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ndk-busybox/networking/ntpd.c
Denys Vlasenko 1bfc4b85a7 ntpd: print result of hostname resolution 
This is particularly useful if hostname resolution is triggered by
host non-reachability: I saw this in real-life, without the message
it is not at all obvious that IP that we use for a specific host
has changed.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2017-01-19 14:42:34 +01:00

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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"
//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"
//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_LOWDELAY definition */
#include <sys/resource.h> /* setpriority */
#include <sys/timex.h>
#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 == 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 */
#define HOSTNAME_INTERVAL 5 /* hostname lookup failed. Wait N secs for next try */
/* 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
/* 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
#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;
/* 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 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;
#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)
#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 agressive:
* 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);
} else {
/* error message is emitted by host2sockaddr() */
set_next(p, HOSTNAME_INTERVAL);
}
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) {
if (!resolve_peer_hostname(p))
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_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;
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.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 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 (G.offset_to_jitter_ratio >= TIMECONST_HACK_GATE)
tmx.constant--;
tmx.offset = (long)(offset * 1000000); /* usec */
if (SLEW_THRESHOLD < STEP_THRESHOLD) {
if (tmx.offset > (long)(SLEW_THRESHOLD * 1000000)) {
tmx.offset = (long)(SLEW_THRESHOLD * 1000000);
tmx.constant--;
}
if (tmx.offset < -(long)(SLEW_THRESHOLD * 1000000)) {
tmx.offset = -(long)(SLEW_THRESHOLD * 1000000);
tmx.constant--;
}
}
if (tmx.constant < 0)
tmx.constant = 0;
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.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 */
/* Parse options */
peers = NULL;
opt_complementary = "dd: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 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_LOWDELAY);
}
#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.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;
}
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) {
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
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