Adding upstream version 255.4.upstream/255.4

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

19 files changed, 2841 insertions, 0 deletions

diff --git a/src/timesync/80-systemd-timesync.list b/src/timesync/80-systemd-timesync.list
new file mode 100644
index 0000000..95e15f7
--- /dev/null
+++ b/src/timesync/80-systemd-timesync.list
@@ -0,0 +1,4 @@
+# This file is part of systemd.
+# See systemd-timedated.service(8) for more information.
+
+systemd-timesyncd.service
diff --git a/src/timesync/meson.build b/src/timesync/meson.build
new file mode 100644
index 0000000..6844480
--- /dev/null
+++ b/src/timesync/meson.build
@@ -0,0 +1,80 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+sources = files(
+        'timesyncd-conf.c',
+        'timesyncd-manager.c',
+        'timesyncd-server.c',
+)
+
+systemd_timesyncd_sources = files(
+        'timesyncd.c',
+        'timesyncd-bus.c',
+)
+
+sources += custom_target(
+        'timesyncd-gperf.c',
+        input : 'timesyncd-gperf.gperf',
+        output : 'timesyncd-gperf.c',
+        command : [gperf, '@INPUT@', '--output-file', '@OUTPUT@'])
+
+if get_option('link-timesyncd-shared')
+        timesyncd_link_with = [libshared]
+else
+        timesyncd_link_with = [libsystemd_static,
+                               libshared_static,
+                               libbasic_gcrypt]
+endif
+
+libtimesyncd_core = static_library(
+        'timesyncd-core',
+        sources,
+        include_directories : includes,
+        dependencies : userspace,
+        link_with : timesyncd_link_with,
+        build_by_default : false)
+
+executables += [
+        libexec_template + {
+                'name' : 'systemd-timesyncd',
+                'conditions' : ['ENABLE_TIMESYNCD'],
+                'sources' : systemd_timesyncd_sources,
+                'link_with' : libtimesyncd_core,
+                'dependencies' : [
+                        libm,
+                        threads,
+                ],
+        },
+        libexec_template + {
+                'name' : 'systemd-time-wait-sync',
+                'conditions' : ['ENABLE_TIMESYNCD'],
+                'sources' : files('wait-sync.c'),
+                'link_with' : libtimesyncd_core,
+        },
+        test_template + {
+                'sources' : files('test-timesync.c'),
+                'link_with' : [
+                        libshared,
+                        libtimesyncd_core,
+                ],
+                'dependencies' : libm,
+        },
+]
+
+custom_target(
+        'timesyncd.conf',
+        input : 'timesyncd.conf.in',
+        output : 'timesyncd.conf',
+        command : [jinja2_cmdline, '@INPUT@', '@OUTPUT@'],
+        install : conf.get('ENABLE_TIMESYNCD') == 1 and install_sysconfdir_samples,
+        install_dir : pkgconfigfiledir)
+
+if conf.get('ENABLE_TIMESYNCD') == 1
+        install_data('org.freedesktop.timesync1.conf',
+                     install_dir : dbuspolicydir)
+        install_data('org.freedesktop.timesync1.service',
+                     install_dir : dbussystemservicedir)
+        install_data('80-systemd-timesync.list',
+                     install_dir : ntpservicelistdir)
+        install_data('org.freedesktop.timesync1.policy',
+                     install_dir : polkitpolicydir)
+endif
diff --git a/src/timesync/org.freedesktop.timesync1.conf b/src/timesync/org.freedesktop.timesync1.conf
new file mode 100644
index 0000000..d33b864
--- /dev/null
+++ b/src/timesync/org.freedesktop.timesync1.conf
@@ -0,0 +1,46 @@
+<?xml version="1.0"?> <!--*-nxml-*-->
+<!DOCTYPE busconfig PUBLIC "-//freedesktop//DTD D-BUS Bus Configuration 1.0//EN"
+        "https://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd">
+
+<!--
+  This file is part of systemd.
+
+  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.
+-->
+
+<busconfig>
+
+        <policy user="systemd-timesync">
+                <allow own="org.freedesktop.timesync1"/>
+                <allow send_destination="org.freedesktop.timesync1"/>
+                <allow receive_sender="org.freedesktop.timesync1"/>
+        </policy>
+
+        <policy context="default">
+                <deny send_destination="org.freedesktop.timesync1"/>
+
+                <allow send_destination="org.freedesktop.timesync1"
+                       send_interface="org.freedesktop.DBus.Introspectable"/>
+
+                <allow send_destination="org.freedesktop.timesync1"
+                       send_interface="org.freedesktop.DBus.Peer"/>
+
+                <allow send_destination="org.freedesktop.timesync1"
+                       send_interface="org.freedesktop.DBus.Properties"
+                       send_member="Get"/>
+
+                <allow send_destination="org.freedesktop.timesync1"
+                       send_interface="org.freedesktop.DBus.Properties"
+                       send_member="GetAll"/>
+
+                <allow send_destination="org.freedesktop.timesync1"
+                       send_interface="org.freedesktop.timesync1.Manager"
+                       send_member="SetRuntimeNTPServers"/>
+
+                <allow receive_sender="org.freedesktop.timesync1"/>
+        </policy>
+
+</busconfig>
diff --git a/src/timesync/org.freedesktop.timesync1.policy b/src/timesync/org.freedesktop.timesync1.policy
new file mode 100644
index 0000000..e73965c
--- /dev/null
+++ b/src/timesync/org.freedesktop.timesync1.policy
@@ -0,0 +1,32 @@
+<?xml version="1.0" encoding="UTF-8"?> <!--*-nxml-*-->
+<!DOCTYPE policyconfig PUBLIC "-//freedesktop//DTD PolicyKit Policy Configuration 1.0//EN"
+        "https://www.freedesktop.org/standards/PolicyKit/1/policyconfig.dtd">
+
+<!--
+  SPDX-License-Identifier: LGPL-2.1-or-later
+
+  This file is part of systemd.
+
+  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.
+-->
+
+<policyconfig>
+
+        <vendor>The systemd Project</vendor>
+        <vendor_url>https://systemd.io</vendor_url>
+
+        <action id="org.freedesktop.timesync1.set-runtime-servers">
+                <description gettext-domain="systemd">Set runtime NTP servers</description>
+                <message gettext-domain="systemd">Authentication is required to set runtime NTP servers.</message>
+                <defaults>
+                        <allow_any>auth_admin</allow_any>
+                        <allow_inactive>auth_admin</allow_inactive>
+                        <allow_active>auth_admin_keep</allow_active>
+                </defaults>
+                <annotate key="org.freedesktop.policykit.owner">unix-user:systemd-timesync</annotate>
+        </action>
+
+</policyconfig>
diff --git a/src/timesync/org.freedesktop.timesync1.service b/src/timesync/org.freedesktop.timesync1.service
new file mode 100644
index 0000000..98878d6
--- /dev/null
+++ b/src/timesync/org.freedesktop.timesync1.service
@@ -0,0 +1,14 @@
+#  SPDX-License-Identifier: LGPL-2.1-or-later
+#
+#  This file is part of systemd.
+#
+#  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.
+
+[D-BUS Service]
+Name=org.freedesktop.timesync1
+Exec=/bin/false
+User=root
+SystemdService=dbus-org.freedesktop.timesync1.service
diff --git a/src/timesync/test-timesync.c b/src/timesync/test-timesync.c
new file mode 100644
index 0000000..7993e4c
--- /dev/null
+++ b/src/timesync/test-timesync.c
@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+/* Some unit tests for the helper functions in timesyncd. */
+
+#include "log.h"
+#include "macro.h"
+#include "timesyncd-conf.h"
+#include "tests.h"
+
+TEST(manager_parse_string) {
+        /* Make sure that NTP_SERVERS is configured to something
+         * that we can actually parse successfully. */
+
+        _cleanup_(manager_freep) Manager *m = NULL;
+
+        assert_se(manager_new(&m) == 0);
+
+        assert_se(!m->have_fallbacks);
+        assert_se(manager_parse_server_string(m, SERVER_FALLBACK, NTP_SERVERS) == 0);
+        assert_se(m->have_fallbacks);
+        assert_se(manager_parse_fallback_string(m, NTP_SERVERS) == 0);
+
+        assert_se(manager_parse_server_string(m, SERVER_SYSTEM, "time1.foobar.com time2.foobar.com axrfav.,avf..ra 12345..123") == 0);
+        assert_se(manager_parse_server_string(m, SERVER_FALLBACK, "time1.foobar.com time2.foobar.com axrfav.,avf..ra 12345..123") == 0);
+        assert_se(manager_parse_server_string(m, SERVER_LINK, "time1.foobar.com time2.foobar.com axrfav.,avf..ra 12345..123") == 0);
+}
+
+DEFINE_TEST_MAIN(LOG_DEBUG);
diff --git a/src/timesync/timesyncd-bus.c b/src/timesync/timesyncd-bus.c
new file mode 100644
index 0000000..7237080
--- /dev/null
+++ b/src/timesync/timesyncd-bus.c
@@ -0,0 +1,264 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <sys/capability.h>
+
+#include "sd-bus.h"
+
+#include "alloc-util.h"
+#include "bus-get-properties.h"
+#include "bus-internal.h"
+#include "bus-log-control-api.h"
+#include "bus-polkit.h"
+#include "bus-protocol.h"
+#include "bus-util.h"
+#include "dns-domain.h"
+#include "in-addr-util.h"
+#include "log.h"
+#include "macro.h"
+#include "strv.h"
+#include "time-util.h"
+#include "timesyncd-bus.h"
+#include "user-util.h"
+
+static int property_get_servers(
+                sd_bus *bus,
+                const char *path,
+                const char *interface,
