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ntp: adapt sampling separation for short polling intervals

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This commit is contained in:
Miroslav Lichvar 2017-01-19 11:14:07 +01:00
parent beaaaad162
commit 97d4203354
1 changed files with 25 additions and 7 deletions
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32
ntp_core.c
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@ -205,7 +205,8 @@ static ARR_Instance broadcasts;
/* Spacing required between samples for any two servers/peers (to
minimise risk of network collisions) (in seconds) */
#define SAMPLING_SEPARATION 0.2
#define MIN_SAMPLING_SEPARATION 0.02
#define MAX_SAMPLING_SEPARATION 0.2
/* Randomness added to spacing between samples for one server/peer */
#define SAMPLING_RANDOMNESS 0.02
@ -279,6 +280,7 @@ static const char tss_chars[3] = {'D', 'K', 'H'};
static void transmit_timeout(void *arg);
static double get_transmit_delay(NCR_Instance inst, int on_tx, double last_tx);
static double get_separation(int poll);
/* ================================================== */
@ -399,7 +401,7 @@ restart_timeout(NCR_Instance inst, double delay)
SCH_RemoveTimeout(inst->tx_timeout_id);
/* Start new timer for transmission */
inst->tx_timeout_id = SCH_AddTimeoutInClass(delay, SAMPLING_SEPARATION,
inst->tx_timeout_id = SCH_AddTimeoutInClass(delay, get_separation(inst->local_poll),
SAMPLING_RANDOMNESS,
SCH_NtpSamplingClass,
transmit_timeout, (void *)inst);
@ -823,6 +825,21 @@ get_transmit_delay(NCR_Instance inst, int on_tx, double last_tx)
return delay_time;
}
/* ================================================== */
/* Calculate sampling separation for given polling interval */
static double
get_separation(int poll)
{
double separation;
/* Allow up to 8 sources using the same short interval to not be limited
by the separation */
separation = UTI_Log2ToDouble(poll - 3);
return CLAMP(MIN_SAMPLING_SEPARATION, separation, MAX_SAMPLING_SEPARATION);
}
/* ================================================== */
/* Timeout handler for closing the client socket when no acceptable
reply can be received from the server */
@ -2345,20 +2362,21 @@ broadcast_timeout(void *arg)
BroadcastDestination *destination;
NTP_int64 orig_ts;
NTP_Local_Timestamp recv_ts;
int poll;
destination = ARR_GetElement(broadcasts, (long)arg);
poll = log(destination->interval) / log(2.0) + 0.5;
UTI_ZeroNtp64(&orig_ts);
UTI_ZeroTimespec(&recv_ts.ts);
recv_ts.source = NTP_TS_DAEMON;
recv_ts.err = 0.0;
transmit_packet(MODE_BROADCAST, 0, log(destination->interval) / log(2.0) + 0.5,
NTP_VERSION, 0, 0, &orig_ts, &orig_ts, &recv_ts, NULL, NULL, NULL,
&destination->addr, &destination->local_addr);
transmit_packet(MODE_BROADCAST, 0, poll, NTP_VERSION, 0, 0, &orig_ts, &orig_ts, &recv_ts,
NULL, NULL, NULL, &destination->addr, &destination->local_addr);
/* Requeue timeout. We don't care if interval drifts gradually. */
SCH_AddTimeoutInClass(destination->interval, SAMPLING_SEPARATION, SAMPLING_RANDOMNESS,
SCH_AddTimeoutInClass(destination->interval, get_separation(poll), SAMPLING_RANDOMNESS,
SCH_NtpBroadcastClass, broadcast_timeout, arg);
}
@ -2377,7 +2395,7 @@ NCR_AddBroadcastDestination(IPAddr *addr, unsigned short port, int interval)
destination->local_addr.sock_fd = NIO_OpenServerSocket(&destination->addr);
destination->interval = CLAMP(1, interval, 1 << MAX_POLL);
SCH_AddTimeoutInClass(destination->interval, SAMPLING_SEPARATION, SAMPLING_RANDOMNESS,
SCH_AddTimeoutInClass(destination->interval, MAX_SAMPLING_SEPARATION, SAMPLING_RANDOMNESS,
SCH_NtpBroadcastClass, broadcast_timeout,
(void *)(long)(ARR_GetSize(broadcasts) - 1));
}