Context fill-in and CI tests

This commit adds common units tests and CI sanitasion.
Additional context for commit b64d9c4498:
 - Fixed macOS/Linux non-portable and unsafe shell usage by adding a posix_spawn helper and replacing system() calls in virtual_interface.cpp.
 - Fixed SessionRegistry::erase() to remove mIPSessions and mSessionIPs entries in session_registry.cpp.
 - Prevented message-length truncation in tcp_message_handler.cpp by rejecting payloads > 65535 bytes.
 - Validated handshake message sizes and removed silent truncation in:
  - tcp_connection.cpp
  - tcp_client.cpp
 - Canonicalized and validated config and whitelist paths in utils.cpp using std::filesystem.
 - Hardened environment-provided config path handling in main.cpp.
 - Validated UDP ciphertext lengths and fixed session ID endianness in udp_client.cpp.
 - Scheduled periodic SessionRegistry::cleanupExpired() in main.cpp (every 5 minutes).

.github/workflows/sanitizers.yml

@@ -0,0 +1,39 @@
+name: Sanitizers
+
+on:
+  push:
+    branches: [ main, master ]
+  pull_request:
+    branches: [ main, master ]
+
+jobs:
+  build-and-test:
+    runs-on: ubuntu-latest
+    env:
+      SANITIZERS: "-fsanitize=address,undefined -fno-omit-frame-pointer -g -O1"
+      ASAN_OPTIONS: "detect_leaks=1:abort_on_error=1"
+      UBSAN_OPTIONS: "print_stacktrace=1"
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Install dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y cmake build-essential clang
+
+      - name: Configure (CMake)
+        run: |
+          mkdir -p build-sanitizers
+          cd build-sanitizers
+          CC=clang CXX=clang++ cmake -DCMAKE_BUILD_TYPE=Debug -DCMAKE_CXX_FLAGS="$SANITIZERS" -DCMAKE_EXE_LINKER_FLAGS="$SANITIZERS" ..
+
+      - name: Build
+        run: |
+          cd build-sanitizers
+          cmake --build . -- -j
+
+      - name: Run tests
+        run: |
+          cd build-sanitizers
+          ctest --output-on-failure || (echo "ctest failed"; exit 1)

.gitignore

@@ -12,5 +12,6 @@ _deps
 CMakeUserPresets.json
 
 build/
+build*/
 .vscode/
 .DS_Store

CMakeLists.txt

@@ -6,7 +6,7 @@ cmake_minimum_required(VERSION 3.16)
 # If MAJOR is 0, and MINOR > 0, Version is BETA
 
 project(ColumnLynx
-    VERSION 1.0.1
+    VERSION 1.1.1
     LANGUAGES CXX
 )
 
@@ -173,3 +173,28 @@ install(FILES
 	LICENSES/GPL-2.0-only.txt
 	LICENSES/GPL-3.0.txt
         DESTINATION ${CMAKE_INSTALL_DATAROOTDIR}/licenses/${PROJECT_NAME})
+
+# ---------------------------------------------------------
+# Unit tests
+# ---------------------------------------------------------
+option(BUILD_TESTS "Build unit tests" ON)
+
+if(BUILD_TESTS)
+    enable_testing()
+    file(GLOB_RECURSE TEST_SRC CONFIGURE_DEPENDS tests/*.cpp)
+    if(TEST_SRC)
+        foreach(TEST_FILE IN LISTS TEST_SRC)
+            get_filename_component(TEST_NAME ${TEST_FILE} NAME_WE)
+            add_executable(${TEST_NAME} ${TEST_FILE})
+            target_link_libraries(${TEST_NAME} PRIVATE common sodium)
+            target_include_directories(${TEST_NAME} PRIVATE 
+                ${PROJECT_SOURCE_DIR}/include
+                ${asio_SOURCE_DIR}/asio/include
+                ${sodium_SOURCE_DIR}/src/libsodium/include
+                ${sodium_BINARY_DIR}/src/libsodium/include
+            )
+            add_test(NAME ${TEST_NAME} COMMAND ${TEST_NAME})
+            set_target_properties(${TEST_NAME} PROPERTIES OUTPUT_NAME "columnlynx_${TEST_NAME}")
+        endforeach()
+    endif()
+endif()

README.md

@@ -213,6 +213,8 @@ ColumnLynx makes use of both **TCP** and **UDP**. **TCP** is used for the initia
 
 It operates on port **48042** for both TCP and UDP.
 
+Current protocol version is **2**.
+
 Generally, all transmission is done in **little-endian byte order**, since pretty much every single modern architecture uses it by default. The only exemption to this is the **transmission of IP addresses** (for the **Virtual Interface**), which is **big-endian**.
 
 ### Handshake Procedure
@@ -231,7 +233,7 @@ The Client now generates a random aesKey (32 bytes long)
 
 C: HANDSHAKE_EXCHANGE_KEY <aesKey Encrypted with Server Public Key>
 
-The Server now assigns a local 8 byte session ID in the Session Registry.
+The Server now assigns a local 4 byte session ID in the Session Registry.
 