+                const char *property,
+                sd_bus_message *reply,
+                void *userdata,
+                sd_bus_error *error) {
+
+        ServerName **s = ASSERT_PTR(userdata);
+        int r;
+
+        assert(bus);
+        assert(reply);
+
+        r = sd_bus_message_open_container(reply, 'a', "s");
+        if (r < 0)
+                return r;
+
+        LIST_FOREACH(names, p, *s) {
+                r = sd_bus_message_append(reply, "s", p->string);
+                if (r < 0)
+                        return r;
+        }
+
+        return sd_bus_message_close_container(reply);
+}
+
+static int method_set_runtime_servers(sd_bus_message *message, void *userdata, sd_bus_error *error) {
+        _cleanup_strv_free_ char **msg_names = NULL;
+        Manager *m = ASSERT_PTR(userdata);
+        int r;
+
+        assert(message);
+
+        r = sd_bus_message_read_strv(message, &msg_names);
+        if (r < 0)
+                return r;
+
+        STRV_FOREACH(name, msg_names) {
+                r = dns_name_is_valid_or_address(*name);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to check validity of NTP server name or address '%s': %m", *name);
+                if (r == 0)
+                        return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS, "Invalid NTP server name or address, refusing: %s", *name);
+        }
+
+        r = bus_verify_polkit_async(message, CAP_NET_ADMIN,
+                                    "org.freedesktop.timesync1.set-runtime-servers",
+                                    NULL, true, UID_INVALID,
+                                    &m->polkit_registry, error);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                /* Polkit will call us back */
+                return 1;
+
+        manager_flush_runtime_servers(m);
+
+        STRV_FOREACH(name, msg_names) {
+                r = server_name_new(m, NULL, SERVER_RUNTIME, *name);
+                if (r < 0) {
+                        manager_flush_runtime_servers(m);
+
+                        return log_error_errno(r, "Failed to add runtime server '%s': %m", *name);
+                }
+        }
+
+        m->exhausted_servers = true;
+        manager_set_server_name(m, NULL);
+        (void) manager_connect(m);
+
+        return sd_bus_reply_method_return(message, NULL);
+}
+
+static int property_get_current_server_name(
+                sd_bus *bus,
+                const char *path,
+                const char *interface,
+                const char *property,
+                sd_bus_message *reply,
+                void *userdata,
+                sd_bus_error *error) {
+
+        ServerName **s = ASSERT_PTR(userdata);
+
+        assert(bus);
+        assert(reply);
+
+        return sd_bus_message_append(reply, "s", *s ? (*s)->string : NULL);
+}
+
+static int property_get_current_server_address(
+                sd_bus *bus,
+                const char *path,
+                const char *interface,
+                const char *property,
+                sd_bus_message *reply,
+                void *userdata,
+                sd_bus_error *error) {
+
+        ServerAddress *a;
+        int r;
+
+        assert(bus);
+        assert(reply);
+        assert(userdata);
+
+        a = *(ServerAddress **) userdata;
+
+        if (!a)
+                return sd_bus_message_append(reply, "(iay)", AF_UNSPEC, 0);
+
+        assert(IN_SET(a->sockaddr.sa.sa_family, AF_INET, AF_INET6));
+
+        r = sd_bus_message_open_container(reply, 'r', "iay");
+        if (r < 0)
+                return r;
+
+        r = sd_bus_message_append(reply, "i", a->sockaddr.sa.sa_family);
+        if (r < 0)
+                return r;
+
+        r = sd_bus_message_append_array(reply, 'y',
+                                        a->sockaddr.sa.sa_family == AF_INET ? (void*) &a->sockaddr.in.sin_addr : (void*) &a->sockaddr.in6.sin6_addr,
+                                        FAMILY_ADDRESS_SIZE(a->sockaddr.sa.sa_family));
+        if (r < 0)
+                return r;
+
+        return sd_bus_message_close_container(reply);
+}
+
+static usec_t ntp_ts_short_to_usec(const struct ntp_ts_short *ts) {
+        return be16toh(ts->sec) * USEC_PER_SEC + (be16toh(ts->frac) * USEC_PER_SEC) / (usec_t) 0x10000ULL;
+}
+
+static usec_t ntp_ts_to_usec(const struct ntp_ts *ts) {
+        return (be32toh(ts->sec) - OFFSET_1900_1970) * USEC_PER_SEC + (be32toh(ts->frac) * USEC_PER_SEC) / (usec_t) 0x100000000ULL;
+}
+
+static int property_get_ntp_message(
+                sd_bus *bus,
+                const char *path,
+                const char *interface,
+                const char *property,
+                sd_bus_message *reply,
+                void *userdata,
+                sd_bus_error *error) {
+
+        Manager *m = ASSERT_PTR(userdata);
+        int r;
+
+        assert(reply);
+
+        r = sd_bus_message_open_container(reply, 'r', "uuuuittayttttbtt");
+        if (r < 0)
+                return r;
+
+        r = sd_bus_message_append(reply, "uuuuitt",
+                                  NTP_FIELD_LEAP(m->ntpmsg.field),
+                                  NTP_FIELD_VERSION(m->ntpmsg.field),
+                                  NTP_FIELD_MODE(m->ntpmsg.field),
+                                  m->ntpmsg.stratum,
+                                  m->ntpmsg.precision,
+                                  ntp_ts_short_to_usec(&m->ntpmsg.root_delay),
+                                  ntp_ts_short_to_usec(&m->ntpmsg.root_dispersion));
+        if (r < 0)
+                return r;
+
+        r = sd_bus_message_append_array(reply, 'y', m->ntpmsg.refid, 4);
+        if (r < 0)
+                return r;
+
+        r = sd_bus_message_append(reply, "ttttbtt",
+                                  timespec_load(&m->origin_time),
+                                  ntp_ts_to_usec(&m->ntpmsg.recv_time),
+                                  ntp_ts_to_usec(&m->ntpmsg.trans_time),
+                                  timespec_load(&m->dest_time),
+                                  m->spike,
+                                  m->packet_count,
+                                  (usec_t) (m->samples_jitter * USEC_PER_SEC));
+        if (r < 0)
+                return r;
+
+        return sd_bus_message_close_container(reply);
+}
+
+static const sd_bus_vtable manager_vtable[] = {
+        SD_BUS_VTABLE_START(0),
+
+        SD_BUS_PROPERTY("LinkNTPServers", "as", property_get_servers, offsetof(Manager, link_servers), SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
+        SD_BUS_PROPERTY("SystemNTPServers", "as", property_get_servers, offsetof(Manager, system_servers), SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
+        SD_BUS_PROPERTY("RuntimeNTPServers", "as", property_get_servers, offsetof(Manager, runtime_servers), SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
+        SD_BUS_PROPERTY("FallbackNTPServers", "as", property_get_servers, offsetof(Manager, fallback_servers), SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
+        SD_BUS_PROPERTY("ServerName", "s", property_get_current_server_name, offsetof(Manager, current_server_name), 0),
+        SD_BUS_PROPERTY("ServerAddress", "(iay)", property_get_current_server_address, offsetof(Manager, current_server_address), 0),
+        SD_BUS_PROPERTY("RootDistanceMaxUSec", "t", bus_property_get_usec, offsetof(Manager, root_distance_max_usec), SD_BUS_VTABLE_PROPERTY_CONST),
+        SD_BUS_PROPERTY("PollIntervalMinUSec", "t", bus_property_get_usec, offsetof(Manager, poll_interval_min_usec), SD_BUS_VTABLE_PROPERTY_CONST),
+        SD_BUS_PROPERTY("PollIntervalMaxUSec", "t", bus_property_get_usec, offsetof(Manager, poll_interval_max_usec), SD_BUS_VTABLE_PROPERTY_CONST),
+        SD_BUS_PROPERTY("PollIntervalUSec", "t", bus_property_get_usec, offsetof(Manager, poll_interval_usec), 0),
+        SD_BUS_PROPERTY("NTPMessage", "(uuuuittayttttbtt)", property_get_ntp_message, 0, SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
+        SD_BUS_PROPERTY("Frequency", "x", NULL, offsetof(Manager, drift_freq), 0),
+
+        SD_BUS_METHOD_WITH_ARGS("SetRuntimeNTPServers",
+                                SD_BUS_ARGS("as", runtime_servers),
+                                SD_BUS_NO_RESULT,
+                                method_set_runtime_servers,
+                                SD_BUS_VTABLE_UNPRIVILEGED),
+
+        SD_BUS_VTABLE_END
+};
+
+int manager_connect_bus(Manager *m) {
+        int r;
+
+        assert(m);
+
+        if (m->bus)
+                return 0;
+
+        r = bus_open_system_watch_bind_with_description(&m->bus, "bus-api-timesync");
+        if (r < 0)
+                return log_error_errno(r, "Failed to connect to bus: %m");
+
+        r = sd_bus_add_object_vtable(m->bus, NULL, "/org/freedesktop/timesync1", "org.freedesktop.timesync1.Manager", manager_vtable, m);
+        if (r < 0)
+                return log_error_errno(r, "Failed to add manager object vtable: %m");
+
+        r = bus_log_control_api_register(m->bus);
+        if (r < 0)
+                return r;
+
+        r = sd_bus_request_name_async(m->bus, NULL, "org.freedesktop.timesync1", 0, NULL, NULL);
