# Submitting Patches

Send changes to Open vSwitch as patches to dev@openvswitch.org. One patch per email. More details are included below.

If you are using Git, then git format-patch takes care of most of the mechanics described below for you.

## Before You Start

Before you send patches at all, make sure that each patch makes sense. In particular:

- A given patch should not break anything, even if later patches fix the problems that it causes. The source tree should still build and work after each patch is applied. (This enables git bisect to work best.)

- A patch should make one logical change. Don’t make multiple, logically unconnected changes to disparate subsystems in a single patch.

- A patch that adds or removes user-visible features should also update the appropriate user documentation or manpages. Consider adding an item to NEWS for nontrivial changes. Check “Feature Deprecation Guidelines” section in this document if you intend to remove user-visible feature.

Testing is also important:

- Test a patch that modifies existing code with `make check` before submission. Refer to the “Unit Tests” in Testing, for more information. We also encourage running the kernel and userspace system tests.

- Consider testing a patch that adds or deletes files with `make distcheck` before submission.

- A patch that modifies Linux kernel code should be at least build-tested on various Linux kernel versions before submission. I suggest versions 3.10 and whatever the current latest release version is at the time.

- A patch that adds a new feature should add appropriate tests for the feature. A bug fix patch should preferably add a test that would fail if the bug recurs.

If you are using GitHub, then you may utilize the GitHub Actions CI build systems. They will run some of the above tests automatically when you push changes to your repository.

## Email Subject

The subject line of your email should be in the following format:

> [PATCH <n>/<m>] <area>: <summary>

Where:

`[PATCH <n>/<m>]`:

  indicates that this is the nth of a series of m patches. It helps reviewers to read patches in the correct order. You may omit this prefix if you are sending only one patch.

`<area>`:

  indicates the area of the Open vSwitch to which the change applies (often the name of a source file or a directory). You may omit it if the change crosses multiple distinct pieces of code.

`<summary>`:

> briefly describes the change. Use the imperative form, e.g. “Force SNAT for multiple gateway routers.” or “Fix daemon exit for bad datapaths or flows.” Try to keep the summary short, about 50 characters wide.

The subject, minus the `[PATCH <n>/<m>]` prefix, becomes the first line of the commit’s change log message.

## Description

The body of the email should start with a more thorough description of the change. This becomes the body of the commit message, following the subject. There is no need to duplicate the summary given in the subject.

Please limit lines in the description to 75 characters in width. That allows the description to format properly even when indented (e.g. by “git log” or in email quotations).

The description should include:

- The rationale for the change.

- Design description and rationale (but this might be better added as code comments).

- Testing that you performed (or testing that should be done but you could not for whatever reason).

- Tags (see below).

There is no need to describe what the patch actually changed, if the reader can see it for himself.

If the patch refers to a commit already in the Open vSwitch repository, please include both the commit number and the subject of the patch, e.g. ‘commit 632d136c (vswitch: Remove restriction on datapath names.)’.

If you, the person sending the patch, did not write the patch yourself, then the very first line of the body should take the form `From: <author name> <author email>`, followed by a blank line. This will automatically cause the named author to be credited with authorship in the repository.

## Tags

The description ends with a series of tags, written one to a line as the last paragraph of the email. Each tag indicates some property of the patch in an easily machine-parseable manner.

Please don’t wrap a tag across multiple lines. If necessary, it’s OK to have a tag extend beyond the customary maximum width of a commit message.

Examples of common tags follow.

`Signed-off-by: Author Name <author.name@email.address...>`

> Informally, this indicates that Author Name is the author or submitter of a patch and has the authority to submit it under the terms of the license. The formal meaning is to agree to the Developer’s Certificate of Origin (see below).

> If the author and submitter are different, each must sign off. If the patch has more than one author, all must sign off.

> Signed-off-by tags should be the last tags in the commit message. If the author (or authors) and submitter are different, the author tags should come first. More generally, occasionally a patch might pass through a chain of submitters, and in such a case the sign-offs should be arranged in chronological order.

>     Signed-off-by: Author Name <author.name@email.address...>
>     Signed-off-by: Submitter Name <submitter.name@email.address...>

`Co-authored-by: Author Name <author.name@email.address...>`

> Git can only record a single person as the author of a given patch. In the rare event that a patch has multiple authors, one must be given the credit in Git and the others must be credited via Co-authored-by: tags. (All co-authors must also sign off.)

