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- /*
- * NTP client/server, based on OpenNTPD 3.9p1
- *
- * Busybox port author: Adam Tkac (C) 2009 <vonsch@gmail.com>
- *
- * OpenNTPd 3.9p1 copyright holders:
- * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
- * Copyright (c) 2004 Alexander Guy <alexander.guy@andern.org>
- *
- * OpenNTPd code is licensed under ISC-style licence:
- *
- * Permission to use, copy, modify, and distribute this software for any
- * purpose with or without fee is hereby granted, provided that the above
- * copyright notice and this permission notice appear in all copies.
- *
- * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
- * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
- * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
- * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
- * WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
- * IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
- * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
- ***********************************************************************
- *
- * Parts of OpenNTPD clock syncronization code is replaced by
- * code which is based on ntp-4.2.6, which 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.
- ***********************************************************************
- */
- //config:config NTPD
- //config: bool "ntpd (17 kb)"
- //config: default y
- //config: select PLATFORM_LINUX
- //config: help
- //config: The NTP client/server daemon.
- //config:
- //config:config FEATURE_NTPD_SERVER
- //config: bool "Make ntpd usable as a NTP server"
- //config: default y
- //config: depends on NTPD
- //config: help
- //config: Make ntpd usable as a NTP server. If you disable this option
- //config: ntpd will be usable only as a NTP client.
- //config:
- //config:config FEATURE_NTPD_CONF
- //config: bool "Make ntpd understand /etc/ntp.conf"
- //config: default y
- //config: depends on NTPD
- //config: help
- //config: Make ntpd look in /etc/ntp.conf for peers. Only "server address"
- //config: is supported.
- //applet:IF_NTPD(APPLET(ntpd, BB_DIR_USR_SBIN, BB_SUID_DROP))
- //kbuild:lib-$(CONFIG_NTPD) += ntpd.o
- //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 (may be repeated)"
- //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: "\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, 'server HOST' lines"
- //usage: "\n from /etc/ntp.conf are used"
- //usage: )
- //usage: IF_FEATURE_NTPD_SERVER(
- //usage: "\n -l Also run as server on port 123"
- //usage: "\n -I IFACE Bind server to IFACE, implies -l"
- //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 <math.h>
- #include <netinet/ip.h> /* For IPTOS_DSCP_AF21 definition */
- #include <sys/timex.h>
- #ifndef IPTOS_DSCP_AF21
- # define IPTOS_DSCP_AF21 0x48
- #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 == 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 MIN_FREQHOLD 10 /* adjust offset, but not freq in this many first adjustments */
- #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 */
- #define HOSTNAME_INTERVAL 4 /* hostname lookup failed. Wait N * peer->dns_errors secs for next try */
- #define DNS_ERRORS_CAP 0x3f /* peer->dns_errors is in [0..63] */
- /* Step threshold (sec). std ntpd uses 0.128.
- */
- #define STEP_THRESHOLD 1
- /* Slew threshold (sec): adjtimex() won't accept offsets larger than this.
- * Using exact power of 2 (1/8) results in smaller code
- */
- #define SLEW_THRESHOLD 0.125
- //^^^^^^^^^^^^^^^^^^^^^^^^^^ TODO: man adjtimex about tmx.offset:
- // "Since Linux 2.6.26, the supplied value is clamped to the range (-0.5s, +0.5s)"
- // - can use this larger value instead?
