rename timedate-sntp to timesync

1 files changed, 792 insertions, 0 deletions

diff --git a/src/timesync/timesyncd.c b/src/timesync/timesyncd.c
new file mode 100644
index 0000000000..5bd61dd07c
--- /dev/null
+++ b/src/timesync/timesyncd.c
@@ -0,0 +1,792 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2014 Kay Sievers
+
+  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 <stdlib.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <string.h>
+#include <time.h>
+#include <math.h>
+#include <arpa/inet.h>
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <sys/timerfd.h>
+#include <sys/timex.h>
+#include <sys/socket.h>
+
+#include "missing.h"
+#include "util.h"
+#include "sparse-endian.h"
+#include "log.h"
+#include "sd-event.h"
+#include "sd-daemon.h"
+
+#define TIME_T_MAX (time_t)((1UL << ((sizeof(time_t) << 3) - 1)) - 1)
+
+#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))
+
+/*
+ * "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        2208988800UL
+
+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_;
+
+typedef struct Manager Manager;
+struct Manager {
+        sd_event *event;
+
+        /* peer */
+        sd_event_source *event_receive;
+        char *server;
+        struct sockaddr_in server_addr;
+        int server_socket;
+        uint64_t packet_count;
+
+        /* last sent packet */
+        struct timespec trans_time_mon;
+        struct timespec trans_time;
+        usec_t retry_interval;
+        bool pending;
+
+        /* poll timer */
+        sd_event_source *event_timer;
+        usec_t poll_interval_usec;
+        bool poll_resync;
+
+        /* history data */
+        struct {
+                double offset;
+                double delay;
+        } samples[8];
+        unsigned int samples_idx;
+        double samples_jitter;
+
+        /* last change */
+        bool jumped;
+
+        /* watch for time changes */
+        sd_event_source *event_clock_watch;
+        int clock_watch_fd;
+};
+
+static void manager_free(Manager *m);
+DEFINE_TRIVIAL_CLEANUP_FUNC(Manager*, manager_free);
+#define _cleanup_manager_free_ _cleanup_(manager_freep)
+
+static int sntp_arm_timer(Manager *m, usec_t next);
+static int sntp_clock_watch_setup(Manager *m);
+static void sntp_server_disconnect(Manager *m);
+
+static double ntp_ts_to_d(const struct ntp_ts *ts) {
+        return be32toh(ts->sec) + ((double)be32toh(ts->frac) / UINT_MAX);
+}
+
+static double tv_to_d(const struct timeval *tv) {
+        return tv->tv_sec + (1.0e-6 * tv->tv_usec);
+}
+
+static double ts_to_d(const struct timespec *ts) {
+        return ts->tv_sec + (1.0e-9 * ts->tv_nsec);
+}
+
+static void d_to_tv(double d, struct timeval *tv) {
+        tv->tv_sec = (long)d;
+        tv->tv_usec = (d - tv->tv_sec) * 1000 * 1000;
+
+        /* the kernel expects -0.3s as {-1, 7000.000} */
+        if (tv->tv_usec < 0) {
+                tv->tv_sec  -= 1;
+                tv->tv_usec += 1000 * 1000;
+        }
+}
+
+static double square(double d) {
+        return d * d;
+}
+
+static int sntp_send_request(Manager *m) {
+        struct ntp_msg ntpmsg = {};
+        struct sockaddr_in addr = {};
+        ssize_t len;
+        int r;
+
+        /*
+         * "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."
+         */
+        ntpmsg.field = NTP_FIELD(0, 4, NTP_MODE_CLIENT);
+
+        /*
+         * 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.
