Changeset 3621 in MondoRescue for branches/3.3/mindi-busybox/networking/ntpd.c

Timestamp:

Dec 20, 2016, 4:07:32 PM (7 years ago)

Author:

Bruno Cornec

Message:

New 3?3 banch for incorporation of latest busybox 1.25. Changing minor version to handle potential incompatibilities.

Location:

branches/3.3

Files:

• . (copied) (copied from branches/3.2 )
• mindi-busybox/networking/ntpd.c (modified) (78 diffs)

branches/3.3/mindi-busybox/networking/ntpd.c

@@ -2 +2 @@
  * NTP client/server, based on OpenNTPD 3.9p1
  *
- * Author: Adam Tkac <vonsch@gmail.com>
+ * Busybox port author: Adam Tkac (C) 2009 <vonsch@gmail.com>
  *
- * Licensed under GPLv2, see file LICENSE in this source tree.
+ * 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, whuch carries the following
+ * 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.                                                           *
- *                                                                     *
+ * Copyright (c) University of Delaware 1992-2009
+ *
+ * Permission to use, copy, modify, and distribute this software and
+ * its documentation for any purpose with or without fee is hereby
+ * granted, provided that the above copyright notice appears in all
+ * copies and that both the copyright notice and this permission
+ * notice appear in supporting documentation, and that the name
+ * University of Delaware not be used in advertising or publicity
+ * pertaining to distribution of the software without specific,
+ * written prior permission. The University of Delaware makes no
+ * representations about the suitability this software for any
+ * purpose. It is provided "as is" without express or implied warranty.
  ***********************************************************************
  */
 
 //usage:#define ntpd_trivial_usage
-//usage:    "[-dnqNw"IF_FEATURE_NTPD_SERVER("l")"] [-S PROG] [-p PEER]..."
+//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"
@@ -38 +51 @@
 //usage:     "\n    -N  Run at high priority"
 //usage:     "\n    -w  Do not set time (only query peers), implies -n"
-//usage:    IF_FEATURE_NTPD_SERVER(
-//usage:     "\n    -l  Run as server on port 123"
-//usage:    )
 //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"
@@ -52 +74 @@
 # define IPTOS_LOWDELAY 0x10
 #endif
-#ifndef IP_PKTINFO
-# error "Sorry, your kernel has to support IP_PKTINFO"
-#endif
 
 
 /* Verbosity control (max level of -dddd options accepted).
- * max 5 is very talkative (and bloated). 2 is non-bloated,
+ * max 6 is very talkative (and bloated). 3 is non-bloated,
  * production level setting.
  */
-#define MAX_VERBOSE     2
+#define MAX_VERBOSE     3
 
 
@@ -91 +110 @@
  * 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 RETRY_INTERVAL  5       /* on error, retry in N secs */
-#define RESPONSE_INTERVAL 15    /* wait for reply up to N secs */
-#define INITIAL_SAMPLES 4       /* how many samples do we want for init */
-
-/* Clock discipline parameters and constants */
+#define INITIAL_SAMPLES    4    /* how many samples do we want for init */
+#define BAD_DELAY_GROWTH   4    /* drop packet if its delay grew by more than this */
+
+#define RETRY_INTERVAL    32    /* on send/recv error, retry in N secs (need to be power of 2) */
+#define NOREPLY_INTERVAL 512    /* sent, but got no reply: cap next query by this many seconds */
+#define RESPONSE_INTERVAL 16    /* wait for reply up to N secs */
 
 /* Step threshold (sec). std ntpd uses 0.128.
- * Using exact power of 2 (1/8) results in smaller code */
-#define STEP_THRESHOLD  0.125
-#define WATCH_THRESHOLD 128     /* stepout threshold (sec). std ntpd uses 900 (11 mins (!)) */
+ */
+#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_).
+/*
+ * 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         10      /* 2^10 sec ~= 17 min */
+#define BIGPOLL         9       /* 2^9 sec ~= 8.5 min */
 #define MAXPOLL         12      /* maximum poll interval (12: 1.1h, 17: 36.4h). std ntpd uses 17 */
-/* Actively lower poll when we see such big offsets.
- * With STEP_THRESHOLD = 0.125, it means we try to sync more aggressively
- * if offset increases over ~0.04 sec */
-#define POLLDOWN_OFFSET (STEP_THRESHOLD / 3)
+/*
+ * 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) */
@@ -228 +275 @@
     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): */
+    /* 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;
@@ -243 +293 @@
     /* last sent packet: */
     msg_t            p_xmt_msg;
+    char             p_hostname[1];
 } peer_t;
 
