./tools/notsd-move

1 files changed, 1157 insertions, 0 deletions

diff --git a/src/systemd-timesyncd/timesyncd-manager.c b/src/systemd-timesyncd/timesyncd-manager.c
new file mode 100644
index 0000000000..687ef09ff3
--- /dev/null
+++ b/src/systemd-timesyncd/timesyncd-manager.c
@@ -0,0 +1,1157 @@
+/***
+  This file is part of systemd.
+
+  Copyright 2014 Kay Sievers, Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <errno.h>
+#include <math.h>
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <resolv.h>
+#include <stdlib.h>
+#include <sys/socket.h>
+#include <sys/timerfd.h>
+#include <sys/timex.h>
+#include <sys/types.h>
+#include <time.h>
+
+#include <systemd/sd-daemon.h>
+
+#include "sd-network/network-util.h"
+#include "systemd-basic/alloc-util.h"
+#include "systemd-basic/fd-util.h"
+#include "systemd-basic/fs-util.h"
+#include "systemd-basic/list.h"
+#include "systemd-basic/log.h"
+#include "systemd-basic/missing.h"
+#include "systemd-basic/ratelimit.h"
+#include "systemd-basic/socket-util.h"
+#include "systemd-basic/sparse-endian.h"
+#include "systemd-basic/string-util.h"
+#include "systemd-basic/strv.h"
+#include "systemd-basic/time-util.h"
+#include "systemd-basic/util.h"
+
+#include "timesyncd-conf.h"
+#include "timesyncd-manager.h"
+
+#ifndef ADJ_SETOFFSET
+#define ADJ_SETOFFSET                   0x0100  /* add 'time' to current time */
+#endif
+
+/* expected accuracy of time synchronization; used to adjust the poll interval */
+#define NTP_ACCURACY_SEC                0.2
+
+/*
+ * "A client MUST NOT under any conditions use a poll interval less
+ * than 15 seconds."
+ */
+#define NTP_POLL_INTERVAL_MIN_SEC       32
+#define NTP_POLL_INTERVAL_MAX_SEC       2048
+
+/*
+ * Maximum delta in seconds which the system clock is gradually adjusted
+ * (slew) to approach the network time. Deltas larger that this are set by
+ * letting the system time jump. The kernel's limit for adjtime is 0.5s.
+ */
+#define NTP_MAX_ADJUST                  0.4
+
+/* NTP protocol, packet header */
+#define NTP_LEAP_PLUSSEC                1
+#define NTP_LEAP_MINUSSEC               2
+#define NTP_LEAP_NOTINSYNC              3
+#define NTP_MODE_CLIENT                 3
+#define NTP_MODE_SERVER                 4
+#define NTP_FIELD_LEAP(f)               (((f) >> 6) & 3)
+#define NTP_FIELD_VERSION(f)            (((f) >> 3) & 7)
+#define NTP_FIELD_MODE(f)               ((f) & 7)
+#define NTP_FIELD(l, v, m)              (((l) << 6) | ((v) << 3) | (m))
+
+/* Maximum acceptable root distance in seconds. */
+#define NTP_MAX_ROOT_DISTANCE           5.0
+
+/* Maximum number of missed replies before selecting another source. */
+#define NTP_MAX_MISSED_REPLIES          2
+
+/*
+ * "NTP timestamps are represented as a 64-bit unsigned fixed-point number,
+ * in seconds relative to 0h on 1 January 1900."
+ */
+#define OFFSET_1900_1970        UINT64_C(2208988800)
+
+#define RETRY_USEC (30*USEC_PER_SEC)
+#define RATELIMIT_INTERVAL_USEC (10*USEC_PER_SEC)
+#define RATELIMIT_BURST 10
+
+#define TIMEOUT_USEC (10*USEC_PER_SEC)
+
+struct ntp_ts {
+        be32_t sec;
+        be32_t frac;
+} _packed_;
+
+struct ntp_ts_short {
+        be16_t sec;
+        be16_t frac;
+} _packed_;
+
+struct ntp_msg {
+        uint8_t field;
+        uint8_t stratum;
+        int8_t poll;
+        int8_t precision;
+        struct ntp_ts_short root_delay;
+        struct ntp_ts_short root_dispersion;
+        char refid[4];
+        struct ntp_ts reference_time;
+        struct ntp_ts origin_time;
+        struct ntp_ts recv_time;
+        struct ntp_ts trans_time;
+} _packed_;
+
+static int manager_arm_timer(Manager *m, usec_t next);
+static int manager_clock_watch_setup(Manager *m);
+static int manager_listen_setup(Manager *m);
+static void manager_listen_stop(Manager *m);
+
+static double ntp_ts_short_to_d(const struct ntp_ts_short *ts) {
+        return be16toh(ts->sec) + (be16toh(ts->frac) / 65536.0);
+}
+
+static double ntp_ts_to_d(const struct ntp_ts *ts) {
+        return be32toh(ts->sec) + ((double)be32toh(ts->frac) / UINT_MAX);
+}
+
+static double ts_to_d(const struct timespec *ts) {
+        return ts->tv_sec + (1.0e-9 * ts->tv_nsec);
+}
+
+static int manager_timeout(sd_event_source *source, usec_t usec, void *userdata) {
+        _cleanup_free_ char *pretty = NULL;
+        Manager *m = userdata;
+
+        assert(m);
+        assert(m->current_server_name);
+        assert(m->current_server_address);
+
+        server_address_pretty(m->current_server_address, &pretty);
+        log_info("Timed out waiting for reply from %s (%s).", strna(pretty), m->current_server_name->string);
+
+        return manager_connect(m);
+}
+
+static int manager_send_request(Manager *m) {
+        _cleanup_free_ char *pretty = NULL;
+        struct ntp_msg ntpmsg = {
+                /*
+                 * "The client initializes the NTP message header, sends the request
+                 * to the server, and strips the time of day from the Transmit
+                 * Timestamp field of the reply.  For this purpose, all the NTP
+                 * header fields are set to 0, except the Mode, VN, and optional
+                 * Transmit Timestamp fields."
