Core/Vehicles:

- Set MovementFlagsExtra (2) correctly depending on vehicle 'template' flags. This makes certain vehicles such as demolishers unable to jump/strafe (as intended)
- Fix SMSG_MONSTER_MOVE_TRANSPORT stucture, prevents a client crash when entering certain vehicles, as well as *properly* broadcast position relative to the vehicle.
- Send SMSG_BREAK_TARGET to player when entering vehicle.
- Set MOVEMENTFLAG_ROOT on passenger when entering vehicle
- Cleanup in affected code

src/server/game/Entities/Unit/Unit.cpp

@@ -417,22 +417,24 @@ void Unit::SendMonsterMove(float NewPosX, float NewPosY, float NewPosZ, uint32 M
 
 void Unit::SendMonsterMoveTransport(Unit *vehicleOwner)
 {
+    // TODO: Turn into BuildMonsterMoveTransport packet and allow certain variables (for npc movement aboard vehicles)
     WorldPacket data(SMSG_MONSTER_MOVE_TRANSPORT, GetPackGUID().size()+vehicleOwner->GetPackGUID().size());
     data.append(GetPackGUID());
     data.append(vehicleOwner->GetPackGUID());
     data << int8(GetTransSeat());
-    data << uint8(0);
+    data << uint8(0);   // unk boolean
     data << GetPositionX() - vehicleOwner->GetPositionX();
     data << GetPositionY() - vehicleOwner->GetPositionY();
     data << GetPositionZ() - vehicleOwner->GetPositionZ();
-    data << uint32(getMSTime());
-    data << uint8(4);
-    data << GetTransOffsetO();
+    data << uint32(100);                    // should be an increasing constant that indicates movement packet count
+    data << uint8(SPLINETYPE_FACING_ANGLE); 
+    data << GetTransOffsetO();              // facing angle?
     data << uint32(SPLINEFLAG_TRANSPORT);
-    data << uint32(0);// move time
-    data << uint32(0);//GetTransOffsetX();
-    data << uint32(0);//GetTransOffsetY();
-    data << uint32(0);//GetTransOffsetZ();
+    data << uint32(0);                      // move time
+    data << uint32(1);
+    data << uint32(GetTransOffsetX());
+    data << uint32(GetTransOffsetY());
+    data << uint32(GetTransOffsetZ());
     SendMessageToSet(&data, true);
 }
 
@@ -16610,16 +16612,20 @@ void Unit::EnterVehicle(Vehicle *vehicle, int8 seatId, bool byAura)
         return;
     }
 
+    if (Player* thisPlr = this->ToPlayer())
+    {
+        WorldPacket data(SMSG_ON_CANCEL_EXPECTED_RIDE_VEHICLE_AURA, 0);
+        thisPlr->GetSession()->SendPacket(&data);
+
+        data.Initialize(SMSG_BREAK_TARGET, 7);
+        data.append(vehicle->GetBase()->GetPackGUID());
+        thisPlr->GetSession()->SendPacket(&data);
+    }
+
     SetControlled(true, UNIT_STAT_ROOT);
     //movementInfo is set in AddPassenger
     //packets are sent in AddPassenger
 
-    if (GetTypeId() == TYPEID_PLAYER)
-    {
-        //this->ToPlayer()->SetClientControl(vehicle, 1);
-        WorldPacket data(SMSG_ON_CANCEL_EXPECTED_RIDE_VEHICLE_AURA, 0);
-        this->ToPlayer()->GetSession()->SendPacket(&data);
-    }
 }
 
 void Unit::ChangeSeat(int8 seatId, bool next, bool byAura)
@@ -16700,6 +16706,8 @@ void Unit::BuildMovementPacket(ByteBuffer *data) const
         case TYPEID_UNIT:
             if (canFly())
                 const_cast<Unit*>(this)->AddUnitMovementFlag(MOVEMENTFLAG_LEVITATING);
+            if (IsVehicle())
+                const_cast<Unit*>(this)->AddExtraUnitMovementFlag(GetVehicleKit()->GetExtraMovementFlagsForBase());
             break;
         case TYPEID_PLAYER:
             // remove unknown, unused etc flags for now
@@ -16714,6 +16722,10 @@ void Unit::BuildMovementPacket(ByteBuffer *data) const
             break;
     }
 
+    if (GetVehicle())
+        if (!this->HasUnitMovementFlag(MOVEMENTFLAG_ROOT))
+            sLog->outError("Unit does not have MOVEMENTFLAG_ROOT but is in vehicle!");
+
     *data << uint32(GetUnitMovementFlags()); // movement flags
     *data << uint16(m_movementInfo.flags2);    // 2.3.0
     *data << uint32(getMSTime());            // time

src/server/game/Entities/Unit/Unit.h

@@ -675,7 +675,7 @@ enum MovementFlags2
     MOVEMENTFLAG2_NONE                     = 0x00000000,
     MOVEMENTFLAG2_NO_STRAFE                = 0x00000001,
     MOVEMENTFLAG2_NO_JUMPING               = 0x00000002,
-    MOVEMENTFLAG2_UNK3                     = 0x00000004,
+    MOVEMENTFLAG2_UNK3                     = 0x00000004,        // Overrides various clientside checks
     MOVEMENTFLAG2_FULL_SPEED_TURNING       = 0x00000008,
     MOVEMENTFLAG2_FULL_SPEED_PITCHING      = 0x00000010,
     MOVEMENTFLAG2_ALWAYS_ALLOW_PITCHING    = 0x00000020,
@@ -1949,6 +1949,12 @@ class Unit : public WorldObject
         uint32 GetUnitMovementFlags() const { return m_movementInfo.flags; }
         void SetUnitMovementFlags(uint32 f) { m_movementInfo.flags = f; }
 
+        void AddExtraUnitMovementFlag(uint16 f) { m_movementInfo.flags2 |= f; }
+        void RemoveExtraUnitMovementFlag(uint16 f) { m_movementInfo.flags2 &= ~f; }
+        uint16 HasExtraUnitMovementFlag(uint16 f) const { return m_movementInfo.flags2 & f; }
+        uint16 GetExtraUnitMovementFlags() const { return m_movementInfo.flags2; }
+        void SetExtraUnitMovementFlags(uint16 f) { m_movementInfo.flags2 = f; }
+
         void SetControlled(bool apply, UnitState state);
 
         void AddComboPointHolder(uint32 lowguid) { m_ComboPointHolders.insert(lowguid); }