@@ -260 +311 @@
     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),
@@ -278 +330 @@
 #if ENABLE_FEATURE_NTPD_SERVER
     int      listen_fd;
+    char     *if_name;
 # define G_listen_fd (G.listen_fd)
 #else
@@ -329 +382 @@
 #define G_precision_sec  0.002
     uint8_t  stratum;
-    /* Bool. After set to 1, never goes back to 0: */
-    smallint initial_poll_complete;
 
 #define STATE_NSET      0       /* initial state, "nothing is set" */
 //#define STATE_FSET    1       /* frequency set from file */
-#define STATE_SPIK      2       /* spike detected */
+//#define STATE_SPIK    2       /* spike detected */
 //#define STATE_FREQ    3       /* initial frequency */
 #define STATE_SYNC      4       /* clock synchronized (normal operation) */
@@ -359 +410 @@
 #define G (*ptr_to_globals)
 
-static const int const_IPTOS_LOWDELAY = IPTOS_LOWDELAY;
-
 
 #define VERB1 if (MAX_VERBOSE && G.verbose)
@@ -367 +416 @@
 #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)
 
 
@@ -568 +618 @@
     sum = 0;
     for (i = 0; i < NUM_DATAPOINTS; i++) {
-        VERB4 {
+        VERB5 {
             bb_error_msg("datapoint[%d]: off:%f disp:%f(%f) age:%f%s",
                 i,
@@ -665 +715 @@
     p->filter_jitter = sum > G_precision_sec ? sum : G_precision_sec;
 
-    VERB3 bb_error_msg("filter offset:%+f disp:%f jitter:%f",
+    VERB4 bb_error_msg("filter offset:%+f disp:%f jitter:%f",
             p->filter_offset,
             p->filter_dispersion,
@@ -675 +725 @@
 {
     int i;
-    bool small_ofs = fabs(offset) < 16 * STEP_THRESHOLD;
+    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 datapoins per peer
+     * after step in order to start trusting them.
+     * In turn, this was making poll interval decrease even after
+     * step was done. (Poll interval decreases already before step
+     * in this scenario, because we see large offsets and end up with
+     * no good peer to select).
+     */
 
     for (i = 0; i < NUM_DATAPOINTS; i++) {
@@ -690 +752 @@
             p->filter_datapoint[i].d_recv_time  = G.cur_time;
             p->filter_datapoint[i].d_offset     = 0;
-            p->filter_datapoint[i].d_dispersion = MAXDISP;
+            /*p->filter_datapoint[i].d_dispersion = MAXDISP;*/
         }
     }
@@ -696 +758 @@
         p->lastpkt_recv_time += offset;
     } else {
-        p->reachable_bits = 0;
+        /*p->reachable_bits = 0;*/
         p->lastpkt_recv_time = G.cur_time;
     }
     filter_datapoints(p); /* recalc p->filter_xxx */
-    VERB5 bb_error_msg("%s->lastpkt_recv_time=%f", p->p_dotted, p->lastpkt_recv_time);
+    VERB6 bb_error_msg("%s->lastpkt_recv_time=%f", p->p_dotted, p->lastpkt_recv_time);
 }
 
 static void
-add_peers(char *s)
-{
+resolve_peer_hostname(peer_t *p, int loop_on_fail)
+{
+    len_and_sockaddr *lsa;
+
+ again:
+    lsa = host2sockaddr(p->p_hostname, 123);
+    if (!lsa) {
+        /* error message already emitted by host2sockaddr() */
+        if (!loop_on_fail)
+            return;
+//FIXME: do this to avoid infinite looping on typo in a hostname?
+//well... in which case, what is a good value for loop_on_fail?
+        //if (--loop_on_fail == 0)
+        //  xfunc_die();
+        sleep(5);
+        goto again;
+    }
+    free(p->p_lsa);
+    free(p->p_dotted);
+    p->p_lsa = lsa;
+    p->p_dotted = xmalloc_sockaddr2dotted_noport(&lsa->u.sa);
+}
+
+static void
+add_peers(const char *s)
+{
+    llist_t *item;
     peer_t *p;
 