 S: HANDSHAKE_EXCHANGE_KEY_CONFIRM <Assigned SessionID>
 ```
@@ -242,7 +244,7 @@ The **Client** and **Server** have now securely exchanged a symmetric **AES Key*
 
 Packet exchange and the general data tunneling is done via **Standard UDP** (*see the **UDP Packet** in **Data***).
 
-The **header** of the sent packet always includes a **random 12 byte nonce** used to obscure the **encrypted payload / data** and the **Session ID** assigned by the server to the client (8 bytes). This makes the header **20 bytes long**.
+The **header** of the sent packet always includes a **12 byte nonce** derived from a random **4 byte base nonce** and the **send count** to ensure a unique nonce, used to obscure the **encrypted payload / data** and the **Session ID** assigned by the server to the client (4 bytes). This makes the header **16 bytes long**.
 
 The **payload / data** of the sent packet is **always encrypted** using the exchanged **AES Key** and obscured using the **random nonce**.
 
@@ -298,7 +300,7 @@ The **Data** is generally just the **raw underlying packet** forwarded to the se
 | Type | Length | Name | Description |
 |:-----|:-------|:-----|:------------|
 | uint8_t | 12 bytes | **Header** - Nonce | Random nonce to obfuscate encrypted contents |
-| uint64_t | 8 bytes | **Header** - Session ID | The unique and random session identifier for the client |
+| uint32_t | 4 bytes | **Header** - Session ID | The unique and random session identifier for the client |
 | uint8_t | variable | Data | General data / payload |
 
 ## Misc.

include/columnlynx/client/client_session.hpp

@@ -0,0 +1,106 @@
+// client_session.hpp - Client Session data for ColumnLynx
+// Copyright (C) 2026 DcruBro
+// Distributed under the terms of the GNU General Public License, either version 2 only or version 3. See LICENSES/ for details.
+
+#pragma once
+
+#include <memory>
+#include <columnlynx/common/libsodium_wrapper.hpp>
+#include <array>
+#include <columnlynx/common/net/virtual_interface.hpp>
+#include <shared_mutex>
+
+namespace ColumnLynx {
+    struct ClientState {
+        std::shared_ptr<Utils::LibSodiumWrapper> sodiumWrapper;
+        SymmetricKey aesKey;
+        bool insecureMode;
+        std::string configPath;
+        std::shared_ptr<Net::VirtualInterface> virtualInterface;
+        uint32_t sessionID;
+        uint64_t recv_cnt;
+        uint64_t send_cnt;
+        uint32_t noncePrefix;
+
+        ~ClientState() { sodium_memzero(aesKey.data(), aesKey.size()); }
+        ClientState(const ClientState&) = delete;
+        ClientState& operator=(const ClientState&) = delete;
+        ClientState(ClientState&&) = default;
+        ClientState& operator=(ClientState&&) = default;
+
+        explicit ClientState() = default;
+
+        explicit ClientState(std::shared_ptr<Utils::LibSodiumWrapper> sodium, SymmetricKey& k, bool insecure,
+                     std::string& config, std::shared_ptr<Net::VirtualInterface> tun, uint32_t session, uint64_t recv, uint64_t send)
+        : sodiumWrapper(sodium), aesKey(k), insecureMode(insecure), configPath(config), virtualInterface(tun), sessionID(session), recv_cnt(recv), send_cnt(send) {}
+    };
+    
+    class ClientSession {
+        public:
+            // Return a reference to the Client Session instance
+            static ClientSession& getInstance() { static ClientSession instance; return instance; }
+
+            // Return the current client state
+            std::shared_ptr<ClientState> getClientState() const;
+
+            // Set the client state
+            void setClientState(std::shared_ptr<ClientState> state);
+
+            // Get the wrapper for libsodium
+            const std::shared_ptr<Utils::LibSodiumWrapper>& getSodiumWrapper() const;
+            // Get the AES key
+            const SymmetricKey& getAESKey() const;
+            // Get whether insecure mode is enabled
+            bool isInsecureMode() const;
+            // Get the config path
+            const std::string& getConfigPath() const;
+            // Get the virtual interface
+            const std::shared_ptr<Net::VirtualInterface>& getVirtualInterface() const;
+            // Get the session ID
+            uint32_t getSessionID() const;
+            uint64_t getRecvCount() const {
+                std::shared_lock lock(mMutex);
+                return mClientState->recv_cnt;
+            }
+
+            uint64_t getSendCount() const {
+                std::shared_lock lock(mMutex);
+                return mClientState->send_cnt;
+            }
+
+            uint32_t getNoncePrefix() const {
+                std::shared_lock lock(mMutex);
+                return mClientState->noncePrefix;
+            }
+
+            // Setters
+            void setSodiumWrapper(std::shared_ptr<Utils::LibSodiumWrapper> sodiumWrapper);
+            void setAESKey(const SymmetricKey& aesKey);
+            void setInsecureMode(bool insecureMode);
+            void setConfigPath(const std::string& configPath);
+            void setVirtualInterface(std::shared_ptr<Net::VirtualInterface> virtualInterface);
+            void setSessionID(uint32_t sessionID);
+            void incrementRecvCount() {
+                std::unique_lock lock(mMutex);
+                mClientState->recv_cnt++;
+            }
+
+            void incrementSendCount() {
+                std::unique_lock lock(mMutex);
+                if (mClientState->send_cnt == std::numeric_limits<uint64_t>::max()) {
+                    Utils::error("ClientSession: send counter overflow detected");
+                    return;
+                }
+                mClientState->send_cnt++;
+            }
+
+            void setNoncePrefix(uint32_t prefix) {
+                std::unique_lock lock(mMutex);
+                mClientState->noncePrefix = prefix;
+            }
+
+        private:
+            mutable std::shared_mutex mMutex;
+            std::shared_ptr<struct ClientState> mClientState{nullptr};
+    };
+}

include/columnlynx/client/net/tcp/tcp_client.hpp

@@ -11,12 +11,14 @@
 #include <columnlynx/common/utils.hpp>
 #include <columnlynx/common/libsodium_wrapper.hpp>
 #include <array>
+#include <atomic>
 #include <algorithm>
 #include <vector>
 #include <unordered_map>
 #include <string>
 #include <columnlynx/common/net/protocol_structs.hpp>
 #include <columnlynx/common/net/virtual_interface.hpp>
+#include <columnlynx/client/client_session.hpp>
 
 using asio::ip::tcp;
 
@@ -25,28 +27,20 @@ namespace ColumnLynx::Net::TCP {
         public:
             TCPClient(asio::io_context& ioContext,
                       const std::string& host,
-                      const std::string& port,
+                      const std::string& port)
-                      std::shared_ptr<Utils::LibSodiumWrapper> sodiumWrapper,
-                      std::shared_ptr<std::array<uint8_t, 32>> aesKey,
-                      std::shared_ptr<uint64_t> sessionIDRef,
-                      bool insecureMode,
-                      std::string& configPath,
-                      std::shared_ptr<VirtualInterface> tun = nullptr)
                 :
                 mResolver(ioContext),
                 mSocket(ioContext),
                 mHost(host),
                 mPort(port),
-                mLibSodiumWrapper(sodiumWrapper),
-                mGlobalKeyRef(aesKey),
-                mSessionIDRef(sessionIDRef),
-                mInsecureMode(insecureMode),
                 mHeartbeatTimer(mSocket.get_executor()),
                 mLastHeartbeatReceived(std::chrono::steady_clock::now()),
-                mLastHeartbeatSent(std::chrono::steady_clock::now()),
+                mLastHeartbeatSent(std::chrono::steady_clock::now())
-                mTun(tun),
-                mConfigDirPath(configPath)
             {
+                // Get initial client config
+                std::string configPath = ClientSession::getInstance().getConfigPath();
+                std::shared_ptr<Utils::LibSodiumWrapper> mLibSodiumWrapper = ClientSession::getInstance().getSodiumWrapper();
+
                 // Preload the config map
                 mRawClientConfig = Utils::getConfigMap(configPath + "client_config");
 
@@ -96,28 +90,22 @@ namespace ColumnLynx::Net::TCP {
 
             // TODO: Move ptrs to smart ptrs
 
-            bool mConnected = false;
+            std::atomic<bool> mConnected{false};
-            bool mHandshakeComplete = false;
+            std::atomic<bool> mHandshakeComplete{false};
             tcp::resolver mResolver;
             tcp::socket mSocket;
             std::shared_ptr<MessageHandler> mHandler;
             std::string mHost, mPort;
             uint8_t mServerPublicKey[32]; // Assuming 256-bit public key
             std::array<uint8_t, 32> mSubmittedChallenge{};
-            std::shared_ptr<Utils::LibSodiumWrapper> mLibSodiumWrapper;
+            uint32_t mConnectionSessionID;
-            uint64_t mConnectionSessionID;
             SymmetricKey mConnectionAESKey;
-            std::shared_ptr<std::array<uint8_t, 32>> mGlobalKeyRef; // Reference to global AES key
-            std::shared_ptr<uint64_t> mSessionIDRef; // Reference to global Session ID
-            bool mInsecureMode; // Insecure mode flag
             asio::steady_timer mHeartbeatTimer;
             std::chrono::steady_clock::time_point mLastHeartbeatReceived;
             std::chrono::steady_clock::time_point mLastHeartbeatSent;
             int mMissedHeartbeats = 0;
             bool mIsHostDomain;
             Protocol::TunConfig mTunConfig;
-            std::shared_ptr<VirtualInterface> mTun = nullptr;
             std::unordered_map<std::string, std::string> mRawClientConfig;
-            std::string mConfigDirPath;
     };
 }

include/columnlynx/client/net/udp/udp_client.hpp

@@ -10,17 +10,15 @@
 #include <columnlynx/common/libsodium_wrapper.hpp>
 #include <array>
 #include <columnlynx/common/net/virtual_interface.hpp>
+#include <columnlynx/client/client_session.hpp>
 
 namespace ColumnLynx::Net::UDP {
     class UDPClient {
         public:
             UDPClient(asio::io_context& ioContext,
                       const std::string& host,
-                      const std::string& port,
+                      const std::string& port)
-                      std::shared_ptr<std::array<uint8_t, 32>> aesKeyRef,
+                : mSocket(ioContext), mResolver(ioContext), mHost(host), mPort(port)
-                      std::shared_ptr<uint64_t> sessionIDRef,
-                      std::shared_ptr<VirtualInterface> tunRef = nullptr)
-                : mSocket(ioContext), mResolver(ioContext), mHost(host), mPort(port), mAesKeyRef(aesKeyRef), mSessionIDRef(sessionIDRef), mTunRef(tunRef) 
             {
                 mStartReceive(); 
             }
@@ -43,9 +41,6 @@ namespace ColumnLynx::Net::UDP {
             asio::ip::udp::endpoint mRemoteEndpoint;
             std::string mHost;
             std::string mPort;
-            std::shared_ptr<std::array<uint8_t, 32>> mAesKeyRef;
-            std::shared_ptr<uint64_t> mSessionIDRef;
-            std::shared_ptr<VirtualInterface> mTunRef = nullptr;
             std::array<uint8_t, 2048> mRecvBuffer; // Adjust size as needed
     };
 }

include/columnlynx/common/net/session_registry.hpp

@@ -27,8 +27,9 @@ namespace ColumnLynx::Net {
         std::chrono::steady_clock::time_point expires{}; // Time of expiry
         uint32_t clientTunIP; // Assigned IP
         uint32_t serverTunIP; // Server IP
-        uint64_t sessionID; // Session ID
+        uint32_t sessionID; // Session ID
         Nonce base_nonce{};
+        uint32_t noncePrefix;
 
         ~SessionState() { sodium_memzero(aesKey.data(), aesKey.size()); }
         SessionState(const SessionState&) = delete;
@@ -36,7 +37,7 @@ namespace ColumnLynx::Net {
         SessionState(SessionState&&) = default;
         SessionState& operator=(SessionState&&) = default;
 
-        explicit SessionState(const SymmetricKey& k, std::chrono::seconds ttl = std::chrono::hours(24), uint32_t clientIP = 0, uint32_t serverIP = 0, uint64_t id = 0) : aesKey(k), clientTunIP(clientIP), serverTunIP(serverIP), sessionID(id) {
+        explicit SessionState(const SymmetricKey& k, std::chrono::seconds ttl = std::chrono::hours(24), uint32_t clientIP = 0, uint32_t serverIP = 0, uint32_t id = 0) : aesKey(k), clientTunIP(clientIP), serverTunIP(serverIP), sessionID(id) {
             expires = created + ttl;
         }
 
@@ -44,6 +45,11 @@ namespace ColumnLynx::Net {
         void setUDPEndpoint(const asio::ip::udp::endpoint& ep) {
             udpEndpoint = ep;
         }
+
+        void setBaseNonce() {
+            Utils::debug("Generating random base nonce for session " + std::to_string(sessionID));
+            randombytes_buf(base_nonce.data(), base_nonce.size());
+        }
     };
 
     class SessionRegistry {
@@ -52,19 +58,19 @@ namespace ColumnLynx::Net {
             static SessionRegistry& getInstance() { static SessionRegistry instance; return instance; }
 
             // Insert or replace a session entry
-            void put(uint64_t sessionID, std::shared_ptr<SessionState> state);
+            void put(uint32_t sessionID, std::shared_ptr<SessionState> state);
 
             // Lookup a session entry by session ID
-            std::shared_ptr<const SessionState> get(uint64_t sessionID) const;
+            std::shared_ptr<const SessionState> get(uint32_t sessionID) const;
 
             // Lookup a session entry by IPv4
             std::shared_ptr<const SessionState> getByIP(uint32_t ip) const;
 
             // Get a snapshot of the Session Registry
-            std::unordered_map<uint64_t, std::shared_ptr<SessionState>> snapshot() const;
+            std::unordered_map<uint32_t, std::shared_ptr<SessionState>> snapshot() const;
 
             // Remove a session by ID
-            void erase(uint64_t sessionID);
+            void erase(uint32_t sessionID);
 
             // Cleanup expired sessions
             void cleanupExpired();
@@ -72,21 +78,23 @@ namespace ColumnLynx::Net {
             // Get the number of registered sessions
             int size() const;
 
+            bool exists(uint32_t sessionID) const;
+
             // IP management
 
             // Get the lowest available IPv4 address; Returns 0 if none available
             uint32_t getFirstAvailableIP(uint32_t baseIP, uint8_t mask) const;
 
             // Lock IP to session ID; Do NOT call before put() - You will segfault!
-            void lockIP(uint64_t sessionID, uint32_t ip);
+            void lockIP(uint32_t sessionID, uint32_t ip);
 
             // Unlock IP from session ID
-            void deallocIP(uint64_t sessionID);
+            void deallocIP(uint32_t sessionID);
 
         private:
             mutable std::shared_mutex mMutex;
-            std::unordered_map<uint64_t, std::shared_ptr<SessionState>> mSessions;
+            std::unordered_map<uint32_t, std::shared_ptr<SessionState>> mSessions;
-            std::unordered_map<uint64_t, uint32_t> mSessionIPs;
+            std::unordered_map<uint32_t, uint32_t> mSessionIPs;
             std::unordered_map<uint32_t, std::shared_ptr<SessionState>> mIPSessions;
     };
 }

include/columnlynx/common/net/tcp/tcp_message_handler.hpp

@@ -39,6 +39,6 @@ namespace ColumnLynx::Net::TCP {
             std::array<uint8_t, 3> mHeader{}; // [type][lenHigh][lenLow]
             std::vector<uint8_t> mBody;
             std::function<void(AnyMessageType, std::string)> mOnMessage;
-            std::function<void(asio::error_code&)> mOnDisconnect;
+            std::function<void(const asio::error_code&)> mOnDisconnect;
     };
 }

include/columnlynx/common/utils.hpp

@@ -15,7 +15,7 @@
 #include <unordered_map>
 #include <unordered_set>
 #include <algorithm>
-#include <bits/stdc++.h>
+
 
 #ifdef _WIN32
     #include <winsock2.h>
@@ -65,27 +65,6 @@ namespace ColumnLynx::Utils {
         return std::string(reinterpret_cast<const char*>(data), length);
     }
 
-    inline constexpr uint64_t cbswap64(uint64_t x) {
-        return ((x & 0x00000000000000FFULL) << 56) |
-               ((x & 0x000000000000FF00ULL) << 40) |
-               ((x & 0x0000000000FF0000ULL) << 24) |
-               ((x & 0x00000000FF000000ULL) << 8)  |
-               ((x & 0x000000FF00000000ULL) >> 8)  |
-               ((x & 0x0000FF0000000000ULL) >> 24) |
-               ((x & 0x00FF000000000000ULL) >> 40) |
-               ((x & 0xFF00000000000000ULL) >> 56);
-    }
-
-    // host -> big-endian (for little-endian hosts) - 64 bit
-    inline constexpr uint64_t chtobe64(uint64_t x) {
-        return cbswap64(x);
-    }
-
-    // big-endian -> host (for little-endian hosts) - 64 bit
-    inline constexpr uint64_t cbe64toh(uint64_t x) {
-        return cbswap64(x);
-    }
-
     template <typename T>
     T cbswap128(const T& x) {
         static_assert(sizeof(T) == 16, "cbswap128 requires a 128-bit type");

include/columnlynx/server/net/tcp/tcp_connection.hpp

@@ -18,6 +18,7 @@
 #include <columnlynx/common/net/session_registry.hpp>
 #include <columnlynx/common/net/protocol_structs.hpp>
 #include <columnlynx/common/net/virtual_interface.hpp>
+#include <columnlynx/server/server_session.hpp>
 
 namespace ColumnLynx::Net::TCP {
     class TCPConnection : public std::enable_shared_from_this<TCPConnection> {
@@ -26,12 +27,9 @@ namespace ColumnLynx::Net::TCP {
 
             static pointer create(
                 asio::ip::tcp::socket socket,
-                std::shared_ptr<Utils::LibSodiumWrapper> sodiumWrapper,
-                std::unordered_map<std::string, std::string>* serverConfig,
-                std::string configDirPath,
                 std::function<void(pointer)> onDisconnect)
             {
-                auto conn = pointer(new TCPConnection(std::move(socket), sodiumWrapper, serverConfig, configDirPath));
+                auto conn = pointer(new TCPConnection(std::move(socket)));
                 conn->mOnDisconnect = std::move(onDisconnect);
                 return conn;
             }
@@ -46,20 +44,17 @@ namespace ColumnLynx::Net::TCP {
             void disconnect(bool echo = true);
 
             // Get the assigned session ID
-            uint64_t getSessionID() const;
+            uint32_t getSessionID() const;
             // Get the assigned AES key; You should probably access this via the Session Registry instead
             std::array<uint8_t, 32> getAESKey() const;
         
         private:
-            TCPConnection(asio::ip::tcp::socket socket, std::shared_ptr<Utils::LibSodiumWrapper> sodiumWrapper, std::unordered_map<std::string, std::string>* serverConfig, std::string configDirPath)
+            TCPConnection(asio::ip::tcp::socket socket)
                 :
                 mHandler(std::make_shared<MessageHandler>(std::move(socket))),
-                mLibSodiumWrapper(sodiumWrapper),
-                mRawServerConfig(serverConfig),
                 mHeartbeatTimer(mHandler->socket().get_executor()),
                 mLastHeartbeatReceived(std::chrono::steady_clock::now()),
-                mLastHeartbeatSent(std::chrono::steady_clock::now()),
+                mLastHeartbeatSent(std::chrono::steady_clock::now())
-                mConfigDirPath(configDirPath)
             {}
 
             // Start the heartbeat routine
@@ -69,16 +64,13 @@ namespace ColumnLynx::Net::TCP {
 
             std::shared_ptr<MessageHandler> mHandler;
             std::function<void(std::shared_ptr<TCPConnection>)> mOnDisconnect;
-            std::shared_ptr<Utils::LibSodiumWrapper> mLibSodiumWrapper;
-            std::unordered_map<std::string, std::string>* mRawServerConfig;
             std::array<uint8_t, 32> mConnectionAESKey;
-            uint64_t mConnectionSessionID;
+            uint32_t mConnectionSessionID;
             AsymPublicKey mConnectionPublicKey;
             asio::steady_timer mHeartbeatTimer;
             std::chrono::steady_clock::time_point mLastHeartbeatReceived;
             std::chrono::steady_clock::time_point mLastHeartbeatSent;
             int mMissedHeartbeats = 0;
             std::string mRemoteIP; // Cached remote IP to avoid calling remote_endpoint() on closed sockets
-            std::string mConfigDirPath;
     };
 }

include/columnlynx/server/net/tcp/tcp_server.hpp

@@ -17,29 +17,23 @@
 #include <columnlynx/server/net/tcp/tcp_connection.hpp>
 #include <columnlynx/common/libsodium_wrapper.hpp>
 #include <columnlynx/common/net/protocol_structs.hpp>
+#include <columnlynx/server/server_session.hpp>
 
 namespace ColumnLynx::Net::TCP {
 
     class TCPServer {
         public:
             TCPServer(asio::io_context& ioContext,
-                      uint16_t port,
+                      uint16_t port)
-                      std::shared_ptr<Utils::LibSodiumWrapper> sodiumWrapper,
-                      std::shared_ptr<bool> hostRunning,
-                      std::string& configPath,
-                      bool ipv4Only = false)
                 : mIoContext(ioContext),
-                  mAcceptor(ioContext),
+                  mAcceptor(ioContext)
-                  mSodiumWrapper(sodiumWrapper),
-                  mHostRunning(hostRunning),
-                  mConfigDirPath(configPath)
             {
                 // Preload the config map
-                mRawServerConfig = Utils::getConfigMap(configPath + "server_config", {"NETWORK", "SUBNET_MASK"});
-
                 asio::error_code ec_open, ec_v6only, ec_bind;
 
-                if (!ipv4Only) {
+                bool isIPv4Only = ServerSession::getInstance().isIPv4Only();
+
+                if (!isIPv4Only) {
                     // Try IPv6 (dual-stack if supported)
                     asio::ip::tcp::endpoint endpoint_v6(asio::ip::tcp::v6(), port);
                 
@@ -55,8 +49,8 @@ namespace ColumnLynx::Net::TCP {
                 }
                 
                 // If IPv6 bind failed OR IPv6 open failed OR forced IPv4-only
-                if (ipv4Only || ec_open || ec_bind) {
+                if (isIPv4Only || ec_open || ec_bind) {
-                    if (!ipv4Only)
+                    if (!isIPv4Only)
                         Utils::warn("TCP: IPv6 unavailable (open=" + ec_open.message() +
                                     ", bind=" + ec_bind.message() +
                                     "), falling back to IPv4 only");
@@ -84,10 +78,6 @@ namespace ColumnLynx::Net::TCP {
             asio::io_context &mIoContext;
             asio::ip::tcp::acceptor mAcceptor;
             std::unordered_set<TCPConnection::pointer> mClients;
-            std::shared_ptr<Utils::LibSodiumWrapper> mSodiumWrapper;
-            std::shared_ptr<bool> mHostRunning;
-            std::unordered_map<std::string, std::string> mRawServerConfig;
-            std::string mConfigDirPath;
     };
 
 }

include/columnlynx/server/net/udp/udp_server.hpp

@@ -9,16 +9,18 @@
 #include <columnlynx/common/utils.hpp>
 #include <array>
 #include <columnlynx/common/net/virtual_interface.hpp>
+#include <columnlynx/common/libsodium_wrapper.hpp>
+#include <columnlynx/server/server_session.hpp>
 
 namespace ColumnLynx::Net::UDP {
     class UDPServer {
         public:
-            UDPServer(asio::io_context& ioContext, uint16_t port, std::shared_ptr<bool> hostRunning, bool ipv4Only = false, std::shared_ptr<VirtualInterface> tun = nullptr)
+            UDPServer(asio::io_context& ioContext, uint16_t port)
-                : mSocket(ioContext), mHostRunning(hostRunning), mTun(tun)
+                : mSocket(ioContext)
             {
                 asio::error_code ec_open, ec_v6only, ec_bind;
 
-                if (!ipv4Only) {
+                if (!mIpv4Only) {
                     asio::ip::udp::endpoint endpoint_v6(asio::ip::udp::v6(), port);
                 
                     // Try opening IPv6 socket
@@ -34,8 +36,8 @@ namespace ColumnLynx::Net::UDP {
                 }
 
                 // Fallback to IPv4 if IPv6 is unusable
-                if (ipv4Only || ec_open || ec_bind) {
+                if (mIpv4Only || ec_open || ec_bind) {
-                    if (!ipv4Only) {
+                    if (!mIpv4Only) {
                         Utils::warn(
                             "UDP: IPv6 unavailable (open=" + ec_open.message() +
                             ", bind=" + ec_bind.message() +
@@ -59,7 +61,7 @@ namespace ColumnLynx::Net::UDP {
             void stop();
 
             // Send UDP data to an endpoint; Fetched via the Session Registry
-            void sendData(const uint64_t sessionID, const std::string& data);
+            void sendData(uint32_t sessionID, const std::string& data);
 
         private:
             // Start receiving UDP data
@@ -70,7 +72,7 @@ namespace ColumnLynx::Net::UDP {
             asio::ip::udp::socket mSocket;
             asio::ip::udp::endpoint mRemoteEndpoint;
             std::array<uint8_t, 2048> mRecvBuffer; // 2048 seems stable
-            std::shared_ptr<bool> mHostRunning;
+            bool mIpv4Only = ServerSession::getInstance().isIPv4Only();
-            std::shared_ptr<VirtualInterface> mTun;
+            const std::shared_ptr<VirtualInterface> mTun = ServerSession::getInstance().getVirtualInterface();
     };
 }

include/columnlynx/server/server_session.hpp

@@ -0,0 +1,62 @@
+// server_session.hpp - Client Session data for ColumnLynx
+// Copyright (C) 2026 DcruBro
+// Distributed under the terms of the GNU General Public License, either version 2 only or version 3. See LICENSES/ for details.
+
+#pragma once
+
+#include <memory>
+#include <columnlynx/common/libsodium_wrapper.hpp>
+#include <array>
+#include <columnlynx/common/net/virtual_interface.hpp>
+#include <shared_mutex>
+
+namespace ColumnLynx {
+    struct ServerState {
+        std::shared_ptr<Utils::LibSodiumWrapper> sodiumWrapper;
+        std::shared_ptr<Net::VirtualInterface> virtualInterface;
+        std::string configPath;
+        std::unordered_map<std::string, std::string> serverConfig;
+        bool ipv4Only;
+        bool hostRunning;
+
+        ~ServerState() = default;
+        ServerState(const ServerState&) = delete;
+        ServerState& operator=(const ServerState&) = delete;
+        ServerState(ServerState&&) = default;
+        ServerState& operator=(ServerState&&) = default;
+
+        explicit ServerState() = default;
+    };
+    
+    class ServerSession {
+        public:
+            // Return a reference to the Server Session instance
+            static ServerSession& getInstance() { static ServerSession instance; return instance; }
+
+            // Return the current server state
+            std::shared_ptr<ServerState> getServerState() const;
+
+            // Set the server state
+            void setServerState(std::shared_ptr<ServerState> state);
+
+            // Getters
+            std::shared_ptr<Utils::LibSodiumWrapper> getSodiumWrapper() const;
+            const std::string& getConfigPath() const;
+            const std::unordered_map<std::string, std::string>& getRawServerConfig() const;
+            const std::shared_ptr<Net::VirtualInterface>& getVirtualInterface() const;
+            bool isIPv4Only() const;
+            bool isHostRunning() const;
+
+            // Setters
+            void setSodiumWrapper(std::shared_ptr<Utils::LibSodiumWrapper> sodiumWrapper);
+            void setConfigPath(const std::string& configPath);
+            void setRawServerConfig(const std::unordered_map<std::string, std::string>& config);
+            void setVirtualInterface(std::shared_ptr<Net::VirtualInterface> tun);
+            void setIPv4Only(bool ipv4Only);
+            void setHostRunning(bool hostRunning);
+
+        private:
+            mutable std::shared_mutex mMutex;
+            std::shared_ptr<struct ServerState> mServerState{nullptr};
+    };
+}

src/client/client_session.cpp

@@ -0,0 +1,71 @@
+// client_session.cpp - Client Session data for ColumnLynx
+// Copyright (C) 2026 DcruBro
+// Distributed under the terms of the GNU General Public License, either version 2 only or version 3. See LICENSES/ for details.
+
+#include <columnlynx/client/client_session.hpp>
+
+namespace ColumnLynx {
+    std::shared_ptr<ClientState> ClientSession::getClientState() const {
+        std::shared_lock lock(mMutex);
+        return mClientState;
+    }
+
+    void ClientSession::setClientState(std::shared_ptr<ClientState> state) {
+        std::unique_lock lock(mMutex);
+        mClientState = state;
+    }
+
+    const std::shared_ptr<Utils::LibSodiumWrapper>& ClientSession::getSodiumWrapper() const {
+        return getClientState()->sodiumWrapper;
+    }
+
+    const SymmetricKey& ClientSession::getAESKey() const {
+        return getClientState()->aesKey;
+    }
+
+    bool ClientSession::isInsecureMode() const {
+        return getClientState()->insecureMode;
+    }
+
+    const std::string& ClientSession::getConfigPath() const {
+        return getClientState()->configPath;
+    }
+
+    const std::shared_ptr<Net::VirtualInterface>& ClientSession::getVirtualInterface() const {
+        return getClientState()->virtualInterface;
+    }
+
+    uint32_t ClientSession::getSessionID() const {
+        return getClientState()->sessionID;
+    }
+
+    void ClientSession::setSodiumWrapper(std::shared_ptr<Utils::LibSodiumWrapper> sodiumWrapper) {
+        std::unique_lock lock(mMutex);
+        mClientState->sodiumWrapper = sodiumWrapper;
+    }
+
+    void ClientSession::setAESKey(const SymmetricKey& aesKey) {
+        std::unique_lock lock(mMutex);
+        mClientState->aesKey = aesKey;
