr);
+  SRC_ResetInstance(result);
+
+  n_sources++;
+
+  update_sel_options();
+
+  return result;
+}
+
+/* ================================================== */
+/* Function to get rid of a source when it is being unconfigured.
+   This may cause the current reference source to be reselected, if this
+   was the reference source or contributed significantly to a
+   falseticker decision. */
+
+void SRC_DestroyInstance(SRC_Instance instance)
+{
+  int dead_index, i;
+
+  if (last_updated_inst == instance)
+    last_updated_inst = NULL;
+
+  assert(initialised);
+  if (instance->index < 0 || instance->index >= n_sources ||
+      instance != sources[instance->index])
+    assert(0);
+
+  SST_DeleteInstance(instance->stats);
+  dead_index = instance->index;
+  for (i=dead_index; i<n_sources-1; i++) {
+    sources[i] = sources[i+1];
+    sources[i]->index = i;
+  }
+  --n_sources;
+  Free(instance);
+
+  update_sel_options();
+
+  if (selected_source_index > dead_index)
+    --selected_source_index;
+  else if (selected_source_index == dead_index)
+    unselect_selected_source(LOGS_INFO, NULL, NULL);
+
+  SRC_SelectSource(NULL);
+}
+
+/* ================================================== */
+
+void
+SRC_ResetInstance(SRC_Instance instance)
+{
+  instance->updates = 0;
+  instance->reachability = 0;
+  instance->reachability_size = 0;
+  instance->distant = 0;
+  instance->bad = 0;
+  instance->status = SRC_BAD_STATS;
+  instance->sel_score = 1.0;
+  instance->stratum = 0;
+  instance->leap = LEAP_Unsynchronised;
+  instance->leap_vote = 0;
+  instance->reported_falseticker = 0;
+
+  memset(&instance->sel_info, 0, sizeof (instance->sel_info));
+
+  SST_ResetInstance(instance->stats);
+
+  if (selected_source_index == instance->index)
+    SRC_SelectSource(NULL);
+}
+
+/* ================================================== */
+
+void
+SRC_SetRefid(SRC_Instance instance, uint32_t ref_id, IPAddr *addr)
+{
+  instance->ref_id = ref_id;
+  instance->ip_addr = addr;
+  SST_SetRefid(instance->stats, ref_id, addr);
+}
+
+/* ================================================== */
+
+SST_Stats
+SRC_GetSourcestats(SRC_Instance instance)
+{
+  assert(initialised);
+  return instance->stats;
+}
+
+/* ================================================== */
+
+static NTP_Leap
+get_leap_status(void)
+{
+  int i, leap_votes, leap_ins, leap_del;
+
+  /* Accept a leap second if more than half of the sources with a vote agree */
+
+  for (i = leap_ins = leap_del = leap_votes = 0; i < n_sources; i++) {
+    if (!sources[i]->leap_vote)
+      continue;
+
+    leap_votes++;
+    if (sources[i]->leap == LEAP_InsertSecond)
+      leap_ins++;
+    else if (sources[i]->leap == LEAP_DeleteSecond)
+      leap_del++;
+  }
+
+  if (leap_ins > leap_votes / 2)
+    return LEAP_InsertSecond;
+  else if (leap_del > leap_votes / 2)
+    return LEAP_DeleteSecond;
+  else
+    return LEAP_Normal;
+}
+
+/* ================================================== */
+
+void
+SRC_UpdateStatus(SRC_Instance inst, int stratum, NTP_Leap leap)
+{
+  inst->stratum = stratum;
+
+  if (REF_IsLeapSecondClose(NULL, 0.0))
+    return;
+
+  inst->leap = leap;
+
+  if (inst->leap_vote)
+    REF_UpdateLeapStatus(get_leap_status());
+}
+
+/* ================================================== */
+
+/* This function is called by one of the source drivers when it has
+   a new sample that is to be accumulated.
+
+   This function causes the frequency estimation to be re-run for the
+   designated source, and the clock selection procedure to be re-run
+   afterwards.
+   */
+
+void
+SRC_AccumulateSample(SRC_Instance inst, NTP_Sample *sample)
+{
+
+  assert(initialised);
+
+  DEBUG_LOG("src=%s ts=%s offset=%e delay=%e disp=%e",
+            source_to_string(inst), UTI_TimespecToString(&sample->time), -sample->offset,
+            sample->root_delay, sample->root_dispersion);
+
+  if (REF_IsLeapSecondClose(&sample->time, sample->offset)) {
+    LOG(LOGS_INFO, "Dropping sample around leap second");
+    return;
+  }
+
+  SST_AccumulateSample(inst->stats, sample);
+  SST_DoNewRegression(inst->stats);
+}
+
+/* ================================================== */
+
+void
+SRC_SetActive(SRC_Instance inst)
+{
+  inst->active = 1;
+}
+
+/* ================================================== */
+
+void
+SRC_UnsetActive(SRC_Instance inst)
+{
+  inst->active = 0;
+}
+
+/* ================================================== */
+
+static int
+special_mode_end(void)
+{
+    int i;
+
+    for (i = 0; i < n_sources; i++) {
+      /* No updates from inactive sources */
+      if (!sources[i]->active)
+        continue;
+
+      /* Don't expect more updates than the initial burst of an NTP source */
+      if (sources[i]->reachability_size >= SOURCE_REACH_BITS - 1)
+        continue;
+
+      /* Check if the source could still have enough samples to be selectable */
+      if (SOURCE_REACH_BITS - 1 - sources[i]->reachability_size +
+            SST_Samples(sources[i]->stats) >= MIN_SAMPLES_FOR_REGRESS)
+        return 0;
+    }
+
+    return 1;
+}
+
+/* ================================================== */
+
+static void
+handle_bad_source(SRC_Instance inst)
+{
+  if (inst->type == SRC_NTP) {
+    DEBUG_LOG("Bad source status=%c", get_status_char(inst->status));
+    NSR_HandleBadSource(inst->ip_addr);
+  }
+}
+
+/* ================================================== */
+
+void
+SRC_UpdateReachability(SRC_Instance inst, int reachable)
+{
+  inst->reachability <<= 1;
+  inst->reachability |= !!reachable;
+  inst->reachability %= 1U << SOURCE_REACH_BITS;
+
+  if (inst->reachability_size < SOURCE_REACH_BITS)
+      inst->reachability_size++;
+
+  if (!reachable && inst->index == selected_source_index) {
+    /* Try to select a better source */
+    SRC_SelectSource(NULL);
+  }
+
+  /* Check if special reference update mode failed */
+  if (REF_GetMode() != REF_ModeNormal && special_mode_end()) {
+    REF_SetUnsynchronised();
+  }
+
+  /* Try to replace unreachable NTP sources */
+  if (inst->reachability == 0 && inst->reachability_size == SOURCE_REACH_BITS)
+    handle_bad_source(inst);