+         */
+        clock_gettime(CLOCK_MONOTONIC, &m->trans_time_mon);
+        clock_gettime(CLOCK_REALTIME, &m->trans_time);
+        ntpmsg.trans_time.sec = htobe32(m->trans_time.tv_sec + OFFSET_1900_1970);
+        ntpmsg.trans_time.frac = htobe32(m->trans_time.tv_nsec);
+
+        addr.sin_family = AF_INET;
+        addr.sin_port = htobe16(123);
+        addr.sin_addr.s_addr = inet_addr(m->server);
+        len = sendto(m->server_socket, &ntpmsg, sizeof(ntpmsg), MSG_DONTWAIT, &addr, sizeof(addr));
+        if (len == sizeof(ntpmsg)) {
+                m->pending = true;
+                log_debug("Sent NTP request to: %s", m->server);
+        } else
+                log_debug("Sending NTP request to %s failed: %m", m->server);
+
+        /* re-arm timer with incresing 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 = sntp_arm_timer(m, m->retry_interval);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+static int sntp_timer(sd_event_source *source, usec_t usec, void *userdata) {
+        Manager *m = userdata;
+
+        assert(m);
+
+        sntp_send_request(m);
+        return 0;
+}
+
+static int sntp_arm_timer(Manager *m, usec_t next) {
+        int r;
+
+        assert(m);
+        assert(m->event_receive);
+
+        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_MONOTONIC) + next);
+                if (r < 0)
+                        return r;
+
+                return sd_event_source_set_enabled(m->event_timer, SD_EVENT_ONESHOT);
+        }
+
+        r = sd_event_add_time(
+                        m->event,
+                        &m->event_timer,
+                        CLOCK_MONOTONIC,
+                        now(CLOCK_MONOTONIC) + next, 0,
+                        sntp_timer, m);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+static int sntp_clock_watch(sd_event_source *source, int fd, uint32_t revents, void *userdata) {
+        Manager *m = userdata;
+
+        assert(m);
+        assert(m->event_receive);
+
+        /* rearm timer */
+        sntp_clock_watch_setup(m);
+
+        /* skip our own jumps */
+        if (m->jumped) {
+                m->jumped = false;
+                return 0;
+        }
+
+        /* resync */
+        log_info("System time changed. Resyncing.");
+        m->poll_resync = true;
+        sntp_send_request(m);
+
+        return 0;
+}
+
+/* wake up when the system time changes underneath us */
+static int sntp_clock_watch_setup(Manager *m) {
+        struct itimerspec its = { .it_value.tv_sec = TIME_T_MAX };
+        _cleanup_close_ int fd = -1;
+        sd_event *e;
+        sd_event_source *source;
+        int r;
+
+        assert(m);
+        assert(m->event_receive);
+
+        fd = timerfd_create(CLOCK_REALTIME, TFD_NONBLOCK|TFD_CLOEXEC);
+        if (fd < 0) {
+                log_error("Failed to create timerfd: %m");
+                return -errno;
+        }
+
+        if (timerfd_settime(fd, TFD_TIMER_ABSTIME|TFD_TIMER_CANCEL_ON_SET, &its, NULL) < 0) {
+                log_error("Failed to set up timerfd: %m");
+                return -errno;
+        }
+
+        e = sd_event_source_get_event(m->event_receive);
+        r = sd_event_add_io(e, &source, fd, EPOLLIN, sntp_clock_watch, m);
+        if (r < 0) {
+                log_error("Failed to create clock watch event source: %s", strerror(-r));
+                return r;
+        }
+
+        sd_event_source_unref(m->event_clock_watch);
+        m->event_clock_watch = source;
+
+        if (m->clock_watch_fd >= 0)
+                close(m->clock_watch_fd);
+        m->clock_watch_fd = fd;
+        fd = -1;
+
+        return 0;
+}
+
+static int sntp_adjust_clock(Manager *m, double offset, int leap_sec) {
+        struct timex tmx = {};
+        int r;
+
+        /*
+         * For small deltas, tell the kernel to gradually adjust the system
+         * clock to the NTP time, larger deltas are just directly set.
+         *
+         * Clear STA_UNSYNC, it will enable the kernel's 11-minute mode, which
+         * syncs the system time periodically to the hardware clock.
