Adding upstream version 255.4.upstream/255.4

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

1 files changed, 240 insertions, 0 deletions

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);