src/timesync/timesyncd.c

   1 /***
   2   This file is part of systemd.
   3
   4   Copyright 2014 Kay Sievers, Lennart Poettering
   5
   6   systemd is free software; you can redistribute it and/or modify it
   7   under the terms of the GNU Lesser General Public License as published by
   8   the Free Software Foundation; either version 2.1 of the License, or
   9   (at your option) any later version.
  10
  11   systemd is distributed in the hope that it will be useful, but
  12   WITHOUT ANY WARRANTY; without even the implied warranty of
  13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14   Lesser General Public License for more details.
  15
  16   You should have received a copy of the GNU Lesser General Public License
  17   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  18 ***/
  19
  20 #include "sd-daemon.h"
  21 #include "sd-event.h"
  22
  23 #include "capability-util.h"
  24 #include "clock-util.h"
  25 #include "fd-util.h"
  26 #include "fs-util.h"
  27 #include "network-util.h"
  28 #include "process-util.h"
  29 #include "signal-util.h"
  30 #include "timesyncd-conf.h"
  31 #include "timesyncd-manager.h"
  32 #include "user-util.h"
  33
  34 static int load_clock_timestamp(uid_t uid, gid_t gid) {
  35         _cleanup_close_ int fd = -1;
  36         usec_t min = TIME_EPOCH * USEC_PER_SEC;
  37         usec_t ct;
  38         int r;
  39
  40         /* Let's try to make sure that the clock is always
  41          * monotonically increasing, by saving the clock whenever we
  42          * have a new NTP time, or when we shut down, and restoring it
  43          * when we start again. This is particularly helpful on
  44          * systems lacking a battery backed RTC. We also will adjust
  45          * the time to at least the build time of systemd. */
  46
  47         fd = open("/var/lib/systemd/clock", O_RDWR|O_CLOEXEC, 0644);
  48         if (fd >= 0) {
  49                 struct stat st;
  50                 usec_t stamp;
  51
  52                 /* check if the recorded time is later than the compiled-in one */
  53                 r = fstat(fd, &st);
  54                 if (r >= 0) {
  55                         stamp = timespec_load(&st.st_mtim);
  56                         if (stamp > min)
  57                                 min = stamp;
  58                 }
  59
  60                 /* Try to fix the access mode, so that we can still
  61                    touch the file after dropping priviliges */
  62                 (void) fchmod(fd, 0644);
  63                 (void) fchown(fd, uid, gid);
  64
  65         } else
  66                 /* create stamp file with the compiled-in date */
  67                 (void) touch_file("/var/lib/systemd/clock", true, min, uid, gid, 0644);
  68
  69         ct = now(CLOCK_REALTIME);
  70         if (ct < min) {
  71                 struct timespec ts;
  72                 char date[FORMAT_TIMESTAMP_MAX];
  73
  74                 log_info("System clock time unset or jumped backwards, restoring from recorded timestamp: %s",
  75                          format_timestamp(date, sizeof(date), min));
  76
  77                 if (clock_settime(CLOCK_REALTIME, timespec_store(&ts, min)) < 0)
  78                         log_error_errno(errno, "Failed to restore system clock: %m");
  79         }
  80
  81         return 0;
  82 }
  83
  84 int main(int argc, char *argv[]) {
  85         _cleanup_(manager_freep) Manager *m = NULL;
  86         const char *user = "systemd-timesync";
  87         uid_t uid;
  88         gid_t gid;
  89         int r;
  90
  91         log_set_target(LOG_TARGET_AUTO);
  92         log_set_facility(LOG_CRON);
  93         log_parse_environment();
  94         log_open();
  95
  96         umask(0022);
  97
  98         if (argc != 1) {
  99                 log_error("This program does not take arguments.");
 100                 r = -EINVAL;
 101                 goto finish;
 102         }
 103
 104         r = get_user_creds(&user, &uid, &gid, NULL, NULL);
 105         if (r < 0) {
 106                 log_error_errno(r, "Cannot resolve user name %s: %m", user);
 107                 goto finish;
 108         }
 109
 110         r = load_clock_timestamp(uid, gid);
 111         if (r < 0)
 112                 goto finish;
 113
 114         /* Drop privileges, but only if we have been started as root. If we are not running as root we assume all
 115          * privileges are already dropped. */
 116         if (geteuid() == 0) {
 117                 r = drop_privileges(uid, gid, (1ULL << CAP_SYS_TIME));
 118                 if (r < 0)
 119                         goto finish;
 120         }
 121
 122         assert_se(sigprocmask_many(SIG_BLOCK, NULL, SIGTERM, SIGINT, -1) >= 0);
 123
 124         r = manager_new(&m);
 125         if (r < 0) {
 126                 log_error_errno(r, "Failed to allocate manager: %m");
 127                 goto finish;
 128         }
 129
 130         if (clock_is_localtime(NULL) > 0) {
 131                 log_info("The system is configured to read the RTC time in the local time zone. "
 132                          "This mode can not be fully supported. All system time to RTC updates are disabled.");
 133                 m->rtc_local_time = true;
 134         }
 135
 136         r = manager_parse_config_file(m);
 137         if (r < 0)
 138                 log_warning_errno(r, "Failed to parse configuration file: %m");
 139
 140         r = manager_parse_fallback_string(m, NTP_SERVERS);
 141         if (r < 0) {
 142                 log_error_errno(r, "Failed to parse fallback server strings: %m");
 143                 goto finish;
 144         }
 145
 146         log_debug("systemd-timesyncd running as pid " PID_FMT, getpid_cached());
 147         sd_notify(false,
 148                   "READY=1\n"
 149                   "STATUS=Daemon is running");
 150
 151         if (network_is_online()) {
 152                 r = manager_connect(m);
 153                 if (r < 0)
 154                         goto finish;
 155         }
 156
 157         r = sd_event_loop(m->event);
 158         if (r < 0) {
 159                 log_error_errno(r, "Failed to run event loop: %m");
 160                 goto finish;
 161         }
 162
 163         /* if we got an authoritative time, store it in the file system */
 164         if (m->sync)
 165                 (void) touch("/var/lib/systemd/clock");
 166
 167         sd_event_get_exit_code(m->event, &r);
 168
 169 finish:
 170         sd_notify(false,
 171                   "STOPPING=1\n"
 172                   "STATUS=Shutting down...");
 173
 174         return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
 175 }