/* * NTP client/server, based on OpenNTPD 3.9p1 * * Author: Adam Tkac * * Licensed under GPLv2, see file LICENSE in this source tree. * * Parts of OpenNTPD clock syncronization code is replaced by * code which is based on ntp-4.2.6, whuch carries the following * copyright notice: * *********************************************************************** * * * Copyright (c) University of Delaware 1992-2009 * * * * Permission to use, copy, modify, and distribute this software and * * its documentation for any purpose with or without fee is hereby * * granted, provided that the above copyright notice appears in all * * copies and that both the copyright notice and this permission * * notice appear in supporting documentation, and that the name * * University of Delaware not be used in advertising or publicity * * pertaining to distribution of the software without specific, * * written prior permission. The University of Delaware makes no * * representations about the suitability this software for any * * purpose. It is provided "as is" without express or implied * * warranty. * * * *********************************************************************** */ //usage:#define ntpd_trivial_usage //usage: "[-dnqNw"IF_FEATURE_NTPD_SERVER("l -I IFACE")"] [-S PROG] [-p PEER]..." //usage:#define ntpd_full_usage "\n\n" //usage: "NTP client/server\n" //usage: "\n -d Verbose" //usage: "\n -n Do not daemonize" //usage: "\n -q Quit after clock is set" //usage: "\n -N Run at high priority" //usage: "\n -w Do not set time (only query peers), implies -n" //usage: IF_FEATURE_NTPD_SERVER( //usage: "\n -l Run as server on port 123" //usage: "\n -I IFACE Bind server to IFACE, implies -l" //usage: ) //usage: "\n -S PROG Run PROG after stepping time, stratum change, and every 11 mins" //usage: "\n -p PEER Obtain time from PEER (may be repeated)" //usage: IF_FEATURE_NTPD_CONF( //usage: "\n If -p is not given, read /etc/ntp.conf" //usage: ) // -l and -p options are not compatible with "standard" ntpd: // it has them as "-l logfile" and "-p pidfile". // -S and -w are not compat either, "standard" ntpd has no such opts. #include "libbb.h" #include #include /* For IPTOS_LOWDELAY definition */ #include /* setpriority */ #include #ifndef IPTOS_LOWDELAY # define IPTOS_LOWDELAY 0x10 #endif /* Verbosity control (max level of -dddd options accepted). * max 6 is very talkative (and bloated). 3 is non-bloated, * production level setting. */ #define MAX_VERBOSE 3 /* High-level description of the algorithm: * * We start running with very small poll_exp, BURSTPOLL, * in order to quickly accumulate INITIAL_SAMPLES datapoints * for each peer. Then, time is stepped if the offset is larger * than STEP_THRESHOLD, otherwise it isn't; anyway, we enlarge * poll_exp to MINPOLL and enter frequency measurement step: * we collect new datapoints but ignore them for WATCH_THRESHOLD * seconds. After WATCH_THRESHOLD seconds we look at accumulated * offset and estimate frequency drift. * * (frequency measurement step seems to not be strictly needed, * it is conditionally disabled with USING_INITIAL_FREQ_ESTIMATION * define set to 0) * * After this, we enter "steady state": we collect a datapoint, * we select the best peer, if this datapoint is not a new one * (IOW: if this datapoint isn't for selected peer), sleep * and collect another one; otherwise, use its offset to update * frequency drift, if offset is somewhat large, reduce poll_exp, * otherwise increase poll_exp. * * If offset is larger than STEP_THRESHOLD, which shouldn't normally * happen, we assume that something "bad" happened (computer * was hibernated, someone set totally wrong date, etc), * then the time is stepped, all datapoints are discarded, * and we go back to steady state. * * Made some changes to speed up re-syncing after our clock goes bad * (tested with suspending my laptop): * - if largish offset (>= STEP_THRESHOLD * 8 == 1 sec) is seen * from a peer, schedule next query for this peer soon * without drastically lowering poll interval for everybody. * This makes us collect enough data for step much faster: * e.g. at poll = 10 (1024 secs), step was done within 5 minutes * after first reply which indicated that our clock is 14 seconds off. * - on step, do not discard d_dispersion data of the existing datapoints, * do not clear reachable_bits. This prevents discarding first ~8 * datapoints after the step. */ #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 */ #define RETRY_INTERVAL 32 /* on send/recv error, retry in N secs (need to be power of 2) */ #define NOREPLY_INTERVAL 512 /* sent, but got no reply: cap next query by this many seconds */ #define RESPONSE_INTERVAL 16 /* wait for reply up to N secs */ /* Step threshold (sec). std ntpd uses 0.128. * Using exact power of 2 (1/8) results in smaller code */ #define STEP_THRESHOLD 0.125 /* Stepout threshold (sec). std ntpd uses 900 (11 mins (!)) */ #define WATCH_THRESHOLD 128 /* NB: set WATCH_THRESHOLD to ~60 when debugging to save time) */ //UNUSED: #define PANIC_THRESHOLD 1000 /* panic threshold (sec) */ /* * If we got |offset| > BIGOFF from a peer, cap next query interval * for this peer by this many seconds: */ #define BIGOFF (STEP_THRESHOLD * 8) #define BIGOFF_INTERVAL (1 << 7) /* 128 s */ #define FREQ_TOLERANCE 0.000015 /* frequency tolerance (15 PPM) */ #define BURSTPOLL 0 /* initial poll */ #define MINPOLL 5 /* minimum poll interval. std ntpd uses 6 (6: 64 sec) */ /* * If offset > discipline_jitter * POLLADJ_GATE, and poll interval is > 2^BIGPOLL, * then it is decreased _at once_. (If <= 2^BIGPOLL, it will be decreased _eventually_). */ #define BIGPOLL 9 /* 2^9 sec ~= 8.5 min */ #define MAXPOLL 12 /* maximum poll interval (12: 1.1h, 17: 36.4h). std ntpd uses 17 */ /* * Actively lower poll when we see such big offsets. * With STEP_THRESHOLD = 0.125, it means we try to sync more aggressively * if offset increases over ~0.04 sec */ //#define POLLDOWN_OFFSET (STEP_THRESHOLD / 3) #define MINDISP 0.01 /* minimum dispersion (sec) */ #define MAXDISP 16 /* maximum dispersion (sec) */ #define MAXSTRAT 16 /* maximum stratum (infinity metric) */ #define MAXDIST 1 /* distance threshold (sec) */ #define MIN_SELECTED 1 /* minimum intersection survivors */ #define MIN_CLUSTERED 3 /* minimum cluster survivors */ #define MAXDRIFT 0.000500 /* frequency drift we can correct (500 PPM) */ /* Poll-adjust threshold. * When we see that offset is small enough compared to discipline jitter, * we grow a counter: += MINPOLL. When counter goes over POLLADJ_LIMIT, * we poll_exp++. If offset isn't small, counter -= poll_exp*2, * and when it goes below -POLLADJ_LIMIT, we poll_exp--. * (Bumped from 30 to 40 since otherwise I often see poll_exp going *2* steps down) */ #define POLLADJ_LIMIT 40 /* If offset < discipline_jitter * POLLADJ_GATE, then we decide to increase * poll interval (we think we can't improve timekeeping * by staying at smaller poll). */ #define POLLADJ_GATE 4 #define TIMECONST_HACK_GATE 2 /* Compromise Allan intercept (sec). doc uses 1500, std ntpd uses 512 */ #define ALLAN 512 /* PLL loop gain */ #define PLL 65536 /* FLL loop gain [why it depends on MAXPOLL??] */ #define FLL (MAXPOLL + 1) /* Parameter averaging constant */ #define AVG 4 enum { NTP_VERSION = 4, NTP_MAXSTRATUM = 15, NTP_DIGESTSIZE = 16, NTP_MSGSIZE_NOAUTH = 48, NTP_MSGSIZE = (NTP_MSGSIZE_NOAUTH + 4 + NTP_DIGESTSIZE), /* Status Masks */ MODE_MASK = (7 << 0), VERSION_MASK = (7 << 3), VERSION_SHIFT = 3, LI_MASK = (3 << 6), /* Leap Second Codes (high order two bits of m_status) */ LI_NOWARNING = (0 << 6), /* no warning */ LI_PLUSSEC = (1 << 6), /* add a second (61 seconds) */ LI_MINUSSEC = (2 << 6), /* minus a second (59 seconds) */ LI_ALARM = (3 << 6), /* alarm condition */ /* Mode values */ MODE_RES0 = 0, /* reserved */ MODE_SYM_ACT = 1, /* symmetric active */ MODE_SYM_PAS = 2, /* symmetric passive */ MODE_CLIENT = 3, /* client */ MODE_SERVER = 4, /* server */ MODE_BROADCAST = 5, /* broadcast */ MODE_RES1 = 6, /* reserved for NTP control message */ MODE_RES2 = 7, /* reserved for private use */ }; //TODO: better base selection #define OFFSET_1900_1970 2208988800UL /* 1970 - 1900 in seconds */ #define NUM_DATAPOINTS 8 typedef struct { uint32_t int_partl; uint32_t fractionl; } l_fixedpt_t; typedef struct { uint16_t int_parts; uint16_t fractions; } s_fixedpt_t; typedef struct { uint8_t m_status; /* status of local clock and leap info */ uint8_t m_stratum; uint8_t m_ppoll; /* poll value */ int8_t m_precision_exp; s_fixedpt_t m_rootdelay; s_fixedpt_t m_rootdisp; uint32_t m_refid; l_fixedpt_t m_reftime; l_fixedpt_t m_orgtime; l_fixedpt_t m_rectime; l_fixedpt_t m_xmttime; uint32_t m_keyid; uint8_t m_digest[NTP_DIGESTSIZE]; } msg_t; typedef struct { double d_offset; double d_recv_time; double d_dispersion; } datapoint_t; typedef struct { len_and_sockaddr *p_lsa; char *p_dotted; int p_fd; int datapoint_idx; uint32_t lastpkt_refid; uint8_t lastpkt_status; uint8_t lastpkt_stratum; uint8_t reachable_bits; /* when to send new query (if p_fd == -1) * or when receive times out (if p_fd >= 0): */ double next_action_time; double p_xmttime; double p_raw_delay; /* p_raw_delay is set even by "high delay" packets */ /* lastpkt_delay isn't */ double lastpkt_recv_time; double lastpkt_delay; double lastpkt_rootdelay; double lastpkt_rootdisp; /* produced by filter algorithm: */ double filter_offset; double filter_dispersion; double filter_jitter; datapoint_t filter_datapoint[NUM_DATAPOINTS]; /* last sent packet: */ msg_t p_xmt_msg; } peer_t; #define USING_KERNEL_PLL_LOOP 1 #define USING_INITIAL_FREQ_ESTIMATION 0 enum { OPT_n = (1 << 0), OPT_q = (1 << 1), OPT_N = (1 << 2), OPT_x = (1 << 3), /* Insert new options above this line. */ /* Non-compat options: */ OPT_w = (1 << 4), OPT_p = (1 << 5), OPT_S = (1 << 6), OPT_l = (1 << 7) * ENABLE_FEATURE_NTPD_SERVER, OPT_I = (1 << 8) * ENABLE_FEATURE_NTPD_SERVER, /* We hijack some bits for other purposes */ OPT_qq = (1 << 31), }; struct globals { double cur_time; /* total round trip delay to currently selected reference clock */ double rootdelay; /* reference timestamp: time when the system clock was last set or corrected */ double reftime; /* total dispersion to currently selected reference clock */ double rootdisp; double last_script_run; char *script_name; llist_t *ntp_peers; #if ENABLE_FEATURE_NTPD_SERVER int listen_fd; char *if_name; # define G_listen_fd (G.listen_fd) #else # define G_listen_fd (-1) #endif unsigned verbose; unsigned peer_cnt; /* refid: 32-bit code identifying the particular server or reference clock * in stratum 0 packets this is a four-character ASCII string, * called the kiss code, used for debugging and monitoring * in stratum 1 packets this is a four-character ASCII string * assigned to the reference clock by IANA. Example: "GPS " * in stratum 2+ packets, it's IPv4 address or 4 first bytes * of MD5 hash of IPv6 */ uint32_t refid; 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 * system clock hardware representation is to the nanosecond. * * Delays, jitters of various kinds are clamped down to precision. * * If precision_sec is too large, discipline_jitter gets clamped to it * and if offset is smaller than discipline_jitter * POLLADJ_GATE, poll * interval grows even though we really can benefit from staying at * smaller one, collecting non-lagged datapoits and correcting offset. * (Lagged datapoits exist when poll_exp is large but we still have * systematic offset error - the time distance between datapoints * is significant and older datapoints have smaller offsets. * This makes our offset estimation a bit smaller than reality) * Due to this effect, setting G_precision_sec close to * STEP_THRESHOLD isn't such a good idea - offsets may grow * too big and we will step. I observed it with -6. * * OTOH, setting precision_sec far too small would result in futile * attempts to syncronize to an unachievable precision. * * -6 is 1/64 sec, -7 is 1/128 sec and so on. * -8 is 1/256 ~= 0.003906 (worked well for me --vda) * -9 is 1/512 ~= 0.001953 (let's try this for some time) */ #define G_precision_exp -9 /* * G_precision_exp is used only for construction outgoing packets. * It's ok to set G_precision_sec to a slightly different value * (One which is "nicer looking" in logs). * Exact value would be (1.0 / (1 << (- G_precision_exp))): */ #define G_precision_sec 0.002 uint8_t stratum; /* Bool. After set to 1, never goes back to 0: */ smallint initial_poll_complete; #define STATE_NSET 0 /* initial state, "nothing is set" */ //#define STATE_FSET 1 /* frequency set from file */ //#define STATE_SPIK 2 /* spike detected */ //#define STATE_FREQ 3 /* initial frequency */ #define STATE_SYNC 4 /* clock synchronized (normal operation) */ uint8_t discipline_state; // doc calls it c.state uint8_t poll_exp; // s.poll int polladj_count; // c.count long kernel_freq_drift; peer_t *last_update_peer; double last_update_offset; // c.last double last_update_recv_time; // s.t double discipline_jitter; // c.jitter /* Since we only compare it with ints, can simplify code * by not making this variable floating point: */ unsigned offset_to_jitter_ratio; //double cluster_offset; // s.offset //double cluster_jitter; // s.jitter #if !USING_KERNEL_PLL_LOOP double discipline_freq_drift; // c.freq /* Maybe conditionally calculate wander? it's used only for logging */ double discipline_wander; // c.wander #endif }; #define G (*ptr_to_globals) static const int const_IPTOS_LOWDELAY = IPTOS_LOWDELAY; #define VERB1 if (MAX_VERBOSE && G.verbose) #define VERB2 if (MAX_VERBOSE >= 2 && G.verbose >= 2) #define VERB3 if (MAX_VERBOSE >= 3 && G.verbose >= 3) #define VERB4 if (MAX_VERBOSE >= 4 && G.verbose >= 4) #define VERB5 if (MAX_VERBOSE >= 5 && G.verbose >= 5) #define VERB6 if (MAX_VERBOSE >= 6 && G.verbose >= 6) static double LOG2D(int a) { if (a < 0) return 1.0 / (1UL << -a); return 1UL << a; } static ALWAYS_INLINE double SQUARE(double x) { return x * x; } static ALWAYS_INLINE double MAXD(double a, double b) { if (a > b) return a; return b; } static ALWAYS_INLINE double MIND(double a, double b) { if (a < b) return a; return b; } static NOINLINE double my_SQRT(double X) { union { float f; int32_t i; } v; double invsqrt; double Xhalf = X * 0.5; /* Fast and good approximation to 1/sqrt(X), black magic */ v.f = X; /*v.i = 0x5f3759df - (v.i >> 1);*/ v.i = 0x5f375a86 - (v.i >> 1); /* - this constant is slightly better */ invsqrt = v.f; /* better than 0.2% accuracy */ /* Refining it using Newton's method: x1 = x0 - f(x0)/f'(x0) * f(x) = 1/(x*x) - X (f==0 when x = 1/sqrt(X)) * f'(x) = -2/(x*x*x) * f(x)/f'(x) = (X - 1/(x*x)) / (2/(x*x*x)) = X*x*x*x/2 - x/2 * x1 = x0 - (X*x0*x0*x0/2 - x0/2) = 1.5*x0 - X*x0*x0*x0/2 = x0*(1.5 - (X/2)*x0*x0) */ invsqrt = invsqrt * (1.5 - Xhalf * invsqrt * invsqrt); /* ~0.05% accuracy */ /* invsqrt = invsqrt * (1.5 - Xhalf * invsqrt * invsqrt); 2nd iter: ~0.0001% accuracy */ /* With 4 iterations, more than half results will be exact, * at 6th iterations result stabilizes with about 72% results exact. * We are well satisfied with 0.05% accuracy. */ return X * invsqrt; /* X * 1/sqrt(X) ~= sqrt(X) */ } static ALWAYS_INLINE double SQRT(double X) { /* If this arch doesn't use IEEE 754 floats, fall back to using libm */ if (sizeof(float) != 4) return sqrt(X); /* This avoids needing libm, saves about 0.5k on x86-32 */ return my_SQRT(X); } static double gettime1900d(void) { struct timeval tv; gettimeofday(&tv, NULL); /* never fails */ G.cur_time = tv.tv_sec + (1.0e-6 * tv.tv_usec) + OFFSET_1900_1970; return G.cur_time; } static void d_to_tv(double d, struct timeval *tv) { tv->tv_sec = (long)d; tv->tv_usec = (d - tv->tv_sec) * 1000000; } static double lfp_to_d(l_fixedpt_t lfp) { double ret; lfp.int_partl = ntohl(lfp.int_partl); lfp.fractionl = ntohl(lfp.fractionl); ret = (double)lfp.int_partl + ((double)lfp.fractionl / UINT_MAX); return ret; } static double sfp_to_d(s_fixedpt_t sfp) { double ret; sfp.int_parts = ntohs(sfp.int_parts); sfp.fractions = ntohs(sfp.fractions); ret = (double)sfp.int_parts + ((double)sfp.fractions / USHRT_MAX); return ret; } #if ENABLE_FEATURE_NTPD_SERVER static l_fixedpt_t d_to_lfp(double d) { l_fixedpt_t lfp; lfp.int_partl = (uint32_t)d; lfp.fractionl = (uint32_t)((d - lfp.int_partl) * UINT_MAX); lfp.int_partl = htonl(lfp.int_partl); lfp.fractionl = htonl(lfp.fractionl); return lfp; } static s_fixedpt_t d_to_sfp(double d) { s_fixedpt_t sfp; sfp.int_parts = (uint16_t)d; sfp.fractions = (uint16_t)((d - sfp.int_parts) * USHRT_MAX); sfp.int_parts = htons(sfp.int_parts); sfp.fractions = htons(sfp.fractions); return sfp; } #endif static double dispersion(const datapoint_t *dp) { return dp->d_dispersion + FREQ_TOLERANCE * (G.cur_time - dp->d_recv_time); } static double root_distance(peer_t *p) { /* The root synchronization distance is the maximum error due to * all causes of the local clock relative to the primary server. * It is defined as half the total delay plus total dispersion * plus peer jitter. */ return MAXD(MINDISP, p->lastpkt_rootdelay + p->lastpkt_delay) / 2 + p->lastpkt_rootdisp + p->filter_dispersion + FREQ_TOLERANCE * (G.cur_time - p->lastpkt_recv_time) + p->filter_jitter; } static void set_next(peer_t *p, unsigned t) { p->next_action_time = G.cur_time + t; } /* * Peer clock filter and its helpers */ static void filter_datapoints(peer_t *p) { int i, idx; double sum, wavg; datapoint_t *fdp; #if 0 /* Simulations have shown that use of *averaged* offset for p->filter_offset * is in fact worse than simply using last received one: with large poll intervals * (>= 2048) averaging code uses offset values which are outdated by hours, * and time/frequency correction goes totally wrong when fed essentially bogus offsets. */ int got_newest; double minoff, maxoff, w; double x = x; /* for compiler */ double oldest_off = oldest_off; double oldest_age = oldest_age; double newest_off = newest_off; double newest_age = newest_age; fdp = p->filter_datapoint; minoff = maxoff = fdp[0].d_offset; for (i = 1; i < NUM_DATAPOINTS; i++) { if (minoff > fdp[i].d_offset) minoff = fdp[i].d_offset; if (maxoff < fdp[i].d_offset) maxoff = fdp[i].d_offset; } idx = p->datapoint_idx; /* most recent datapoint's index */ /* Average offset: * Drop two outliers and take weighted average of the rest: * most_recent/2 + older1/4 + older2/8 ... + older5/32 + older6/32 * we use older6/32, not older6/64 since sum of weights should be 1: * 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/32 = 1 */ wavg = 0; w = 0.5; /* n-1 * --- dispersion(i) * filter_dispersion = \ ------------- * / (i+1) * --- 2 * i=0 */ got_newest = 0; sum = 0; for (i = 0; i < NUM_DATAPOINTS; i++) { VERB5 { bb_error_msg("datapoint[%d]: off:%f disp:%f(%f) age:%f%s", i, fdp[idx].d_offset, fdp[idx].d_dispersion, dispersion(&fdp[idx]), G.cur_time - fdp[idx].d_recv_time, (minoff == fdp[idx].d_offset || maxoff == fdp[idx].d_offset) ? " (outlier by offset)" : "" ); } sum += dispersion(&fdp[idx]) / (2 << i); if (minoff == fdp[idx].d_offset) { minoff -= 1; /* so that we don't match it ever again */ } else if (maxoff == fdp[idx].d_offset) { maxoff += 1; } else { oldest_off = fdp[idx].d_offset; oldest_age = G.cur_time - fdp[idx].d_recv_time; if (!got_newest) { got_newest = 1; newest_off = oldest_off; newest_age = oldest_age; } x = oldest_off * w; wavg += x; w /= 2; } idx = (idx - 1) & (NUM_DATAPOINTS - 1); } p->filter_dispersion = sum; wavg += x; /* add another older6/64 to form older6/32 */ /* Fix systematic underestimation with large poll intervals. * Imagine that we still have a bit of uncorrected drift, * and poll interval is big (say, 100 sec). Offsets form a progression: * 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 - 0.7 is most recent. * The algorithm above drops 0.0 and 0.7 as outliers, * and then we have this estimation, ~25% off from 0.7: * 0.1/32 + 0.2/32 + 0.3/16 + 0.4/8 + 0.5/4 + 0.6/2 = 0.503125 */ x = oldest_age - newest_age; if (x != 0) { x = newest_age / x; /* in above example, 100 / (600 - 100) */ if (x < 1) { /* paranoia check */ x = (newest_off - oldest_off) * x; /* 0.5 * 100/500 = 0.1 */ wavg += x; } } p->filter_offset = wavg; #else fdp = p->filter_datapoint; idx = p->datapoint_idx; /* most recent datapoint's index */ /* filter_offset: simply use the most recent value */ p->filter_offset = fdp[idx].d_offset; /* n-1 * --- dispersion(i) * filter_dispersion = \ ------------- * / (i+1) * --- 2 * i=0 */ wavg = 0; sum = 0; for (i = 0; i < NUM_DATAPOINTS; i++) { sum += dispersion(&fdp[idx]) / (2 << i); wavg += fdp[idx].d_offset; idx = (idx - 1) & (NUM_DATAPOINTS - 1); } wavg /= NUM_DATAPOINTS; p->filter_dispersion = sum; #endif /* +----- -----+ ^ 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 - fdp[i].d_offset); } sum = SQRT(sum / NUM_DATAPOINTS); p->filter_jitter = sum > G_precision_sec ? sum : G_precision_sec; VERB4 bb_error_msg("filter offset:%+f disp:%f jitter:%f", p->filter_offset, p->filter_dispersion, p->filter_jitter); } static void reset_peer_stats(peer_t *p, double offset) { int i; bool small_ofs = fabs(offset) < 16 * STEP_THRESHOLD; /* Used to set p->filter_datapoint[i].d_dispersion = MAXDISP * and clear reachable bits, but this proved to be too agressive: * after step (tested with suspinding laptop for ~30 secs), * this caused all previous data to be considered invalid, * making us needing to collect full ~8 datapoins per peer * after step in order to start trusting them. * In turn, this was making poll interval decrease even after * step was done. (Poll interval decreases already before step * in this scenario, because we see large offsets and end up with * no good peer to select). */ for (i = 0; i < NUM_DATAPOINTS; i++) { if (small_ofs) { p->filter_datapoint[i].d_recv_time += offset; if (p->filter_datapoint[i].d_offset != 0) { p->filter_datapoint[i].d_offset -= offset; //bb_error_msg("p->filter_datapoint[%d].d_offset %f -> %f", // i, // p->filter_datapoint[i].d_offset + offset, // p->filter_datapoint[i].d_offset); } } else { p->filter_datapoint[i].d_recv_time = G.cur_time; p->filter_datapoint[i].d_offset = 0; /*p->filter_datapoint[i].d_dispersion = MAXDISP;*/ } } if (small_ofs) { p->lastpkt_recv_time += offset; } else { /*p->reachable_bits = 0;*/ p->lastpkt_recv_time = G.cur_time; } filter_datapoints(p); /* recalc p->filter_xxx */ VERB6 bb_error_msg("%s->lastpkt_recv_time=%f", p->p_dotted, p->lastpkt_recv_time); } static void add_peers(const char *s) { peer_t *p; p = xzalloc(sizeof(*p)); p->p_lsa = xhost2sockaddr(s, 123); p->p_dotted = xmalloc_sockaddr2dotted_noport(&p->p_lsa->u.sa); p->p_fd = -1; p->p_xmt_msg.m_status = MODE_CLIENT | (NTP_VERSION << 3); p->next_action_time = G.cur_time; /* = set_next(p, 0); */ reset_peer_stats(p, 16 * STEP_THRESHOLD); llist_add_to(&G.ntp_peers, p); G.peer_cnt++; } static int do_sendto(int fd, const struct sockaddr *from, const struct sockaddr *to, socklen_t addrlen, msg_t *msg, ssize_t len) { ssize_t ret; errno = 0; if (!from) { ret = sendto(fd, msg, len, MSG_DONTWAIT, to, addrlen); } else { ret = send_to_from(fd, msg, len, MSG_DONTWAIT, to, from, addrlen); } if (ret != len) { bb_perror_msg("send failed"); return -1; } return 0; } static void 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); } */ if (p->p_fd == -1) { int fd, family; len_and_sockaddr *local_lsa; family = p->p_lsa->u.sa.sa_family; p->p_fd = fd = xsocket_type(&local_lsa, family, SOCK_DGRAM); /* local_lsa has "null" address and port 0 now. * bind() ensures we have a *particular port* selected by kernel * and remembered in p->p_fd, thus later recv(p->p_fd) * receives only packets sent to this port. */ PROBE_LOCAL_ADDR xbind(fd, &local_lsa->u.sa, local_lsa->len); PROBE_LOCAL_ADDR #if ENABLE_FEATURE_IPV6 if (family == AF_INET) #endif setsockopt(fd, IPPROTO_IP, IP_TOS, &const_IPTOS_LOWDELAY, sizeof(const_IPTOS_LOWDELAY)); free(local_lsa); } /* Emit message _before_ attempted send. Think of a very short * roundtrip networks: we need to go back to recv loop ASAP, * to reduce delay. Printing messages after send works against that. */ VERB1 bb_error_msg("sending query to %s", p->p_dotted); /* * Send out a random 64-bit number as our transmit time. The NTP * server will copy said number into the originate field on the * response that it sends us. This is totally legal per the SNTP spec. * * The impact of this is two fold: we no longer send out the current * system time for the world to see (which may aid an attacker), and * it gives us a (not very secure) way of knowing that we're not * getting spoofed by an attacker that can't capture our traffic * but can spoof packets from the NTP server we're communicating with. * * Save the real transmit timestamp locally. */ p->p_xmt_msg.m_xmttime.int_partl = rand(); p->p_xmt_msg.m_xmttime.fractionl = rand(); p->p_xmttime = gettime1900d(); /* Were doing it only if sendto worked, but * loss of sync detection needs reachable_bits updated * even if sending fails *locally*: * "network is unreachable" because cable was pulled? * We still need to declare "unsync" if this condition persists. */ p->reachable_bits <<= 1; if (do_sendto(p->p_fd, /*from:*/ NULL, /*to:*/ &p->p_lsa->u.sa, /*addrlen:*/ p->p_lsa->len, &p->p_xmt_msg, NTP_MSGSIZE_NOAUTH) == -1 ) { close(p->p_fd); p->p_fd = -1; /* * We know that we sent nothing. * We can retry *soon* without fearing * that we are flooding the peer. */ set_next(p, RETRY_INTERVAL); return; } set_next(p, RESPONSE_INTERVAL); } /* Note that there is no provision to prevent several run_scripts * to be started in quick succession. In fact, it happens rather often * if initial syncronization results in a step. * You will see "step" and then "stratum" script runs, sometimes * as close as only 0.002 seconds apart. * Script should be ready to deal with this. */ static void run_script(const char *action, double offset) { char *argv[3]; char *env1, *env2, *env3, *env4; G.last_script_run = G.cur_time; if (!G.script_name) return; argv[0] = (char*) G.script_name; argv[1] = (char*) action; argv[2] = NULL; VERB1 bb_error_msg("executing '%s %s'", G.script_name, action); env1 = xasprintf("%s=%u", "stratum", G.stratum); putenv(env1); env2 = xasprintf("%s=%ld", "freq_drift_ppm", G.kernel_freq_drift); putenv(env2); env3 = xasprintf("%s=%u", "poll_interval", 1 << G.poll_exp); putenv(env3); env4 = xasprintf("%s=%f", "offset", offset); putenv(env4); /* Other items of potential interest: selected peer, * rootdelay, reftime, rootdisp, refid, ntp_status, * last_update_offset, last_update_recv_time, discipline_jitter, * how many peers have reachable_bits = 0? */ /* Don't want to wait: it may run hwclock --systohc, and that * may take some time (seconds): */ /*spawn_and_wait(argv);*/ spawn(argv); unsetenv("stratum"); unsetenv("freq_drift_ppm"); unsetenv("poll_interval"); unsetenv("offset"); free(env1); free(env2); free(env3); free(env4); } static NOINLINE void step_time(double offset) { llist_t *item; double dtime; struct timeval tvc, tvn; char buf[sizeof("yyyy-mm-dd hh:mm:ss") + /*paranoia:*/ 4]; time_t tval; gettimeofday(&tvc, NULL); /* never fails */ dtime = tvc.tv_sec + (1.0e-6 * tvc.tv_usec) + offset; d_to_tv(dtime, &tvn); if (settimeofday(&tvn, NULL) == -1) bb_perror_msg_and_die("settimeofday"); VERB2 { tval = tvc.tv_sec; strftime_YYYYMMDDHHMMSS(buf, sizeof(buf), &tval); bb_error_msg("current time is %s.