+}
+
+/* ================================================== */
+
+void
+SRC_ResetReachability(SRC_Instance inst)
+{
+  inst->reachability = 0;
+  inst->reachability_size = 0;
+  SRC_UpdateReachability(inst, 0);
+}
+
+/* ================================================== */
+
+static void
+update_sel_options(void)
+{
+  int options, auth_ntp_options, unauth_ntp_options, refclk_options;
+  int i, auth_ntp_sources, unauth_ntp_sources;
+
+  auth_ntp_sources = unauth_ntp_sources = 0;
+
+  for (i = 0; i < n_sources; i++) {
+    if (sources[i]->conf_sel_options & SRC_SELECT_NOSELECT)
+      continue;
+    if (sources[i]->type != SRC_NTP)
+      continue;
+    if (sources[i]->authenticated)
+      auth_ntp_sources++;
+    else
+      unauth_ntp_sources++;
+  }
+
+  auth_ntp_options = unauth_ntp_options = refclk_options = 0;
+
+  /* Determine which selection options need to be added to authenticated NTP
+     sources, unauthenticated NTP sources, and refclocks, to follow the
+     configured selection mode */
+  switch (CNF_GetAuthSelectMode()) {
+    case SRC_AUTHSELECT_IGNORE:
+      break;
+    case SRC_AUTHSELECT_MIX:
+      if (auth_ntp_sources > 0 && unauth_ntp_sources > 0)
+        auth_ntp_options = refclk_options = SRC_SELECT_REQUIRE | SRC_SELECT_TRUST;
+      break;
+    case SRC_AUTHSELECT_PREFER:
+      if (auth_ntp_sources > 0)
+        unauth_ntp_options = SRC_SELECT_NOSELECT;
+      break;
+    case SRC_AUTHSELECT_REQUIRE:
+      unauth_ntp_options = SRC_SELECT_NOSELECT;
+      break;
+    default:
+      assert(0);
+  }
+
+  for (i = 0; i < n_sources; i++) {
+    options = sources[i]->conf_sel_options;
+
+    if (!(options & SRC_SELECT_NOSELECT)) {
+      switch (sources[i]->type) {
+        case SRC_NTP:
+          options |= sources[i]->authenticated ? auth_ntp_options : unauth_ntp_options;
+          break;
+        case SRC_REFCLOCK:
+          options |= refclk_options;
+          break;
+        default:
+          assert(0);
+      }
+    }
+
+    if (sources[i]->sel_options != options) {
+      DEBUG_LOG("changing %s from %x to %x", source_to_string(sources[i]),
+                (unsigned int)sources[i]->sel_options, (unsigned int)options);
+      sources[i]->sel_options = options;
+    }
+  }
+}
+
+/* ================================================== */
+
+static void
+log_selection_message(LOG_Severity severity, const char *format, const char *arg)
+{
+  if (REF_GetMode() != REF_ModeNormal)
+    return;
+  LOG(severity, format, arg);
+}
+
+/* ================================================== */
+
+static void
+log_selection_source(LOG_Severity severity, const char *format, SRC_Instance inst)
+{
+  char buf[320], *name, *ntp_name;
+
+  name = source_to_string(inst);
+  ntp_name = inst->type == SRC_NTP ? NSR_GetName(inst->ip_addr) : NULL;
+
+  if (ntp_name && strcmp(name, ntp_name) != 0)
+    snprintf(buf, sizeof (buf), "%s (%s)", name, ntp_name);
+  else
+    snprintf(buf, sizeof (buf), "%s", name);
+
+  log_selection_message(severity, format, buf);
+}
+
+/* ================================================== */
+
+static int
+compare_sort_elements(const void *a, const void *b)
+{
+  const struct Sort_Element *u = (const struct Sort_Element *) a;
+  const struct Sort_Element *v = (const struct Sort_Element *) b;
+
+  if (u->offset < v->offset) {
+    return -1;
+  } else if (u->offset > v->offset) {
+    return +1;
+  } else if (u->tag < v->tag) {
+    return -1;
+  } else if (u->tag > v->tag) {
+    return +1;
+  } else {
+    return 0;
+  }
+}
+
+/* ================================================== */
+
+static char *
+source_to_string(SRC_Instance inst)
+{
+  switch (inst->type) {
+    case SRC_NTP:
+      return UTI_IPToString(inst->ip_addr);
+    case SRC_REFCLOCK:
+      return UTI_RefidToString(inst->ref_id);
+    default:
+      assert(0);
+  }
+  return NULL;
+}
+
+/* ================================================== */
+
+static void
+mark_source(SRC_Instance inst, SRC_Status status)
+{
+  struct timespec now;
+
+  inst->status = status;
+
+  /* Try to replace NTP sources that are falsetickers, or have a root
+     distance or jitter larger than the allowed maximums */
+  if (inst == last_updated_inst) {
+    if (inst->bad < INT_MAX &&
+        (status == SRC_FALSETICKER || status == SRC_BAD_DISTANCE || status == SRC_JITTERY))
+      inst->bad++;
+    else
+      inst->bad = 0;
+    if (inst->bad >= BAD_HANDLE_THRESHOLD)
+      handle_bad_source(inst);
+  }
+
+  DEBUG_LOG("%s status=%c options=%x reach=%o/%d updates=%d distant=%d bad=%d leap=%d vote=%d lo=%f hi=%f",
+            source_to_string(inst), get_status_char(inst->status),
+            (unsigned int)inst->sel_options, (unsigned int)inst->reachability,
+            inst->reachability_size, inst->updates,
+            inst->distant, inst->bad, (int)inst->leap, inst->leap_vote,
+            inst->sel_info.lo_limit, inst->sel_info.hi_limit);
+
+  if (logfileid == -1)
+    return;
+
+  SCH_GetLastEventTime(&now, NULL, NULL);
+
+  LOG_FileWrite(logfileid,
+                "%s %-15s %c -%c%c%c%c %4o %5.2f %10.3e %10.3e %10.3e",
+                UTI_TimeToLogForm(now.tv_sec), source_to_string(inst),
+                get_status_char(inst->status),
+                inst->sel_options & SRC_SELECT_NOSELECT ? 'N' : '-',
+                inst->sel_options & SRC_SELECT_PREFER ? 'P' : '-',
+                inst->sel_options & SRC_SELECT_TRUST ? 'T' : '-',
+                inst->sel_options & SRC_SELECT_REQUIRE ? 'R' : '-',
+                (unsigned int)inst->reachability, inst->sel_score,
+                inst->sel_info.last_sample_ago,
+                inst->sel_info.lo_limit, inst->sel_info.hi_limit);
+}
+
+/* ================================================== */
+
+static void
+mark_ok_sources(SRC_Status status)
+{
+  int i;
+
+  for (i = 0; i < n_sources; i++) {
+    if (sources[i]->status != SRC_OK)
+      continue;
+    mark_source(sources[i], status);
+  }
+}
+
+/* ================================================== */
+/* Reset the index of selected source and report the selection loss.  If no
