feat: Upgrades networking to use io_uring. (#2315)

> [!IMPORTANT]
> **Breaking Changes**
> - DecodePacket and EncodePacket delegates replaced with IClientEncryption interface
> - NetState.Connection (Socket) replaced with internal RingSocket management
> - NetState.RecvPipe and NetState.SendPipe removed (buffers managed internally)

## Summary

Upgrades the networking stack from PollGroup-based I/O to io_uring, significantly improving I/O performance on Linux.
This also adds native client encryption support for encrypted UO clients.

## Major Changes

io_uring Networking Architecture
- Replaced PollGroup with IORingGroup for async socket I/O operations
- Removed Pipe.cs (mirrored ring buffer) and TcpServer.cs in favor of RingSocketManager
- Added NetState.Network.cs - centralized network infrastructure handling accept, recv, send, and disconnect
completions
- Added SocketHelper.cs - platform-specific socket utilities for raw socket handle operations (getpeername,
getsockname)
- Buffer management now handled by RingSocketManager with configurable slab allocation

### Client Encryption Support
- Added full encryption stack in Network/Encryption/:
  - EncryptionConfig.cs - configurable encryption modes (None, Unencrypted, Encrypted, Both)
  - EncryptionManager.cs - encryption detection and initialization for login/game packets
  - LoginEncryption.cs - handles login packet encryption with version-derived keys
  - GameEncryption.cs - handles game server encryption using Twofish
  - TwofishEngine.cs - optimized Twofish block cipher implementation
  - LoginKeys.cs - encryption key table for client versions
  - IClientEncryption.cs - interface for client encryption implementations

### NetState Improvements
- Replaced Socket Connection with RingSocket _socket for managed socket lifecycle
- Changed from GCHandle polling to event-based completion processing
- Disconnect handling now properly waits for pending sends to flush
- Simplified connecting socket management using lazy queue removal

### Configuration
- New settings: network.encryptionMode and network.encryptionDebug
- Encryption mode flags: Unencrypted, Encrypted, or Both

### Dependencies
- Replaced PollGroup NuGet package with IORingGroup
- Linux requires liburing-dev / liburing-devel package

### Test plan

- Verify server starts and accepts connections on Linux with io_uring
- Verify server starts and accepts connections on Windows (fallback to IOCP)
- Test unencrypted client connections (ClassicUO with encryption disabled)
- Test encrypted client connections if available
- Verify graceful disconnect flushes pending data
- Confirm CI builds pass on all target platforms

Author: kamronbatman

.github/workflows/build-test.yml

@@ -42,7 +42,9 @@ jobs:
 
   build-linux:
     runs-on: ubuntu-latest
-    container: ${{ matrix.container }}
+    container:
+      image: ${{ matrix.container }}
+      options: --security-opt seccomp=unconfined
     name: Build (${{ matrix.name }})
     strategy:
       fail-fast: false
@@ -68,14 +70,17 @@ jobs:
             packageManager: dnf
 
     steps:
-      - name: Enable EPEL
-        run: dnf upgrade --refresh -y && dnf install -y epel-release epel-next-release
-        if: ${{ startsWith(matrix.name, 'CentOS')  }}
+      - name: Enable EPEL and CRB for CentOS
+        run: |
+          dnf upgrade --refresh -y
+          dnf install -y epel-release epel-next-release
+          dnf config-manager --set-enabled crb
+        if: ${{ startsWith(matrix.name, 'CentOS') }}
       - name: Install Prerequisites using dnf
-        run: dnf makecache --refresh && dnf install -y findutils libicu libdeflate-devel zstd libargon2-devel
+        run: dnf makecache --refresh && dnf install -y findutils libicu libdeflate-devel zstd libargon2-devel liburing-devel
         if: ${{ matrix.packageManager == 'dnf' }}
       - name: Install Prerequisites using apt
-        run: apt-get update -y && apt-get install -y curl libicu-dev libdeflate-dev zstd libargon2-dev tzdata
+        run: apt-get update -y && apt-get install -y curl libicu-dev libdeflate-dev zstd libargon2-dev tzdata liburing-dev
         if: ${{ matrix.packageManager == 'apt' }}
       - uses: actions/checkout@v4
         with:

Projects/Server.Tests/Fixtures/TestServerInitializer.cs

@@ -78,6 +78,9 @@ public static void Initialize(bool loadTileData = false)
             Core.LoopContext = new EventLoopContext();
             Core.Expansion = Expansion.EJ;
 