+        if (r < 0)
+                return log_error_errno(r, "Failed to request name: %m");
+
+        r = sd_bus_attach_event(m->bus, m->event, 0);
+        if (r < 0)
+                return log_error_errno(r, "Failed to attach bus to event loop: %m");
+
+        return 0;
+}
diff --git a/src/timesync/timesyncd-bus.h b/src/timesync/timesyncd-bus.h
new file mode 100644
index 0000000..83db216
--- /dev/null
+++ b/src/timesync/timesyncd-bus.h
@@ -0,0 +1,6 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include "timesyncd-manager.h"
+
+int manager_connect_bus(Manager *m);
diff --git a/src/timesync/timesyncd-conf.c b/src/timesync/timesyncd-conf.c
new file mode 100644
index 0000000..9c0b6f7
--- /dev/null
+++ b/src/timesync/timesyncd-conf.c
@@ -0,0 +1,127 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "alloc-util.h"
+#include "constants.h"
+#include "dns-domain.h"
+#include "extract-word.h"
+#include "string-util.h"
+#include "timesyncd-conf.h"
+#include "timesyncd-manager.h"
+#include "timesyncd-server.h"
+
+int manager_parse_server_string(Manager *m, ServerType type, const char *string) {
+        ServerName *first;
+        int r;
+
+        assert(m);
+        assert(string);
+
+        first = type == SERVER_FALLBACK ? m->fallback_servers : m->system_servers;
+
+        if (type == SERVER_FALLBACK)
+                 m->have_fallbacks = true;
+
+        for (;;) {
+                _cleanup_free_ char *word = NULL;
+                bool found = false;
+
+                r = extract_first_word(&string, &word, NULL, 0);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to parse timesyncd server syntax \"%s\": %m", string);
+                if (r == 0)
+                        break;
+
+                r = dns_name_is_valid_or_address(word);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to check validity of NTP server name or address '%s': %m", word);
+                if (r == 0) {
+                        log_error("Invalid NTP server name or address, ignoring: %s", word);
+                        continue;
+                }
+
+                /* Filter out duplicates */
+                LIST_FOREACH(names, n, first)
+                        if (streq_ptr(n->string, word)) {
+                                found = true;
+                                break;
+                        }
+
+                if (found)
+                        continue;
+
+                r = server_name_new(m, NULL, type, word);
+                if (r < 0)
+                        return r;
+        }
+
+        return 0;
+}
+
+int manager_parse_fallback_string(Manager *m, const char *string) {
+        if (m->have_fallbacks)
+                return 0;
+
+        return manager_parse_server_string(m, SERVER_FALLBACK, string);
+}
+
+int config_parse_servers(
+                const char *unit,
+                const char *filename,
+                unsigned line,
+                const char *section,
+                unsigned section_line,
+                const char *lvalue,
+                int ltype,
+                const char *rvalue,
+                void *data,
+                void *userdata) {
+
+        Manager *m = userdata;
+        int r;
+
+        assert(filename);
+        assert(lvalue);
+        assert(rvalue);
+
+        if (isempty(rvalue))
+                manager_flush_server_names(m, ltype);
+        else {
+                r = manager_parse_server_string(m, ltype, rvalue);
+                if (r < 0) {
+                        log_syntax(unit, LOG_WARNING, filename, line, r,
+                                   "Failed to parse NTP server string '%s', ignoring: %m", rvalue);
+                        return 0;
+                }
+        }
+
+        return 0;
+}
+
+int manager_parse_config_file(Manager *m) {
+        int r;
+
+        assert(m);
+
+        r = config_parse_config_file("timesyncd.conf", "Time\0",
+                                     config_item_perf_lookup, timesyncd_gperf_lookup,
+                                     CONFIG_PARSE_WARN, m);
+        if (r < 0)
+                return r;
+
+        if (m->poll_interval_min_usec < 16 * USEC_PER_SEC) {
+                log_warning("Invalid PollIntervalMinSec=. Using default value.");
+                m->poll_interval_min_usec = NTP_POLL_INTERVAL_MIN_USEC;
+        }
+
+        if (m->poll_interval_max_usec < m->poll_interval_min_usec) {
+                log_warning("PollIntervalMaxSec= is smaller than PollIntervalMinSec=. Using default value.");
+                m->poll_interval_max_usec = MAX(NTP_POLL_INTERVAL_MAX_USEC, m->poll_interval_min_usec * 32);
+        }
+
+        if (m->connection_retry_usec < 1 * USEC_PER_SEC) {
+                log_warning("Invalid ConnectionRetrySec=. Using default value.");
+                m->connection_retry_usec = DEFAULT_CONNECTION_RETRY_USEC;
+        }
+
+        return r;
+}
diff --git a/src/timesync/timesyncd-conf.h b/src/timesync/timesyncd-conf.h
new file mode 100644
index 0000000..d6b9060
--- /dev/null
+++ b/src/timesync/timesyncd-conf.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include "conf-parser.h"
+#include "timesyncd-manager.h"
+
+const struct ConfigPerfItem* timesyncd_gperf_lookup(const char *key, GPERF_LEN_TYPE length);
+
+int manager_parse_server_string(Manager *m, ServerType type, const char *string);
+
+CONFIG_PARSER_PROTOTYPE(config_parse_servers);
+
+int manager_parse_config_file(Manager *m);
+int manager_parse_fallback_string(Manager *m, const char *string);
diff --git a/src/timesync/timesyncd-gperf.gperf b/src/timesync/timesyncd-gperf.gperf
new file mode 100644
index 0000000..731dea1
--- /dev/null
+++ b/src/timesync/timesyncd-gperf.gperf
@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+%{
+#if __GNUC__ >= 7
+_Pragma("GCC diagnostic ignored \"-Wimplicit-fallthrough\"")
+#endif
+#include <stddef.h>
+#include "conf-parser.h"
+#include "timesyncd-conf.h"
+%}
+struct ConfigPerfItem;
+%null_strings
+%language=ANSI-C
+%define slot-name section_and_lvalue
+%define hash-function-name timesyncd_gperf_hash
+%define lookup-function-name timesyncd_gperf_lookup
+%readonly-tables
+%omit-struct-type
+%struct-type
+%includes
+%%
+Time.NTP,                            config_parse_servers, SERVER_SYSTEM,   0
+Time.Servers,                        config_parse_servers, SERVER_SYSTEM,   0
+Time.FallbackNTP,                    config_parse_servers, SERVER_FALLBACK, 0
+Time.RootDistanceMaxSec,             config_parse_sec,     0,               offsetof(Manager, root_distance_max_usec)
+Time.PollIntervalMinSec,             config_parse_sec,     0,               offsetof(Manager, poll_interval_min_usec)
+Time.PollIntervalMaxSec,             config_parse_sec,     0,               offsetof(Manager, poll_interval_max_usec)
+Time.ConnectionRetrySec,             config_parse_sec,     0,               offsetof(Manager, connection_retry_usec)
+Time.SaveIntervalSec,                config_parse_sec,     0,               offsetof(Manager, save_time_interval_usec)
diff --git a/src/timesync/timesyncd-manager.c b/src/timesync/timesyncd-manager.c
new file mode 100644
index 0000000..1998ba9
--- /dev/null
+++ b/src/timesync/timesyncd-manager.c
@@ -0,0 +1,1287 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <math.h>
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <resolv.h>
+#include <stdlib.h>
+#include <sys/timerfd.h>
+#include <sys/timex.h>
+#include <sys/types.h>
+
+#include "sd-daemon.h"
+#include "sd-messages.h"
+
+#include "alloc-util.h"
+#include "bus-polkit.h"
+#include "common-signal.h"
+#include "dns-domain.h"
+#include "event-util.h"
+#include "fd-util.h"
+#include "format-util.h"
+#include "fs-util.h"
+#include "list.h"
+#include "log.h"
+#include "logarithm.h"
+#include "network-util.h"
+#include "ratelimit.h"
+#include "resolve-private.h"
+#include "random-util.h"
+#include "socket-util.h"
+#include "string-util.h"
+#include "strv.h"
+#include "time-util.h"
+#include "timesyncd-conf.h"
+#include "timesyncd-manager.h"
+#include "user-util.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
+
+/*
+ * Maximum delta in seconds which the system clock is gradually adjusted
+ * (slewed) 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
+
+/* Default of maximum acceptable root distance in microseconds. */
+#define NTP_ROOT_DISTANCE_MAX_USEC      (5 * USEC_PER_SEC)
+
+/* Maximum number of missed replies before selecting another source. */
+#define NTP_MAX_MISSED_REPLIES          2
+
+#define RATELIMIT_INTERVAL_USEC (10*USEC_PER_SEC)
+#define RATELIMIT_BURST 10
+
+#define TIMEOUT_USEC (10*USEC_PER_SEC)
+
+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 int manager_save_time_and_rearm(Manager *m, usec_t t);
+
+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 = ASSERT_PTR(userdata);
+
+        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) {
+                log_warning_errno(r, "Failed to set up connection socket: %m");
+                return manager_connect(m);
+        }
+
+        /*
+         * Generate a random number as transmit timestamp, to ensure we get
+         * a full 64 bits of entropy to make it hard for off-path attackers
+         * to inject random time to us.