+   message is provided, assume it is a transient state and wait for another
+   call providing a message or selection of another source, which resets the
+   report_selection_loss flag. */
+
+static void
+unselect_selected_source(LOG_Severity severity, const char *format, const char *arg)
+{
+  if (selected_source_index != INVALID_SOURCE) {
+    selected_source_index = INVALID_SOURCE;
+    report_selection_loss = 1;
+  }
+
+  if (report_selection_loss && format) {
+    log_selection_message(severity, format, arg);
+    report_selection_loss = 0;
+  }
+}
+
+/* ================================================== */
+
+static int
+combine_sources(int n_sel_sources, struct timespec *ref_time, double *offset,
+                double *offset_sd, double *frequency, double *frequency_sd, double *skew)
+{
+  struct timespec src_ref_time;
+  double src_offset, src_offset_sd, src_frequency, src_frequency_sd, src_skew;
+  double src_root_delay, src_root_dispersion, sel_src_distance, elapsed;
+  double offset_weight, sum_offset_weight, sum_offset, sum2_offset_sd;
+  double frequency_weight, sum_frequency_weight, sum_frequency;
+  double inv_sum2_frequency_sd, inv_sum2_skew;
+  int i, index, combined;
+
+  if (n_sel_sources == 1)
+    return 1;
+
+  sum_offset_weight = sum_offset = sum2_offset_sd = 0.0;
+  sum_frequency_weight = sum_frequency = inv_sum2_frequency_sd = inv_sum2_skew = 0.0;
+
+  sel_src_distance = sources[selected_source_index]->sel_info.root_distance;
+  if (sources[selected_source_index]->type == SRC_NTP)
+    sel_src_distance += reselect_distance;
+
+  for (i = combined = 0; i < n_sel_sources; i++) {
+    index = sel_sources[i];
+    SST_GetTrackingData(sources[index]->stats, &src_ref_time,
+                        &src_offset, &src_offset_sd,
+                        &src_frequency, &src_frequency_sd, &src_skew,
+                        &src_root_delay, &src_root_dispersion);
+
+    /* Don't include this source if its distance is longer than the distance of
+       the selected source multiplied by the limit, their estimated frequencies
+       are not close, or it was recently marked as distant */
+
+    if (index != selected_source_index &&
+        (sources[index]->sel_info.root_distance > combine_limit * sel_src_distance ||
+         fabs(*frequency - src_frequency) >
+           combine_limit * (*skew + src_skew + LCL_GetMaxClockError()))) {
+      /* Use a smaller penalty in first few updates */
+      sources[index]->distant = sources[index]->reachability_size >= SOURCE_REACH_BITS ?
+                                DISTANT_PENALTY : 1;
+    } else if (sources[index]->distant) {
+      sources[index]->distant--;
+    }
+
+    if (sources[index]->distant) {
+      mark_source(sources[index], SRC_DISTANT);
+      continue;
+    }
+
+    if (sources[index]->status == SRC_OK)
+      mark_source(sources[index], SRC_UNSELECTED);
+
+    elapsed = UTI_DiffTimespecsToDouble(ref_time, &src_ref_time);
+    src_offset += elapsed * src_frequency;
+    src_offset_sd += elapsed * src_frequency_sd;
+    offset_weight = 1.0 / sources[index]->sel_info.root_distance;
+    frequency_weight = 1.0 / SQUARE(src_frequency_sd);
+
+    DEBUG_LOG("combining %s oweight=%e offset=%e osd=%e fweight=%e freq=%e fsd=%e skew=%e",
+              source_to_string(sources[index]), offset_weight, src_offset, src_offset_sd,
+              frequency_weight, src_frequency, src_frequency_sd, src_skew);
+
+    sum_offset_weight += offset_weight;
+    sum_offset += offset_weight * src_offset;
+    sum2_offset_sd += offset_weight * (SQUARE(src_offset_sd) +
+                                       SQUARE(src_offset - *offset));
+
+    sum_frequency_weight += frequency_weight;
+    sum_frequency += frequency_weight * src_frequency;
+    inv_sum2_frequency_sd += 1.0 / SQUARE(src_frequency_sd);
+    inv_sum2_skew += 1.0 / SQUARE(src_skew);
+
+    combined++;
+  }
+
+  assert(combined);
+  *offset = sum_offset / sum_offset_weight;
+  *offset_sd = sqrt(sum2_offset_sd / sum_offset_weight);
+  *frequency = sum_frequency / sum_frequency_weight;
+  *frequency_sd = 1.0 / sqrt(inv_sum2_frequency_sd);
+  *skew = 1.0 / sqrt(inv_sum2_skew);
+
+  DEBUG_LOG("combined result offset=%e osd=%e freq=%e fsd=%e skew=%e",
+            *offset, *offset_sd, *frequency, *frequency_sd, *skew);
+
+  return combined;
+}
+
+/* ================================================== */
+/* This function selects the current reference from amongst the pool
+   of sources we are holding and updates the local reference */
+
+void
+SRC_SelectSource(SRC_Instance updated_inst)
+{
+  struct SelectInfo *si;
+  struct timespec now, ref_time;
+  int i, j, j1, j2, index, sel_prefer, n_endpoints, n_sel_sources, sel_req_source;
+  int n_badstats_sources, max_sel_reach, max_sel_reach_size, max_badstat_reach;
+  int depth, best_depth, trust_depth, best_trust_depth, n_sel_trust_sources;
+  int combined, stratum, min_stratum, max_score_index;
+  int orphan_stratum, orphan_source;
+  double src_offset, src_offset_sd, src_frequency, src_frequency_sd, src_skew;
+  double src_root_delay, src_root_dispersion;
+  double best_lo, best_hi, distance, sel_src_distance, max_score;
+  double best_trust_lo, best_trust_hi;
+  double first_sample_ago, max_reach_sample_ago;
+  NTP_Leap leap_status;
+
+  if (updated_inst) {
+    updated_inst->updates++;
+    last_updated_inst = updated_inst;
+  }
+
+  if (n_sources == 0) {
+    unselect_selected_source(LOGS_INFO, "Can't synchronise: no sources", NULL);
+    return;
+  }
+
+  /* This is accurate enough and cheaper than calling LCL_ReadCookedTime */
+  SCH_GetLastEventTime(&now, NULL, NULL);
+
+  /* Step 1 - build intervals about each source */
+
+  n_endpoints = 0;
+  n_sel_sources = n_sel_trust_sources = 0;
+  n_badstats_sources = 0;
+  sel_req_source = 0;
+  max_sel_reach = max_badstat_reach = 0;
+  max_sel_reach_size = 0;
+  max_reach_sample_ago = 0.0;
+
+  for (i = 0; i < n_sources; i++) {
+    assert(sources[i]->status != SRC_OK);
+
+    /* Don't allow the source to vote on leap seconds unless it's selectable */
+    sources[i]->leap_vote = 0;