+    }
+
+    void ClientSession::setInsecureMode(bool insecureMode) {
+        std::unique_lock lock(mMutex);
+        mClientState->insecureMode = insecureMode;
+    }
+
+    void ClientSession::setConfigPath(const std::string& configPath) {
+        std::unique_lock lock(mMutex);
+        mClientState->configPath = configPath;
+    }
+
+    void ClientSession::setVirtualInterface(std::shared_ptr<Net::VirtualInterface> virtualInterface) {
+        std::unique_lock lock(mMutex);
+        mClientState->virtualInterface = virtualInterface;
+    }
+
+    void ClientSession::setSessionID(uint32_t sessionID) {
+        std::unique_lock lock(mMutex);
+        mClientState->sessionID = sessionID;
+    }
+}

src/client/main.cpp

@@ -5,12 +5,15 @@
 #include <asio.hpp>
 #include <csignal>
 #include <iostream>
+#include <filesystem>
 #include <columnlynx/common/utils.hpp>
 #include <columnlynx/common/panic_handler.hpp>
 #include <columnlynx/client/net/tcp/tcp_client.hpp>
 #include <columnlynx/client/net/udp/udp_client.hpp>
 #include <cxxopts.hpp>
 #include <columnlynx/common/net/virtual_interface.hpp>
+#include <columnlynx/client/client_session.hpp>
+#include <thread>
 
 #if defined(__WIN32__)
 #include <windows.h>
@@ -88,7 +91,20 @@ int main(int argc, char** argv) {
         std::string configPath = optionsObj["config-dir"].as<std::string>();
         const char* envConfigPath = std::getenv("COLUMNLYNX_CONFIG_DIR");
         if (envConfigPath != nullptr) {
-            configPath = std::string(envConfigPath);
+            // Validate and canonicalize environment-provided path
+            try {
+                namespace fs = std::filesystem;
+                std::error_code ec;
+                fs::path candidate(envConfigPath);
+                fs::path abs = fs::absolute(candidate, ec);
+                if (!ec) {
+                    configPath = abs.string();
+                } else {
+                    warn(std::string("Invalid COLUMNLYNX_CONFIG_DIR value: ") + envConfigPath + " - using default");
+                }
+            } catch (const std::exception& e) {
+                warn(std::string("Failed to canonicalize COLUMNLYNX_CONFIG_DIR: ") + e.what());
+            }
         }
 
         if (configPath.back() != '/' && configPath.back() != '\\') {
@@ -99,24 +115,37 @@ int main(int argc, char** argv) {
             #endif
         }
 
+        struct ClientState initialState{};
+        initialState.configPath = configPath;
+        initialState.insecureMode = insecureMode;
+        initialState.send_cnt = 0;
+        initialState.recv_cnt = 0;
+        randombytes_buf(&initialState.noncePrefix, sizeof(uint32_t)); // Randomize nonce prefix
+
         std::shared_ptr<VirtualInterface> tun = std::make_shared<VirtualInterface>(optionsObj["interface"].as<std::string>());
         log("Using virtual interface: " + tun->getName());
+        initialState.virtualInterface = tun;
 
         std::shared_ptr<LibSodiumWrapper> sodiumWrapper = std::make_shared<LibSodiumWrapper>();
         debug("Public Key: " + Utils::bytesToHexString(sodiumWrapper->getPublicKey(), 32));
         debug("Private Key: " + Utils::bytesToHexString(sodiumWrapper->getPrivateKey(), 64));
+        initialState.sodiumWrapper = sodiumWrapper;
 
-        std::shared_ptr<std::array<uint8_t, 32>> aesKey = std::make_shared<std::array<uint8_t, 32>>(); 
+        std::array<uint8_t, 32> aesKey = std::array<uint8_t, 32>(); 
-        aesKey->fill(0); // Defualt zeroed state until modified by handshake
+        aesKey.fill(0); // Defualt zeroed state until modified by handshake
-        std::shared_ptr<uint64_t> sessionID = std::make_shared<uint64_t>(0);
+        uint32_t sessionID = 0;
+        initialState.aesKey = aesKey;
+        initialState.sessionID = sessionID;
+
+        ColumnLynx::ClientSession::getInstance().setClientState(std::make_shared<ClientState>(std::move(initialState))); // Set initial state
 
         if (insecureMode) {
             warn("You have started the client with the --ignore-whitelist. This means that the client will NOT attempt to verify the server's public key. This is INSECURE and SHOULDN'T be used!");
         }
 
         asio::io_context io;
-        auto client = std::make_shared<ColumnLynx::Net::TCP::TCPClient>(io, host, port, sodiumWrapper, aesKey, sessionID, insecureMode, configPath, tun);
+        auto client = std::make_shared<ColumnLynx::Net::TCP::TCPClient>(io, host, port); // TODO: Move to ClientSession state
-        auto udpClient = std::make_shared<ColumnLynx::Net::UDP::UDPClient>(io, host, port, aesKey, sessionID, tun);
+        auto udpClient = std::make_shared<ColumnLynx::Net::UDP::UDPClient>(io, host, port);
 
         client->start();
         udpClient->start();

src/client/net/tcp/tcp_client.cpp

@@ -14,19 +14,25 @@ namespace ColumnLynx::Net::TCP {
                     asio::async_connect(mSocket, endpoints,
                         [this, self](asio::error_code ec, const tcp::endpoint&) {
                             if (!ec) {
-                                mConnected = true;
+                                mConnected.store(true, std::memory_order_relaxed);
                                 Utils::log("Client connected.");
                                 mHandler = std::make_shared<MessageHandler>(std::move(mSocket));
-                                mHandler->onMessage([this](AnyMessageType type, const std::string& data) {
+                                mHandler->onMessage([weakSelf = weak_from_this()](AnyMessageType type, const std::string& data) {
-                                    mHandleMessage(static_cast<ServerMessageType>(MessageHandler::toUint8(type)), data);
+                                    if (auto self = weakSelf.lock()) {
+                                        self->mHandleMessage(static_cast<ServerMessageType>(MessageHandler::toUint8(type)), data);
+                                    }
                                 });
                                 // Close only after peer FIN to avoid RSTs
-                                mHandler->onDisconnect([this](const asio::error_code& ec) {
+                                mHandler->onDisconnect([weakSelf = weak_from_this()](const asio::error_code& ec) {
-                                    asio::error_code ec2;
+                                    auto self = weakSelf.lock();
-                                    if (mHandler) {
+                                    if (!self) {
-                                        mHandler->socket().close(ec2);
+                                        return;
                                     }
-                                    mConnected = false;
+                                    asio::error_code ec2;
+                                    if (self->mHandler) {
+                                        self->mHandler->socket().close(ec2);
+                                    }
+                                    self->mConnected.store(false, std::memory_order_relaxed);
                                     Utils::log(std::string("Server disconnected: ") + ec.message());
                                 });
                                 mHandler->start();
@@ -46,10 +52,13 @@ namespace ColumnLynx::Net::TCP {
                                 std::vector<uint8_t> payload;
                                 payload.reserve(1 + crypto_box_PUBLICKEYBYTES);
                                 payload.push_back(Utils::protocolVersion());
+                                Utils::log("Using protocol version: " + std::to_string(Utils::protocolVersion()));
                                 /*payload.insert(payload.end(),
                                     mLibSodiumWrapper->getXPublicKey(),
                                     mLibSodiumWrapper->getXPublicKey() + crypto_box_PUBLICKEYBYTES
                                 );*/
+
+                                const auto& mLibSodiumWrapper = ClientSession::getInstance().getSodiumWrapper();
                                 payload.insert(payload.end(),
                                     mLibSodiumWrapper->getPublicKey(),
                                     mLibSodiumWrapper->getPublicKey() + crypto_sign_PUBLICKEYBYTES
@@ -71,7 +80,7 @@ namespace ColumnLynx::Net::TCP {
     }
 
     void TCPClient::sendMessage(ClientMessageType type, const std::string& data) {
-        if (!mConnected) {
+        if (!mConnected.load(std::memory_order_relaxed)) {
             Utils::error("Cannot send message, client not connected.");
             return;
         }
@@ -84,7 +93,7 @@ namespace ColumnLynx::Net::TCP {
     }
 
     void TCPClient::disconnect(bool echo) {
-        if (mConnected && mHandler) {
+        if (mConnected.load(std::memory_order_relaxed) && mHandler) {
             if (echo) {
                 mHandler->sendMessage(ClientMessageType::GRACEFUL_DISCONNECT, "Goodbye");
             }
@@ -104,17 +113,17 @@ namespace ColumnLynx::Net::TCP {
     }
 
     bool TCPClient::isHandshakeComplete() const {
-        return mHandshakeComplete;
+        return mHandshakeComplete.load(std::memory_order_relaxed);
     }
 
     bool TCPClient::isConnected() const {
-        return mConnected;
+        return mConnected.load(std::memory_order_relaxed);
     }
 
     void TCPClient::mStartHeartbeat() {
         auto self = shared_from_this();
         mHeartbeatTimer.expires_after(std::chrono::seconds(5));
-        mHeartbeatTimer.async_wait([this, self](const asio::error_code& ec) {
+        mHeartbeatTimer.async_wait([self](const asio::error_code& ec) {
             if (ec == asio::error::operation_aborted) {
                 return; // Timer was cancelled
             }
@@ -127,14 +136,14 @@ namespace ColumnLynx::Net::TCP {
                 
                 // Close sockets forcefully, server is dead
                 asio::error_code ec;
-                mHandler->socket().shutdown(tcp::socket::shutdown_both, ec);
+                if (self->mHandler) {
-                mHandler->socket().close(ec);
+                    self->mHandler->socket().shutdown(tcp::socket::shutdown_both, ec);
-                mConnected = false;
+                    self->mHandler->socket().close(ec);
-
-                mGlobalKeyRef = nullptr;
-                if (mSessionIDRef) {
-                    *mSessionIDRef = 0;
                 }
+                self->mConnected.store(false, std::memory_order_relaxed);
+                
+                ClientSession::getInstance().setAESKey({}); // Clear AES key with all zeros
+                ClientSession::getInstance().setSessionID(0);
 
                 return;
             }
@@ -150,14 +159,21 @@ namespace ColumnLynx::Net::TCP {
     void TCPClient::mHandleMessage(ServerMessageType type, const std::string& data) {
         switch (type) {
             case ServerMessageType::HANDSHAKE_IDENTIFY: {
-                    std::memcpy(mServerPublicKey, data.data(), std::min(data.size(), sizeof(mServerPublicKey)));
+                    if (data.size() != sizeof(mServerPublicKey)) {
+                        Utils::warn("HANDSHAKE_IDENTIFY has invalid size: " + std::to_string(data.size()));
+                        disconnect();
+                        return;
+                    }
+
+                    std::memcpy(mServerPublicKey, data.data(), sizeof(mServerPublicKey));
                     std::string hexServerPub = Utils::bytesToHexString(mServerPublicKey, 32);
                     Utils::log("Received server identity. Public Key: " + hexServerPub);
 
                     // Verify pubkey against whitelisted_keys
-                    std::vector<std::string> whitelistedKeys = Utils::getWhitelistedKeys(mConfigDirPath);
+                    const std::string& configPath = ClientSession::getInstance().getConfigPath();
+                    std::vector<std::string> whitelistedKeys = Utils::getWhitelistedKeys(configPath);
                     if (std::find(whitelistedKeys.begin(), whitelistedKeys.end(), Utils::bytesToHexString(mServerPublicKey, 32)) == whitelistedKeys.end()) { // Key verification is handled in later steps of the handshake
-                        if (!mInsecureMode) {
+                        if (!ClientSession::getInstance().isInsecureMode()) {
                             Utils::error("Server public key not in whitelisted_keys. Terminating connection.");
                             disconnect();
                             return;
@@ -178,7 +194,13 @@ namespace ColumnLynx::Net::TCP {
                 {
                     // Verify the signature
                     Signature sig{};
-                    std::memcpy(sig.data(), data.data(), std::min(data.size(), sig.size()));
+                    if (data.size() != sig.size()) {
+                        Utils::warn("HANDSHAKE_CHALLENGE_RESPONSE has invalid size: " + std::to_string(data.size()));
+                        disconnect();
+                        return;
+                    }
+
+                    std::memcpy(sig.data(), data.data(), sig.size());
                     if (Utils::LibSodiumWrapper::verifyMessage(mSubmittedChallenge.data(), mSubmittedChallenge.size(), sig, mServerPublicKey)) {
                         Utils::log("Challenge response verified successfully.");
                         
@@ -193,16 +215,14 @@ namespace ColumnLynx::Net::TCP {
 
                         // Generate AES key and send confirmation
                         mConnectionAESKey = Utils::LibSodiumWrapper::generateRandom256Bit();
-                        if (mGlobalKeyRef) { // Copy to the global reference
+                        ClientSession::getInstance().setAESKey(mConnectionAESKey);
-                            std::copy(mConnectionAESKey.begin(), mConnectionAESKey.end(), mGlobalKeyRef->begin());
-                        }
                         AsymNonce nonce{};
                         randombytes_buf(nonce.data(), nonce.size());
 
                         // TODO: This is pretty redundant, it should return the required type directly
                         std::array<uint8_t, 32> arrayPrivateKey;
-                        std::copy(mLibSodiumWrapper->getXPrivateKey(),
+                        std::copy(ClientSession::getInstance().getSodiumWrapper()->getXPrivateKey(),
-                                  mLibSodiumWrapper->getXPrivateKey() + 32,
+                                  ClientSession::getInstance().getSodiumWrapper()->getXPrivateKey() + 32,
                                   arrayPrivateKey.begin());
 
                         std::vector<uint8_t> encr = Utils::LibSodiumWrapper::encryptAsymmetric(
@@ -245,24 +265,23 @@ namespace ColumnLynx::Net::TCP {
                     std::memcpy(&mConnectionSessionID, decrypted.data(), sizeof(mConnectionSessionID));
