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ntp: refresh IP addresses periodically

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Refresh NTP sources specified by hostname periodically (every 2 weeks
by default) to avoid long-running instances using a server which is no
longer intended for service, even if it is still responding correctly
and would not be replaced as unreachable, and help redistributing load
in large pools like pool.ntp.org. Only one source is refreshed at a time
to not interrupt clock updates if there are multiple selectable servers.

The refresh directive configures the interval. A value of 0 disables
the periodic refreshment.

Suggested-by: Ask Bjørn Hansen <ask@develooper.com>
This commit is contained in:
Miroslav Lichvar
2023-06-20 16:23:34 +02:00
parent 36f9b24dfe
commit b86c50bb9f
5 changed files with 103 additions and 1 deletions
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48
ntp_sources.c
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@@ -32,6 +32,7 @@
#include "sysincl.h"
#include "array.h"
#include "conf.h"
#include "ntp_sources.h"
#include "ntp_core.h"
#include "ntp_io.h"
@@ -64,6 +65,7 @@ typedef struct {
received from the source yet */
uint32_t conf_id; /* Configuration ID, which can be shared with
different sources in case of a pool */
double last_resolving; /* Time of last name resolving (monotonic) */
} SourceRecord;
/* Hash table of SourceRecord, its size is a power of two and it's never
@@ -389,6 +391,7 @@ add_source(NTP_Remote_Address *remote_addr, char *name, NTP_Source_Type type,
record->pool_id = pool_id;
record->tentative = 1;
record->conf_id = conf_id;
record->last_resolving = SCH_GetLastEventMonoTime();
record_lock = 0;
@@ -985,9 +988,11 @@ resolve_source_replacement(SourceRecord *record, int refreshment)
{
struct UnresolvedSource *us;
DEBUG_LOG("trying to replace %s (%s)",
DEBUG_LOG("%s %s (%s)", refreshment ? "refreshing" : "trying to replace",
UTI_IPToString(&record->remote_addr->ip_addr), record->name);
record->last_resolving = SCH_GetLastEventMonoTime();
us = MallocNew(struct UnresolvedSource);
us->name = Strdup(record->name);
/* Ignore the order of addresses from the resolver to not get
@@ -1042,6 +1047,45 @@ NSR_HandleBadSource(IPAddr *address)
/* ================================================== */
static void
maybe_refresh_source(void)
{
static double last_refreshment = 0.0;
SourceRecord *record, *oldest_record;
int i, min_interval;
double now;
min_interval = CNF_GetRefresh();
now = SCH_GetLastEventMonoTime();
if (min_interval <= 0 || now < last_refreshment + min_interval)
return;
last_refreshment = now;
for (i = 0, oldest_record = NULL; i < ARR_GetSize(records); i++) {
record = get_record(i);
if (!record->remote_addr || UTI_IsStringIP(record->name))
continue;
if (!oldest_record || oldest_record->last_resolving > record->last_resolving)
oldest_record = record;
}
if (!oldest_record)
return;
/* Check if the name wasn't already resolved in the last interval */
if (now < oldest_record->last_resolving + min_interval) {
last_refreshment = oldest_record->last_resolving;
return;
}
resolve_source_replacement(oldest_record, 1);
}
/* ================================================== */
void
NSR_RefreshAddresses(void)
{
@@ -1179,6 +1223,8 @@ NSR_ProcessRx(NTP_Remote_Address *remote_addr, NTP_Local_Address *local_addr,
remove_pool_sources(record->pool_id, 1, 0);
}
}
maybe_refresh_source();
} else {
NCR_ProcessRxUnknown(remote_addr, local_addr, rx_ts, message, length);
}