+
+    /* If some sources are specified with the require option, at least one
+       of them will have to be selectable in order to update the clock */
+    if (sources[i]->sel_options & SRC_SELECT_REQUIRE)
+      sel_req_source = 1;
+
+    /* Ignore sources which were added with the noselect option */
+    if (sources[i]->sel_options & SRC_SELECT_NOSELECT) {
+      mark_source(sources[i], SRC_UNSELECTABLE);
+      continue;
+    }
+
+    /* Ignore sources which are not synchronised */
+    if (sources[i]->leap == LEAP_Unsynchronised) {
+      mark_source(sources[i], SRC_UNSYNCHRONISED);
+      continue;
+    }
+
+    si = &sources[i]->sel_info;
+    SST_GetSelectionData(sources[i]->stats, &now,
+                         &si->lo_limit, &si->hi_limit, &si->root_distance,
+                         &si->std_dev, &first_sample_ago,
+                         &si->last_sample_ago, &si->select_ok);
+
+    if (!si->select_ok) {
+      ++n_badstats_sources;
+      mark_source(sources[i], SRC_BAD_STATS);
+      if (max_badstat_reach < sources[i]->reachability)
+        max_badstat_reach = sources[i]->reachability;
+      continue;
+    }
+
+    /* Include extra dispersion in the root distance of sources that don't
+       have new samples (the last sample is older than span of all samples) */
+    if (first_sample_ago < 2.0 * si->last_sample_ago) {
+      double extra_disp = LCL_GetMaxClockError() *
+                          (2.0 * si->last_sample_ago - first_sample_ago);
+      si->root_distance += extra_disp;
+      si->lo_limit -= extra_disp;
+      si->hi_limit += extra_disp;
+    }
+
+    /* Require the root distance to be below the allowed maximum and the
+       endpoints to be in the right order (i.e. a non-negative distance) */
+    if (!(si->root_distance <= max_distance && si->lo_limit <= si->hi_limit)) {
+      mark_source(sources[i], SRC_BAD_DISTANCE);
+      continue;
+    }
+
+    /* And the same applies for the estimated standard deviation */
+    if (si->std_dev > max_jitter) {
+      mark_source(sources[i], SRC_JITTERY);
+      continue;
+    }
+
+    sources[i]->status = SRC_OK; /* For now */
+
+    if (sources[i]->reachability && max_reach_sample_ago < first_sample_ago)
+      max_reach_sample_ago = first_sample_ago;
+
+    if (max_sel_reach < sources[i]->reachability)
+      max_sel_reach = sources[i]->reachability;
+
+    if (max_sel_reach_size < sources[i]->reachability_size)
+      max_sel_reach_size = sources[i]->reachability_size;
+  }
+
+  orphan_stratum = REF_GetOrphanStratum();
+  orphan_source = INVALID_SOURCE;
+
+  for (i = 0; i < n_sources; i++) {
+    if (sources[i]->status != SRC_OK)
+      continue;
+
+    si = &sources[i]->sel_info;
+
+    /* Reachability is not a requirement for selection.  An unreachable source
+       can still be selected if its newest sample is not older than the oldest
+       sample from reachable sources. */
+    if (!sources[i]->reachability && max_reach_sample_ago < si->last_sample_ago) {
+      mark_source(sources[i], SRC_STALE);
+      continue;
+    }
+
+    /* When the local reference is configured with the orphan option, NTP
+       sources that have stratum equal to the configured local stratum are
+       considered to be orphans (i.e. serving local time while not being
+       synchronised with real time) and are excluded from the normal source
+       selection.  Sources with stratum larger than the local stratum are
+       considered to be directly on indirectly synchronised to an orphan and
+       are always ignored.
+
+       If no selectable source is available and all orphan sources have
+       reference IDs larger than the local ID, no source will be selected and
+       the local reference mode will be activated at some point, i.e. this host
+       will become an orphan.  Otherwise, the orphan source with the smallest
+       reference ID will be selected.  This ensures a group of servers polling
+       each other (with the same orphan configuration) which have no external
+       source can settle down to a state where only one server is serving its
+       local unsychronised time and others are synchronised to it. */
+
+    if (sources[i]->stratum >= orphan_stratum && sources[i]->type == SRC_NTP) {
+      mark_source(sources[i], SRC_ORPHAN);
+
+      if (sources[i]->stratum == orphan_stratum && sources[i]->reachability &&
+          (orphan_source == INVALID_SOURCE ||
+           sources[i]->ref_id < sources[orphan_source]->ref_id))
+        orphan_source = i;
+
+      continue;
+    }
+
+    ++n_sel_sources;
+  }
+
+  /* If no selectable source is available, consider the orphan source */
+  if (!n_sel_sources && orphan_source != INVALID_SOURCE) {
+    uint32_t local_ref_id = NSR_GetLocalRefid(sources[orphan_source]->ip_addr);
+
+    if (!local_ref_id) {
+      LOG(LOGS_ERR, "Unknown local refid in orphan mode");
+    } else if (sources[orphan_source]->ref_id < local_ref_id) {
+      sources[orphan_source]->status = SRC_OK;
+      n_sel_sources = 1;
+      DEBUG_LOG("selecting orphan refid=%"PRIx32, sources[orphan_source]->ref_id);
+    }
+  }
+
+  for (i = 0; i < n_sources; i++) {
+    if (sources[i]->status != SRC_OK)
+      continue;
+
+    if (sources[i]->sel_options & SRC_SELECT_TRUST)
+      n_sel_trust_sources++;
+
+    si = &sources[i]->sel_info;
+
+    j1 = n_endpoints;
+    j2 = j1 + 1;
+
+    sort_list[j1].index = i;
+    sort_list[j1].offset = si->lo_limit;
+    sort_list[j1].tag = LOW;
+
+    sort_list[j2].index = i;
+    sort_list[j2].offset = si->hi_limit;
+    sort_list[j2].tag = HIGH;
+
+    n_endpoints += 2;
+  }
+
+  DEBUG_LOG("badstat=%d sel=%d badstat_reach=%o sel_reach=%o size=%d max_reach_ago=%f",
+            n_badstats_sources, n_sel_sources, (unsigned int)max_badstat_reach,
+            (unsigned int)max_sel_reach, max_sel_reach_size, max_reach_sample_ago);
+
+  /* Wait for the next call if we have no source selected and there is
+     a source with bad stats (has less than 3 samples) with reachability
+     equal to shifted maximum reachability of sources with valid stats.