`Acked-by: Reviewer Name <reviewer.name@email.address...>`

> Reviewers will often give an `Acked-by:` tag to code of which they approve. It is polite for the submitter to add the tag before posting the next version of the patch or applying the patch to the repository. Quality reviewing is hard work, so this gives a small amount of credit to the reviewer.

> Not all reviewers give `Acked-by:` tags when they provide positive reviews. It’s customary only to add tags from reviewers who actually provide them explicitly.

`Tested-by: Tester Name <reviewer.name@email.address...>`

> When someone tests a patch, it is customary to add a Tested-by: tag indicating that. It’s rare for a tester to actually provide the tag; usually the patch submitter makes the tag himself in response to an email indicating successful testing results.

`Tested-at: <URL>`

> When a test report is publicly available, this provides a way to reference it. Typical <URL>s would be build logs from autobuilders or references to mailing list archives.

> Some autobuilders only retain their logs for a limited amount of time. It is less useful to cite these because they may be dead links for a developer reading the commit message months or years later.

`Reported-by: Reporter Name <reporter.name@email.address...>`

> When a patch fixes a bug reported by some person, please credit the reporter in the commit log in this fashion. Please also add the reporter’s name and email address to the list of people who provided helpful bug reports in the AUTHORS file at the top of the source tree.

> Fairly often, the reporter of a bug also tests the fix. Occasionally one sees a combined “Reported-and-tested-by:” tag used to indicate this. It is also acceptable, and more common, to include both tags separately.

> (If a bug report is received privately, it might not always be appropriate to publicly credit the reporter. If in doubt, please ask the reporter.)

`Requested-by: Requester Name <requester.name@email.address...>`

> When a patch implements a request or a suggestion made by some person, please credit that person in the commit log in this fashion. For a helpful suggestion, please also add the person’s name and email address to the list of people who provided suggestions in the AUTHORS file at the top of the source tree.

> (If a suggestion or a request is received privately, it might not always be appropriate to publicly give credit. If in doubt, please ask.)

`Suggested-by: Suggester Name <suggester.name@email.address...>`

> See `Requested-by:`.

`CC: Person <name@email>`

> This is a way to tag a patch for the attention of a person when no more specific tag is appropriate. One use is to request a review from a particular person. It doesn’t make sense to include the same person in CC and another tag, so e.g. if someone who is CCed later provides an Acked-by, add the Acked-by and remove the CC at the same time.

`Reported-at: <URL>`

> If a patch fixes or is otherwise related to a bug reported in a public bug tracker, please include a reference to the bug in the form of a URL to the specific bug, e.g.:

>     Reported-at: https://bugs.debian.org/743635

> This is also an appropriate way to refer to bug report emails in public email archives, e.g.:

>     Reported-at: https://mail.openvswitch.org/pipermail/ovs-dev/2014-June/284495.html

`Submitted-at: <URL>`

> If a patch was submitted somewhere other than the Open vSwitch development mailing list, such as a GitHub pull request, this header can be used to reference the source.

>     Submitted-at: https://github.com/openvswitch/ovs/pull/92

`VMware-BZ: #1234567`

> If a patch fixes or is otherwise related to a bug reported in a private bug tracker, you may include some tracking ID for the bug for your own reference. Please include some identifier to make the origin clear, e.g. “VMware-BZ” refers to VMware’s internal Bugzilla instance and “ONF-JIRA” refers to the Open Networking Foundation’s JIRA bug tracker.

`ONF-JIRA: EXT-12345`

> See `VMware-BZ:`.

`Bug #1234567.`

> These are obsolete forms of VMware-BZ: that can still be seen in old change log entries. (They are obsolete because they do not tell the reader what bug tracker is referred to.)

`Issue: 1234567`

> See `Bug:`.

`Fixes: 63bc9fb1c69f ("packets: Reorder CS_* flags to remove gap.")`

> If you would like to record which commit introduced a bug being fixed, you may do that with a “Fixes” header. This assists in determining which OVS releases have the bug, so the patch can be applied to all affected versions. The easiest way to generate the header in the proper format is with this git command. This command also CCs the author of the commit being fixed, which makes sense unless the author also made the fix or is already named in another tag:

>     $ git log -1 --pretty=format:"CC: %an <%ae>%nFixes: %h (\"%s\")" \
>       --abbrev=12 COMMIT_REF

`Vulnerability: CVE-2016-2074`

> Specifies that the patch fixes or is otherwise related to a security vulnerability with the given CVE identifier. Other identifiers in public vulnerability databases are also suitable.