+                 */
+                .field = NTP_FIELD(0, 4, NTP_MODE_CLIENT),
+        };
+        ssize_t len;
+        int r;
+
+        assert(m);
+        assert(m->current_server_name);
+        assert(m->current_server_address);
+
+        m->event_timeout = sd_event_source_unref(m->event_timeout);
+
+        r = manager_listen_setup(m);
+        if (r < 0)
+                return log_warning_errno(r, "Failed to setup connection socket: %m");
+
+        /*
+         * Set transmit timestamp, remember it; the server will send that back
+         * as the origin timestamp and we have an indication that this is the
+         * matching answer to our request.
+         *
+         * The actual value does not matter, We do not care about the correct
+         * NTP UINT_MAX fraction; we just pass the plain nanosecond value.
+         */
+        assert_se(clock_gettime(clock_boottime_or_monotonic(), &m->trans_time_mon) >= 0);
+        assert_se(clock_gettime(CLOCK_REALTIME, &m->trans_time) >= 0);
+        ntpmsg.trans_time.sec = htobe32(m->trans_time.tv_sec + OFFSET_1900_1970);
+        ntpmsg.trans_time.frac = htobe32(m->trans_time.tv_nsec);
+
+        server_address_pretty(m->current_server_address, &pretty);
+
+        len = sendto(m->server_socket, &ntpmsg, sizeof(ntpmsg), MSG_DONTWAIT, &m->current_server_address->sockaddr.sa, m->current_server_address->socklen);
+        if (len == sizeof(ntpmsg)) {
+                m->pending = true;
+                log_debug("Sent NTP request to %s (%s).", strna(pretty), m->current_server_name->string);
+        } else {
+                log_debug_errno(errno, "Sending NTP request to %s (%s) failed: %m", strna(pretty), m->current_server_name->string);
+                return manager_connect(m);
+        }
+
+        /* re-arm timer with increasing timeout, in case the packets never arrive back */
+        if (m->retry_interval > 0) {
+                if (m->retry_interval < NTP_POLL_INTERVAL_MAX_SEC * USEC_PER_SEC)
+                        m->retry_interval *= 2;
+        } else
+                m->retry_interval = NTP_POLL_INTERVAL_MIN_SEC * USEC_PER_SEC;
+
+        r = manager_arm_timer(m, m->retry_interval);
+        if (r < 0)
+                return log_error_errno(r, "Failed to rearm timer: %m");
+
+        m->missed_replies++;
+        if (m->missed_replies > NTP_MAX_MISSED_REPLIES) {
+                r = sd_event_add_time(
+                                m->event,
+                                &m->event_timeout,
+                                clock_boottime_or_monotonic(),
+                                now(clock_boottime_or_monotonic()) + TIMEOUT_USEC, 0,
+                                manager_timeout, m);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to arm timeout timer: %m");
+        }
+
+        return 0;
+}
+
+static int manager_timer(sd_event_source *source, usec_t usec, void *userdata) {
+        Manager *m = userdata;
+
+        assert(m);
+
+        return manager_send_request(m);
+}
+
+static int manager_arm_timer(Manager *m, usec_t next) {
+        int r;
+
+        assert(m);
+
+        if (next == 0) {
+                m->event_timer = sd_event_source_unref(m->event_timer);
+                return 0;
+        }
+
+        if (m->event_timer) {
+                r = sd_event_source_set_time(m->event_timer, now(clock_boottime_or_monotonic()) + next);
+                if (r < 0)
+                        return r;
+
+                return sd_event_source_set_enabled(m->event_timer, SD_EVENT_ONESHOT);
+        }
+
+        return sd_event_add_time(
+                        m->event,
+                        &m->event_timer,
+                        clock_boottime_or_monotonic(),
+                        now(clock_boottime_or_monotonic()) + next, 0,
+                        manager_timer, m);
+}
+
+static int manager_clock_watch(sd_event_source *source, int fd, uint32_t revents, void *userdata) {
+        Manager *m = userdata;
+
+        assert(m);
+
+        /* rearm timer */
+        manager_clock_watch_setup(m);
+
+        /* skip our own jumps */
+        if (m->jumped) {
+                m->jumped = false;
+                return 0;
+        }
+
+        /* resync */
+        log_debug("System time changed. Resyncing.");
+        m->poll_resync = true;
+
+        return manager_send_request(m);
+}
+
+/* wake up when the system time changes underneath us */
+static int manager_clock_watch_setup(Manager *m) {
+
+        struct itimerspec its = {
+                .it_value.tv_sec = TIME_T_MAX
+        };
+
+        int r;
+
+        assert(m);
+
+        m->event_clock_watch = sd_event_source_unref(m->event_clock_watch);
+        safe_close(m->clock_watch_fd);
+
+        m->clock_watch_fd = timerfd_create(CLOCK_REALTIME, TFD_NONBLOCK|TFD_CLOEXEC);
+        if (m->clock_watch_fd < 0)
+                return log_error_errno(errno, "Failed to create timerfd: %m");
+
+        if (timerfd_settime(m->clock_watch_fd, TFD_TIMER_ABSTIME|TFD_TIMER_CANCEL_ON_SET, &its, NULL) < 0)