+     This delays selecting source on start with servers using the same
+     polling interval until they all have valid stats. */
+  if (n_badstats_sources && n_sel_sources && selected_source_index == INVALID_SOURCE &&
+      max_sel_reach_size < SOURCE_REACH_BITS && max_sel_reach >> 1 == max_badstat_reach) {
+    mark_ok_sources(SRC_WAITS_STATS);
+    unselect_selected_source(LOGS_INFO, NULL, NULL);
+    return;
+  }
+
+  if (n_endpoints == 0) {
+    /* No sources provided valid endpoints */
+    unselect_selected_source(LOGS_INFO, "Can't synchronise: no selectable sources", NULL);
+    return;
+  }
+
+  /* Now sort the endpoint list */
+  qsort((void *) sort_list, n_endpoints, sizeof(struct Sort_Element), compare_sort_elements);
+
+  /* Now search for the interval which is contained in the most
+     individual source intervals.  Any source which overlaps this
+     will be a candidate.
+
+     If we get a case like
+
+     <----------------------->
+         <-->
+                  <-->
+         <===========>
+
+     we will build the interval as shown with '=', whereas with an extra source we get
+
+     <----------------------->
+        <------->
+         <-->
+                  <-->
+         <==>
+
+     The first case is just bad luck - we need extra sources to
+     detect the falseticker, so just make an arbitrary choice based
+     on stratum & stability etc.
+
+     Intervals from sources specified with the trust option have higher
+     priority in the search.
+     */
+
+  trust_depth = best_trust_depth = 0;
+  depth = best_depth = 0;
+  best_lo = best_hi = best_trust_lo = best_trust_hi = 0.0;
+
+  for (i = 0; i < n_endpoints; i++) {
+    switch (sort_list[i].tag) {
+      case LOW:
+        depth++;
+        if (sources[sort_list[i].index]->sel_options & SRC_SELECT_TRUST)
+          trust_depth++;
+        if (trust_depth > best_trust_depth ||
+            (trust_depth == best_trust_depth && depth > best_depth)) {
+          if (trust_depth > best_trust_depth) {
+            best_trust_depth = trust_depth;
+            best_trust_lo = sort_list[i].offset;
+          }
+          best_depth = depth;
+          best_lo = sort_list[i].offset;
+        }
+        break;
+      case HIGH:
+        if (trust_depth == best_trust_depth) {
+          if (depth == best_depth)
+            best_hi = sort_list[i].offset;
+          best_trust_hi = sort_list[i].offset;
+        }
+        if (sources[sort_list[i].index]->sel_options & SRC_SELECT_TRUST)
+          trust_depth--;
+        depth--;
+        break;
+      default:
+        assert(0);
+    }
+    assert(trust_depth <= depth);
+    assert(trust_depth >= 0);
+  }
+
+  assert(depth == 0 && trust_depth == 0);
+  assert(2 * n_sel_sources == n_endpoints);
+
+  if ((best_trust_depth == 0 && best_depth <= n_sel_sources / 2) ||
+      (best_trust_depth > 0 && best_trust_depth <= n_sel_trust_sources / 2)) {
+    /* Could not even get half the reachable (trusted) sources to agree */
+
+    if (!reported_no_majority) {
+      log_selection_message(LOGS_WARN, "Can't synchronise: no majority", NULL);
+      reported_no_majority = 1;
+      report_selection_loss = 0;
+    }
+
+    if (selected_source_index != INVALID_SOURCE) {
+      REF_SetUnsynchronised();
+      selected_source_index = INVALID_SOURCE;
+    }
+
+    /* .. and mark all sources as falsetickers (so they appear thus
+       on the outputs from the command client) */
+    mark_ok_sources(SRC_FALSETICKER);
+
+    return;
+  }
+
+  /* We have our interval, now work out which source are in it,
+     i.e. build list of admissible sources. */
+
+  n_sel_sources = 0;
+
+  for (i = 0; i < n_sources; i++) {
+    /* This should be the same condition to get into the endpoint
+       list */
+    if (sources[i]->status != SRC_OK)
+      continue;
+
+    /* Check if source's interval contains the best interval, or is wholly
+       contained within it.  If there are any trusted sources, other sources
+       are required to be wholly contained within the best interval of the
+       trusted sources to not allow non-trusted sources to move the final
+       offset outside the trusted interval. */
+    if ((sources[i]->sel_info.lo_limit <= best_lo &&
+         sources[i]->sel_info.hi_limit >= best_hi) ||
+        (sources[i]->sel_info.lo_limit >= best_lo &&
+         sources[i]->sel_info.hi_limit <= best_hi)) {
+
+      if (!(best_trust_depth == 0 || (sources[i]->sel_options & SRC_SELECT_TRUST) ||
+            (sources[i]->sel_info.lo_limit >= best_trust_lo &&
+             sources[i]->sel_info.hi_limit <= best_trust_hi))) {
+        mark_source(sources[i], SRC_UNTRUSTED);
+        continue;
+      }
+
+      sel_sources[n_sel_sources++] = i;
+
+      if (sources[i]->sel_options & SRC_SELECT_REQUIRE)
+        sel_req_source = 0;
+    } else {
+      mark_source(sources[i], SRC_FALSETICKER);
+      if (!sources[i]->reported_falseticker) {
+        log_selection_source(LOGS_WARN, "Detected falseticker %s", sources[i]);
+        sources[i]->reported_falseticker = 1;
+      }
+    }
+  }
+
+  if (!n_sel_sources || sel_req_source || n_sel_sources < CNF_GetMinSources()) {
+    unselect_selected_source(LOGS_INFO, "Can't synchronise: %s selectable sources",
+                             !n_sel_sources ? "no" :
+                             sel_req_source ? "no required source in" : "not enough");
+    mark_ok_sources(SRC_WAITS_SOURCES);
+    return;
+  }
+
+  /* Enable the selectable sources (and trusted if there are any) to
+     vote on leap seconds */
+  for (i = 0; i < n_sel_sources; i++) {
+    index = sel_sources[i];
+    if (best_trust_depth && !(sources[index]->sel_options & SRC_SELECT_TRUST))
+      continue;
+    sources[index]->leap_vote = 1;
+  }
+
