Development

Learn how to contribute to VyOS.

Architecture overview

VyOS source code is hosted on GitHub in the VyOS organization: https://github.com/vyos

VyOS is composed of multiple modules spread across different repositories. Some modules contain forks of upstream packages and are periodically synced. VyOS consolidates most packages into the vyos-1x repository while maintaining a consistent structure. The base code is being rewritten from Perl and Bash to Python using an XML-based CLI interface definition.

VyOS ISO build scripts are hosted in the vyos-build repository. See the vyos-build repository README.md file for more information on building VyOS ISO images.

Contributing code

Warning

You must sign the Contributor License Agreement for your contributions to be accepted.

VyOS is open-source and welcomes patches. All submissions must adhere to these guidelines:

Determining package ownership

To determine which VyOS package contains a file you want to modify, use Debian’s dpkg -S command on your running VyOS installation.

Submitting your code

Fork the repository and submit a GitHub pull request. This is the preferred way to contribute changes to VyOS.

To fork a VyOS repository:

  1. Append /fork to the repository URL on GitHub. For example, to fork vyos-1x, use: https://github.com/vyos/vyos-1x/fork

  2. Clone your fork or add it as a remote to your local repository:

    • Clone: git clone https://github.com/<user>/vyos-1x.git

    • Add remote: git remote add myfork https://github.com/<user>/vyos-1x.git

  1. Configure your Git identity:

    git config --global user.name "J. Random Hacker"
git config --global user.email "jrhacker@example.net"

  2. Make your changes and add files to the Git index:

    • Single file: git add myfile

    • Directory: git add somedir/*

  3. Commit your changes with a meaningful headline and Phabricator reference:

    git commit

  4. Push to your fork and create a GitHub pull request:

    git push

Alternatively, you can export commits as patches and send them to maintainers@vyos.net or attach them directly to the Phabricator task:

  • Export last commit: git format-patch

  • Export last two commits: git format-patch -2

Commit messages

For guidance on writing commit messages, review the file history with git log path/to/file.txt.

Every change must be associated with a task number (prefixed with T) and a component. If no bug report or feature request exists for your changes, create a Phabricator task first. Reference the task ID in your commit message:

  • ddclient: T1030: auto create runtime directories

  • Jenkins: add current Git commit ID to build description

If your pull request lacks a Phabricator reference, maintainers will request that you amend the commit message.

Writing good commit messages

Follow the format described in the Git documentation and Chris Beams’ guide.

Commit message format:

  1. Summary line (50 characters recommended, 80 maximum): Include the component prefix and Phabricator reference (for example, snmp: T1111: or ethernet: T2222:). Concatenate multiple components with colons (for example, snmp: ethernet: T3333).

  2. Blank line: Separate the summary from the body. This blank line is critical.

  1. Message body with details:

    • Describe what changed, why, and how. This helps with git bisect.

    • Wrap text at 72 characters for readability with git log on an 80x25 terminal.

    • Reference previous commits when applicable: After commit abcd12ef ("snmp: this is a headline") a Python import statement is missing, throwing the following exception: ABCDEF

  2. Cherry-pick option: Always use the -x option when back-porting or forward-porting commits:

    git cherry-pick -x <commit>

    This appends (cherry picked from commit <ID>) to the commit message, making bisecting easier.

  3. Single responsibility: Each commit must be self-contained. Do not fix multiple bugs in a single commit. Use git add --patch to stage only the parts related to one issue.

Constraints:

  • Bugfixes are only accepted for packages other than https://github.com/vyos/vyos-1x. New functionality must use the new XML/Python interface, not old-style templates (node.def files and Perl/Bash code).

Coding guidelines

VyOS maintains consistent coding standards to help contributors navigate the codebase and understand its logic.

Formatting

  • Python: Use 4 spaces per indentation level. Tabs must not be used.

  • XML: Use 2 spaces per indentation level. Tabs must not be used.

Use tools like VIM extensions (xmllint) to enforce correct indentation. Add this to your .vimrc file:

au FileType xml setlocal equalprg=xmllint\ --format\ --recover\ -\ 2>/dev/null

Then use gg=G in command mode to run the linter.

Text generation

Use a template processor for generating config files:

  • Jinja2 is the default template processor for VyOS code.

  • Built-in string formatting may be used for simple line-oriented formats (for example, iptables rules) where every line is self-contained.

  • Template processors must be used for structured, multi-line formats (for example, ISC DHCPd configuration).

Python code

Configuration scripts and operation mode scripts written in Python3 should follow these guidelines:

  • Wrap lines at 80 characters. This improves readability when browsing GitHub on mobile devices and reads well in side-by-side diffs.