%06u", buf, (unsigned)tvc.tv_usec); } tval = tvn.tv_sec; strftime_YYYYMMDDHHMMSS(buf, sizeof(buf), &tval); bb_error_msg("setting time to %s.%06u (offset %+fs)", buf, (unsigned)tvn.tv_usec, offset); /* Correct various fields which contain time-relative values: */ /* Globals: */ G.cur_time += offset; G.last_update_recv_time += offset; G.last_script_run += offset; /* p->lastpkt_recv_time, p->next_action_time and such: */ for (item = G.ntp_peers; item != NULL; item = item->link) { peer_t *pp = (peer_t *) item->data; reset_peer_stats(pp, offset); //bb_error_msg("offset:%+f pp->next_action_time:%f -> %f", // offset, pp->next_action_time, pp->next_action_time + offset); pp->next_action_time += offset; if (pp->p_fd >= 0) { /* We wait for reply from this peer too. * But due to step we are doing, reply's data is no longer * useful (in fact, it'll be bogus). Stop waiting for it. */ close(pp->p_fd); pp->p_fd = -1; set_next(pp, RETRY_INTERVAL); } } } static void clamp_pollexp_and_set_MAXSTRAT(void) { if (G.poll_exp < MINPOLL) G.poll_exp = MINPOLL; if (G.poll_exp > BIGPOLL) G.poll_exp = BIGPOLL; G.polladj_count = 0; G.stratum = MAXSTRAT; } /* * Selection and clustering, and their helpers */ typedef struct { peer_t *p; int type; double edge; double opt_rd; /* optimization */ } point_t; static int compare_point_edge(const void *aa, const void *bb) { const point_t *a = aa; const point_t *b = bb; if (a->edge < b->edge) { return -1; } return (a->edge > b->edge); } typedef struct { peer_t *p; double metric; } survivor_t; static int compare_survivor_metric(const void *aa, const void *bb) { const survivor_t *a = aa; const survivor_t *b = bb; if (a->metric < b->metric) { return -1; } return (a->metric > b->metric); } static int fit(peer_t *p, double rd) { if ((p->reachable_bits & (p->reachable_bits-1)) == 0) { /* One or zero bits in reachable_bits */ VERB4 bb_error_msg("peer %s unfit for selection: unreachable", p->p_dotted); return 0; } #if 0 /* we filter out such packets earlier */ if ((p->lastpkt_status & LI_ALARM) == LI_ALARM || p->lastpkt_stratum >= MAXSTRAT ) { VERB4 bb_error_msg("peer %s unfit for selection: bad status/stratum", p->p_dotted); return 0; } #endif /* rd is root_distance(p) */ if (rd > MAXDIST + FREQ_TOLERANCE * (1 << G.poll_exp)) { VERB4 bb_error_msg("peer %s unfit for selection: root distance too high", p->p_dotted); return 0; } //TODO // /* Do we have a loop? */ // if (p->refid == p->dstaddr || p->refid == s.refid) // return 0; return 1; } static peer_t* select_and_cluster(void) { peer_t *p; llist_t *item; int i, j; int size = 3 * G.peer_cnt; /* for selection algorithm */ point_t point[size]; unsigned num_points, num_candidates; double low, high; unsigned num_falsetickers; /* for cluster algorithm */ survivor_t survivor[size]; unsigned num_survivors; /* Selection */ num_points = 0; item = G.ntp_peers; if (G.initial_poll_complete) while (item != NULL) { double rd, offset; p = (peer_t *) item->data; rd = root_distance(p); offset = p->filter_offset; if (!fit(p, rd)) { item = item->link; continue; } VERB5 bb_error_msg("interval: [%f %f %f] %s", offset - rd, offset, offset + rd, p->p_dotted ); point[num_points].p = p; point[num_points].type = -1; point[num_points].edge = offset - rd; point[num_points].opt_rd = rd; num_points++; point[num_points].p = p; point[num_points].type = 0; point[num_points].edge = offset; point[num_points].opt_rd = rd; num_points++; point[num_points].p = p; point[num_points].type = 1; point[num_points].edge = offset + rd; point[num_points].opt_rd = rd; num_points++; item = item->link; } num_candidates = num_points / 3; if (num_candidates == 0) { VERB3 bb_error_msg("no valid datapoints%s", ", no peer selected"); return NULL; } //TODO: sorting does not seem to be done in reference code qsort(point, num_points, sizeof(point[0]), compare_point_edge); /* Start with the assumption that there are no falsetickers. * Attempt to find a nonempty intersection interval containing * the midpoints of all truechimers. * If a nonempty interval cannot be found, increase the number * of assumed falsetickers by one and try again. * If a nonempty interval is found and the number of falsetickers * is less than the number of truechimers, a majority has been found * and the midpoint of each truechimer represents * the candidates available to the cluster algorithm. */ num_falsetickers = 0; while (1) { int c; unsigned num_midpoints = 0; low = 1 << 9; high = - (1 << 9); c = 0; for (i = 0; i < num_points; i++) { /* We want to do: * if (point[i].type == -1) c++; * if (point[i].type == 1) c--; * and it's simpler to do it this way: */ c -= point[i].type; if (c >= num_candidates - num_falsetickers) { /* If it was c++ and it got big enough... */ low = point[i].edge; break; } if (point[i].type == 0) num_midpoints++; } c = 0; for (i = num_points-1; i >= 0; i--) { c += point[i].type; if (c >= num_candidates - num_falsetickers) { high = point[i].edge; break; } if (point[i].type == 0) num_midpoints++; } /* If the number of midpoints is greater than the number * of allowed falsetickers, the intersection contains at * least one truechimer with no midpoint - bad. * Also, interval should be nonempty. */ if (num_midpoints <= num_falsetickers && low < high) break; num_falsetickers++; if (num_falsetickers * 2 >= num_candidates) { VERB3 bb_error_msg("falsetickers:%d, candidates:%d%s", num_falsetickers, num_candidates, ", no peer selected"); return NULL; } } VERB4 bb_error_msg("selected interval: [%f, %f]; candidates:%d falsetickers:%d", low, high, num_candidates, num_falsetickers); /* Clustering */ /* Construct a list of survivors (p, metric) * from the chime list, where metric is dominated * first by stratum and then by root distance. * All other things being equal, this is the order of preference. */ num_survivors = 0; for (i = 0; i < num_points; i++) { if (point[i].edge < low || point[i].edge > high) continue; p = point[i].p; survivor[num_survivors].p = p; /* x.opt_rd == root_distance(p); */ survivor[num_survivors].metric = MAXDIST * p->lastpkt_stratum + point[i].opt_rd; VERB5 bb_error_msg("survivor[%d] metric:%f peer:%s", num_survivors, survivor[num_survivors].metric, p->p_dotted); num_survivors++; } /* There must be at least MIN_SELECTED survivors to satisfy the * correctness assertions. Ordinarily, the Byzantine criteria * require four survivors, but for the demonstration here, one * is acceptable. */ if (num_survivors < MIN_SELECTED) { VERB3 bb_error_msg("survivors:%d%s", num_survivors, ", no peer selected"); return NULL; } //looks like this is ONLY used by the fact that later we pick survivor[0]. //we can avoid sorting then, just find the minimum once! qsort(survivor, num_survivors, sizeof(survivor[0]), compare_survivor_metric); /* For each association p in turn, calculate the selection * jitter p->sjitter as the square root of the sum of squares * (p->offset - q->offset) over all q associations. The idea is * to repeatedly discard the survivor with maximum selection * jitter until a termination condition is met. */ while (1) { unsigned max_idx = max_idx; double max_selection_jitter = max_selection_jitter; double min_jitter = min_jitter; if (num_survivors <= MIN_CLUSTERED) { VERB4 bb_error_msg("num_survivors %d <= %d, not discarding more", num_survivors, MIN_CLUSTERED); break; } /* To make sure a few survivors are left * for the clustering algorithm to chew on, * we stop if the number of survivors * is less than or equal to MIN_CLUSTERED (3). */ for (i = 0; i < num_survivors; i++) { double selection_jitter_sq; p = survivor[i].p; if (i == 0 || p->filter_jitter < min_jitter) min_jitter = p->filter_jitter; selection_jitter_sq = 0; for (j = 0; j < num_survivors; j++) { peer_t *q = survivor[j].p; selection_jitter_sq += SQUARE(p->filter_offset - q->filter_offset); } if (i == 0 || selection_jitter_sq > max_selection_jitter) { max_selection_jitter = selection_jitter_sq; max_idx = i; } VERB6 bb_error_msg("survivor %d selection_jitter^2:%f", i, selection_jitter_sq); } max_selection_jitter = SQRT(max_selection_jitter / num_survivors); VERB5 bb_error_msg("max_selection_jitter (at %d):%f min_jitter:%f", max_idx, max_selection_jitter, min_jitter); /* If the maximum selection jitter is less than the * minimum peer jitter, then tossing out more survivors * will not lower the minimum peer jitter, so we might * as well stop. */ if (max_selection_jitter < min_jitter) { VERB4 bb_error_msg("max_selection_jitter:%f < min_jitter:%f, num_survivors:%d, not discarding more", max_selection_jitter, min_jitter, num_survivors); break; } /* Delete survivor[max_idx] from the list * and go around again. */ VERB6 bb_error_msg("dropping survivor %d", max_idx); num_survivors--; while (max_idx < num_survivors) { survivor[max_idx] = survivor[max_idx + 1]; max_idx++; } } if (0) { /* Combine the offsets of the clustering algorithm survivors * using a weighted average with weight determined by the root * distance. Compute the selection jitter as the weighted RMS * difference between the first survivor and the remaining * survivors. In some cases the inherent clock jitter can be * reduced by not using this algorithm, especially when frequent * clockhopping is involved. bbox: thus we don't do it. */ double x, y, z, w; y = z = w = 0; for (i = 0; i < num_survivors; i++) { p = survivor[i].p; x = root_distance(p); y += 1 / x; z += p->filter_offset / x; w += SQUARE(p->filter_offset - survivor[0].p->filter_offset) / x; } //G.cluster_offset = z / y; //G.cluster_jitter = SQRT(w / y); } /* Pick the best clock. If the old system peer is on the list * and at the same stratum as the first survivor on the list, * then don't do a clock hop. Otherwise, select the first * survivor on the list as the new system peer. */ p = survivor[0].p; if (G.last_update_peer && G.last_update_peer->lastpkt_stratum <= p->lastpkt_stratum ) { /* Starting from 1 is ok here */ for (i = 1; i < num_survivors; i++) { if (G.last_update_peer == survivor[i].p) { VERB5 bb_error_msg("keeping old synced peer"); p = G.last_update_peer; goto keep_old; } } } G.last_update_peer = p; keep_old: VERB4 bb_error_msg("selected peer %s filter_offset:%+f age:%f", p->p_dotted, p->filter_offset, G.cur_time - p->lastpkt_recv_time ); return p; } /* * Local clock discipline and its helpers */ static void set_new_values(int disc_state, double offset, double recv_time) { /* Enter new state and set state variables. Note we use the time * of the last clock filter sample, which must be earlier than * the current time. */ VERB4 bb_error_msg("disc_state=%d last update offset=%f recv_time=%f", disc_state, offset, recv_time); G.discipline_state = disc_state; G.last_update_offset = offset; G.last_update_recv_time = recv_time; } /* Return: -1: decrease poll interval, 0: leave as is, 1: increase */ static NOINLINE int update_local_clock(peer_t *p) { int rc; struct timex tmx; /* Note: can use G.cluster_offset instead: */ double offset = p->filter_offset; double recv_time = p->lastpkt_recv_time; double abs_offset; #if !USING_KERNEL_PLL_LOOP double freq_drift; #endif #if !USING_KERNEL_PLL_LOOP || USING_INITIAL_FREQ_ESTIMATION double since_last_update; #endif double etemp, dtemp; abs_offset = fabs(offset); #if 0 /* If needed, -S script can do it by looking at $offset * env var and killing parent */ /* If the offset is too large, give up and go home */ if (abs_offset > PANIC_THRESHOLD) { bb_error_msg_and_die("offset %f far too big, exiting", offset); } #endif /* If this is an old update, for instance as the result * of a system peer change, avoid it. We never use * an old sample or the same sample twice. */ if (recv_time <= G.last_update_recv_time) { VERB3 bb_error_msg("update from %s: same or older datapoint, not using it", p->p_dotted); return 0; /* "leave poll interval as is" */ } /* Clock state machine transition function. This is where the * action is and defines how the system reacts to large time * and frequency errors. */ #if !USING_KERNEL_PLL_LOOP || USING_INITIAL_FREQ_ESTIMATION since_last_update = recv_time - G.reftime; #endif #if !USING_KERNEL_PLL_LOOP freq_drift = 0; #endif #if USING_INITIAL_FREQ_ESTIMATION if (G.discipline_state == STATE_FREQ) { /* Ignore updates until the stepout threshold */ if (since_last_update < WATCH_THRESHOLD) { VERB4 bb_error_msg("measuring drift, datapoint ignored, %f sec remains", 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 } #endif /* There are two main regimes: when the * offset exceeds the step threshold and when it does not. */ if (abs_offset > STEP_THRESHOLD) { #if 0 double remains; // This "spike state" seems to be useless, peer selection already drops // occassional "bad" datapoints. If we are here, there were _many_ // large offsets. When a few first large offsets are seen, // we end up in "no valid datapoints, no peer selected" state. // Only when enough of them are seen (which means it's not a fluke), // we end up here. Looks like _our_ clock is off. switch (G.discipline_state) { case STATE_SYNC: /* The first outlyer: ignore it, switch to SPIK state */ VERB3 bb_error_msg("update from %s: offset:%+f, spike%s", p->p_dotted, offset, ""); G.discipline_state = STATE_SPIK; return -1; /* "decrease poll interval" */ case STATE_SPIK: /* Ignore succeeding outlyers until either an inlyer * is found or the stepout threshold is exceeded. */ remains = WATCH_THRESHOLD - since_last_update; if (remains > 0) { VERB3 bb_error_msg("update from %s: offset:%+f, spike%s", p->p_dotted, offset, ", datapoint ignored"); return -1; /* "decrease poll interval" */ } /* fall through: we need to step */ } /* switch */ #endif /* Step the time and clamp down the poll interval. * * In NSET state an initial frequency correction is * not available, usually because the frequency file has * not yet been written. Since the time is outside the * capture range, the clock is stepped. The frequency * will be set directly following the stepout interval. * * In FSET state the initial frequency has been set * from the frequency file. Since the time is outside * the capture range, the clock is stepped immediately, * rather than after the stepout interval. Guys get * nervous if it takes 17 minutes to set the clock for * the first time. * * In SPIK state the stepout threshold has expired and * the phase is still above the step threshold. Note * that a single spike greater than the step threshold * is always suppressed, even at the longer poll * intervals. */ VERB4 bb_error_msg("stepping time by %+f; poll_exp=MINPOLL", offset); step_time(offset); if (option_mask32 & OPT_q) { /* We were only asked to set time once. Done. */ exit(0); } clamp_pollexp_and_set_MAXSTRAT(); run_script("step", offset); recv_time += offset; #if USING_INITIAL_FREQ_ESTIMATION if (G.discipline_state == STATE_NSET) { set_new_values(STATE_FREQ, /*offset:*/ 0, recv_time); return 1; /* "ok to increase poll interval" */ } #endif abs_offset = offset = 0; set_new_values(STATE_SYNC, offset, recv_time); } else { /* abs_offset <= STEP_THRESHOLD */ /* Compute the clock jitter as the RMS of exponentially * weighted offset differences. Used by the poll adjust code. */ etemp = SQUARE(G.discipline_jitter); dtemp = SQUARE(offset - G.last_update_offset); G.discipline_jitter = SQRT(etemp + (dtemp - etemp) / AVG); switch (G.discipline_state) { case STATE_NSET: if (option_mask32 & OPT_q) { /* We were only asked to set time once. * The clock is precise enough, no need to step. */ exit(0); } #if USING_INITIAL_FREQ_ESTIMATION /* This is the first update received and the frequency * has not been initialized. The first thing to do * is directly measure the oscillator frequency. */ set_new_values(STATE_FREQ, offset, recv_time); #else set_new_values(STATE_SYNC, offset, recv_time); #endif VERB4 bb_error_msg("transitioning to FREQ, datapoint ignored"); return 0; /* "leave poll interval as is" */ #if 0 /* this is dead code for now */ case STATE_FSET: /* This is the first update and the frequency * has been initialized. Adjust the phase, but * don't adjust the frequency until the next update. */ set_new_values(STATE_SYNC, offset, recv_time); /* freq_drift remains 0 */ break; #endif #if USING_INITIAL_FREQ_ESTIMATION case STATE_FREQ: /* since_last_update >= WATCH_THRESHOLD, we waited enough. * Correct the phase and frequency and switch to SYNC state. * freq_drift was already estimated (see code above) */ set_new_values(STATE_SYNC, offset, recv_time); break; #endif default: #if !USING_KERNEL_PLL_LOOP /* Compute freq_drift due to PLL and FLL contributions. * * The FLL and PLL frequency gain constants * depend on the poll interval and Allan * intercept. The FLL is not used below one-half * the Allan intercept. Above that the loop gain * increases in steps to 1 / AVG. */ if ((1 << G.poll_exp) > ALLAN / 2) { etemp = FLL - G.poll_exp; if (etemp < AVG) etemp = AVG; freq_drift += (offset - G.last_update_offset) / (MAXD(since_last_update, ALLAN) * etemp); } /* For the PLL the integration interval * (numerator) is the minimum of the update * interval and poll interval. This allows * oversampling, but not undersampling. */ 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; } if (G.stratum != p->lastpkt_stratum + 1) { G.stratum = p->lastpkt_stratum + 1; run_script("stratum", offset); } } if (G.discipline_jitter < G_precision_sec) G.discipline_jitter = G_precision_sec; G.offset_to_jitter_ratio = abs_offset / G.discipline_jitter; G.reftime = G.cur_time; 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(G.cluster_jitter)); dtemp += MAXD(p->filter_dispersion + FREQ_TOLERANCE * (G.cur_time - p->lastpkt_recv_time) + abs_offset, MINDISP); G.rootdisp = p->lastpkt_rootdisp + dtemp; VERB4 bb_error_msg("updating leap/refid/reftime/rootdisp from peer %s", p->p_dotted); /* We are in STATE_SYNC now, but did not do adjtimex yet. * (Any other state does not reach this, they all return earlier) * By this time, freq_drift and offset are set * to values suitable for adjtimex. */ #if !USING_KERNEL_PLL_LOOP /* Calculate the new frequency drift