sd-event: check clock argument to sd_event_now()

sd_event_now() is a public function, so we must check all
arguments for validity. Update man page and add tests.

Sample debug message:
Assertion 'IN_SET(clock, CLOCK_REALTIME, CLOCK_REALTIME_ALARM, CLOCK_MONOTONIC, CLOCK_BOOTTIME, CLOCK_BOOTTIME_ALARM)' failed at src/libsystemd/sd-event/sd-event.c:2719, function sd_event_now(). Ignoring.

3 files changed, 42 insertions, 3 deletions

diff --git a/man/sd_event_now.xml b/man/sd_event_now.xml
index 58d7375eac..6cec0446c8 100644
--- a/man/sd_event_now.xml
+++ b/man/sd_event_now.xml
@@ -115,12 +115,18 @@
       </varlistentry>
 
       <varlistentry>
+        <term><constant>-EOPNOTSUPP</constant></term>
+
+        <listitem><para>Unsupported clock type.
+        </para></listitem>
+      </varlistentry>
+
+      <varlistentry>
         <term><constant>-ECHILD</constant></term>
 
         <listitem><para>The event loop object was created in a
         different process.</para></listitem>
       </varlistentry>
-
     </variablelist>
   </refsect1>
 
diff --git a/src/libsystemd/sd-event/sd-event.c b/src/libsystemd/sd-event/sd-event.c
index aeb06ad9a8..c898ccc3c6 100644
--- a/src/libsystemd/sd-event/sd-event.c
+++ b/src/libsystemd/sd-event/sd-event.c
@@ -2751,6 +2751,12 @@ _public_ int sd_event_now(sd_event *e, clockid_t clock, uint64_t *usec) {
         assert_return(e, -EINVAL);
         assert_return(usec, -EINVAL);
         assert_return(!event_pid_changed(e), -ECHILD);
+        assert_return(IN_SET(clock,
+                             CLOCK_REALTIME,
+                             CLOCK_REALTIME_ALARM,
+                             CLOCK_MONOTONIC,
+                             CLOCK_BOOTTIME,
+                             CLOCK_BOOTTIME_ALARM), -EOPNOTSUPP);
 
         if (!dual_timestamp_is_set(&e->timestamp)) {
                 /* Implicitly fall back to now() if we never ran
@@ -2770,8 +2776,7 @@ _public_ int sd_event_now(sd_event *e, clockid_t clock, uint64_t *usec) {
                 *usec = e->timestamp.monotonic;
                 break;
 
-        case CLOCK_BOOTTIME:
-        case CLOCK_BOOTTIME_ALARM:
+        default:
                 *usec = e->timestamp_boottime;
                 break;
         }
diff --git a/src/libsystemd/sd-event/test-event.c b/src/libsystemd/sd-event/test-event.c
index 9417a8d1d1..c605b18ae9 100644
--- a/src/libsystemd/sd-event/test-event.c
+++ b/src/libsystemd/sd-event/test-event.c
@@ -264,6 +264,30 @@ static void test_basic(void) {
         safe_close_pair(k);
 }
 
+static void test_sd_event_now(void) {
+        _cleanup_(sd_event_unrefp) sd_event *e = NULL;
+        uint64_t event_now;
+
+        assert_se(sd_event_new(&e) >= 0);
+        assert_se(sd_event_now(e, CLOCK_MONOTONIC, &event_now) > 0);
+        assert_se(sd_event_now(e, CLOCK_REALTIME, &event_now) > 0);
+        assert_se(sd_event_now(e, CLOCK_REALTIME_ALARM, &event_now) > 0);
+        assert_se(sd_event_now(e, CLOCK_BOOTTIME, &event_now) > 0);
+        assert_se(sd_event_now(e, CLOCK_BOOTTIME_ALARM, &event_now) > 0);
+        assert_se(sd_event_now(e, -1, &event_now) == -EOPNOTSUPP);
+        assert_se(sd_event_now(e, 900 /* arbitrary big number */, &event_now) == -EOPNOTSUPP);
+
+        assert_se(sd_event_run(e, 0) == 0);
+
+        assert_se(sd_event_now(e, CLOCK_MONOTONIC, &event_now) == 0);
+        assert_se(sd_event_now(e, CLOCK_REALTIME, &event_now) == 0);
+        assert_se(sd_event_now(e, CLOCK_REALTIME_ALARM, &event_now) == 0);
+        assert_se(sd_event_now(e, CLOCK_BOOTTIME, &event_now) == 0);
+        assert_se(sd_event_now(e, CLOCK_BOOTTIME_ALARM, &event_now) == 0);
+        assert_se(sd_event_now(e, -1, &event_now) == -EOPNOTSUPP);
+        assert_se(sd_event_now(e, 900 /* arbitrary big number */, &event_now) == -EOPNOTSUPP);
+}
+
 static int last_rtqueue_sigval = 0;
 static int n_rtqueue = 0;
 
@@ -324,7 +348,11 @@ static void test_rtqueue(void) {
 
 int main(int argc, char *argv[]) {
 
+        log_set_max_level(LOG_DEBUG);
+        log_parse_environment();
+
         test_basic();
+        test_sd_event_now();
         test_rtqueue();
 
         return 0;