Add sleep inside the infinite loop

Get the period and check if we are inside the reboot window
or not. If not inside the reboot window then sleep until next
period and if inside the window then reboot.

locksmithctl/daemon.go

@@ -135,8 +135,11 @@ func (r rebooter) rebootAndSleep() {
 }
 
 // lockAndReboot attempts to acquire the lock and reboot the machine in an
-// infinite loop. Returns if the reboot failed.
+// infinite loop if it is in the reboot window.
+// Returns if the reboot failed.
 func (r rebooter) lockAndReboot(lck *lock.Lock) {
+	var period *timeutil.Periodic
+
 	interval := initialInterval
 	for {
 		err := lck.Lock()
@@ -148,6 +151,46 @@ func (r rebooter) lockAndReboot(lck *lock.Lock) {
 			continue
 		}
 
+		startw := os.Getenv("LOCKSMITHD_REBOOT_WINDOW_START")
+		if startw == "" {
+			startw = os.Getenv("REBOOT_WINDOW_START")
+		}
+
+		lengthw := os.Getenv("LOCKSMITHD_REBOOT_WINDOW_LENGTH")
+		if lengthw == "" {
+			lengthw = os.Getenv("REBOOT_WINDOW_LENGTH")
+		}
+
+		if (startw == "") != (lengthw == "") {
+			dlog.Fatal("Either both or neither $REBOOT_WINDOW_START and $REBOOT_WINDOW_LENGTH must be set")
+		}
+
+		if startw != "" && lengthw != "" {
+			p, err := timeutil.ParsePeriodic(startw, lengthw)
+			if err != nil {
+				dlog.Fatalf("Error parsing reboot window: %s", err)
+			}
+
+			period = p
+		}
+
+		if period != nil {
+			dlog.Infof("Reboot window start is %q and length is %q", startw, lengthw)
+			next := period.Next(time.Now())
+			dlog.Infof("Next window begins at %s and ends at %s", next.Start, next.End)
+		} else {
+			dlog.Info("No configured reboot window")
+		}
+
+		if period != nil {
+			now := time.Now()
+			sleeptime := period.DurationToStart(now)
+			if sleeptime > 0 {
+				dlog.Infof("Waiting for %s to reboot.", sleeptime)
+				time.Sleep(sleeptime)
+			}
+		}
+
 		r.rebootAndSleep()
 		return
 	}