Process & Workflow

FRR is a large project developed by many different groups. This section documents standards for code style & quality, commit messages, pull requests and best practices that all contributors are asked to follow.

This chapter is “descriptive/post-factual” in that it documents pratices that are in use; it is not “definitive/pre-factual” in prescribing practices. This means that when a procedure changes, it is agreed upon, then put into practice, and then documented here. If this document doesn’t match reality, it’s the document that needs to be updated, not reality.

Mailing Lists

The FRR development group maintains multiple mailing lists for use by the community. Italicized lists are private.

Topic List
Development dev@lists.frrouting.org
Users & Operators frog@lists.frrouting.org
Announcements announce@lists.frrouting.org
Security security@lists.frrouting.org
Technical Steering Committee tsc@lists.frrouting.org

The Development list is used to discuss and document general issues related to project development and governance. The public Slack instance and weekly technical meetings provide a higher bandwidth channel for discussions. The results of such discussions must be reflected in updates, as appropriate, to code (i.e., merges), GitHub issues, and for governance or process changes, updates to the Development list and either this file or information posted at https://frrouting.org/.

Development & Release Cycle

Development

Merging Git branches into a central trunk

Rough outline of FRR development workflow

The master Git for FRR resides on GitHub.

There is one main branch for development, master. For each major release (2.0, 3.0 etc) a new release branch is created based on the master. Significant bugfixes should be backported to upcoming and existing release branches no more than 1 year old. As a general rule new features are not backported to release branches.

Subsequent point releases based on a major branch are handled with git tags.

Releases

FRR employs a <MAJOR>.<MINOR>.<BUGFIX> versioning scheme.

MAJOR
Significant new features or multiple minor features. The addition of a new routing protocol or daemon would fall under this class.
MINOR
Small features, e.g. options for automatic BGP shutdown.
BUGFIX
Fixes for actual bugs and/or security issues.

We will pull a new development branch for the next release every 4 months. The current schedule is Feb/June/October 1. The decision for a MAJOR/MINOR release is made at the time of branch pull based on what has been received the previous 4 months. The branch name will be dev/MAJOR.MINOR. At this point in time the master branch and this new branch, configure.ac, documentation and packaging systems will be updated to reflect the next possible release name to allow for easy distinguishing.

After one month the development branch will be renamed to stable/MAJOR.MINOR. The branch is a stable branch. This process is not held up unless a crash or security issue has been found and needs to be addressed. Issues being fixed will not cause a delay.

Bugfix releases are made as needed at 1 month intervals until the next MAJOR.MINOR release branch is pulled. Depending on the severity of the bugs, bugfix releases may occur sooner.

Bugfixes are applied to the two most recent releases. Security fixes are backported to all releases less than or equal to at least one year old. Security fixes may also be backported to older releases depending on severity.

Long term support branches ( LTS )

This kind of branch is not yet officially supported, and need experimentation before being effective.

Previous definition of releases prevents long term support of previous releases. For instance, bug and security fixes are not applied if the stable branch is too old.

Because the FRR users have a need to backport bug and security fixes after the stable branch becomes too old, there is a need to provide support on a long term basis on that stable branch. If that support is applied on that stable branch, then that branch is a long term support branch.

Having a LTS branch requires extra-work and requires one person to be in charge of that maintenance branch for a certain amount of time. The amount of time will be by default set to 4 months, and can be increased. 4 months stands for the time between two releases, this time can be applied to the decision to continue with a LTS release or not. In all cases, that time period will be well-defined and published. Also, a self nomination from a person that proposes to handle the LTS branch is required. The work can be shared by multiple people. In all cases, there must be at least one person that is in charge of the maintenance branch. The person on people responsible for a maintenance branch must be a FRR maintainer. Note that they may choose to abandon support for the maintenance branch at any time. If no one takes over the responsibility of the LTS branch, then the support will be discontinued.

The LTS branch duties are the following ones:

  • organise meetings on a (bi-)weekly or monthly basis, the handling of issues and pull requested relative to that branch. When time permits, this may be done during the regularly scheduled FRR meeting.
  • ensure the stability of the branch, by using and eventually adapting the checking the CI tools of FRR ( indeed, maintaining may lead to create maintenance branches for topotests or for CI).