+                return log_error_errno(errno, "Failed to set up timerfd: %m");
+
+        r = sd_event_add_io(m->event, &m->event_clock_watch, m->clock_watch_fd, EPOLLIN, manager_clock_watch, m);
+        if (r < 0)
+                return log_error_errno(r, "Failed to create clock watch event source: %m");
+
+        return 0;
+}
+
+static int manager_adjust_clock(Manager *m, double offset, int leap_sec) {
+        struct timex tmx = {};
+        int r;
+
+        assert(m);
+
+        /*
+         * For small deltas, tell the kernel to gradually adjust the system
+         * clock to the NTP time, larger deltas are just directly set.
+         */
+        if (fabs(offset) < NTP_MAX_ADJUST) {
+                tmx.modes = ADJ_STATUS | ADJ_NANO | ADJ_OFFSET | ADJ_TIMECONST | ADJ_MAXERROR | ADJ_ESTERROR;
+                tmx.status = STA_PLL;
+                tmx.offset = offset * NSEC_PER_SEC;
+                tmx.constant = log2i(m->poll_interval_usec / USEC_PER_SEC) - 4;
+                tmx.maxerror = 0;
+                tmx.esterror = 0;
+                log_debug("  adjust (slew): %+.3f sec", offset);
+        } else {
+                tmx.modes = ADJ_STATUS | ADJ_NANO | ADJ_SETOFFSET;
+
+                /* ADJ_NANO uses nanoseconds in the microseconds field */
+                tmx.time.tv_sec = (long)offset;
+                tmx.time.tv_usec = (offset - tmx.time.tv_sec) * NSEC_PER_SEC;
+
+                /* the kernel expects -0.3s as {-1, 7000.000.000} */
+                if (tmx.time.tv_usec < 0) {
+                        tmx.time.tv_sec  -= 1;
+                        tmx.time.tv_usec += NSEC_PER_SEC;
+                }
+
+                m->jumped = true;
+                log_debug("  adjust (jump): %+.3f sec", offset);
+        }
+
+        /*
+         * An unset STA_UNSYNC will enable the kernel's 11-minute mode,
+         * which syncs the system time periodically to the RTC.
+         *
+         * In case the RTC runs in local time, never touch the RTC,
+         * we have no way to properly handle daylight saving changes and
+         * mobile devices moving between time zones.
+         */
+        if (m->rtc_local_time)
+                tmx.status |= STA_UNSYNC;
+
+        switch (leap_sec) {
+        case 1:
+                tmx.status |= STA_INS;
+                break;
+        case -1:
+                tmx.status |= STA_DEL;
+                break;
+        }
+
+        r = clock_adjtime(CLOCK_REALTIME, &tmx);
+        if (r < 0)
+                return -errno;
+
+        /* If touch fails, there isn't much we can do. Maybe it'll work next time. */
+        (void) touch("/var/lib/systemd/clock");
+
+        m->drift_ppm = tmx.freq / 65536;
+
+        log_debug("  status       : %04i %s\n"
+                  "  time now     : %li.%03llu\n"
+                  "  constant     : %li\n"
+                  "  offset       : %+.3f sec\n"
+                  "  freq offset  : %+li (%i ppm)\n",
+                  tmx.status, tmx.status & STA_UNSYNC ? "unsync" : "sync",
+                  tmx.time.tv_sec, (unsigned long long) (tmx.time.tv_usec / NSEC_PER_MSEC),
+                  tmx.constant,
+                  (double)tmx.offset / NSEC_PER_SEC,
+                  tmx.freq, m->drift_ppm);
+
+        return 0;
+}
+
+static bool manager_sample_spike_detection(Manager *m, double offset, double delay) {
+        unsigned int i, idx_cur, idx_new, idx_min;
+        double jitter;
+        double j;
+
+        assert(m);
+
+        m->packet_count++;
+
+        /* ignore initial sample */
+        if (m->packet_count == 1)
+                return false;
+
+        /* store the current data in our samples array */
+        idx_cur = m->samples_idx;
+        idx_new = (idx_cur + 1) % ELEMENTSOF(m->samples);
+        m->samples_idx = idx_new;
+        m->samples[idx_new].offset = offset;
+        m->samples[idx_new].delay = delay;
+
+        /* calculate new jitter value from the RMS differences relative to the lowest delay sample */
+        jitter = m->samples_jitter;
+        for (idx_min = idx_cur, i = 0; i < ELEMENTSOF(m->samples); i++)
+                if (m->samples[i].delay > 0 && m->samples[i].delay < m->samples[idx_min].delay)
+                        idx_min = i;
+
+        j = 0;
+        for (i = 0; i < ELEMENTSOF(m->samples); i++)
+                j += pow(m->samples[i].offset - m->samples[idx_min].offset, 2);
+        m->samples_jitter = sqrt(j / (ELEMENTSOF(m->samples) - 1));
+
+        /* ignore samples when resyncing */
+        if (m->poll_resync)
+                return false;
+
+        /* always accept offset if we are farther off than the round-trip delay */
+        if (fabs(offset) > delay)
+                return false;
+
+        /* we need a few samples before looking at them */
+        if (m->packet_count < 4)
+                return false;
+
+        /* do not accept anything worse than the maximum possible error of the best sample */
