Hi, At the moment ntpd never goes into unsynced mode if network connectivity is lost. The code to do that is only triggered when a pakcet is received, which does not happen.
This diff fixes that by going into unsynced mode if no time data was processed for a while. An earlier version of this diff was tested by naddy@. Compared to that version, the needed period of inactivity is now three times as large and I set scale to 1, so recovery goes faster. Please test and review, -Otto Index: ntp.c =================================================================== RCS file: /cvs/src/usr.sbin/ntpd/ntp.c,v retrieving revision 1.165 diff -u -p -r1.165 ntp.c --- ntp.c 22 Jun 2020 06:11:34 -0000 1.165 +++ ntp.c 22 Aug 2020 13:48:34 -0000 @@ -89,6 +89,7 @@ ntp_main(struct ntpd_conf *nconf, struct struct stat stb; struct ctl_conn *cc; time_t nextaction, last_sensor_scan = 0, now; + time_t last_action = 0, interval; void *newp; if (socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, PF_UNSPEC, @@ -402,6 +403,7 @@ ntp_main(struct ntpd_conf *nconf, struct for (; nfds > 0 && j < idx_clients; j++) { if (pfd[j].revents & (POLLIN|POLLERR)) { nfds--; + last_action = now; if (client_dispatch(idx2peer[j - idx_peers], conf->settime, conf->automatic) == -1) { log_warn("pipe write error (settime)"); @@ -417,8 +419,24 @@ ntp_main(struct ntpd_conf *nconf, struct for (s = TAILQ_FIRST(&conf->ntp_sensors); s != NULL; s = next_s) { next_s = TAILQ_NEXT(s, entry); - if (s->next <= getmonotime()) + if (s->next <= now) { + last_action = now; sensor_query(s); + } + } + + /* + * Compute maximum of scale_interval(INTERVAL_QUERY_NORMAL), + * if we did not process a time message for three times that + * interval, stop advertising we're synced. + */ + interval = INTERVAL_QUERY_NORMAL * conf->scale; + interval += MAXIMUM(5, interval / 10) - 1; + if (conf->status.synced && last_action + 3 * interval < now) { + log_info("clock is now unsynced"); + conf->status.synced = 0; + conf->scale = 1; + priv_dns(IMSG_UNSYNCED, NULL, 0); } }