Stability Improvements

CMakeLists.txt

@@ -8,7 +8,7 @@ include(cmake/Vcpkg.cmake) # needs to happen before project()
 
 project(
     "BeamMP-Server" # replace this
-    VERSION 3.3.0
+    VERSION 3.9.2
 )
 
 include(cmake/StandardSettings.cmake)
@@ -39,6 +39,7 @@ set(PRJ_HEADERS
     include/TConfig.h
     include/TConsole.h
     include/THeartbeatThread.h
+    include/TIoPollThread.h
     include/TLuaEngine.h
     include/TLuaPlugin.h
     include/TNetwork.h
@@ -52,6 +53,8 @@ set(PRJ_HEADERS
     include/Settings.h
     include/Profiling.h
     include/ChronoWrapper.h
+    include/TConnectionLimiter.h
+    include/TLuaResult.h
 )
 # add all source files (.cpp) to this, except the one with main()
 set(PRJ_SOURCES
@@ -65,6 +68,7 @@ set(PRJ_SOURCES
     src/TConfig.cpp
     src/TConsole.cpp
     src/THeartbeatThread.cpp
+    src/TIoPollThread.cpp
     src/TLuaEngine.cpp
     src/TLuaPlugin.cpp
     src/TNetwork.cpp
@@ -78,6 +82,8 @@ set(PRJ_SOURCES
     src/Settings.cpp
     src/Profiling.cpp
     src/ChronoWrapper.cpp
+    src/TConnectionLimiter.cpp
+    src/TLuaResult.cpp
 )
 
 find_package(Lua REQUIRED)

cmake/Vcpkg.cmake

@@ -15,3 +15,5 @@ if(NOT DEFINED CMAKE_TOOLCHAIN_FILE)
     set(CMAKE_TOOLCHAIN_FILE ${CMAKE_SOURCE_DIR}/vcpkg/scripts/buildsystems/vcpkg.cmake)
 endif()
 
+# ensure SOL2 safeties are all ON
+add_compile_definitions(SOL_ALL_SAFETIES_ON=1)

include/Client.h

@@ -18,6 +18,7 @@
 
 #pragma once
 
+#include <atomic>
 #include <chrono>
 #include <memory>
 #include <optional>
@@ -68,8 +69,11 @@ class TClient final {
     std::string GetCarPositionRaw(int Ident);
     void SetUDPAddr(const ip::udp::endpoint& Addr) { mUDPAddress = Addr; }
     void SetTCPSock(ip::tcp::socket&& CSock) { mSocket = std::move(CSock); }
-    void Disconnect(std::string_view Reason);
-    bool IsDisconnected() const { return !mSocket.is_open(); }
+    // Returns true only for the thread that actually performs socket shutdown/close.
+    [[nodiscard]] bool Disconnect(std::string_view Reason);
+    bool IsDisconnected() const {
+        return mDisconnectState.load(std::memory_order_acquire) != EDisconnectState::Connected;
+    }
     // locks
     void DeleteCar(int Ident);
     [[nodiscard]] const std::unordered_map<std::string, std::string>& GetIdentifiers() const { return mIdentifiers; }
@@ -106,6 +110,12 @@ class TClient final {
     [[nodiscard]] const std::vector<uint8_t>& GetMagic() const { return mMagic; }
 
 private:
+    enum class EDisconnectState {
+        Connected,
+        Disconnecting,
+        Disconnected
+    };
+
     void InsertVehicle(int ID, const std::string& Data);
 
     TServer& mServer;
@@ -121,6 +131,8 @@ class TClient final {
     TSetOfVehicleData mVehicleData;
     SparseArray<std::string> mVehiclePosition;
     std::string mName = "Unknown Client";
+    // Once disconnect starts, this client is terminal and its socket must be treated as dead.
+    std::atomic<EDisconnectState> mDisconnectState { EDisconnectState::Connected };
     ip::tcp::socket mSocket;
     ip::udp::endpoint mUDPAddress {};
     int mUnicycleID = -1;

include/Common.h

@@ -132,6 +132,10 @@ class Application final {
     static inline Version mVersion { 3, 9, 2 };
 };
 
+/// Used to static_assert in std::visit
+template<class>
+inline constexpr bool AlwaysFalseV = false;
+
 void SplitString(std::string const& str, const char delim, std::vector<std::string>& out);
 std::string LowerString(std::string str);
 