+        if (fabs(offset) > m->samples[idx_min].delay)
+                return true;
+
+        /* compare the difference between the current offset to the previous offset and jitter */
+        return fabs(offset - m->samples[idx_cur].offset) > 3 * jitter;
+}
+
+static void manager_adjust_poll(Manager *m, double offset, bool spike) {
+        assert(m);
+
+        if (m->poll_resync) {
+                m->poll_interval_usec = NTP_POLL_INTERVAL_MIN_SEC * USEC_PER_SEC;
+                m->poll_resync = false;
+                return;
+        }
+
+        /* set to minimal poll interval */
+        if (!spike && fabs(offset) > NTP_ACCURACY_SEC) {
+                m->poll_interval_usec = NTP_POLL_INTERVAL_MIN_SEC * USEC_PER_SEC;
+                return;
+        }
+
+        /* increase polling interval */
+        if (fabs(offset) < NTP_ACCURACY_SEC * 0.25) {
+                if (m->poll_interval_usec < NTP_POLL_INTERVAL_MAX_SEC * USEC_PER_SEC)
+                        m->poll_interval_usec *= 2;
+                return;
+        }
+
+        /* decrease polling interval */
+        if (spike || fabs(offset) > NTP_ACCURACY_SEC * 0.75) {
+                if (m->poll_interval_usec > NTP_POLL_INTERVAL_MIN_SEC * USEC_PER_SEC)
+                        m->poll_interval_usec /= 2;
+                return;
+        }
+}
+
+static int manager_receive_response(sd_event_source *source, int fd, uint32_t revents, void *userdata) {
+        Manager *m = userdata;
+        struct ntp_msg ntpmsg;
+
+        struct iovec iov = {
+                .iov_base = &ntpmsg,
+                .iov_len = sizeof(ntpmsg),
+        };
+        union {
+                struct cmsghdr cmsghdr;
+                uint8_t buf[CMSG_SPACE(sizeof(struct timeval))];
+        } control;
+        union sockaddr_union server_addr;
+        struct msghdr msghdr = {
+                .msg_iov = &iov,
+                .msg_iovlen = 1,
+                .msg_control = &control,
+                .msg_controllen = sizeof(control),
+                .msg_name = &server_addr,
+                .msg_namelen = sizeof(server_addr),
+        };
+        struct cmsghdr *cmsg;
+        struct timespec *recv_time;
+        ssize_t len;
+        double origin, receive, trans, dest;
+        double delay, offset;
+        double root_distance;
+        bool spike;
+        int leap_sec;
+        int r;
+
+        assert(source);
+        assert(m);
+
+        if (revents & (EPOLLHUP|EPOLLERR)) {
+                log_warning("Server connection returned error.");
+                return manager_connect(m);
+        }
+
+        len = recvmsg(fd, &msghdr, MSG_DONTWAIT);
+        if (len < 0) {
+                if (errno == EAGAIN)
+                        return 0;
+
+                log_warning("Error receiving message. Disconnecting.");
+                return manager_connect(m);
+        }
+
+        /* Too short or too long packet? */
+        if (iov.iov_len < sizeof(struct ntp_msg) || (msghdr.msg_flags & MSG_TRUNC)) {
+                log_warning("Invalid response from server. Disconnecting.");
+                return manager_connect(m);
+        }
+
+        if (!m->current_server_name ||
+            !m->current_server_address ||
+            !sockaddr_equal(&server_addr, &m->current_server_address->sockaddr)) {
+                log_debug("Response from unknown server.");
+                return 0;
+        }
+
+        recv_time = NULL;
+        CMSG_FOREACH(cmsg, &msghdr) {
+                if (cmsg->cmsg_level != SOL_SOCKET)
+                        continue;
+
+                switch (cmsg->cmsg_type) {
+                case SCM_TIMESTAMPNS:
+                        recv_time = (struct timespec *) CMSG_DATA(cmsg);
+                        break;
+                }
+        }
+        if (!recv_time) {
+                log_error("Invalid packet timestamp.");
+                return -EINVAL;
+        }
+
+        if (!m->pending) {
+                log_debug("Unexpected reply. Ignoring.");
+                return 0;
+        }
+
+        m->missed_replies = 0;
+
+        /* check our "time cookie" (we just stored nanoseconds in the fraction field) */
+        if (be32toh(ntpmsg.origin_time.sec) != m->trans_time.tv_sec + OFFSET_1900_1970 ||
+            be32toh(ntpmsg.origin_time.frac) != m->trans_time.tv_nsec) {
+                log_debug("Invalid reply; not our transmit time. Ignoring.");
+                return 0;
+        }
+
+        m->event_timeout = sd_event_source_unref(m->event_timeout);
+
+        if (be32toh(ntpmsg.recv_time.sec) < TIME_EPOCH + OFFSET_1900_1970 ||
+            be32toh(ntpmsg.trans_time.sec) < TIME_EPOCH + OFFSET_1900_1970) {
+                log_debug("Invalid reply, returned times before epoch. Ignoring.");
+                return manager_connect(m);
+        }
+
+        if (NTP_FIELD_LEAP(ntpmsg.field) == NTP_LEAP_NOTINSYNC ||
+            ntpmsg.stratum == 0 || ntpmsg.stratum >= 16) {