It will not be possible to backport feature requests to LTS branches. Actually, it is a false good idea to use LTS for that need. Introducing feature requests may break the paradigm where all more recent releases should also include the feature request. This would require the LTS maintainer to ensure that all more recent releases have support for this feature request. Moreover, introducing features requests may result in breaking the stability of the branch. LTS branches are first done to bring long term support for stability.

Changelog

The changelog will be the base for the release notes. A changelog entry for your changes is usually not required and will be added based on your commit messages by the maintainers. However, you are free to include an update to the changelog with some better description.

Submitting Patches and Enhancements

FRR accepts patches from two sources:

  • Email (git format-patch)
  • GitHub pull request

Contributors are highly encouraged to use GitHub’s fork-and-PR workflow. It is easier for us to review it, test it, try it and discuss it on GitHub than it is via email, thus your patch will get more attention more quickly on GitHub.

The base branch for new contributions and non-critical bug fixes should be master. Please ensure your pull request is based on this branch when you submit it.

GitHub Pull Requests

The preferred method of submitting changes is a GitHub pull request. Code submitted by pull request will be automatically tested by one or more CI systems. Once the automated tests succeed, other developers will review your code for quality and correctness. After any concerns are resolved, your code will be merged into the branch it was submitted against.

The title of the pull request should provide a high level technical summary of the included patches. The description should provide additional details that will help the reviewer to understand the context of the included patches.

Patch Submission via Mailing List

As an alternative submission method, a patch can be mailed to the development mailing list. Patches received on the mailing list will be picked up by Patchwork and tested against the latest development branch.

The recommended way to send the patch (or series of NN patches) to the list is by using git send-email as follows (assuming they are the N most recent commit(s) in your git history):

git send-email -NN --annotate [email protected]

If your commits do not already contain a Signed-off-by line, then use the following command to add it (after making sure you agree to the Developer Certificate of Origin as outlined above):

git send-email -NN --annotate --signoff [email protected]

Submitting multi-commit patches as a GitHub pull request is strongly encouraged and increases the probability of your patch getting reviewed and merged in a timely manner.

License for Contributions

FRR is under a “GPLv2 or later” license. Any code submitted must be released under the same license (preferred) or any license which allows redistribution under this GPLv2 license (eg MIT License). It is forbidden to push any code that prevents from using GPLv3 license. This becomes a community rule, as FRR produces binaries that links with Apache 2.0 libraries. Apache 2.0 and GPLv2 license are incompatible, if put together. Please see http://www.apache.org/licenses/GPL-compatibility.html for more information. This rule guarantees the user to distribute FRR binary code without any licensing issues.

Pre-submission Checklist

  • Format code (see Code Formatting)
  • Verify and acknowledge license (see License for Contributions)
  • Ensure you have properly signed off (see Signing Off)
  • Test building with various configurations:
    • buildtest.sh
  • Verify building source distribution:
    • make dist (and try rebuilding from the resulting tar file)
  • Run unit tests:
    • make test
  • In the case of a major new feature or other significant change, document plans for continued maintenance of the feature

Signing Off

Code submitted to FRR must be signed off. We have the same requirements for using the signed-off-by process as the Linux kernel. In short, you must include a Signed-off-by tag in every patch.

Signed-off-by is a developer’s certification that they have the right to submit the patch for inclusion into the project. It is an agreement to the Developer’s Certificate of Origin. Code without a proper Signed-off-by line cannot and will not be merged.

If you are unfamiliar with this process, you should read the official policy at kernel.org. You might also find this article about participating in the Linux community on the Linux Foundation website to be a helpful resource.

In short, when you sign off on a commit, you assert your agreement to all of the following:

Developer's Certificate of Origin 1.1

By making a contribution to this project, I certify that:

(a) The contribution was created in whole or in part by me and I
    have the right to submit it under the open source license
    indicated in the file; or

(b) The contribution is based upon previous work that, to the best
    of my knowledge, is covered under an appropriate open source
    license and I have the right under that license to submit that
    work with modifications, whether created in whole or in part by
    me, under the same open source license (unless I am permitted to
    submit under a different license), as indicated in the file; or

(c) The contribution was provided directly to me by some other
    person who certified (a), (b) or (c) and I have not modified it.