and frequency stability (wander). * Compute the clock wander as the RMS of exponentially weighted * frequency differences. This is not used directly, but can, * along with the jitter, be a highly useful monitoring and * debugging tool. */ dtemp = G.discipline_freq_drift + freq_drift; G.discipline_freq_drift = MAXD(MIND(MAXDRIFT, dtemp), -MAXDRIFT); etemp = SQUARE(G.discipline_wander); dtemp = SQUARE(dtemp); G.discipline_wander = SQRT(etemp + (dtemp - etemp) / AVG); VERB4 bb_error_msg("discipline freq_drift=%.9f(int:%ld corr:%e) wander=%f", G.discipline_freq_drift, (long)(G.discipline_freq_drift * 65536e6), freq_drift, G.discipline_wander); #endif VERB4 { memset(&tmx, 0, sizeof(tmx)); if (adjtimex(&tmx) < 0) bb_perror_msg_and_die("adjtimex"); bb_error_msg("p adjtimex freq:%ld offset:%+ld status:0x%x tc:%ld", tmx.freq, tmx.offset, tmx.status, tmx.constant); } memset(&tmx, 0, sizeof(tmx)); #if 0 //doesn't work, offset remains 0 (!) in kernel: //ntpd: set adjtimex freq:1786097 tmx.offset:77487 //ntpd: prev adjtimex freq:1786097 tmx.offset:0 //ntpd: cur adjtimex freq:1786097 tmx.offset:0 tmx.modes = ADJ_FREQUENCY | ADJ_OFFSET; /* 65536 is one ppm */ tmx.freq = G.discipline_freq_drift * 65536e6; #endif tmx.modes = ADJ_OFFSET | ADJ_STATUS | ADJ_TIMECONST;// | ADJ_MAXERROR | ADJ_ESTERROR; tmx.offset = (offset * 1000000); /* usec */ tmx.status = STA_PLL; 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; /* EXPERIMENTAL. * The below if statement should be unnecessary, but... * It looks like Linux kernel's PLL is far too gentle in changing * tmx.freq in response to clock offset. Offset keeps growing * and eventually we fall back to smaller poll intervals. * We can make correction more agressive (about x2) by supplying * PLL time constant which is one less than the real one. * To be on a safe side, let's do it only if offset is significantly * larger than jitter. */ if (tmx.constant > 0 && G.offset_to_jitter_ratio >= TIMECONST_HACK_GATE) tmx.constant--; //tmx.esterror = (uint32_t)(clock_jitter * 1e6); //tmx.maxerror = (uint32_t)((sys_rootdelay / 2 + sys_rootdisp) * 1e6); rc = adjtimex(&tmx); if (rc < 0) bb_perror_msg_and_die("adjtimex"); /* NB: here kernel returns constant == G.poll_exp, not == G.poll_exp - 4. * Not sure why. Perhaps it is normal. */ VERB4 bb_error_msg("adjtimex:%d freq:%ld offset:%+ld status:0x%x", rc, tmx.freq, tmx.offset, tmx.status); G.kernel_freq_drift = tmx.freq / 65536; VERB2 bb_error_msg("update from:%s offset:%+f jitter:%f clock drift:%+.3fppm tc:%d", p->p_dotted, offset, G.discipline_jitter, (double)tmx.freq / 65536, (int)tmx.constant); return 1; /* "ok to increase poll interval" */ } /* * We've got a new reply packet from a peer, process it * (helpers first) */ static unsigned poll_interval(int upper_bound) { unsigned interval, r, mask; interval = 1 << G.poll_exp; if (interval > upper_bound) interval = upper_bound; mask = ((interval-1) >> 4) | 1; r = rand(); interval += r & mask; /* ~ random(0..1) * interval/16 */ VERB4 bb_error_msg("chose poll interval:%u (poll_exp:%d)", interval, G.poll_exp); return interval; } static void adjust_poll(int count) { G.polladj_count += count; if (G.polladj_count > POLLADJ_LIMIT) { G.polladj_count = 0; if (G.poll_exp < MAXPOLL) { G.poll_exp++; VERB4 bb_error_msg("polladj: discipline_jitter:%f ++poll_exp=%d", G.discipline_jitter, G.poll_exp); } } else if (G.polladj_count < -POLLADJ_LIMIT || (count < 0 && G.poll_exp > BIGPOLL)) { G.polladj_count = 0; if (G.poll_exp > MINPOLL) { llist_t *item; G.poll_exp--; /* Correct p->next_action_time in each peer * which waits for sending, so that they send earlier. * Old pp->next_action_time are on the order * of t + (1 << old_poll_exp) + small_random, * we simply need to subtract ~half of that. */ for (item = G.ntp_peers; item != NULL; item = item->link) { peer_t *pp = (peer_t *) item->data; if (pp->p_fd < 0) pp->next_action_time -= (1 << G.poll_exp); } VERB4 bb_error_msg("polladj: discipline_jitter:%f --poll_exp=%d", G.discipline_jitter, G.poll_exp); } } else { VERB4 bb_error_msg("polladj: count:%d", G.polladj_count); } } static NOINLINE void recv_and_process_peer_pkt(peer_t *p) { int rc; ssize_t size; msg_t msg; double T1, T2, T3, T4; double offset; double prev_delay, delay; unsigned interval; datapoint_t *datapoint; peer_t *q; offset = 0; /* We can recvfrom here and check from.IP, but some multihomed * ntp servers reply from their *other IP*. * TODO: maybe we should check at least what we can: from.port == 123? */ recv_again: size = recv(p->p_fd, &msg, sizeof(msg), MSG_DONTWAIT); if (size < 0) { if (errno == EINTR) /* Signal caught */ goto recv_again; if (errno == EAGAIN) /* There was no packet after all * (poll() returning POLLIN for a fd * is not a ironclad guarantee that data is there) */ return; /* * If you need a different handling for a specific * errno, always explain it in comment. */ bb_perror_msg_and_die("recv(%s) error", p->p_dotted); } if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE) { bb_error_msg("malformed packet received from %s", p->p_dotted); return; } if (msg.m_orgtime.int_partl != p->p_xmt_msg.m_xmttime.int_partl || msg.m_orgtime.fractionl != p->p_xmt_msg.m_xmttime.fractionl ) { /* Somebody else's packet */ return; } /* We do not expect any more packets from this peer for now. * Closing the socket informs kernel about it. * We open a new socket when we send a new query. */ close(p->p_fd); p->p_fd = -1; if ((msg.m_status & LI_ALARM) == LI_ALARM || msg.m_stratum == 0 || msg.m_stratum > NTP_MAXSTRATUM ) { bb_error_msg("reply from %s: peer is unsynced", p->p_dotted); /* * 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. * If poll interval is small, increase it. */ if (G.poll_exp < BIGPOLL) goto increase_interval; goto pick_normal_interval; } // /* Verify valid root distance */ // if (msg.m_rootdelay / 2 + msg.m_rootdisp >= MAXDISP || p->lastpkt_reftime > msg.m_xmt) // return; /* invalid header values */ /* * From RFC 2030 (with a correction to the delay math): * * Timestamp Name ID When Generated * ------------------------------------------------------------ * Originate Timestamp T1 time request sent by client * Receive Timestamp T2 time request received by server * Transmit Timestamp T3 time reply sent by server * Destination Timestamp T4 time reply received by client * * The roundtrip delay and local clock offset are defined as * * delay = (T4 - T1) - (T3 - T2); offset = ((T2 - T1) + (T3 - T4)) / 2 */ T1 = p->p_xmttime; T2 = lfp_to_d(msg.m_rectime); T3 = lfp_to_d(msg.m_xmttime); T4 = G.cur_time; /* 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. */ delay = (T4 - T1) - (T3 - T2); if (delay < G_precision_sec) 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. */ prev_delay = p->p_raw_delay; p->p_raw_delay = delay; if (p->reachable_bits && delay > prev_delay * BAD_DELAY_GROWTH) { bb_error_msg("reply from %s: delay %f is too high, ignoring", p->p_dotted, delay); goto pick_normal_interval; } p->lastpkt_delay = delay; p->lastpkt_recv_time = T4; VERB6 bb_error_msg("%s->lastpkt_recv_time=%f", p->p_dotted, p->lastpkt_recv_time); 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; 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 = 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 */ int i; for (i = 0; i < NUM_DATAPOINTS; i++) { p->filter_datapoint[i].d_offset = offset; } } p->reachable_bits |= 1; if ((MAX_VERBOSE && G.verbose) || (option_mask32 & OPT_w)) { bb_error_msg("reply from %s: offset:%+f delay:%f status:0x%02x strat:%d refid:0x%08x rootdelay:%f reach:0x%02x", p->p_dotted, offset, p->lastpkt_delay, p->lastpkt_status, p->lastpkt_stratum, p->lastpkt_refid, p->lastpkt_rootdelay, p->reachable_bits /* not shown: m_ppoll, m_precision_exp, m_rootdisp, * m_reftime, m_orgtime, m_rectime, m_xmttime */ ); } /* Muck with statictics and update the clock */ filter_datapoints(p); q = select_and_cluster(); rc = 0; if (q) { if (!