timesyncd: lookup name server via sd-resolve, support IPv6, react to SIGINT/SITERM

4 files changed, 237 insertions, 152 deletions

diff --git a/Makefile.am b/Makefile.am
index e4525a4f1c..cbb405b15e 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -4023,6 +4023,7 @@ systemd_timesyncd_LDADD = \
 	libsystemd-label.la \
 	libsystemd-internal.la \
 	libsystemd-shared.la \
+	libsystemd-resolve.la \
 	-lm
 
 rootlibexec_PROGRAMS += \
diff --git a/src/shared/util.c b/src/shared/util.c
index 5bf9c9fabd..d1dc476ab6 100644
--- a/src/shared/util.c
+++ b/src/shared/util.c
@@ -2016,7 +2016,6 @@ int ignore_signals(int sig, ...) {
         va_list ap;
         int r = 0;
 
-
         if (sigaction(sig, &sa, NULL) < 0)
                 r = -errno;
 
@@ -2442,6 +2441,24 @@ void sigset_add_many(sigset_t *ss, ...) {
         va_end(ap);
 }
 
+int sigprocmask_many(int how, ...) {
+        va_list ap;
+        sigset_t ss;
+        int sig;
+
+        assert_se(sigemptyset(&ss) == 0);
+
+        va_start(ap, how);
+        while ((sig = va_arg(ap, int)) > 0)
+                assert_se(sigaddset(&ss, sig) == 0);
+        va_end(ap);
+
+        if (sigprocmask(how, &ss, NULL) < 0)
+                return -errno;
+
+        return 0;
+}
+
 char* gethostname_malloc(void) {
         struct utsname u;
 
diff --git a/src/shared/util.h b/src/shared/util.h
index d584a65979..891fcee239 100644
--- a/src/shared/util.h
+++ b/src/shared/util.h
@@ -393,6 +393,7 @@ char* dirname_malloc(const char *path);
 void rename_process(const char name[8]);
 
 void sigset_add_many(sigset_t *ss, ...);
+int sigprocmask_many(int how, ...);
 
 bool hostname_is_set(void);
 
diff --git a/src/timesync/timesyncd.c b/src/timesync/timesyncd.c
index 3cf3579576..a66d1e46c0 100644
--- a/src/timesync/timesyncd.c
+++ b/src/timesync/timesyncd.c
@@ -39,6 +39,7 @@
 #include "log.h"
 #include "socket-util.h"
 #include "sd-event.h"
+#include "sd-resolve.h"
 #include "sd-daemon.h"
 
 #define TIME_T_MAX (time_t)((1UL << ((sizeof(time_t) << 3) - 1)) - 1)
@@ -108,11 +109,14 @@ struct ntp_msg {
 typedef struct Manager Manager;
 struct Manager {
         sd_event *event;
+        sd_resolve *resolve;
 
         /* peer */
+        sd_resolve_query *resolve_query;
         sd_event_source *event_receive;
         char *server;
         union sockaddr_union server_addr;
+        socklen_t server_addr_length;
         int server_socket;
         uint64_t packet_count;
 
@@ -142,15 +146,17 @@ struct Manager {
         /* watch for time changes */
         sd_event_source *event_clock_watch;
         int clock_watch_fd;
+
+        /* Handle SIGINT/SIGTERM */
+        sd_event_source *sigterm, *sigint;
 };
 
 static void manager_free(Manager *m);
 DEFINE_TRIVIAL_CLEANUP_FUNC(Manager*, manager_free);
 #define _cleanup_manager_free_ _cleanup_(manager_freep)
 
-static int sntp_arm_timer(Manager *m, usec_t next);
-static int sntp_clock_watch_setup(Manager *m);
-static void sntp_server_disconnect(Manager *m);
+static int manager_arm_timer(Manager *m, usec_t next);
+static int manager_clock_watch_setup(Manager *m);
 
 static double ntp_ts_to_d(const struct ntp_ts *ts) {
         return be32toh(ts->sec) + ((double)be32toh(ts->frac) / UINT_MAX);
@@ -168,7 +174,7 @@ static double square(double d) {
         return d * d;
 }
 