(d) I understand and agree that this project and the contribution
    are public and that a record of the contribution (including all
    personal information I submit with it, including my sign-off) is
    maintained indefinitely and may be redistributed consistent with
    this project or the open source license(s) involved.

After Submitting Your Changes

  • Watch for Continuous Integration (CI) test results
    • You should automatically receive an email with the test results within less than 2 hrs of the submission. If you don’t get the email, then check status on the GitHub pull request.
    • Please notify the development mailing list if you think something doesn’t work.
  • If the tests failed:
    • In general, expect the community to ignore the submission until the tests pass.
    • It is up to you to fix and resubmit.
      • This includes fixing existing unit (“make test”) tests if your changes broke or changed them.
      • It also includes fixing distribution packages for the failing platforms (ie if new libraries are required).
      • Feel free to ask for help on the development list.
    • Go back to the submission process and repeat until the tests pass.
  • If the tests pass:
    • Wait for reviewers. Someone will review your code or be assigned to review your code.
    • Respond to any comments or concerns the reviewer has. Use e-mail or add a comment via github to respond or to let the reviewer know how their comment or concern is addressed.
    • An author must never delete or manually dismiss someone else’s comments or review. (A review may be overridden by agreement in the weekly technical meeting.)
    • Automatically generated comments, e.g., those generated by CI systems, may be deleted by authors and others when such comments are not the most recent results from that automated comment source.
    • After all comments and concerns are addressed, expect your patch to be merged.
  • Watch out for questions on the mailing list. At this time there will be a manual code review and further (longer) tests by various community members.
  • Your submission is done once it is merged to the master branch.

Programming Languages, Tools and Libraries

The core of FRR is written in C (gcc or clang supported) and makes use of GNU compiler extensions. A few non-essential scripts are implemented in Perl and Python. FRR requires the following tools to build distribution packages: automake, autoconf, texinfo, libtool and gawk and various libraries (i.e. libpam and libjson-c).

If your contribution requires a new library or other tool, then please highlight this in your description of the change. Also make sure it’s supported by all FRR platform OSes or provide a way to build without the library (potentially without the new feature) on the other platforms.

Documentation should be written in reStructuredText. Sphinx extensions may be utilized but pure ReST is preferred where possible. See Documentation.

Code Reviews

Code quality is paramount for any large program. Consequently we require reviews of all submitted patches by at least one person other than the submitter before the patch is merged.

Because of the nature of the software, FRR’s maintainer list (i.e. those with commit permissions) tends to contain employees / members of various organizations. In order to prevent conflicts of interest, we use an honor system in which submissions from an individual representing one company should be merged by someone unaffiliated with that company.

Guidelines for code review

  • As a rule of thumb, the depth of the review should be proportional to the scope and / or impact of the patch.
  • Anyone may review a patch.
  • When using GitHub reviews, marking “Approve” on a code review indicates willingness to merge the PR.
  • For individuals with merge rights, marking “Changes requested” is equivalent to a NAK.
  • For a PR you marked with “Changes requested”, please respond to updates in a timely manner to avoid impeding the flow of development.
  • Rejected or obsolete PRs are generally closed by the submitter based on requests and/or agreement captured in a PR comment. The comment may originate with a reviewer or document agreement reached on Slack, the Development mailing list, or the weekly technical meeting.

Coding Practices & Style

Commit messages

Commit messages should be formatted in the same way as Linux kernel commit messages. The format is roughly:

dir: short summary

extended summary

dir should be the top level source directory under which the change was made. For example, a change in bgpd/rfapi would be formatted as:

bgpd: short summary

...

The first line should be no longer than 50 characters. Subsequent lines should be wrapped to 72 characters.

You must also sign off on your commit.

See also

Signing Off

Source File Header

New files must have a copyright header (see License for Contributions above) added to the file. The header should be:

/*
 * Title/Function of file
 * Copyright (C) YEAR  Author’s Name
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 *
 * 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; see the file COPYING; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <zebra.h>

Please copy-paste this header verbatim. In particular:

  • Do not replace “This program” with “FRR”
  • Do not change the address of the FSF

Code Formatting

FRR uses Linux kernel style except where noted below. Code which does not comply with these style guidelines will not be accepted.

