HAProxyDetector

A lightweight plugin designed to solve the compatibility issue where direct connections are impossible after enabling HAProxy (Proxy Protocol) support on Paper or Velocity.

Core Features

• Mixed Connection Support: Allows servers with proxy-protocol: true to simultaneously receive proxy traffic from HAProxy/frp and direct traffic from players.
• Native Parser Compatibility: Instead of taking over complex protocol parsing, the plugin injects a fake HAProxy V2 header into direct traffic. This "tricks" the server's native parser, allowing all traffic to follow the official, most stable parsing path.
• Zero Configuration / Zero Dependencies: No ProtocolLib required, no whitelist configuration needed. Plug and play.
• Cross-Version Compatibility: Based on Netty-level injection and feature detection, theoretically supports all Minecraft versions with strong cross-version stability.

Why Choose This Plugin?

Traditional HAProxy plugins are often "patch-style," meaning they force support onto servers that don't natively have it. This causes conflicts in modern Paper versions, which already have a more secure built-in implementation.

This plugin adopts an "auxiliary" approach:

1. For frp/Proxy Players: If an existing protocol header is detected, it is passed through directly without interfering with the original IP chain.
2. For Direct Players: If a missing protocol header is detected, a fake header containing the player's real IP is immediately prepended. This allows the server's native parser to extract and apply the player's real address directly.

Supported Platforms

• Paper/Purpur: Theoretically supports all versions with native HAProxy functionality (Tested on 1.20.1 - 1.21.4).
• Velocity: Theoretically supports all 3.0.0+ versions.

Usage

1. Enable Native HAProxy Support:
   • Paper/Purpur: Set proxy-protocol to true in config/paper-global.yml (Newer versions) or paper.yml (Older versions).
   • Velocity: Set haproxy = true in velocity.toml.
2. Install Plugin: Place the plugin JAR in the plugins folder.
3. Restart Server.

Technical Implementation

• Netty ChannelPipeline Injection: Intercepts raw ByteBuf at the very front of the network processing pipeline.
• Feature Detection Logic: Automatically identifies the ServerConnection field in NMS without relying on specific field name obfuscation, providing high robustness across versions.
• Protocol Header Forging: Implements standard HAProxy V2 protocol format injection.