- /* Stepout threshold (sec). std ntpd uses 900 (11 mins (!)) */
- //UNUSED: #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
- #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 SLEW_THRESHOLD = 0.125, it means we try to sync more aggressively
- * if offset increases over ~0.04 sec
- */
- //#define POLLDOWN_OFFSET (SLEW_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;
- uint8_t dns_errors;
- /* 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;
- char p_hostname[1];
- } 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 synchronize 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;
- #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
- int FREQHOLD_cnt;
- 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)
- #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) < STEP_THRESHOLD;
- /* Used to set p->filter_datapoint[i].d_dispersion = MAXDISP
- * and clear reachable bits, but this proved to be too aggressive:
- * after step (tested with suspending laptop for ~30 secs),
- * this caused all previous data to be considered invalid,
- * making us needing to collect full ~8 datapoints 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 len_and_sockaddr*
- resolve_peer_hostname(peer_t *p)
- {
- len_and_sockaddr *lsa = host2sockaddr(p->p_hostname, 123);
- if (lsa) {
- free(p->p_lsa);
- free(p->p_dotted);
- p->p_lsa = lsa;
- p->p_dotted = xmalloc_sockaddr2dotted_noport(&lsa->u.sa);
- VERB1 if (strcmp(p->p_hostname, p->p_dotted) != 0)
- bb_error_msg("'%s' is %s", p->p_hostname, p->p_dotted);
- p->dns_errors = 0;
- return lsa;
- }
- p->dns_errors = ((p->dns_errors << 1) | 1) & DNS_ERRORS_CAP;
- return lsa;
- }
- static void
- add_peers(const char *s)
- {
- llist_t *item;
- peer_t *p;
- p = xzalloc(sizeof(*p) + strlen(s));
- strcpy(p->p_hostname, s);
- 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, STEP_THRESHOLD);
- /* Names like N.<country2chars>.pool.ntp.org are randomly resolved
- * to a pool of machines. Sometimes different N's resolve to the same IP.
- * It is not useful to have two peers with same IP. We skip duplicates.
- */
- if (resolve_peer_hostname(p)) {
- for (item = G.ntp_peers; item != NULL; item = item->link) {
- peer_t *pp = (peer_t *) item->data;
- if (pp->p_dotted && strcmp(p->p_dotted, pp->p_dotted) == 0) {
- bb_error_msg("duplicate peer %s (%s)", s, p->p_dotted);
- free(p->p_lsa);
- free(p->p_dotted);
- free(p);
- return;
- }
- }
- }
- 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)
- {
- if (!p->p_lsa)
- return;
- /* 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_int(fd, IPPROTO_IP, IP_TOS, IPTOS_DSCP_AF21);
- 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);
- //maybe? G.FREQHOLD_cnt = 0;
- /* 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;
- 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 */
- /* The ratio is calculated before jitter is updated to make
- * poll adjust code more sensitive to large offsets.
- */
- G.offset_to_jitter_ratio = abs_offset / G.discipline_jitter;
- /* 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);
- if (G.discipline_jitter < G_precision_sec)
- G.discipline_jitter = G_precision_sec;
- 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);
- }
- }
- 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 = (long)(offset * 1000000); /* usec */
- if (SLEW_THRESHOLD < STEP_THRESHOLD) {
- if (tmx.offset > (long)(SLEW_THRESHOLD * 1000000)) {
- tmx.offset = (long)(SLEW_THRESHOLD * 1000000);
- }
- if (tmx.offset < -(long)(SLEW_THRESHOLD * 1000000)) {
- tmx.offset = -(long)(SLEW_THRESHOLD * 1000000);
- }
- }
- tmx.status = STA_PLL;
- if (G.FREQHOLD_cnt != 0) {
- /* man adjtimex on STA_FREQHOLD:
- * "Normally adjustments made via ADJ_OFFSET result in dampened
- * frequency adjustments also being made.
- * This flag prevents the small frequency adjustment from being
- * made when correcting for an ADJ_OFFSET value."
- *
- * Use this flag for a few first adjustments at the beginning
- * of ntpd execution, otherwise even relatively small initial
- * offset tend to cause largish changes to in-kernel tmx.freq.
- * If ntpd was restarted due to e.g. switch to another network,
- * this destroys already well-established tmx.freq value.