+                log_debug("Server is not synchronized. Disconnecting.");
+                return manager_connect(m);
+        }
+
+        if (!IN_SET(NTP_FIELD_VERSION(ntpmsg.field), 3, 4)) {
+                log_debug("Response NTPv%d. Disconnecting.", NTP_FIELD_VERSION(ntpmsg.field));
+                return manager_connect(m);
+        }
+
+        if (NTP_FIELD_MODE(ntpmsg.field) != NTP_MODE_SERVER) {
+                log_debug("Unsupported mode %d. Disconnecting.", NTP_FIELD_MODE(ntpmsg.field));
+                return manager_connect(m);
+        }
+
+        root_distance = ntp_ts_short_to_d(&ntpmsg.root_delay) / 2 + ntp_ts_short_to_d(&ntpmsg.root_dispersion);
+        if (root_distance > NTP_MAX_ROOT_DISTANCE) {
+                log_debug("Server has too large root distance. Disconnecting.");
+                return manager_connect(m);
+        }
+
+        /* valid packet */
+        m->pending = false;
+        m->retry_interval = 0;
+
+        /* Stop listening */
+        manager_listen_stop(m);
+
+        /* announce leap seconds */
+        if (NTP_FIELD_LEAP(ntpmsg.field) & NTP_LEAP_PLUSSEC)
+                leap_sec = 1;
+        else if (NTP_FIELD_LEAP(ntpmsg.field) & NTP_LEAP_MINUSSEC)
+                leap_sec = -1;
+        else
+                leap_sec = 0;
+
+        /*
+         * "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 round-trip delay, d, and system clock offset, t, are defined as:
+         *  d = (T4 - T1) - (T3 - T2)     t = ((T2 - T1) + (T3 - T4)) / 2"
+         */
+        origin = ts_to_d(&m->trans_time) + OFFSET_1900_1970;
+        receive = ntp_ts_to_d(&ntpmsg.recv_time);
+        trans = ntp_ts_to_d(&ntpmsg.trans_time);
+        dest = ts_to_d(recv_time) + OFFSET_1900_1970;
+
+        offset = ((receive - origin) + (trans - dest)) / 2;
+        delay = (dest - origin) - (trans - receive);
+
+        spike = manager_sample_spike_detection(m, offset, delay);
+
+        manager_adjust_poll(m, offset, spike);
+
+        log_debug("NTP response:\n"
+                  "  leap         : %u\n"
+                  "  version      : %u\n"
+                  "  mode         : %u\n"
+                  "  stratum      : %u\n"
+                  "  precision    : %.6f sec (%d)\n"
+                  "  root distance: %.6f sec\n"
+                  "  reference    : %.4s\n"
+                  "  origin       : %.3f\n"
+                  "  receive      : %.3f\n"
+                  "  transmit     : %.3f\n"
+                  "  dest         : %.3f\n"
+                  "  offset       : %+.3f sec\n"
+                  "  delay        : %+.3f sec\n"
+                  "  packet count : %"PRIu64"\n"
+                  "  jitter       : %.3f%s\n"
+                  "  poll interval: " USEC_FMT "\n",
+                  NTP_FIELD_LEAP(ntpmsg.field),
+                  NTP_FIELD_VERSION(ntpmsg.field),
+                  NTP_FIELD_MODE(ntpmsg.field),
+                  ntpmsg.stratum,
+                  exp2(ntpmsg.precision), ntpmsg.precision,
+                  root_distance,
+                  ntpmsg.stratum == 1 ? ntpmsg.refid : "n/a",
+                  origin - OFFSET_1900_1970,
+                  receive - OFFSET_1900_1970,
+                  trans - OFFSET_1900_1970,
+                  dest - OFFSET_1900_1970,
+                  offset, delay,
+                  m->packet_count,
+                  m->samples_jitter, spike ? " spike" : "",
+                  m->poll_interval_usec / USEC_PER_SEC);
+
+        if (!spike) {
+                m->sync = true;
+                r = manager_adjust_clock(m, offset, leap_sec);
+                if (r < 0)
+                        log_error_errno(r, "Failed to call clock_adjtime(): %m");
+        }
+
+        log_debug("interval/delta/delay/jitter/drift " USEC_FMT "s/%+.3fs/%.3fs/%.3fs/%+ippm%s",
+                  m->poll_interval_usec / USEC_PER_SEC, offset, delay, m->samples_jitter, m->drift_ppm,
+                  spike ? " (ignored)" : "");
+
+        if (!m->good) {
+                _cleanup_free_ char *pretty = NULL;
+
+                m->good = true;
+
+                server_address_pretty(m->current_server_address, &pretty);
+                log_info("Synchronized to time server %s (%s).", strna(pretty), m->current_server_name->string);
+                sd_notifyf(false, "STATUS=Synchronized to time server %s (%s).", strna(pretty), m->current_server_name->string);
+        }
+
+        r = manager_arm_timer(m, m->poll_interval_usec);
+        if (r < 0)
+                return log_error_errno(r, "Failed to rearm timer: %m");
+
+        return 0;
+}
+
+static int manager_listen_setup(Manager *m) {
+        union sockaddr_union addr = {};
+        static const int tos = IPTOS_LOWDELAY;
+        static const int on = 1;
+        int r;
+
+        assert(m);
+
+        if (m->server_socket >= 0)
+                return 0;
+
+        assert(!m->event_receive);
+        assert(m->current_server_address);
+