The project provides multiple tools to allow you to correctly style your code as painlessly as possible, primarily built around clang-format.

clang-format

In the project root there is a .clang-format configuration file which can be used with the clang-format source formatter tool from the LLVM project. Most of the time, this is the easiest and smartest tool to use. It can be run in a variety of ways. If you point it at a C source file or directory of source files, it will format all of them. In the LLVM source tree there are scripts that allow you to integrate it with git, vim and emacs, and there are third-party plugins for other editors. The git integration is particularly useful; suppose you have some changes in your git index. Then, with the integration installed, you can do the following:

git clang-format

This will format only the changes present in your index. If you have just made a few commits and would like to correctly style only the changes made in those commits, you can use the following syntax:

git clang-format HEAD~X

Where X is one more than the number of commits back from the tip of your branch you would like clang-format to look at (similar to specifying the target for a rebase).

The vim plugin is particularly useful. It allows you to select lines in visual line mode and press a key binding to invoke clang-format on only those lines.

When using clang-format, it is recommended to use the latest version. Each consecutive version generally has better handling of various edge cases. You may notice on occasion that two consecutive runs of clang-format over the same code may result in changes being made on the second run. This is an unfortunate artifact of the tool. Please check with the kernel style guide if in doubt.

One stylistic problem with the FRR codebase is the use of DEFUN macros for defining CLI commands. clang-format will happily format these macro invocations, but the result is often unsightly and difficult to read. Consequently, FRR takes a more relaxed position with how these are formatted. In general you should lean towards using the style exemplified in the section on Command Line Interface. Because clang-format mangles this style, there is a Python script named tools/indent.py that wraps clang-format and handles DEFUN macros as well as some other edge cases specific to FRR. If you are submitting a new file, it is recommended to run that script over the new file, preferably after ensuring that the latest stable release of clang-format is in your PATH.

Documentation on clang-format and its various integrations is maintained on the LLVM website.

https://clang.llvm.org/docs/ClangFormat.html

checkpatch.sh

In the Linux kernel source tree there is a Perl script used to check incoming patches for style errors. FRR uses an adapted version of this script for the same purpose. It can be found at tools/checkpatch.sh. This script takes a git-formatted diff or patch file, applies it to a clean FRR tree, and inspects the result to catch potential style errors. Running this script on your patches before submission is highly recommended. The CI system runs this script as well and will comment on the PR with the results if style errors are found.

It is run like this:

./checkpatch.sh <patch> <tree>

Reports are generated on stderr and the exit code indicates whether issues were found (2, 1) or not (0).

Where <patch> is the path to the diff or patch file and <tree> is the path to your FRR source tree. The tree should be on the branch that you intend to submit the patch against. The script will make a best-effort attempt to save the state of your working tree and index before applying the patch, and to restore it when it is done, but it is still recommended that you have a clean working tree as the script does perform a hard reset on your tree during its run.

The script reports two classes of issues, namely WARNINGs and ERRORs. Please pay attention to both of them. The script will generally report WARNINGs where it cannot be 100% sure that a particular issue is real. In most cases WARNINGs indicate an issue that needs to be fixed. Sometimes the script will report false positives; these will be handled in code review on a case-by-case basis. Since the script only looks at changed lines, occasionally changing one part of a line can cause the script to report a style issue already present on that line that is unrelated to the change. When convenient it is preferred that these be cleaned up inline, but this is not required.

In general, a developer should heed the information reported by checkpatch. However, some flexibility is needed for cases where human judgement yields better clarity than the script. Accordingly, it may be appropriate to ignore some checkpatch.sh warnings per discussion among the submitter(s) and reviewer(s) of a change. Misreporting of errors by the script is possible. When this occurs, the exception should be handled either by patching checkpatch to correct the false error report, or by documenting the exception in this document under Exceptions. If the incorrect report is likely to appear again, a checkpatch update is preferred.

If the script finds one or more WARNINGs it will exit with 1. If it finds one or more ERRORs it will exit with 2.

Please remember that while FRR provides these tools for your convenience, responsibility for properly formatting your code ultimately lies on the shoulders of the submitter. As such, it is recommended to double-check the results of these tools to avoid delays in merging your submission.

