feat(Core/Movement): time synchronisation to better interpret client timestamps (#5300)

src/common/Packets/WorldPacket.h

@@ -9,6 +9,7 @@
 
 #include "Common.h"
 #include "ByteBuffer.h"
+#include "Duration.h"
 
 class WorldPacket : public ByteBuffer
 {
@@ -18,6 +19,11 @@ public:
     {
     }
     explicit WorldPacket(uint16 opcode, size_t res = 200) : ByteBuffer(res), m_opcode(opcode) { }
+
+    WorldPacket(WorldPacket&& packet, TimePoint receivedTime) : ByteBuffer(std::move(packet)), m_opcode(packet.m_opcode), m_receivedTime(receivedTime)
+    {
+    }
+
     // copy constructor
     WorldPacket(const WorldPacket& packet)              : ByteBuffer(packet), m_opcode(packet.m_opcode)
     {
@@ -39,7 +45,10 @@ public:
     [[nodiscard]] uint16 GetOpcode() const { return m_opcode; }
     void SetOpcode(uint16 opcode) { m_opcode = opcode; }
 
+    [[nodiscard]] TimePoint GetReceivedTime() const { return m_receivedTime; }
+
 protected:
     uint16 m_opcode{0};
+    TimePoint m_receivedTime; // only set for a specific set of opcodes, for performance reasons.
 };
 #endif

src/common/Utilities/CircularBuffer.h

@@ -0,0 +1,100 @@
+/*
+ * Copyright (C) 2016+ AzerothCore <www.azerothcore.org>, released under GNU AGPL v3 license: https://github.com/azerothcore/azerothcore-wotlk/blob/master/LICENSE-AGPL3
+ *
+ * This file was based on
+ * https://embeddedartistry.com/blog/2017/05/17/creating-a-circular-buffer-in-c-and-c/
+ * https://github.com/embeddedartistry/embedded-resources/blob/master/examples/cpp/circular_buffer.cpp
+ */
+
+#ifndef AZEROTHCORE_CIRCULAR_BUFFER_H
+#define AZEROTHCORE_CIRCULAR_BUFFER_H
+
+#include <memory>
+#include <mutex>
+#include <vector>
+
+template <typename T>
+class CircularBuffer {
+public:
+    explicit CircularBuffer(size_t size) :
+        buf_(std::unique_ptr<T[]>(new T[size])),
+        max_size_(size)
+    {
+
+    }
+
+    void put(T item)
+    {
+        std::lock_guard<std::mutex> lock(mutex_);
+
+        buf_[head_] = item;
+
+        if (full_)
+        {
+            tail_ = (tail_ + 1) % max_size_;
+        }
+
+        head_ = (head_ + 1) % max_size_;
+
+        full_ = head_ == tail_;
+    }
+
+    bool empty() const
+    {
+        //if head and tail are equal, we are empty
+        return (!full_ && (head_ == tail_));
+    }
+
+    bool full() const
+    {
+        //If tail is ahead the head by 1, we are full
+        return full_;
+    }
+
+    size_t capacity() const
+    {
+        return max_size_;
+    }
+
+    size_t size() const
+    {
+        size_t size = max_size_;
+
+        if (!full_)
+        {
+            if (head_ >= tail_)
+            {
+                size = head_ - tail_;
+            }
+            else
+            {
+                size += head_ - tail_;
+            }
+        }
+
+        return size;
+    }
+
+    // the implementation of this function is simplified by the fact that head_ will never be lower than tail_
+    // when compared to the original implementation of this class
+    std::vector<T> content() {
+        std::lock_guard<std::mutex> lock(mutex_);
+
+        return std::vector<T>(buf_.get(), buf_.get() + size());
+    }
+
+    T peak_back() {
+        std::lock_guard<std::mutex> lock(mutex_);
+
+        return empty() ? T() : buf_[tail_];
+    }
+
+private:
+    std::mutex mutex_;
+    std::unique_ptr<T[]> buf_;
+    size_t head_ = 0;
+    size_t tail_ = 0;
+    const size_t max_size_;
+    bool full_ = 0;
+};
+#endif