-    p = xzalloc(sizeof(*p));
-    p->p_lsa = xhost2sockaddr(s, 123);
-    p->p_dotted = xmalloc_sockaddr2dotted_noport(&p->p_lsa->u.sa);
+    p = xzalloc(sizeof(*p) + strlen(s));
+    strcpy(p->p_hostname, s);
+    resolve_peer_hostname(p, /*loop_on_fail=*/ 1);
+
+    /* 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.
+     */
+    for (item = G.ntp_peers; item != NULL; item = item->link) {
+        peer_t *pp = (peer_t *) item->data;
+        if (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;
+        }
+    }
+
     p->p_fd = -1;
     p->p_xmt_msg.m_status = MODE_CLIENT | (NTP_VERSION << 3);
     p->next_action_time = G.cur_time; /* = set_next(p, 0); */
-    reset_peer_stats(p, 16 * STEP_THRESHOLD);
+    reset_peer_stats(p, STEP_THRESHOLD);
 
     llist_add_to(&G.ntp_peers, p);
@@ -778 +881 @@
         if (family == AF_INET)
 #endif
-            setsockopt(fd, IPPROTO_IP, IP_TOS, &const_IPTOS_LOWDELAY, sizeof(const_IPTOS_LOWDELAY));
+            setsockopt_int(fd, IPPROTO_IP, IP_TOS, IPTOS_LOWDELAY);
         free(local_lsa);
     }
@@ -801 +904 @@
      * Save the real transmit timestamp locally.
      */
-    p->p_xmt_msg.m_xmttime.int_partl = random();
-    p->p_xmt_msg.m_xmttime.fractionl = random();
+    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,
@@ -810 +921 @@
         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;
     }
 
-    p->reachable_bits <<= 1;
     set_next(p, RESPONSE_INTERVAL);
 }
@@ -820 +935 @@
 
 /* Note that there is no provision to prevent several run_scripts
- * to be done in quick succession. In fact, it happens rather often
+ * 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
@@ -830 +945 @@
     char *argv[3];
     char *env1, *env2, *env3, *env4;
+
+    G.last_script_run = G.cur_time;
 
     if (!G.script_name)
@@ -867 +984 @@
     free(env3);
     free(env4);
-
-    G.last_script_run = G.cur_time;
 }
 
@@ -888 +1003 @@
     VERB2 {
         tval = tvc.tv_sec;
-        strftime(buf, sizeof(buf), "%Y-%m-%d %H:%M:%S", localtime(&tval));
+        strftime_YYYYMMDDHHMMSS(buf, sizeof(buf), &tval);
         bb_error_msg("current time is %s.%06u", buf, (unsigned)tvc.tv_usec);
     }
     tval = tvn.tv_sec;
-    strftime(buf, sizeof(buf), "%Y-%m-%d %H:%M:%S", localtime(&tval));
+    strftime_YYYYMMDDHHMMSS(buf, sizeof(buf), &tval);
     bb_error_msg("setting time to %s.%06u (offset %+fs)", buf, (unsigned)tvn.tv_usec, offset);
 
