[quagga-debian.git] / HACKING.md

---
title: Conventions for working on Quagga 
papersize: a4paper
geometry: a4paper,scale=0.82
fontsize: 11pt
toc: true
date: \today
include-before: 
  \large This is a living document describing the processes and guidelines
   for working on Quagga. You *must* read Section
   ["REQUIRED READING"](#sec:required), before contributing to Quagga.

   Suggestions for updates, via the
  [quagga-dev list](http://lists.quagga.net/mailman/listinfo/quagga-dev),
  are welcome. \newpage
...

\newpage

OBJECTIVES {#sec:goals}
==========

The objectives of the Quagga project are to develop and implement high
quality routing protocols and related software, maximising:

* Free software:
    * Quagga is and will remain a copyleft, free software project
    * Some non-core parts may be available under compatible, permissive
      licenses to facilitate code sharing, where contributors agree.
    * The test and integration orchestration infrastructure shall be free
      software, developed similarly to the rest of Quagga. Proprietary
      conformance suites may be among the test tools orchestrated.
* Openness and transparency
    * The business of the project shall be conducted on its public email
      lists, to the greatest extent possible.
    * The design of the software will be governed by open discussion on
      the public email lists.
    * Participants shall endeavour to be transparent about their interests
      in the project, and any associations likely to be relevant.
* Ethical behaviour:
    * The licenses of all copyright holders will be respected, and the
      project will err in their favour where there is reasonable doubt or
      legal advice to that effect.
    * Participants will behave with respect for others, and in a manner that
      builds and maintains the trust needed for productive collaboration.

See also the Section on [CODE OF CONDUCT](#sec:codeconduct).

Governance {#sec:governance}
==========

Quagga is a Sociocracy, as it has been since its earliest days.

Quagga was forked from GNU Zebra by Paul Jakma, who holds the domain name. 
Governance was soon devolved to a collective group, the maintainers,
consisting of those who regularly contributed and reviewed code.  The
details can easily be changed.

You are free to use reason to _persuade_ others to adopt some alternative. 
If, after that, you truly can not abide by what is mutually agreeable, you
are asked to do the honourable thing: take your copy of the code, make your
apologies, and be on your way with good grace.

Those who repeatedly violate the [Code of Conduct](#sec:codeconduct) will be
asked to leave.

Holding of project assets
-------------------------

One or more mature, independent trustees, with technical and free software
experience, will be appointed as the executor(s) for key assets of the
project to ensure continuity, such as the domain name.

Should a corporate vehicle ever be created to hold such assets it __must__:

* Publish up to date accounts on a regular business.
* Generally operate openly and transparently.
* Have control distributed, with a significant degree of control held
  independent of any contributors with business interests in the software.
* Carry out no other business itself that may be seen to conflict or compete
  with the business of others in the community.
* Have all officers disclose all interests that could be
  seen to have a bearing on the project, as far as is reasonable.

It not clear at this time that the overheads and potential liabilities of
such a vehicle would be appropriate for this project.  These principles
should though still be applied, where possible, to any non-corporate body
formed around the project.

CODE OF CONDUCT {#sec:codeconduct}
===============

Participants will treat each other with respect and integrity.  Participants
will build and treasure the trust that is required for parties to
successfully collaborate together on free software.  Particularly when those
parties may have competing interests.  The following principles and
guidelines should be followed to foster that trust:

* Participants should be open about their goals, and their interests.
    - Business associations with other participants should be disclosed,
      so far as is reasonable and where applicable. E.g., if there is voting
      on matters, or in endorsements or objections to contributions.
    - Other associations and interests that may be relevant should be
      disclosed, to the degree necessary to avoid any perception
      by others of conflicts of interests or of deception.
    - Be open about your goals, so as to maximise the common understanding
      and minimise any misunderstandings and disputes.
* Design should be done in the open
    -  Do your design on list, ahead of significant implementation.  Avoid
      "Surprise!" development where possible.
    - Where significant implementation work must be done behind closed
      doors, accept that you may be asked to rework it, potentially from
      scratch once you take it public.
    - Get "buy in" from others ahead of time, to avoid disappointment.
* Interaction 
    - Feedback on design should be constructive, thoughtful and 
      understanding.
    - Avoid personalising matters. Discuss the idea, the code, the abstract
      subject and avoid unnecessary personal pronouns.
    - Avoid language that paints either party into a corner. Leave some room
      for doubt. Ask questions, rather than make assertions, where possible.
* Disputes should be resolved through calm, analytic discussion
    - Separate out as much of the matter under dispute into principles that
      can be agreed on, and into the objective domain (by measurement or
      logic). 
    - Seek ways to resolve any remaining subjective differences by alternate
      paths that can accommodate both sides, e.g., through abstraction or
      modularisation.
    - Aim for Win-Win.
* Respect others
    - Avoid passive-aggressive behaviours. E.g., tit-for-tat
      non-constructive behaviour. Be explicit.
    - It is acceptable for management to allocate resources on development
      according to their need.  It is not acceptable to try use external,
      management intervention to over-turn positions held by participants.

REQUIRED READING {#sec:required}
================

Note well: By proposing a change to Quagga, by whatever means, you are
implicitly agreeing:
                                                                              
-   To licence your contribution according to the licence of any files in
    Quagga being modified, _and_ according to the COPYING file in the
    top-level directory of Quagga, other than where the contribution
    explicitly and clearly indicates otherwise.

-   That it is your responsibility to ensure you hold whatever rights are
    required to be able to contribute your changes under the licenses of the
    files in Quagga being modified, and the top-level COPYING file.
                                                                              
-   That it is your responsibility to give with the contribution a full
    account of all interests held and claims in the contribution; such as
    through copyright, trademark and patent laws or otherwise; that are known
    to you or your associates (e.g.  your employer).

Before contributing to Quagga, you *must*  also read 
[Section COMMIT MESSAGES](#sec:commit-messages).  

You _should_ ideally read the entire document, as it contains useful
information on the community norms and how to implement them.

Please note that authorship and any relevant other rights information should
be _explicitly_ stated with the contribution.  A "Signed-off-by" line is
_not_ sufficient.  The "Signed-off-by" line is not used by the Quagga
project.

You may document applicable copyright claims to files being modified or
added by your contribution.  For new files, the standard way is to add a
string in the following format near the beginning of the file:

    Copyright (C) <Year> <name of person/entity>[, optional contact details]

When adding copyright claims for modifications to an existing file, please
preface the claim with "Portions: " on a line before it and indent the
"Copyright ..." string. If such a case already exists, add your indented
claim immediately after. E.g.:

    Portions:
      Copyright (C) <Year> <Entity A> ....
      Copyright (C) <Year> <Your details> [optional brief change description]


GUIDELINES FOR HACKING ON QUAGGA {#sec:guidelines}
================================

GNU coding standards apply.  Indentation follows the result of
invoking GNU indent (as of 2.2.8a) with the -–nut argument.

Originally, tabs were used instead of spaces, with tabs are every 8 columns. 
However, tab’s interoperability issues mean space characters are now preferred for
new changes. We generally only clean up whitespace when code is unmaintainable
due to whitespace issues, to minimise merging conflicts.

Be particularly careful not to break platforms/protocols that you
cannot test.

Parsers or packet-writers of data from untrusted parties, particularly
remote ones, *MUST* use the lib/stream bounded-buffer abstraction, and use
its checked getters and putters.  Twiddling of pointers based on contents of
untrusted data is _strongly_ discouraged - any such code is not acceptable,
unless there are very good reasons (e.g.  compatibility with external or old
code that is not easily rewritten).

New code should have good comments, which explain why the code is correct.
Changes to existing code should in many cases upgrade the comments when
necessary for a reviewer to conclude that the change has no unintended
consequences.

Each file in the Git repository should have a git format-placeholder (like
an RCS Id keyword), somewhere very near the top, commented out appropriately
for the file type. The placeholder used for Quagga (replacing \<dollar\>
with \$) is:

`$QuaggaId: <dollar>Format:%an, %ai, %h<dollar> $`

See line 2 of HACKING.tex, the source for this document, for an example.