+        addr.sa.sa_family = m->current_server_address->sockaddr.sa.sa_family;
+
+        m->server_socket = socket(addr.sa.sa_family, SOCK_DGRAM | SOCK_CLOEXEC, 0);
+        if (m->server_socket < 0)
+                return -errno;
+
+        r = bind(m->server_socket, &addr.sa, m->current_server_address->socklen);
+        if (r < 0)
+                return -errno;
+
+        r = setsockopt(m->server_socket, SOL_SOCKET, SO_TIMESTAMPNS, &on, sizeof(on));
+        if (r < 0)
+                return -errno;
+
+        (void) setsockopt(m->server_socket, IPPROTO_IP, IP_TOS, &tos, sizeof(tos));
+
+        return sd_event_add_io(m->event, &m->event_receive, m->server_socket, EPOLLIN, manager_receive_response, m);
+}
+
+static void manager_listen_stop(Manager *m) {
+        assert(m);
+
+        m->event_receive = sd_event_source_unref(m->event_receive);
+        m->server_socket = safe_close(m->server_socket);
+}
+
+static int manager_begin(Manager *m) {
+        _cleanup_free_ char *pretty = NULL;
+        int r;
+
+        assert(m);
+        assert_return(m->current_server_name, -EHOSTUNREACH);
+        assert_return(m->current_server_address, -EHOSTUNREACH);
+
+        m->good = false;
+        m->missed_replies = NTP_MAX_MISSED_REPLIES;
+        if (m->poll_interval_usec == 0)
+                m->poll_interval_usec = NTP_POLL_INTERVAL_MIN_SEC * USEC_PER_SEC;
+
+        server_address_pretty(m->current_server_address, &pretty);
+        log_debug("Connecting to time server %s (%s).", strna(pretty), m->current_server_name->string);
+        sd_notifyf(false, "STATUS=Connecting to time server %s (%s).", strna(pretty), m->current_server_name->string);
+
+        r = manager_clock_watch_setup(m);
+        if (r < 0)
+                return r;
+
+        return manager_send_request(m);
+}
+
+void manager_set_server_name(Manager *m, ServerName *n) {
+        assert(m);
+
+        if (m->current_server_name == n)
+                return;
+
+        m->current_server_name = n;
+        m->current_server_address = NULL;
+
+        manager_disconnect(m);
+
+        if (n)
+                log_debug("Selected server %s.", n->string);
+}
+
+void manager_set_server_address(Manager *m, ServerAddress *a) {
+        assert(m);
+
+        if (m->current_server_address == a)
+                return;
+
+        m->current_server_address = a;
+        /* If a is NULL, we are just clearing the address, without
+         * changing the name. Keep the existing name in that case. */
+        if (a)
+                m->current_server_name = a->name;
+
+        manager_disconnect(m);
+
+        if (a) {
+                _cleanup_free_ char *pretty = NULL;
+                server_address_pretty(a, &pretty);
+                log_debug("Selected address %s of server %s.", strna(pretty), a->name->string);
+        }
+}
+
+static int manager_resolve_handler(sd_resolve_query *q, int ret, const struct addrinfo *ai, void *userdata) {
+        Manager *m = userdata;
+        int r;
+
+        assert(q);
+        assert(m);
+        assert(m->current_server_name);
+
+        m->resolve_query = sd_resolve_query_unref(m->resolve_query);
+
+        if (ret != 0) {
+                log_debug("Failed to resolve %s: %s", m->current_server_name->string, gai_strerror(ret));
+
+                /* Try next host */
+                return manager_connect(m);
+        }
+
+        for (; ai; ai = ai->ai_next) {
+                _cleanup_free_ char *pretty = NULL;
+                ServerAddress *a;
+
+                assert(ai->ai_addr);
+                assert(ai->ai_addrlen >= offsetof(struct sockaddr, sa_data));
+
+                if (!IN_SET(ai->ai_addr->sa_family, AF_INET, AF_INET6)) {
+                        log_warning("Unsuitable address protocol for %s", m->current_server_name->string);
+                        continue;
+                }
+
+                r = server_address_new(m->current_server_name, &a, (const union sockaddr_union*) ai->ai_addr, ai->ai_addrlen);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to add server address: %m");
+
+                server_address_pretty(a, &pretty);
+                log_debug("Resolved address %s for %s.", pretty, m->current_server_name->string);
+        }
+
+        if (!m->current_server_name->addresses) {
+                log_error("Failed to find suitable address for host %s.", m->current_server_name->string);
+
+                /* Try next host */
+                return manager_connect(m);
+        }
+
+        manager_set_server_address(m, m->current_server_name->addresses);
+
+        return manager_begin(m);
+}
+
+static int manager_retry_connect(sd_event_source *source, usec_t usec, void *userdata) {
+        Manager *m = userdata;
+
+        assert(m);
+
+        return manager_connect(m);
+}
+
+int manager_connect(Manager *m) {
+        int r;
+
+        assert(m);
+
+        manager_disconnect(m);
+
+        m->event_retry = sd_event_source_unref(m->event_retry);
+        if (!ratelimit_test(&m->ratelimit)) {
