me_proxy: Dynamic OMCI Managed Entity Proxy for OpenWrt

Abstract

Testing interoperability between ONUs and various GPON/XGSPON OLTs often requires handling vendor-specific Managed Entities (ME). Traditionally, supporting a new ME requires modifying the core OMCI application and performing a full Firmware (FW) upgrade—a process that is time-consuming and risky for field deployments.

me_proxy is an experimental project designed to solve this. Leveraging OpenWrt’s powerful opkg package management and high-performance Lua integration, me_proxy allows ODMs and Telecommunications providers to customize ME behavior on-the-fly. By simply installing a specific .ipk plugin, the system can support new MEs without a reboot or firmware flash.

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System Architecture

The system is divided into three layers: the CLI Trigger, the Communication Bridge, and the Logic Engine.

1. omci_pkt (CLI Tool): A lightweight test tool that sends OMCI commands (Get/Set) to a Named Pipe (FIFO).
2. omci_app (Daemon): Reads from the FIFO and acts as a ubus client, forwarding requests to the core proxy.
3. me_proxy (Core Engine):
   • C Core: Manages ubus registration and system signals.
   • Lua Binding: Provides an abstraction layer for ME logic.
   • Hot-Reload (SIGHUP): Supports reloading Lua plugins without restarting the process.
4. Plugins (Lua): User-defined logic stored in /etc/omci/plugins/, distributed via independent ipk packages (e.g., Mesh Control, Robot Manager).

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Request Control Flow

The following diagram illustrates the lifecycle of an omci_pkt set command as it traverses from the CLI to the Lua callback.

Workflow Steps:

1. Trigger: User executes omci_pkt set 33100....
2. IPC: The command is written to /tmp/omci_fifo.
3. Dispatch: omci_app invokes the omci.me_proxy set method via ubus.
4. Parsing: me_proxy parses the attribute mask and looks up the corresponding handler.
5. Execution: The C core calls the specific Lua function defined in the plugin (e.g., robot_manager.lua).
6. Response: The result is bubbled back up to the CLI tool.

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Key Features

• Decoupled Logic: Keep the stable C core intact while iterating on business logic in Lua.
• Dynamic Deployment: Use opkg install to add support for new MEs (e.g., Mesh, VoIP, or proprietary OAM).
• Zero Downtime: Supports SIGHUP signal to refresh the Lua environment without dropping ubus connections.
• Lightweight: Minimal memory footprint, ideal for embedded resource-constrained ONUs.

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Installation & Usage

1. Start the Proxy

/etc/init.d/me_proxy start

2. Test an Unsupported ME

./omci_pkt get 33000 0 c000
# Result: 4 (Not Supported)

3. Install Plugin and Hot-Reload

opkg install me-33000-mesh
# The postinst script automatically sends SIGHUP to me_proxy

4. Verify Support

./omci_pkt get 33000 0 c000
# Result: 0 (Success)

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Future Experiments

• Extended Schema Validation: Using Lua tables to define ME constraints (Range, Type).
• MIB Persistence: Allowing Lua plugins to store state across reboots via UCI.