                     std::memcpy(&mTunConfig, decrypted.data() + sizeof(mConnectionSessionID), sizeof(Protocol::TunConfig));
 
-                    mConnectionSessionID = Utils::cbe64toh(mConnectionSessionID);
+                    mConnectionSessionID = ntohl(mConnectionSessionID);
 
                     Utils::log("Connection established with Session ID: " + std::to_string(mConnectionSessionID));
                 
-                    if (mSessionIDRef) { // Copy to the global reference
+                    ClientSession::getInstance().setSessionID(mConnectionSessionID);
-                        *mSessionIDRef = mConnectionSessionID;
-                    }
 
                     uint32_t clientIP = ntohl(mTunConfig.clientIP);
                     uint32_t serverIP = ntohl(mTunConfig.serverIP);
                     uint8_t prefixLen = mTunConfig.prefixLength;
                     uint16_t mtu = mTunConfig.mtu;
 
+                    const auto& mTun = ClientSession::getInstance().getVirtualInterface();
                     if (mTun) {
                         mTun->configureIP(clientIP, serverIP, prefixLen, mtu);
                     }
 
-                    mHandshakeComplete = true;
+                    mHandshakeComplete.store(true, std::memory_order_relaxed);
                 }
             
                 break;
@@ -277,13 +296,13 @@ namespace ColumnLynx::Net::TCP {
                 break;
             case ServerMessageType::GRACEFUL_DISCONNECT:
                 Utils::log("Server is disconnecting: " + data);
-                if (mConnected) { // Prevent Recursion
+                if (mConnected.load(std::memory_order_relaxed)) { // Prevent Recursion
                     disconnect(false);
                 }
                 break;
             case ServerMessageType::KILL_CONNECTION:
                 Utils::warn("Server is killing the connection: " + data);
-                if (mConnected) {
+                if (mConnected.load(std::memory_order_relaxed)) {
                     disconnect(false);
                 }
                 break;

src/client/net/udp/udp_client.cpp

@@ -3,6 +3,8 @@
 // Distributed under the terms of the GNU General Public License, either version 2 only or version 3. See LICENSES/ for details.
 
 #include <columnlynx/client/net/udp/udp_client.hpp>
+#include <thread>
+#include <chrono>
 
 namespace ColumnLynx::Net::UDP {
     void UDPClient::start() {
@@ -46,9 +48,14 @@ namespace ColumnLynx::Net::UDP {
 
     void UDPClient::sendMessage(const std::string& data) {
         UDPPacketHeader hdr{};
-        randombytes_buf(hdr.nonce.data(), hdr.nonce.size());
+        uint8_t nonce[12];
+        uint32_t prefix = ClientSession::getInstance().getNoncePrefix();
+        uint64_t sendCount = ClientSession::getInstance().getSendCount();
+        memcpy(nonce, &prefix, sizeof(uint32_t)); // Prefix nonce with client-specific random value
+        memcpy(nonce + sizeof(uint32_t), &sendCount, sizeof(uint64_t)); // Use send count as nonce suffix to ensure uniqueness
+        std::copy_n(nonce, 12, hdr.nonce.data());
 
-        if (mAesKeyRef == nullptr || mSessionIDRef == nullptr) {
+        if (ClientSession::getInstance().getAESKey().empty() || ClientSession::getInstance().getSessionID() == 0) {
             Utils::error("UDP Client AES key or Session ID reference is null!");
             return;
         }
@@ -57,24 +64,28 @@ namespace ColumnLynx::Net::UDP {
 
         auto encryptedPayload = Utils::LibSodiumWrapper::encryptMessage(
             reinterpret_cast<const uint8_t*>(data.data()), data.size(),
-            *mAesKeyRef, hdr.nonce, "udp-data"
+            ClientSession::getInstance().getAESKey(), hdr.nonce, "udp-data"
             //std::string(reinterpret_cast<const char*>(&mSessionIDRef), sizeof(uint64_t))
         );
 
         std::vector<uint8_t> packet;
-        packet.reserve(sizeof(UDPPacketHeader) + sizeof(uint64_t) + encryptedPayload.size());
+        packet.reserve(sizeof(UDPPacketHeader) + encryptedPayload.size());
         packet.insert(packet.end(), 
             reinterpret_cast<uint8_t*>(&hdr),
             reinterpret_cast<uint8_t*>(&hdr) + sizeof(UDPPacketHeader)
         );
+        uint32_t sessionID = static_cast<uint32_t>(ClientSession::getInstance().getSessionID());
+        uint32_t sessionIDNet = htonl(sessionID);
         packet.insert(packet.end(),
-            reinterpret_cast<uint8_t*>(mSessionIDRef.get()),
+            reinterpret_cast<uint8_t*>(&sessionIDNet),
-            reinterpret_cast<uint8_t*>(mSessionIDRef.get()) + sizeof(uint64_t)
+            reinterpret_cast<uint8_t*>(&sessionIDNet) + sizeof(uint32_t)
         );
         packet.insert(packet.end(), encryptedPayload.begin(), encryptedPayload.end());
 
         mSocket.send_to(asio::buffer(packet), mRemoteEndpoint);
         Utils::debug("Sent UDP packet of size " + std::to_string(packet.size()));
+
+        ClientSession::getInstance().incrementSendCount();
     }
 
     void UDPClient::stop() {
@@ -93,7 +104,12 @@ namespace ColumnLynx::Net::UDP {
                 if (ec) {
                     if (ec == asio::error::operation_aborted) return; // Socket closed
                     // Other recv error
-                    mStartReceive();
+                    Utils::warn("UDPClient receive error: " + ec.message());
+                    // Back off briefly before restarting receive to avoid busy error loops
+                    asio::post(mSocket.get_executor(), [this]() {
+                        std::this_thread::sleep_for(std::chrono::milliseconds(50));
+                        mStartReceive();
+                    });
                     return;
                 }
 
@@ -107,7 +123,7 @@ namespace ColumnLynx::Net::UDP {
     }
 
     void UDPClient::mHandlePacket(std::size_t bytes) {
-        if (bytes < sizeof(UDPPacketHeader) + sizeof(uint64_t)) {
+        if (bytes < sizeof(UDPPacketHeader) + sizeof(uint32_t)) {
             Utils::warn("UDP Client received packet too small to process.");
             return;
         }
@@ -117,27 +133,43 @@ namespace ColumnLynx::Net::UDP {
         std::memcpy(&hdr, mRecvBuffer.data(), sizeof(UDPPacketHeader));
 
         // Parse session ID
-        uint64_t sessionID;
+        uint32_t sessionIDNet;
-        std::memcpy(&sessionID, mRecvBuffer.data() + sizeof(UDPPacketHeader), sizeof(uint64_t));
+        std::memcpy(&sessionIDNet, mRecvBuffer.data() + sizeof(UDPPacketHeader), sizeof(uint32_t));
+        uint32_t sessionID = ntohl(sessionIDNet);
 
-        if (sessionID != *mSessionIDRef) {
+        if (sessionID != ClientSession::getInstance().getSessionID()) {
-            Utils::warn("Got packet that isn't for me! Dropping!");
+            Utils::warn("This packet that isn't for me! Dropping!");
             return;
         }
 
         // Decrypt payload
+        // Extract ciphertext safely
+        size_t headerLen = sizeof(UDPPacketHeader) + sizeof(uint32_t);
+        if (bytes < headerLen) {
+            Utils::warn("UDP Client received packet too small after header check.");
+            return;
+        }
+
+        size_t ciphertextLen = bytes - headerLen;
+        // Enforce reasonable maximum (UDP payload practical limit)
+        const size_t MAX_UDP_PAYLOAD = 65507; // 65535 - UDP/IP headers
+        if (ciphertextLen > MAX_UDP_PAYLOAD) {
+            Utils::warn("UDP Client received packet with excessive payload size: " + std::to_string(ciphertextLen));
+            return;
+        }
+
         std::vector<uint8_t> ciphertext(
-            mRecvBuffer.begin() + sizeof(UDPPacketHeader) + sizeof(uint64_t),
+            mRecvBuffer.begin() + headerLen,
-            mRecvBuffer.begin() + bytes
+            mRecvBuffer.begin() + headerLen + ciphertextLen
         );
 
-        if (mAesKeyRef == nullptr) {
+        if (ClientSession::getInstance().getAESKey().empty()) {
             Utils::error("UDP Client AES key reference is null!");
             return;
         }
 
         std::vector<uint8_t> plaintext = Utils::LibSodiumWrapper::decryptMessage(
-            ciphertext.data(), ciphertext.size(), *mAesKeyRef, hdr.nonce, "udp-data"
+            ciphertext.data(), ciphertext.size(), ClientSession::getInstance().getAESKey(), hdr.nonce, "udp-data"
             //std::string(reinterpret_cast<const char*>(&mSessionIDRef), sizeof(uint64_t))
         );
 
@@ -149,6 +181,7 @@ namespace ColumnLynx::Net::UDP {
         Utils::debug("UDP Client received packet from " + mRemoteEndpoint.address().to_string() + " - Packet size: " + std::to_string(bytes));
 
         // Write to TUN
+        const auto& mTunRef = ClientSession::getInstance().getVirtualInterface();
         if (mTunRef) {
             mTunRef->writePacket(plaintext);
         }

src/common/session_registry.cpp

@@ -5,13 +5,13 @@
 #include <columnlynx/common/net/session_registry.hpp>
 
 namespace ColumnLynx::Net {
-    void SessionRegistry::put(uint64_t sessionID, std::shared_ptr<SessionState> state) {
+    void SessionRegistry::put(uint32_t sessionID, std::shared_ptr<SessionState> state) {
         std::unique_lock lock(mMutex);
         mSessions[sessionID] = std::move(state);
         mIPSessions[mSessions[sessionID]->clientTunIP] = mSessions[sessionID];
     }
 
-    std::shared_ptr<const SessionState> SessionRegistry::get(uint64_t sessionID) const {
+    std::shared_ptr<const SessionState> SessionRegistry::get(uint32_t sessionID) const {
         std::shared_lock lock(mMutex);
         auto it = mSessions.find(sessionID);
         return (it == mSessions.end()) ? nullptr : it->second;
@@ -23,16 +23,35 @@ namespace ColumnLynx::Net {
         return (it == mIPSessions.end()) ? nullptr : it->second;
     }
 
-    std::unordered_map<uint64_t, std::shared_ptr<SessionState>> SessionRegistry::snapshot() const {
+    std::unordered_map<uint32_t, std::shared_ptr<SessionState>> SessionRegistry::snapshot() const {
-        std::unordered_map<uint64_t, std::shared_ptr<SessionState>> snap;
+        std::unordered_map<uint32_t, std::shared_ptr<SessionState>> snap;
         std::shared_lock lock(mMutex);
         snap = mSessions;
         return snap;
     }
 
-    void SessionRegistry::erase(uint64_t sessionID) {
+    void SessionRegistry::erase(uint32_t sessionID) {
         std::unique_lock lock(mMutex);
-        mSessions.erase(sessionID);
+        auto it = mSessions.find(sessionID);
+        if (it != mSessions.end()) {
+            // If the session has a client IP mapping, remove it to avoid stale entries
+            if (it->second) {
+                uint32_t ip = it->second->clientTunIP;
+                auto ipIt = mIPSessions.find(ip);
+                if (ipIt != mIPSessions.end()) {
+                    // Only erase if it points to the same session
+                    if (ipIt->second == it->second) {
+                        mIPSessions.erase(ipIt);
+                    }
+                }
+            }
+
+            // Remove any session->ip bookkeeping
+            mSessionIPs.erase(sessionID);
+
+            // Finally erase the session
+            mSessions.erase(it);
+        }
     }
 
     void SessionRegistry::cleanupExpired() {
@@ -60,6 +79,11 @@ namespace ColumnLynx::Net {
         return static_cast<int>(mSessions.size());
     }
 
+    bool SessionRegistry::exists(uint32_t sessionID) const {
+        std::shared_lock lock(mMutex);
+        return mSessions.find(sessionID) != mSessions.end();
+    }
+    
     uint32_t SessionRegistry::getFirstAvailableIP(uint32_t baseIP, uint8_t mask) const {
         std::shared_lock lock(mMutex);
 
@@ -77,17 +101,21 @@ namespace ColumnLynx::Net {
         return 0;
     }
 
-    void SessionRegistry::lockIP(uint64_t sessionID, uint32_t ip) {
+    void SessionRegistry::lockIP(uint32_t sessionID, uint32_t ip) {
         std::unique_lock lock(mMutex);
         mSessionIPs[sessionID] = ip;
 
-        /*if (mIPSessions.find(sessionID) == mIPSessions.end()) {
+        auto it = mSessions.find(sessionID);
-            Utils::debug("yikes");
+        if (it == mSessions.end() || !it->second) {
-        }*/
+            Utils::warn("SessionRegistry::lockIP called for unknown session " + std::to_string(sessionID));
-        mIPSessions[ip] = mSessions.find(sessionID)->second;
+            mSessionIPs.erase(sessionID);
+            return;
+        }
+
+        mIPSessions[ip] = it->second;
     }
 
-    void SessionRegistry::deallocIP(uint64_t sessionID) {
+    void SessionRegistry::deallocIP(uint32_t sessionID) {
         std::unique_lock lock(mMutex);
     
         auto it = mSessionIPs.find(sessionID);

src/common/tcp_message_handler.cpp

@@ -5,6 +5,7 @@
 #include <columnlynx/common/net/tcp/tcp_message_handler.hpp>
 #include <columnlynx/common/net/tcp/net_helper.hpp>
 #include <columnlynx/common/utils.hpp>
+#include <memory>
 
 namespace ColumnLynx::Net::TCP {
     void MessageHandler::start() {
@@ -17,17 +18,23 @@ namespace ColumnLynx::Net::TCP {
             return static_cast<uint8_t>(type);
         }, type);
 
-        std::vector<uint8_t> data;
+        auto data = std::make_shared<std::vector<uint8_t>>();
-        data.push_back(typeByte);
+        data->push_back(typeByte);
-        uint16_t length = payload.size();
+        // Ensure payload fits into protocol's 16-bit length field
+        if (payload.size() > static_cast<size_t>(std::numeric_limits<uint16_t>::max())) {
+            Utils::error("sendMessage(): payload too large (>65535 bytes)");
+            return;
+        }
 
-        data.push_back(length >> 8);
+        uint16_t length = static_cast<uint16_t>(payload.size());
-        data.push_back(length & 0xFF);
 
-        data.insert(data.end(), payload.begin(), payload.end());
+        data->push_back(static_cast<uint8_t>(length >> 8));
+        data->push_back(static_cast<uint8_t>(length & 0xFF));
+
+        data->insert(data->end(), payload.begin(), payload.end());
         auto self = shared_from_this();
-        asio::async_write(mSocket, asio::buffer(data),
+        asio::async_write(mSocket, asio::buffer(*data),
-            [self](asio::error_code ec, std::size_t) {
+            [self, data](asio::error_code ec, std::size_t) {
                 if (ec) {
                     Utils::error("Send failed: " + ec.message());
                 }

src/common/utils.cpp

@@ -3,6 +3,7 @@
 // Distributed under the terms of the GNU General Public License, either version 2 only or version 3. See LICENSES/ for details.
 
 #include <columnlynx/common/utils.hpp>
+#include <filesystem>
 
 namespace ColumnLynx::Utils {
     std::string unixMillisToISO8601(uint64_t unixMillis, bool local) {
@@ -85,7 +86,7 @@ namespace ColumnLynx::Utils {
     }
 
     std::string getVersion() {
