From 1ee5afdce28d5a11987071f710c1d2fd493618cc Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Sat, 2 Jan 2010 15:57:07 +0100 Subject: ntpd: fix jitter calculations and status propagation Signed-off-by: Denys Vlasenko --- networking/ntpd.c | 119 ++++++++++++++++++++++++++---------------------------- 1 file changed, 58 insertions(+), 61 deletions(-) (limited to 'networking') diff --git a/networking/ntpd.c b/networking/ntpd.c index cabfb79..92e2723 100644 --- a/networking/ntpd.c +++ b/networking/ntpd.c @@ -166,7 +166,7 @@ typedef struct { int p_fd; int datapoint_idx; uint32_t lastpkt_refid; - uint8_t lastpkt_leap; + uint8_t lastpkt_status; uint8_t lastpkt_stratum; uint8_t p_reachable_bits; double p_xmttime; @@ -216,7 +216,7 @@ struct globals { * in stratum 2+ packets, it's IPv4 address or 4 first bytes of MD5 hash of IPv6 */ uint32_t refid; - uint8_t leap; + uint8_t ntp_status; /* precision is defined as the larger of the resolution and time to * read the clock, in log2 units. For instance, the precision of a * mains-frequency clock incrementing at 60 Hz is 16 ms, even when the @@ -245,8 +245,6 @@ struct globals { #define G_precision_sec (1.0 / (1 << (- G_precision_exp))) uint8_t stratum; /* Bool. After set to 1, never goes back to 0: */ -//TODO: fix logic: -// uint8_t time_was_stepped; uint8_t adjtimex_was_done; uint8_t discipline_state; // doc calls it c.state @@ -415,12 +413,13 @@ filter_datapoints(peer_t *p, double t) */ wavg = 0; w = 0.5; - // n-1 - // --- dispersion(i) - // filter_dispersion = \ ------------- - // / (i+1) - // --- 2 - // i=0 + /* n-1 + * --- dispersion(i) + * filter_dispersion = \ ------------- + * / (i+1) + * --- 2 + * i=0 + */ got_newest = 0; sum = 0; for (i = 0; i < NUM_DATAPOINTS; i++) { @@ -474,21 +473,22 @@ filter_datapoints(peer_t *p, double t) } p->filter_offset = wavg; - // +----- -----+ ^ 1/2 - // | n-1 | - // | --- | - // 1 | \ 2 | - // filter_jitter = --- * | / (avg-offset_j) | - // n | --- | - // | j=0 | - // +----- -----+ - // where n is the number of valid datapoints in the filter (n > 1); - // if filter_jitter < precision then filter_jitter = precision + /* +----- -----+ ^ 1/2 + * | n-1 | + * | --- | + * | 1 \ 2 | + * filter_jitter = | --- * / (avg-offset_j) | + * | n --- | + * | j=0 | + * +----- -----+ + * where n is the number of valid datapoints in the filter (n > 1); + * if filter_jitter < precision then filter_jitter = precision + */ sum = 0; for (i = 0; i < NUM_DATAPOINTS; i++) { sum += SQUARE(wavg - p->filter_datapoint[i].d_offset); } - sum = SQRT(sum) / NUM_DATAPOINTS; + sum = SQRT(sum / NUM_DATAPOINTS); p->filter_jitter = sum > G_precision_sec ? sum : G_precision_sec; VERB3 bb_error_msg("filter offset:%f(corr:%e) disp:%f jitter:%f", @@ -570,22 +570,23 @@ do_sendto(int fd, static int send_query_to_peer(peer_t *p) { - // Why do we need to bind()? - // See what happens when we don't bind: - // - // socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 3 - // setsockopt(3, SOL_IP, IP_TOS, [16], 4) = 0 - // gettimeofday({1259071266, 327885}, NULL) = 0 - // sendto(3, "xxx", 48, MSG_DONTWAIT, {sa_family=AF_INET, sin_port=htons(123), sin_addr=inet_addr("10.34.32.125")}, 16) = 48 - // ^^^ we sent it from some source port picked by