-static int sntp_send_request(Manager *m) {
+static int manager_send_request(Manager *m) {
         struct ntp_msg ntpmsg = {
                 /*
                  * "The client initializes the NTP message header, sends the request
@@ -179,14 +185,7 @@ static int sntp_send_request(Manager *m) {
                  */
                 .field = NTP_FIELD(0, 4, NTP_MODE_CLIENT),
         };
-
-        union sockaddr_union addr = {
-                .in.sin_family = AF_INET,
-                .in.sin_port = htobe16(123),
-        };
         ssize_t len;
-        int r;
-
 
         /*
          * Set transmit timestamp, remember it; the server will send that back
@@ -196,13 +195,12 @@ static int sntp_send_request(Manager *m) {
          * The actual value does not matter, We do not care about the correct
          * NTP UINT_MAX fraction; we just pass the plain nanosecond value.
          */
-        clock_gettime(CLOCK_MONOTONIC, &m->trans_time_mon);
-        clock_gettime(CLOCK_REALTIME, &m->trans_time);
+        assert_se(clock_gettime(CLOCK_MONOTONIC, &m->trans_time_mon) >= 0);
+        assert_se(clock_gettime(CLOCK_REALTIME, &m->trans_time) >= 0);
         ntpmsg.trans_time.sec = htobe32(m->trans_time.tv_sec + OFFSET_1900_1970);
         ntpmsg.trans_time.frac = htobe32(m->trans_time.tv_nsec);
 
-        addr.in.sin_addr.s_addr = inet_addr(m->server);
-        len = sendto(m->server_socket, &ntpmsg, sizeof(ntpmsg), MSG_DONTWAIT, &addr.sa, sizeof(addr.in));
+        len = sendto(m->server_socket, &ntpmsg, sizeof(ntpmsg), MSG_DONTWAIT, &m->server_addr.sa, m->server_addr_length);
         if (len == sizeof(ntpmsg)) {
                 m->pending = true;
                 log_debug("Sent NTP request to: %s", m->server);
@@ -215,23 +213,19 @@ static int sntp_send_request(Manager *m) {
                         m->retry_interval *= 2;
         } else
                 m->retry_interval = NTP_POLL_INTERVAL_MIN_SEC * USEC_PER_SEC;
-        r = sntp_arm_timer(m, m->retry_interval);
-        if (r < 0)
-                return r;
 
-        return 0;
+        return manager_arm_timer(m, m->retry_interval);
 }
 
-static int sntp_timer(sd_event_source *source, usec_t usec, void *userdata) {
+static int manager_timer(sd_event_source *source, usec_t usec, void *userdata) {
         Manager *m = userdata;
 
         assert(m);
 
-        sntp_send_request(m);
-        return 0;
+        return manager_send_request(m);
 }
 
-static int sntp_arm_timer(Manager *m, usec_t next) {
+static int manager_arm_timer(Manager *m, usec_t next) {
         int r;
 
         assert(m);
@@ -250,26 +244,21 @@ static int sntp_arm_timer(Manager *m, usec_t next) {
                 return sd_event_source_set_enabled(m->event_timer, SD_EVENT_ONESHOT);
         }
 
-        r = sd_event_add_time(
+        return sd_event_add_time(
                         m->event,
                         &m->event_timer,
                         CLOCK_MONOTONIC,
                         now(CLOCK_MONOTONIC) + next, 0,
-                        sntp_timer, m);
-        if (r < 0)
-                return r;
-
-        return 0;
+                        manager_timer, m);
 }
 