+  /* If there are any sources with prefer option, reduce the list again
+     only to the preferred sources */
+  for (i = 0; i < n_sel_sources; i++) {
+    if (sources[sel_sources[i]]->sel_options & SRC_SELECT_PREFER)
+      break;
+  }
+  if (i < n_sel_sources) {
+    for (i = j = 0; i < n_sel_sources; i++) {
+      if (!(sources[sel_sources[i]]->sel_options & SRC_SELECT_PREFER))
+        mark_source(sources[sel_sources[i]], SRC_NONPREFERRED);
+      else
+        sel_sources[j++] = sel_sources[i];
+    }
+    assert(j > 0);
+    n_sel_sources = j;
+    sel_prefer = 1;
+  } else {
+    sel_prefer = 0;
+  }
+
+  /* Find minimum stratum */
+
+  index = sel_sources[0];
+  min_stratum = sources[index]->stratum;
+  for (i = 1; i < n_sel_sources; i++) {
+    index = sel_sources[i];
+    stratum = sources[index]->stratum;
+    if (stratum < min_stratum)
+      min_stratum = stratum;
+  }
+
+  /* Update scores and find the source with maximum score */
+
+  max_score_index = INVALID_SOURCE;
+  max_score = 0.0;
+  sel_src_distance = 0.0;
+
+  if (selected_source_index != INVALID_SOURCE)
+    sel_src_distance = sources[selected_source_index]->sel_info.root_distance +
+      (sources[selected_source_index]->stratum - min_stratum) * stratum_weight;
+
+  for (i = 0; i < n_sources; i++) {
+    /* Reset score for non-selectable sources */
+    if (sources[i]->status != SRC_OK ||
+        (sel_prefer && !(sources[i]->sel_options & SRC_SELECT_PREFER))) {
+      sources[i]->sel_score = 1.0;
+      sources[i]->distant = DISTANT_PENALTY;
+      continue;
+    }
+
+    distance = sources[i]->sel_info.root_distance +
+      (sources[i]->stratum - min_stratum) * stratum_weight;
+    if (sources[i]->type == SRC_NTP)
+      distance += reselect_distance;
+
+    if (selected_source_index != INVALID_SOURCE) {
+      /* Update score, but only for source pairs where one source
+         has a new sample */
+      if (sources[i] == updated_inst ||
+          sources[selected_source_index] == updated_inst) {
+
+        sources[i]->sel_score *= sel_src_distance / distance;
+
+        if (sources[i]->sel_score < 1.0)
+          sources[i]->sel_score = 1.0;
+      }
+    } else {
+      /* When there is no selected source yet, assign scores so that the
+         source with minimum distance will have maximum score.  The scores
+         will be reset when the source is selected later in this function. */
+      sources[i]->sel_score = 1.0 / distance;
+    }
+
+    DEBUG_LOG("%s score=%f dist=%f",
+              source_to_string(sources[i]), sources[i]->sel_score, distance);
+
+    if (max_score < sources[i]->sel_score) {
+      max_score = sources[i]->sel_score;
+      max_score_index = i;
+    }
+  }
+
+  assert(max_score_index != INVALID_SOURCE);
+
+  /* Is the current source still a survivor and no other source has reached
+     the score limit? */
+  if (selected_source_index == INVALID_SOURCE ||
+      sources[selected_source_index]->status != SRC_OK ||
+      (max_score_index != selected_source_index && max_score > SCORE_LIMIT)) {
+
+    /* Before selecting the new synchronisation source wait until the reference
+       can be updated */
+    if (sources[max_score_index]->updates == 0) {
+      unselect_selected_source(LOGS_INFO, NULL, NULL);
+      mark_ok_sources(SRC_WAITS_UPDATE);
+      return;
+    }
+
+    selected_source_index = max_score_index;
+    log_selection_source(LOGS_INFO, "Selected source %s", sources[selected_source_index]);
+
+    /* New source has been selected, reset all scores */
+    for (i = 0; i < n_sources; i++) {
+      sources[i]->sel_score = 1.0;
+      sources[i]->distant = 0;
+      sources[i]->reported_falseticker = 0;
+    }
+
+    reported_no_majority = 0;
+    report_selection_loss = 0;
+  }
+
+  mark_source(sources[selected_source_index], SRC_SELECTED);
+
+  /* Don't update reference when the selected source has no new samples */
+
+  if (sources[selected_source_index]->updates == 0) {
+    /* Mark the remaining sources as last combine_sources() call */
+
+    for (i = 0; i < n_sel_sources; i++) {
+      index = sel_sources[i];
+      if (sources[index]->status == SRC_OK)
+        mark_source(sources[index], sources[index]->distant ? SRC_DISTANT : SRC_UNSELECTED);
+    }
+    return;
+  }
+
+  for (i = 0; i < n_sources; i++)
+    sources[i]->updates = 0;
+
+  leap_status = get_leap_status();
+
+  /* Now just use the statistics of the selected source combined with
+     the other selectable sources for trimming the local clock */
+
+  SST_GetTrackingData(sources[selected_source_index]->stats, &ref_time,
+                      &src_offset, &src_offset_sd,
+                      &src_frequency, &src_frequency_sd, &src_skew,
+                      &src_root_delay, &src_root_dispersion);
+
+  combined = combine_sources(n_sel_sources, &ref_time, &src_offset, &src_offset_sd,
+                             &src_frequency, &src_frequency_sd, &src_skew);
+
+  REF_SetReference(sources[selected_source_index]->stratum,
+                   leap_status, combined,
+                   sources[selected_source_index]->ref_id,
+                   sources[selected_source_index]->ip_addr,
+                   &ref_time, src_offset, src_offset_sd,
+                   src_frequency, src_frequency_sd, src_skew,
+                   src_root_delay, src_root_dispersion);
+}
+
+/* ================================================== */
+/* Force reselecting the best source */
+
+void
+SRC_ReselectSource(void)
+{
+  selected_source_index = INVALID_SOURCE;
+  SRC_SelectSource(NULL);
+}
+
+/* ================================================== */
+
+void
+SRC_SetReselectDistance(double distance)
+{
+  if (reselect_distance != distance) {
+    reselect_distance = distance;
+    LOG(LOGS_INFO, "New reselect distance %f", distance);