This placeholder string will be expanded out by the ‘git archive’ commands,
which is used to generate the tar archives for snapshots and releases.

Please document fully the proper use of a new function in the header file
in which it is declared.  And please consult existing headers for
documentation on how to use existing functions.  In particular, please consult
these header files:

<span>lib/log.h</span> logging levels and usage guidance

<span>[more to be added]</span>

If changing an exported interface, please try to deprecate the interface in
an orderly manner. If at all possible, try to retain the old deprecated
interface as is, or functionally equivalent. Make a note of when the
interface was deprecated and guard the deprecated interface definitions in
the header file, i.e.:

    /* Deprecated: 20050406 */
    #if !defined(QUAGGA_NO_DEPRECATED_INTERFACES)
    #warning "Using deprecated <libname> (interface(s)|function(s))"
    ...
    #endif /* QUAGGA_NO_DEPRECATED_INTERFACES */

This is to ensure that the core Quagga sources do not use the deprecated
interfaces (you should update Quagga sources to use new interfaces, if
applicable), while allowing external sources to continue to build. 
Deprecated interfaces should be excised in the next unstable cycle.

Note: If you wish, you can test for GCC and use a function
marked with the ’deprecated’ attribute.  However, you must provide the
warning for other compilers.

If changing or removing a command definition, *ensure* that you
properly deprecate it - use the \_DEPRECATED form of the appropriate DEFUN
macro. This is *critical*.  Even if the command can no longer
function, you *MUST* still implement it as a do-nothing stub.

Failure to follow this causes grief for systems administrators, as an
upgrade may cause daemons to fail to start because of unrecognised commands. 
Deprecated commands should be excised in the next unstable cycle.  A list of
deprecated commands should be collated for each release.

See also [Section SHARED LIBRARY VERSIONING](#sec:dll-versioning) below.

YOUR FIRST CONTRIBUTIONS
========================

Routing protocols can be very complex sometimes. Then, working with an
Opensource community can be complex too, but usually friendly with
anyone who is ready to be willing to do it properly.

-   First, start doing simple tasks. Quagga’s patchwork is a good place
    to start with. Pickup some patches, apply them on your git trie,
    review them and send your ack’t or review comments. Then, a
    maintainer will apply the patch if ack’t or the author will have to
    provide a new update. It help a lot to drain the patchwork queues.
    See <http://patchwork.quagga.net/project/quagga/list/>

-   The more you’ll review patches from patchwork, the more the Quagga’s
    maintainers will be willing to consider some patches you will be
    sending.

-   start using git clone, pwclient
    <http://patchwork.quagga.net/help/pwclient/>

        $ pwclient list -s new
        ID    State        Name
        --    -----        ----
        179   New          [quagga-dev,6648] Re: quagga on FreeBSD 4.11 (gcc-2.95)
        181   New          [quagga-dev,6660] proxy-arp patch
        [...]

        $ pwclient git-am 1046

HANDY GUIDELINES FOR MAINTAINERS
================================

Get your cloned trie:

      git clone vjardin@git.sv.gnu.org:/srv/git/quagga.git

Apply some ack’t patches:

      pwclient git-am 1046
        Applying patch #1046 using 'git am'
        Description: [quagga-dev,11595] zebra: route_unlock_node is missing in "show ip[v6] route <prefix>" commands
        Applying: zebra: route_unlock_node is missing in "show ip[v6] route <prefix>" commands

Run a quick review. If the ack’t was not done properly, you know who you have
to blame.

Push the patches:

      git push

Set the patch to accepted on patchwork

      pwclient update -s Accepted 1046

COMPILE-TIME CONDITIONAL CODE
=============================

Please think very carefully before making code conditional at compile time,
as it increases maintenance burdens and user confusion. In particular,
please avoid gratuitous -–enable-… switches to the configure script -
typically code should be good enough to be in Quagga, or it shouldn’t be
there 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. I.e.  this:

        if (SOME_SYMBOL)
          frobnicate();

rather than:

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

Note that the former approach requires ensuring that SOME\_SYMBOL will
be defined (watch your AC\_DEFINEs).