-static int sntp_clock_watch(sd_event_source *source, int fd, uint32_t revents, void *userdata) {
+static int manager_clock_watch(sd_event_source *source, int fd, uint32_t revents, void *userdata) {
         Manager *m = userdata;
 
         assert(m);
-        assert(m->event_receive);
 
         /* rearm timer */
-        sntp_clock_watch_setup(m);
+        manager_clock_watch_setup(m);
 
         /* skip our own jumps */
         if (m->jumped) {
@@ -280,56 +269,49 @@ static int sntp_clock_watch(sd_event_source *source, int fd, uint32_t revents, v
         /* resync */
         log_info("System time changed. Resyncing.");
         m->poll_resync = true;
-        sntp_send_request(m);
-
-        return 0;
+        return manager_send_request(m);
 }
 
 /* wake up when the system time changes underneath us */
-static int sntp_clock_watch_setup(Manager *m) {
+static int manager_clock_watch_setup(Manager *m) {
 
         struct itimerspec its = {
                 .it_value.tv_sec = TIME_T_MAX
         };
 
-        _cleanup_close_ int fd = -1;
-        sd_event_source *source;
         int r;
 
         assert(m);
-        assert(m->event_receive);
 
-        fd = timerfd_create(CLOCK_REALTIME, TFD_NONBLOCK|TFD_CLOEXEC);
-        if (fd < 0) {
+        m->event_clock_watch = sd_event_source_unref(m->event_clock_watch);
+        m->clock_watch_fd = safe_close(m->clock_watch_fd);
+
+        m->clock_watch_fd = timerfd_create(CLOCK_REALTIME, TFD_NONBLOCK|TFD_CLOEXEC);
+        if (m->clock_watch_fd < 0) {
                 log_error("Failed to create timerfd: %m");
                 return -errno;
         }
 
-        if (timerfd_settime(fd, TFD_TIMER_ABSTIME|TFD_TIMER_CANCEL_ON_SET, &its, NULL) < 0) {
+        if (timerfd_settime(m->clock_watch_fd, TFD_TIMER_ABSTIME|TFD_TIMER_CANCEL_ON_SET, &its, NULL) < 0) {
                 log_error("Failed to set up timerfd: %m");
                 return -errno;
         }
 
-        r = sd_event_add_io(m->event, &source, fd, EPOLLIN, sntp_clock_watch, m);
+        r = sd_event_add_io(m->event, &m->event_clock_watch, m->clock_watch_fd, EPOLLIN, manager_clock_watch, m);
         if (r < 0) {
                 log_error("Failed to create clock watch event source: %s", strerror(-r));
                 return r;
         }
 
-        sd_event_source_unref(m->event_clock_watch);
-        m->event_clock_watch = source;
-
-        safe_close(m->clock_watch_fd);
-        m->clock_watch_fd = fd;
-        fd = -1;
-
         return 0;
 }
 
-static int sntp_adjust_clock(Manager *m, double offset, int leap_sec) {
+static int manager_adjust_clock(Manager *m, double offset, int leap_sec) {
         struct timex tmx = {};
         int r;
 
+        assert(m);
+
         /*
          * For small deltas, tell the kernel to gradually adjust the system
          * clock to the NTP time, larger deltas are just directly set.
@@ -391,11 +373,13 @@ static int sntp_adjust_clock(Manager *m, double offset, int leap_sec) {
         return 0;
 }
 
-static bool sntp_sample_spike_detection(Manager *m, double offset, double delay) {
+static bool manager_sample_spike_detection(Manager *m, double offset, double delay) {
         unsigned int i, idx_cur, idx_new, idx_min;
         double jitter;
         double j;
 
+        assert(m);
+
         m->packet_count++;
 
         /* ignore initial sample */
@@ -440,7 +424,9 @@ static bool sntp_sample_spike_detection(Manager *m, double offset, double delay)
         return fabs(offset - m->samples[idx_cur].offset) > 3 * jitter;
 }
 
