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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-10 20:49:52 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-10 20:49:52 +0000
commit55944e5e40b1be2afc4855d8d2baf4b73d1876b5 (patch)
tree33f869f55a1b149e9b7c2b7e201867ca5dd52992 /src/timesync/timesyncd.c
parentInitial commit. (diff)
downloadsystemd-55944e5e40b1be2afc4855d8d2baf4b73d1876b5.tar.xz
systemd-55944e5e40b1be2afc4855d8d2baf4b73d1876b5.zip
Adding upstream version 255.4.upstream/255.4
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/timesync/timesyncd.c')
-rw-r--r--src/timesync/timesyncd.c231
1 files changed, 231 insertions, 0 deletions
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);