@@ -921 +1036 @@
 }
 
+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;
+}
+
 
 /*
@@ -960 +1085 @@
     if ((p->reachable_bits & (p->reachable_bits-1)) == 0) {
         /* One or zero bits in reachable_bits */
-        VERB3 bb_error_msg("peer %s unfit for selection: unreachable", p->p_dotted);
+        VERB4 bb_error_msg("peer %s unfit for selection: unreachable", p->p_dotted);
         return 0;
     }
@@ -967 +1092 @@
      || p->lastpkt_stratum >= MAXSTRAT
     ) {
-        VERB3 bb_error_msg("peer %s unfit for selection: bad status/stratum", p->p_dotted);
+        VERB4 bb_error_msg("peer %s unfit for selection: bad status/stratum", p->p_dotted);
         return 0;
     }
@@ -973 +1098 @@
     /* rd is root_distance(p) */
     if (rd > MAXDIST + FREQ_TOLERANCE * (1 << G.poll_exp)) {
-        VERB3 bb_error_msg("peer %s unfit for selection: root distance too high", p->p_dotted);
+        VERB4 bb_error_msg("peer %s unfit for selection: root distance too high", p->p_dotted);
         return 0;
     }
@@ -1002 +1127 @@
     num_points = 0;
     item = G.ntp_peers;
-    if (G.initial_poll_complete) while (item != NULL) {
+    while (item != NULL) {
         double rd, offset;
 
@@ -1013 +1138 @@
         }
 
-        VERB4 bb_error_msg("interval: [%f %f %f] %s",
+        VERB5 bb_error_msg("interval: [%f %f %f] %s",
                 offset - rd,
                 offset,
@@ -1038 +1163 @@
     num_candidates = num_points / 3;
     if (num_candidates == 0) {
-        VERB3 bb_error_msg("no valid datapoints, no peer selected");
+        VERB3 bb_error_msg("no valid datapoints%s", ", no peer selected");
         return NULL;
     }
@@ -1096 +1221 @@
         num_falsetickers++;
         if (num_falsetickers * 2 >= num_candidates) {
-            VERB3 bb_error_msg("too many falsetickers:%d (candidates:%d), no peer selected",
-                    num_falsetickers, num_candidates);
+            VERB3 bb_error_msg("falsetickers:%d, candidates:%d%s",
+                    num_falsetickers, num_candidates,
+                    ", no peer selected");
             return NULL;
         }
     }
-    VERB3 bb_error_msg("selected interval: [%f, %f]; candidates:%d falsetickers:%d",
+    VERB4 bb_error_msg("selected interval: [%f, %f]; candidates:%d falsetickers:%d",
             low, high, num_candidates, num_falsetickers);
 
@@ -1119 +1245 @@
         /* x.opt_rd == root_distance(p); */
         survivor[num_survivors].metric = MAXDIST * p->lastpkt_stratum + point[i].opt_rd;
-        VERB4 bb_error_msg("survivor[%d] metric:%f peer:%s",
+        VERB5 bb_error_msg("survivor[%d] metric:%f peer:%s",
             num_survivors, survivor[num_survivors].metric, p->p_dotted);
         num_survivors++;
@@ -1129 +1255 @@
      */
     if (num_survivors < MIN_SELECTED) {
-        VERB3 bb_error_msg("num_survivors %d < %d, no peer selected",
-                num_survivors, MIN_SELECTED);
+        VERB3 bb_error_msg("survivors:%d%s",
+                num_survivors,
+                ", no peer selected");
         return NULL;
     }
@@ -1150 +1277 @@
 
         if (num_survivors <= MIN_CLUSTERED) {
-            VERB3 bb_error_msg("num_survivors %d <= %d, not discarding more",
+            VERB4 bb_error_msg("num_survivors %d <= %d, not discarding more",
                     num_survivors, MIN_CLUSTERED);
             break;
@@ -1176 +1303 @@
                 max_idx = i;
             }
-            VERB5 bb_error_msg("survivor %d selection_jitter^2:%f",
+            VERB6 bb_error_msg("survivor %d selection_jitter^2:%f",
                     i, selection_jitter_sq);
         }
         max_selection_jitter = SQRT(max_selection_jitter / num_survivors);
-        VERB4 bb_error_msg("max_selection_jitter (at %d):%f min_jitter:%f",
+        VERB5 bb_error_msg("max_selection_jitter (at %d):%f min_jitter:%f",
                 max_idx, max_selection_jitter, min_jitter);
 