-        return "1.0.1";
+        return "1.1.1";
     }
 
     unsigned short serverPort() {
@@ -93,7 +94,7 @@ namespace ColumnLynx::Utils {
     }
 
     unsigned char protocolVersion() {
-        return 1;
+        return 2;
     }
 
     std::string bytesToHexString(const uint8_t* bytes, size_t length) {
@@ -144,19 +145,49 @@ namespace ColumnLynx::Utils {
 
         std::vector<std::string> out;
 
-        std::ifstream file(basePath + "whitelisted_keys");
+        namespace fs = std::filesystem;
+        std::error_code ec;
+
+        fs::path base(basePath);
+        fs::path absBase = fs::absolute(base, ec);
+        if (ec) {
+            warn("getWhitelistedKeys(): failed to resolve base path: " + basePath + " - " + ec.message());
+            return out;
+        }
+
+        fs::path whitelist = absBase / "whitelisted_keys";
+        if (!fs::exists(whitelist, ec) || ec) {
+            warn("getWhitelistedKeys(): whitelist file not found: " + whitelist.string());
+            return out;
+        }
+
+        // Canonicalize to avoid symlink tricks
+        fs::path canon = fs::canonical(whitelist, ec);
+        if (ec) {
+            warn("getWhitelistedKeys(): failed to canonicalize path: " + whitelist.string());
+            return out;
+        }
+
+        std::ifstream file(canon);
         if (!file.is_open()) {
-            warn("Failed to open whitelisted_keys file at path: " + basePath + "whitelisted_keys");
+            warn("getWhitelistedKeys(): failed to open whitelist file: " + canon.string());
             return out;
         }
 
         std::string line;
         while (std::getline(file, line)) {
+            // Trim whitespace
+            while (!line.empty() && isspace(static_cast<unsigned char>(line.back()))) line.pop_back();
+            size_t start = 0;
+            while (start < line.size() && isspace(static_cast<unsigned char>(line[start]))) ++start;
+            if (start >= line.size()) continue;
+            std::string key = line.substr(start);
+
             // Convert to upper case to align with the bytesToHexString() output
-            for (int i = 0; i < line.length(); i++) {
+            for (size_t i = 0; i < key.length(); ++i) {
-                line[i] = toupper(line[i]);
+                key[i] = static_cast<char>(toupper(static_cast<unsigned char>(key[i])));
             }
-            out.push_back(line);
+            out.push_back(key);
         }
 
         return out;
@@ -166,9 +197,26 @@ namespace ColumnLynx::Utils {
         // TODO: Currently re-reads every time.
         std::vector<std::string> readLines;
 
-        std::ifstream file(path);
+        namespace fs = std::filesystem;
+        std::error_code ec;
+        fs::path p(path);
+        fs::path abs = fs::absolute(p, ec);
+        if (ec) {
+            throw std::runtime_error("getConfigMap(): failed to resolve path: " + path + " - " + ec.message());
+        }
+
+        if (!fs::exists(abs, ec) || ec) {
+            throw std::runtime_error("getConfigMap(): config file does not exist: " + abs.string());
+        }
+
+        fs::path canon = fs::canonical(abs, ec);
+        if (ec) {
+            throw std::runtime_error("getConfigMap(): failed to canonicalize config path: " + abs.string());
+        }
+
+        std::ifstream file(canon);
         if (!file.is_open()) {
-            throw std::runtime_error("Failed to open config file at path: " + path);
+            throw std::runtime_error("Failed to open config file at path: " + canon.string());
         }
 
         std::string line;

src/common/virtual_interface.cpp

@@ -4,6 +4,11 @@
 
 #include <columnlynx/common/net/virtual_interface.hpp>
 
+#include <spawn.h>
+#include <sys/wait.h>
+
+extern char **environ;
+
 // This is all fucking voodoo dark magic.
 
 #if defined(_WIN32)
@@ -56,6 +61,33 @@ static void InitializeWintun()
 #endif // _WIN32
 
 namespace ColumnLynx::Net {
+
+// Run a command without invoking a shell. Arguments are passed directly
+// to the underlying process to avoid shell injection vulnerabilities.
+static bool runCommand(const std::vector<std::string>& args) {
+    if (args.empty()) return false;
+
+    std::vector<char*> argv;
+    argv.reserve(args.size() + 1);
+    for (const auto &s : args) {
+        argv.push_back(const_cast<char*>(s.c_str()));
+    }
+    argv.push_back(nullptr);
+
+    pid_t pid;
+    int rc = posix_spawnp(&pid, argv[0], nullptr, nullptr, argv.data(), environ);
+    if (rc != 0) {
+        return false;
+    }
+
+    int status = 0;
+    if (waitpid(pid, &status, 0) == -1) {
+        return false;
+    }
+
+    return WIFEXITED(status) && WEXITSTATUS(status) == 0;
+}
+
     // ------------------------------ Constructor ------------------------------
     VirtualInterface::VirtualInterface(const std::string& ifName)
         : mIfName(ifName), mFd(-1)
@@ -181,8 +213,8 @@ namespace ColumnLynx::Net {
         pfd.fd = mFd;
         pfd.events = POLLIN;
 
-        // timeout in ms; keep it small so shutdown is responsive
+        // timeout in ms; keep it small so shutdown is responsive. Reduced for lower latency.
-        int ret = poll(&pfd, 1, 200);
+        int ret = poll(&pfd, 1, 50);
 
         if (ret == 0) {
             // No data yet
@@ -307,25 +339,10 @@ namespace ColumnLynx::Net {
 
     void VirtualInterface::resetIP() {
     #if defined(__linux__)
-        char cmd[512];
+        runCommand({"ip", "addr", "flush", "dev", mIfName});
-        snprintf(cmd, sizeof(cmd),
-                 "ip addr flush dev %s",
-                 mIfName.c_str()
-        );
-        system(cmd);
     #elif defined(__APPLE__)
-        char cmd[512];
+        runCommand({"ifconfig", mIfName, "inet", "0.0.0.0", "delete"});
-        snprintf(cmd, sizeof(cmd),
+        runCommand({"ifconfig", mIfName, "inet6", "::", "delete"});
-                 "ifconfig %s inet 0.0.0.0 delete",
-                 mIfName.c_str()
-        );
-        system(cmd);
-
-        snprintf(cmd, sizeof(cmd),
-                 "ifconfig %s inet6 :: delete",
-                 mIfName.c_str()
-        );
-        system(cmd);
 
         // Wipe old routes
         //snprintf(cmd, sizeof(cmd),
@@ -357,26 +374,19 @@ namespace ColumnLynx::Net {
     bool VirtualInterface::mApplyLinuxIP(uint32_t clientIP, uint32_t serverIP,
                                         uint8_t prefixLen, uint16_t mtu)
     {
-        char cmd[512];
     
         std::string ipStr = ipv4ToString(clientIP);
         std::string peerStr = ipv4ToString(serverIP);
     
         // Wipe the current config
-        snprintf(cmd, sizeof(cmd),
+        runCommand({"ip", "addr", "flush", "dev", mIfName});
-                 "ip addr flush dev %s",
-                 mIfName.c_str()
-        );
-        system(cmd);
 
-        snprintf(cmd, sizeof(cmd),
+        // Add address with peer
-                 "ip addr add %s/%d peer %s dev %s",
+        std::string addrArg = ipStr + "/" + std::to_string(prefixLen);
-                 ipStr.c_str(), prefixLen, peerStr.c_str(), mIfName.c_str());
+        runCommand({"ip", "addr", "add", addrArg, "peer", peerStr, "dev", mIfName});
-        system(cmd);
 
-        snprintf(cmd, sizeof(cmd),
+        // Bring link up and set MTU
-                 "ip link set dev %s up mtu %d", mIfName.c_str(), mtu);
+        runCommand({"ip", "link", "set", "dev", mIfName, "up", "mtu", std::to_string(mtu)});
-        system(cmd);
     
         return true;
     }
@@ -387,39 +397,23 @@ namespace ColumnLynx::Net {
     bool VirtualInterface::mApplyMacOSIP(uint32_t clientIP, uint32_t serverIP,
                                         uint8_t prefixLen, uint16_t mtu)
     {
-        char cmd[512];
     
         std::string ipStr = ipv4ToString(clientIP);
         std::string peerStr = ipv4ToString(serverIP);
         std::string prefixStr = ipv4ToString(prefixLengthToNetmask(prefixLen), false);
         Utils::debug("Prefix string: " + prefixStr);
     
-        // Reset
+        // Reset IPv4 and IPv6 addresses
-        snprintf(cmd, sizeof(cmd),
+        runCommand({"ifconfig", mIfName, "inet", "0.0.0.0", "delete"});
-                 "ifconfig %s inet 0.0.0.0 delete",
+        runCommand({"ifconfig", mIfName, "inet6", "::", "delete"});
-                mIfName.c_str()
-        );
-        system(cmd);
 
-        snprintf(cmd, sizeof(cmd),
+        // Set address and netmask
-                 "ifconfig %s inet6 :: delete",
+        std::string netArg = ipStr + " " + peerStr; // ifconfig expects ip peer
-                mIfName.c_str()
+        runCommand({"ifconfig", mIfName, "inet", ipStr, peerStr, "mtu", std::to_string(mtu), "netmask", prefixStr, "up"});
-        );
-        system(cmd);
 
-        // Set
+        // Add route for the network
-        snprintf(cmd, sizeof(cmd),
+        std::string networkArg = ipStr + "/" + std::to_string(prefixLen);
-                "ifconfig %s inet %s %s mtu %d netmask %s up",
+        runCommand({"route", "-n", "add", "-net", networkArg, "-interface", mIfName});
-                 mIfName.c_str(), ipStr.c_str(), peerStr.c_str(), mtu, prefixStr.c_str());
-        system(cmd);
-
-        // Host bits are auto-normalized by the kernel on macOS, so we don't need to worry about them not being zeroed out.
-        snprintf(cmd, sizeof(cmd),
-                 "route -n add -net %s/%d -interface %s",
-                 ipStr.c_str(), prefixLen, mIfName.c_str());
-        system(cmd);
-
-        Utils::log("Executed command: " + std::string(cmd));
     
         return true;
     }

src/server/main.cpp

@@ -6,6 +6,7 @@
 #include <iostream>
 #include <thread>
 #include <chrono>
+#include <cstring>
 #include <columnlynx/common/utils.hpp>
 #include <columnlynx/common/panic_handler.hpp>
 #include <columnlynx/server/net/tcp/tcp_server.hpp>
@@ -15,6 +16,7 @@
 #include <unordered_map>
 #include <cxxopts.hpp>
 #include <columnlynx/common/net/virtual_interface.hpp>
+#include <columnlynx/server/server_session.hpp>
 
 #if defined(__WIN32__)
 #include <windows.h>
@@ -69,6 +71,8 @@ int main(int argc, char** argv) {
         //WintunInitialize();
 #endif
 
+        struct ServerState serverState{};
+
         // Get the config path, ENV > CLI > /etc/columnlynx
         std::string configPath = optionsObj["config-dir"].as<std::string>();
         const char* envConfigPath = std::getenv("COLUMNLYNX_CONFIG_DIR");
@@ -84,11 +88,23 @@ int main(int argc, char** argv) {
             #endif
         }
 
-        std::unordered_map<std::string, std::string> config = Utils::getConfigMap(configPath + "server_config");
+        serverState.configPath = configPath;
+
+#if defined(DEBUG)
+        std::unordered_map<std::string, std::string> config = Utils::getConfigMap(configPath + "server_config", { "NETWORK", "SUBNET_MASK" });
+#else
+        // A production server should never use random keys. If the config file cannot be read or does not contain keys, the server will fail to start.
+        std::unordered_map<std::string, std::string> config = Utils::getConfigMap(configPath + "server_config", { "NETWORK", "SUBNET_MASK", "SERVER_PUBLIC_KEY", "SERVER_PRIVATE_KEY" });
+#endif
+
+        serverState.serverConfig = config;
 
         std::shared_ptr<VirtualInterface> tun = std::make_shared<VirtualInterface>(optionsObj["interface"].as<std::string>());
         log("Using virtual interface: " + tun->getName());
 
+        // Store a reference to the tun in the serverState, it will increment and keep a safe reference (we love shared_ptrs)
+        serverState.virtualInterface = tun;
+
         // Generate a temporary keypair, replace with actual CA signed keys later (Note, these are stored in memory)
         std::shared_ptr<LibSodiumWrapper> sodiumWrapper = std::make_shared<LibSodiumWrapper>();
 
@@ -117,21 +133,44 @@ int main(int argc, char** argv) {
 
         log("Server public key: " + bytesToHexString(sodiumWrapper->getPublicKey(), crypto_sign_PUBLICKEYBYTES));
 
-        std::shared_ptr<bool> hostRunning = std::make_shared<bool>(true);
+        serverState.sodiumWrapper = sodiumWrapper;
+        serverState.ipv4Only = ipv4Only;
+        serverState.hostRunning = true;
+
+        // Store the global state; from now on, it should only be accessed through the ServerSession singleton, which will ensure thread safety with its internal mutex
+        ServerSession::getInstance().setServerState(std::make_shared<ServerState>(std::move(serverState)));
 
         asio::io_context io;
 
-        auto server = std::make_shared<TCPServer>(io, serverPort(), sodiumWrapper, hostRunning, configPath, ipv4Only);
+        auto server = std::make_shared<TCPServer>(io, serverPort());
-        auto udpServer = std::make_shared<UDPServer>(io, serverPort(), hostRunning, ipv4Only, tun);
+        auto udpServer = std::make_shared<UDPServer>(io, serverPort());
+
+        // Schedule periodic cleanup of expired sessions every 5 minutes
+        auto cleanupTimer = std::make_shared<asio::steady_timer>(io);
+        auto cleanupHandler = std::make_shared<std::function<void(const asio::error_code&)>>();
+        *cleanupHandler = [cleanupTimer, cleanupHandler](const asio::error_code& ec) {
+            if (ec == asio::error::operation_aborted) return; // Timer cancelled
+            try {
+                SessionRegistry::getInstance().cleanupExpired();
+            } catch (const std::exception& e) {
+                Utils::warn(std::string("SessionRegistry::cleanupExpired() threw: ") + e.what());
+            }
+            cleanupTimer->expires_after(std::chrono::minutes(5));
+            cleanupTimer->async_wait(*cleanupHandler);
+        };
+        cleanupTimer->expires_after(std::chrono::minutes(5));
+        cleanupTimer->async_wait(*cleanupHandler);
 
         asio::signal_set signals(io, SIGINT, SIGTERM);
         signals.async_wait([&](const std::error_code&, int) {
             log("Received termination signal. Shutting down server gracefully.");
             done = 1;
             asio::post(io, [&]() {
-                *hostRunning = false;
+                ServerSession::getInstance().setHostRunning(false);
                 server->stop();
                 udpServer->stop();
+                // Cancel cleanup timer
+                cleanupTimer->cancel();
             });
         });
 
@@ -152,15 +191,35 @@ int main(int argc, char** argv) {
                 continue;
             }
 
+            if (packet.size() < 20) {
+                Utils::warn("TUN: Dropping packet smaller than IPv4 header (" + std::to_string(packet.size()) + " bytes)");
+                continue;
+            }
+
             const uint8_t* ip = packet.data();
-            uint32_t srcIP = ntohl(*(uint32_t*)(ip + 12)); // IPv4 source address offset