src/common/Utilities/MathUtil.h

@@ -0,0 +1,83 @@
+/*
+ * Copyright (C) 2016+ AzerothCore <www.azerothcore.org>, released under GNU AGPL v3 license: https://github.com/azerothcore/azerothcore-wotlk/blob/master/LICENSE-AGPL3
+ */
+
+#ifndef _MATH_UTIL_H
+#define _MATH_UTIL_H
+
+#include <vector>
+#include <iterator>
+#include <algorithm>
+#include <numeric>
+
+// based on https://stackoverflow.com/questions/7616511/calculate-mean-and-standard-deviation-from-a-vector-of-samples-in-c-using-boos/12405793#comment32490316_12405793
+template <typename Container, typename T = typename std::decay<decltype(*std::begin(std::declval<Container>()))>::type>
+inline T standard_deviation(Container&& c)
+{
+    auto b = std::begin(c), e = std::end(c);
+    auto size = std::distance(b, e);
+    auto sum = std::accumulate(b, e, T());
+    auto mean = sum / size;
+
+    if (size == 1)
+        return (T) 0;
+
+    T accum = T();
+    for (const auto d : c)
+        accum += (d - mean) * (d - mean);
+    return std::sqrt(accum / (size - 1));
+}
+
+
+template <typename Container, typename T = typename std::decay<decltype(*std::begin(std::declval<Container>()))>::type>
+inline T mean(Container&& c)
+{
+    auto b = std::begin(c), e = std::end(c);
+    auto size = std::distance(b, e);
+    auto sum = std::accumulate(b, e, T());
+    return sum / size;
+}
+
+// based off https://www.geeksforgeeks.org/finding-median-of-unsorted-array-in-linear-time-using-c-stl/
+template <typename T>
+inline T median(std::vector<T> a)
+{
+    size_t n = a.size();
+    // If size of the arr[] is even
+    if (n % 2 == 0) {
+
+        // Applying nth_element
+        // on n/2th index
+        std::nth_element(a.begin(),
+            a.begin() + n / 2,
+            a.end());
+
+        // Applying nth_element
+        // on (n-1)/2 th index
+        std::nth_element(a.begin(),
+            a.begin() + (n - 1) / 2,
+            a.end());
+
+        // Find the average of value at
+        // index N/2 and (N-1)/2
+        return (T)(a[(n - 1) / 2]
+            + a[n / 2])
+            / 2.0;
+    }
+
+    // If size of the arr[] is odd
+    else {
+
+        // Applying nth_element
+        // on n/2
+        std::nth_element(a.begin(),
+            a.begin() + n / 2,
+            a.end());
+
+        // Value at index (N/2)th
+        // is the median
+        return (T)a[n / 2];
+    }
+}
+
+#endif

src/server/game/Entities/Player/Player.cpp

@@ -929,11 +929,6 @@ Player::Player(WorldSession* session): Unit(true), m_mover(this)
 
     m_ChampioningFaction = 0;
 
-    m_timeSyncCounter = 0;
-    m_timeSyncTimer = 0;
-    m_timeSyncClient = 0;
-    m_timeSyncServer = 0;
-
     for (uint8 i = 0; i < MAX_POWERS; ++i)
         m_powerFraction[i] = 0;
 
@@ -1833,14 +1828,6 @@ void Player::Update(uint32 p_time)
             m_zoneUpdateTimer -= p_time;
     }
 
-    if (m_timeSyncTimer > 0)
-    {
-        if (p_time >= m_timeSyncTimer)
-            SendTimeSync();
-        else
-            m_timeSyncTimer -= p_time;
-    }
-
     if (IsAlive())
     {
         m_regenTimer += p_time;
@@ -23804,8 +23791,8 @@ void Player::SendInitialPacketsAfterAddToMap()
 {
     UpdateVisibilityForPlayer(true);
 
-    ResetTimeSync();
-    SendTimeSync();
+    GetSession()->ResetTimeSync();
+    GetSession()->SendTimeSync();
 
     CastSpell(this, 836, true);                             // LOGINEFFECT
 
@@ -27558,25 +27545,6 @@ uint8 Player::GetMostPointsTalentTree() const
     return maxIndex;
 }
 