+                log_debug("Slowing down attempts to contact servers.");
+
+                r = sd_event_add_time(m->event, &m->event_retry, clock_boottime_or_monotonic(), now(clock_boottime_or_monotonic()) + RETRY_USEC, 0, manager_retry_connect, m);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to create retry timer: %m");
+
+                return 0;
+        }
+
+        /* If we already are operating on some address, switch to the
+         * next one. */
+        if (m->current_server_address && m->current_server_address->addresses_next)
+                manager_set_server_address(m, m->current_server_address->addresses_next);
+        else {
+                struct addrinfo hints = {
+                        .ai_flags = AI_NUMERICSERV|AI_ADDRCONFIG,
+                        .ai_socktype = SOCK_DGRAM,
+                };
+
+                /* Hmm, we are through all addresses, let's look for the next host instead */
+                if (m->current_server_name && m->current_server_name->names_next)
+                        manager_set_server_name(m, m->current_server_name->names_next);
+                else {
+                        ServerName *f;
+                        bool restart = true;
+
+                        /* Our current server name list is exhausted,
+                         * let's find the next one to iterate. First
+                         * we try the system list, then the link list.
+                         * After having processed the link list we
+                         * jump back to the system list. However, if
+                         * both lists are empty, we change to the
+                         * fallback list. */
+                        if (!m->current_server_name || m->current_server_name->type == SERVER_LINK) {
+                                f = m->system_servers;
+                                if (!f)
+                                        f = m->link_servers;
+                        } else {
+                                f = m->link_servers;
+                                if (!f)
+                                        f = m->system_servers;
+                                else
+                                        restart = false;
+                        }
+
+                        if (!f)
+                                f = m->fallback_servers;
+
+                        if (!f) {
+                                manager_set_server_name(m, NULL);
+                                log_debug("No server found.");
+                                return 0;
+                        }
+
+                        if (restart && !m->exhausted_servers && m->poll_interval_usec) {
+                                log_debug("Waiting after exhausting servers.");
+                                r = sd_event_add_time(m->event, &m->event_retry, clock_boottime_or_monotonic(), now(clock_boottime_or_monotonic()) + m->poll_interval_usec, 0, manager_retry_connect, m);
+                                if (r < 0)
+                                        return log_error_errno(r, "Failed to create retry timer: %m");
+
+                                m->exhausted_servers = true;
+
+                                /* Increase the polling interval */
+                                if (m->poll_interval_usec < NTP_POLL_INTERVAL_MAX_SEC * USEC_PER_SEC)
+                                        m->poll_interval_usec *= 2;
+
+                                return 0;
+                        }
+
+                        m->exhausted_servers = false;
+
+                        manager_set_server_name(m, f);
+                }
+
+                /* Tell the resolver to reread /etc/resolv.conf, in
+                 * case it changed. */
+                res_init();
+
+                /* Flush out any previously resolved addresses */
+                server_name_flush_addresses(m->current_server_name);
+
+                log_debug("Resolving %s...", m->current_server_name->string);
+
+                r = sd_resolve_getaddrinfo(m->resolve, &m->resolve_query, m->current_server_name->string, "123", &hints, manager_resolve_handler, m);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to create resolver: %m");
+
+                return 1;
+        }
+
+        r = manager_begin(m);
+        if (r < 0)
+                return r;
+
+        return 1;
+}
+
+void manager_disconnect(Manager *m) {
+        assert(m);
+
+        m->resolve_query = sd_resolve_query_unref(m->resolve_query);
+
+        m->event_timer = sd_event_source_unref(m->event_timer);
+
+        manager_listen_stop(m);
+
+        m->event_clock_watch = sd_event_source_unref(m->event_clock_watch);
+        m->clock_watch_fd = safe_close(m->clock_watch_fd);
+
+        m->event_timeout = sd_event_source_unref(m->event_timeout);
+
+        sd_notifyf(false, "STATUS=Idle.");
+}
+
+void manager_flush_server_names(Manager  *m, ServerType t) {
+        assert(m);
+
+        if (t == SERVER_SYSTEM)
