From 13ea0a98de2e51ddd4d062f1f4a0cafc95a818d5 Mon Sep 17 00:00:00 2001
From: Edmond Mondor <Hazado22@hotmail.com>
Date: Mon, 18 Sep 2023 09:41:33 -0700
Subject: [PATCH] Don't trust the local machine's system time.

Co-authored-by: Adam Johnson <AdamJohnso@gmail.com>
---
 .../plNetClient/plNetCliAgeJoiner.cpp         |  2 +-
 .../PubUtilLib/plNetClient/plNetClientMgr.cpp | 49 +++++++------------
 .../PubUtilLib/plNetClient/plNetClientMgr.h   |  5 +-
 3 files changed, 20 insertions(+), 36 deletions(-)

diff --git a/Sources/Plasma/PubUtilLib/plNetClient/plNetCliAgeJoiner.cpp b/Sources/Plasma/PubUtilLib/plNetClient/plNetCliAgeJoiner.cpp
index 6581052d..62c26dfd 100644
--- a/Sources/Plasma/PubUtilLib/plNetClient/plNetCliAgeJoiner.cpp
+++ b/Sources/Plasma/PubUtilLib/plNetClient/plNetCliAgeJoiner.cpp
@@ -211,7 +211,7 @@ void plNCAgeJoiner::Start () {
 
 	plNetClientMgr * nc = plNetClientMgr::GetInstance();
 	nc->SetFlagsBit(plNetClientMgr::kPlayingGame, false);
-	nc->fServerTimeOffset				= 0;	// reset since we're connecting to a new server
+	nc->ResetServerTimeOffset();
 	nc->fRequiredNumInitialSDLStates	= 0;
 	nc->fNumInitialSDLStates			= 0;
 	nc->SetFlagsBit(plNetClientApp::kNeedInitialAgeStateCount);
diff --git a/Sources/Plasma/PubUtilLib/plNetClient/plNetClientMgr.cpp b/Sources/Plasma/PubUtilLib/plNetClient/plNetClientMgr.cpp
index dc5d4e12..6ef1dede 100644
--- a/Sources/Plasma/PubUtilLib/plNetClient/plNetClientMgr.cpp
+++ b/Sources/Plasma/PubUtilLib/plNetClient/plNetClientMgr.cpp
@@ -133,9 +133,7 @@ plNetClientMgr::plNetClientMgr() :
 		// fProgressBar( nil ),
 		fTaskProgBar( nil ),
 		fMsgRecorder(nil),
-		fServerTimeOffset(0),
-		fTimeSamples(0),
-		fLastTimeUpdate(0),
+		fLastLocalTime(), 
 		fListenListMode(kListenList_Distance),
 		fAgeSDLObjectKey(nil),
 		fExperimentalLevel(0),
@@ -480,34 +478,23 @@ void plNetClientMgr::StartLinkInFX()
 //
 void plNetClientMgr::UpdateServerTimeOffset(plNetMessage* msg)
 {
-	if ((hsTimer::GetSysSeconds() - fLastTimeUpdate) > 5)
-	{
-		fLastTimeUpdate = hsTimer::GetSysSeconds();
-
-		const plUnifiedTime& msgSentUT = msg->GetTimeSent();
-		if (!msgSentUT.AtEpoch())
-		{
-			double diff = plUnifiedTime::GetTimeDifference(msgSentUT, plClientUnifiedTime::GetCurrentTime());
+	if (!msg->GetHasTimeSent())
+		return;
+	if (msg->GetTimeSent().AtEpoch())
+		return;
 
-			if (fServerTimeOffset == 0)
-			{
-				fServerTimeOffset = diff;
-			}
-			else
-			{
-				fServerTimeOffset = fServerTimeOffset + ((diff - fServerTimeOffset) / ++fTimeSamples);
-			}
+	double localTime = hsTimer::GetSeconds();
+	if (localTime - fLastLocalTime < 1.0)
+		return;
 
-			DebugMsg("Setting server time offset to %f", fServerTimeOffset);
-		}
-	}
+	fLastServerTime = msg->GetTimeSent();
+	fLastLocalTime = localTime;
 }
 
 void plNetClientMgr::ResetServerTimeOffset()
 {
-	fServerTimeOffset = 0;
-	fTimeSamples = 0;
-	fLastTimeUpdate = 0;
+	fLastServerTime.ToEpoch();
+	fLastLocalTime = 0.0;
 }
 
 //
@@ -515,14 +502,12 @@ void plNetClientMgr::ResetServerTimeOffset()
 //
 plUnifiedTime plNetClientMgr::GetServerTime() const 
 { 
-	if ( fServerTimeOffset==0 )		// offline mode or before connecting/calibrating to a server
+	if (fLastServerTime.AtEpoch()) {
+		WarningMsg("Someone asked for the server time, but we don't know it yet!");
 		return plUnifiedTime::GetCurrentTime();
-	
-	plUnifiedTime serverUT;
-	if (fServerTimeOffset<0)
-		return plUnifiedTime::GetCurrentTime() - plUnifiedTime(fabs(fServerTimeOffset)); 
-	else
-		return  plUnifiedTime::GetCurrentTime() + plUnifiedTime(fServerTimeOffset); 
+	}
+
+	return fLastServerTime + plUnifiedTime(hsTimer::GetSeconds() - fLastLocalTime);
 }
 
 //
diff --git a/Sources/Plasma/PubUtilLib/plNetClient/plNetClientMgr.h b/Sources/Plasma/PubUtilLib/plNetClient/plNetClientMgr.h
index 8fe246b5..a94f4f25 100644
--- a/Sources/Plasma/PubUtilLib/plNetClient/plNetClientMgr.h
+++ b/Sources/Plasma/PubUtilLib/plNetClient/plNetClientMgr.h
@@ -166,9 +166,8 @@ private:
 	std::string			fSPDesiredPlayerName;	// SP: the player we want to load from vault.
 	
 	// server info
-	double				fServerTimeOffset;		// diff between our unified time and server's unified time
-	UInt32				fTimeSamples;
-	double				fLastTimeUpdate;
+	plUnifiedTime		fLastServerTime;		// Last received time update from the server
+	double				fLastLocalTime;			// Last monotonic time (in seconds) when the above update was received
 
 	UInt8				fJoinOrder;			// returned by the server