In some cases, these tools modify or flag the format in ways that go beyond or even conflict [1] with the canonical documented Linux kernel style. In these cases, the Linux kernel style takes priority; non-canonical issues flagged by the tools are not compulsory but rather are opportunities for discussion among the submitter(s) and reviewer(s) of a change.

Whitespace changes in untouched parts of the code are not acceptable in patches that change actual code. To change/fix formatting issues, please create a separate patch that only does formatting changes and nothing else.

Kernel and BSD styles are documented externally:

For GNU coding style, use indent with the following invocation:

indent -nut -nfc1 file_for_submission.c

Historically, FRR used fixed-width integral types that do not exist in any standard but were defined by most platforms at some point. Officially these types are not guaranteed to exist. Therefore, please use the fixed-width integral types introduced in the C99 standard when contributing new code to FRR. If you need to convert a large amount of code to use the correct types, there is a shell script in tools/convert-fixedwidth.sh that will do the necessary replacements.

Incorrect Correct
u_int8_t uint8_t
u_int16_t uint16_t
u_int32_t uint32_t
u_int64_t uint64_t
u_char uint8_t or unsigned char
u_short unsigned short
u_int unsigned int
u_long unsigned long

Exceptions

FRR project code comes from a variety of sources, so there are some stylistic exceptions in place. They are organized here by branch.

For master

BSD coding style applies to:

  • ldpd/

babeld uses, approximately, the following style:

  • K&R style braces
  • Indents are 4 spaces
  • Function return types are on their own line
For stable/3.0 and stable/2.0

GNU coding style apply to the following parts:

  • lib/
  • zebra/
  • bgpd/
  • ospfd/
  • ospf6d/
  • isisd/
  • ripd/
  • ripngd/
  • vtysh/

BSD coding style applies to:

  • ldpd/

Specific Exceptions

Most of the time checkpatch errors should be corrected. Occasionally as a group maintainers will decide to ignore certain stylistic issues. Usually this is because correcting the issue is not possible without large unrelated code changes. When an exception is made, if it is unlikely to show up again and doesn’t warrant an update to checkpatch, it is documented here.

Issue Ignore Reason
DEFPY_HIDDEN, DEFPY_ATTR: complex macros should be wrapped in parentheses DEF* macros cannot be wrapped in parentheses without updating all usages of the macro, which would be highly disruptive.

Compile-time conditional code

Many users access FRR via binary packages from 3rd party sources; compile-time code puts inclusion/exclusion in the hands of the package maintainer. Please think very carefully before making code conditional at compile time, as it increases regression testing, maintenance burdens, and user confusion. In particular, please avoid gratuitous --enable-… switches to the configure script - in general, code should be of high quality and in working condition, or it shouldn’t be in FRR at all.

When code must be compile-time conditional, try have the compiler make it conditional rather than the C pre-processor so that it will still be checked by the compiler, even if disabled. For example,

if (SOME_SYMBOL)
      frobnicate();

is preferred to

#ifdef SOME_SYMBOL
frobnicate ();
#endif /* SOME_SYMBOL */

Note that the former approach requires ensuring that SOME_SYMBOL will be defined (watch your AC_DEFINEs).

Debug-guards in code

Debugging statements are an important methodology to allow developers to fix issues found in the code after it has been released. The caveat here is that the developer must remember that people will be using the code at scale and in ways that can be unexpected for the original implementor. As such debugs MUST be guarded in such a way that they can be turned off. FRR has the ability to turn on/off debugs from the CLI and it is expected that the developer will use this convention to allow control of their debugs.

Static Analysis and Sanitizers

Clang/LLVM comes with a variety of tools that can be used to help find bugs in FRR.

clang-analyze
This is a static analyzer that scans the source code looking for patterns that are likely to be bugs. The tool is run automatically on pull requests as part of CI and new static analysis warnings will be placed in the CI results. FRR aims for absolutely zero static analysis errors. While the project is not quite there, code that introduces new static analysis errors is very unlikely to be merged.
AddressSanitizer

This is an excellent tool that provides runtime instrumentation for detecting memory errors. As part of CI FRR is built with this instrumentation and run through a series of tests to look for any results. Testing your own code with this tool before submission is encouraged. You can enable it by passing:

--enable-address-sanitizer

to configure.