- */
- if (G.FREQHOLD_cnt < 0) {
- /* Initialize it */
- // Example: a laptop whose clock runs slower when hibernated,
- // after wake up it still has good tmx.freq, but accumulated ~0.5 sec offset:
- // Run with code where initial G.FREQHOLD_cnt was always 8:
- //15:17:52.947 no valid datapoints, no peer selected
- //15:17:56.515 update from:<IP> offset:+0.485133 delay:0.157762 jitter:0.209310 clock drift:-1.393ppm tc:4
- //15:17:57.719 update from:<IP> offset:+0.483825 delay:0.158070 jitter:0.181159 clock drift:-1.393ppm tc:4
- //15:17:59.925 update from:<IP> offset:+0.479504 delay:0.158147 jitter:0.156657 clock drift:-1.393ppm tc:4
- //15:18:33.322 update from:<IP> offset:+0.428119 delay:0.158317 jitter:0.138071 clock drift:-1.393ppm tc:4
- //15:19:06.718 update from:<IP> offset:+0.376932 delay:0.158276 jitter:0.122075 clock drift:-1.393ppm tc:4
- //15:19:39.114 update from:<IP> offset:+0.327022 delay:0.158384 jitter:0.108538 clock drift:-1.393ppm tc:4
- //15:20:12.715 update from:<IP> offset:+0.275596 delay:0.158297 jitter:0.097292 clock drift:-1.393ppm tc:4
- //15:20:45.111 update from:<IP> offset:+0.225715 delay:0.158271 jitter:0.087841 clock drift:-1.393ppm tc:4
- // If allowed to continue, it would start increasing tmx.freq now.
- // Instead, it was ^Ced, and started anew:
- //15:21:15.043 no valid datapoints, no peer selected
- //15:21:17.408 update from:<IP> offset:+0.175910 delay:0.158314 jitter:0.076683 clock drift:-1.393ppm tc:4
- //15:21:19.774 update from:<IP> offset:+0.171784 delay:0.158401 jitter:0.066436 clock drift:-1.393ppm tc:4
- //15:21:22.140 update from:<IP> offset:+0.171660 delay:0.158592 jitter:0.057536 clock drift:-1.393ppm tc:4
- //15:21:22.140 update from:<IP> offset:+0.167126 delay:0.158507 jitter:0.049792 clock drift:-1.393ppm tc:4
- //15:21:55.696 update from:<IP> offset:+0.115223 delay:0.158277 jitter:0.050240 clock drift:-1.393ppm tc:4
- //15:22:29.093 update from:<IP> offset:+0.068051 delay:0.158243 jitter:0.049405 clock drift:-1.393ppm tc:5
- //15:23:02.490 update from:<IP> offset:+0.051632 delay:0.158215 jitter:0.043545 clock drift:-1.393ppm tc:5
- //15:23:34.726 update from:<IP> offset:+0.039984 delay:0.158157 jitter:0.038106 clock drift:-1.393ppm tc:5
- // STA_FREQHOLD no longer set, started increasing tmx.freq now:
- //15:24:06.961 update from:<IP> offset:+0.030968 delay:0.158190 jitter:0.033306 clock drift:+2.387ppm tc:5
- //15:24:40.357 update from:<IP> offset:+0.023648 delay:0.158211 jitter:0.029072 clock drift:+5.454ppm tc:5
- //15:25:13.774 update from:<IP> offset:+0.018068 delay:0.157660 jitter:0.025288 clock drift:+7.728ppm tc:5
- //15:26:19.173 update from:<IP> offset:+0.010057 delay:0.157969 jitter:0.022255 clock drift:+8.361ppm tc:6
- //15:27:26.602 update from:<IP> offset:+0.006737 delay:0.158103 jitter:0.019316 clock drift:+8.792ppm tc:6
- //15:28:33.030 update from:<IP> offset:+0.004513 delay:0.158294 jitter:0.016765 clock drift:+9.080ppm tc:6
- //15:29:40.617 update from:<IP> offset:+0.002787 delay:0.157745 jitter:0.014543 clock drift:+9.258ppm tc:6
- //15:30:47.045 update from:<IP> offset:+0.001324 delay:0.157709 jitter:0.012594 clock drift:+9.342ppm tc:6
- //15:31:53.473 update from:<IP> offset:+0.000007 delay:0.158142 jitter:0.010922 clock drift:+9.343ppm tc:6
- //15:32:58.902 update from:<IP> offset:-0.000728 delay:0.158222 jitter:0.009454 clock drift:+9.298ppm tc:6
- /*
- * This expression would choose MIN_FREQHOLD + 7 in the above example.