+            // Configure networking (initializes RingSocketManager for tests)
+            Server.Network.NetState.Configure();
+
             // Configure / Initialize
             TestMapDefinitions.ConfigureTestMapDefinitions();
 

Projects/Server.Tests/Helpers/PacketTestUtilities.cs

@@ -1,16 +1,94 @@
 using System;
+using System.Collections.Generic;
+using System.Net;
 using System.Net.Sockets;
+using System.Network;
 using Server.Network;
 
-namespace Server.Tests.Network
+namespace Server.Tests.Network;
+
+public static class PacketTestUtilities
 {
-    public static class PacketTestUtilities
+    private static nint _testListener;
+    private static int _testPort;
+    private static readonly List<Socket> _testSocketClients = [];
+
+    public static Span<byte> Compile(this Packet p) => p.Compile(false, out var length).AsSpan(0, length);
+
+    /// <summary>
+    /// Creates a NetState for unit testing.
+    /// Uses a real Socket and RingSocket with actual buffers.
+    /// Must be disposed after use (use 'using' statement).
+    /// </summary>
+    public static NetState CreateTestNetState()
     {
-        public static Span<byte> Compile(this Packet p) =>
-            p.Compile(false, out var length).AsSpan(0, length);
+        NetState.Slice(); // Process disconnects/disposes
+
+        for (var i = _testSocketClients.Count - 1; i >= 0; i--)
+        {
+            var sock = _testSocketClients[i];
+            if (!sock.Connected)
+            {
+                sock.Dispose();
+                _testSocketClients.RemoveAt(i);
+            }
+        }
+
+        var ring = NetState.Ring;
+
+        // Create a test listener if we don't have one (using the ring for RIO-compatible sockets)
+        if (_testListener == 0)
+        {
+            // Disable rate limiter for tests - we don't want connection attempts to be throttled
+            // NetState.DisableRateLimiter();
+
+            _testListener = ring.CreateListener("127.0.0.1", 0, 128);
+            if (_testListener == -1)
+            {
+                throw new InvalidOperationException("Failed to create test listener");
+            }
+
+            _testPort = SocketHelper.GetLocalEndPoint(_testListener)?.Port ?? 0;
+            if (_testPort == 0)
+            {
+                throw new InvalidOperationException("Failed to get test listener port");
+            }
+        }
+
+        // Queue an accept operation
+        ring.PrepareAccept(_testListener, 0, 0, IORingUserData.EncodeAccept());
+        ring.Submit();
+
+        Core._now = DateTime.UtcNow;
+
+        // Create a client socket and connect to trigger the accept
+        var testSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
+        testSocket.Connect(IPAddress.Loopback, _testPort);
+        _testSocketClients.Add(testSocket);
+
+        // Slice until we have a new NetState instance added
+        // AcceptEx is asynchronous, so we may need to wait/retry
+        const int maxRetries = 100;
+        for (var i = 0; i < maxRetries; i++)
+        {
+            NetState.Slice();
+
+            // Get the latest instance connected.
+            foreach (var ns in NetState.Instances)
+            {
+                if (ns.ConnectedOn == Core._now)
+                {
+                    return ns;
+                }
+            }
+
+            // Wait a bit for AcceptEx to complete
+            if (i < maxRetries - 1)
+            {
+                System.Threading.Thread.Sleep(1);
+            }
+        }
 
-        public static NetState CreateTestNetState() => new(
-            new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)
-        );
+        throw new Exception("Failed to slice for test NetState instance after retries");
     }
 }

Projects/Server.Tests/Server.Tests.csproj

@@ -16,6 +16,13 @@
         <DataFiles Include="$(SolutionDir)\Distribution\Data\**" />
         <ProjectReference Include="..\UOContent\UOContent.csproj" />
     </ItemGroup>
+    <!-- Copy native ioring.dll for tests -->
+    <ItemGroup>
+        <Content Include="C:\Repositories\IORingGroup\IORingGroup\runtimes\win-x64\native\ioring.dll" Condition="Exists('C:\Repositories\IORingGroup\IORingGroup\runtimes\win-x64\native\ioring.dll')">
+            <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+            <Link>ioring.dll</Link>
+        </Content>
+    </ItemGroup>
     <Target Name="CopyData" AfterTargets="AfterBuild">
         <Copy SourceFiles="@(DataFiles)" DestinationFolder="$(OutDir)\Data\%(RecursiveDir)" />
     </Target>