+         */
+        if (fabs(offset) < NTP_MAX_ADJUST) {
+                tmx.modes = ADJ_STATUS | ADJ_OFFSET | ADJ_TIMECONST | ADJ_MAXERROR | ADJ_ESTERROR;
+                tmx.status = STA_PLL;
+                tmx.offset = offset * USEC_PER_SEC;
+                tmx.constant = log2i(m->poll_interval_usec / USEC_PER_SEC) - 6;
+                tmx.maxerror = 0;
+                tmx.esterror = 0;
+                log_debug("  adjust (slew): %+f sec\n", (double)tmx.offset / USEC_PER_SEC);
+        } else {
+                tmx.modes = ADJ_SETOFFSET;
+                d_to_tv(offset, &tmx.time);
+
+                m->jumped = true;
+                log_debug("  adjust (jump): %+f sec\n", tv_to_d(&tmx.time));
+        }
+
+        switch (leap_sec) {
+        case 1:
+                tmx.status |= STA_INS;
+                break;
+        case -1:
+                tmx.status |= STA_DEL;
+                break;
+        }
+
+        //r = clock_adjtime(CLOCK_REALTIME, &tmx);
+        r = adjtimex(&tmx);
+        if (r < 0)
+                return r;
+
+        log_debug("  status       : %04i %s\n"
+                  "  time now     : %li.%06li\n"
+                  "  constant     : %li\n"
+                  "  offset       : %+f sec\n"
+                  "  freq offset  : %+li (%+.3f ppm)\n",
+                  tmx.status, tmx.status & STA_UNSYNC ? "" : "sync",
+                  tmx.time.tv_sec, tmx.time.tv_usec,
+                  tmx.constant,
+                  (double)tmx.offset / USEC_PER_SEC,
+                  tmx.freq, (double)tmx.freq / 65536);
+
+        return 0;
+}
+
+static bool sntp_sample_spike_detection(Manager *m, double offset, double delay) {
+        unsigned int i, idx_cur, idx_new, idx_min;
+        double jitter;
+        double j;
+
+        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 += square(m->samples[i].offset - m->samples[idx_min].offset);
+        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 sntp_adjust_poll(Manager *m, double offset, bool spike) {
+        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 sntp_receive_response(sd_event_source *source, int fd, uint32_t revents, void *userdata) {
+        Manager *m = userdata;
+        unsigned char buf[sizeof(struct ntp_msg)];
+        struct iovec iov = {
+                .iov_base = buf,
+                .iov_len = sizeof(buf),
+        };
+        union {
+                struct cmsghdr cmsghdr;
+                uint8_t buf[CMSG_SPACE(sizeof(struct timeval))];
+        } control;
+        struct sockaddr_in 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 now_ts;
+        struct timeval *recv_time;
+        ssize_t len;
+        struct ntp_msg *ntpmsg;
+        double origin, receive, trans, dest;
+        double delay, offset;
+        bool spike;
+        int leap_sec;
+        int r;
+
+        if (revents & (EPOLLHUP|EPOLLERR)) {
+                log_debug("Server connection returned error. Closing.");
+                sntp_server_disconnect(m);
+                return -ENOTCONN;
+        }
+
+        len = recvmsg(fd, &msghdr, MSG_DONTWAIT);
+        if (len < 0) {
+                log_debug("Error receiving message. Disconnecting.");
+                return -EINVAL;
+        }
+
+        if (iov.iov_len < sizeof(struct ntp_msg)) {
+                log_debug("Invalid response from server. Disconnecting.");
+                return -EINVAL;
+        }
+
+        if (m->server_addr.sin_addr.s_addr != server_addr.sin_addr.s_addr) {
+                log_debug("Response from unknown server. Disconnecting.");
+                return -EINVAL;
+        }
+
+        recv_time = NULL;
