GO-MFP

Warning: this project is work in progress and under the intensive development.

This project contains the foundation of the behavior-accurate simulator for multi-function printers (MFPs) that supports at least IPP 2.x for printing, eSCL and WSD for scanning, and DNS-SD and WS-Discovery for device discovery.

This simulator will consist of a core simulation engine that provides reference implementations of the aforementioned protocols, along with a customization engine that allows for the expression of implementation details specific to individual devices without the need to reimplement common functionalities repeatedly.

For the purpose of implementation of the MFP core simulation engine it contains many libraries (Go packages) that are aimed to be a part of the simulator, but can be useful as a general-purpose libraries as well.

It contains (partially done for now) the fairly complete eSCL and WSD WS-Scan implementations, DNS-SD and WS-Discovery published and querier, smart device discovery engine, able to bind various instances of the same device together, representing them as a sub-units of a single physical device (IPP/IPPS, AppSocket AKA JetDirect and LPD for printing, eSCL and WSD for scanning), based on the similar work previously done for scanners in the sane-airscan project and much more.

The ultimate goal of this project, among writing the MFP simulator, is to implement a comprehensive Go toolkit for printing and scanning on Linux and UNIX-like systems.

Building

Building is quite straightforward: just type make at the root directory.

It requires the following development packages to be installed:

• Golang compiler
• gcc compiler
• avahi-libs for the DNS-SD
• libjpeg, libpng for image conversion
• libusb
• libppd
• Python3 (cpython) development package

It also requires some external Go libraries, but if your build computer is connected to the network, they will be downloaded and cached automatically at the first build attrmpt:

• github.com/OpenPrinting/go-avahi - Go binding for Avahi
• github.com/OpenPrinting/goipp - Low-level IPP implementation
• github.com/google/go-cmp - used only for testing
• github.com/peterh/liner - line editor for the interactive shell

Building and running on Windows (WSL2)

The project builds and runs under the Windows Subsystem for Linux (WSL2). The USB device emulation relies on the USB/IP kernel support (the vhci_hcd module), which recent WSL2 kernels already include, so a separate virtual machine is not required.

The instructions below were tested on Ubuntu 24.04 under WSL2 (kernel 6.6.87 microsoft-standard-WSL2).

Install the build dependencies together with the USB/IP client tools:

sudo apt-get install -y \
    golang gcc pkg-config make \
    libavahi-client-dev libjpeg-dev libpng-dev \
    libusb-1.0-0-dev python3-dev \
    linux-tools-generic linux-tools-common linux-tools-virtual \
    usbutils

Note that Ubuntu has no standalone usbip package: the usbip client is shipped as part of linux-tools and installed under /usr/lib/linux-tools-*/usbip. Put it on the PATH, for example:

sudo ln -sf "$(ls /usr/lib/linux-tools-*/usbip | head -1)" \
    /usr/local/bin/usbip

Ubuntu does not package libppd, which is needed by a full make. To just build and try the virtual MFP simulator, build only that command:

go build -o mfp-virtual ./cmd/mfp-virtual

Run the simulator in USB/IP mode:

./mfp-virtual --usbip -d

In another terminal, load the kernel module and attach the emulated device:

sudo modprobe vhci-hcd
sudo usbip attach -r localhost -b 1-1

The virtual MFP now appears as a real USB device (lsusb lists it as OpenPrinting Virtual MFP) and can be driven by the usual Linux printing and scanning stack, including ipp-usb.

Source tree organization

import github.com/OpenPrinting/go-mfp/abstract"

This package contains definitions for the abstract (protocol-independent) printer and scanner.

import github.com/OpenPrinting/go-mfp/argv"

This is a general-purpose library for parsing command options.

import github.com/OpenPrinting/go-mfp/cmd"

This is a root directory for all commands (executable files) build as a part of this project.

import github.com/OpenPrinting/go-mfp/cmd/mfp"

TODO

import github.com/OpenPrinting/go-mfp/cmd/mfp-cups"

This is the command-line CUPS client.

import github.com/OpenPrinting/go-mfp/cmd/mfp-discover"

This is the command-line device discovery tool.

import github.com/OpenPrinting/go-mfp/cmd/mfp-proxy"

This is the MFP masquerading tool. It allows to re-expose existent MFP device under the different name or different IP address and to sniff its traffic (which is convenient tool for troubleshooting).

import github.com/OpenPrinting/go-mfp/cmd/mfp-shell"

This is interactive shell for all mfp-XXX commands.

import github.com/OpenPrinting/go-mfp/cmd/mfp-virtual"

This is the vurtual MFP simulator.

import github.com/OpenPrinting/go-mfp/cups"

This is the CUPS API library. It uses the IPP protocol to communicate with the CUPS server.

import github.com/OpenPrinting/go-mfp/discovery"

This is the smart MFP discovery library.

import github.com/OpenPrinting/go-mfp/internal"

This is the collection of internally used support libraries. These libraries are not exposed via the GO-MFP API.

import github.com/OpenPrinting/go-mfp/log"

This is the logging library, used across the project.

import github.com/OpenPrinting/go-mfp/proto"

This is the collection of packages, that implement MFP protocols.

import github.com/OpenPrinting/go-mfp/proto/escl"

This is the eSCL protocol implementation.

import github.com/OpenPrinting/go-mfp/proto/ipp"

This is the high-level IPP protocol implementation.

import github.com/OpenPrinting/go-mfp/proto/wsd"

This is the WS-Discovery protocol implementation, querier and responder.

import github.com/OpenPrinting/go-mfp/transport"

This is the low-level transport library, used for communication with devices.

import github.com/OpenPrinting/go-mfp/util"

This is the collection of internally used support libraries. These libraries are exposed via the GO-MFP API.