+         */
+        random_bytes(&m->request_nonce, sizeof(m->request_nonce));
+        ntpmsg.trans_time = m->request_nonce;
+
+        server_address_pretty(m->current_server_address, &pretty);
+
+        /*
+         * Record the transmit timestamp. This should be as close as possible to
+         * the send-to to ensure the timestamp is reasonably accurate
+         */
+        assert_se(clock_gettime(CLOCK_BOOTTIME, &m->trans_time_mon) >= 0);
+        assert_se(clock_gettime(CLOCK_REALTIME, &m->trans_time) >= 0);
+
+        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)
+                m->retry_interval = NTP_RETRY_INTERVAL_MIN_USEC;
+        else
+                m->retry_interval = MIN(m->retry_interval * 4/3, NTP_RETRY_INTERVAL_MAX_USEC);
+
+        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,
+                                now(CLOCK_BOOTTIME) + 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 = ASSERT_PTR(userdata);
+
+        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_relative(m->event_timer, next);
+                if (r < 0)
+                        return r;
+
+                return sd_event_source_set_enabled(m->event_timer, SD_EVENT_ONESHOT);
+        }
+
+        return sd_event_add_time_relative(
+                        m->event,
+                        &m->event_timer,
+                        CLOCK_BOOTTIME,
+                        next, 0,
+                        manager_timer, m);
+}
+
+static int manager_clock_watch(sd_event_source *source, int fd, uint32_t revents, void *userdata) {
+        Manager *m = ASSERT_PTR(userdata);
+
+        /* 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) {
+        int r;
+
+        assert(m);
+
+        m->event_clock_watch = sd_event_source_disable_unref(m->event_clock_watch);
+
+        r = event_add_time_change(m->event, &m->event_clock_watch, 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;
+
+        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 = (struct timex) {
+                        .modes = ADJ_STATUS | ADJ_NANO | ADJ_OFFSET | ADJ_TIMECONST | ADJ_MAXERROR | ADJ_ESTERROR,
+                        .status = STA_PLL,
+                        .offset = offset * NSEC_PER_SEC,
+                        .constant = log2i(m->poll_interval_usec / USEC_PER_SEC) - 4,
+                };
+
+                log_debug("  adjust (slew): %+.3f sec", offset);
+        } else {
+                tmx = (struct timex) {
+                        .modes = ADJ_STATUS | ADJ_NANO | ADJ_SETOFFSET | ADJ_MAXERROR | ADJ_ESTERROR,
+
+                        /* ADJ_NANO uses nanoseconds in the microseconds field */
+                        .time.tv_sec = (long)offset,
+                        .time.tv_usec = (offset - (double) (long) offset) * 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;
+        }
+
+        if (clock_adjtime(CLOCK_REALTIME, &tmx) < 0)
+                return -errno;
+
+        m->drift_freq = tmx.freq;
+
+        log_debug("  status       : %04i %s\n"
+                  "  time now     : %"PRI_TIME".%03"PRI_USEC"\n"
+                  "  constant     : %"PRI_TIMEX"\n"
+                  "  offset       : %+.3f sec\n"
+                  "  freq offset  : %+"PRI_TIMEX" (%+"PRI_TIMEX" ppm)\n",
+                  tmx.status, tmx.status & STA_UNSYNC ? "unsync" : "sync",
+                  tmx.time.tv_sec, tmx.time.tv_usec / NSEC_PER_MSEC,
+                  tmx.constant,
+                  (double)tmx.offset / NSEC_PER_SEC,
+                  tmx.freq, tmx.freq / 65536);
+
+        return 0;
+}
+
+static bool manager_sample_spike_detection(Manager *m, double offset, double delay) {
+        unsigned 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 = m->poll_interval_min_usec;
+                m->poll_resync = false;
+                return;
+        }
+
+        /* set to minimal poll interval */
+        if (!spike && fabs(offset) > NTP_ACCURACY_SEC) {
+                m->poll_interval_usec = m->poll_interval_min_usec;
+                return;
+        }
+
+        /* increase polling interval */
+        if (fabs(offset) < NTP_ACCURACY_SEC * 0.25) {
+                if (m->poll_interval_usec < m->poll_interval_max_usec)
+                        m->poll_interval_usec *= 2;
+                return;
+        }
+
+        /* decrease polling interval */
+        if (spike || fabs(offset) > NTP_ACCURACY_SEC * 0.75) {
+                if (m->poll_interval_usec > m->poll_interval_min_usec)
+                        m->poll_interval_usec /= 2;
+                return;
+        }
+}
+
+static int manager_receive_response(sd_event_source *source, int fd, uint32_t revents, void *userdata) {
+        Manager *m = ASSERT_PTR(userdata);
+        struct ntp_msg ntpmsg;
+
+        struct iovec iov = {
+                .iov_base = &ntpmsg,
+                .iov_len = sizeof(ntpmsg),
+        };
+        /* This needs to be initialized with zero. See #20741. */
+        CMSG_BUFFER_TYPE(CMSG_SPACE_TIMESPEC) 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 timespec *recv_time;
+        triple_timestamp dts;
+        ssize_t len;
+        double origin, receive, trans, dest, delay, offset, root_distance;
+        bool spike;
+        int leap_sec, r;
+
+        assert(source);
+
+        if (revents & (EPOLLHUP|EPOLLERR)) {
+                log_warning("Server connection returned error.");
+                return manager_connect(m);
+        }
+
+        len = recvmsg_safe(fd, &msghdr, MSG_DONTWAIT);
+        if (len == -EAGAIN)
+                return 0;
+        if (len < 0) {
+                log_warning_errno(len, "Error receiving message, disconnecting: %m");
+                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 = CMSG_FIND_AND_COPY_DATA(&msghdr, SOL_SOCKET, SCM_TIMESTAMPNS, struct timespec);
+        if (!recv_time)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Packet timestamp missing.");
+
+        if (!m->pending) {
+                log_debug("Unexpected reply. Ignoring.");
+                return 0;
+        }
+
+        m->missed_replies = 0;
+
+        /* check the transmit request nonce was properly returned in the origin_time field */
+        if (ntpmsg.origin_time.sec != m->request_nonce.sec || ntpmsg.origin_time.frac != m->request_nonce.frac) {
+                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 > (double) m->root_distance_max_usec / (double) USEC_PER_SEC) {
+                log_info("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         : %i\n"
+                  "  version      : %i\n"
+                  "  mode         : %i\n"
+                  "  stratum      : %u\n"
+                  "  precision    : %.6f sec (%i)\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);
+
+        /* Get current monotonic/realtime clocks immediately before adjusting the latter */
+        triple_timestamp_now(&dts);
+
+        if (!spike) {
+                /* Fix up our idea of the time. */
+                dts.realtime = (usec_t) (dts.realtime + offset * USEC_PER_SEC);
+
+                r = manager_adjust_clock(m, offset, leap_sec);
+                if (r < 0)
+                        log_error_errno(r, "Failed to call clock_adjtime(): %m");
+
+                (void) manager_save_time_and_rearm(m, dts.realtime);
+
+                /* If touch fails, there isn't much we can do. Maybe it'll work next time. */
+                r = touch("/run/systemd/timesync/synchronized");
+                if (r < 0)
+                        log_debug_errno(r, "Failed to touch /run/systemd/timesync/synchronized, ignoring: %m");
+        }
+
+        /* Save NTP response */
+        m->ntpmsg = ntpmsg;
+        m->origin_time = m->trans_time;
+        m->dest_time = *recv_time;
+        m->spike = spike;
+
+        log_debug("interval/delta/delay/jitter/drift " USEC_FMT "s/%+.3fs/%.3fs/%.3fs/%+"PRIi64"ppm%s",
+                  m->poll_interval_usec / USEC_PER_SEC, offset, delay, m->samples_jitter, m->drift_freq / 65536,
+                  spike ? " (ignored)" : "");
+
+        if (sd_bus_is_ready(m->bus) > 0)
+                (void) sd_bus_emit_properties_changed(
+                                m->bus,
+                                "/org/freedesktop/timesync1",
+                                "org.freedesktop.timesync1.Manager",
+                                "NTPMessage",
+                                NULL);
+
+        if (!m->talking) {
+                _cleanup_free_ char *pretty = NULL;
+
+                m->talking = true;
+
+                (void) server_address_pretty(m->current_server_address, &pretty);
+
+                log_info("Contacted time server %s (%s).", strna(pretty), m->current_server_name->string);
+                (void) sd_notifyf(false, "STATUS=Contacted time server %s (%s).", strna(pretty), m->current_server_name->string);
+        }
+
+        if (!spike && !m->synchronized) {
+                m->synchronized = true;
+
+                log_struct(LOG_INFO,
+                           LOG_MESSAGE("Initial clock synchronization to %s.",
+                                       FORMAT_TIMESTAMP_STYLE(dts.realtime, TIMESTAMP_US)),
+                           "MESSAGE_ID=" SD_MESSAGE_TIME_SYNC_STR,
+                           "MONOTONIC_USEC=" USEC_FMT, dts.monotonic,
+                           "REALTIME_USEC=" USEC_FMT, dts.realtime,
+                           "BOOTTIME_USEC=" USEC_FMT, dts.boottime);
+        }
+
+        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 = {};
+        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_int(m->server_socket, SOL_SOCKET, SO_TIMESTAMPNS, true);
+        if (r < 0)
+                return r;
+
+        (void) socket_set_option(m->server_socket, addr.sa.sa_family, IP_TOS, IPV6_TCLASS, IPTOS_DSCP_EF);
+
+        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->talking = false;
+        m->missed_replies = NTP_MAX_MISSED_REPLIES;
+        if (m->poll_interval_usec == 0)
+                m->poll_interval_usec = m->poll_interval_min_usec;
+
+        server_address_pretty(m->current_server_address, &pretty);
+        log_debug("Connecting to time server %s (%s).", strna(pretty), m->current_server_name->string);
+        (void) 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, Manager *m) {
+        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_debug("Ignoring 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 = ASSERT_PTR(userdata);
+
+        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_below(&m->ratelimit)) {
+                log_debug("Delaying attempts to contact servers.");
+
+                r = sd_event_add_time_relative(m->event, &m->event_retry, CLOCK_BOOTTIME, m->connection_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 {
+                /* 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 runtime list, then the system list,
+                         * then the link list. After having processed the link list we jump back to the system list
+                         * if no runtime server list.
