openwrt-composer

An OpenWRT firmware builder which takes input from a YAML manifest.

OpenWRT composer takes a YAML manifest which specifies firmware images to build, including what packages to add/remove from the firmware, and how to configure the firmware. The idea is that the firmware image is regarded as immutable; any change in configuration is achieved by producing a new firmware image and loading that onto the device.

Configuration is specified in the YAML manifest, and leverages the NetJSONConfig package to create valid configuration files which are then baked into the firmware image.

Building of the image itself is done inside a container. Currently the Podman container runtime is used, but adding Docker support is on the TODO list, and wouldn't require much work at all.

This project is still under heavy development. It will probably build you a firmware that will turn your router into a brick.

The concept

The aim is to provide a reliable and simple way to produce custom OpenWRT firmware images which allow device configuration and customization to be "baked in" to the firmware.

As such, the philosophy is to regard the firmware image as immutable; any change in configuration is achieved by producing a new firmware image and loading that onto the device.

The concept is simple:

• Leverage the OpenWRT image builder to build custom firmwares.
• Use a YAML manifest to determine what packages are installed in the firmware
• Use the same YAML manifest to create a configuration for the firmware

As such, a single YAML manifest specifies the contents and configuration of a firmware. That makes it very easy to share and collaborate firmware configurations.

Installation

In the future, the package will be available from PyPi. However, at the moment, you'll need to clone this repository, and then install it via poetry. It is recommended to do this in a Python virtual environment:

python -m venv openwrt-composer
pip install poetry
poetry install

It's recommended to install the package in a

Usage

The command line tool is owc:

$ owc
Usage: owc [OPTIONS] CONFIG_FILE MANIFEST_FILE
Try "owc --help" for help.

The command expects two arguments, both of which should be YAML files. The CONFIG_FILE argument corresponds to a file that configures the tool itself. the MANIFEST_FILE specifies the firmwares to be built.

An example CONFIG_FILE:

work_dir: ./build
openwrt_base_url: https://downloads.openwrt.org/

An example MANIFEST_FILE:

firmwares:
  - target: lantiq
    sub_target: xrx200
    profile:  bt_homehub-v5a
    version: 18.06.1
    name: router
    packages:
      add:
        - dnsmasq-full
      remove:
        - dnsmasq

Firmware Configuration

There are currently two overlapping ways of specifying the configuration of the firmware in the manifest. In both cases, the end result is the same: the firmware contains customized files which configure the device.

Option 1: using the files section in the manifest

The files section of a firmware image specification can specify the contents of files to include in the firmware. An example is shown below:

firmwares:
  - target: lantiq
    sub_target: xrx200
    profile:  bt_homehub-v5a
    version: 18.06.1
    name: router
    packages:
      add:
        - dnsmasq-full
      remove:
        - dnsmasq
    files:
      - path: /etc/motd
        contents: |
          This is a message of the day.

          This is another line in the MOTD.

The mechanism by which these files end up in the firmware is that openwrt-composer writes them to disk and then passes them as the FILES argument when invoking the OpenWRT image builder.

Option 2: using the config section in the manifest

The config section of a firmware image specification is passed through NetJSONConfig to produce a set of configuration files which are then included in the firmware image via the FILES argument of the OpenWRT Image Builder.

A short (incomplete) example is shown below:

firmwares:
  - target: lantiq
    sub_target: xrx200
    profile:  bt_homehub-v5a
    version: 18.06.1
    name: router
    packages:
      add:
        - dnsmasq-full
      remove:
        - dnsmasq
    config:
      interfaces:
        - name: "ppp0"
          type: "other"
          proto: "ppp"
          device: "/dev/usb/modem1"
          username: "user1"
          password: "pwd0123"
          keepalive: 3
          ipv6: True

Note: Since the NetJSONConfig specification allows the inclusion of additional files, in principle this removes the need for the simple files section described above. However, the simplicity of the files method above is attractive, and so we retain that functionality.

Backends

Firmware building is done using OpenWRT image builders running inside a container.

The approach taken is to create a container image for any required (target, sub-target, profile) firmware combination containing the relevant OpenWRT image builder. All of these (target, sub-target, profile) firmware builder images are built from a common base image (currently based on Fedora 31 with the relevant tools installed).

At present, the only container runtime supported is Podman, but Docker support will be added in the near future.