Projects/Server.Tests/Tests/Maps/ClientEnumeratorTests.cs

@@ -1,8 +1,8 @@
 using System;
 using System.Collections.Generic;
-using System.Net.Sockets;
 using Server.Accounting;
 using Server.Network;
+using Server.Tests.Network;
 using Xunit;
 
 namespace Server.Tests.Maps;
@@ -356,7 +356,7 @@ public void ClientEnumerator_GetClientsInRange()
     {
         var map = Map.Felucca;
         var center = new Point3D(900, 900, 0);
-        var range = 5;
+        const int range = 5;
 
         var clients = new (NetState, Mobile)[3];
         try
@@ -456,8 +456,8 @@ public Mobile this[int index]
 
     private static (NetState, Mobile) CreateClientWithMobile(Map map, Point3D location)
     {
-        var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
-        var ns = new NetState(socket);
+        // Create test NetState with real socket and buffers
+        var ns = PacketTestUtilities.CreateTestNetState();
 
         // Assign a mock account to avoid null reference issues
         ns.Account = new MockAccount();
@@ -533,16 +533,16 @@ public void ClientEnumerator_NegativeRangeCreates1x1Bounds()
         }
     }
 
-    private static void DeleteAll((NetState, Mobile)[] clients)
+    private static void DeleteAll((NetState state, Mobile m)[] clients)
     {
         for (var i = 0; i < clients.Length; i++)
         {
-            if (clients[i].Item1 != null)
+            if (clients[i].state != null)
             {
-                clients[i].Item1.Mobile = null;
-                clients[i].Item1.Disconnect("Test cleanup");
+                clients[i].state.Mobile = null;
+                clients[i].state.Dispose();
             }
-            clients[i].Item2?.Delete();
+            clients[i].m?.Delete();
         }
     }
 }

Projects/Server.Tests/Tests/Maps/MapSelectionTests.cs

@@ -4,7 +4,7 @@
 using System.Text.Json.Serialization;
 using System.Text.Json;
 
-namespace Server.Tests.Tests.Maps
+namespace Server.Tests.Maps
 {
     public class MapSelectionTests
     {

Projects/Server.Tests/Tests/Network/Packets/Outgoing/AccountPacketTests.cs

@@ -92,7 +92,7 @@ public void TestChangeCharacter()
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendChangeCharacter(account);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -105,7 +105,7 @@ public void TestClientVersionReq()
 
         ns.SendClientVersionRequest();
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -117,7 +117,7 @@ public void TestDeleteResult()
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendCharacterDeleteResult(DeleteResultType.BadRequest);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -129,7 +129,7 @@ public void TestPopupMessage()
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendPopupMessage(PMMessage.LoginSyncError);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -156,7 +156,7 @@ public void TestSupportedFeatures(ProtocolChanges protocolChanges)
         var expected = new SupportedFeatures(ns).Compile();
         ns.SendSupportedFeature();
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -177,7 +177,7 @@ public void TestLoginConfirm()
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendLoginConfirmation(m);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -189,7 +189,7 @@ public void TestLoginComplete()
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendLoginComplete();
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -214,7 +214,7 @@ public void TestCharacterListUpdate()
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendCharacterListUpdate(account);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -248,7 +248,7 @@ public void TestCharacterList70130()
 
         ns.SendCharacterList();
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -281,7 +281,7 @@ public void TestCharacterListOld()
 
         ns.SendCharacterList();
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -294,7 +294,7 @@ public void TestAccountLoginRej()
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendAccountLoginRejected(reason);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -313,23 +313,23 @@ public void TestAccountLoginAck()
 
         ns.SendAccountLoginAck();
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
     [Fact]
     public void TestPlayServerAck()
     {
         var si = new ServerInfo("Test Server", 0, TimeZoneInfo.Local, IPEndPoint.Parse("127.0.0.1"));
-        var authId = 0x123456;
+        const int authId = 0x123456;
 
         var expected = new PlayServerAck(si, authId).Compile();
 
         using var ns = PacketTestUtilities.CreateTestNetState();
 
         ns.SendPlayServerAck(si, authId);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 }

Projects/Server.Tests/Tests/Network/Packets/Outgoing/CombatPacketTests.cs

@@ -17,7 +17,7 @@ public void TestSwing()
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendSwing(attacker, defender);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -29,7 +29,7 @@ public void TestSetWarMode(bool warmode)
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendSetWarMode(warmode);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -43,7 +43,7 @@ public void TestChangeCombatant()
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendChangeCombatant(serial);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 }