+                         * However, if all lists are empty, we change to the fallback list. */
+                        if (!m->current_server_name || m->current_server_name->type == SERVER_LINK) {
+                                f = m->runtime_servers;
+                                if (!f)
+                                        f = m->system_servers;
+                                if (!f)
+                                        f = m->link_servers;
+                        } else {
+                                f = m->link_servers;
+                                if (f)
+                                        restart = false;
+                                else {
+                                        f = m->runtime_servers;
+                                        if (!f)
+                                                f = m->system_servers;
+                                }
+                        }
+
+                        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 > 0) {
+                                log_debug("Waiting after exhausting servers.");
+                                r = sd_event_add_time_relative(m->event, &m->event_retry, CLOCK_BOOTTIME, 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 < m->poll_interval_max_usec)
+                                        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);
+
+                struct addrinfo hints = {
+                        .ai_flags = AI_NUMERICSERV|AI_ADDRCONFIG,
+                        .ai_socktype = SOCK_DGRAM,
+                        .ai_family = socket_ipv6_is_supported() ? AF_UNSPEC : AF_INET,
+                };
+
+                r = resolve_getaddrinfo(m->resolve, &m->resolve_query, m->current_server_name->string, "123", &hints, manager_resolve_handler, NULL, 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_disable_unref(m->event_clock_watch);
+
+        m->event_timeout = sd_event_source_unref(m->event_timeout);
+
+        (void) sd_notify(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);
+
+        if (t == SERVER_RUNTIME)
+                manager_flush_runtime_servers(m);
+}
+
+void manager_flush_runtime_servers(Manager *m) {
+        assert(m);
+
+        while (m->runtime_servers)
+                server_name_free(m->runtime_servers);
+}
+
+Manager* manager_free(Manager *m) {
+        if (!m)
+                return NULL;
+
+        manager_disconnect(m);
+        manager_flush_server_names(m, SERVER_SYSTEM);
+        manager_flush_server_names(m, SERVER_LINK);
+        manager_flush_server_names(m, SERVER_RUNTIME);
+        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_event_source_unref(m->event_save_time);
+
+        sd_event_source_unref(m->deferred_ntp_server_event_source);
+
+        sd_resolve_unref(m->resolve);
+        sd_event_unref(m->event);
+
+        sd_bus_flush_close_unref(m->bus);
+
+        bus_verify_polkit_async_registry_free(m->polkit_registry);
+
+        return mfree(m);
+}
+
+static int manager_network_read_link_servers(Manager *m) {
+        _cleanup_strv_free_ char **ntp = NULL;
+        bool changed = false;
+        int r;
+
+        assert(m);
+
+        r = sd_network_get_ntp(&ntp);
+        if (r < 0 && r != -ENODATA) {
+                if (r == -ENOMEM)
+                        log_oom();
+                else
+                        log_debug_errno(r, "Failed to get link NTP servers: %m");
+                goto clear;
+        }
+
+        LIST_FOREACH(names, n, m->link_servers)
+                n->marked = true;
+
+        STRV_FOREACH(i, ntp) {
+                bool found = false;
+
+                r = dns_name_is_valid_or_address(*i);
+                if (r < 0) {
+                        log_error_errno(r, "Failed to check validity of NTP server name or address '%s': %m", *i);
+                        goto clear;
+                } else if (r == 0) {
+                        log_error("Invalid NTP server name or address, ignoring: %s", *i);
+                        continue;
+                }
+
+                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) {
+                                log_oom();
+                                goto clear;
+                        }
+
+                        changed = true;
+                }
+        }
+
+        LIST_FOREACH(names, n, m->link_servers)
+                if (n->marked) {
+                        server_name_free(n);
+                        changed = true;
+                }
+
+        return changed;
+
+clear:
+        manager_flush_server_names(m, SERVER_LINK);
+        return r;
+}
+
+bool manager_is_connected(Manager *m) {
+        assert(m);
+
+        /* Return true when the manager is sending a request, resolving a server name, or
+         * in a poll interval. */
+        return m->server_socket >= 0 || m->resolve_query || m->event_timer;
+}
+
+static int manager_network_event_handler(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
+        Manager *m = ASSERT_PTR(userdata);
+        bool changed, connected, online;
+        int r;
+
+        sd_network_monitor_flush(m->network_monitor);
+
+        /* When manager_network_read_link_servers() failed, we assume that the servers are changed. */
+        changed = manager_network_read_link_servers(m);
+
+        /* check if the machine is online */
+        online = network_is_online();
+
+        /* check if the client is currently connected */
+        connected = manager_is_connected(m);
+
+        if (connected && !online) {
+                log_info("No network connectivity, watching for changes.");
+                manager_disconnect(m);
+
+        } else if ((!connected || changed) && 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 == -ENOENT) {
+                log_info("systemd does not appear to be running, not listening for systemd-networkd events.");
+                return 0;
+        }
+        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 = new(Manager, 1);
+        if (!m)
+                return -ENOMEM;
+
+        *m = (Manager) {
+                .root_distance_max_usec = NTP_ROOT_DISTANCE_MAX_USEC,
+                .poll_interval_min_usec = NTP_POLL_INTERVAL_MIN_USEC,
+                .poll_interval_max_usec = NTP_POLL_INTERVAL_MAX_USEC,
+
+                .connection_retry_usec = DEFAULT_CONNECTION_RETRY_USEC,
+
+                .server_socket = -EBADF,
+
+                .ratelimit = (const RateLimit) {
+                        RATELIMIT_INTERVAL_USEC,
+                        RATELIMIT_BURST
+                },
+
+                .save_time_interval_usec = DEFAULT_SAVE_TIME_INTERVAL_USEC,
+        };
+
+        r = sd_event_default(&m->event);
+        if (r < 0)
+                return r;
+
+        (void) sd_event_add_signal(m->event, NULL, SIGTERM, NULL,  NULL);
+        (void) sd_event_add_signal(m->event, NULL, SIGINT, NULL, NULL);
+        (void) sd_event_add_signal(m->event, NULL, SIGRTMIN+18, sigrtmin18_handler, NULL);
+
+        r = sd_event_add_memory_pressure(m->event, NULL, NULL, NULL);
+        if (r < 0)
+                log_debug_errno(r, "Failed allocate memory pressure event source, ignoring: %m");
+
+        (void) sd_event_set_watchdog(m->event, true);
+
+        /* Load previous synchronization state */
+        r = access("/run/systemd/timesync/synchronized", F_OK);
+        if (r < 0 && errno != ENOENT)
+                log_debug_errno(errno, "Failed to determine whether /run/systemd/timesync/synchronized exists, ignoring: %m");
+        m->synchronized = r >= 0;
+
+        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;
+
+        (void) manager_network_read_link_servers(m);
+
+        *ret = TAKE_PTR(m);
+
+        return 0;
+}
+
+static int manager_save_time_handler(sd_event_source *s, uint64_t usec, void *userdata) {
+        Manager *m = ASSERT_PTR(userdata);
+
+        (void) manager_save_time_and_rearm(m, USEC_INFINITY);
+        return 0;
+}
+
+int manager_setup_save_time_event(Manager *m) {
+        int r;
+
+        assert(m);
+        assert(!m->event_save_time);
+
+        if (m->save_time_interval_usec == USEC_INFINITY)
+                return 0;
+
+        /* NB: we'll accumulate scheduling latencies here, but this doesn't matter */
+        r = sd_event_add_time_relative(
+                        m->event, &m->event_save_time,
+                        CLOCK_BOOTTIME,
+                        m->save_time_interval_usec,
+                        10 * USEC_PER_SEC,
+                        manager_save_time_handler, m);
+        if (r < 0)
+                return log_error_errno(r, "Failed to add save time event: %m");
+
+        (void) sd_event_source_set_description(m->event_save_time, "save-time");
+
+        return 0;
+}
+
+static int manager_save_time_and_rearm(Manager *m, usec_t t) {
+        int r;
+
+        assert(m);
+
+        /* Updates the timestamp file to the specified time. If 't' is USEC_INFINITY uses the current system
+         * clock, but otherwise uses the specified timestamp. Note that whenever we acquire an NTP sync the
+         * specified timestamp value might be more accurate than the system clock, since the latter is
+         * subject to slow adjustments. */
+        r = touch_file(CLOCK_FILE, false, t, UID_INVALID, GID_INVALID, MODE_INVALID);
+        if (r < 0)
+                log_debug_errno(r, "Failed to update " CLOCK_FILE ", ignoring: %m");
+
+        m->save_on_exit = true;
+
+        if (m->save_time_interval_usec != USEC_INFINITY) {
+                r = sd_event_source_set_time_relative(m->event_save_time, m->save_time_interval_usec);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to rearm save time event: %m");
+
+                r = sd_event_source_set_enabled(m->event_save_time, SD_EVENT_ONESHOT);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to enable save time event: %m");
+        }
+
+        return 0;
+}
+
+static const char* ntp_server_property_name[_SERVER_TYPE_MAX] = {
+        [SERVER_SYSTEM]   = "SystemNTPServers",
+        [SERVER_FALLBACK] = "FallbackNTPServers",
+        [SERVER_LINK]     = "LinkNTPServers",
+        [SERVER_RUNTIME]  = "RuntimeNTPServers",
+};
+
+static int ntp_server_emit_changed_strv(Manager *manager, char **properties) {
+        assert(manager);
+        assert(properties);
+
+        if (sd_bus_is_ready(manager->bus) <= 0)
+                return 0;
+
+        return sd_bus_emit_properties_changed_strv(
+                        manager->bus,
+                        "/org/freedesktop/timesync1",
+                        "org.freedesktop.timesync1.Manager",
+                        properties);
+}
+
+static int on_deferred_ntp_server(sd_event_source *s, void *userdata) {
+        int r;
+        _cleanup_strv_free_ char **p = NULL;
+        Manager *m = ASSERT_PTR(userdata);
+
+        m->deferred_ntp_server_event_source = sd_event_source_disable_unref(m->deferred_ntp_server_event_source);
+
+        for (int type = SERVER_SYSTEM; type < _SERVER_TYPE_MAX; type++)
+                if (m->ntp_server_change_mask & (1U << type))
+                        if (strv_extend(&p, ntp_server_property_name[type]) < 0)
+                                log_oom();
+
+        m->ntp_server_change_mask = 0;
+
+        if (strv_isempty(p))
+                return log_error_errno(SYNTHETIC_ERRNO(ENOMEM), "Failed to build ntp server event strv!");
+
+        r = ntp_server_emit_changed_strv(m, p);
+        if (r < 0)
+                log_warning_errno(r, "Could not emit ntp server changed properties, ignoring: %m");
+
+        return 0;
+}
+
+int bus_manager_emit_ntp_server_changed(Manager *m) {
+        int r;
+
+        assert(m);
+
+        if (m->deferred_ntp_server_event_source)
+                return 0;
+
+        if (!m->event)
+                return 0;
+
+        if (IN_SET(sd_event_get_state(m->event), SD_EVENT_FINISHED, SD_EVENT_EXITING))
+                return 0;
+
+        r = sd_event_add_defer(m->event, &m->deferred_ntp_server_event_source, on_deferred_ntp_server, m);
+        if (r < 0)
+                return log_error_errno(r, "Failed to allocate ntp server event source: %m");
+
+        (void) sd_event_source_set_description(m->deferred_ntp_server_event_source, "deferred-ntp-server");
+
+        return 1;
+}
diff --git a/src/timesync/timesyncd-manager.h b/src/timesync/timesyncd-manager.h
new file mode 100644
index 0000000..f444787
--- /dev/null
+++ b/src/timesync/timesyncd-manager.h
@@ -0,0 +1,142 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include <sys/timex.h>
+
+#include "sd-bus.h"
+#include "sd-event.h"
+#include "sd-network.h"
+#include "sd-resolve.h"
+
+#include "hashmap.h"
+#include "list.h"
+#include "ratelimit.h"
+#include "time-util.h"
+#include "timesyncd-ntp-message.h"
+
+typedef struct Manager Manager;
+
+#include "timesyncd-server.h"
+
+/*
+ * "A client MUST NOT under any conditions use a poll interval less
+ * than 15 seconds."
+ */
+#define NTP_POLL_INTERVAL_MIN_USEC      (32 * USEC_PER_SEC)
+#define NTP_POLL_INTERVAL_MAX_USEC      (2048 * USEC_PER_SEC)
+
+#define NTP_RETRY_INTERVAL_MIN_USEC     (15 * USEC_PER_SEC)
+#define NTP_RETRY_INTERVAL_MAX_USEC     (6 * 60 * USEC_PER_SEC) /* 6 minutes */
+
+#define DEFAULT_CONNECTION_RETRY_USEC   (30 * USEC_PER_SEC)
+
+#define DEFAULT_SAVE_TIME_INTERVAL_USEC (60 * USEC_PER_SEC)
+
+#define STATE_DIR   "/var/lib/systemd/timesync"
+#define CLOCK_FILE  STATE_DIR "/clock"
+
+struct Manager {
+        sd_bus *bus;
+        sd_event *event;
+        sd_resolve *resolve;
+
+        LIST_HEAD(ServerName, system_servers);
+        LIST_HEAD(ServerName, link_servers);
+        LIST_HEAD(ServerName, runtime_servers);
+        LIST_HEAD(ServerName, fallback_servers);
+
+        bool have_fallbacks:1;
+
+        RateLimit ratelimit;
+        bool exhausted_servers;
+
+        /* network */
+        sd_event_source *network_event_source;
+        sd_network_monitor *network_monitor;
+
+        /* peer */
+        sd_resolve_query *resolve_query;
+        sd_event_source *event_receive;
+        ServerName *current_server_name;
+        ServerAddress *current_server_address;
+        int server_socket;
+        int missed_replies;
+        uint64_t packet_count;
+        sd_event_source *event_timeout;
+        bool talking;
+
+        /* PolicyKit */
+        Hashmap *polkit_registry;
+
+        /* last sent packet */
+        struct timespec trans_time_mon;
+        struct timespec trans_time;
+        struct ntp_ts request_nonce;
+        usec_t retry_interval;
+        usec_t connection_retry_usec;
+        bool pending;
+
+        /* poll timer */
+        sd_event_source *event_timer;
+        usec_t poll_interval_usec;
+        usec_t poll_interval_min_usec;
+        usec_t poll_interval_max_usec;
+        bool poll_resync;
+
+        /* history data */
+        struct {
+                double offset;
+                double delay;
+        } samples[8];
+        unsigned samples_idx;
+        double samples_jitter;
+        usec_t root_distance_max_usec;
+
+        /* last change */
+        bool jumped;
+        int64_t drift_freq;
+
+        /* watch for time changes */
+        sd_event_source *event_clock_watch;
+
+        /* Retry connections */
+        sd_event_source *event_retry;
+
+        /* RTC runs in local time, leave it alone */
+        bool rtc_local_time;
+
+        /* NTP response */
+        struct ntp_msg ntpmsg;
+        struct timespec origin_time, dest_time;
+        bool spike;
+
+        /* Indicates whether we ever managed to set the local clock from NTP */
+        bool synchronized;
+
+        /* save time event */
+        sd_event_source *event_save_time;
+        usec_t save_time_interval_usec;
+        bool save_on_exit;
+
+        /* Used to coalesce bus PropertiesChanged events */
+        sd_event_source *deferred_ntp_server_event_source;
+        unsigned ntp_server_change_mask;
+};
+
+int manager_new(Manager **ret);
+Manager* manager_free(Manager *m);
+
+DEFINE_TRIVIAL_CLEANUP_FUNC(Manager*, manager_free);
+
+void manager_set_server_name(Manager *m, ServerName *n);
+void manager_set_server_address(Manager *m, ServerAddress *a);
+void manager_flush_server_names(Manager *m, ServerType t);
+void manager_flush_runtime_servers(Manager *m);
+
+int manager_connect(Manager *m);
+void manager_disconnect(Manager *m);
+bool manager_is_connected(Manager *m);
+
+int manager_setup_save_time_event(Manager *m);
+
+int bus_manager_emit_ntp_server_changed(Manager *m);
diff --git a/src/timesync/timesyncd-ntp-message.h b/src/timesync/timesyncd-ntp-message.h
new file mode 100644
index 0000000..76ed9ec
--- /dev/null
+++ b/src/timesync/timesyncd-ntp-message.h
@@ -0,0 +1,45 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include "sparse-endian.h"
+
+/* 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        UINT64_C(2208988800)
+
+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_;
diff --git a/src/timesync/timesyncd-server.c b/src/timesync/timesyncd-server.c
new file mode 100644
index 0000000..0f68203
--- /dev/null
+++ b/src/timesync/timesyncd-server.c
@@ -0,0 +1,177 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "alloc-util.h"
+#include "string-table.h"
+#include "timesyncd-server.h"
+
+static const char * const server_type_table[_SERVER_TYPE_MAX] = {
+        [SERVER_SYSTEM]   = "system",
+        [SERVER_FALLBACK] = "fallback",
+        [SERVER_LINK]     = "link",
+        [SERVER_RUNTIME]  = "runtime",
+};
+
+DEFINE_PRIVATE_STRING_TABLE_LOOKUP_TO_STRING(server_type, ServerType);
+
+int server_address_new(
+                ServerName *n,
+                ServerAddress **ret,
+                const union sockaddr_union *sockaddr,
+                socklen_t socklen) {
+
+        ServerAddress *a, *tail;
+
+        assert(n);
+        assert(sockaddr);
+        assert(socklen >= offsetof(struct sockaddr, sa_data));
+        assert(socklen <= sizeof(union sockaddr_union));
+
+        a = new(ServerAddress, 1);
+        if (!a)
+                return -ENOMEM;
+
+        *a = (ServerAddress) {
+                .name = n,
+                .socklen = socklen,
+        };
+
+        memcpy(&a->sockaddr, sockaddr, socklen);
+
+        tail = LIST_FIND_TAIL(addresses, n->addresses);
+        LIST_INSERT_AFTER(addresses, n->addresses, tail, a);
+
+        if (ret)
+                *ret = a;
+
+        return 0;
+}
+
+ServerAddress* server_address_free(ServerAddress *a) {
+        if (!a)
+                return NULL;
+
+        if (a->name) {
+                LIST_REMOVE(addresses, a->name->addresses, a);
+
+                if (a->name->manager && a->name->manager->current_server_address == a)
+                        manager_set_server_address(a->name->manager, NULL);
+        }
+
+        return mfree(a);
+}
+
+static int enable_ntp_server_defer_event(Manager *m, ServerType type) {
+        int r;
+
+        assert(m);
+        assert((type >= 0) && (type < _SERVER_TYPE_MAX));
+
+        m->ntp_server_change_mask |= 1U << type;
+
+        r = bus_manager_emit_ntp_server_changed(m);
+        if (r < 0)
+                return r;
+
+        return 1;
+}
+
+int server_name_new(
+                Manager *m,
+                ServerName **ret,
+                ServerType type,
+                const char *string) {
+        int r;
+        ServerName *n;
+
+        assert(m);
+        assert(string);
+
+        n = new(ServerName, 1);
+        if (!n)
+                return -ENOMEM;
+
+        *n = (ServerName) {
+                .manager = m,
+                .type = type,
+                .string = strdup(string),
+        };
+
+        if (!n->string) {
+                free(n);
+                return -ENOMEM;
+        }
+
+        switch (type) {
+        case SERVER_SYSTEM:
+                LIST_APPEND(names, m->system_servers, n);
+                break;
+        case SERVER_LINK:
+                LIST_APPEND(names, m->link_servers, n);
+                break;
+        case SERVER_FALLBACK:
+                LIST_APPEND(names, m->fallback_servers, n);
+                break;
+        case SERVER_RUNTIME:
+                LIST_APPEND(names, m->runtime_servers, n);
+                break;
+        default:
+                assert_not_reached();
+        }
+
+        r = enable_ntp_server_defer_event(m, type);
+        if (r < 0)
+                log_debug_errno(r, "Failed to enable ntp server defer event, ignoring: %m");
+
+        if (type != SERVER_FALLBACK &&
+            m->current_server_name &&
+            m->current_server_name->type == SERVER_FALLBACK)
+                manager_set_server_name(m, NULL);
+
+        log_debug("Added new %s server %s.", server_type_to_string(type), string);
+
+        if (ret)
+                *ret = n;
+
+        return 0;
+}
+
+ServerName *server_name_free(ServerName *n) {
+        int r;
+
+        if (!n)
+                return NULL;
+
+        server_name_flush_addresses(n);
+
+        if (n->manager) {
+                if (n->type == SERVER_SYSTEM)
+                        LIST_REMOVE(names, n->manager->system_servers, n);
+                else if (n->type == SERVER_LINK)
+                        LIST_REMOVE(names, n->manager->link_servers, n);
+                else if (n->type == SERVER_FALLBACK)
+                        LIST_REMOVE(names, n->manager->fallback_servers, n);
+                else if (n->type == SERVER_RUNTIME)
+                        LIST_REMOVE(names, n->manager->runtime_servers, n);
+                else
+                        assert_not_reached();
+
+                r = enable_ntp_server_defer_event(n->manager, n->type);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to enable ntp server defer event, ignoring: %m");
+
+                if (n->manager->current_server_name == n)
+                        manager_set_server_name(n->manager, NULL);
+        }
+
+        log_debug("Removed server %s.", n->string);
+
+        free(n->string);
+        return mfree(n);
+}
+
+void server_name_flush_addresses(ServerName *n) {
+        assert(n);
+
+        while (n->addresses)
+                server_address_free(n->addresses);
+}
diff --git a/src/timesync/timesyncd-server.h b/src/timesync/timesyncd-server.h
new file mode 100644
index 0000000..e22917a
--- /dev/null
+++ b/src/timesync/timesyncd-server.h
@@ -0,0 +1,50 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include "list.h"
+#include "socket-util.h"
+
+typedef struct ServerAddress ServerAddress;
+typedef struct ServerName ServerName;
+
+typedef enum ServerType {
+        SERVER_SYSTEM,
+        SERVER_FALLBACK,
+        SERVER_LINK,
+        SERVER_RUNTIME,
+        _SERVER_TYPE_MAX,
+        _SERVER_TYPE_INVALID = -EINVAL,
+} ServerType;
+
+#include "timesyncd-manager.h"
+
+struct ServerAddress {
+        ServerName *name;
+
+        union sockaddr_union sockaddr;
+        socklen_t socklen;
+
+        LIST_FIELDS(ServerAddress, addresses);
+};
+
+struct ServerName {
+        Manager *manager;
+
+        ServerType type;
+        char *string;
+
+        bool marked:1;
+
+        LIST_HEAD(ServerAddress, addresses);
+        LIST_FIELDS(ServerName, names);
+};
+