-static void sntp_adjust_poll(Manager *m, double offset, bool spike) {
+static void manager_adjust_poll(Manager *m, double offset, bool spike) {
+        assert(m);
+
         if (m->poll_resync) {
                 m->poll_interval_usec = NTP_POLL_INTERVAL_MIN_SEC * USEC_PER_SEC;
                 m->poll_resync = false;
@@ -468,12 +454,29 @@ static void sntp_adjust_poll(Manager *m, double offset, bool spike) {
         }
 }
 
-static int sntp_receive_response(sd_event_source *source, int fd, uint32_t revents, void *userdata) {
+static bool sockaddr_equal(union sockaddr_union *a, union sockaddr_union *b) {
+        assert(a);
+        assert(b);
+
+        if (a->sa.sa_family != b->sa.sa_family)
+                return false;
+
+        if (a->sa.sa_family == AF_INET)
+                return a->in.sin_addr.s_addr == b->in.sin_addr.s_addr;
+
+        if (a->sa.sa_family == AF_INET6)
+                return memcmp(&a->in6.sin6_addr, &b->in6.sin6_addr, sizeof(a->in6.sin6_addr)) == 0;
+
+        return false;
+}
+
+static int manager_receive_response(sd_event_source *source, int fd, uint32_t revents, void *userdata) {
         Manager *m = userdata;
-        unsigned char buf[sizeof(struct ntp_msg)];
+        struct ntp_msg ntpmsg;
+
         struct iovec iov = {
-                .iov_base = buf,
-                .iov_len = sizeof(buf),
+                .iov_base = &ntpmsg,
+                .iov_len = sizeof(ntpmsg),
         };
         union {
                 struct cmsghdr cmsghdr;
@@ -492,7 +495,6 @@ static int sntp_receive_response(sd_event_source *source, int fd, uint32_t reven
         struct timespec now_ts;
         struct timeval *recv_time;
         ssize_t len;
-        struct ntp_msg *ntpmsg;
         double origin, receive, trans, dest;
         double delay, offset;
         bool spike;
@@ -500,15 +502,17 @@ static int sntp_receive_response(sd_event_source *source, int fd, uint32_t reven
         int r;
 
         if (revents & (EPOLLHUP|EPOLLERR)) {
-                log_debug("Server connection returned error. Closing.");
-                sntp_server_disconnect(m);
+                log_debug("Server connection returned error.");
                 return -ENOTCONN;
         }
 
         len = recvmsg(fd, &msghdr, MSG_DONTWAIT);
         if (len < 0) {
+                if (errno == EAGAIN)
+                        return 0;
+
                 log_debug("Error receiving message. Disconnecting.");
-                return -EINVAL;
+                return -errno;
         }
 
         if (iov.iov_len < sizeof(struct ntp_msg)) {
@@ -516,7 +520,7 @@ static int sntp_receive_response(sd_event_source *source, int fd, uint32_t reven
                 return -EINVAL;
         }
 
-        if (m->server_addr.in.sin_addr.s_addr != server_addr.in.sin_addr.s_addr) {
+        if (!sockaddr_equal(&server_addr, &m->server_addr)) {
                 log_debug("Response from unknown server. Disconnecting.");
                 return -EINVAL;
         }
@@ -537,31 +541,30 @@ static int sntp_receive_response(sd_event_source *source, int fd, uint32_t reven
                 return -EINVAL;
         }
 
-        ntpmsg = iov.iov_base;
         if (!m->pending) {
                 log_debug("Unexpected reply. Ignoring.");
                 return 0;
         }
 
         /* check our "time cookie" (we just stored nanoseconds in the fraction field) */
-        if (be32toh(ntpmsg->origin_time.sec) != m->trans_time.tv_sec + OFFSET_1900_1970 ||
-            be32toh(ntpmsg->origin_time.frac) != m->trans_time.tv_nsec) {
+        if (be32toh(ntpmsg.origin_time.sec) != m->trans_time.tv_sec + OFFSET_1900_1970 ||
+            be32toh(ntpmsg.origin_time.frac) != m->trans_time.tv_nsec) {
                 log_debug("Invalid reply; not our transmit time. Ignoring.");
                 return 0;
         }
 