> If the vulnerability was reported publicly, then it is also appropriate to cite the URL to the report in a Reported-at tag. Use a Reported-by tag to acknowledge the reporters.

## Developer’s Certificate of Origin

To help track the author of a patch as well as the submission chain, and be clear that the developer has authority to submit a patch for inclusion in Open vSwitch please sign off your work. The sign off certifies 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.

See also http://developercertificate.org/.

## Feature Deprecation Guidelines

Open vSwitch is intended to be user friendly. This means that under normal circumstances we don’t abruptly remove features from OVS that some users might still be using. Otherwise, if we would, then we would possibly break our user setup when they upgrade and would receive bug reports.

Typical process to deprecate a feature in Open vSwitch is to:

1. Mention deprecation of a feature in the NEWS file. Also, mention expected release or absolute time when this feature would be removed from OVS altogether. Don’t use relative time (e.g. “in 6 months”) because that is not clearly interpretable.

2. If Open vSwitch is configured to use deprecated feature it should print a warning message to the log files clearly indicating that feature is deprecated and that use of it should be avoided.

3. If this feature is mentioned in man pages, then add “Deprecated” keyword to it.

Also, if there is alternative feature to the one that is about to be marked as deprecated, then mention it in (a), (b) and (c) as well.

Remember to follow-up and actually remove the feature from OVS codebase once deprecation grace period has expired and users had opportunity to use at least one OVS release that would have informed them about feature deprecation!

## Comments

If you want to include any comments in your email that should not be part of the commit’s change log message, put them after the description, separated by a line that contains just `---`. It may be helpful to include a diffstat here for changes that touch multiple files.

## Patch

The patch should be in the body of the email following the description, separated by a blank line.

Patches should be in `diff -up` format. We recommend that you use Git to produce your patches, in which case you should use the `-M -C` options to `git diff` (or other Git tools) if your patch renames or copies files. Quilt might be useful if you do not want to use Git.

Patches should be inline in the email message. Some email clients corrupt white space or wrap lines in patches. There are hints on how to configure many email clients to avoid this problem on kernel.org. If you cannot convince your email client not to mangle patches, then sending the patch as an attachment is a second choice.

Follow the style used in the code that you are modifying. Coding Style file describes the coding style used in most of Open vSwitch. Use Linux kernel coding style for Linux kernel code.

If your code is non-datapath code, you may use the `utilities/checkpatch.py` utility as a quick check for certain commonly occurring mistakes (improper leading/trailing whitespace, missing signoffs, some improper formatted patch files). For Linux datapath code, it is a good idea to use the Linux script `checkpatch.pl`.

## Example

    From fa29a1c2c17682879e79a21bb0cdd5bbe67fa7c0 Mon Sep 17 00:00:00 2001
    From: Jesse Gross <jesse@nicira.com>
    Date: Thu, 8 Dec 2011 13:17:24 -0800
    Subject: [PATCH] datapath: Alphabetize include/net/ipv6.h compat header.

    Signed-off-by: Jesse Gross <jesse@nicira.com>
    ---
     datapath/linux/Modules.mk |    2 +-
     1 files changed, 1 insertions(+), 1 deletions(-)

    diff --git a/datapath/linux/Modules.mk b/datapath/linux/Modules.mk
    index fdd952e..f6cb88e 100644
    --- a/datapath/linux/Modules.mk
    +++ b/datapath/linux/Modules.mk
    @@ -56,11 +56,11 @@ openvswitch_headers += \
        linux/compat/include/net/dst.h \
        linux/compat/include/net/genetlink.h \
        linux/compat/include/net/ip.h \
    +   linux/compat/include/net/ipv6.h \
        linux/compat/include/net/net_namespace.h \
        linux/compat/include/net/netlink.h \
        linux/compat/include/net/protocol.h \
        linux/compat/include/net/route.h \
    -   linux/compat/include/net/ipv6.h \
        linux/compat/genetlink.inc

     both_modules += brcompat
    --
    1.7.7.3