Contributing code

The best way to contribute code is to submit a high-quality pull request against the master branch of the official repository on GitHub. To speed up code review and improve your code acceptance chances, please adhere to SquidCodingGuidelines and follow the MergeProcedure.

ProgrammingGuide provides a broad overview of Squid architecture and details some of Squid modules. It also discusses manual page writing.

Auto-generated code documentation offers some information on the Squid internals with links to the latest version of the code.

Finding things to do:

  • Bugzilla contains bugs and feature requests.

  • RoadMap lists the feature wishes and plans for future releases.

  • RoadMap/Tasks itemizes general cleanup tasks that need to be done. These can be good introductory tasks.

  • HTTP/1.1 compliance violations need to be addressed.

  • git grep XXX

  • git grep TODO

  • Other developers are often able to provide projects for anyone just wanting to contribute.

Discussing code

Most development discussions happen on the developer mailing list. Please note that all messages must be sent in plain-text only (no HTML email).


We run constant integration testing with a BuildFarm.

It is possible to rely on the images we use for it to test code changes against different Linux distributions and compiler versions. We publish these images to the Docker Hub. They are named squidcache/buildfarm-`uname -m`-<os name>

Assuming you have access to a Docker environment, the easiest way to test a local checkout on it is to run the command:

OS=centos-7 docker run -ti --rm -v$PWD:$PWD -w$PWD -u1000 ./ squidcache/buildfarm-`uname -m`-$OS --verbose --use-config-cache --cleanup

It may leave behind some files owned by UID 1000; sorry it can't be avoided

Detecting build errors early

It is always better to find bugs before submitting a PR for review. Since Squid has such a large number of build permutations that can interact to change build dependencies and outcomes the a script is provided in the repository to check that your code contribution will at least compile successfully. This is the same script which will be run by the CI system in a wider range of OS systems to prevent regressions.

In a checkout of the Squid sources branch you are proposing to submit for PR, run: ` ./ && ./ `

The default stdout display just lists the ERROR and FAIL messages produced during build. Not all of these are problems (eg stats indicating 0 failures), a series of logs with full build output are provided as well. See the end of the log for overall build result if you have any doubts about the success/failure status.

The command line option --keep-going is provided to allow as many error as possible to be found on one script execution. It builds with make -k and tries all build permutations instead of exiting on the first compile failure.

The command line option --verbose is provided to allow full compile output to stdout instead of only to logs. The logs are still produced.

Other options are available for specific build situations. See the script for details or ask on squid-dev mailing list.

Replication of CI BuildFarm failures

On any linux system with docker installed, to reproduce a build you can check out squid sources on a fresh directory, then run:

` OS_VERSION=fedora-32 docker run -ti --rm -u jenkins -v $PWD:$PWD -w $PWD squidcache/buildfarm:uname -m-$OS_VERSION /bin/bash -l `

  • /!\ Replace OS_VERSION with the OS version of the CI system node which is failing (eg, fedora-rawhide, debian-unstable)

This will drop you in the container, ready to try things out.

Getting sources

There are several ways to get Squid sources. The method you select determines whether the sources come bootstrapped or can be easily updated as the official code changes.

Raw sources via GitHub

The official Squid source code repository is on GitHub. see GitHints for common actions you may need to perform with the git VCS.

  • /!\ When working from this repository the script is required to prepare ./configure and related magic. See #Required_Build_Tools for the required bootstrapping and building tools.

Bootstrapped source tarballs via HTTP

The latest sources are available at address with a series of previous daily snapshots of the code for testing regressions and other special circumstances.

  • {i} The daily tarballs displayed are listed by date created and the repository revision ID included in that tarball. Gaps are expected in the list when there were no new revisions committed that day, or when the revision failed to compile on our tarball creation machine.

    /!\ Daily tarballs contain the fully bootstrapped tool chain ready to build. But be aware that some changes may appear with incomplete or missing documentation.

As a more lightweight alternative you can use rsync to fetch the latest tarball content.

Bootstrapped sources via rsync

As a more lightweight alternative to the tarballs you can use rsync; the latest sources are available at address rsync://<version>

The rsync source mirrors the latest published sources tarball.

/!\ The rsync sources contain the fully bootstrapped tool chain ready to build. But be aware that some changes may appear with incomplete or missing documentation.

To use this feature you may use

$ rsync rsync://
(sample output)
drwxr-xr-x         512 2011/03/20 19:14:28 .
drwxr-xr-x        1024 2009/09/17 14:13:26 squid-2.6
drwxr-xr-x        1024 2011/03/20 19:14:06 squid-2.7
drwxr-xr-x        1024 2010/07/02 13:10:53 squid-2
drwxr-xr-x        1024 2010/07/02 13:17:48 squid-3.0
drwxr-xr-x        1024 2011/03/20 19:14:21 squid-3.1
drwxr-xr-x        1024 2011/03/20 19:14:26 squid-3.2
drwxr-xr-x        1024 2011/03/20 19:14:26 squid-3.3
drwxr-xr-x        1024 2011/03/20 19:14:26 squid-3.4
drwxr-xr-x        1024 2011/03/20 19:14:26 squid-3.5
drwxr-xr-x        1024 2011/03/20 19:14:13 squid-4

After you've selected the version you wish to download you can:

rsync -avz rsync://<version> .

Required Build Tools

  • autoconf 2.64 or later
  • automake 1.10 or later
  • libtool 2.6 or later
  • libltdl-dev
  • awk
  • ed
  • CppUnit for unit testing.

Depending on what features you wish to develop there may be other library and tool requirements.

Building tarballs for distribution requires these additional tools:

  • autoconf-archive
  • tar
  • gzip
  • bzip2
  • xz
  • perl

When working from the repository code the script is required initially to run a number of autotools to prepare ./configure and related magic. This needs repeating after any changes to the or scripts, including changes received from the repository updates. Common problems are discussed in ProgrammingGuide/Bootstrap.


ReleaseProcess describes the process and criteria used by the Squid Developers when making new Squid releases from the accepted changes.

WhoWeAre explains who the people working on the Squid project are.

During the life of the Squid project, a number of papers have been published.

Code Sprints are informal gatherings of Squid developers with a focus on developing urgently needed features or fixing major bugs. You can find links to related documents in MeetUps.

DeveloperResources (last edited 2021-07-04 22:29:47 by FrancescoChemolli)