d99ef636f
Denys Vlasenko
2013-05-22
Subject
ntpd: drop delay outliers; run "unsync" handler if no replies for some time
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networking/ntpd.c+34 -8
| @@ -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"); | |