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

Projects/UOContent.Tests/Fixtures/UOContentFixture.cs

@@ -26,6 +26,9 @@ public class UOContentFixture : ICollectionFixture<UOContentFixture>, IDisposabl
         // Load Skills
         SkillsInfo.Configure();
 
+        // Configure networking (initializes RingSocketManager for tests)
+        Server.Network.NetState.Configure();
+
         // Configure / Initialize
         TestMapDefinitions.ConfigureTestMapDefinitions();
 

Projects/UOContent.Tests/Tests/Engines/Chat/ChatPacketTests.cs

@@ -5,7 +5,7 @@ using Xunit;
 
 namespace UOContent.Tests;
 
-[Collection("Sequential Server Tests")]
+[Collection("Sequential UOContent Tests")]
 public class ChatPacketTests
 {
     [Theory]
@@ -18,7 +18,7 @@ public class ChatPacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendChatMessage(lang, number, param1, param2);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 }

Projects/UOContent.Tests/Tests/Engines/Help/TestHelpTopicPacket.cs

@@ -19,7 +19,7 @@ public class TestHelpTopicPacket
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendDisplayHelpTopic(topic, display);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 }

Projects/UOContent.Tests/Tests/Engines/ML Quests/MLQuestPacketTests.cs

@@ -73,7 +73,7 @@ public class MLQuestPacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendRaceChanger(female, race);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -85,7 +85,7 @@ public class MLQuestPacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendCloseRaceChanger();
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 }

Projects/UOContent.Tests/Tests/Engines/Party/PartyPacketTests.cs

@@ -19,7 +19,7 @@ public class PartyPacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendPartyRemoveMember(m);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -40,7 +40,7 @@ public class PartyPacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendPartyRemoveMember(member.Serial, p);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -61,7 +61,7 @@ public class PartyPacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendPartyMemberList(p);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -78,7 +78,7 @@ public class PartyPacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendPartyTextMessage(serial, text, toAll);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -92,7 +92,7 @@ public class PartyPacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendPartyInvitation(m);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 }

Projects/UOContent.Tests/Tests/Engines/Veteran Rewards/Character Statue Maker/CharacterStatuePacketTests.cs

@@ -7,7 +7,7 @@ using Xunit;
 
 namespace UOContent.Tests;
 
-[Collection("Sequential Server Tests")]
+[Collection("Sequential UOContent Tests")]
 public class CharacterStatuePacketTests
 {
     [Theory]
@@ -19,7 +19,7 @@ public class CharacterStatuePacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendStatueAnimation((Serial)s, status, anim, frame);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 }

Projects/UOContent.Tests/Tests/Items/Books/BookPacketTests.cs

@@ -50,7 +50,7 @@ public class BookPacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendBookCover(m, book);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -87,7 +87,7 @@ public class BookPacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendBookContent(book);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 }

Projects/UOContent.Tests/Tests/Items/Bulletin Boards/BulletinBoardPacketTests.cs

@@ -23,7 +23,7 @@ public class BulletinBoardPacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendBBDisplayBoard(bb);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -50,7 +50,7 @@ public class BulletinBoardPacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendBBMessage(bb, msg, content);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 }

Projects/UOContent.Tests/Tests/Items/Games/Mahjong/MahjongPacketTests.cs

@@ -19,7 +19,7 @@ public class MahjongPacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendMahjongJoinGame(game);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -39,7 +39,7 @@ public class MahjongPacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendMahjongPlayersInfo(game, m);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -57,7 +57,7 @@ public class MahjongPacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendMahjongGeneralInfo(game);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -77,7 +77,7 @@ public class MahjongPacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendMahjongTilesInfo(game, m);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -97,7 +97,7 @@ public class MahjongPacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendMahjongTileInfo(game.Tiles[0], m);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -111,7 +111,7 @@ public class MahjongPacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendMahjongRelieve(game);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 }

Projects/UOContent.Tests/Tests/Items/Maps/TestMapItemPackets.cs

@@ -24,7 +24,7 @@ public class TestMapItemPackets
             (Packet)new MapDetailsNew(mapItem) : new MapDetails(mapItem)).Compile();
         ns.SendMapDetails(mapItem);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -42,7 +42,7 @@ public class TestMapItemPackets
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendMapCommand(mapItem, command, x, y, number > 0);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 }

Projects/UOContent.Tests/Tests/Items/Misc/Corpses/CorpsePacketTests.cs

@@ -26,7 +26,7 @@ public class CorpsePacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendCorpseEquip(m, c);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -50,7 +50,7 @@ public class CorpsePacketTests
 
         ns.SendCorpseContent(m, c);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 }

Projects/UOContent.Tests/Tests/Items/Weapons/Abilities/WeaponAbilityPacketTests.cs

@@ -20,7 +20,7 @@ public class WeaponAbilityPacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendToggleSpecialAbility(abilityId, active);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -32,7 +32,7 @@ public class WeaponAbilityPacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendClearWeaponAbility();
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 }

Projects/UOContent.Tests/Tests/Multis/Boats/BoatPacketTests.cs

@@ -59,7 +59,7 @@ public class BoatPacketTests
 
         ns.SendMoveBoatHS(boat, list, d, speed, xOffset, yOffset);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -103,7 +103,7 @@ public class BoatPacketTests
 
         ns.SendDisplayBoatHS(beholder, boat);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 

Projects/UOContent.Tests/Tests/Multis/Houses/HousePacketTests.cs

@@ -20,7 +20,7 @@ public class HousePacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendBeginHouseCustomization((Serial)serial);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -33,7 +33,7 @@ public class HousePacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendEndHouseCustomization((Serial)serial);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -47,7 +47,7 @@ public class HousePacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendDesignStateGeneral((Serial)serial, revision);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 

Projects/UOContent.Tests/Tests/Network/Packets/ArrowPacketTests.cs

@@ -14,7 +14,7 @@ public class ArrowPacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendCancelArrow(0, 0, Serial.Zero);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -29,7 +29,7 @@ public class ArrowPacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendSetArrow(x, y, Serial.Zero);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -47,7 +47,7 @@ public class ArrowPacketTests
         ns.ProtocolChanges = ProtocolChanges.HighSeas;
         ns.SendCancelArrow(x, y, serial);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -65,7 +65,7 @@ public class ArrowPacketTests
         ns.ProtocolChanges = ProtocolChanges.HighSeas;
         ns.SendSetArrow(x, y, serial);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 }

Projects/UOContent.Tests/Tests/Network/Packets/BuffIconPacketTests.cs

@@ -24,7 +24,7 @@ public class BuffIconPacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendAddBuffPacket((Serial)mob, iconID, titleCliloc, secondaryCliloc, args, (int)timeSpan.TotalMilliseconds);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -38,7 +38,7 @@ public class BuffIconPacketTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendRemoveBuffPacket(m, buffIcon);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 }

Projects/UOContent.Tests/Tests/Skills/SkillPacketsTests.cs

@@ -27,7 +27,7 @@ public class SkillPacketsTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendSkillChange(skill);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 
@@ -45,7 +45,7 @@ public class SkillPacketsTests
         using var ns = PacketTestUtilities.CreateTestNetState();
         ns.SendSkillsUpdate(skills);
 
-        var result = ns.SendPipe.Reader.AvailableToRead();
+        var result = ns.SendBuffer.GetReadSpan();
         AssertThat.Equal(result, expected);
     }
 }