-void Player::ResetTimeSync()
-{
-    m_timeSyncCounter = 0;
-    m_timeSyncTimer = 0;
-    m_timeSyncClient = 0;
-    m_timeSyncServer = World::GetGameTimeMS();
-}
-
-void Player::SendTimeSync()
-{
-    WorldPacket data(SMSG_TIME_SYNC_REQ, 4);
-    data << uint32(m_timeSyncCounter++);
-    GetSession()->SendPacket(&data);
-
-    // Schedule next sync in 10 sec
-    m_timeSyncTimer = 10000;
-    m_timeSyncServer = World::GetGameTimeMS();
-}
-
 void Player::SetReputation(uint32 factionentry, uint32 value)
 {
     GetReputationMgr().SetReputation(sFactionStore.LookupEntry(factionentry), value);

src/server/game/Entities/Player/Player.h

@@ -2823,9 +2823,6 @@ protected:
     ItemDurationList m_itemSoulboundTradeable;
     std::mutex m_soulboundTradableLock;
 
-    void ResetTimeSync();
-    void SendTimeSync();
-
     uint64 m_resurrectGUID;
     uint32 m_resurrectMap;
     float m_resurrectX, m_resurrectY, m_resurrectZ;
@@ -2966,11 +2963,6 @@ private:
 
     uint32 m_ChampioningFaction;
 
-    uint32 m_timeSyncCounter;
-    uint32 m_timeSyncTimer;
-    uint32 m_timeSyncClient;
-    uint32 m_timeSyncServer;
-
     InstanceTimeMap _instanceResetTimes;
     uint32 _pendingBindId;
     uint32 _pendingBindTimer;

src/server/game/Handlers/MiscHandler.cpp

@@ -1356,14 +1356,6 @@ void WorldSession::HandleSetTitleOpcode(WorldPacket& recv_data)
     GetPlayer()->SetUInt32Value(PLAYER_CHOSEN_TITLE, title);
 }
 
-void WorldSession::HandleTimeSyncResp(WorldPacket& recv_data)
-{
-    uint32 counter, clientTicks;
-    recv_data >> counter >> clientTicks;
-    //uint32 ourTicks = clientTicks + (World::GetGameTimeMS() - _player->m_timeSyncServer);
-    _player->m_timeSyncClient = clientTicks;
-}
-
 void WorldSession::HandleResetInstancesOpcode(WorldPacket& /*recv_data*/)
 {
 #if defined(ENABLE_EXTRAS) && defined(ENABLE_EXTRA_LOGS)

src/server/game/Handlers/MovementHandler.cpp

@@ -14,6 +14,7 @@
 #include "GameGraveyard.h"
 #include "InstanceSaveMgr.h"
 #include "Log.h"
+#include "MathUtil.h"
 #include "MapManager.h"
 #include "ObjectMgr.h"
 #include "Opcodes.h"
@@ -419,11 +420,6 @@ void WorldSession::HandleMovementOpcodes(WorldPacket& recvData)
     if (mover->GetGUID() != _player->GetGUID())
         movementInfo.flags &= ~MOVEMENTFLAG_WALKING;
 
-    uint32 mstime = World::GetGameTimeMS();
-    /*----------------------*/
-    if(m_clientTimeDelay == 0)
-        m_clientTimeDelay = mstime > movementInfo.time ? std::min(mstime - movementInfo.time, (uint32)100) : 0;
-
     // Xinef: do not allow to move with UNIT_FLAG_DISABLE_MOVE
     if (mover->HasFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_DISABLE_MOVE))
     {
@@ -442,8 +438,16 @@ void WorldSession::HandleMovementOpcodes(WorldPacket& recvData)
 