+            uint8_t ipVersion = (ip[0] >> 4);
-            uint32_t dstIP = ntohl(*(uint32_t*)(ip + 16)); // IPv4 destination address offset
+            if (ipVersion != 4) {
+                Utils::debug("TUN: Non-IPv4 packet received (version=" + std::to_string(ipVersion) + "), skipping server IPv4 routing path.");
+                continue;
+            }
+
+            uint32_t srcIPNet = 0;
+            uint32_t dstIPNet = 0;
+            std::memcpy(&srcIPNet, ip + 12, sizeof(srcIPNet)); // IPv4 source address offset
+            std::memcpy(&dstIPNet, ip + 16, sizeof(dstIPNet)); // IPv4 destination address offset
+            uint32_t srcIP = ntohl(srcIPNet);
+            uint32_t dstIP = ntohl(dstIPNet);
         
             // First, check if destination IP is a registered client (e.g., server responding to client or client-to-client)
             auto dstSession = SessionRegistry::getInstance().getByIP(dstIP);
             if (dstSession) {
-                // Destination is a registered client, forward to that client's session
+                // Destination is a registered client, enforce MTU and forward to that client's session
-                udpServer->sendData(dstSession->sessionID, std::string(packet.begin(), packet.end()));
+                const size_t MTU = 1420; // Enforce configured MTU; TODO: read from server config
+                if (packet.size() > MTU) {
+                    Utils::warn("TUN: Dropping oversized packet (" + std::to_string(packet.size()) + " > MTU " + std::to_string(MTU) + ")");
+                } else {
+                    udpServer->sendData(dstSession->sessionID, std::string(packet.begin(), packet.end()));
+                }
                 continue;
             }
 

src/server/net/tcp/tcp_connection.cpp

@@ -14,23 +14,31 @@ namespace ColumnLynx::Net::TCP {
             Utils::warn("Failed to get remote endpoint: " + std::string(e.what()));
         }
 
-        mHandler->onMessage([this](AnyMessageType type, const std::string& data) {
+        mHandler->onMessage([weakSelf = weak_from_this()](AnyMessageType type, const std::string& data) {
-            mHandleMessage(static_cast<ClientMessageType>(MessageHandler::toUint8(type)), data);
+            if (auto self = weakSelf.lock()) {
+                self->mHandleMessage(static_cast<ClientMessageType>(MessageHandler::toUint8(type)), data);
+            }
         });
 
-        mHandler->onDisconnect([this](const asio::error_code& ec) {
+        mHandler->onDisconnect([weakSelf = weak_from_this()](const asio::error_code& ec) {
+            auto self = weakSelf.lock();
+            if (!self) {
+                return;
+            }
             // Peer has closed; finalize locally without sending RST
-            Utils::log("Client disconnected: " + mRemoteIP + " - " + ec.message());
+            Utils::log("Client disconnected: " + self->mRemoteIP + " - " + ec.message());
             asio::error_code ec2;
-            mHandler->socket().close(ec2);
+            if (self->mHandler) {
+                self->mHandler->socket().close(ec2);
+            }
 
-            SessionRegistry::getInstance().erase(mConnectionSessionID);
+            SessionRegistry::getInstance().erase(self->mConnectionSessionID);
-            SessionRegistry::getInstance().deallocIP(mConnectionSessionID);
+            SessionRegistry::getInstance().deallocIP(self->mConnectionSessionID);
 
-            Utils::log("Closed connection to " + mRemoteIP);
+            Utils::log("Closed connection to " + self->mRemoteIP);
 
-            if (mOnDisconnect) {
+            if (self->mOnDisconnect) {
-                mOnDisconnect(shared_from_this());
+                self->mOnDisconnect(self);
             }
         });
 
@@ -66,7 +74,7 @@ namespace ColumnLynx::Net::TCP {
         Utils::log("Initiated graceful disconnect (half-close) to " + mRemoteIP);
     }
 
-    uint64_t TCPConnection::getSessionID() const {
+    uint32_t TCPConnection::getSessionID() const {
         return mConnectionSessionID;
     }
 
@@ -77,7 +85,7 @@ namespace ColumnLynx::Net::TCP {
     void TCPConnection::mStartHeartbeat() {
         auto self = shared_from_this();
         mHeartbeatTimer.expires_after(std::chrono::seconds(5));
-        mHeartbeatTimer.async_wait([this, self](const asio::error_code& ec) {
+        mHeartbeatTimer.async_wait([self](const asio::error_code& ec) {
             if (ec == asio::error::operation_aborted) {
                 return; // Timer was cancelled
             }
@@ -90,10 +98,13 @@ namespace ColumnLynx::Net::TCP {
                 
                 // Remove socket forcefully, client is dead
                 asio::error_code ec;
-                mHandler->socket().shutdown(asio::ip::tcp::socket::shutdown_both, ec);
+                if (self->mHandler) {
-                mHandler->socket().close(ec);
+                    self->mHandler->socket().shutdown(asio::ip::tcp::socket::shutdown_both, ec);
+                    self->mHandler->socket().close(ec);
+                }
 
                 SessionRegistry::getInstance().erase(self->mConnectionSessionID);
+                SessionRegistry::getInstance().deallocIP(self->mConnectionSessionID);
 
                 return;
             }
@@ -113,8 +124,8 @@ namespace ColumnLynx::Net::TCP {
             case ClientMessageType::HANDSHAKE_INIT: {
                 Utils::log("Received HANDSHAKE_INIT from " + reqAddr);
 
-                if (data.size() < 1 + crypto_box_PUBLICKEYBYTES) {
+                if (data.size() != 1 + crypto_sign_PUBLICKEYBYTES) {
-                    Utils::warn("HANDSHAKE_INIT from " + reqAddr + " is too short.");
+                    Utils::warn("HANDSHAKE_INIT from " + reqAddr + " has invalid size: " + std::to_string(data.size()));
                     disconnect();
                     return;
                 }
@@ -130,7 +141,7 @@ namespace ColumnLynx::Net::TCP {
                 Utils::log("Client protocol version " + std::to_string(clientProtoVer) + " accepted from " + reqAddr + ".");
 
                 PublicKey signPk;
-                std::memcpy(signPk.data(), data.data() + 1, std::min(data.size() - 1, sizeof(signPk)));
+                std::memcpy(signPk.data(), data.data() + 1, sizeof(signPk));
 
                 // We can safely store this without further checking, the client will need to send the encrypted AES key in a way where they must possess the corresponding private key anyways.
                 int r = crypto_sign_ed25519_pk_to_curve25519(mConnectionPublicKey.data(), signPk.data()); // Store the client's public encryption key key (for identification)
@@ -145,7 +156,7 @@ namespace ColumnLynx::Net::TCP {
                 
                 Utils::debug("Key attempted connect: " + Utils::bytesToHexString(signPk.data(), signPk.size()));
 
-                std::vector<std::string> whitelistedKeys = Utils::getWhitelistedKeys(mConfigDirPath);
+                std::vector<std::string> whitelistedKeys = Utils::getWhitelistedKeys(ServerSession::getInstance().getConfigPath());
 
                 if (std::find(whitelistedKeys.begin(), whitelistedKeys.end(), Utils::bytesToHexString(signPk.data(), signPk.size())) == whitelistedKeys.end()) {
                     Utils::warn("Non-whitelisted client attempted to connect, terminating. Client IP: " + reqAddr);
@@ -156,20 +167,26 @@ namespace ColumnLynx::Net::TCP {
 
                 Utils::debug("Client " + reqAddr + " passed authorized_keys");
 
-                mHandler->sendMessage(ServerMessageType::HANDSHAKE_IDENTIFY, Utils::uint8ArrayToString(mLibSodiumWrapper->getPublicKey(), crypto_sign_PUBLICKEYBYTES)); // This public key should always exist
+                mHandler->sendMessage(ServerMessageType::HANDSHAKE_IDENTIFY, Utils::uint8ArrayToString(ServerSession::getInstance().getSodiumWrapper()->getPublicKey(), crypto_sign_PUBLICKEYBYTES)); // This public key should always exist
                 break;
             }
             case ClientMessageType::HANDSHAKE_CHALLENGE: {
                 Utils::log("Received HANDSHAKE_CHALLENGE from " + reqAddr);
                 
-                // Convert to byte array
+                // Convert to byte array - require exact size
+                if (data.size() != 32) {
+                    Utils::warn("HANDSHAKE_CHALLENGE has invalid size: " + std::to_string(data.size()));
+                    disconnect();
+                    return;
+                }
+
                 uint8_t challengeData[32];
-                std::memcpy(challengeData, data.data(), std::min(data.size(), sizeof(challengeData)));
+                std::memcpy(challengeData, data.data(), sizeof(challengeData));
 
                 // Sign the challenge
                 Signature sig = Utils::LibSodiumWrapper::signMessage(
                     challengeData, sizeof(challengeData),
-                    mLibSodiumWrapper->getPrivateKey()
+                    ServerSession::getInstance().getSodiumWrapper()->getPrivateKey()
                 );
 
                 mHandler->sendMessage(ServerMessageType::HANDSHAKE_CHALLENGE_RESPONSE, Utils::uint8ArrayToString(sig.data(), sig.size())); // Placeholder response
@@ -191,8 +208,8 @@ namespace ColumnLynx::Net::TCP {
                 std::memcpy(ciphertext.data(), data.data() + nonce.size(), ciphertext.size());
                 try {
                     std::array<uint8_t, 32> arrayPrivateKey;
-                    std::copy(mLibSodiumWrapper->getXPrivateKey(),
+                    std::copy(ServerSession::getInstance().getSodiumWrapper()->getXPrivateKey(),
-                              mLibSodiumWrapper->getXPrivateKey() + 32,
+                              ServerSession::getInstance().getSodiumWrapper()->getXPrivateKey() + 32,
                               arrayPrivateKey.begin());
 
                     // Decrypt the AES key using the client's public key and server's private key
@@ -211,14 +228,18 @@ namespace ColumnLynx::Net::TCP {
 
                     std::memcpy(mConnectionAESKey.data(), decrypted.data(), decrypted.size());
 
-                    // Make a Session ID
+                    // Make a Session ID - unique and not zero (zero is reserved for invalid sessions)
-                    randombytes_buf(&mConnectionSessionID, sizeof(mConnectionSessionID));
+                    do {
+                        randombytes_buf(&mConnectionSessionID, sizeof(mConnectionSessionID));
+                    } while (SessionRegistry::getInstance().exists(mConnectionSessionID) || mConnectionSessionID == 0); // Regenerate if it already exists or is zero (zero is reserved for invalid sessions)
 
                     // Encrypt the Session ID with the established AES key (using symmetric encryption, nonce can be all zeros for this purpose)
                     Nonce symNonce{}; // All zeros
 
-                    std::string networkString = mRawServerConfig->find("NETWORK")->second; // The load check guarantees that this value exists
+                    const auto& serverConfig = ServerSession::getInstance().getRawServerConfig();
-                    uint8_t configMask = std::stoi(mRawServerConfig->find("SUBNET_MASK")->second); // Same deal here
+
+                    std::string networkString = serverConfig.find("NETWORK")->second; // The load check guarantees that this value exists
+                    uint8_t configMask = std::stoi(serverConfig.find("SUBNET_MASK")->second); // Same deal here
 
                     uint32_t baseIP = Net::VirtualInterface::stringToIpv4(networkString);
 
@@ -245,11 +266,11 @@ namespace ColumnLynx::Net::TCP {
                     tunConfig.dns1 = htonl(0x08080808);    // 8.8.8.8
                     tunConfig.dns2 = 0;
 
-                    uint64_t sessionIDNet = Utils::chtobe64(mConnectionSessionID);
+                    uint32_t sessionIDNet = htonl(mConnectionSessionID);
 
-                    std::vector<uint8_t> payload(sizeof(uint64_t) + sizeof(tunConfig));
+                    std::vector<uint8_t> payload(sizeof(uint32_t) + sizeof(tunConfig));
-                    std::memcpy(payload.data(), &sessionIDNet, sizeof(uint64_t));
+                    std::memcpy(payload.data(), &sessionIDNet, sizeof(uint32_t));
-                    std::memcpy(payload.data() + sizeof(uint64_t), &tunConfig, sizeof(tunConfig));
+                    std::memcpy(payload.data() + sizeof(uint32_t), &tunConfig, sizeof(tunConfig));
 
                     std::vector<uint8_t> encryptedPayload = Utils::LibSodiumWrapper::encryptMessage(
                         payload.data(), payload.size(),
@@ -261,6 +282,7 @@ namespace ColumnLynx::Net::TCP {
                     // Add to session registry
                     Utils::log("Handshake with " + reqAddr + " completed successfully. Session ID assigned (" + std::to_string(mConnectionSessionID) + ").");
                     auto session = std::make_shared<SessionState>(mConnectionAESKey, std::chrono::hours(12), clientIP, htonl(0x0A0A0001), mConnectionSessionID);
+                    session->setBaseNonce(); // Set it
                     SessionRegistry::getInstance().put(mConnectionSessionID, std::move(session));
                     SessionRegistry::getInstance().lockIP(mConnectionSessionID, clientIP);
 

src/server/net/tcp/tcp_server.cpp

@@ -27,16 +27,13 @@ namespace ColumnLynx::Net::TCP {
                     }
                     Utils::error("Accept failed: " + ec.message());
                     // Try again only if still running
-                    if (mHostRunning && *mHostRunning && mAcceptor.is_open())
+                    if (ServerSession::getInstance().isHostRunning() && mAcceptor.is_open())
                         mStartAccept();
                     return;
                 }
 
                 auto client = TCPConnection::create(
                     std::move(socket),
-                    mSodiumWrapper,
-                    &mRawServerConfig,
-                    mConfigDirPath,
                     [this](std::shared_ptr<TCPConnection> c) {
                         mClients.erase(c);
                         Utils::log("Client removed.");
@@ -46,7 +43,7 @@ namespace ColumnLynx::Net::TCP {
                 client->start();
                 Utils::log("Accepted new client connection.");
             
-                if (mHostRunning && *mHostRunning && mAcceptor.is_open())
+                if (ServerSession::getInstance().isHostRunning() && mAcceptor.is_open())
                     mStartAccept();
             }
         );

src/server/net/udp/udp_server.cpp

@@ -16,26 +16,27 @@ namespace ColumnLynx::Net::UDP {
                 if (ec) {
                     if (ec == asio::error::operation_aborted) return; // Socket closed
                     // Other recv error