ThreadSanitizer

Similar to AddressSanitizer, this tool provides runtime instrumentation for detecting data races. If you are working on or around multithreaded code, extensive testing with this instrumtation enabled is highly recommended. You can enable it by passing:

--enable-thread-sanitizer

to configure.

MemorySanitizer

Similar to AddressSanitizer, this tool provides runtime instrumentation for detecting use of uninitialized heap memory. Testing your own code with this tool before submission is encouraged. You can enable it by passing:

--enable-memory-sanitizer

to configure.

All of the above tools are available in the Clang/LLVM toolchain since 3.4. AddressSanitizer and ThreadSanitizer are available in recent versions of GCC, but are no longer actively maintained. MemorySanitizer is not available in GCC.

Additionally, the FRR codebase is regularly scanned with Coverity. Unfortunately Coverity does not have the ability to handle scanning pull requests, but after code is merged it will send an email notifying project members with Coverity access of newly introduced defects.

CLI changes

CLI’s are a complicated ugly beast. Additions or changes to the CLI should use a DEFUN to encapsulate one setting as much as is possible. Additionally as new DEFUN’s are added to the system, documentation should be provided for the new commands.

Backwards Compatibility

As a general principle, changes to CLI and code in the lib/ directory should be made in a backwards compatible fashion. This means that changes that are purely stylistic in nature should be avoided, e.g., renaming an existing macro or library function name without any functional change. When adding new parameters to common functions, it is also good to consider if this too should be done in a backward compatible fashion, e.g., by preserving the old form in addition to adding the new form.

This is not to say that minor or even major functional changes to CLI and common code should be avoided, but rather that the benefit gained from a change should be weighed against the added cost/complexity to existing code. Also, that when making such changes, it is good to preserve compatibility when possible to do so without introducing maintenance overhead/cost. It is also important to keep in mind, existing code includes code that may reside in private repositories (and is yet to be submitted) or code that has yet to be migrated from Quagga to FRR.

That said, compatibility measures can (and should) be removed when either:

  • they become a significant burden, e.g. when data structures change and the compatibility measure would need a complex adaptation layer or becomes flat-out impossible
  • some measure of time (dependent on the specific case) has passed, so that the compatibility grace period is considered expired.

For CLI commands, the deprecation period is 1 year.

In all cases, compatibility pieces should be marked with compiler/preprocessor annotations to print warnings at compile time, pointing to the appropriate update path. A -Werror build should fail if compatibility bits are used. To avoid compilation issues in released code, such compiler/preprocessor annotations must be ignored non-development branches. For example:

#if CONFDATE > 20180403
CPP_NOTICE("Use of <XYZ> is deprecated, please use <ABC>")
#endif

Preferably, the shell script tools/fixup-deprecated.py will be updated along with making non-backwards compatible code changes, or an alternate script should be introduced, to update the code to match the change. When the script is updated, there is no need to preserve the deprecated code. Note that this does not apply to user interface changes, just internal code, macros and libraries.

Miscellaneous

When in doubt, follow the guidelines in the Linux kernel style guide, or ask on the development mailing list / public Slack instance.

Documentation

FRR uses Sphinx+RST as its documentation system. The document you are currently reading was generated by Sphinx from RST source in doc/developer/workflow.rst. The documentation is structured as follows:

Directory Contents
doc/user User documentation; configuration guides; protocol overviews
doc/developer Developer’s documentation; API specs; datastructures; architecture overviews; project management procedure
doc/manpages Source for manpages
doc/figures Images and diagrams
doc/extra Miscellaneous Sphinx extensions, scripts, customizations, etc.

Each of these directories, with the exception of doc/figures and doc/extra, contains a Sphinx-generated Makefile and configuration script conf.py used to set various document parameters. The makefile can be used for a variety of targets; invoke make help in any of these directories for a listing of available output formats. For convenience, there is a top-level Makefile.am that has targets for PDF and HTML documentation for both developer and user documentation, respectively. That makefile is also responsible for building manual pages packed with distribution builds.