kernel. - // time(NULL) = 1259071266 - // write(2, "ntpd: entering poll 15 secs\n", 28) = 28 - // poll([{fd=3, events=POLLIN}], 1, 15000) = 1 ([{fd=3, revents=POLLIN}]) - // recv(3, "yyy", 68, MSG_DONTWAIT) = 48 - // ^^^ this recv will receive packets to any local port! - // - // Uncomment this and use strace to see it in action: -#define PROBE_LOCAL_ADDR // { len_and_sockaddr lsa; lsa.len = LSA_SIZEOF_SA; getsockname(p->query.fd, &lsa.u.sa, &lsa.len); } + /* Why do we need to bind()? + * See what happens when we don't bind: + * + * socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 3 + * setsockopt(3, SOL_IP, IP_TOS, [16], 4) = 0 + * gettimeofday({1259071266, 327885}, NULL) = 0 + * sendto(3, "xxx", 48, MSG_DONTWAIT, {sa_family=AF_INET, sin_port=htons(123), sin_addr=inet_addr("10.34.32.125")}, 16) = 48 + * ^^^ we sent it from some source port picked by kernel. + * time(NULL) = 1259071266 + * write(2, "ntpd: entering poll 15 secs\n", 28) = 28 + * poll([{fd=3, events=POLLIN}], 1, 15000) = 1 ([{fd=3, revents=POLLIN}]) + * recv(3, "yyy", 68, MSG_DONTWAIT) = 48 + * ^^^ this recv will receive packets to any local port! + * + * Uncomment this and use strace to see it in action: + */ +#define PROBE_LOCAL_ADDR /* { len_and_sockaddr lsa; lsa.len = LSA_SIZEOF_SA; getsockname(p->query.fd, &lsa.u.sa, &lsa.len); } */ if (p->p_fd == -1) { int fd, family; @@ -662,8 +663,6 @@ step_time(double offset) strftime(buf, sizeof(buf), "%a %b %e %H:%M:%S %Z %Y", localtime(&tval)); bb_error_msg("setting clock to %s (offset %fs)", buf, offset); - -// G.time_was_stepped = 1; } @@ -705,13 +704,14 @@ fit(peer_t *p, double rd) VERB3 bb_error_msg("peer %s unfit for selection: unreachable", p->p_dotted); return 0; } -//TODO: we never accept such packets anyway, right? - if ((p->lastpkt_leap & LI_ALARM) == LI_ALARM +#if 0 /* we filter out such packets earlier */ + if ((p->lastpkt_status & LI_ALARM) == LI_ALARM || p->lastpkt_stratum >= MAXSTRAT ) { VERB3 bb_error_msg("peer %s unfit for selection: bad status/stratum", p->p_dotted); return 0; } +#endif /* rd is root_distance(p, t) */ if (rd > MAXDIST + FREQ_TOLERANCE * (1 << G.poll_exp)) { VERB3 bb_error_msg("peer %s unfit for selection: root distance too high", p->p_dotted); @@ -908,7 +908,6 @@ select_and_cluster(double t) selection_jitter_sq = 0; for (j = 0; j < num_survivors; j++) { peer_t *q = survivor[j].p; -//TODO: where is 1/(n-1) * ... multiplier? selection_jitter_sq += SQUARE(p->filter_offset - q->filter_offset); } if (i == 0 || selection_jitter_sq > max_selection_jitter) { @@ -918,7 +917,7 @@ select_and_cluster(double t) VERB5 bb_error_msg("survivor %d selection_jitter^2:%f", i, selection_jitter_sq); } - max_selection_jitter = SQRT(max_selection_jitter); + max_selection_jitter = SQRT(max_selection_jitter / num_survivors); VERB4 bb_error_msg("max_selection_jitter (at %d):%f min_jitter:%f", max_idx, max_selection_jitter, min_jitter); @@ -991,7 +990,9 @@ update_local_clock(peer_t *p, double t) double offset = p->filter_offset; double recv_time = p->lastpkt_recv_time; double abs_offset; +#if !USING_KERNEL_PLL_LOOP double freq_drift; +#endif double since_last_update; double etemp, dtemp; @@ -1017,7 +1018,9 @@ update_local_clock(peer_t *p, double t) * and frequency errors. */ since_last_update = recv_time - G.reftime; +#if !USING_KERNEL_PLL_LOOP freq_drift = 0; +#endif if (G.discipline_state == STATE_FREQ) { /* Ignore updates until the stepout threshold */ if (since_last_update < WATCH_THRESHOLD) { @@ -1025,7 +1028,9 @@ update_local_clock(peer_t *p, double t) WATCH_THRESHOLD - since_last_update); return 0; /* "leave poll interval as is" */ } +#if !USING_KERNEL_PLL_LOOP freq_drift = (offset - G.last_update_offset) / since_last_update; +#endif } /* There are two main regimes: when the @@ -1145,6 +1150,7 @@ update_local_clock(peer_t *p, double t) break; default: +#if !USING_KERNEL_PLL_LOOP /* Compute freq_drift due to PLL and FLL contributions. * * The FLL and PLL frequency gain constants @@ -1167,6 +1173,7 @@ update_local_clock(peer_t *p, double t) etemp = MIND(since_last_update, (1 << G.poll_exp)); dtemp = (4 * PLL) << G.poll_exp; freq_drift += offset * etemp / SQUARE(dtemp); +#endif set_new_values(STATE_SYNC, offset, recv_time); break; } @@ -1174,7 +1181,7 @@ update_local_clock(peer_t *p, double t) } G.reftime = t; - G.leap = p->lastpkt_leap; + G.ntp_status = p->lastpkt_status; G.refid = p->lastpkt_refid; G.rootdelay = p->lastpkt_rootdelay + p->lastpkt_delay; dtemp = p->filter_jitter; // SQRT(SQUARE(p->filter_jitter) + SQUARE(s.jitter)); @@ -1241,10 +1248,10 @@ update_local_clock(peer_t *p, double t) /* + (G.last_update_offset < 0 ? -0.5 : 0.5) - too small to bother */ + old_tmx_offset; /* almost always 0 */ tmx.status = STA_PLL; - //if (sys_leap == LEAP_ADDSECOND) - // tmx.status |= STA_INS; - //else if (sys_leap == LEAP_DELSECOND) - // tmx.status |= STA_DEL; + if (G.ntp_status & LI_PLUSSEC) + tmx.status |= STA_INS; + if (G.ntp_status & LI_MINUSSEC) + tmx.status |= STA_DEL; tmx.constant = G.poll_exp - 4; //tmx.esterror = (u_int32)(clock_jitter * 1e6); //tmx.maxerror = (u_int32)((sys_rootdelay / 2 + sys_rootdisp) * 1e6); @@ -1376,18 +1383,12 @@ recv_and_process_peer_pkt(peer_t *p) goto close_sock; } -// /* -// * Verify the server is synchronized with valid stratum and -// * reference time not later than the transmit time. -// */ -// if (p->lastpkt_leap == NOSYNC || p->lastpkt_stratum >= MAXSTRAT) -// return; /* unsynchronized */ -// // /* Verify valid root distance */ // if (msg.m_rootdelay / 2 + msg.m_rootdisp >= MAXDISP || p->lastpkt_reftime > msg.m_xmt) // return; /* invalid header values */ - p->lastpkt_leap = msg.m_status; + p->lastpkt_status = msg.m_status; + p->lastpkt_stratum = msg.m_stratum; p->lastpkt_rootdelay = sfp_to_d(msg.m_rootdelay); p->lastpkt_rootdisp = sfp_to_d(msg.m_rootdisp); p->lastpkt_refid = msg.m_refid; @@ -1557,7 +1558,7 @@ recv_and_process_client_pkt(void /*int fd*/) /* Build a reply packet */ memset(&msg, 0, sizeof(msg)); - msg.m_status = G.stratum < MAXSTRAT ? G.leap : LI_ALARM; + msg.m_status = G.stratum < MAXSTRAT ? G.ntp_status : LI_ALARM; msg.m_status |= (query_status & VERSION_MASK); msg.m_status |= ((query_status & MODE_MASK) == MODE_CLIENT) ? MODE_SERVER : MODE_SYM_PAS; @@ -1822,10 +1823,6 @@ int ntpd_main(int argc UNUSED_PARAM, char **argv) } } -// if ((trial_cnt > 0 && sent_cnt == 0) || g.peer_cnt == 0) { -// G.time_was_stepped = 1; -// } - timeout = nextaction - cur_time; if (timeout < 1) timeout = 1; -- cgit v1.1