     /* process position-change */
     WorldPacket data(opcode, recvData.size());
-    //movementInfo.time = movementInfo.time + m_clientTimeDelay + MOVEMENT_PACKET_TIME_DELAY;
-    movementInfo.time = mstime; // pussywizard: set to time of relocation (server time), constant addition may smoothen movement clientside, but client sees target on different position than the real serverside position
+    int64 movementTime = (int64)movementInfo.time + _timeSyncClockDelta;
+    if (_timeSyncClockDelta == 0 || movementTime < 0 || movementTime > 0xFFFFFFFF)
+    {
+        LOG_INFO("misc", "The computed movement time using clockDelta is erronous. Using fallback instead");
+        movementInfo.time = getMSTime();
+    }
+    else
+    {
+        movementInfo.time = (uint32) movementTime;
+    }
 
     movementInfo.guid = mover->GetGUID();
     WriteMovementInfo(&data, &movementInfo);
@@ -796,3 +800,76 @@ void WorldSession::HandleMoveTimeSkippedOpcode(WorldPacket& recvData)
     data << timeSkipped;
     GetPlayer()->SendMessageToSet(&data, false);
 }
+
+void WorldSession::HandleTimeSyncResp(WorldPacket& recvData)
+{
+#if defined(ENABLE_EXTRAS) && defined(ENABLE_EXTRA_LOGS)
+    LOG_DEBUG("network", "CMSG_TIME_SYNC_RESP");
+#endif
+
+    uint32 counter, clientTimestamp;
+    recvData >> counter >> clientTimestamp;
+
+    if (_pendingTimeSyncRequests.count(counter) == 0)
+        return;
+
+    uint32 serverTimeAtSent = _pendingTimeSyncRequests.at(counter);
+    _pendingTimeSyncRequests.erase(counter);
+
+    // time it took for the request to travel to the client, for the client to process it and reply and for response to travel back to the server.
+    // we are going to make 2 assumptions:
+    // 1) we assume that the request processing time equals 0.
+    // 2) we assume that the packet took as much time to travel from server to client than it took to travel from client to server.
+    uint32 roundTripDuration = getMSTimeDiff(serverTimeAtSent, recvData.GetReceivedTime());
+    uint32 lagDelay = roundTripDuration / 2;
+
+    /*
+    clockDelta = serverTime - clientTime
+    where
+    serverTime: time that was displayed on the clock of the SERVER at the moment when the client processed the SMSG_TIME_SYNC_REQUEST packet.
+    clientTime:  time that was displayed on the clock of the CLIENT at the moment when the client processed the SMSG_TIME_SYNC_REQUEST packet.
+
+    Once clockDelta has been computed, we can compute the time of an event on server clock when we know the time of that same event on the client clock,
+    using the following relation:
+    serverTime = clockDelta + clientTime
+    */
+    int64 clockDelta = (int64)serverTimeAtSent + (int64)lagDelay - (int64)clientTimestamp;
+    _timeSyncClockDeltaQueue.put(std::pair<int64, uint32>(clockDelta, roundTripDuration));
+    ComputeNewClockDelta();
+}
+
+void WorldSession::ComputeNewClockDelta()
+{
+    // implementation of the technique described here: https://web.archive.org/web/20180430214420/http://www.mine-control.com/zack/timesync/timesync.html
+    // to reduce the skew induced by dropped TCP packets that get resent.
+
+    std::vector<uint32> latencies;
+    std::vector<int64> clockDeltasAfterFiltering;
+
+    for (auto pair : _timeSyncClockDeltaQueue.content())
+        latencies.push_back(pair.second);
+
+    uint32 latencyMedian = median(latencies);
+    uint32 latencyStandardDeviation = standard_deviation(latencies);
+
+    uint32 sampleSizeAfterFiltering = 0;
+    for (auto pair : _timeSyncClockDeltaQueue.content())
+    {
+        if (pair.second <= latencyMedian + latencyStandardDeviation) {
+            clockDeltasAfterFiltering.push_back(pair.first);
+            sampleSizeAfterFiltering++;
+        }
+    }
+
+    if (sampleSizeAfterFiltering != 0)
+    {
+        int64 meanClockDelta = static_cast<int64>(mean(clockDeltasAfterFiltering));
+        if (std::abs(meanClockDelta - _timeSyncClockDelta) > 25)
+            _timeSyncClockDelta = meanClockDelta;
+    }
+    else if (_timeSyncClockDelta == 0)
+    {
+        std::pair<int64, uint32> back = _timeSyncClockDeltaQueue.peak_back();
+        _timeSyncClockDelta = back.first;
+    }
+}