+  }
+}
+
+/* ================================================== */
+/* This routine is registered as a callback with the local clock
+   module, to be called whenever the local clock changes frequency or
+   is slewed.  It runs through all the existing source statistics, and
+   adjusts them to make them look as though they were sampled under
+   the new regime. */
+
+static void
+slew_sources(struct timespec *raw, struct timespec *cooked, double dfreq,
+             double doffset, LCL_ChangeType change_type, void *anything)
+{
+  int i;
+
+  for (i=0; i<n_sources; i++) {
+    if (change_type == LCL_ChangeUnknownStep) {
+      SST_ResetInstance(sources[i]->stats);
+    } else {
+      SST_SlewSamples(sources[i]->stats, cooked, dfreq, doffset);
+    }
+  }
+
+  if (change_type == LCL_ChangeUnknownStep) {
+    /* Update selection status */
+    SRC_SelectSource(NULL);
+  }
+}
+
+/* ================================================== */
+/* This routine is called when an indeterminate offset is introduced
+   into the local time. */
+
+static void
+add_dispersion(double dispersion, void *anything)
+{
+  int i;
+
+  for (i = 0; i < n_sources; i++) {
+    SST_AddDispersion(sources[i]->stats, dispersion);
+  }
+}
+
+/* ================================================== */
+
+static int
+get_dumpfile(SRC_Instance inst, char *filename, size_t len)
+{
+  /* Use the IP address, or reference ID with reference clocks */
+  switch (inst->type) {
+    case SRC_NTP:
+      if (!UTI_IsIPReal(inst->ip_addr) ||
+          snprintf(filename, len, "%s", source_to_string(inst)) >= len)
+        return 0;
+      break;
+    case SRC_REFCLOCK:
+      if (snprintf(filename, len, "refid:%08"PRIx32, inst->ref_id) >= len)
+        return 0;
+      break;
+    default:
+      assert(0);
+  }
+
+  return 1;
+}
+
+/* ================================================== */
+
+static void
+save_source(SRC_Instance inst)
+{
+  char filename[64], *dumpdir, *ntp_name;
+  FILE *f;
+
+  dumpdir = CNF_GetDumpDir();
+  if (!dumpdir)
+    return;
+
+  if (!get_dumpfile(inst, filename, sizeof (filename)))
+    return;
+
+  f = UTI_OpenFile(dumpdir, filename, ".dat", 'w', 0644);
+  if (!f)
+    return;
+
+  ntp_name = inst->type == SRC_NTP ? NSR_GetName(inst->ip_addr) : ".";
+
+  if (fprintf(f, "%s%s\n%d %o %d %d %d\n",
+              DUMP_IDENTIFIER, ntp_name, inst->authenticated,
+              (unsigned int)inst->reachability, inst->reachability_size,
+              inst->stratum, (int)inst->leap) < 0 ||
+      !SST_SaveToFile(inst->stats, f)) {
+    fclose(f);
+    if (!UTI_RemoveFile(dumpdir, filename, ".dat"))
+      ;
+    return;
+  }
+
+  fclose(f);
+}
+
+/* ================================================== */
+/* This is called to dump out the source measurement registers */
+
+void
+SRC_DumpSources(void)
+{
+  int i;
+
+  for (i = 0; i < n_sources; i++)
+    save_source(sources[i]);
+}
+
+/* ================================================== */
+
+#define MAX_WORDS 1
+
+static void
+load_source(SRC_Instance inst)
+{
+  char filename[64], line[256], *dumpdir, *ntp_name, *words[MAX_WORDS];
+  int auth, leap, reach_size, stratum;
+  unsigned int reach;
+  FILE *f;
+
+  dumpdir = CNF_GetDumpDir();
+  if (!dumpdir)
+    return;
+
+  if (!get_dumpfile(inst, filename, sizeof (filename)))
+    return;
+
+  f = UTI_OpenFile(dumpdir, filename, ".dat", 'r', 0);
+  if (!f)
+    return;
+
+  ntp_name = inst->type == SRC_NTP ? NSR_GetName(inst->ip_addr) : NULL;
+
+  if (!fgets(line, sizeof (line), f) || strcmp(line, DUMP_IDENTIFIER) != 0 ||
+      !fgets(line, sizeof (line), f) || UTI_SplitString(line, words, MAX_WORDS) != 1 ||
+        (inst->type == SRC_NTP && (!ntp_name || strcmp(words[0], ntp_name) != 0)) ||
+      !fgets(line, sizeof (line), f) ||
+        sscanf(words[0], "%d %o %d %d %d",
+               &auth, &reach, &reach_size, &stratum, &leap) != 5 ||
+        (!auth && inst->authenticated) ||
+        stratum < 0 || stratum >= NTP_MAX_STRATUM ||
+        leap < LEAP_Normal || leap >= LEAP_Unsynchronised ||
+      !SST_LoadFromFile(inst->stats, f)) {
+    LOG(LOGS_WARN, "Could not load dump file for %s", source_to_string(inst));
+    fclose(f);
+    return;
+  }
+
+  inst->reachability = reach & ((1U << SOURCE_REACH_BITS) - 1);
+  inst->reachability_size = CLAMP(0, reach_size, SOURCE_REACH_BITS);
+  inst->stratum = stratum;
+  inst->leap = leap;
+
+  LOG(LOGS_INFO, "Loaded dump file for %s", source_to_string(inst));
+
+  fclose(f);
+}
+
+/* ================================================== */
+
+void
+SRC_ReloadSources(void)
+{
+  int i;
+
+  for (i = 0; i < n_sources; i++) {
+    load_source(sources[i]);
+
+    /* Allow an immediate update of the reference */
+    sources[i]->updates++;
+  }
+
+  /* Select sources and set the reference */
+  SRC_SelectSource(NULL);
+}
+
+/* ================================================== */
+
+void
+SRC_RemoveDumpFiles(void)
+{
+  char pattern[PATH_MAX], name[64], *dumpdir, *s;
+  IPAddr ip_addr;
+  glob_t gl;
+  size_t i;
+
+  dumpdir = CNF_GetDumpDir();
+  if (!dumpdir ||
+      snprintf(pattern, sizeof (pattern), "%s/*.dat", dumpdir) >= sizeof (pattern))
+    return;
+
+  if (glob(pattern, 0, NULL, &gl))
+    return;
+
+  for (i = 0; i < gl.gl_pathc; i++) {
+    s = strrchr(gl.gl_pathv[i], '/');
+    if (!s || snprintf(name, sizeof (name), "%s", s + 1) >= sizeof (name))
+      continue;
+
+    /* Remove .dat extension */
+    if (strlen(name) < 4)
+      continue;
+    name[strlen(name) - 4] = '\0';
+
+    /* Check if it looks like name of an actual dump file */
+    if (strncmp(name, "refid:", 6) && !UTI_StringToIP(name, &ip_addr))
+      continue;
+
+    if (!UTI_RemoveFile(NULL, gl.gl_pathv[i], NULL))
+      ;
+  }
+