-        if (NTP_FIELD_LEAP(ntpmsg->field) == NTP_LEAP_NOTINSYNC) {
+        if (NTP_FIELD_LEAP(ntpmsg.field) == NTP_LEAP_NOTINSYNC) {
                 log_debug("Server is not synchronized. Disconnecting.");
                 return -EINVAL;
         }
 
-        if (NTP_FIELD_VERSION(ntpmsg->field) != 4) {
-                log_debug("Response NTPv%d. Disconnecting.", NTP_FIELD_VERSION(ntpmsg->field));
+        if (NTP_FIELD_VERSION(ntpmsg.field) != 4) {
+                log_debug("Response NTPv%d. Disconnecting.", NTP_FIELD_VERSION(ntpmsg.field));
                 return -EINVAL;
         }
 
-        if (NTP_FIELD_MODE(ntpmsg->field) != NTP_MODE_SERVER) {
-                log_debug("Unsupported mode %d. Disconnecting.", NTP_FIELD_MODE(ntpmsg->field));
+        if (NTP_FIELD_MODE(ntpmsg.field) != NTP_MODE_SERVER) {
+                log_debug("Unsupported mode %d. Disconnecting.", NTP_FIELD_MODE(ntpmsg.field));
                 return -EINVAL;
         }
 
@@ -570,9 +573,9 @@ static int sntp_receive_response(sd_event_source *source, int fd, uint32_t reven
         m->retry_interval = 0;
 
         /* announce leap seconds */
-        if (NTP_FIELD_LEAP(ntpmsg->field) & NTP_LEAP_PLUSSEC)
+        if (NTP_FIELD_LEAP(ntpmsg.field) & NTP_LEAP_PLUSSEC)
                 leap_sec = 1;
-        else if (NTP_FIELD_LEAP(ntpmsg->field) & NTP_LEAP_MINUSSEC)
+        else if (NTP_FIELD_LEAP(ntpmsg.field) & NTP_LEAP_MINUSSEC)
                 leap_sec = -1;
         else
                 leap_sec = 0;
@@ -588,18 +591,18 @@ static int sntp_receive_response(sd_event_source *source, int fd, uint32_t reven
          *  The round-trip delay, d, and system clock offset, t, are defined as:
          *  d = (T4 - T1) - (T3 - T2)     t = ((T2 - T1) + (T3 - T4)) / 2"
          */
-        clock_gettime(CLOCK_MONOTONIC, &now_ts);
+        assert_se(clock_gettime(CLOCK_MONOTONIC, &now_ts) >= 0);
         origin = tv_to_d(recv_time) - (ts_to_d(&now_ts) - ts_to_d(&m->trans_time_mon)) + OFFSET_1900_1970;
-        receive = ntp_ts_to_d(&ntpmsg->recv_time);
-        trans = ntp_ts_to_d(&ntpmsg->trans_time);
+        receive = ntp_ts_to_d(&ntpmsg.recv_time);
+        trans = ntp_ts_to_d(&ntpmsg.trans_time);
         dest = tv_to_d(recv_time) + OFFSET_1900_1970;
 
         offset = ((receive - origin) + (trans - dest)) / 2;
         delay = (dest - origin) - (trans - receive);
 
-        spike = sntp_sample_spike_detection(m, offset, delay);
+        spike = manager_sample_spike_detection(m, offset, delay);
 