COMMIT MESSAGES {#sec:commit-messages}
======================================

The commit message requirements are:

-   The message *MUST* provide a suitable one-line summary followed by a
    blank line as the very first line of the message, in the form:

    `topic: high-level, one line summary`

    Where topic would tend to be name of a subdirectory, and/or daemon, unless
    there’s a more suitable topic (e.g. ’build’). This topic is used to
    organise change summaries in release announcements.

-   It should have a suitable “body”, which tries to address the
    following areas, so as to help reviewers and future browsers of the
    code-base understand why the change is correct (note also the code
    comment requirements):

    -   The motivation for the change (does it fix a bug, if so which?
        add a feature?)

    -   The general approach taken, and trade-offs versus any other
        approaches.

    -   Any testing undertaken or other information affecting the confidence
        that can be had in the change.

    -   Information to allow reviewers to be able to tell which specific
        changes to the code are intended (and hence be able to spot any accidental
        unintended changes).

-   The commit message *must* give details of all the authors of the change,
    beyond the person listed in the Author field.  Any and all affiliations
    which may have a bearing on copyright in any way should be clearly
    stated, unless those affiliations are already obvious from other
    details, e.g.  from the email address.  This would cover employment and
    contracting obligations (give details).

    Note: Do not rely on "Signed-off-by" for this, be explicit.
    
-   If the change introduces a new dependency on any code or other
    copyrighted material, please explicitly note this.  Give details of what
    that external material is, the copyright licence the material may be
    used under, and the nature of the dependency.

The one-line summary must be limited to 54 characters, and all other
lines to 72 characters.

Commit message bodies in the Quagga project have typically taken the
following form:

-   An optional introduction, describing the change generally.

-   A short description of each specific change made, preferably:

    -   file by file

        -   function by function (use of “ditto”, or globs is allowed)

Contributors are strongly encouraged to follow this form.

This itemised commit messages allows reviewers to have confidence that the
author has self-reviewed every line of the patch, as well as providing
reviewers a clear index of which changes are intended, and descriptions for
them (C-to-english descriptions are not desirable - some discretion is
useful).  For short patches, a per-function/file break-down may be
redundant.  For longer patches, such a break-down may be essential.  A
contrived example (where the general discussion is obviously somewhat
redundant, given the one-line summary):

>     zebra: Enhance frob FSM to detect loss of frob
>
>     Add a new DOWN state to the frob state machine to allow the barinator to
>     detect loss of frob.
>
>     * frob.h: (struct frob) Add DOWN state flag.
>     * frob.c: (frob_change) set/clear DOWN appropriately on state change.
>     * bar.c: (barinate) Check frob for DOWN state.

Please have a look at the git commit logs to get a feel for what the norms
are.

Note that the commit message format follows git norms, so that “git log
–oneline” will have useful output.

HACKING THE BUILD SYSTEM
========================

If you change or add to the build system (configure.ac, any Makefile.am,
etc.), please heck that the following things still work:

-   make dist

-   resulting dist tarball builds

-   out-of-tree builds

This can be achieved by running 'make distcheck'

The quagga.net site relies on make dist to work to generate snapshots. It
must work. Common problems are to forget to have some additional file
included in the dist, or to have a make rule refer to a source file without
using the srcdir variable.

RELEASE PROCEDURE
=================

To make a release:

-   Edit configure.ac, bump the version and commit the change with
    a "release: <version" subject.

