feat: Upgrades networking to use io_uring.

[kamronbatman]

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

[Copilot]

Pull request overview

This pull request upgrades the networking infrastructure from a traditional socket polling approach to io_uring-based I/O on Linux and Windows RIO (Registered I/O). The changes introduce a new C native library for Windows RIO support, replace the core networking components (TcpServer, Pipe), and refactor NetState to use the new IORingGroup package.

Changes:

• Adds new C native library (ioring.c/h) implementing Windows RIO with io_uring-compatible API
• Replaces TcpServer and Pipe classes with new IORingGroup-based socket manager
• Refactors NetState to use RingSocket/RingSocketManager instead of raw Socket/Pipe
• Updates all test infrastructure to work with new networking model

Reviewed changes

Copilot reviewed 59 out of 59 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
Projects/ioring/ioring.vcxproj	Visual Studio project for Windows RIO native library
Projects/ioring/ioring.h	Header defining io_uring-compatible API for Windows RIO
Projects/ioring/ioring.c	C implementation of Windows RIO with AcceptEx support
Projects/Server/Network/SocketHelper.cs	Platform-specific utilities for socket handle introspection
Projects/Server/Network/NetState/NetState.cs	Core NetState refactoring for new networking model
Projects/Server/Network/NetState/NetState.Network.cs	New networking layer with RingSocketManager
Projects/Server/Server.csproj	Package reference update from PollGroup to IORingGroup
Projects/UOContent/Misc/ServerList.cs	Updated to use new LocalEndPoint property
Projects/Server.Tests/Helpers/PacketTestUtilities.cs	Test helper updates for new socket creation
Various test files	Updated SendPipe.Reader calls to SendBuffer.GetReadSpan

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