-        sntp_adjust_poll(m, offset, spike);
+        manager_adjust_poll(m, offset, spike);
 
         log_debug("NTP response:\n"
                   "  leap         : %u\n"
@@ -617,12 +620,12 @@ static int sntp_receive_response(sd_event_source *source, int fd, uint32_t reven
                   "  packet count : %"PRIu64"\n"
                   "  jitter       : %.3f%s\n"
                   "  poll interval: %llu\n",
-                  NTP_FIELD_LEAP(ntpmsg->field),
-                  NTP_FIELD_VERSION(ntpmsg->field),
-                  NTP_FIELD_MODE(ntpmsg->field),
-                  ntpmsg->stratum,
-                  exp2(ntpmsg->precision), ntpmsg->precision,
-                  ntpmsg->stratum == 1 ? ntpmsg->refid : "n/a",
+                  NTP_FIELD_LEAP(ntpmsg.field),
+                  NTP_FIELD_VERSION(ntpmsg.field),
+                  NTP_FIELD_MODE(ntpmsg.field),
+                  ntpmsg.stratum,
+                  exp2(ntpmsg.precision), ntpmsg.precision,
+                  ntpmsg.stratum == 1 ? ntpmsg.refid : "n/a",
                   origin - OFFSET_1900_1970,
                   receive - OFFSET_1900_1970,
                   trans - OFFSET_1900_1970,
@@ -633,7 +636,7 @@ static int sntp_receive_response(sd_event_source *source, int fd, uint32_t reven
                   m->poll_interval_usec / USEC_PER_SEC);
 
         if (!spike) {
-                r = sntp_adjust_clock(m, offset, leap_sec);
+                r = manager_adjust_clock(m, offset, leap_sec);
                 if (r < 0)
                         log_error("Failed to call clock_adjtime(): %m");
         }
@@ -641,89 +644,132 @@ static int sntp_receive_response(sd_event_source *source, int fd, uint32_t reven
         log_info("%s: interval/delta/delay/jitter/drift %llus/%+.3fs/%.3fs/%.3fs/%+ippm%s",
                  m->server, m->poll_interval_usec / USEC_PER_SEC, offset, delay, m->samples_jitter, m->drift_ppm,
                  spike ? " (ignored)" : "");
-        r = sntp_arm_timer(m, m->poll_interval_usec);
-        if (r < 0)
-                return r;
 
-        return 0;
+        return manager_arm_timer(m, m->poll_interval_usec);
 }
 
-static int sntp_server_connect(Manager *m, const char *server) {
-        _cleanup_free_ char *s = NULL;
+static int manager_listen_setup(Manager *m) {
+        union sockaddr_union addr = {};
+        static const int tos = IPTOS_LOWDELAY;
+        static const int on = 1;
+        int r;
 
         assert(m);
-        assert(server);
-        assert(m->server_socket >= 0);
 
-        s = strdup(server);
-        if (!s)
-                return -ENOMEM;
+        assert(m->server_socket < 0);
+        assert(!m->event_receive);
 
-        free(m->server);
-        m->server = s;
-        s = NULL;
+        addr.sa.sa_family = m->server_addr.sa.sa_family;
 
-        zero(m->server_addr);
-        m->server_addr.in.sin_family = AF_INET;
-        m->server_addr.in.sin_addr.s_addr = inet_addr(server);
+        m->server_socket = socket(addr.sa.sa_family, SOCK_DGRAM | SOCK_CLOEXEC, 0);
+        if (m->server_socket < 0)
+                return -errno;
 
-        m->poll_interval_usec = NTP_POLL_INTERVAL_MIN_SEC * USEC_PER_SEC;
+        r = bind(m->server_socket, &addr.sa, m->server_addr_length);
+        if (r < 0)
+                return -errno;
+
+        r = setsockopt(m->server_socket, SOL_SOCKET, SO_TIMESTAMP, &on, sizeof(on));
+        if (r < 0)
+                return -errno;
+
+        setsockopt(m->server_socket, IPPROTO_IP, IP_TOS, &tos, sizeof(tos));
 