- */
- G.FREQHOLD_cnt = MIN_FREQHOLD + ((unsigned)(abs(tmx.offset)) >> 16);
- }
- G.FREQHOLD_cnt--;
- tmx.status |= STA_FREQHOLD;
- }
- if (G.ntp_status & LI_PLUSSEC)
- tmx.status |= STA_INS;
- if (G.ntp_status & LI_MINUSSEC)
- tmx.status |= STA_DEL;
- tmx.constant = (int)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 aggressive (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 (G.offset_to_jitter_ratio >= TIMECONST_HACK_GATE)
- tmx.constant--;
- if (tmx.constant < 0)
- tmx.constant = 0;
- //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 delay:%f jitter:%f clock drift:%+.3fppm tc:%d",
- p->p_dotted,
- offset,
- p->lastpkt_delay,
- 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 {
- VERB3 if (rc > 0)
- bb_error_msg("want smaller interval: offset/jitter = %u",
- G.offset_to_jitter_ratio);
- 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 SLEW_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;
- }
- /* Respond only to client and symmetric active packets */
- if ((msg.m_status & MODE_MASK) != MODE_CLIENT
- && (msg.m_status & MODE_MASK) != MODE_SYM_ACT
- ) {
- 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.discipline_jitter = G_precision_sec;
- 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 */
- G.FREQHOLD_cnt = -1;
- /* Parse options */
- peers = NULL;
- 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 */
- "\0"
- "dd:wn" /* -d: counter; -p: list; -w implies -n */
- IF_FEATURE_NTPD_SERVER(":Il") /* -I implies -l */
- , &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 ENABLE_FEATURE_NTPD_SERVER
- G_listen_fd = -1;
- if (opts & OPT_l) {
- G_listen_fd = create_and_bind_dgram_or_die(NULL, 123);
- if (G.if_name) {
- if (setsockopt_bindtodevice(G_listen_fd, G.if_name))
- xfunc_die();
- }
- socket_want_pktinfo(G_listen_fd);
- setsockopt_int(G_listen_fd, IPPROTO_IP, IP_TOS, IPTOS_DSCP_AF21);
- }
- #endif
- /* I hesitate to set -20 prio. -15 should be high enough for timekeeping */
- if (opts & OPT_N)
- setpriority(PRIO_PROCESS, 0, -15);
- if (!(opts & OPT_n)) {
- bb_daemonize_or_rexec(DAEMON_DEVNULL_STDIO, argv);
- logmode = LOGMODE_NONE;
- }
- 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 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.last_script_run + (11*60);
- if (nextaction < G.cur_time + 1)
- nextaction = G.cur_time + 1;
- 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;
- }
- 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);
- /* What if don't see it because it changed its IP? */
- if (p->reachable_bits == 0)
- resolve_peer_hostname(p);
- 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) {
- double ct;
- int dns_error;
- if (bb_got_signal)
- break; /* poll was interrupted by a signal */
- if (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 */
- }
- /* Resolve peer names to IPs, if not resolved yet.
- * We do it only when poll timed out:
- * this way, we almost never overlap DNS resolution with
- * "request-reply" packet round trip.
- */
- dns_error = 0;
- ct = G.cur_time;
- for (item = G.ntp_peers; item != NULL; item = item->link) {
- peer_t *p = (peer_t *) item->data;
- if (p->next_action_time <= ct && !p->p_lsa) {
- /* This can take up to ~10 sec per each DNS query */
- dns_error |= (!resolve_peer_hostname(p));
- }
- }
- if (!dns_error)
- goto check_unsync;
- /* Set next time for those which are still not resolved */
- gettime1900d(); /* sets G.cur_time (needed for set_next()) */
- for (item = G.ntp_peers; item != NULL; item = item->link) {
- peer_t *p = (peer_t *) item->data;
- if (p->next_action_time <= ct && !p->p_lsa) {
- set_next(p, HOSTNAME_INTERVAL * p->dns_errors);
- }
- }
- 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
|