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ntpd: don't stay at short polling interval
To avoid polling servers frequently slowly increase the interval up to BIGPOLL when - no replies are received from a peer - no source can be selected - peer claims to be unsynchronized (e.g. we are polling it too frequently) When recv() returns with an error, drop code to try to continue on network errors: I'm not convinced those cases happen in real life. function old new delta recv_and_process_peer_pkt 919 838 -81 Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com> Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Miroslav Lichvar
Denys Vlasenko
parent
cf76b5ce12
commit
b434ce7069
@ -136,17 +136,17 @@
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#define BURSTPOLL 0 /* initial poll */
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#define MINPOLL 5 /* minimum poll interval. std ntpd uses 6 (6: 64 sec) */
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/*
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* If offset > discipline_jitter * POLLADJ_GATE, and poll interval is >= 2^BIGPOLL,
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* then it is decreased _at once_. (If < 2^BIGPOLL, it will be decreased _eventually_).
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* If offset > discipline_jitter * POLLADJ_GATE, and poll interval is > 2^BIGPOLL,
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* then it is decreased _at once_. (If <= 2^BIGPOLL, it will be decreased _eventually_).
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*/
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#define BIGPOLL 10 /* 2^10 sec ~= 17 min */
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#define BIGPOLL 9 /* 2^9 sec ~= 8.5 min */
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#define MAXPOLL 12 /* maximum poll interval (12: 1.1h, 17: 36.4h). std ntpd uses 17 */
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/*
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* Actively lower poll when we see such big offsets.
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* With STEP_THRESHOLD = 0.125, it means we try to sync more aggressively
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* if offset increases over ~0.04 sec
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*/
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#define POLLDOWN_OFFSET (STEP_THRESHOLD / 3)
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//#define POLLDOWN_OFFSET (STEP_THRESHOLD / 3)
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#define MINDISP 0.01 /* minimum dispersion (sec) */
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#define MAXDISP 16 /* maximum dispersion (sec) */
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#define MAXSTRAT 16 /* maximum stratum (infinity metric) */
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@ -984,8 +984,8 @@ static void clamp_pollexp_and_set_MAXSTRAT(void)
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{
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if (G.poll_exp < MINPOLL)
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G.poll_exp = MINPOLL;
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if (G.poll_exp >= BIGPOLL)
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G.poll_exp = BIGPOLL - 1;
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if (G.poll_exp > BIGPOLL)
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G.poll_exp = BIGPOLL;
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G.polladj_count = 0;
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G.stratum = MAXSTRAT;
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}
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@ -1682,7 +1682,7 @@ poll_interval(int upper_bound)
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VERB4 bb_error_msg("chose poll interval:%u (poll_exp:%d)", interval, G.poll_exp);
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return interval;
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}
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static NOINLINE void
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static void
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adjust_poll(int count)
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{
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G.polladj_count += count;
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@ -1693,7 +1693,7 @@ adjust_poll(int count)
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VERB4 bb_error_msg("polladj: discipline_jitter:%f ++poll_exp=%d",
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G.discipline_jitter, G.poll_exp);
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}
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} else if (G.polladj_count < -POLLADJ_LIMIT || (count < 0 && G.poll_exp >= BIGPOLL)) {
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} else if (G.polladj_count < -POLLADJ_LIMIT || (count < 0 && G.poll_exp > BIGPOLL)) {
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G.polladj_count = 0;
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if (G.poll_exp > MINPOLL) {
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llist_t *item;
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@ -1736,19 +1736,23 @@ recv_and_process_peer_pkt(peer_t *p)
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* ntp servers reply from their *other IP*.
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* TODO: maybe we should check at least what we can: from.port == 123?
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*/
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recv_again:
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size = recv(p->p_fd, &msg, sizeof(msg), MSG_DONTWAIT);
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if (size == -1) {
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bb_perror_msg("recv(%s) error", p->p_dotted);
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if (errno == EHOSTUNREACH || errno == EHOSTDOWN
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|| errno == ENETUNREACH || errno == ENETDOWN
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|| errno == ECONNREFUSED || errno == EADDRNOTAVAIL
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|| errno == EAGAIN
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) {
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//TODO: always do this?