@@ -1189 +1316 @@
          */
         if (max_selection_jitter < min_jitter) {
-            VERB3 bb_error_msg("max_selection_jitter:%f < min_jitter:%f, num_survivors:%d, not discarding more",
+            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;
@@ -1197 +1324 @@
          * and go around again.
          */
-        VERB5 bb_error_msg("dropping survivor %d", max_idx);
+        VERB6 bb_error_msg("dropping survivor %d", max_idx);
         num_survivors--;
         while (max_idx < num_survivors) {
@@ -1239 +1366 @@
         for (i = 1; i < num_survivors; i++) {
             if (G.last_update_peer == survivor[i].p) {
-                VERB4 bb_error_msg("keeping old synced peer");
+                VERB5 bb_error_msg("keeping old synced peer");
                 p = G.last_update_peer;
                 goto keep_old;
@@ -1247 +1374 @@
     G.last_update_peer = p;
  keep_old:
-    VERB3 bb_error_msg("selected peer %s filter_offset:%+f age:%f",
+    VERB4 bb_error_msg("selected peer %s filter_offset:%+f age:%f",
             p->p_dotted,
             p->filter_offset,
@@ -1266 +1393 @@
      * the current time.
      */
-    VERB3 bb_error_msg("disc_state=%d last update offset=%f recv_time=%f",
+    VERB4 bb_error_msg("disc_state=%d last update offset=%f recv_time=%f",
             disc_state, offset, recv_time);
     G.discipline_state = disc_state;
@@ -1285 +1412 @@
     double freq_drift;
 #endif
+#if !USING_KERNEL_PLL_LOOP || USING_INITIAL_FREQ_ESTIMATION
     double since_last_update;
+#endif
     double etemp, dtemp;
 
@@ -1304 +1433 @@
      */
     if (recv_time <= G.last_update_recv_time) {
-        VERB3 bb_error_msg("same or older datapoint: %f >= %f, not using it",
-                G.last_update_recv_time, 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" */
     }
@@ -1313 +1442 @@
      * 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;
@@ -1321 +1452 @@
         /* Ignore updates until the stepout threshold */
         if (since_last_update < WATCH_THRESHOLD) {
-            VERB3 bb_error_msg("measuring drift, datapoint ignored, %f sec remains",
+            VERB4 bb_error_msg("measuring drift, datapoint ignored, %f sec remains",
                     WATCH_THRESHOLD - since_last_update);
             return 0; /* "leave poll interval as is" */
@@ -1335 +1466 @@
      */
     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("offset:%+f - spike detected", offset);
+            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" */
@@ -1346 +1488 @@
              * is found or the stepout threshold is exceeded.
              */
-            if (since_last_update < WATCH_THRESHOLD) {
-                VERB3 bb_error_msg("spike detected, datapoint ignored, %f sec remains",
-                        WATCH_THRESHOLD - since_last_update);
+            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.
@@ -1375 +1520 @@
          * intervals.
          */
-        VERB3 bb_error_msg("stepping time by %+f; poll_exp=MINPOLL", offset);
+        VERB4 bb_error_msg("stepping time by %+f; poll_exp=MINPOLL", offset);
         step_time(offset);
         if (option_mask32 & OPT_q) {
@@ -1382 +1527 @@
         }
 
-        G.polladj_count = 0;
-        G.poll_exp = MINPOLL;
-        G.stratum = MAXSTRAT;
+        clamp_pollexp_and_set_MAXSTRAT();
 
         run_script("step", offset);
+
+        recv_time += offset;
 
 #if USING_INITIAL_FREQ_ESTIMATION
@@ -1396 +1541 @@
         abs_offset = offset = 0;
         set_new_values(STATE_SYNC, offset, recv_time);
-
     } else { /* abs_offset <= STEP_THRESHOLD */
 
-        if (G.poll_exp < MINPOLL && G.initial_poll_complete) {
-            VERB3 bb_error_msg("small offset:%+f, disabling burst mode", offset);
-            G.polladj_count = 0;
-            G.poll_exp = MINPOLL;
-        }
+        /* 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
@@ -1411 +1554 @@
         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) {
@@ -1429 +1574 @@
             set_new_values(STATE_SYNC, offset, recv_time);
 #endif
-            VERB3 bb_error_msg("transitioning to FREQ, datapoint ignored");
+            VERB4 bb_error_msg("transitioning to FREQ, datapoint ignored");
             return 0; /* "leave poll interval as is" */
 