The 'release.sh' script should then be used. It should be run with 2
arguments, the release tag for the release to be carried, and the tag of the
previous release, e.g.:

        release.sh quagga-1.1.1 quagga-1.1.0

The 'release.sh' will carry out these steps for you:

-   Tag the appropriate commit with a release tag (follow existing
    conventions), with:

        git tag -u <release signing key id> <quagga-release-tag>

-   Create a fresh tar archive of the quagga.net repository, and do a
    test build.  Use git archive to ensure it consists of files in the
    repository, and to carry out the keyword expansions.  Do NOT do this in
    a subdirectory of the Quagga sources, autoconf will think it’s a
    sub-package and fail to include neccessary files.

            git archive ... <quagga-release-tag> | tar xC ..

            autoreconf -i && ./configure && make && make dist-gzip

-   Similarly test the dist tarball produced. This is the tarball to be
    released. This is important.

-   Sign the dist tarball to be released
            
            gpg -u 54CD2E60 -a --detach-sign quagga-0.99.99.99.tar

The 'release.sh' script, if finishes successfully,  will print out
instructions on the files it has created and the details on remaining steps
to be carried out to complete the release. Which roughly are:

-   Upload the release tarball, its PGP signature, and the full changelog
    to the public release area on Savannah

-   Add the version number on https://bugzilla.quagga.net/, under
    Administration, Products, “Quagga”, Edit versions, Add a version.

-   Post a news entry on Savannah

-   Send a mail to quagga-dev and quagga-users

If any errors occur, move tags as needed and start over again with the
release.sh script.  Do not try to append stuff to tarballs, as this has
produced non-standards-conforming tarballs in the past.

[TODO: collation of a list of deprecated commands. Possibly can be
scripted to extract from vtysh/vtysh\_cmd.c]

TOOL VERSIONS
=============

Require versions of support tools are listed in INSTALL.quagga.txt.
Required versions should only be done with due deliberation, as it can
cause environments to no longer be able to compile quagga.

SHARED LIBRARY VERSIONING {#sec:dll-versioning}
=========================

[this section is at the moment just gdt’s opinion]

Quagga builds several shared libaries (lib/libzebra, ospfd/libospf,
ospfclient/libsopfapiclient).  These may be used by external programs,
e.g. a new routing protocol that works with the zebra daemon, or
ospfapi clients.  The libtool info pages (node Versioning) explain
when major and minor version numbers should be changed.  These values
are set in Makefile.am near the definition of the library.  If you
make a change that requires changing the shared library version,
please update Makefile.am.

libospf exports far more than it should, and is needed by ospfapi
clients.  Only bump libospf for changes to functions for which it is
reasonable for a user of ospfapi to call, and please err on the side
of not bumping.

There is no support intended for installing part of zebra.  The core
library libzebra and the included daemons should always be built and
installed together.

GIT COMMIT SUBMISSION {#sec:git-submission}
=====================

The preferred method for submitting changes is to provide git commits via a
publicly-accessible git repository, which the maintainers can easily pull.

The commits should be in a branch based off the Quagga.net master - a
“feature branch”.  Ideally there should be no commits to this branch other
than those in master, and those intended to be submitted.  However, merge
commits to this branch from the Quagga master are permitted, though strongly
discouraged - use another (potentially local and throw-away) branch to test
merge with the latest Quagga master.

Recommended practice is to keep different logical sets of changes on
separate branches - “topic” or “feature” branches.  This allows you to still
merge them together to one branch (potentially local and/or “throw-away”)
for testing or use, while retaining smaller, independent branches that are
easier to merge.

All content guidelines in [Section PATCH SUBMISSION](#sec:patch-submission)
apply.

PATCH SUBMISSION {#sec:patch-submission}
================

-   For complex changes, contributors are strongly encouraged to first
    start a design discussion on the quagga-dev list *before* starting
    any coding.

-   Send a clean diff against the ’master’ branch of the quagga.git
    repository, in unified diff format, preferably with the ’-p’
    argument to show C function affected by any chunk, and with the -w
    and -b arguments to minimise changes. E.g:

    git diff -up mybranch..remotes/quagga.net/master

    It is preferable to use git format-patch, and even more preferred to
    publish a git repository (see 
    [Section GIT COMMIT SUBMISSION](#sec:git-submission)).

    If not using git format-patch, Include the commit message in the
    email.

-   After a commit, code should have comments explaining to the reviewer
    why it is correct, without reference to history. The commit message
    should explain why the change is correct.

