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332 lines
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.. SPDX-License-Identifier: GPL-2.0
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.. _netdev-FAQ:
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==========
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netdev FAQ
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==========
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tl;dr
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-----
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- designate your patch to a tree - ``[PATCH net]`` or ``[PATCH net-next]``
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- for fixes the ``Fixes:`` tag is required, regardless of the tree
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- don't post large series (> 15 patches), break them up
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- don't repost your patches within one 24h period
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- reverse xmas tree
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What is netdev?
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---------------
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It is a mailing list for all network-related Linux stuff. This
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includes anything found under net/ (i.e. core code like IPv6) and
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drivers/net (i.e. hardware specific drivers) in the Linux source tree.
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Note that some subsystems (e.g. wireless drivers) which have a high
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volume of traffic have their own specific mailing lists.
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The netdev list is managed (like many other Linux mailing lists) through
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VGER (http://vger.kernel.org/) with archives available at
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https://lore.kernel.org/netdev/
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Aside from subsystems like those mentioned above, all network-related
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Linux development (i.e. RFC, review, comments, etc.) takes place on
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netdev.
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How do the changes posted to netdev make their way into Linux?
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--------------------------------------------------------------
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There are always two trees (git repositories) in play. Both are
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driven by David Miller, the main network maintainer. There is the
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``net`` tree, and the ``net-next`` tree. As you can probably guess from
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the names, the ``net`` tree is for fixes to existing code already in the
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mainline tree from Linus, and ``net-next`` is where the new code goes
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for the future release. You can find the trees here:
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- https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git
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- https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git
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How do I indicate which tree (net vs. net-next) my patch should be in?
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----------------------------------------------------------------------
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To help maintainers and CI bots you should explicitly mark which tree
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your patch is targeting. Assuming that you use git, use the prefix
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flag::
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git format-patch --subject-prefix='PATCH net-next' start..finish
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Use ``net`` instead of ``net-next`` (always lower case) in the above for
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bug-fix ``net`` content.
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How often do changes from these trees make it to the mainline Linus tree?
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-------------------------------------------------------------------------
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To understand this, you need to know a bit of background information on
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the cadence of Linux development. Each new release starts off with a
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two week "merge window" where the main maintainers feed their new stuff
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to Linus for merging into the mainline tree. After the two weeks, the
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merge window is closed, and it is called/tagged ``-rc1``. No new
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features get mainlined after this -- only fixes to the rc1 content are
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expected. After roughly a week of collecting fixes to the rc1 content,
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rc2 is released. This repeats on a roughly weekly basis until rc7
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(typically; sometimes rc6 if things are quiet, or rc8 if things are in a
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state of churn), and a week after the last vX.Y-rcN was done, the
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official vX.Y is released.
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Relating that to netdev: At the beginning of the 2-week merge window,
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the ``net-next`` tree will be closed - no new changes/features. The
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accumulated new content of the past ~10 weeks will be passed onto
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mainline/Linus via a pull request for vX.Y -- at the same time, the
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``net`` tree will start accumulating fixes for this pulled content
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relating to vX.Y
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An announcement indicating when ``net-next`` has been closed is usually
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sent to netdev, but knowing the above, you can predict that in advance.
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.. warning::
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Do not send new ``net-next`` content to netdev during the
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period during which ``net-next`` tree is closed.
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RFC patches sent for review only are obviously welcome at any time
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(use ``--subject-prefix='RFC net-next'`` with ``git format-patch``).
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Shortly after the two weeks have passed (and vX.Y-rc1 is released), the
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tree for ``net-next`` reopens to collect content for the next (vX.Y+1)
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release.
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If you aren't subscribed to netdev and/or are simply unsure if
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``net-next`` has re-opened yet, simply check the ``net-next`` git
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repository link above for any new networking-related commits. You may
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also check the following website for the current status:
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http://vger.kernel.org/~davem/net-next.html
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The ``net`` tree continues to collect fixes for the vX.Y content, and is
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fed back to Linus at regular (~weekly) intervals. Meaning that the
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focus for ``net`` is on stabilization and bug fixes.
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Finally, the vX.Y gets released, and the whole cycle starts over.
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So where are we now in this cycle?
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----------------------------------
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Load the mainline (Linus) page here:
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https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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and note the top of the "tags" section. If it is rc1, it is early in
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the dev cycle. If it was tagged rc7 a week ago, then a release is
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probably imminent. If the most recent tag is a final release tag
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(without an ``-rcN`` suffix) - we are most likely in a merge window
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and ``net-next`` is closed.