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interval = poll_interval(RETRY_INTERVAL);
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goto set_next_and_ret;
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}
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xfunc_die();
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if (size < 0) {
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if (errno == EINTR)
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/* Signal caught */
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goto recv_again;
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if (errno == EAGAIN)
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/* There was no packet after all
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* (poll() returning POLLIN for a fd
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* is not a ironclad guarantee that data is there)
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*/
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return;
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/*
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* If you need a different handling for a specific
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* errno, always explain it in comment.
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*/
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bb_perror_msg_and_die("recv(%s) error", p->p_dotted);
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}
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if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE) {
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@ -1774,10 +1778,15 @@ recv_and_process_peer_pkt(peer_t *p)
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|| msg.m_stratum == 0
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|| msg.m_stratum > NTP_MAXSTRATUM
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) {
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// TODO: stratum 0 responses may have commands in 32-bit m_refid field:
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// "DENY", "RSTR" - peer does not like us at all
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// "RATE" - peer is overloaded, reduce polling freq
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bb_error_msg("reply from %s: peer is unsynced", p->p_dotted);
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/*
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* Stratum 0 responses may have commands in 32-bit m_refid field:
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* "DENY", "RSTR" - peer does not like us at all,
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* "RATE" - peer is overloaded, reduce polling freq.
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* If poll interval is small, increase it.
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*/
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if (G.poll_exp < BIGPOLL)
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goto increase_interval;
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goto pick_normal_interval;
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}
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@ -1866,11 +1875,19 @@ recv_and_process_peer_pkt(peer_t *p)
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/* Muck with statictics and update the clock */
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filter_datapoints(p);
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q = select_and_cluster();
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rc = -1;
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rc = 0;
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if (q) {
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rc = 0;
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if (!(option_mask32 & OPT_w)) {
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rc = update_local_clock(q);
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#if 0
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//Disabled this because there is a case where largish offsets
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//are unavoidable: if network round-trip delay is, say, ~0.6s,
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//error in offset estimation would be ~delay/2 ~= 0.3s.
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//Thus, offsets will be usually in -0.3...0.3s range.
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//In this case, this code would keep poll interval small,
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//but it won't be helping.
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//BIGOFF check below deals with a case of seeing multi-second offsets.
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/* If drift is dangerously large, immediately
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* drop poll interval one step down.
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*/
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@ -1879,9 +1896,15 @@ recv_and_process_peer_pkt(peer_t *p)
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adjust_poll(-POLLADJ_LIMIT * 3);
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rc = 0;
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}
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#endif
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}
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} else {
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/* No peer selected.
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* If poll interval is small, increase it.
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*/
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if (G.poll_exp < BIGPOLL)
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goto increase_interval;
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}
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/* else: no peer selected, rc = -1: we want to poll more often */
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if (rc != 0) {
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/* Adjust the poll interval by comparing the current offset
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@ -1893,6 +1916,7 @@ recv_and_process_peer_pkt(peer_t *p)
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if (rc > 0 && G.offset_to_jitter_ratio <= POLLADJ_GATE) {
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/* was += G.poll_exp but it is a bit
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* too optimistic for my taste at high poll_exp's */
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increase_interval:
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adjust_poll(MINPOLL);
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} else {
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adjust_poll(-G.poll_exp * 2);
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@ -1917,7 +1941,6 @@ recv_and_process_peer_pkt(peer_t *p)
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interval = BIGOFF_INTERVAL;
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}
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set_next_and_ret:
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set_next(p, interval);
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}
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@ -2252,6 +2275,9 @@ int ntpd_main(int argc UNUSED_PARAM, char **argv)
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/* Timed out waiting for reply */
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close(p->p_fd);
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p->p_fd = -1;
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/* If poll interval is small, increase it */
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if (G.poll_exp < BIGPOLL)
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adjust_poll(MINPOLL);
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timeout = poll_interval(NOREPLY_INTERVAL);
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bb_error_msg("timed out waiting for %s, reach 0x%02x, next query in %us",
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p->p_dotted, p->reachable_bits, timeout);
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