-        return sntp_send_request(m);
+        return sd_event_add_io(m->event, &m->event_receive, m->server_socket, EPOLLIN, manager_receive_response, m);
 }
 
-static void sntp_server_disconnect(Manager *m) {
-        if (!m->server)
-                return;
+static int manager_resolve_handler(sd_resolve_query *q, int ret, const struct addrinfo *ai, void *userdata) {
+        _cleanup_free_ char *pretty = NULL;
+        Manager *m = userdata;
+        int r;
 
-        m->event_timer = sd_event_source_unref(m->event_timer);
+        assert(q);
+        assert(m);
 
-        m->event_clock_watch = sd_event_source_unref(m->event_clock_watch);
-        m->clock_watch_fd = safe_close(m->clock_watch_fd);
+        m->resolve_query = sd_resolve_query_unref(m->resolve_query);
 
-        m->event_receive = sd_event_source_unref(m->event_receive);
-        m->server_socket = safe_close(m->server_socket);
+        if (ret != 0) {
+                log_error("Failed to resolve %s: %s", m->server, gai_strerror(ret));
+                return -EHOSTUNREACH;
+        }
 
-        zero(m->server_addr);
-        free(m->server);
-        m->server = NULL;
+        assert(ai);
+        assert(ai->ai_addr);
+        assert(ai->ai_addrlen >= offsetof(struct sockaddr, sa_data));
+        assert(ai->ai_addrlen <= sizeof(union sockaddr_union));
+
+        if (!IN_SET(ai->ai_addr->sa_family, AF_INET, AF_INET6)) {
+                log_warning("Failed to find IP address for %s", m->server);
+                return -EHOSTUNREACH;
+        }
+
+        memcpy(&m->server_addr, ai->ai_addr, ai->ai_addrlen);
+        m->server_addr_length = ai->ai_addrlen;
+
+        r = sockaddr_pretty(&m->server_addr.sa, m->server_addr_length, true, &pretty);
+        if (r < 0) {
+                log_warning("Failed to decode address of %s: %s", m->server, strerror(-r));
+                return r;
+        }
+
+        log_debug("Connecting to NTP server %s.", pretty);
+        sd_notifyf(false, "STATUS=Using Time Server %s", pretty);
+
+        r = manager_listen_setup(m);
+        if (r < 0) {
+                log_warning("Failed to setup connection socket: %s", strerror(-r));
+                return r;
+        }
+
+        r = manager_clock_watch_setup(m);
+        if (r < 0) {
+                log_warning("Failed to setup clock watch: %s", strerror(-r));
+                return r;
+        }
+
+        return manager_send_request(m);
 }
 
-static int sntp_listen_setup(Manager *m) {
+static int manager_connect(Manager *m, const char *server) {
 
-        union sockaddr_union addr = {
-                .in.sin_family = AF_INET,
+        struct addrinfo hints = {
+                .ai_flags = AI_NUMERICSERV|AI_ADDRCONFIG,
+                .ai_socktype = SOCK_DGRAM,
         };
 
-        _cleanup_close_ int fd = -1;
-        const int on = 1;
-        const int tos = IPTOS_LOWDELAY;
-        int r;
+        assert(m);
+        assert(server);
 
-        fd = socket(PF_INET, SOCK_DGRAM | SOCK_CLOEXEC, 0);
-        if (fd < 0)
-                return -errno;
+        if (m->server)
+                return -EBUSY;
 
-        r = bind(fd, &addr.sa, sizeof(addr.in));
-        if (r < 0)
-                return -errno;
+        m->server = strdup(server);
+        if (!m->server)
+                return -ENOMEM;
 
-        r = setsockopt(fd, SOL_SOCKET, SO_TIMESTAMP, &on, sizeof(on));
-        if (r < 0)
-                return -errno;
+        m->poll_interval_usec = NTP_POLL_INTERVAL_MIN_SEC * USEC_PER_SEC;
 