@@ -1487 +1632 @@
     }
 
-    if (G.discipline_jitter < G_precision_sec)
-        G.discipline_jitter = G_precision_sec;
-    G.offset_to_jitter_ratio = abs_offset / G.discipline_jitter;
-
     G.reftime = G.cur_time;
     G.ntp_status = p->lastpkt_status;
@@ -1498 +1639 @@
     dtemp += MAXD(p->filter_dispersion + FREQ_TOLERANCE * (G.cur_time - p->lastpkt_recv_time) + abs_offset, MINDISP);
     G.rootdisp = p->lastpkt_rootdisp + dtemp;
-    VERB3 bb_error_msg("updating leap/refid/reftime/rootdisp from peer %s", p->p_dotted);
+    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.
@@ -1518 +1659 @@
     G.discipline_wander = SQRT(etemp + (dtemp - etemp) / AVG);
 
-    VERB3 bb_error_msg("discipline freq_drift=%.9f(int:%ld corr:%e) wander=%f",
+    VERB4 bb_error_msg("discipline freq_drift=%.9f(int:%ld corr:%e) wander=%f",
             G.discipline_freq_drift,
             (long)(G.discipline_freq_drift * 65536e6),
@@ -1524 +1665 @@
             G.discipline_wander);
 #endif
-    VERB3 {
+    VERB4 {
         memset(&tmx, 0, sizeof(tmx));
         if (adjtimex(&tmx) < 0)
@@ -1543 +1684 @@
 #endif
     tmx.modes = ADJ_OFFSET | ADJ_STATUS | ADJ_TIMECONST;// | ADJ_MAXERROR | ADJ_ESTERROR;
-    tmx.offset = (offset * 1000000); /* usec */
-    tmx.status = STA_PLL;
-    if (G.ntp_status & LI_PLUSSEC)
-        tmx.status |= STA_INS;
-    if (G.ntp_status & LI_MINUSSEC)
-        tmx.status |= STA_DEL;
-
-    tmx.constant = G.poll_exp - 4;
+    tmx.constant = (int)G.poll_exp - 4;
     /* EXPERIMENTAL.
      * The below if statement should be unnecessary, but...
@@ -1561 +1695 @@
      * larger than jitter.
      */
-    if (tmx.constant > 0 && G.offset_to_jitter_ratio >= TIMECONST_HACK_GATE)
+    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);
@@ -1572 +1725 @@
      * Not sure why. Perhaps it is normal.
      */
-    VERB3 bb_error_msg("adjtimex:%d freq:%ld offset:%+ld status:0x%x",
+    VERB4 bb_error_msg("adjtimex:%d freq:%ld offset:%+ld status:0x%x",
                 rc, tmx.freq, tmx.offset, tmx.status);
     G.kernel_freq_drift = tmx.freq / 65536;
-    VERB2 bb_error_msg("update from:%s offset:%+f jitter:%f clock drift:%+.3fppm tc:%d",
-            p->p_dotted, offset, G.discipline_jitter, (double)tmx.freq / 65536, (int)tmx.constant);
+    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" */
@@ -1587 +1746 @@
  */
 static unsigned
-retry_interval(void)
-{
-    /* Local problem, want to retry soon */
-    unsigned interval, r;
-    interval = RETRY_INTERVAL;
-    r = random();
-    interval += r % (unsigned)(RETRY_INTERVAL / 4);
-    VERB3 bb_error_msg("chose retry interval:%u", interval);
+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 unsigned
-poll_interval(int exponent)
-{
-    unsigned interval, r;
-    exponent = G.poll_exp + exponent;
-    if (exponent < 0)
-        exponent = 0;
-    interval = 1 << exponent;
-    r = random();
-    interval += ((r & (interval-1)) >> 4) + ((r >> 8) & 1); /* + 1/16 of interval, max */
-    VERB3 bb_error_msg("chose poll interval:%u (poll_exp:%d exp:%d)", interval, G.poll_exp, exponent);
-    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
@@ -1617 +1800 @@
     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 == -1) {
-        bb_perror_msg("recv(%s) error", p->p_dotted);
-        if (errno == EHOSTUNREACH || errno == EHOSTDOWN
-         || errno == ENETUNREACH || errno == ENETDOWN
-         || errno == ECONNREFUSED || errno == EADDRNOTAVAIL
-         || errno == EAGAIN
-        ) {
-//TODO: always do this?
-            interval = retry_interval();
-            goto set_next_and_ret;
-        }
-        xfunc_die();
+    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);
     }
 