src/server/game/Server/Protocol/Opcodes.cpp

@@ -926,7 +926,7 @@ OpcodeHandler opcodeTable[NUM_MSG_TYPES] =
     /*0x38D*/ { "CMSG_MOVE_CHNG_TRANSPORT",                                STATUS_LOGGEDIN,   PROCESS_THREADSAFE,     &WorldSession::HandleMovementOpcodes                    },
     /*0x38E*/ { "MSG_PARTY_ASSIGNMENT",                                    STATUS_LOGGEDIN,   PROCESS_THREADUNSAFE,   &WorldSession::HandlePartyAssignmentOpcode              },
     /*0x38F*/ { "SMSG_OFFER_PETITION_ERROR",                               STATUS_NEVER,      PROCESS_INPLACE,        &WorldSession::Handle_ServerSide                        },
-    /*0x390*/ { "SMSG_TIME_SYNC_REQ",                                      STATUS_NEVER,      PROCESS_INPLACE,        &WorldSession::Handle_ServerSide                        },
+    /*0x390*/ { "SMSG_TIME_SYNC_REQ",                                      STATUS_NEVER,      PROCESS_THREADSAFE,     &WorldSession::Handle_ServerSide                        },
     /*0x391*/ { "CMSG_TIME_SYNC_RESP",                                     STATUS_LOGGEDIN,   PROCESS_INPLACE,        &WorldSession::HandleTimeSyncResp                       },
     /*0x392*/ { "CMSG_SEND_LOCAL_EVENT",                                   STATUS_NEVER,      PROCESS_INPLACE,        &WorldSession::Handle_NULL                              },
     /*0x393*/ { "CMSG_SEND_GENERAL_TRIGGER",                               STATUS_NEVER,      PROCESS_INPLACE,        &WorldSession::Handle_NULL                              },

src/server/game/Server/WorldSession.cpp

@@ -110,14 +110,16 @@ WorldSession::WorldSession(uint32 id, WorldSocket* sock, AccountTypes sec, uint8
     m_sessionDbcLocale(sWorld->GetDefaultDbcLocale()),
     m_sessionDbLocaleIndex(locale),
     m_latency(0),
-    m_clientTimeDelay(0),
     m_TutorialsChanged(false),
     recruiterId(recruiter),
     isRecruiter(isARecruiter),
     m_currentVendorEntry(0),
     m_currentBankerGUID(0),
     timeWhoCommandAllowed(0),
-    _calendarEventCreationCooldown(0)
+    _calendarEventCreationCooldown(0),
+    _timeSyncClockDeltaQueue(6),
+    _timeSyncClockDelta(0),
+    _pendingTimeSyncRequests()
 {
     memset(m_Tutorials, 0, sizeof(m_Tutorials));
 
@@ -126,6 +128,9 @@ WorldSession::WorldSession(uint32 id, WorldSocket* sock, AccountTypes sec, uint8
     _kicked = false;
     _shouldSetOfflineInDB = true;
 
+    _timeSyncNextCounter = 0;
+    _timeSyncTimer = 0;
+
     if (sock)
     {
         m_Address = sock->GetRemoteAddress();
@@ -253,7 +258,7 @@ void WorldSession::QueuePacket(WorldPacket* new_packet)
 /// Update the WorldSession (triggered by World update)
 bool WorldSession::Update(uint32 diff, PacketFilter& updater)
 {
-    if (updater.ProcessLogout())
+    if (updater.ProcessUnsafe())
     {
         UpdateTimeOutTime(diff);
 
@@ -263,7 +268,7 @@ bool WorldSession::Update(uint32 diff, PacketFilter& updater)
             m_Socket->CloseSocket("Client didn't send anything for too long");
     }
 
-    HandleTeleportTimeout(updater.ProcessLogout());
+    HandleTeleportTimeout(updater.ProcessUnsafe());
 
     uint32 _startMSTime = getMSTime();
     WorldPacket* packet = nullptr;
@@ -390,7 +395,7 @@ bool WorldSession::Update(uint32 diff, PacketFilter& updater)
     if (m_Socket && !m_Socket->IsClosed())
         ProcessQueryCallbacks();
 