Indent and styling should follow existing conventions:

  • 3 spaces for indents under directives
  • Cross references may contain only lowercase alphanumeric characters and hyphens (‘-‘)
  • Lines wrapped to 80 characters where possible

Characters for header levels should follow Python documentation guide:

  • # with overline, for parts
  • * with overline, for chapters
  • =, for sections
  • -, for subsections
  • ^, for subsubsections
  • ", for paragraphs

After you have made your changes, please make sure that you can invoke make latexpdf and make html with no warnings.

The documentation is currently incomplete and needs love. If you find a broken cross-reference, figure, dead hyperlink, style issue or any other nastiness we gladly accept documentation patches.

To build the docs, please ensure you have installed a recent version of Sphinx. If you want to build LaTeX or PDF docs, you will also need a full LaTeX distribution installed.

Code

FRR is a large and complex software project developed by many different people over a long period of time. Without adequate documentation, it can be exceedingly difficult to understand code segments, APIs and other interfaces. In the interest of keeping the project healthy and maintainable, you should make every effort to document your code so that other people can understand what it does without needing to closely read the code itself.

Some specific guidelines that contributors should follow are:

  • Functions exposed in header files should have descriptive comments above their signatures in the header file. At a minimum, a function comment should contain information about the return value, parameters, and a general summary of the function’s purpose. Documentation on parameter values can be omitted if it is (very) obvious what they are used for.

    Function comments must follow the style for multiline comments laid out in the kernel style guide.

    Example:

    /*
     * Determines whether or not a string is cool.
     *
     * text
     *    the string to check for coolness
     *
     * is_clccfc
     *    whether capslock is cruise control for cool
     *
     * Returns:
     *    7 if the text is cool, 0 otherwise
     */
    int check_coolness(const char *text, bool is_clccfc);
    

    Function comments should make it clear what parameters and return values are used for.

  • Static functions should have descriptive comments in the same form as above if what they do is not immediately obvious. Use good engineering judgement when deciding whether a comment is necessary. If you are unsure, document your code.

  • Global variables, static or not, should have a comment describing their use.

  • For new code in lib/, these guidelines are hard requirements.

If you make significant changes to portions of the codebase covered in the Developer’s Manual, add a major subsystem or feature, or gain arcane mastery of some undocumented or poorly documented part of the codebase, please document your work so others can benefit. If you add a major feature or introduce a new API, please document the architecture and API to the best of your abilities in the Developer’s Manual, using good judgement when choosing where to place it.

Finally, if you come across some code that is undocumented and feel like going above and beyond, document it! We absolutely appreciate and accept patches that document previously undocumented code.

User

If you are contributing code that adds significant user-visible functionality please document how to use it in doc/user. Use good judgement when choosing where to place documentation. For example, instructions on how to use your implementation of a new BGP draft should go in the BGP chapter instead of being its own chapter. If you are adding a new protocol daemon, please create a new chapter.

FRR Specific Markup

FRR has some customizations applied to the Sphinx markup that go a long way towards making documentation easier to use, write and maintain.

CLI Commands

When documenting CLI please use a combination of the .. index:: and .. clicmd:: directives. For example, the command show pony would be documented as follows:

.. index:: show pony
.. clicmd:: show pony

   Prints an ASCII pony. Example output:::

           >>\.
          /_  )`.
         /  _)`^)`.   _.---. _
        (_,' \  `^-)""      `.\
              |  | \
              \              / |
             / \  /.___.'\  (\ (_
            < ,"||     \ |`. \`-'
             \\ ()      )|  )/
      hjw    |_>|>     /_] //
               /_]        /_]

When documented this way, CLI commands can be cross referenced with the :clicmd: inline markup like so:

:clicmd:`show pony`

This is very helpful for users who want to quickly remind themselves what a particular command does.

Configuration Snippets

When putting blocks of example configuration please use the .. code-block:: directive and specify frr as the highlighting language, as in the following example. This will tell Sphinx to use a custom Pygments lexer to highlight FRR configuration syntax.

.. code-block:: frr

   !
   ! Example configuration file.
   !
   log file /tmp/log.log
   service integrated-vtysh-config
   !
   ip route 1.2.3.0/24 reject
   ipv6 route de:ea:db:ee:ff::/64 reject
   !

Footnotes

[1]For example, lines over 80 characters are allowed for text strings to make it possible to search the code for them: please see Linux kernel style (breaking long lines and strings) and Issue #1794.