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How can I tell the status of a patch I've sent?
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-----------------------------------------------
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Start by looking at the main patchworks queue for netdev:
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https://patchwork.kernel.org/project/netdevbpf/list/
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The "State" field will tell you exactly where things are at with your
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patch. Patches are indexed by the ``Message-ID`` header of the emails
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which carried them so if you have trouble finding your patch append
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the value of ``Message-ID`` to the URL above.
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How long before my patch is accepted?
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-------------------------------------
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Generally speaking, the patches get triaged quickly (in less than
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48h). But be patient, if your patch is active in patchwork (i.e. it's
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listed on the project's patch list) the chances it was missed are close to zero.
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Asking the maintainer for status updates on your
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patch is a good way to ensure your patch is ignored or pushed to the
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bottom of the priority list.
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Should I directly update patchwork state of my own patches?
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-----------------------------------------------------------
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It may be tempting to help the maintainers and update the state of your
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own patches when you post a new version or spot a bug. Please do not do that.
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Interfering with the patch status on patchwork will only cause confusion. Leave
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it to the maintainer to figure out what is the most recent and current
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version that should be applied. If there is any doubt, the maintainer
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will reply and ask what should be done.
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How do I divide my work into patches?
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-------------------------------------
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Put yourself in the shoes of the reviewer. Each patch is read separately
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and therefore should constitute a comprehensible step towards your stated
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goal.
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Avoid sending series longer than 15 patches. Larger series takes longer
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to review as reviewers will defer looking at it until they find a large
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chunk of time. A small series can be reviewed in a short time, so Maintainers
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just do it. As a result, a sequence of smaller series gets merged quicker and
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with better review coverage. Re-posting large series also increases the mailing
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list traffic.
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I made changes to only a few patches in a patch series should I resend only those changed?
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------------------------------------------------------------------------------------------
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No, please resend the entire patch series and make sure you do number your
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patches such that it is clear this is the latest and greatest set of patches
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that can be applied.
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I have received review feedback, when should I post a revised version of the patches?
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-------------------------------------------------------------------------------------
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Allow at least 24 hours to pass between postings. This will ensure reviewers
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from all geographical locations have a chance to chime in. Do not wait
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too long (weeks) between postings either as it will make it harder for reviewers
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to recall all the context.
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Make sure you address all the feedback in your new posting. Do not post a new
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version of the code if the discussion about the previous version is still
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ongoing, unless directly instructed by a reviewer.
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I submitted multiple versions of a patch series and it looks like a version other than the last one has been accepted, what should I do?
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----------------------------------------------------------------------------------------------------------------------------------------
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There is no revert possible, once it is pushed out, it stays like that.
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Please send incremental versions on top of what has been merged in order to fix
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the patches the way they would look like if your latest patch series was to be
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merged.
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Are there special rules regarding stable submissions on netdev?
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---------------------------------------------------------------
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While it used to be the case that netdev submissions were not supposed
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to carry explicit ``CC: stable@vger.kernel.org`` tags that is no longer
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the case today. Please follow the standard stable rules in
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:ref:`Documentation/process/stable-kernel-rules.rst <stable_kernel_rules>`,
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and make sure you include appropriate Fixes tags!
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Is the comment style convention different for the networking content?
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---------------------------------------------------------------------
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Yes, in a largely trivial way. Instead of this::
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/*
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* foobar blah blah blah
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* another line of text
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*/
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it is requested that you make it look like this::
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/* foobar blah blah blah
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* another line of text
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*/
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What is "reverse xmas tree"?
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----------------------------
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Netdev has a convention for ordering local variables in functions.
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Order the variable declaration lines longest to shortest, e.g.::
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struct scatterlist *sg;
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struct sk_buff *skb;
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int err, i;
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If there are dependencies between the variables preventing the ordering
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move the initialization out of line.
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I am working in existing code which uses non-standard formatting. Which formatting should I use?
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------------------------------------------------------------------------------------------------
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Make your code follow the most recent guidelines, so that eventually all code
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in the domain of netdev is in the preferred format.
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I found a bug that might have possible security implications or similar. Should I mail the main netdev maintainer off-list?