+int server_address_new(ServerName *n, ServerAddress **ret, const union sockaddr_union *sockaddr, socklen_t socklen);
+ServerAddress* server_address_free(ServerAddress *a);
+static inline int server_address_pretty(ServerAddress *a, char **pretty) {
+        return sockaddr_pretty(&a->sockaddr.sa, a->socklen, true, true, pretty);
+}
+
+int server_name_new(Manager *m, ServerName **ret, ServerType type,const char *string);
+ServerName *server_name_free(ServerName *n);
+void server_name_flush_addresses(ServerName *n);
diff --git a/src/timesync/timesyncd.c b/src/timesync/timesyncd.c
new file mode 100644
index 0000000..1d8ebec
--- /dev/null
+++ b/src/timesync/timesyncd.c
@@ -0,0 +1,231 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include "sd-daemon.h"
+#include "sd-event.h"
+#include "sd-messages.h"
+
+#include "capability-util.h"
+#include "clock-util.h"
+#include "daemon-util.h"
+#include "fd-util.h"
+#include "fs-util.h"
+#include "main-func.h"
+#include "mkdir-label.h"
+#include "network-util.h"
+#include "process-util.h"
+#include "signal-util.h"
+#include "timesyncd-bus.h"
+#include "timesyncd-conf.h"
+#include "timesyncd-manager.h"
+#include "user-util.h"
+
+static int advance_tstamp(int fd, const struct stat *st) {
+        assert_se(fd >= 0);
+        assert_se(st);
+
+        /* So here's the problem: whenever we read the timestamp we'd like to ensure the next time we won't
+         * restore the exact same time again, but one at least one step further (so that comparing mtimes of
+         * the timestamp file is a reliable check that timesync did its thing). But file systems have
+         * different timestamp accuracy: traditional fat has 2s granularity, and even ext2 and friends expose
+         * different granularity depending on selected inode size during formatting! Hence, to ensure the
+         * timestamp definitely is increased, here's what we'll do: we'll first try to increase the timestamp
+         * by 1μs, write that and read it back. If it was updated, great. But if it was not, we'll instead
+         * increase the timestamp by 10μs, and do the same, then 100μs, then 1ms, and so on, until it works,
+         * or we reach 10s. If it still didn't work then, the fs is just broken and we give up. */
+
+        usec_t target = MAX3(now(CLOCK_REALTIME),
+                             TIME_EPOCH * USEC_PER_SEC,
+                             timespec_load(&st->st_mtim));
+
+        for (usec_t a = 1; a <= 10 * USEC_PER_SEC; a *= 10) { /* 1μs, 10μs, 100μs, 1ms, … 10s */
+                struct timespec ts[2];
+                struct stat new_st;
+
+                /* Bump to the maximum of the old timestamp advanced by the specified unit,  */
+                usec_t c = usec_add(target, a);
+
+                timespec_store(&ts[0], c);
+                ts[1] = ts[0];
+
+                if (futimens(fd, ts) < 0) {
+                        /* If this doesn't work at all, log, don't fail but give up */
+                        log_warning_errno(errno, "Unable to update mtime of timestamp file, ignoring: %m");
+                        return 0;
+                }
+
+                if (fstat(fd, &new_st) < 0)
+                        return log_error_errno(errno, "Failed to stat timestamp file: %m");
+
+                if (timespec_load(&new_st.st_mtim) > target) {
+                        log_debug("Successfully bumped timestamp file.");
+                        return 1;
+                }
+
+                log_debug("Tried to advance timestamp file by " USEC_FMT ", but this didn't work, file system timestamp granularity too coarse?", a);
+        }
+
+        log_debug("Gave up trying to advance timestamp file.");
+        return 0;
+}
+
+static int load_clock_timestamp(uid_t uid, gid_t gid) {
+        usec_t min = TIME_EPOCH * USEC_PER_SEC, ct;
+        _cleanup_close_ int fd = -EBADF;
+        int r;
+
+        /* Let's try to make sure that the clock is always monotonically increasing, by saving the clock
+         * whenever we have a new NTP time, or when we shut down, and restoring it when we start again. This
+         * is particularly helpful on systems lacking a battery backed RTC. We also will adjust the time to
+         * at least the build time of systemd. */
+
+        fd = open(CLOCK_FILE, O_RDWR|O_CLOEXEC, 0644);
+        if (fd < 0) {
+                if (errno != ENOENT)
+                        log_debug_errno(errno, "Unable to open timestamp file '" CLOCK_FILE "', ignoring: %m");
+
+                r = mkdir_safe_label(STATE_DIR, 0755, uid, gid,
+                                     MKDIR_FOLLOW_SYMLINK | MKDIR_WARN_MODE);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to create state directory, ignoring: %m");
+
+                /* create stamp file with the compiled-in date */
+                r = touch_file(CLOCK_FILE, /* parents= */ false, min, uid, gid, 0644);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to create %s, ignoring: %m", CLOCK_FILE);
+        } else {
+                struct stat st;
+                usec_t stamp;
+
+                /* check if the recorded time is later than the compiled-in one */
+                if (fstat(fd, &st) < 0)
+                        return log_error_errno(errno, "Unable to stat timestamp file '" CLOCK_FILE "': %m");
+
+                stamp = timespec_load(&st.st_mtim);
+                if (stamp > min)
+                        min = stamp;
+
+                /* Try to fix the access mode, so that we can still touch the file after dropping
+                 * privileges */
+                r = fchmod_and_chown(fd, 0644, uid, gid);
+                if (r < 0)
+                        log_full_errno(ERRNO_IS_PRIVILEGE(r) ? LOG_DEBUG : LOG_WARNING, r,
+                                       "Failed to chmod or chown %s, ignoring: %m", CLOCK_FILE);
+
+                (void) advance_tstamp(fd, &st);
+        }
+
+        ct = now(CLOCK_REALTIME);
+        if (ct > min)
+                return 0;
+
+        /* Not that it matters much, but we actually restore the clock to n+1 here rather than n, simply
+         * because we read n as time previously already and we want to progress here, i.e. not report the
+         * same time again. */
+        if (clock_settime(CLOCK_REALTIME, TIMESPEC_STORE(min+1)) < 0) {
+                log_warning_errno(errno, "Failed to restore system clock, ignoring: %m");
+                return 0;
+        }
+
+        log_struct(LOG_INFO,
+                   "MESSAGE_ID=" SD_MESSAGE_TIME_BUMP_STR,
+                   "REALTIME_USEC=" USEC_FMT, min+1,
+                   LOG_MESSAGE("System clock time unset or jumped backwards, restored from recorded timestamp: %s",
+                               FORMAT_TIMESTAMP(min+1)));
+        return 0;
+}
+
+static int run(int argc, char *argv[]) {
+        _cleanup_(manager_freep) Manager *m = NULL;
+        _unused_ _cleanup_(notify_on_cleanup) const char *notify_message = NULL;
+        const char *user = "systemd-timesync";
+        uid_t uid, uid_current;
+        gid_t gid;
+        int r;
+
+        log_set_facility(LOG_CRON);
+        log_setup();
+
+        umask(0022);
+
+        if (argc != 1)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "This program does not take arguments.");
+
+        uid = uid_current = geteuid();
+        gid = getegid();
+
+        if (uid_current == 0) {
+                r = get_user_creds(&user, &uid, &gid, NULL, NULL, 0);
+                if (r < 0)
+                        return log_error_errno(r, "Cannot resolve user name %s: %m", user);
+        }
+
+        r = load_clock_timestamp(uid, gid);
+        if (r < 0)
+                return r;
+
+        /* Drop privileges, but only if we have been started as root. If we are not running as root we assume all
+         * privileges are already dropped. */
+        if (uid_current == 0) {
+                r = drop_privileges(uid, gid, (1ULL << CAP_SYS_TIME));
+                if (r < 0)
+                        return log_error_errno(r, "Failed to drop privileges: %m");
+        }
+
+        assert_se(sigprocmask_many(SIG_BLOCK, NULL, SIGTERM, SIGINT, SIGRTMIN+18, -1) >= 0);
+
+        r = manager_new(&m);
+        if (r < 0)
+                return log_error_errno(r, "Failed to allocate manager: %m");
+
+        r = manager_connect_bus(m);
+        if (r < 0)
+                return log_error_errno(r, "Could not connect to bus: %m");
+
+        if (clock_is_localtime(NULL) > 0) {
+                log_info("The system is configured to read the RTC time in the local time zone. "
+                         "This mode cannot be fully supported. All system time to RTC updates are disabled.");
+                m->rtc_local_time = true;
+        }
+
+        r = manager_parse_config_file(m);
+        if (r < 0)
+                log_warning_errno(r, "Failed to parse configuration file: %m");
+
+        r = manager_parse_fallback_string(m, NTP_SERVERS);
+        if (r < 0)
+                return log_error_errno(r, "Failed to parse fallback server strings: %m");
+
+        log_debug("systemd-timesyncd running as pid " PID_FMT, getpid_cached());
+
+        notify_message = notify_start("READY=1\n"
+                                      "STATUS=Daemon is running",
+                                      NOTIFY_STOPPING);
+
+        r = manager_setup_save_time_event(m);
+        if (r < 0)
+                return r;
+
+        if (network_is_online()) {
+                r = manager_connect(m);
+                if (r < 0)
+                        return r;
+        }
+
+        r = sd_event_loop(m->event);
+        if (r < 0)
+                return log_error_errno(r, "Failed to run event loop: %m");
+
+        /* if we got an authoritative time, store it in the file system */
+        if (m->save_on_exit) {
+                r = touch(CLOCK_FILE);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to touch " CLOCK_FILE ", ignoring: %m");
+        }
+
+        return 0;
+}
+
+DEFINE_MAIN_FUNCTION(run);
diff --git a/src/timesync/timesyncd.conf.in b/src/timesync/timesyncd.conf.in
new file mode 100644
index 0000000..6ef41cf
--- /dev/null
+++ b/src/timesync/timesyncd.conf.in
@@ -0,0 +1,26 @@
+#  This file is part of systemd.
+#
+#  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.
