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+.. SPDX-License-Identifier: GPL-2.0
+
+.. _netdev-FAQ:
+
+=============================
+Networking subsystem (netdev)
+=============================
+
+tl;dr
+-----
+
+ - designate your patch to a tree - ``[PATCH net]`` or ``[PATCH net-next]``
+ - for fixes the ``Fixes:`` tag is required, regardless of the tree
+ - don't post large series (> 15 patches), break them up
+ - don't repost your patches within one 24h period
+ - reverse xmas tree
+
+netdev
+------
+
+netdev is a mailing list for all network-related Linux stuff. This
+includes anything found under net/ (i.e. core code like IPv6) and
+drivers/net (i.e. hardware specific drivers) in the Linux source tree.
+
+Note that some subsystems (e.g. wireless drivers) which have a high
+volume of traffic have their own specific mailing lists and trees.
+
+The netdev list is managed (like many other Linux mailing lists) through
+VGER (http://vger.kernel.org/) with archives available at
+https://lore.kernel.org/netdev/
+
+Aside from subsystems like those mentioned above, all network-related
+Linux development (i.e. RFC, review, comments, etc.) takes place on
+netdev.
+
+Development cycle
+-----------------
+
+Here is a bit of background information on
+the cadence of Linux development. Each new release starts off with a
+two week "merge window" where the main maintainers feed their new stuff
+to Linus for merging into the mainline tree. After the two weeks, the
+merge window is closed, and it is called/tagged ``-rc1``. No new
+features get mainlined after this -- only fixes to the rc1 content are
+expected. After roughly a week of collecting fixes to the rc1 content,
+rc2 is released. This repeats on a roughly weekly basis until rc7
+(typically; sometimes rc6 if things are quiet, or rc8 if things are in a
+state of churn), and a week after the last vX.Y-rcN was done, the
+official vX.Y is released.
+
+To find out where we are now in the cycle - load the mainline (Linus)
+page here:
+
+ https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
+
+and note the top of the "tags" section. If it is rc1, it is early in
+the dev cycle. If it was tagged rc7 a week ago, then a release is
+probably imminent. If the most recent tag is a final release tag
+(without an ``-rcN`` suffix) - we are most likely in a merge window
+and ``net-next`` is closed.
+
+git trees and patch flow
+------------------------
+
+There are two networking trees (git repositories) in play. Both are
+driven by David Miller, the main network maintainer. There is the
+``net`` tree, and the ``net-next`` tree. As you can probably guess from
+the names, the ``net`` tree is for fixes to existing code already in the
+mainline tree from Linus, and ``net-next`` is where the new code goes
+for the future release. You can find the trees here:
+
+- https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git
+- https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git
+
+Relating that to kernel development: At the beginning of the 2-week
+merge window, the ``net-next`` tree will be closed - no new changes/features.
+The accumulated new content of the past ~10 weeks will be passed onto
+mainline/Linus via a pull request for vX.Y -- at the same time, the
+``net`` tree will start accumulating fixes for this pulled content
+relating to vX.Y
+
+An announcement indicating when ``net-next`` has been closed is usually
+sent to netdev, but knowing the above, you can predict that in advance.
+
+.. warning::
+ Do not send new ``net-next`` content to netdev during the
+ period during which ``net-next`` tree is closed.
+
+RFC patches sent for review only are obviously welcome at any time
+(use ``--subject-prefix='RFC net-next'`` with ``git format-patch``).
+
+Shortly after the two weeks have passed (and vX.Y-rc1 is released), the
+tree for ``net-next`` reopens to collect content for the next (vX.Y+1)
+release.
+
+If you aren't subscribed to netdev and/or are simply unsure if
+``net-next`` has re-opened yet, simply check the ``net-next`` git
+repository link above for any new networking-related commits. You may
+also check the following website for the current status:
+
+ https://netdev.bots.linux.dev/net-next.html
+
+The ``net`` tree continues to collect fixes for the vX.Y content, and is
+fed back to Linus at regular (~weekly) intervals. Meaning that the
+focus for ``net`` is on stabilization and bug fixes.
+
+Finally, the vX.Y gets released, and the whole cycle starts over.