+                while (m->system_servers)
+                        server_name_free(m->system_servers);
+
+        if (t == SERVER_LINK)
+                while (m->link_servers)
+                        server_name_free(m->link_servers);
+
+        if (t == SERVER_FALLBACK)
+                while (m->fallback_servers)
+                        server_name_free(m->fallback_servers);
+}
+
+void manager_free(Manager *m) {
+        if (!m)
+                return;
+
+        manager_disconnect(m);
+        manager_flush_server_names(m, SERVER_SYSTEM);
+        manager_flush_server_names(m, SERVER_LINK);
+        manager_flush_server_names(m, SERVER_FALLBACK);
+
+        sd_event_source_unref(m->event_retry);
+
+        sd_event_source_unref(m->network_event_source);
+        sd_network_monitor_unref(m->network_monitor);
+
+        sd_resolve_unref(m->resolve);
+        sd_event_unref(m->event);
+
+        free(m);
+}
+
+static int manager_network_read_link_servers(Manager *m) {
+        _cleanup_strv_free_ char **ntp = NULL;
+        ServerName *n, *nx;
+        char **i;
+        int r;
+
+        assert(m);
+
+        r = sd_network_get_ntp(&ntp);
+        if (r < 0)
+                goto clear;
+
+        LIST_FOREACH(names, n, m->link_servers)
+                n->marked = true;
+
+        STRV_FOREACH(i, ntp) {
+                bool found = false;
+
+                LIST_FOREACH(names, n, m->link_servers)
+                        if (streq(n->string, *i)) {
+                                n->marked = false;
+                                found = true;
+                                break;
+                        }
+
+                if (!found) {
+                        r = server_name_new(m, NULL, SERVER_LINK, *i);
+                        if (r < 0)
+                                goto clear;
+                }
+        }
+
+        LIST_FOREACH_SAFE(names, n, nx, m->link_servers)
+                if (n->marked)
+                        server_name_free(n);
+
+        return 0;
+
+clear:
+        manager_flush_server_names(m, SERVER_LINK);
+        return r;
+}
+
+static int manager_network_event_handler(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
+        Manager *m = userdata;
+        bool connected, online;
+        int r;
+
+        assert(m);
+
+        sd_network_monitor_flush(m->network_monitor);
+
+        manager_network_read_link_servers(m);
+
+        /* check if the machine is online */
+        online = network_is_online();
+
+        /* check if the client is currently connected */
+        connected = m->server_socket >= 0 || m->resolve_query || m->exhausted_servers;
+
+        if (connected && !online) {
+                log_info("No network connectivity, watching for changes.");
+                manager_disconnect(m);
+
+        } else if (!connected && online) {
+                log_info("Network configuration changed, trying to establish connection.");
+
+                if (m->current_server_address)
+                        r = manager_begin(m);
+                else
+                        r = manager_connect(m);
+                if (r < 0)
+                        return r;
+        }
+
+        return 0;
+}
+
+static int manager_network_monitor_listen(Manager *m) {
+        int r, fd, events;
+
+        assert(m);
+
+        r = sd_network_monitor_new(&m->network_monitor, NULL);
+        if (r < 0)
+                return r;
+
+        fd = sd_network_monitor_get_fd(m->network_monitor);
+        if (fd < 0)
+                return fd;
+
+        events = sd_network_monitor_get_events(m->network_monitor);
+        if (events < 0)
+                return events;
+
+        r = sd_event_add_io(m->event, &m->network_event_source, fd, events, manager_network_event_handler, m);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+int manager_new(Manager **ret) {
+        _cleanup_(manager_freep) Manager *m = NULL;
+        int r;
+
+        assert(ret);
+
+        m = new0(Manager, 1);
+        if (!m)
+                return -ENOMEM;
+
+        m->server_socket = m->clock_watch_fd = -1;
+
+        RATELIMIT_INIT(m->ratelimit, RATELIMIT_INTERVAL_USEC, RATELIMIT_BURST);
+
+        r = manager_parse_server_string(m, SERVER_FALLBACK, NTP_SERVERS);
+        if (r < 0)
+                return r;
+
+        r = sd_event_default(&m->event);
+        if (r < 0)
+                return r;
+
+        sd_event_add_signal(m->event, NULL, SIGTERM, NULL,  NULL);
+        sd_event_add_signal(m->event, NULL, SIGINT, NULL, NULL);
+
+        sd_event_set_watchdog(m->event, true);
+
+        r = sd_resolve_default(&m->resolve);
+        if (r < 0)
+                return r;
+
+        r = sd_resolve_attach_event(m->resolve, m->event, 0);
+        if (r < 0)
+                return r;
+
+        r = manager_network_monitor_listen(m);
+        if (r < 0)
+                return r;
+
+        manager_network_read_link_servers(m);
+
+        *ret = m;
+        m = NULL;
+
+        return 0;
+}