+        for (cmsg = CMSG_FIRSTHDR(&msghdr); cmsg; cmsg = CMSG_NXTHDR(&msghdr, cmsg)) {
+                if (cmsg->cmsg_level != SOL_SOCKET)
+                        continue;
+
+                switch (cmsg->cmsg_type) {
+                case SCM_TIMESTAMP:
+                        recv_time = (struct timeval *) CMSG_DATA(cmsg);
+                        break;
+                }
+        }
+        if (!recv_time) {
+                log_debug("Invalid packet timestamp. Disconnecting.");
+                return -EINVAL;
+        }
+
+        ntpmsg = iov.iov_base;
+        if (!m->pending) {
+                log_debug("Unexpected reply. Ignoring.");
+                return 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;
+        }
+
+        if (NTP_FIELD_LEAP(ntpmsg->field) == NTP_LEAP_NOTINSYNC) {
+                log_debug("Server is not synchronized. Disconnecting.");
+                return -EINVAL;
+        }
+
+        if (NTP_FIELD_VERSION(ntpmsg->field) != 4) {
+                log_debug("Response NTPv%d. Disconnecting.", NTP_FIELD_VERSION(ntpmsg->field));
+                return -EINVAL;
+        }
+
+        if (NTP_FIELD_MODE(ntpmsg->field) != NTP_MODE_SERVER) {
+                log_debug("Unsupported mode %d. Disconnecting.", NTP_FIELD_MODE(ntpmsg->field));
+                return -EINVAL;
+        }
+
+        /* valid packet */
+        m->pending = false;
+        m->retry_interval = 0;
+
+        /* 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"
+         */
+        clock_gettime(CLOCK_MONOTONIC, &now_ts);
+        origin = tv_to_d(recv_time) - (ts_to_d(&now_ts) - ts_to_d(&m->trans_time_mon)) + OFFSET_1900_1970;
+        receive = ntp_ts_to_d(&ntpmsg->recv_time);
+        trans = ntp_ts_to_d(&ntpmsg->trans_time);
+        dest = tv_to_d(recv_time) + OFFSET_1900_1970;
+
+        offset = ((receive - origin) + (trans - dest)) / 2;
+        delay = (dest - origin) - (trans - receive);
+
+        spike = sntp_sample_spike_detection(m, offset, delay);
+
+        sntp_adjust_poll(m, offset, spike);
+
+        log_debug("NTP response:\n"
+                  "  leap         : %u\n"
+                  "  version      : %u\n"
+                  "  mode         : %u\n"
+                  "  stratum      : %u\n"
+                  "  precision    : %f sec (%d)\n"
+                  "  reference    : %.4s\n"
+                  "  origin       : %f\n"
+                  "  receive      : %f\n"
+                  "  transmit     : %f\n"
+                  "  dest         : %f\n"
+                  "  offset       : %+f sec\n"
+                  "  delay        : %+f sec\n"
+                  "  packet count : %"PRIu64"\n"
+                  "  jitter       : %f%s\n"
+                  "  poll interval: %llu\n",
+                  NTP_FIELD_LEAP(ntpmsg->field),
+                  NTP_FIELD_VERSION(ntpmsg->field),
+                  NTP_FIELD_MODE(ntpmsg->field),
+                  ntpmsg->stratum,
+                  exp2(ntpmsg->precision), ntpmsg->precision,
+                  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);
+
+        log_info("%4llu %+10f %10f %10f%s",
+                 m->poll_interval_usec / USEC_PER_SEC, offset, delay, m->samples_jitter, spike ? " spike" : "");
+
+        if (!spike) {
+                r = sntp_adjust_clock(m, offset, leap_sec);
+                if (r < 0)
+                        log_error("Failed to call clock_adjtime(): %m");
+        }
+
+        r = sntp_arm_timer(m, m->poll_interval_usec);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+static int sntp_server_connect(Manager *m, const char *server) {
+        _cleanup_free_ char *s = NULL;
+
+        assert(m);
+        assert(server);
+        assert(m->server_socket >= 0);
+
+        s = strdup(server);
+        if (!s)
+                return -ENOMEM;
+
+        free(m->server);
+        m->server = s;
+        s = NULL;
+
+        zero(m->server_addr);
+        m->server_addr.sin_family = AF_INET;
+        m->server_addr.sin_addr.s_addr = inet_addr(server);
+
+        m->poll_interval_usec = NTP_POLL_INTERVAL_MIN_SEC * USEC_PER_SEC;
+
+        return sntp_send_request(m);
+}
+
+static void sntp_server_disconnect(Manager *m) {
+        if (!m->server)
+                return;
+
+        m->event_timer = sd_event_source_unref(m->event_timer);
+
+        m->event_clock_watch = sd_event_source_unref(m->event_clock_watch);
+        if (m->clock_watch_fd > 0)
+                close(m->clock_watch_fd);
+        m->clock_watch_fd = -1;
+
+        m->event_receive = sd_event_source_unref(m->event_receive);
+        if (m->server_socket > 0)
+                close(m->server_socket);
+        m->server_socket = -1;
+
+        zero(m->server_addr);
+        free(m->server);
+        m->server = NULL;
+}
+
+static int sntp_listen_setup(Manager *m) {
+        _cleanup_close_ int fd = -1;
+        struct sockaddr_in addr;
+        const int on = 1;
+        const int tos = IPTOS_LOWDELAY;
+        int r;
+
+        fd = socket(PF_INET, SOCK_DGRAM | SOCK_CLOEXEC, 0);
+        if (fd < 0)
+                return -errno;
+
+        zero(addr);
+        addr.sin_family = AF_INET;
+        r = bind(fd, (struct sockaddr *)&addr, sizeof(addr));
+        if (r < 0)
+                return -errno;
+
+        r = setsockopt(fd, SOL_SOCKET, SO_TIMESTAMP, &on, sizeof(on));
+        if (r < 0)
+                return -errno;
+
+        r = setsockopt(fd, IPPROTO_IP, IP_TOS, &tos, sizeof(tos));
+        if (r < 0)
+                return -errno;
+
+        r = sd_event_add_io(m->event, &m->event_receive, fd, EPOLLIN, sntp_receive_response, m);
+        if (r < 0)
+                return r;
+
+        m->server_socket = fd;
+        fd = -1;
+
+        return 0;
+}
+
+static int manager_new(Manager **ret) {
+        _cleanup_manager_free_ Manager *m = NULL;
+        int r;
+
+        m = new0(Manager, 1);
+        if (!m)
+                return -ENOMEM;
+
+        r = sd_event_default(&m->event);
+        if (r < 0)
+                return r;
+
+        r = sntp_listen_setup(m);
+        if (r < 0)
+                return r;
+
+        r = sntp_clock_watch_setup(m);
+        if (r < 0)
+                return r;
+
+        *ret = m;
+        m = NULL;
+
+        return 0;
+}
+
+static void manager_free(Manager *m) {
+
+        if (!m)
+                return;
+
+        sd_event_unref(m->event);
+        free(m);
+}
+
+int main(int argc, char *argv[]) {
+        _cleanup_manager_free_ Manager *m = NULL;
+        const char *server;
+        int r;
+
+        log_set_target(LOG_TARGET_AUTO);
+        log_parse_environment();
+        log_open();
+
+        r = manager_new(&m);
+        if (r < 0)
+                goto out;
+
+        //server = "216.239.32.15";       /* time1.google.com */
+        //server = "192.53.103.108";      /* ntp1.ptb.de */
+        server = "27.54.95.11";         /* au.pool.ntp.org */
+
+        sd_notifyf(false,
+                  "READY=1\n"
+                  "STATUS=Connecting to %s", server);
+
+        r = sntp_server_connect(m, server);
+        if (r < 0)
+                goto out;
+
+        r = sd_event_loop(m->event);
+        if (r < 0)
+                goto out;
+
+out:
+        return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
+}