+  globfree(&gl);
+}
+
+/* ================================================== */
+
+void
+SRC_ResetSources(void)
+{
+  int i;
+
+  for (i = 0; i < n_sources; i++)
+    SRC_ResetInstance(sources[i]);
+
+  LOG(LOGS_INFO, "Reset all sources");
+}
+
+/* ================================================== */
+
+int
+SRC_IsSyncPeer(SRC_Instance inst)
+{
+  if (inst->index == selected_source_index) {
+    return 1;
+  } else {
+    return 0;
+  }
+
+}
+
+/* ================================================== */
+
+int
+SRC_IsReachable(SRC_Instance inst)
+{
+  return inst->reachability != 0;
+}
+
+/* ================================================== */
+
+int
+SRC_ReadNumberOfSources(void)
+{
+  return n_sources;
+}
+
+/* ================================================== */
+
+int
+SRC_ActiveSources(void)
+{
+  int i, r;
+
+  for (i = r = 0; i < n_sources; i++)
+    if (sources[i]->active)
+      r++;
+
+  return r;
+}
+
+/* ================================================== */
+
+static SRC_Instance
+find_source(IPAddr *ip, uint32_t ref_id)
+{
+  int i;
+
+  for (i = 0; i < n_sources; i++) {
+    if ((ip->family != IPADDR_UNSPEC && sources[i]->type == SRC_NTP &&
+         UTI_CompareIPs(ip, sources[i]->ip_addr, NULL) == 0) ||
+        (ip->family == IPADDR_UNSPEC && sources[i]->type == SRC_REFCLOCK &&
+         ref_id == sources[i]->ref_id))
+      return sources[i];
+  }
+
+  return NULL;
+}
+
+/* ================================================== */
+
+int
+SRC_ModifySelectOptions(IPAddr *ip, uint32_t ref_id, int options, int mask)
+{
+  SRC_Instance inst;
+
+  inst = find_source(ip, ref_id);
+  if (!inst)
+    return 0;
+
+  if ((inst->conf_sel_options & mask) == options)
+    return 1;
+
+  inst->conf_sel_options = (inst->conf_sel_options & ~mask) | options;
+  LOG(LOGS_INFO, "Source %s selection options modified", source_to_string(inst));
+
+  update_sel_options();
+
+  return 1;
+}
+
+/* ================================================== */
+
+int
+SRC_ReportSource(int index, RPT_SourceReport *report, struct timespec *now)
+{
+  SRC_Instance src;
+  if ((index >= n_sources) || (index < 0)) {
+    return 0;
+  } else {
+    src = sources[index];
+
+    if (src->ip_addr)
+      report->ip_addr = *src->ip_addr;
+    else {
+      /* Use refid as an address */
+      report->ip_addr.addr.in4 = src->ref_id;
+      report->ip_addr.family = IPADDR_INET4;
+    }
+
+    report->stratum = src->stratum;
+
+    switch (src->status) {
+      case SRC_FALSETICKER:
+        report->state = RPT_FALSETICKER;
+        break;
+      case SRC_JITTERY:
+        report->state = RPT_JITTERY;
+        break;
+      case SRC_WAITS_SOURCES:
+      case SRC_NONPREFERRED:
+      case SRC_WAITS_UPDATE:
+      case SRC_DISTANT:
+      case SRC_OUTLIER:
+        report->state = RPT_SELECTABLE;
+        break;
+      case SRC_UNSELECTED:
+        report->state = RPT_UNSELECTED;
+        break;
+      case SRC_SELECTED:
+        report->state = RPT_SELECTED;
+        break;
+      default:
+        report->state = RPT_NONSELECTABLE;
+        break;
+    }
+
+    report->reachability = src->reachability;
+
+    /* Call stats module to fill out estimates */
+    SST_DoSourceReport(src->stats, report, now);
+
+    return 1;
+  }
+
+}
+
+/* ================================================== */
+
+int
+SRC_ReportSourcestats(int index, RPT_SourcestatsReport *report, struct timespec *now)
+{ 
+  SRC_Instance src;
+
+  if ((index >= n_sources) || (index < 0)) {
+    return 0;
+  } else {
+    src = sources[index];
+    report->ref_id = src->ref_id;
+    if (src->ip_addr)
+      report->ip_addr = *src->ip_addr;
+    else
+      report->ip_addr.family = IPADDR_UNSPEC; 
+    SST_DoSourcestatsReport(src->stats, report, now);
+    return 1;
+  }
+}
+
+/* ================================================== */
+
+static char
+get_status_char(SRC_Status status)
+{
+  switch (status) {
+    case SRC_UNSELECTABLE:
+      return 'N';
+    case SRC_UNSYNCHRONISED:
+      return 's';
+    case SRC_BAD_STATS:
+      return 'M';
+    case SRC_BAD_DISTANCE:
+      return 'd';
+    case SRC_JITTERY:
+      return '~';
+    case SRC_WAITS_STATS:
+      return 'w';
+    case SRC_STALE:
+      return 'S';
+    case SRC_ORPHAN:
+      return 'O';
+    case SRC_UNTRUSTED:
+      return 'T';
+    case SRC_FALSETICKER:
+      return 'x';
+    case SRC_WAITS_SOURCES:
+      return 'W';
+    case SRC_NONPREFERRED:
+      return 'P';
+    case SRC_WAITS_UPDATE:
+      return 'U';
+    case SRC_DISTANT:
+      return 'D';
+    case SRC_OUTLIER:
+      return 'L';
+    case SRC_UNSELECTED:
+      return '+';
+    case SRC_SELECTED:
+      return '*';
+    default:
+      return '?';
+  }
+}
+
+/* ================================================== */
+
+int
+SRC_GetSelectReport(int index, RPT_SelectReport *report)
+{
+  SRC_Instance inst;
+
+  if (index >= n_sources || index < 0)
+    return 0;
+
+  inst = sources[index];
+
+  report->ref_id = inst->ref_id;
+  if (inst->ip_addr)
+    report->ip_addr = *inst->ip_addr;
+  else
+    report->ip_addr.family = IPADDR_UNSPEC;
+  report->state_char = get_status_char(inst->status);
+  report->authentication = inst->authenticated;
+  report->leap = inst->leap;
+  report->conf_options = inst->conf_sel_options;
+  report->eff_options = inst->sel_options;
+  report->last_sample_ago = inst->sel_info.last_sample_ago;
+  report->score = inst->sel_score;
+  report->lo_limit = inst->sel_info.lo_limit;
+  report->hi_limit = inst->sel_info.hi_limit;
+
+  return 1;
+}
+
+/* ================================================== */
+
+SRC_Type
+SRC_GetType(int index)
+{
+  if ((index >= n_sources) || (index < 0))
+    return -1;
+  return sources[index]->type;
+}
+
+/* ================================================== */