How to submit patches

Setting up working enviroment

Although criu could be run as non-root (see Security), development is better to be done as root. For example, some tests require root. So, it would be a good idea to set up some recent Linux distro on a virtual machine.

Obtaining the source code

The CRIU sources are tracked by Git SCM at https://github.com/xemul/criu repository. You either could download packed sources or use git tool itself.

For example to clone CRIU one need to type

       git clone https://github.com/xemul/criu

Picking the proper branch

Please note, that the development goes on the criu-dev branch. The master one is for stable releases.

Compiling the source code

Note: Dependencies are listed in the Installation article.

Run:

       cd criu
       make

This will produce ./criu executable. As you are going to work with sources, it would come in handy to get tags by running:

       make tags

Note: It requires ctags to be installed.

Changing the source code

When you change the source code keep in mind - we prefer tabs and indentations to be 8 characters width. Consider reading Linux kernel coding style.

Other "rules" could be learned from the source code - just make your code to look similar.

Producing a patch

There are at least two ways to make it right.

1) git format-patch

You might need to read documentation on Git SCM how to prepare patch for mail submission. Take a look on http://book.git-scm.com/ and/or http://git-scm.com/documentation for details. It should not be hard at all.

2) Use "diff -up"

Use diff -up or diff -uprN to create patches.

Signing your work

To improve tracking of who did what we've introduced a "sign-off" procedure on patches that are being emailed around.

The sign-off is a simple line at the end of the explanation for the patch, which certifies that you wrote it or otherwise have the right to pass it on as a open-source patch. The rules are pretty simple: if you can certify the below:

   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.

then you just add a line saying

       Signed-off-by: Random J Developer <random at developer.example.org>

using your real name (please, no pseudonyms or anonymous contributions if it possible).

Hint: you can use git commit -s to add Signed-off-by line to your commit message. To append such line to a commit you already made, use git commit --amend -s.

An example of patch message

From: Random J Developer <random at developer.example.org>
Subject: [PATCH] Short patch description

Long patch description (could be skipped if patch
is trivial enough)

Signed-off-by: Random J Developer <random at developer.example.org>
---
Patch body here

Checking patches for errors

Basic style error checking is provided by scripts/checkpatch.pl script from linux kernel source tree. You might have headers or complete sources of linux kernel at /usr/src/. Run

        checkpatch.pl my_patch.patch (consider --no-tree option for headers-only)

It will produce detailed report on style problems in your patch. Make sure to fix all _errors_(some warnings may be ignored).

To check whether your patches don't harm anything run

        make test

It will launch ZDTM_Test_Suite. Check for error messages produced by it. You may also want to run other tests(rpc, libcriu, security etc) from test/ dir.

In addition, you can enable travis-ci for you github repo, which will check compilation on all platforms and execute a big part of tests.

Mailing patches

The patches should be sent to CRIU development mailing list which is located at https://openvz.org/mailman/listinfo/criu

Please make sure the email client you're using doesn't screw your patch (line wrapping and so on).

Wait for response

Be patient. Most CRIU developers are pretty busy people so if there is no immediate response on your patch - don't be surprised, sometimes a patch may fly around a week(s) before it get reviewed. But definitely the patches will not go to /dev/null.