-   Include NEWS entries as appropriate.

-   Include only one semantic change or group of changes per patch.

-   Do not make gratuitous changes to whitespace. See the w and b
    arguments to diff.

-   Changes should be arranged so that the least controversial and most
    trivial are first, and the most complex or more controversial are
    last. This will maximise how many the Quagga maintainers can merge,
    even if some other commits need further work.

-   Providing a unit-test is strongly encouraged. Doing so will make it
    much easier for maintainers to have confidence that they will be
    able to support your change.

-   New code should be arranged so that it easy to verify and test. E.g.
    stateful logic should be separated out from functional logic as much
    as possible: wherever possible, move complex logic out to smaller
    helper functions which access no state other than their arguments.

-   State on which platforms and with what daemons the patch has been
    tested. Understand that if the set of testing locations is small,
    and the patch might have unforeseen or hard to fix consequences that
    there may be a call for testers on quagga-dev, and that the patch
    may be blocked until test results appear.

    If there are no users for a platform on quagga-dev who are able and
    willing to verify -current occasionally, that platform may be
    dropped from the “should be checked” list.

PATCH APPLICATION
=================

-   Only apply patches that meet the submission guidelines.

-   If the patch might break something, issue a call for testing on the
    mailing-list.

-   Give an appropriate commit message (see above), and use the –author
    argument to git-commit, if required, to ensure proper attribution
    (you should still be listed as committer)

-   Immediately after commiting, double-check (with git-log and/or
    gitk). If there’s a small mistake you can easily fix it with ‘git
    commit –amend ..’

-   When merging a branch, always use an explicit merge commit. Giving
    –no-ff ensures a merge commit is created which documents “this human
    decided to merge this branch at this time”.

STABLE PLATFORMS AND DAEMONS
============================

The list of platforms that should be tested follow.  This is a list
derived from what quagga is thought to run on and for which
maintainers can test or there are people on quagga-dev who are able
and willing to verify that -current does or does not work correctly.

-   BSD (Free, Net or Open, any platform)

-   GNU/Linux (any distribution, i386)

-   Solaris (strict alignment, any platform)

-   future: NetBSD/sparc64

The list of daemons that are thought to be stable and that should be
tested are:

-   zebra

-   bgpd

-   ripd

-   ospfd

-   ripngd

Daemons which are in a testing phase are

-   ospf6d

-   isisd

-   watchquagga

USEFUL URLs
===========

*   The project homepage is at:

    <https://www.quagga.net>


*   Bugs can be reported via Bugzilla at:

    <https://bugzilla.quagga.net>

*   Buildbot runs CI tests, and is at:

    <https://buildbot.quagga.net>

    It tests commits and  jobs submitted on local changes via
    'buildbot try ...' for developers.

*   Patchwork tracks any patches emailed to the quagga-dev list, and is at:

    <https://patchwork.quagga.net/project/quagga/list/>


BUILDBOT
========

The buildbot client can be used to test changes before committing, with
"buildbot try".

-   Ask for a buildbot account

-   Install the buildbot client

-   Configure it, e.g.:

    ~~~~~
    $ cat ~/.buildbot/options
    try_master = 'radia.quagga.net:8031'
    try_username = 'paul'
    try_password = 'password123'
    try_vc = 'git'
    try_branch = 'master'
    try_wait = True
    $ buildbot try -c pb --get-builder-names
    using 'pb' connect method
    The following builders are available for the try scheduler: 
    build-fedora-24
    ...
    ~~~~~

-   You can then submit your local changes to try build:

    ~~~~
    $ buildbot try -c pb
    ~~~~

    or use the -b argument to limit to a specific builder (recommended).

    ~~~~~
    $ buildbot try -c pb -b build-distcheck
    ~~~~~

-  To test a series of locally committed change use git diff:

    ~~~~
    git diff <base rev>.. | buildbot try -c pb --vc git \
         -b build-centos-7  --branch=volatile/next --diff=- -p 1
    ~~~~