@@ -1663 +1854 @@
      || msg.m_stratum > NTP_MAXSTRATUM
     ) {
-// TODO: 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
-        interval = poll_interval(0);
-        bb_error_msg("reply from %s: peer is unsynced, next query in %us", p->p_dotted, interval);
-        goto set_next_and_ret;
+        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;
     }
 
@@ -1674 +1869 @@
 //  if (msg.m_rootdelay / 2 + msg.m_rootdisp >= MAXDISP || p->lastpkt_reftime > msg.m_xmt)
 //      return;                 /* invalid header values */
-
-    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;
 
     /*
@@ -1700 +1889 @@
     T4 = G.cur_time;
 
-    p->lastpkt_recv_time = T4;
-
-    VERB5 bb_error_msg("%s->lastpkt_recv_time=%f", p->p_dotted, p->lastpkt_recv_time);
-    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    = ((T2 - T1) + (T3 - T4)) / 2;
     /* The delay calculation is a special case. In cases where the
      * server and client clocks are running at different rates and
@@ -1713 +1895 @@
      * the delay is clamped not less than the system precision.
      */
-    p->lastpkt_delay = (T4 - T1) - (T3 - T2);
-    if (p->lastpkt_delay < G_precision_sec)
-        p->lastpkt_delay = G_precision_sec;
+    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) {
@@ -1721 +1927 @@
         int i;
         for (i = 0; i < NUM_DATAPOINTS; i++) {
-            p->filter_datapoint[i].d_offset = datapoint->d_offset;
+            p->filter_datapoint[i].d_offset = offset;
         }
     }
@@ -1729 +1935 @@
         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,
-            datapoint->d_offset,
+            offset,
             p->lastpkt_delay,
             p->lastpkt_status,
@@ -1745 +1951 @@
     filter_datapoints(p);
     q = select_and_cluster();
-    rc = -1;
+    rc = 0;
     if (q) {
-        rc = 0;
         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) {
-                VERB3 bb_error_msg("offset:%+f > POLLDOWN_OFFSET", q->filter_offset);
-                goto poll_down;
+                VERB4 bb_error_msg("offset:%+f > POLLDOWN_OFFSET", q->filter_offset);
+                adjust_poll(-POLLADJ_LIMIT * 3);
+                rc = 0;
             }
-        }
-    }
-    /* else: no peer selected, rc = -1: we want to poll more often */
+#endif
+        }
+    } else {
+        /* No peer selected.
+         * If poll interval is small, increase it.
+         */
+        if (G.poll_exp < BIGPOLL)
+            goto increase_interval;
+    }
 
     if (rc != 0) {
@@ -1771 +1992 @@
             /* was += G.poll_exp but it is a bit
              * too optimistic for my taste at high poll_exp's */
-            G.polladj_count += MINPOLL;
-            if (G.polladj_count > POLLADJ_LIMIT) {
-                G.polladj_count = 0;
-                if (G.poll_exp < MAXPOLL) {
-                    G.poll_exp++;
-                    VERB3 bb_error_msg("polladj: discipline_jitter:%f ++poll_exp=%d",
-                            G.discipline_jitter, G.poll_exp);
-                }
-            } else {
-                VERB3 bb_error_msg("polladj: incr:%d", G.polladj_count);
-            }
+ increase_interval:
+            adjust_poll(MINPOLL);
         } else {
-            G.polladj_count -= G.poll_exp * 2;
-            if (G.polladj_count < -POLLADJ_LIMIT || G.poll_exp >= BIGPOLL) {
- poll_down:
-                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);
-                    }
-                    VERB3 bb_error_msg("polladj: discipline_jitter:%f --poll_exp=%d",
-                            G.discipline_jitter, G.poll_exp);
-                }
-            } else {
-                VERB3 bb_error_msg("polladj: decr:%d", G.polladj_count);
-            }
+            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 */
-    interval = poll_interval(0);
-
- set_next_and_ret:
+ 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);
 }
@@ -1844 +2049 @@
         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;
     }
@@ -1979 +2191 @@
     llist_t *peers;
 
