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ntpd: drop delay outliers; run "unsync" handler if no replies for some time

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function                                             old     new   delta
ntpd_main                                            960    1029     +69
recv_and_process_peer_pkt                            834     892     +58
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(add/remove: 0/0 grow/shrink: 2/0 up/down: 127/0)             Total: 127 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2013-05-22 17:48:19 +02:00
parent b6dc13c2d3
commit d99ef636f6
1 changed files with 34 additions and 8 deletions
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42
networking/ntpd.c
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@ -95,6 +95,7 @@
#define RETRY_INTERVAL 5 /* on error, retry in N secs */
#define RESPONSE_INTERVAL 15 /* wait for reply up to N secs */
#define INITIAL_SAMPLES 4 /* how many samples do we want for init */
#define BAD_DELAY_GROWTH 4 /* drop packet if its delay grew by more than this */
/* Clock discipline parameters and constants */
@ -1616,6 +1617,7 @@ recv_and_process_peer_pkt(peer_t *p)
ssize_t size;
msg_t msg;
double T1, T2, T3, T4;
double dv;
unsigned interval;
datapoint_t *datapoint;
peer_t *q;
@ -1665,9 +1667,8 @@ recv_and_process_peer_pkt(peer_t *p)
// TODO: stratum 0 responses may have commands in 32-bit m_refid field:
// "DENY", "RSTR" - peer does not like us at all
// "RATE" - peer is overloaded, reduce polling freq
interval = poll_interval(0);
bb_error_msg("reply from %s: peer is unsynced, next query in %us", p->p_dotted, interval);
goto set_next_and_ret;
bb_error_msg("reply from %s: peer is unsynced", p->p_dotted);
goto pick_normal_interval;
}
// /* Verify valid root distance */
@ -1700,21 +1701,31 @@ recv_and_process_peer_pkt(peer_t *p)
T4 = G.cur_time;
p->lastpkt_recv_time = T4;
VERB5 bb_error_msg("%s->lastpkt_recv_time=%f", p->p_dotted, p->lastpkt_recv_time);
p->datapoint_idx = p->reachable_bits ? (p->datapoint_idx + 1) % NUM_DATAPOINTS : 0;
datapoint = &p->filter_datapoint[p->datapoint_idx];
datapoint->d_recv_time = T4;
datapoint->d_offset = ((T2 - T1) + (T3 - T4)) / 2;
/* The delay calculation is a special case. In cases where the
* server and client clocks are running at different rates and
* with very fast networks, the delay can appear negative. In
* order to avoid violating the Principle of Least Astonishment,
* the delay is clamped not less than the system precision.
*/
dv = p->lastpkt_delay;
p->lastpkt_delay = (T4 - T1) - (T3 - T2);
if (p->lastpkt_delay < G_precision_sec)
p->lastpkt_delay = G_precision_sec;
/*
* If this packet's delay is much bigger than the last one,
* it's better to just ignore it than use its much less precise value.
*/
if (p->reachable_bits && p->lastpkt_delay > dv * BAD_DELAY_GROWTH) {
bb_error_msg("reply from %s: delay %f is too high, ignoring", p->p_dotted, p->lastpkt_delay);
goto pick_normal_interval;
}
p->datapoint_idx = p->reachable_bits ? (p->datapoint_idx + 1) % NUM_DATAPOINTS : 0;
datapoint = &p->filter_datapoint[p->datapoint_idx];
datapoint->d_recv_time = T4;
datapoint->d_offset = ((T2 - T1) + (T3 - T4)) / 2;
datapoint->d_dispersion = LOG2D(msg.m_precision_exp) + G_precision_sec;
if (!p->reachable_bits) {
/* 1st datapoint ever - replicate offset in every element */
@ -1811,6 +1822,7 @@ recv_and_process_peer_pkt(peer_t *p)
}
/* Decide when to send new query for this peer */
pick_normal_interval:
interval = poll_interval(0);
set_next_and_ret:
@ -2195,6 +2207,20 @@ int ntpd_main(int argc UNUSED_PARAM, char **argv)
gettime1900d(); /* sets G.cur_time */
}
}
if (G.ntp_peers && G.stratum != MAXSTRAT) {
for (item = G.ntp_peers; item != NULL; item = item->link) {
peer_t *p = (peer_t *) item->data;
if (p->reachable_bits)
goto have_reachable_peer;
}
/* No peer responded for last 8 packets, panic */
G.polladj_count = 0;
G.poll_exp = MINPOLL;
G.stratum = MAXSTRAT;
run_script("unsync", G.last_update_offset);
have_reachable_peer: ;
}
} /* while (!bb_got_signal) */
remove_pidfile(CONFIG_PID_FILE_PATH "/ntpd.pid");