include/TConnectionLimiter.h

@@ -0,0 +1,90 @@
+// BeamMP, the BeamNG.drive multiplayer mod.
+// Copyright (C) 2026 BeamMP Ltd., BeamMP team and contributors.
+//
+// BeamMP Ltd. can be contacted by electronic mail via contact@beammp.com.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published
+// by the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+#pragma once
+
+#include <mutex>
+#include <optional>
+#include <string>
+#include <unordered_map>
+#include <utility>
+
+class TConnectionLimiter {
+public:
+    struct TStats {
+        size_t CurrentGlobal = 0;
+        size_t MaxGlobal = 0;
+        size_t ActiveIpBuckets = 0;
+        size_t CurrentMaxPerIp = 0;
+        size_t MaxPerIp = 0;
+        size_t SaturatedIpBuckets = 0;
+    };
+
+    class TGuard {
+    public:
+        TGuard() = default;
+        TGuard(TConnectionLimiter* owner, std::string ip);
+
+        TGuard(const TGuard&) = delete;
+        TGuard& operator=(const TGuard&) = delete;
+
+        ~TGuard() { Release(); }
+
+        // not threadsafe
+        TGuard(TGuard&& other) noexcept { *this = std::move(other); }
+        // not threadsafe
+        TGuard& operator=(TGuard&& other) noexcept;
+
+    private:
+        friend class TConnectionLimiter;
+
+        // not threadsafe
+        void Release();
+
+        TConnectionLimiter* mOwner { nullptr };
+        std::string mIp;
+    };
+
+    TConnectionLimiter(size_t maxPerIp, size_t maxGlobal);
+
+    [[nodiscard]] std::optional<TGuard> TryAcquire(const std::string& ip);
+    [[nodiscard]] TStats GetStats();
+
+private:
+    void Release(const std::string& ip) {
+        std::unique_lock Lock { mMutex };
+        auto It = mPerIp.find(ip);
+        if (It != mPerIp.end()) {
+            // this guard exists to avoid underflow in case something goes wrong and this gets called too many times
+            if (It->second > 0)
+                --It->second;
+            if (It->second == 0)
+                mPerIp.erase(It);
+        }
+        // this guard exists to avoid underflow in case something goes wrong and this gets called too many times
+        if (mGlobal > 0)
+            --mGlobal;
+    }
+
+    const size_t mMaxPerIp;
+    const size_t mMaxGlobal;
+
+    std::mutex mMutex { };
+    std::unordered_map<std::string, size_t> mPerIp { };
+    size_t mGlobal = 0;
+};

include/TIoPollThread.h

@@ -0,0 +1,36 @@
+// BeamMP, the BeamNG.drive multiplayer mod.
+// Copyright (C) 2024 BeamMP Ltd., BeamMP team and contributors.
+//
+// BeamMP Ltd. can be contacted by electronic mail via contact@beammp.com.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published
+// by the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+#pragma once
+
+#include <boost/asio/io_context.hpp>
+#include <boost/asio/executor_work_guard.hpp>
+#include <thread>
+
+class TIoPollThread {
+public:
+    TIoPollThread();
+    ~TIoPollThread();
+
+    boost::asio::io_context& IoCtx() noexcept { return mIoCtx; }
+
+private:
+    boost::asio::io_context mIoCtx;
+    boost::asio::executor_work_guard<boost::asio::io_context::executor_type> mWorkGuard;
+    std::jthread mThread;
+};

include/TLuaEngine.h

@@ -19,13 +19,12 @@
 #pragma once
 
 #include "Profiling.h"
+#include "TLuaResult.h"
 #include "TNetwork.h"
 #include "TServer.h"
-#include <any>
 #include <chrono>
 #include <condition_variable>
 #include <filesystem>
-#include <initializer_list>
 #include <list>
 #include <lua.hpp>
 #include <memory>
@@ -34,6 +33,8 @@
 #include <queue>
 #include <random>
 #include <set>
+#include <sol/forward.hpp>
+#include <sol/protected_function_result.hpp>
 #include <toml.hpp>
 #include <unordered_map>
 #include <vector>
@@ -58,36 +59,10 @@ namespace fs = std::filesystem;
 /**
  * std::variant means, that TLuaArgTypes may be one of the Types listed as template args
  */
-using TLuaValue = std::variant<std::string, int, JsonString, bool, std::unordered_map<std::string, std::string>, float>;
-enum TLuaType {
-    String = 0,
-    Int = 1,
-    Json = 2,
-    Bool = 3,
-    StringStringMap = 4,
-    Float = 5,
-};
+using TLuaValue = std::variant<std::monostate, std::string, int, JsonString, bool, std::unordered_map<std::string, std::string>, float>;
 
 class TLuaPlugin;
 
-struct TLuaResult {
-    bool Ready;
-    bool Error;
-    std::string ErrorMessage;
-    sol::object Result { sol::lua_nil };
-    TLuaStateId StateId;
-    std::string Function;
-    std::shared_ptr<std::mutex> ReadyMutex {
-        std::make_shared<std::mutex>()
-    };
-    std::shared_ptr<std::condition_variable> ReadyCondition {
-        std::make_shared<std::condition_variable>()
-    };
-
-    void MarkAsReady();
-    void WaitUntilReady();
-};
-
 struct TLuaPluginConfig {
     static inline const std::string FileName = "PluginConfig.toml";
     TLuaStateId StateId;
@@ -229,7 +204,7 @@ class TLuaEngine : public std::enable_shared_from_this<TLuaEngine>, IThreaded {
     std::unordered_map<std::string /*event name */, std::vector<std::string> /* handlers */> Debug_GetEventsForState(TLuaStateId StateId);
     std::queue<std::pair<TLuaChunk, std::shared_ptr<TLuaResult>>> Debug_GetStateExecuteQueueForState(TLuaStateId StateId);
     std::vector<QueuedFunction> Debug_GetStateFunctionQueueForState(TLuaStateId StateId);
-    std::vector<TLuaResult> Debug_GetResultsToCheckForState(TLuaStateId StateId);
+    std::vector<TLuaResult::DetachedSnapshot> Debug_GetResultsToCheckForState(TLuaStateId StateId);
 
 private:
     void CollectAndInitPlugins();