-    if (updater.ProcessLogout())
+    if (updater.ProcessUnsafe())
     {
         if (m_Socket && !m_Socket->IsClosed() && _warden)
         {
@@ -415,6 +420,22 @@ bool WorldSession::Update(uint32 diff, PacketFilter& updater)
         }
     }
 
+    if (!updater.ProcessUnsafe()) // <=> updater is of type MapSessionFilter
+    {
+        // Send time sync packet every 10s.
+        if (_timeSyncTimer > 0)
+        {
+            if (diff >= _timeSyncTimer)
+            {
+                SendTimeSync();
+            }
+            else
+            {
+                _timeSyncTimer -= diff;
+            }
+        }
+    }
+
     return true;
 }
 
@@ -1648,3 +1669,22 @@ uint32 WorldSession::DosProtection::GetMaxPacketCounterAllowed(uint16 opcode) co
 
     return maxPacketCounterAllowed;
 }
+
+void WorldSession::ResetTimeSync()
+{
+    _timeSyncNextCounter = 0;
+    _pendingTimeSyncRequests.clear();
+}
+
+void WorldSession::SendTimeSync()
+{
+    WorldPacket data(SMSG_TIME_SYNC_REQ, 4);
+    data << uint32(_timeSyncNextCounter);
+    SendPacket(&data);
+
+    _pendingTimeSyncRequests[_timeSyncNextCounter] = getMSTime();
+
+    // Schedule next sync in 10 sec (except for the 2 first packets, which are spaced by only 5s)
+    _timeSyncTimer = _timeSyncNextCounter == 0 ? 5000 : 10000;
+    _timeSyncNextCounter++;
+}

src/server/game/Server/WorldSession.h

@@ -15,6 +15,7 @@
 #include "AuthDefines.h"
 #include "AddonMgr.h"
 #include "BanManager.h"
+#include "CircularBuffer.h"
 #include "Common.h"
 #include "DatabaseEnv.h"
 #include "GossipDef.h"
@@ -23,6 +24,7 @@
 #include "World.h"
 #include "WorldPacket.h"
 #include <utility>
+#include <map>
 
 class Creature;
 class GameObject;
@@ -124,7 +126,7 @@ public:
     virtual ~PacketFilter() = default;
 
     virtual bool Process(WorldPacket* /*packet*/) { return true; }
-    [[nodiscard]] virtual bool ProcessLogout() const { return true; }
+    [[nodiscard]] virtual bool ProcessUnsafe() const { return true; }
 
 protected:
     WorldSession* const m_pSession;
@@ -138,7 +140,7 @@ public:
 
     bool Process(WorldPacket* packet) override;
     //in Map::Update() we do not process player logout!
-    [[nodiscard]] bool ProcessLogout() const override { return false; }
+    [[nodiscard]] bool ProcessUnsafe() const override { return false; }
 };
 
 //class used to filer only thread-unsafe packets from queue
@@ -357,7 +359,6 @@ public:
 
     uint32 GetLatency() const { return m_latency; }
     void SetLatency(uint32 latency) { m_latency = latency; }
-    void ResetClientTimeDelay() { m_clientTimeDelay = 0; }
 
     std::atomic<time_t> m_timeOutTime;
     void UpdateTimeOutTime(uint32 diff)
@@ -387,6 +388,9 @@ public:
     time_t GetCalendarEventCreationCooldown() const { return _calendarEventCreationCooldown; }
     void SetCalendarEventCreationCooldown(time_t cooldown) { _calendarEventCreationCooldown = cooldown; }
 