-                    if (mHostRunning && *mHostRunning) mStartReceive();
+                    if (ServerSession::getInstance().isHostRunning()) mStartReceive();
                     return;
                 }
                 if (bytes > 0) mHandlePacket(bytes);
-                if (mHostRunning && *mHostRunning) mStartReceive();
+                if (ServerSession::getInstance().isHostRunning()) mStartReceive();
             }
         );
     }
 
     void UDPServer::mHandlePacket(std::size_t bytes) {
-        if (bytes < sizeof(UDPPacketHeader))
+        if (bytes < sizeof(UDPPacketHeader) + sizeof(uint32_t))
             return;
         
         const auto* hdr = reinterpret_cast<UDPPacketHeader*>(mRecvBuffer.data());
 
-        // Get plaintext session ID (assuming first 8 bytes after nonce (header))
+        // Get plaintext session ID (first 4 bytes after header, in network byte order)
-        uint64_t sessionID = 0;
+        uint32_t sessionIDNet = 0;
-        std::memcpy(&sessionID, mRecvBuffer.data() + sizeof(UDPPacketHeader), sizeof(uint64_t));
+        std::memcpy(&sessionIDNet, mRecvBuffer.data() + sizeof(UDPPacketHeader), sizeof(uint32_t));
+        uint32_t sessionID = sessionIDNet; // ntohl(sessionIDNet); --- IGNORE ---
 
-        auto it = mRecvBuffer.begin() + sizeof(UDPPacketHeader) + sizeof(uint64_t);
+        auto it = mRecvBuffer.begin() + sizeof(UDPPacketHeader) + sizeof(uint32_t);
         std::vector<uint8_t> encryptedPayload(it, mRecvBuffer.begin() + bytes);
 
         // Get associated session state
@@ -54,7 +55,7 @@ namespace ColumnLynx::Net::UDP {
                 encryptedPayload.data(), encryptedPayload.size(),
                 session->aesKey,
                 hdr->nonce, "udp-data"
-                //std::string(reinterpret_cast<const char*>(&sessionID), sizeof(uint64_t))
+                //std::string(reinterpret_cast<const char*>(&sessionID), sizeof(uint32_t))
             );
 
             Utils::debug("Passed decryption");
@@ -76,7 +77,7 @@ namespace ColumnLynx::Net::UDP {
         }
     }
 
-    void UDPServer::sendData(const uint64_t sessionID, const std::string& data) {
+    void UDPServer::sendData(uint32_t sessionID, const std::string& data) {
         // Find the IPv4/IPv6 endpoint for the session
         std::shared_ptr<const SessionState> session = SessionRegistry::getInstance().get(sessionID);
         if (!session) {
@@ -92,23 +93,45 @@ namespace ColumnLynx::Net::UDP {
 
         // Prepare packet
         UDPPacketHeader hdr{};
-        randombytes_buf(hdr.nonce.data(), hdr.nonce.size());
+        uint8_t nonce[12];
+        uint32_t prefix = session->noncePrefix;
+            // Increment send counter with overflow protection
+            uint64_t sendCount = 0;
+            {
+                auto ptr = const_cast<SessionState*>(session.get());
+                uint64_t old = ptr->send_ctr.load(std::memory_order_relaxed);
+                for (;;) {
+                    if (old == std::numeric_limits<uint64_t>::max()) {
+                        Utils::error("UDP: send counter overflow for session " + std::to_string(sessionID));
+                        return;
+                    }
+                    if (ptr->send_ctr.compare_exchange_weak(old, old + 1, std::memory_order_relaxed)) {
+                        sendCount = old;
+                        break;
+                    }
+                    // old updated by compare_exchange_weak, loop
+                }
+            }
+        memcpy(nonce, &prefix, sizeof(uint32_t)); // Prefix nonce
+        memcpy(nonce + sizeof(uint32_t), &sendCount, sizeof(uint64_t)); // Use send count as nonce suffix to ensure uniqueness
+        std::copy_n(nonce, 12, hdr.nonce.data());
 
         auto encryptedPayload = Utils::LibSodiumWrapper::encryptMessage(
             reinterpret_cast<const uint8_t*>(data.data()), data.size(),
             session->aesKey, hdr.nonce, "udp-data"
-            //std::string(reinterpret_cast<const char*>(&sessionID), sizeof(uint64_t))
+            //std::string(reinterpret_cast<const char*>(&sessionID), sizeof(uint32_t))
         );
 
         std::vector<uint8_t> packet;
-        packet.reserve(sizeof(UDPPacketHeader) +  sizeof(uint64_t) + encryptedPayload.size());
+        packet.reserve(sizeof(UDPPacketHeader) + sizeof(uint32_t) + encryptedPayload.size());
         packet.insert(packet.end(), 
             reinterpret_cast<uint8_t*>(&hdr),
             reinterpret_cast<uint8_t*>(&hdr) + sizeof(UDPPacketHeader)
         );
+        uint32_t sessionIDNet = htonl(sessionID);
         packet.insert(packet.end(),
-            reinterpret_cast<const uint8_t*>(&sessionID),
+            reinterpret_cast<const uint8_t*>(&sessionIDNet),
-            reinterpret_cast<const uint8_t*>(&sessionID) + sizeof(sessionID)
+            reinterpret_cast<const uint8_t*>(&sessionIDNet) + sizeof(sessionIDNet)
         );
         packet.insert(packet.end(), encryptedPayload.begin(), encryptedPayload.end());
 

src/server/server_session.cpp

@@ -0,0 +1,92 @@
+// server_session.cpp - Client Session data for ColumnLynx
+// Copyright (C) 2026 DcruBro
+// Distributed under the terms of the GNU General Public License, either version 2 only or version 3. See LICENSES/ for details.
+
+#include <columnlynx/server/server_session.hpp>
+
+namespace ColumnLynx {
+    std::shared_ptr<ServerState> ServerSession::getServerState() const {
+        std::shared_lock lock(mMutex);
+        return mServerState;
+    }
+
+    void ServerSession::setServerState(std::shared_ptr<ServerState> state) {
+        std::unique_lock lock(mMutex);
+        mServerState = std::move(state);
+    }
+
+    std::shared_ptr<Utils::LibSodiumWrapper> ServerSession::getSodiumWrapper() const {
+        std::shared_lock lock(mMutex);
+        return mServerState ? mServerState->sodiumWrapper : nullptr;
+    }
+
+    const std::string& ServerSession::getConfigPath() const {
+        static const std::string emptyString;
+        std::shared_ptr<ServerState> state = getServerState();
+        return state ? state->configPath : emptyString;
+    }
+
+    const std::unordered_map<std::string, std::string>& ServerSession::getRawServerConfig() const {
+        static const std::unordered_map<std::string, std::string> emptyMap;
+        std::shared_ptr<ServerState> state = getServerState();
+        return state ? state->serverConfig : emptyMap;
+    }
+
+    const std::shared_ptr<Net::VirtualInterface>& ServerSession::getVirtualInterface() const {
+        static const std::shared_ptr<Net::VirtualInterface> nullTun = nullptr;
+        std::shared_ptr<ServerState> state = getServerState();
+        return state ? state->virtualInterface : nullTun;
+    }
+
+    bool ServerSession::isIPv4Only() const {
+        std::shared_ptr<ServerState> state = getServerState();
+        return state ? state->ipv4Only : false;
+    }
+
+    bool ServerSession::isHostRunning() const {
+        std::shared_ptr<ServerState> state = getServerState();
+        return state ? state->hostRunning : false;
+    }
+
+    void ServerSession::setSodiumWrapper(std::shared_ptr<Utils::LibSodiumWrapper> sodiumWrapper) {
+        std::unique_lock lock(mMutex);
+        if (!mServerState)
+            mServerState = std::make_shared<ServerState>();
+        mServerState->sodiumWrapper = std::move(sodiumWrapper);
+    }
+
+    void ServerSession::setConfigPath(const std::string& configPath) {
+        std::unique_lock lock(mMutex);
+        if (!mServerState)
+            mServerState = std::make_shared<ServerState>();
+        mServerState->configPath = configPath;
+    }
+
+    void ServerSession::setRawServerConfig(const std::unordered_map<std::string, std::string>& config) {
+        std::unique_lock lock(mMutex);
+        if (!mServerState)
+            mServerState = std::make_shared<ServerState>();
+        mServerState->serverConfig = config;
+    }
+
+    void ServerSession::setVirtualInterface(std::shared_ptr<Net::VirtualInterface> tun) {
+        std::unique_lock lock(mMutex);
+        if (!mServerState)
+            mServerState = std::make_shared<ServerState>();
+        mServerState->virtualInterface = std::move(tun);
+    }
+
+    void ServerSession::setIPv4Only(bool ipv4Only) {
+        std::unique_lock lock(mMutex);
+        if (!mServerState)
+            mServerState = std::make_shared<ServerState>();
+        mServerState->ipv4Only = ipv4Only;
+    }
+
+    void ServerSession::setHostRunning(bool hostRunning) {
+        std::unique_lock lock(mMutex);
+        if (!mServerState)
+            mServerState = std::make_shared<ServerState>();
+        mServerState->hostRunning = hostRunning;
+    }
+}

tests/test_libsodium_wrapper.cpp

@@ -0,0 +1,42 @@
+// Tests for LibSodiumWrapper: random, symmetric encrypt/decrypt, sign/verify
+#include <iostream>
+#include <cassert>
+
+#include <columnlynx/common/libsodium_wrapper.hpp>
+
+int main() {
+    using namespace ColumnLynx::Utils;
+
+    // Random bytes uniqueness
+    auto a = LibSodiumWrapper::generateRandom256Bit();
+    auto b = LibSodiumWrapper::generateRandom256Bit();
+    assert(a != b && "generateRandom256Bit() should produce different outputs (very likely)");
+
+    // Symmetric encrypt/decrypt roundtrip
+    ColumnLynx::SymmetricKey key = {};
+    for (size_t i = 0; i < key.size(); ++i) key[i] = static_cast<uint8_t>(i);
+    auto nonce = LibSodiumWrapper::generateNonce();
+
+    std::string plaintext = "The quick brown fox jumps over the lazy dog";
+    auto ct = LibSodiumWrapper::encryptMessage(reinterpret_cast<const uint8_t*>(plaintext.data()), plaintext.size(), key, nonce, "aad");
+    auto pt = LibSodiumWrapper::decryptMessage(ct.data(), ct.size(), key, nonce, "aad");
+    std::string recovered(pt.begin(), pt.end());
+    assert(recovered == plaintext && "decrypt should recover original plaintext");
+
+    // Sign and verify
+    ColumnLynx::PrivateKey sk{}; ColumnLynx::PublicKey pk{};
+    randombytes_buf(sk.data(), sk.size());
+    // naive keypair generation for test purposes: use libsodium functions via wrapper
+    // generate a real keypair using crypto_sign
+    if (crypto_sign_keypair(pk.data(), sk.data()) != 0) {
+        std::cerr << "Failed to generate keypair\n";
+        return 2;
+    }
+
+    auto sig = LibSodiumWrapper::signMessage(plaintext, sk);
+    bool ok = LibSodiumWrapper::verifyMessage(plaintext, sig, pk);
+    assert(ok && "Signature should verify");
+
+    std::cout << "LibSodiumWrapper tests passed\n";
+    return 0;
+}

tests/test_session_registry.cpp

@@ -0,0 +1,49 @@
+// Simple unit tests for SessionRegistry
+#include <cassert>
+#include <iostream>
+#include <chrono>
+
+#include <columnlynx/common/net/session_registry.hpp>
+#include <columnlynx/common/libsodium_wrapper.hpp>
+
+int main() {
+    using namespace ColumnLynx::Net;
+    using namespace ColumnLynx::Utils;
+
+    auto &reg = SessionRegistry::getInstance();
+
+    // Use a unique session id to avoid colliding with any running instance
+    const uint32_t sid = 0xDEADBEEF;
+    // ensure clean state
+    reg.erase(sid);
+
+    auto key = LibSodiumWrapper::generateRandom256Bit();
+    auto state = std::make_shared<SessionState>(key, std::chrono::hours(24), 0xC0A80101 /*192.168.1.1*/, 0, sid);
+
+    reg.put(sid, state);
+
+    assert(reg.exists(sid) && "Session should exist after put()");
+
+    auto got = reg.get(sid);
+    assert(got && got->sessionID == sid && "get() should return stored session");
+
+    auto byip = reg.getByIP(0xC0A80101);
+    assert(byip && byip->sessionID == sid && "getByIP() should find session by client IP");
+
+    // Erase and verify removed
+    reg.erase(sid);
+    assert(!reg.exists(sid) && "Session should not exist after erase()");
+    assert(reg.getByIP(0xC0A80101) == nullptr && "getByIP() should return nullptr after erase");
+
+    // Test cleanupExpired: insert an already-expired session
+    const uint32_t sid2 = 0xFEEDBEEF;
+    reg.erase(sid2);
+    auto expiredState = std::make_shared<SessionState>(key, std::chrono::seconds(0), 0xC0A80102, 0, sid2);
+    reg.put(sid2, expiredState);
+    // Force cleanup
+    reg.cleanupExpired();
+    assert(!reg.exists(sid2) && "Expired session should be removed by cleanupExpired()");
+
+    std::cout << "SessionRegistry tests passed\n";
+    return 0;
+}

tests/test_session_registry_ip.cpp

@@ -0,0 +1,43 @@
+// Tests for SessionRegistry IP allocation and lock/dealloc
+#include <iostream>
+#include <cassert>
+
+#include <columnlynx/common/net/session_registry.hpp>
+#include <columnlynx/common/libsodium_wrapper.hpp>
+
+int main() {
+    using namespace ColumnLynx::Net;
+    using namespace ColumnLynx::Utils;
+
+    auto &reg = SessionRegistry::getInstance();
+
+    const uint32_t sid = 0xABCDEF01;
+    reg.erase(sid);
+
+    auto key = LibSodiumWrapper::generateRandom256Bit();
+    auto state = std::make_shared<SessionState>(key, std::chrono::hours(24), 0, 0, sid);
+    reg.put(sid, state);
+
+    // Lock IP
+    uint32_t ip = 0xC0A80201; // 192.168.2.1
+    reg.lockIP(sid, ip);
+
+    auto byip = reg.getByIP(ip);
+    assert(byip && byip->sessionID == sid && "lockIP should populate mIPSessions");
+
+    // deallocIP
+    reg.deallocIP(sid);
+    assert(reg.getByIP(ip) == nullptr && "deallocIP should remove mapping");
+
+    // getFirstAvailableIP: choose a small /30 range to limit hosts
+    uint32_t base = 0x0A000000; // 10.0.0.0
+    uint8_t mask = 30; // 2 usable hosts
+    uint32_t first = reg.getFirstAvailableIP(base, mask);
+    assert(first != 0 && "Should find available IP in empty registry");
+
+    // cleanup
+    reg.erase(sid);
+
+    std::cout << "SessionRegistry IP tests passed\n";
+    return 0;
+}

tests/test_tcp_message_handler_static.cpp

@@ -0,0 +1,30 @@
+// Tests for TCP MessageHandler static helpers
+#include <cassert>
+#include <iostream>
+
+#include <columnlynx/common/net/tcp/tcp_message_handler.hpp>
+#include <columnlynx/common/net/tcp/tcp_message_type.hpp>
+
+int main() {
+    using namespace ColumnLynx::Net::TCP;
+
+    // server message special codes
+    auto t1 = MessageHandler::decodeMessageType(0xFE);
+    // Expect GRACEFUL_DISCONNECT mapped
+    // Compare by converting back to uint8
+    assert(MessageHandler::toUint8(t1) == 0xFE);
+
+    auto t2 = MessageHandler::decodeMessageType(0xFF);
+    assert(MessageHandler::toUint8(t2) == 0xFF);
+
+    // Client message range (>= 0xA0)
+    auto t3 = MessageHandler::decodeMessageType(0xA5);
+    assert(MessageHandler::toUint8(t3) == 0xA5);
+
+    // Server message range (< 0xA0) and not special
+    auto t4 = MessageHandler::decodeMessageType(0x10);
+    assert(MessageHandler::toUint8(t4) == 0x10);
+
+    std::cout << "TCP MessageHandler static helpers tests passed\n";
+    return 0;
+}