-        r = setsockopt(fd, IPPROTO_IP, IP_TOS, &tos, sizeof(tos));
-        if (r < 0)
-                return -errno;
+        return sd_resolve_getaddrinfo(m->resolve, &m->resolve_query, m->server, "123", &hints, manager_resolve_handler, m);
+}
 
-        r = sd_event_add_io(m->event, &m->event_receive, fd, EPOLLIN, sntp_receive_response, m);
-        if (r < 0)
-                return r;
+static void manager_disconnect(Manager *m) {
+        assert(m);
 
-        m->server_socket = fd;
-        fd = -1;
+        m->resolve_query = sd_resolve_query_unref(m->resolve_query);
 
-        return 0;
+        m->event_timer = sd_event_source_unref(m->event_timer);
+
+        m->event_receive = sd_event_source_unref(m->event_receive);
+        m->server_socket = safe_close(m->server_socket);
+
+        zero(m->server_addr);
+        m->server_addr_length = 0;
+
+        free(m->server);
+        m->server = NULL;
+
+        m->event_clock_watch = sd_event_source_unref(m->event_clock_watch);
+        m->clock_watch_fd = safe_close(m->clock_watch_fd);
 }
 
 static int manager_new(Manager **ret) {
@@ -734,15 +780,24 @@ static int manager_new(Manager **ret) {
         if (!m)
                 return -ENOMEM;
 
+        m->server_socket = m->clock_watch_fd = -1;
+
         r = sd_event_default(&m->event);
         if (r < 0)
                 return r;
 
-        r = sntp_listen_setup(m);
+        sd_event_add_signal(m->event, &m->sigterm, SIGTERM, NULL,  NULL);
+        sd_event_add_signal(m->event, &m->sigint, SIGINT, NULL, NULL);
+
+        r = sd_resolve_default(&m->resolve);
         if (r < 0)
                 return r;
 
-        r = sntp_clock_watch_setup(m);
+        r = sd_resolve_attach_event(m->resolve, m->event, 0);
+        if (r < 0)
+                return 0;
+
+        r = manager_clock_watch_setup(m);
         if (r < 0)
                 return r;
 
@@ -753,40 +808,51 @@ static int manager_new(Manager **ret) {
 }
 
 static void manager_free(Manager *m) {
-
         if (!m)
                 return;
 
+        manager_disconnect(m);
+
+        sd_event_source_unref(m->sigint);
+        sd_event_source_unref(m->sigterm);
+
+        sd_resolve_unref(m->resolve);
         sd_event_unref(m->event);
+
         free(m);
 }
 
 int main(int argc, char *argv[]) {
         _cleanup_manager_free_ Manager *m = NULL;
-        const char *server;
         int r;
 
         log_set_target(LOG_TARGET_AUTO);
         log_parse_environment();
         log_open();
 
+        assert_se(sigprocmask_many(SIG_BLOCK, SIGTERM, SIGINT, -1) == 0);
+
         r = manager_new(&m);
-        if (r < 0)
+        if (r < 0) {
+                log_error("Failed to allocate manager: %s", strerror(-r));
                 goto out;
-
-        server = "216.239.32.15";       /* time1.google.com */
+        }
 
         sd_notify(false, "READY=1");
 
-        r = sntp_server_connect(m, server);
-        if (r < 0)
+        r = manager_connect(m, "time1.google.com");
+        if (r < 0) {
+                log_error("Failed to initiate connection: %s", strerror(-r));
                 goto out;
-
-        sd_notifyf(false, "STATUS=Using Time Server: %s", server);
+        }
 
         r = sd_event_loop(m->event);
-        if (r < 0)
+        if (r < 0) {
+                log_error("Failed to run event loop: %s", strerror(-r));
                 goto out;
+        }
+
+        sd_event_get_exit_code(m->event, &r);
 
 out:
         return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;