+#
+# Entries in this file show the compile time defaults. Local configuration
+# should be created by either modifying this file (or a copy of it placed in
+# /etc/ if the original file is shipped in /usr/), or by creating "drop-ins" in
+# the /etc/systemd/timesyncd.conf.d/ directory. The latter is generally
+# recommended. Defaults can be restored by simply deleting the main
+# configuration file and all drop-ins located in /etc/.
+#
+# Use 'systemd-analyze cat-config systemd/timesyncd.conf' to display the full config.
+#
+# See timesyncd.conf(5) for details.
+
+[Time]
+#NTP=
+#FallbackNTP={{NTP_SERVERS}}
+#RootDistanceMaxSec=5
+#PollIntervalMinSec=32
+#PollIntervalMaxSec=2048
+#ConnectionRetrySec=30
+#SaveIntervalSec=60
diff --git a/src/timesync/wait-sync.c b/src/timesync/wait-sync.c
new file mode 100644
index 0000000..832e117
--- /dev/null
+++ b/src/timesync/wait-sync.c
@@ -0,0 +1,240 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/* systemd service to wait until kernel realtime clock is synchronized */
+
+#include <errno.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/inotify.h>
+#include <sys/timerfd.h>
+#include <sys/timex.h>
+#include <unistd.h>
+
+#include "sd-event.h"
+
+#include "fd-util.h"
+#include "inotify-util.h"
+#include "main-func.h"
+#include "signal-util.h"
+#include "time-util.h"
+
+typedef struct ClockState {
+        int timerfd_fd;                  /* non-negative is descriptor from timerfd_create */
+        int adjtime_state;               /* return value from last adjtimex(2) call */
+        sd_event_source *timerfd_event_source; /* non-null is the active io event source */
+        int inotify_fd;
+        sd_event_source *inotify_event_source;
+        int run_systemd_wd;
+        int run_systemd_timesync_wd;
+        bool has_watchfile;
+} ClockState;
+
+static void clock_state_release_timerfd(ClockState *sp) {
+        sp->timerfd_event_source = sd_event_source_unref(sp->timerfd_event_source);
+        sp->timerfd_fd = safe_close(sp->timerfd_fd);
+}
+
+static void clock_state_release(ClockState *sp) {
+        clock_state_release_timerfd(sp);
+        sp->inotify_event_source = sd_event_source_unref(sp->inotify_event_source);
+        sp->inotify_fd = safe_close(sp->inotify_fd);
+}
+
+static int clock_state_update(ClockState *sp, sd_event *event);
+
+static int update_notify_run_systemd_timesync(ClockState *sp) {
+        sp->run_systemd_timesync_wd = inotify_add_watch(sp->inotify_fd, "/run/systemd/timesync", IN_CREATE|IN_DELETE_SELF);
+        return sp->run_systemd_timesync_wd;
+}
+
+static int timerfd_handler(sd_event_source *s,
+                           int fd,
+                           uint32_t revents,
+                           void *userdata) {
+        ClockState *sp = userdata;
+
+        return clock_state_update(sp, sd_event_source_get_event(s));
+}
+
+static void process_inotify_event(sd_event *event, ClockState *sp, struct inotify_event *e) {
+        if (e->wd == sp->run_systemd_wd) {
+                /* Only thing we care about is seeing if we can start watching /run/systemd/timesync. */
+                if (sp->run_systemd_timesync_wd < 0)
+                        update_notify_run_systemd_timesync(sp);
+        } else if (e->wd == sp->run_systemd_timesync_wd) {
+                if (e->mask & IN_DELETE_SELF) {
+                        /* Somebody removed /run/systemd/timesync. */
+                        (void) inotify_rm_watch(sp->inotify_fd, sp->run_systemd_timesync_wd);
+                        sp->run_systemd_timesync_wd = -1;
+                } else
+                        /* Somebody might have created /run/systemd/timesync/synchronized. */
+                        clock_state_update(sp, event);
+        }
+}
+
+static int inotify_handler(sd_event_source *s,
+                           int fd,
+                           uint32_t revents,
+                           void *userdata) {
+        sd_event *event = sd_event_source_get_event(s);
+        ClockState *sp = userdata;
+        union inotify_event_buffer buffer;
+        ssize_t l;
+
+        l = read(fd, &buffer, sizeof(buffer));
+        if (l < 0) {
+                if (ERRNO_IS_TRANSIENT(errno))
+                        return 0;
+
+                return log_warning_errno(errno, "Lost access to inotify: %m");
+        }
+        FOREACH_INOTIFY_EVENT_WARN(e, buffer, l)
+                process_inotify_event(event, sp, e);
+
+        return 0;
+}
+
+static int clock_state_update(
+                ClockState *sp,
+                sd_event *event) {
+
+        struct timex tx = {};
+        usec_t t;
+        int r;
+
+        clock_state_release_timerfd(sp);
+
+        /* The kernel supports cancelling timers whenever its realtime clock is "set" (which can happen in a variety of
+         * ways, generally adjustments of at least 500 ms). The way this module works is we set up a timerfd that will
+         * wake when the clock is set, and when that happens we read the clock synchronization state from the return
+         * value of adjtimex(2), which supports the NTP time adjustment protocol.
+         *
+         * The kernel determines whether the clock is synchronized using driver-specific tests, based on time
+         * information passed by an application, generally through adjtimex(2). If the application asserts the clock is
+         * synchronized, but does not also do something that "sets the clock", the timer will not be cancelled and
+         * synchronization will not be detected.
+         *
+         * Similarly, this service will never complete if the application sets the time without also providing
+         * information that adjtimex(2) can use to determine that the clock is synchronized. This generally doesn't
+         * happen, but can if the system has a hardware clock that is accurate enough that the adjustment is too small
+         * to be a "set".
+         *
+         * Both these failure-to-detect situations are covered by having the presence/creation of
+         * /run/systemd/timesync/synchronized, which is considered sufficient to indicate a synchronized clock even if
+         * the kernel has not been updated.
+         *
+         * For timesyncd the initial setting of the time uses settimeofday(2), which sets the clock but does not mark
+         * it synchronized. When an NTP source is selected it sets the clock again with clock_adjtime(2) which marks it
+         * synchronized and also touches /run/systemd/timesync/synchronized which covers the case when the clock wasn't
+         * "set". */
+
+        r = time_change_fd();
+        if (r < 0) {
+                log_error_errno(r, "Failed to create timerfd: %m");
+                goto finish;
+        }
+        sp->timerfd_fd = r;
+
+        r = adjtimex(&tx);
+        if (r < 0) {
+                log_error_errno(errno, "Failed to read adjtimex state: %m");
+                goto finish;
+        }
+        sp->adjtime_state = r;
+
+        if (tx.status & STA_NANO)
+                tx.time.tv_usec /= 1000;
+        t = timeval_load(&tx.time);
+
+        log_info("adjtime state %i status %x time %s", sp->adjtime_state, (unsigned) tx.status,
+                 FORMAT_TIMESTAMP_STYLE(t, TIMESTAMP_US_UTC) ?: "unrepresentable");
+
+        sp->has_watchfile = access("/run/systemd/timesync/synchronized", F_OK) >= 0;
+        if (sp->has_watchfile)
+                /* Presence of watch file overrides adjtime_state */
+                r = 0;
+        else if (sp->adjtime_state == TIME_ERROR) {
+                /* Not synchronized.  Do a one-shot wait on the descriptor and inform the caller we need to keep
+                 * running. */
+                r = sd_event_add_io(event, &sp->timerfd_event_source, sp->timerfd_fd,
+                                    EPOLLIN, timerfd_handler, sp);
+                if (r < 0) {
+                        log_error_errno(r, "Failed to create time change monitor source: %m");
+                        goto finish;
+                }
+                r = 1;
+        } else
+                /* Synchronized; we can exit. */
+                r = 0;
+
+ finish:
+        if (r <= 0)
+                (void) sd_event_exit(event, r);
+        return r;
+}
+
+static int run(int argc, char * argv[]) {
+        _cleanup_(sd_event_unrefp) sd_event *event = NULL;
+        _cleanup_(clock_state_release) ClockState state = {
+                .timerfd_fd = -EBADF,
+                .inotify_fd = -EBADF,
+                .run_systemd_wd = -1,
+                .run_systemd_timesync_wd = -1,
+        };
+        int r;
+
+        assert_se(sigprocmask_many(SIG_BLOCK, NULL, SIGTERM, SIGINT, -1) >= 0);
+
+        r = sd_event_default(&event);
+        if (r < 0)
+                return log_error_errno(r, "Failed to allocate event loop: %m");
+
+        r = sd_event_add_signal(event, NULL, SIGTERM, NULL, NULL);
+        if (r < 0)
+                return log_error_errno(r, "Failed to create sigterm event source: %m");
+
+        r = sd_event_add_signal(event, NULL, SIGINT, NULL, NULL);
+        if (r < 0)
+                return log_error_errno(r, "Failed to create sigint event source: %m");
+
+        r = sd_event_set_watchdog(event, true);
+        if (r < 0)
+                return log_error_errno(r, "Failed to create watchdog event source: %m");
+
+        r = inotify_init1(IN_NONBLOCK|IN_CLOEXEC);
+        if (r < 0)
+                return log_error_errno(errno, "Failed to create inotify descriptor: %m");
+
+        state.inotify_fd = r;
+
+        r = sd_event_add_io(event, &state.inotify_event_source, state.inotify_fd,
+                            EPOLLIN, inotify_handler, &state);
+        if (r < 0)
+                return log_error_errno(r, "Failed to create notify event source: %m");
+
+        r = inotify_add_watch_and_warn(state.inotify_fd, "/run/systemd/", IN_CREATE);
+        if (r < 0)
+                return r;
+
+        state.run_systemd_wd = r;
+
+        (void) update_notify_run_systemd_timesync(&state);
+
+        r = clock_state_update(&state, event);
+        if (r > 0) {
+                r = sd_event_loop(event);
+                if (r < 0)
+                        log_error_errno(r, "Failed in event loop: %m");
+        }
+
+        if (state.has_watchfile)
+                log_debug("Exit enabled by: /run/systemd/timesync/synchronized");
+
+        if (state.adjtime_state == TIME_ERROR)
+                log_info("Exit without adjtimex synchronized.");
+
+        return r;
+}
+
+DEFINE_MAIN_FUNCTION(run);