(option_mask32 & OPT_w)) { rc = update_local_clock(q); #if 0 //Disabled this because there is a case where largish offsets //are unavoidable: if network round-trip delay is, say, ~0.6s, //error in offset estimation would be ~delay/2 ~= 0.3s. //Thus, offsets will be usually in -0.3...0.3s range. //In this case, this code would keep poll interval small, //but it won't be helping. //BIGOFF check below deals with a case of seeing multi-second offsets. /* If drift is dangerously large, immediately * drop poll interval one step down. */ if (fabs(q->filter_offset) >= POLLDOWN_OFFSET) { VERB4 bb_error_msg("offset:%+f > POLLDOWN_OFFSET", q->filter_offset); adjust_poll(-POLLADJ_LIMIT * 3); rc = 0; } #endif } } else { /* No peer selected. * If poll interval is small, increase it. */ if (G.poll_exp < BIGPOLL) goto increase_interval; } if (rc != 0) { /* Adjust the poll interval by comparing the current offset * with the clock jitter. If the offset is less than * the clock jitter times a constant, then the averaging interval * is increased, otherwise it is decreased. A bit of hysteresis * helps calm the dance. Works best using burst mode. */ if (rc > 0 && G.offset_to_jitter_ratio <= POLLADJ_GATE) { /* was += G.poll_exp but it is a bit * too optimistic for my taste at high poll_exp's */ increase_interval: adjust_poll(MINPOLL); } else { adjust_poll(-G.poll_exp * 2); } } /* Decide when to send new query for this peer */ pick_normal_interval: interval = poll_interval(INT_MAX); if (fabs(offset) >= BIGOFF && interval > BIGOFF_INTERVAL) { /* If we are synced, offsets are less than STEP_THRESHOLD, * or at the very least not much larger than it. * Now we see a largish one. * Either this peer is feeling bad, or packet got corrupted, * or _our_ clock is wrong now and _all_ peers will show similar * largish offsets too. * I observed this with laptop suspend stopping clock. * In any case, it makes sense to make next request soonish: * cases 1 and 2: get a better datapoint, * case 3: allows to resync faster. */ interval = BIGOFF_INTERVAL; } set_next(p, interval); } #if ENABLE_FEATURE_NTPD_SERVER static NOINLINE void recv_and_process_client_pkt(void /*int fd*/) { ssize_t size; //uint8_t version; len_and_sockaddr *to; struct sockaddr *from; msg_t msg; uint8_t query_status; l_fixedpt_t query_xmttime; to = get_sock_lsa(G_listen_fd); from = xzalloc(to->len); size = recv_from_to(G_listen_fd, &msg, sizeof(msg), MSG_DONTWAIT, from, &to->u.sa, to->len); if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE) { char *addr; if (size < 0) { if (errno == EAGAIN) goto bail; bb_perror_msg_and_die("recv"); } addr = xmalloc_sockaddr2dotted_noport(from); bb_error_msg("malformed packet received from %s: size %u", addr, (int)size); free(addr); goto bail; } query_status = msg.m_status; query_xmttime = msg.m_xmttime; /* Build a reply packet */ memset(&msg, 0, sizeof(msg)); msg.m_status = G.stratum < MAXSTRAT ? (G.ntp_status & LI_MASK) : LI_ALARM; msg.m_status |= (query_status & VERSION_MASK); msg.m_status |= ((query_status & MODE_MASK) == MODE_CLIENT) ? MODE_SERVER : MODE_SYM_PAS; msg.m_stratum = G.stratum; msg.m_ppoll = G.poll_exp; msg.m_precision_exp = G_precision_exp; /* this time was obtained between poll() and recv() */ msg.m_rectime = d_to_lfp(G.cur_time); msg.m_xmttime = d_to_lfp(gettime1900d()); /* this instant */ if (G.peer_cnt == 0) { /* we have no peers: "stratum 1 server" mode. reftime = our own time */ G.reftime = G.cur_time; } msg.m_reftime = d_to_lfp(G.reftime); msg.m_orgtime = query_xmttime; msg.m_rootdelay = d_to_sfp(G.rootdelay); //simple code does not do this, fix simple code! msg.m_rootdisp = d_to_sfp(G.rootdisp); //version = (query_status & VERSION_MASK); /* ... >> VERSION_SHIFT - done below instead */ msg.m_refid = G.refid; // (version > (3 << VERSION_SHIFT)) ? G.refid : G.refid3; /* We reply from the local address packet was sent to, * this makes to/from look swapped here: */ do_sendto(G_listen_fd, /*from:*/ &to->u.sa, /*to:*/ from, /*addrlen:*/ to->len, &msg, size); bail: free(to); free(from); } #endif /* Upstream ntpd's options: * * -4 Force DNS resolution of host names to the IPv4 namespace. * -6 Force DNS resolution of host names to the IPv6 namespace. * -a Require cryptographic authentication for broadcast client, * multicast client and symmetric passive associations. * This is the default. * -A Do not require cryptographic authentication for broadcast client, * multicast client and symmetric passive associations. * This is almost never a good idea. * -b Enable the client to synchronize to broadcast servers. * -c conffile * Specify the name and path of the configuration file, * default /etc/ntp.conf * -d Specify debugging mode. This option may occur more than once, * with each occurrence indicating greater detail of display. * -D level * Specify debugging level directly. * -f driftfile * Specify the name and path of the frequency file. * This is the same operation as the "driftfile FILE" * configuration command. * -g Normally, ntpd exits with a message to the system log * if the offset exceeds the panic threshold, which is 1000 s * by default. This option allows the time to be set to any value * without restriction; however, this can happen only once. * If the threshold is exceeded after that, ntpd will exit * with a message to the system log. This option can be used * with the -q and -x options. See the tinker command for other options. * -i jaildir * Chroot the server to the directory jaildir. This option also implies * that the server attempts to drop root privileges at startup * (otherwise, chroot gives very little additional security). * You may need to also specify a -u option. * -k keyfile * Specify the name and path of the symmetric key file, * default /etc/ntp/keys. This is the same operation * as the "keys FILE" configuration command. * -l logfile * Specify the name and path of the log file. The default * is the system log file. This is the same operation as * the "logfile FILE" configuration command. * -L Do not listen to virtual IPs. The default is to listen. * -n Don't fork. * -N To the extent permitted by the operating system, * run the ntpd at the highest priority. * -p pidfile * Specify the name and path of the file used to record the ntpd * process ID. This is the same operation as the "pidfile FILE" * configuration command. * -P priority * To the extent permitted by the operating system, * run the ntpd at the specified priority. * -q Exit the ntpd just after the first time the clock is set. * This behavior mimics that of the ntpdate program, which is * to be retired. The -g and -x options can be used with this option. * Note: The kernel time discipline is disabled with this option. * -r broadcastdelay * Specify the default propagation delay from the broadcast/multicast * server to this client. This is necessary only if the delay * cannot be computed automatically by the protocol. * -s statsdir * Specify the directory path for files created by the statistics * facility. This is the same operation as the "statsdir DIR" * configuration command. * -t key * Add a key number to the trusted key list. This option can occur * more than once. * -u user[:group] * Specify a user, and optionally a group, to switch to. * -v variable * -V variable * Add a system variable listed by default. * -x Normally, the time is slewed if the offset is less than the step * threshold, which is 128 ms by default, and stepped if above * the threshold. This option sets the threshold to 600 s, which is * well within the accuracy window to set the clock manually. * Note: since the slew rate of typical Unix kernels is limited * to 0.5 ms/s, each second of adjustment requires an amortization * interval of 2000 s. Thus, an adjustment as much as 600 s * will take almost 14 days to complete. This option can be used * with the -g and -q options. See the tinker command for other options. * Note: The kernel time discipline is disabled with this option. */ /* By doing init in a separate function we decrease stack usage * in main loop. */ static NOINLINE void ntp_init(char **argv) { unsigned opts; llist_t *peers; srand(getpid()); if (getuid()) bb_error_msg_and_die(bb_msg_you_must_be_root); /* Set some globals */ G.stratum = MAXSTRAT; if (BURSTPOLL != 0) G.poll_exp = BURSTPOLL; /* speeds up initial sync */ G.last_script_run = G.reftime = G.last_update_recv_time = gettime1900d(); /* sets G.cur_time too */ /* Parse options */ peers = NULL; opt_complementary = "dd:p::wn" /* -d: counter; -p: list; -w implies -n */ IF_FEATURE_NTPD_SERVER(":Il"); /* -I implies -l */ opts = getopt32(argv, "nqNx" /* compat */ "wp:S:"IF_FEATURE_NTPD_SERVER("l") /* NOT compat */ IF_FEATURE_NTPD_SERVER("I:") /* compat */ "d" /* compat */ "46aAbgL", /* compat, ignored */ &peers,&G.script_name, #if ENABLE_FEATURE_NTPD_SERVER &G.if_name, #endif &G.verbose); // if (opts & OPT_x) /* disable stepping, only slew is allowed */ // G.time_was_stepped = 1; if (peers) { while (peers) add_peers(llist_pop(&peers)); } #if ENABLE_FEATURE_NTPD_CONF else { parser_t *parser; char *token[3]; parser = config_open("/etc/ntp.conf"); while (config_read(parser, token, 3, 1, "# \t", PARSE_NORMAL)) { if (strcmp(token[0], "server") == 0 && token[1]) { add_peers(token[1]); continue; } bb_error_msg("skipping %s:%u: unimplemented command '%s'", "/etc/ntp.conf", parser->lineno, token[0] ); } config_close(parser); } #endif if (G.peer_cnt == 0) { if (!(opts & OPT_l)) bb_show_usage(); /* -l but no peers: "stratum 1 server" mode */ G.stratum = 1; } #if ENABLE_FEATURE_NTPD_SERVER G_listen_fd = -1; if (opts & OPT_l) { G_listen_fd = create_and_bind_dgram_or_die(NULL, 123); if (opts & OPT_I) { if (setsockopt_bindtodevice(G_listen_fd, G.if_name)) xfunc_die(); } socket_want_pktinfo(G_listen_fd); setsockopt(G_listen_fd, IPPROTO_IP, IP_TOS, &const_IPTOS_LOWDELAY, sizeof(const_IPTOS_LOWDELAY)); } #endif if (!