Structure your scripts with these functions:

#!/usr/bin/env python3
#
# Copyright (C) 2020 VyOS maintainers and contributors
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 or later as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

import sys

from vyos.config import Config
from vyos import ConfigError

def get_config(config=None):
    if config:
        conf = config
    else:
        conf = Config()

    # Base path to CLI nodes
    base = ['...', '...']
    # Convert the VyOS config to an abstract internal representation
    config_data = conf.get_config_dict(base, key_mangling=('-', '_'), get_first_key=True)
    return config_data

def verify(config):
    # Verify that configuration is valid
    if invalid:
        raise ConfigError("Descriptive message")

def generate(config):
    # Generate daemon configs
    pass

def apply(config):
    # Apply the generated configs to the live system
    pass

try:
    c = get_config()
    verify(c)
    generate(c)
    apply(c)
except ConfigError as e:
    print(e)
    sys.exit(1)

get_config(): This function converts a VyOS config object to an abstract internal representation. No other function may call the vyos.config.Config object directly. Limiting config reads to one function makes it easier to modify the config syntax in the future. Additionally, this design improves testability since you can construct an internal representation by hand rather than mocking the entire config subsystem.

verify(): This function validates the internal representation. It must raise ConfigError with a descriptive message if the config is invalid. It must not make any changes to the system. This design enables future features like commit dry-run (“commit test” as in JunOS) where the system can abort a commit before making changes.

generate(): This function generates config files for system components.

apply(): This function applies the generated configuration to the live system. Prefer non-disruptive reload when possible. Disruptive operations like daemon restarts are acceptable only when:

  • The component does not support non-disruptive reload, or

  • The expected service degradation is minimal (for example, auxiliary services like LLDPd)

For high-impact services (VPN daemons, routing protocols), make effort to determine if changes can be applied non-disruptively before resorting to restarts.

Never modify active configuration directly unless absolutely necessary. Instead, generate configuration files and apply them with a single command like service reload through systemd. For example, save iptables rules to a file and load them with iptables-restore rather than executing iptables commands one by one.

The apply() and generate() functions may raise ConfigError if the daemon fails to start with the updated config. However, this is not a substitute for proper config validation in the verify() function. Make reasonable effort to verify that generated configuration is valid and will be accepted by the daemon, including cross-checks with other VyOS configuration subtrees when necessary.

Exceptions like VyOSError (raised by vyos.config.Config on improper operations) should not be silenced or caught. While this may produce less polished error output for users, it generates better bug reports and helps maintainers debug issues.

For reference implementations, see ntp.py or interfaces-bonding.py (for tag nodes) in the vyos-1x repository.

Other considerations: vyos-configd

All scripts now run under the config daemon and must conform to these requirements:

  1. The signature and first four lines of get_config(...) must be as specified above.

  2. Each of get_config, verify, apply, and generate must appear with the correct signatures, even if they are a no-op.

  3. Config objects other than those in get_config must not appear.

  4. The legacy function my_set must not appear. Modifications to active config should not appear in new code (alternative mechanisms may be used if absolutely necessary).

XML for CLI definitions

XML interface definitions define the VyOS CLI structure. Before VyOS 1.2 (crux), these files were created manually. After a redesign, new-style templates are automatically generated from XML input files.

VyOS interface definitions come with a RelaxNG schema located in the vyos-1x repository. This schema is a modified version from VyConf (VyOS 2.0). VyOS 1.2.x interface definitions are reusable in future VyOS versions with minimal changes.

Schemas provide two benefits:

  • Complete grammar verification

  • Automatic validation against the schema

The build-command-templates script converts XML definitions to old-style templates and verifies them against the schema. A bad definition causes the package build to fail. While the XML format is verbose, no other format provides this level of verification. Specialized XML editors can help manage verbosity. .. start_vyoslinter

Example XML interface definition:

<?xml version="1.0"?>
<!-- Cron configuration -->
<interfaceDefinition>
  <node name="system">
    <children>
      <node name="task-scheduler">
        <properties>
          <help>Task scheduler settings</help>
        </properties>
        <children>
          <tagNode name="task" owner="${vyos_conf_scripts_dir}/task_scheduler.py">
            <properties>
              <help>Scheduled task</help>
              <valueHelp>
                <format>&lt;string&gt;</format>
                <description>Task name</description>
              </valueHelp>
              <priority>999</priority>
            </properties>
            <children>
              <leafNode name="crontab-spec">
                <properties>
                  <help>UNIX crontab time specification string</help>
                </properties>
              </leafNode>
              <leafNode name="interval">
                <properties>
                  <help>Execution interval</help>
                  <valueHelp>
                    <format>&lt;minutes&gt;</format>
                    <description>Execution interval in minutes</description>
                  </valueHelp>
                  <valueHelp>
                    <format>&lt;minutes&gt;m</format>
                    <description>Execution interval in minutes</description>
                  </valueHelp>
                  <valueHelp>
                    <format>&lt;hours&gt;h</format>
                    <description>Execution interval in hours</description>
                  </valueHelp>
                  <valueHelp>
                    <format>&lt;days&gt;d</format>
                    <description>Execution interval in days</description>
                  </valueHelp>
                  <constraint>
                    <regex>[1-9]([0-9]*)([mhd]{0,1})</regex>
                  </constraint>
                </properties>
              </leafNode>
              <node name="executable">
                <properties>
                  <help>Executable path and arguments</help>
                </properties>
                <children>
                  <leafNode name="path">
                    <properties>
                      <help>Path to executable</help>
                    </properties>
                  </leafNode>
                  <leafNode name="arguments">
                    <properties>
                      <help>Arguments passed to the executable</help>
                    </properties>
                  </leafNode>
                </children>
              </node>
            </children>
          </tagNode>
        </children>
      </node>
    </children>
  </node>
</interfaceDefinition>

XML definitions are purely declarative and contain no logic. All logic for generating config files, restarting services, and related tasks is implemented in configuration scripts.

Template Processors

XML interface definition files use the .xml.in file extension (implemented in T1843). These files use the GCC preprocessor to reduce code duplication in common areas:

  • VIF (including VIF-S and VIF-C)

  • Address configuration

  • Description

  • Enabled/Disabled state

Instead of repeating XML nodes, use include files with predefined features:

The .in files are preprocessed and stored in the interface-definitions folder. The scripts/build-command-templates script then operates on this folder to generate all required CLI nodes.

Example preprocessor output:

$ make interface_definitions
install -d -m 0755 build/interface-definitions
install -d -m 0755 build/op-mode-definitions
Generating build/interface-definitions/intel_qat.xml from interface-definitions/intel_qat.xml.in
Generating build/interface-definitions/interfaces-bonding.xml from interface-definitions/interfaces-bonding.xml.in
Generating build/interface-definitions/cron.xml from interface-definitions/cron.xml.in
Generating build/interface-definitions/pppoe-server.xml from interface-definitions/pppoe-server.xml.in
Generating build/interface-definitions/mdns-repeater.xml from interface-definitions/mdns-repeater.xml.in
Generating build/interface-definitions/tftp-server.xml from interface-definitions/tftp-server.xml.in
[...]

Command Definition Guidelines

Use of Numbers

Avoid using numbers in command names unless the number is part of a protocol name or similar. For example, protocols ospfv3 is appropriate, but server-1 is questionable.

Help Strings

Follow these guidelines for consistent, readable help strings:

Capitalization and Punctuation

  • Capitalize the first word of every help string.

  • Do not use a period at the end of help strings.

This standard mirrors network device CLIs and improves aesthetics.

Examples:

  • Good: “Frobnication algorithm”

  • Bad: “frobnication algorithm”

  • Bad: “Frobnication algorithm.”

  • Incorrect: “frobnication algorithm.”

Abbreviations and Acronyms

  • Capitalize all abbreviations and acronyms.

Examples:

  • Good: “TCP connection timeout”

  • Bad: “tcp connection timeout”

  • Bad: “Tcp connection timeout”

  • Capitalize acronyms to distinguish them from normal words.

Examples:

  • Good: RADIUS (remote authentication for dial-in user services)

  • Bad: radius (unless referring to circular distance)

  • Follow accepted spelling conventions for mixed-case abbreviations. If it contains “over” or “version”, use lowercase. Follow RFC or standard spellings when they exist.

Examples:

  • Good: PPPoE, IPsec

  • Bad: PPPOE, IPSEC

  • Bad: pppoe, ipsec

Verbs

  • Avoid verbs. If a verb can be omitted, omit it.

Examples:

  • Good: “TCP connection timeout”

  • Bad: “Set TCP connection timeout”

  • When a verb is essential, use it. For example: “Disable IPv6 forwarding on all interfaces” for set system ipv6 disable-forwarding.

  • Use infinitive form for necessary verbs.

Examples:

  • Good: “Disable IPv6 forwarding”

  • Bad: “Disables IPv6 forwarding”

C++ Backend Code

The VyOS CLI parser combines bash, bash-completion helpers, and the C++ backend library vyatta-cfg. This section references common CLI commands and their C/C++ entry points:

set:

commit: