core: Use real time in RealtimeSimulatorImpl::Now

CHANGES.md

@@ -28,6 +28,8 @@ This file is a best-effort approach to solving this issue; we will do our best b
 
 ### Changed behavior
 
+* (core) `RealTimeSimulatorImpl::Now` uses real time instead of the time of the last event call.
+
 ## Changes from ns-3.43 to ns-3.44
 
 ### New API

RELEASE_NOTES.md

@@ -30,6 +30,8 @@ been tested on Linux. As of this release, the latest known version to work with
 
 ### New user-visible features
 
+- (core ) !2385 - The function `Now()` will now print the real time since the beginning of the simulation instead of the real time since the last event call when `RealTimeSimulatorImpl` is used.
+
 ### Bugs fixed
 
 - (wifi) #2368 - Fix various issues related to Content Channels and RU allocation. Fixes mostly covers cases where OFDMA is used with central 26 tones, where a single user is being assigned the whole PPDU bandwidth or where a RU is larger than 20 MHz.

src/core/model/realtime-simulator-impl.cc

@@ -573,7 +573,7 @@ RealtimeSimulatorImpl::ScheduleNow(EventImpl* impl)
 Time
 RealtimeSimulatorImpl::Now() const
 {
-    return TimeStep(m_currentTs);
+    return TimeStep(m_running ? m_synchronizer->GetCurrentRealtime() : m_currentTs);
 }
 
 //