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smooth: add option to smooth out only leap seconds

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The leaponly option can be used to enable a mode where only leap seconds
are smoothed out and normal offset/frequency changes are ignored. This
is useful to make the interval in which a leap second is smoothed out
constant and allow an NTP client to use multiple leap smearing servers
safely.
This commit is contained in:
Miroslav Lichvar
2015-06-02 13:24:04 +02:00
parent 31669f343a
commit 0abdc2a350
6 changed files with 61 additions and 20 deletions
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30
smooth.c
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@@ -77,6 +77,10 @@ static struct stage stages[NUM_STAGES];
/* Enabled/disabled smoothing */
static int enabled;
/* Enabled/disabled mode where only leap seconds are smoothed out and normal
offset/frequency changes are ignored */
static int leap_only_mode;
/* Maximum skew/max_wander ratio to start updating offset and frequency */
#define UNLOCK_SKEW_WANDER_RATIO 10000
@@ -185,8 +189,9 @@ update_smoothing(struct timeval *now, double offset, double freq)
{
/* Don't accept offset/frequency until the clock has stabilized */
if (locked) {
if (REF_GetSkew() / max_wander < UNLOCK_SKEW_WANDER_RATIO) {
LOG(LOGS_INFO, LOGF_Smooth, "Time smoothing activated");
if (REF_GetSkew() / max_wander < UNLOCK_SKEW_WANDER_RATIO || leap_only_mode) {
LOG(LOGS_INFO, LOGF_Smooth, "Time smoothing activated%s", leap_only_mode ?
" (leap seconds only)" : "");
locked = 0;
}
return;
@@ -208,15 +213,19 @@ handle_slew(struct timeval *raw, struct timeval *cooked, double dfreq,
{
double delta;
if (change_type == LCL_ChangeAdjust)
update_smoothing(cooked, doffset, dfreq);
if (change_type == LCL_ChangeAdjust) {
if (leap_only_mode)
update_smoothing(cooked, 0.0, 0.0);
else
update_smoothing(cooked, doffset, dfreq);
}
UTI_AdjustTimeval(&last_update, cooked, &last_update, &delta, dfreq, doffset);
}
void SMT_Initialise(void)
{
CNF_GetSmooth(&max_freq, &max_wander);
CNF_GetSmooth(&max_freq, &max_wander, &leap_only_mode);
if (max_freq <= 0.0 || max_wander <= 0.0) {
enabled = 0;
return;
@@ -265,3 +274,14 @@ SMT_Reset(struct timeval *now)
smooth_freq = 0.0;
last_update = *now;
}
void
SMT_Leap(struct timeval *now, int leap)
{
/* When the leap-only mode is disabled, the leap second will be accumulated
in handle_slew() as a normal offset */
if (!enabled || !leap_only_mode)
return;
update_smoothing(now, leap, 0.0);
}