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sources.c
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sources.c
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/*
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_BAD_STATS, /* Doesn't have valid stats data */
SRC_UNSYNCHRONISED, /* Provides samples, but not synchronised */
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) */
static int forced_first_report; /* Flag to allow one failed selection to be
logged before a successful selection */
/* 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++;
/* Source selection can change with unreachable sources */
if (inst->reachability == 0) {
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 max_badstat_reach, max_badstat_reach_size, n_badstats_sources;
int max_sel_reach, max_sel_reach_size;
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 = max_badstat_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;
}
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;
if (max_badstat_reach_size < sources[i]->reachability_size)
max_badstat_reach_size = sources[i]->reachability_size;
continue;
}
/* Ignore sources which are not synchronised */
if (sources[i]->leap == LEAP_Unsynchronised) {
mark_source(sources[i], SRC_UNSYNCHRONISED);
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.