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---------------------------------------------------------------------------------------------------------------------------
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No. The current netdev maintainer has consistently requested that
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people use the mailing lists and not reach out directly. If you aren't
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OK with that, then perhaps consider mailing security@kernel.org or
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reading about http://oss-security.openwall.org/wiki/mailing-lists/distros
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as possible alternative mechanisms.
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What level of testing is expected before I submit my change?
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------------------------------------------------------------
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At the very minimum your changes must survive an ``allyesconfig`` and an
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``allmodconfig`` build with ``W=1`` set without new warnings or failures.
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Ideally you will have done run-time testing specific to your change,
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and the patch series contains a set of kernel selftest for
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``tools/testing/selftests/net`` or using the KUnit framework.
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You are expected to test your changes on top of the relevant networking
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tree (``net`` or ``net-next``) and not e.g. a stable tree or ``linux-next``.
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How do I post corresponding changes to user space components?
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-------------------------------------------------------------
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User space code exercising kernel features should be posted
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alongside kernel patches. This gives reviewers a chance to see
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how any new interface is used and how well it works.
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When user space tools reside in the kernel repo itself all changes
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should generally come as one series. If series becomes too large
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or the user space project is not reviewed on netdev include a link
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to a public repo where user space patches can be seen.
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In case user space tooling lives in a separate repository but is
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reviewed on netdev (e.g. patches to ``iproute2`` tools) kernel and
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user space patches should form separate series (threads) when posted
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to the mailing list, e.g.::
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[PATCH net-next 0/3] net: some feature cover letter
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└─ [PATCH net-next 1/3] net: some feature prep
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└─ [PATCH net-next 2/3] net: some feature do it
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└─ [PATCH net-next 3/3] selftest: net: some feature
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[PATCH iproute2-next] ip: add support for some feature
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Posting as one thread is discouraged because it confuses patchwork
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(as of patchwork 2.2.2).
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Can I reproduce the checks from patchwork on my local machine?
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--------------------------------------------------------------
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Checks in patchwork are mostly simple wrappers around existing kernel
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scripts, the sources are available at:
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https://github.com/kuba-moo/nipa/tree/master/tests
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Running all the builds and checks locally is a pain, can I post my patches and have the patchwork bot validate them?
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--------------------------------------------------------------------------------------------------------------------
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No, you must ensure that your patches are ready by testing them locally
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before posting to the mailing list. The patchwork build bot instance
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gets overloaded very easily and netdev@vger really doesn't need more
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traffic if we can help it.
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netdevsim is great, can I extend it for my out-of-tree tests?
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-------------------------------------------------------------
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No, ``netdevsim`` is a test vehicle solely for upstream tests.
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(Please add your tests under ``tools/testing/selftests/``.)
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We also give no guarantees that ``netdevsim`` won't change in the future
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in a way which would break what would normally be considered uAPI.
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Is netdevsim considered a "user" of an API?
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-------------------------------------------
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Linux kernel has a long standing rule that no API should be added unless
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it has a real, in-tree user. Mock-ups and tests based on ``netdevsim`` are
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strongly encouraged when adding new APIs, but ``netdevsim`` in itself
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is **not** considered a use case/user.
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Any other tips to help ensure my net/net-next patch gets OK'd?
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--------------------------------------------------------------
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Attention to detail. Re-read your own work as if you were the
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reviewer. You can start with using ``checkpatch.pl``, perhaps even with
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the ``--strict`` flag. But do not be mindlessly robotic in doing so.
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If your change is a bug fix, make sure your commit log indicates the
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end-user visible symptom, the underlying reason as to why it happens,
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and then if necessary, explain why the fix proposed is the best way to
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get things done. Don't mangle whitespace, and as is common, don't
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mis-indent function arguments that span multiple lines. If it is your
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first patch, mail it to yourself so you can test apply it to an
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unpatched tree to confirm infrastructure didn't mangle it.
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Finally, go back and read
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:ref:`Documentation/process/submitting-patches.rst <submittingpatches>`
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to be sure you are not repeating some common mistake documented there.
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My company uses peer feedback in employee performance reviews. Can I ask netdev maintainers for feedback?
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---------------------------------------------------------------------------------------------------------
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Yes, especially if you spend significant amount of time reviewing code
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and go out of your way to improve shared infrastructure.
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The feedback must be requested by you, the contributor, and will always
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be shared with you (even if you request for it to be submitted to your
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manager).
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