+
+netdev patch review
+-------------------
+
+.. _patch_status:
+
+Patch status
+~~~~~~~~~~~~
+
+Status of a patch can be checked by looking at the main patchwork
+queue for netdev:
+
+ https://patchwork.kernel.org/project/netdevbpf/list/
+
+The "State" field will tell you exactly where things are at with your
+patch:
+
+================== =============================================================
+Patch state Description
+================== =============================================================
+New, Under review pending review, patch is in the maintainer’s queue for
+ review; the two states are used interchangeably (depending on
+ the exact co-maintainer handling patchwork at the time)
+Accepted patch was applied to the appropriate networking tree, this is
+ usually set automatically by the pw-bot
+Needs ACK waiting for an ack from an area expert or testing
+Changes requested patch has not passed the review, new revision is expected
+ with appropriate code and commit message changes
+Rejected patch has been rejected and new revision is not expected
+Not applicable patch is expected to be applied outside of the networking
+ subsystem
+Awaiting upstream patch should be reviewed and handled by appropriate
+ sub-maintainer, who will send it on to the networking trees;
+ patches set to ``Awaiting upstream`` in netdev's patchwork
+ will usually remain in this state, whether the sub-maintainer
+ requested changes, accepted or rejected the patch
+Deferred patch needs to be reposted later, usually due to dependency
+ or because it was posted for a closed tree
+Superseded new version of the patch was posted, usually set by the
+ pw-bot
+RFC not to be applied, usually not in maintainer’s review queue,
+ pw-bot can automatically set patches to this state based
+ on subject tags
+================== =============================================================
+
+Patches are indexed by the ``Message-ID`` header of the emails
+which carried them so if you have trouble finding your patch append
+the value of ``Message-ID`` to the URL above.
+
+Updating patch status
+~~~~~~~~~~~~~~~~~~~~~
+
+Contributors and reviewers do not have the permissions to update patch
+state directly in patchwork. Patchwork doesn't expose much information
+about the history of the state of patches, therefore having multiple
+people update the state leads to confusion.
+
+Instead of delegating patchwork permissions netdev uses a simple mail
+bot which looks for special commands/lines within the emails sent to
+the mailing list. For example to mark a series as Changes Requested
+one needs to send the following line anywhere in the email thread::
+
+ pw-bot: changes-requested
+
+As a result the bot will set the entire series to Changes Requested.
+This may be useful when author discovers a bug in their own series
+and wants to prevent it from getting applied.
+
+The use of the bot is entirely optional, if in doubt ignore its existence
+completely. Maintainers will classify and update the state of the patches
+themselves. No email should ever be sent to the list with the main purpose
+of communicating with the bot, the bot commands should be seen as metadata.
+
+The use of the bot is restricted to authors of the patches (the ``From:``
+header on patch submission and command must match!), maintainers of
+the modified code according to the MAINTAINERS file (again, ``From:``
+must match the MAINTAINERS entry) and a handful of senior reviewers.
+
+Bot records its activity here:
+
+ https://netdev.bots.linux.dev/pw-bot.html
+
+Review timelines
+~~~~~~~~~~~~~~~~
+
+Generally speaking, the patches get triaged quickly (in less than
+48h). But be patient, if your patch is active in patchwork (i.e. it's
+listed on the project's patch list) the chances it was missed are close to zero.
+Asking the maintainer for status updates on your
+patch is a good way to ensure your patch is ignored or pushed to the
+bottom of the priority list.
+
+.. _Changes requested:
+
+Changes requested
+~~~~~~~~~~~~~~~~~
+
+Patches :ref:`marked<patch_status>` as ``Changes Requested`` need
+to be revised. The new version should come with a change log,
+preferably including links to previous postings, for example::
+
+ [PATCH net-next v3] net: make cows go moo
+
+ Even users who don't drink milk appreciate hearing the cows go "moo".
+
+ The amount of mooing will depend on packet rate so should match
+ the diurnal cycle quite well.