-    srandom(getpid());
+    srand(getpid());
 
     if (getuid())
@@ -1985 +2197 @@
 
     /* Set some globals */
+    G.discipline_jitter = G_precision_sec;
     G.stratum = MAXSTRAT;
     if (BURSTPOLL != 0)
@@ -1992 +2205 @@
     /* Parse options */
     peers = NULL;
-    opt_complementary = "dd:p::wn"; /* d: counter; p: list; -w implies -n */
+    opt_complementary = "dd:p::wn"         /* -d: counter; -p: list; -w implies -n */
+        IF_FEATURE_NTPD_SERVER(":Il"); /* -I implies -l */
     opts = getopt32(argv,
             "nqNx" /* compat */
             "wp:S:"IF_FEATURE_NTPD_SERVER("l") /* NOT compat */
+            IF_FEATURE_NTPD_SERVER("I:") /* compat */
             "d" /* compat */
             "46aAbgL", /* compat, ignored */
-            &peers, &G.script_name, &G.verbose);
-    if (!(opts & (OPT_p|OPT_l)))
-        bb_show_usage();
+            &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;
@@ -2006 +2224 @@
         while (peers)
             add_peers(llist_pop(&peers));
-    } else {
+    }
+#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 (!(opts & OPT_n)) {
-        bb_daemonize_or_rexec(DAEMON_DEVNULL_STDIO, argv);
-        logmode = LOGMODE_NONE;
     }
 #if ENABLE_FEATURE_NTPD_SERVER
@@ -2018 +2253 @@
     if (opts & OPT_l) {
         G_listen_fd = create_and_bind_dgram_or_die(NULL, 123);
+        if (opts & OPT_I) {
+            if (setsockopt_bindtodevice(G_listen_fd, G.if_name))
+                xfunc_die();
+        }
         socket_want_pktinfo(G_listen_fd);
-        setsockopt(G_listen_fd, IPPROTO_IP, IP_TOS, &const_IPTOS_LOWDELAY, sizeof(const_IPTOS_LOWDELAY));
-    }
-#endif
+        setsockopt_int(G_listen_fd, IPPROTO_IP, IP_TOS, IPTOS_LOWDELAY);
+    }
+#endif
+    if (!(opts & OPT_n)) {
+        bb_daemonize_or_rexec(DAEMON_DEVNULL_STDIO, argv);
+        logmode = LOGMODE_NONE;
+    }
     /* I hesitate to set -20 prio. -15 should be high enough for timekeeping */
     if (opts & OPT_N)
@@ -2109 +2352 @@
                     /* Time to send new req */
                     if (--cnt == 0) {
-                        G.initial_poll_complete = 1;
+                        VERB4 bb_error_msg("disabling burst mode");
+                        G.polladj_count = 0;
+                        G.poll_exp = MINPOLL;
                     }
                     send_query_to_peer(p);
@@ -2116 +2361 @@
                     close(p->p_fd);
                     p->p_fd = -1;
-                    timeout = poll_interval(-2); /* -2: try a bit sooner */
+                    /* 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, /*loop_on_fail=*/ 0);
+
                     set_next(p, timeout);
                 }
@@ -2160 +2413 @@
         gettime1900d(); /* sets G.cur_time */
         if (nfds <= 0) {
-            if (G.script_name && G.cur_time - G.last_script_run > 11*60) {
+            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 */
             }
-            continue;
+            goto check_unsync;
         }
 
@@ -2195 +2450 @@
                 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) */