+    // Time Synchronisation
+    void ResetTimeSync();
+    void SendTimeSync();
 public:                                                 // opcodes handlers
     void Handle_NULL(WorldPacket& recvPacket);          // not used
     void Handle_EarlyProccess(WorldPacket& recvPacket); // just mark packets processed in WorldSocket::OnRead
@@ -1028,7 +1032,6 @@ private:
     LocaleConstant m_sessionDbcLocale;
     LocaleConstant m_sessionDbLocaleIndex;
     uint32 m_latency;
-    uint32 m_clientTimeDelay;
     AccountData m_accountData[NUM_ACCOUNT_DATA_TYPES];
     uint32 m_Tutorials[MAX_ACCOUNT_TUTORIAL_VALUES];
     bool   m_TutorialsChanged;
@@ -1044,6 +1047,14 @@ private:
     bool _shouldSetOfflineInDB;
     // Packets cooldown
     time_t _calendarEventCreationCooldown;
+
+    CircularBuffer<std::pair<int64, uint32>> _timeSyncClockDeltaQueue; // first member: clockDelta. Second member: latency of the packet exchange that was used to compute that clockDelta.
+    int64 _timeSyncClockDelta;
+    void ComputeNewClockDelta();
+
+    std::map<uint32, uint32> _pendingTimeSyncRequests; // key: counter. value: server time when packet with that counter was sent.
+    uint32 _timeSyncNextCounter;
+    uint32 _timeSyncTimer;
 };
 #endif
 /// @}

src/server/game/Server/WorldSocket.cpp

@@ -669,15 +669,13 @@ int WorldSocket::ProcessIncoming(WorldPacket* new_pct)
         switch (opcode)
         {
             case CMSG_PING:
-                {
                 try
                 {
                     return HandlePing(*new_pct);
                 }
-                    catch (ByteBufferPositionException const&) {}
+                catch (ByteBufferPositionException const&) { }
                  LOG_ERROR("server", "WorldSocket::ReadDataHandler(): client sent malformed CMSG_PING");
                 return -1;
-                }
             case CMSG_AUTH_SESSION:
                 if (m_Session)
                 {
@@ -689,27 +687,11 @@ int WorldSocket::ProcessIncoming(WorldPacket* new_pct)
                 if (m_Session)
                     m_Session->ResetTimeOutTime(true);
                 return 0;
+            case CMSG_TIME_SYNC_RESP:
+                new_pct = new WorldPacket(std::move(*new_pct), std::chrono::steady_clock::now());
+                break;
             default:
-                {
-                    std::lock_guard<std::mutex> guard(m_SessionLock);
-
-                    if (m_Session != nullptr)
-                    {
-                        // Our Idle timer will reset on any non PING opcodes.
-                        // Catches people idling on the login screen and any lingering ingame connections.
-                        m_Session->ResetTimeOutTime(false);
-
-                        // OK, give the packet to WorldSession
-                        aptr.release();
-                        m_Session->QueuePacket (new_pct);
-                        return 0;
-                    }
-                    else
-                    {
-                        LOG_ERROR("server", "WorldSocket::ProcessIncoming: Client not authed opcode = %u", uint32(opcode));
-                        return -1;
-                    }
-                }
+                break;
         }
     }
     catch (ByteBufferException const&)
@@ -724,7 +706,25 @@ int WorldSocket::ProcessIncoming(WorldPacket* new_pct)
         return -1;
     }
 
-    ACE_NOTREACHED (return 0);
+    std::lock_guard<std::mutex> guard(m_SessionLock);
+
+    if (m_Session != nullptr)
+    {
+        // Our Idle timer will reset on any non PING or TIME_SYNC opcodes.
+        // Catches people idling on the login screen and any lingering ingame connections.
+        if (opcode != CMSG_PING && opcode != CMSG_TIME_SYNC_RESP)
+        {
+            m_Session->ResetTimeOutTime(false);
+        }
+
+        // OK, give the packet to WorldSession
+        aptr.release();
+        m_Session->QueuePacket(new_pct);
+        return 0;
+    }
+
+    LOG_ERROR("server", "WorldSocket::ProcessIncoming: Client not authed opcode = %u", uint32(opcode));
+    return -1;
 }
 
 int WorldSocket::HandleAuthSession(WorldPacket& recvPacket)
@@ -1074,7 +1074,6 @@ int WorldSocket::HandlePing(WorldPacket& recvPacket)
         if (m_Session)
         {
             m_Session->SetLatency (latency);
-            m_Session->ResetClientTimeDelay();
         }
         else
         {