(opts & OPT_n)) { bb_daemonize_or_rexec(DAEMON_DEVNULL_STDIO, argv); logmode = LOGMODE_NONE; } /* I hesitate to set -20 prio. -15 should be high enough for timekeeping */ if (opts & OPT_N) setpriority(PRIO_PROCESS, 0, -15); /* If network is up, syncronization occurs in ~10 seconds. * We give "ntpd -q" 10 seconds to get first reply, * then another 50 seconds to finish syncing. * * I tested ntpd 4.2.6p1 and apparently it never exits * (will try forever), but it does not feel right. * The goal of -q is to act like ntpdate: set time * after a reasonably small period of polling, or fail. */ if (opts & OPT_q) { option_mask32 |= OPT_qq; alarm(10); } bb_signals(0 | (1 << SIGTERM) | (1 << SIGINT) | (1 << SIGALRM) , record_signo ); bb_signals(0 | (1 << SIGPIPE) | (1 << SIGCHLD) , SIG_IGN ); } int ntpd_main(int argc UNUSED_PARAM, char **argv) MAIN_EXTERNALLY_VISIBLE; int ntpd_main(int argc UNUSED_PARAM, char **argv) { #undef G struct globals G; struct pollfd *pfd; peer_t **idx2peer; unsigned cnt; memset(&G, 0, sizeof(G)); SET_PTR_TO_GLOBALS(&G); ntp_init(argv); /* If ENABLE_FEATURE_NTPD_SERVER, + 1 for listen_fd: */ cnt = G.peer_cnt + ENABLE_FEATURE_NTPD_SERVER; idx2peer = xzalloc(sizeof(idx2peer[0]) * cnt); pfd = xzalloc(sizeof(pfd[0]) * cnt); /* Countdown: we never sync before we sent INITIAL_SAMPLES+1 * packets to each peer. * NB: if some peer is not responding, we may end up sending * fewer packets to it and more to other peers. * NB2: sync usually happens using INITIAL_SAMPLES packets, * since last reply does not come back instantaneously. */ cnt = G.peer_cnt * (INITIAL_SAMPLES + 1); write_pidfile(CONFIG_PID_FILE_PATH "/ntpd.pid"); while (!bb_got_signal) { llist_t *item; unsigned i, j; int nfds, timeout; double nextaction; /* Nothing between here and poll() blocks for any significant time */ nextaction = G.cur_time + 3600; i = 0; #if ENABLE_FEATURE_NTPD_SERVER if (G_listen_fd != -1) { pfd[0].fd = G_listen_fd; pfd[0].events = POLLIN; i++; } #endif /* Pass over peer list, send requests, time out on receives */ for (item = G.ntp_peers; item != NULL; item = item->link) { peer_t *p = (peer_t *) item->data; if (p->next_action_time <= G.cur_time) { if (p->p_fd == -1) { /* Time to send new req */ if (--cnt == 0) { VERB4 bb_error_msg("disabling burst mode"); G.polladj_count = 0; G.poll_exp = MINPOLL; G.initial_poll_complete = 1; } send_query_to_peer(p); } else { /* Timed out waiting for reply */ close(p->p_fd); p->p_fd = -1; /* If poll interval is small, increase it */ if (G.poll_exp < BIGPOLL) adjust_poll(MINPOLL); timeout = poll_interval(NOREPLY_INTERVAL); bb_error_msg("timed out waiting for %s, reach 0x%02x, next query in %us", p->p_dotted, p->reachable_bits, timeout); set_next(p, timeout); } } if (p->next_action_time < nextaction) nextaction = p->next_action_time; if (p->p_fd >= 0) { /* Wait for reply from this peer */ pfd[i].fd = p->p_fd; pfd[i].events = POLLIN; idx2peer[i] = p; i++; } } timeout = nextaction - G.cur_time; if (timeout < 0) timeout = 0; timeout++; /* (nextaction - G.cur_time) rounds down, compensating */ /* Here we may block */ VERB2 { if (i > (ENABLE_FEATURE_NTPD_SERVER && G_listen_fd != -1)) { /* We wait for at least one reply. * Poll for it, without wasting time for message. * Since replies often come under 1 second, this also * reduces clutter in logs. */ nfds = poll(pfd, i, 1000); if (nfds != 0) goto did_poll; if (--timeout <= 0) goto did_poll; } bb_error_msg("poll:%us sockets:%u interval:%us", timeout, i, 1 << G.poll_exp); } nfds = poll(pfd, i, timeout * 1000); did_poll: gettime1900d(); /* sets G.cur_time */ if (nfds <= 0) { if (!bb_got_signal /* poll wasn't interrupted by a signal */ && G.cur_time - G.last_script_run > 11*60 ) { /* Useful for updating battery-backed RTC and such */ run_script("periodic", G.last_update_offset); gettime1900d(); /* sets G.cur_time */ } goto check_unsync; } /* Process any received packets */ j = 0; #if ENABLE_FEATURE_NTPD_SERVER if (G.listen_fd != -1) { if (pfd[0].revents /* & (POLLIN|POLLERR)*/) { nfds--; recv_and_process_client_pkt(/*G.listen_fd*/); gettime1900d(); /* sets G.cur_time */ } j = 1; } #endif for (; nfds != 0 && j < i; j++) { if (pfd[j].revents /* & (POLLIN|POLLERR)*/) { /* * At init, alarm was set to 10 sec. * Now we did get a reply. * Increase timeout to 50 seconds to finish syncing. */ if (option_mask32 & OPT_qq) { option_mask32 &= ~OPT_qq; alarm(50); } nfds--; recv_and_process_peer_pkt(idx2peer[j]); gettime1900d(); /* sets G.cur_time */ } } check_unsync: 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 */ clamp_pollexp_and_set_MAXSTRAT(); run_script("unsync", 0.0); have_reachable_peer: ; } } /* while (!bb_got_signal) */ remove_pidfile(CONFIG_PID_FILE_PATH "/ntpd.pid"); kill_myself_with_sig(bb_got_signal); } /*** openntpd-4.6 uses only adjtime, not adjtimex ***/ /*** ntp-4.2.6/ntpd/ntp_loopfilter.c - adjtimex usage ***/ #if 0 static double direct_freq(double fp_offset) { #ifdef KERNEL_PLL /* * If the kernel is enabled, we need the residual offset to * calculate the frequency correction. */ if (pll_control && kern_enable) { memset(&ntv, 0, sizeof(ntv)); ntp_adjtime(&ntv); #ifdef STA_NANO clock_offset = ntv.offset / 1e9; #else /* STA_NANO */ clock_offset = ntv.offset / 1e6; #endif /* STA_NANO */ drift_comp = FREQTOD(ntv.freq); } #endif /* KERNEL_PLL */ set_freq((fp_offset - clock_offset) / (current_time - clock_epoch) + drift_comp); wander_resid = 0; return drift_comp; } static void set_freq(double freq) /* frequency update */ { char tbuf[80]; drift_comp = freq; #ifdef KERNEL_PLL /* * If the kernel is enabled, update the kernel frequency. */ if (pll_control && kern_enable) { memset(&ntv, 0, sizeof(ntv)); ntv.modes = MOD_FREQUENCY; ntv.freq = DTOFREQ(drift_comp); ntp_adjtime(&ntv); snprintf(tbuf, sizeof(tbuf), "kernel %.3f PPM", drift_comp * 1e6); report_event(EVNT_FSET, NULL, tbuf); } else { snprintf(tbuf, sizeof(tbuf), "ntpd %.3f PPM", drift_comp * 1e6); report_event(EVNT_FSET, NULL, tbuf); } #else /* KERNEL_PLL */ snprintf(tbuf, sizeof(tbuf), "ntpd %.3f PPM", drift_comp * 1e6); report_event(EVNT_FSET, NULL, tbuf); #endif /* KERNEL_PLL */ } ... ... ... #ifdef KERNEL_PLL /* * This code segment works when clock adjustments are made using * precision time kernel support and the ntp_adjtime() system * call. This support is available in Solaris 2.6 and later, * Digital Unix 4.0 and later, FreeBSD, Linux and specially * modified kernels for HP-UX 9 and Ultrix 4. In the case of the * DECstation 5000/240 and Alpha AXP, additional kernel * modifications provide a true microsecond clock and nanosecond * clock, respectively. * * Important note: The kernel discipline is used only if the * step threshold is less than 0.5 s, as anything higher can * lead to overflow problems. This might occur if some misguided * lad set the step threshold to something ridiculous. */ if (pll_control && kern_enable) { #define MOD_BITS (MOD_OFFSET | MOD_MAXERROR | MOD_ESTERROR | MOD_STATUS | MOD_TIMECONST) /* * We initialize the structure for the ntp_adjtime() * system call. We have to convert everything to * microseconds or nanoseconds first. Do not update the * system variables if the ext_enable flag is set. In * this case, the external clock driver will update the * variables, which will be read later by the local * clock driver. Afterwards, remember the time and * frequency offsets for jitter and stability values and * to update the frequency file. */ memset(&ntv, 0, sizeof(ntv)); if (ext_enable) { ntv.modes = MOD_STATUS; } else { #ifdef STA_NANO ntv.modes = MOD_BITS | MOD_NANO; #else /* STA_NANO */ ntv.modes = MOD_BITS; #endif /* STA_NANO */ if (clock_offset < 0) dtemp = -.5; else dtemp = .5; #ifdef STA_NANO ntv.offset = (int32)(clock_offset * 1e9 + dtemp); ntv.constant = sys_poll; #else /* STA_NANO */ ntv.offset = (int32)(clock_offset * 1e6 + dtemp); ntv.constant = sys_poll - 4; #endif /* STA_NANO */ ntv.esterror = (u_int32)(clock_jitter * 1e6); ntv.maxerror = (u_int32)((sys_rootdelay / 2 + sys_rootdisp) * 1e6); ntv.status = STA_PLL; /* * Enable/disable the PPS if requested. */ if (pps_enable) { if (!(pll_status & STA_PPSTIME)) report_event(EVNT_KERN, NULL, "PPS enabled"); ntv.status |= STA_PPSTIME | STA_PPSFREQ; } else { if (pll_status & STA_PPSTIME) report_event(EVNT_KERN, NULL, "PPS disabled"); ntv.status &= ~(STA_PPSTIME | STA_PPSFREQ); } if (sys_leap == LEAP_ADDSECOND) ntv.status |= STA_INS; else if (sys_leap == LEAP_DELSECOND) ntv.status |= STA_DEL; } /* * Pass the stuff to the kernel. If it squeals, turn off * the pps. In any case, fetch the kernel offset, * frequency and jitter. */ if (ntp_adjtime(&ntv) == TIME_ERROR) { if (!(ntv.status & STA_PPSSIGNAL)) report_event(EVNT_KERN, NULL, "PPS no signal"); } pll_status = ntv.status; #ifdef STA_NANO clock_offset = ntv.offset / 1e9; #else /* STA_NANO */ clock_offset = ntv.offset / 1e6; #endif /* STA_NANO */ clock_frequency = FREQTOD(ntv.freq); /* * If the kernel PPS is lit, monitor its performance. */ if (ntv.status & STA_PPSTIME) { #ifdef STA_NANO clock_jitter = ntv.jitter / 1e9; #else /* STA_NANO */ clock_jitter = ntv.jitter / 1e6; #endif /* STA_NANO */ } #if defined(STA_NANO) && NTP_API == 4 /* * If the TAI changes, update the kernel TAI. */ if (loop_tai != sys_tai) { loop_tai = sys_tai; ntv.modes = MOD_TAI; ntv.constant = sys_tai; ntp_adjtime(&ntv); } #endif /* STA_NANO */ } #endif /* KERNEL_PLL */ #endif