Merge pull request #2843 from NetworkManager/clock_boottime

time-util: fall back to CLOCK_MONOTONIC if CLOCK_BOOTTIME unsupported

src/basic/time-util.c

@@ -47,12 +47,15 @@ static clockid_t map_clock_id(clockid_t c) {
         /* Some more exotic archs (s390, ppc, …) lack the "ALARM" flavour of the clocks. Thus, clock_gettime() will
          * fail for them. Since they are essentially the same as their non-ALARM pendants (their only difference is
          * when timers are set on them), let's just map them accordingly. This way, we can get the correct time even on
-         * those archs. */
+         * those archs.
+         *
+         * Also, older kernels don't support CLOCK_BOOTTIME: fall back to CLOCK_MONOTONIC. */
 
         switch (c) {
 
+        case CLOCK_BOOTTIME:
         case CLOCK_BOOTTIME_ALARM:
-                return CLOCK_BOOTTIME;
+                return clock_boottime_or_monotonic ();
 
         case CLOCK_REALTIME_ALARM:
                 return CLOCK_REALTIME;