+
+ Signed-of-by: Joe Defarmer <joe@barn.org>
+ ---
+ v3:
+ - add a note about time-of-day mooing fluctuation to the commit message
+ v2: https://lore.kernel.org/netdev/123themessageid@barn.org/
+ - fix missing argument in kernel doc for netif_is_bovine()
+ - fix memory leak in netdev_register_cow()
+ v1: https://lore.kernel.org/netdev/456getstheclicks@barn.org/
+
+The commit message should be revised to answer any questions reviewers
+had to ask in previous discussions. Occasionally the update of
+the commit message will be the only change in the new version.
+
+Partial resends
+~~~~~~~~~~~~~~~
+
+Please always resend the entire patch series and make sure you do number your
+patches such that it is clear this is the latest and greatest set of patches
+that can be applied. Do not try to resend just the patches which changed.
+
+Handling misapplied patches
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Occasionally a patch series gets applied before receiving critical feedback,
+or the wrong version of a series gets applied.
+
+Making the patch disappear once it is pushed out is not possible, the commit
+history in netdev trees is immutable.
+Please send incremental versions on top of what has been merged in order to fix
+the patches the way they would look like if your latest patch series was to be
+merged.
+
+In cases where full revert is needed the revert has to be submitted
+as a patch to the list with a commit message explaining the technical
+problems with the reverted commit. Reverts should be used as a last resort,
+when original change is completely wrong; incremental fixes are preferred.
+
+Stable tree
+~~~~~~~~~~~
+
+While it used to be the case that netdev submissions were not supposed
+to carry explicit ``CC: stable@vger.kernel.org`` tags that is no longer
+the case today. Please follow the standard stable rules in
+:ref:`Documentation/process/stable-kernel-rules.rst <stable_kernel_rules>`,
+and make sure you include appropriate Fixes tags!
+
+Security fixes
+~~~~~~~~~~~~~~
+
+Do not email netdev maintainers directly if you think you discovered
+a bug that might have possible security implications.
+The current netdev maintainer has consistently requested that
+people use the mailing lists and not reach out directly. If you aren't
+OK with that, then perhaps consider mailing security@kernel.org or
+reading about http://oss-security.openwall.org/wiki/mailing-lists/distros
+as possible alternative mechanisms.
+
+
+Co-posting changes to user space components
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+User space code exercising kernel features should be posted
+alongside kernel patches. This gives reviewers a chance to see
+how any new interface is used and how well it works.
+
+When user space tools reside in the kernel repo itself all changes
+should generally come as one series. If series becomes too large
+or the user space project is not reviewed on netdev include a link
+to a public repo where user space patches can be seen.
+
+In case user space tooling lives in a separate repository but is
+reviewed on netdev (e.g. patches to ``iproute2`` tools) kernel and
+user space patches should form separate series (threads) when posted
+to the mailing list, e.g.::
+
+ [PATCH net-next 0/3] net: some feature cover letter
+ └─ [PATCH net-next 1/3] net: some feature prep
+ └─ [PATCH net-next 2/3] net: some feature do it
+ └─ [PATCH net-next 3/3] selftest: net: some feature
+
+ [PATCH iproute2-next] ip: add support for some feature
+
+Posting as one thread is discouraged because it confuses patchwork
+(as of patchwork 2.2.2).
+
+Preparing changes
+-----------------
+
+Attention to detail is important. Re-read your own work as if you were the
+reviewer. You can start with using ``checkpatch.pl``, perhaps even with
+the ``--strict`` flag. But do not be mindlessly robotic in doing so.
+If your change is a bug fix, make sure your commit log indicates the
+end-user visible symptom, the underlying reason as to why it happens,
+and then if necessary, explain why the fix proposed is the best way to
+get things done. Don't mangle whitespace, and as is common, don't
+mis-indent function arguments that span multiple lines. If it is your
+first patch, mail it to yourself so you can test apply it to an
+unpatched tree to confirm infrastructure didn't mangle it.
+
+Finally, go back and read
+:ref:`Documentation/process/submitting-patches.rst <submittingpatches>`
+to be sure you are not repeating some common mistake documented there.
+
+Indicating target tree
+~~~~~~~~~~~~~~~~~~~~~~
+
+To help maintainers and CI bots you should explicitly mark which tree
+your patch is targeting. Assuming that you use git, use the prefix
+flag::
+
+ git format-patch --subject-prefix='PATCH net-next' start..finish
+
+Use ``net`` instead of ``net-next`` (always lower case) in the above for
+bug-fix ``net`` content.
+
+Dividing work into patches
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Put yourself in the shoes of the reviewer. Each patch is read separately
+and therefore should constitute a comprehensible step towards your stated
+goal.
+
+Avoid sending series longer than 15 patches. Larger series takes longer
+to review as reviewers will defer looking at it until they find a large
+chunk of time. A small series can be reviewed in a short time, so Maintainers
+just do it. As a result, a sequence of smaller series gets merged quicker and
+with better review coverage. Re-posting large series also increases the mailing
+list traffic.
+
+Multi-line comments
+~~~~~~~~~~~~~~~~~~~
+
+Comment style convention is slightly different for networking and most of
+the tree. Instead of this::
+
+ /*
+ * foobar blah blah blah
+ * another line of text
+ */
+
+it is requested that you make it look like this::
+
+ /* foobar blah blah blah
+ * another line of text
+ */
+
+Local variable ordering ("reverse xmas tree", "RCS")
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Netdev has a convention for ordering local variables in functions.
+Order the variable declaration lines longest to shortest, e.g.::
+
+ struct scatterlist *sg;
+ struct sk_buff *skb;
+ int err, i;
+
+If there are dependencies between the variables preventing the ordering
+move the initialization out of line.
+
+Format precedence
+~~~~~~~~~~~~~~~~~
+
+When working in existing code which uses nonstandard formatting make
+your code follow the most recent guidelines, so that eventually all code
+in the domain of netdev is in the preferred format.
+
+Resending after review
+~~~~~~~~~~~~~~~~~~~~~~
+
+Allow at least 24 hours to pass between postings. This will ensure reviewers
+from all geographical locations have a chance to chime in. Do not wait
+too long (weeks) between postings either as it will make it harder for reviewers
+to recall all the context.
+
+Make sure you address all the feedback in your new posting. Do not post a new
+version of the code if the discussion about the previous version is still
+ongoing, unless directly instructed by a reviewer.
+
+The new version of patches should be posted as a separate thread,
+not as a reply to the previous posting. Change log should include a link
+to the previous posting (see :ref:`Changes requested`).
+
+Testing
+-------
+
+Expected level of testing
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+At the very minimum your changes must survive an ``allyesconfig`` and an
+``allmodconfig`` build with ``W=1`` set without new warnings or failures.
+
+Ideally you will have done run-time testing specific to your change,
+and the patch series contains a set of kernel selftest for
+``tools/testing/selftests/net`` or using the KUnit framework.
+
+You are expected to test your changes on top of the relevant networking
+tree (``net`` or ``net-next``) and not e.g. a stable tree or ``linux-next``.
+
+patchwork checks
+~~~~~~~~~~~~~~~~
+
+Checks in patchwork are mostly simple wrappers around existing kernel
+scripts, the sources are available at:
+
+https://github.com/kuba-moo/nipa/tree/master/tests
+
+**Do not** post your patches just to run them through the checks.
+You must ensure that your patches are ready by testing them locally
+before posting to the mailing list. The patchwork build bot instance
+gets overloaded very easily and netdev@vger really doesn't need more
+traffic if we can help it.
+
+netdevsim
+~~~~~~~~~
+
+``netdevsim`` is a test driver which can be used to exercise driver
+configuration APIs without requiring capable hardware.
+Mock-ups and tests based on ``netdevsim`` are strongly encouraged when
+adding new APIs, but ``netdevsim`` in itself is **not** considered
+a use case/user. You must also implement the new APIs in a real driver.
+
+We give no guarantees that ``netdevsim`` won't change in the future
+in a way which would break what would normally be considered uAPI.
+
+``netdevsim`` is reserved for use by upstream tests only, so any
+new ``netdevsim`` features must be accompanied by selftests under
+``tools/testing/selftests/``.
+
+Testimonials / feedback
+-----------------------
+
+Some companies use peer feedback in employee performance reviews.
+Please feel free to request feedback from netdev maintainers,
+especially if you spend significant amount of time reviewing code
+and go out of your way to improve shared infrastructure.
+
+The feedback must be requested by you, the contributor, and will always
+be shared with you (even if you request for it to be submitted to your
+manager).