docs: net: Convert netdev-FAQ to restructured text

	- HOWTO for multiqueue network device support.

netconsole.txt

	- The network console module netconsole.ko: configuration and notes.

netdev-FAQ.txt

	- FAQ describing how to submit net changes to netdev mailing list.

netdev-features.txt

	- Network interface features API description.

netdevices.txt

.. toctree::

   :maxdepth: 2

   netdev-FAQ

   af_xdp

   batman-adv

   can

.. SPDX-License-Identifier: GPL-2.0

.. _netdev-FAQ:

==========

netdev FAQ

==========

Q: What is netdev?

------------------

A: It 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.

The netdev list is managed (like many other Linux mailing lists) through

VGER (http://vger.kernel.org/) and archives can be found below:

-  http://marc.info/?l=linux-netdev

-  http://www.spinics.net/lists/netdev/

Aside from subsystems like that mentioned above, all network-related

Linux development (i.e. RFC, review, comments, etc.) takes place on

netdev.

Q: How do the changes posted to netdev make their way into Linux?

-----------------------------------------------------------------

A: There are always two 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/davem/net.git

- https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git

Q: How often do changes from these trees make it to the mainline Linus tree?

----------------------------------------------------------------------------

A: To understand this, you need to know 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.

Relating that to netdev: 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.

IMPORTANT: Do not send new ``net-next`` content to netdev during the

period during which ``net-next`` tree is closed.

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:

  http://vger.kernel.org/~davem/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.

Q: So where are we now in this 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.

Q: How do I indicate which tree (net vs. net-next) my patch should be in?

-------------------------------------------------------------------------

A: Firstly, think whether you have a bug fix or new "next-like" content.

Then once decided, assuming that you use git, use the prefix flag, i.e.

::

  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.  If you don't use git, then note the only magic

in the above is just the subject text of the outgoing e-mail, and you

can manually change it yourself with whatever MUA you are comfortable

with.

Q: I sent a patch and I'm wondering what happened to it?

--------------------------------------------------------

Q: How can I tell whether it got merged?

A: Start by looking at the main patchworks queue for netdev:

  http://patchwork.ozlabs.org/project/netdev/list/

The "State" field will tell you exactly where things are at with your

patch.

Q: The above only says "Under Review".  How can I find out more?

----------------------------------------------------------------

A: Generally speaking, the patches get triaged quickly (in less than

48h).  So be patient.  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.

Q: I submitted multiple versions of the patch series

----------------------------------------------------

Q: should I directly update patchwork for the previous versions of these

patch series?

A: No, please don't interfere with the patch status on patchwork, leave

it to the maintainer to figure out what is the most recent and current

version that should be applied. If there is any doubt, the maintainer

will reply and ask what should be done.

Q: How can I tell what patches are queued up for backporting to the various stable releases?

--------------------------------------------------------------------------------------------

A: Normally Greg Kroah-Hartman collects stable commits himself, but for

networking, Dave collects up patches he deems critical for the

networking subsystem, and then hands them off to Greg.

There is a patchworks queue that you can see here:

  http://patchwork.ozlabs.org/bundle/davem/stable/?state=*

It contains the patches which Dave has selected, but not yet handed off

to Greg.  If Greg already has the patch, then it will be here:

  https://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git

A quick way to find whether the patch is in this stable-queue is to

simply clone the repo, and then git grep the mainline commit ID, e.g.

::

  stable-queue$ git grep -l 284041ef21fdf2e

  releases/3.0.84/ipv6-fix-possible-crashes-in-ip6_cork_release.patch

  releases/3.4.51/ipv6-fix-possible-crashes-in-ip6_cork_release.patch

  releases/3.9.8/ipv6-fix-possible-crashes-in-ip6_cork_release.patch

  stable/stable-queue$

Q: I see a network patch and I think it should be backported to stable.

-----------------------------------------------------------------------

Q: Should I request it via stable@vger.kernel.org like the references in

the kernel's Documentation/process/stable-kernel-rules.rst file say?

A: No, not for networking.  Check the stable queues as per above first

to see if it is already queued.  If not, then send a mail to netdev,

listing the upstream commit ID and why you think it should be a stable

candidate.

Before you jump to go do the above, do note that the normal stable rules

in :ref:`Documentation/process/stable-kernel-rules.rst <stable_kernel_rules>`

still apply.  So you need to explicitly indicate why it is a critical

fix and exactly what users are impacted.  In addition, you need to

convince yourself that you *really* think it has been overlooked,

vs. having been considered and rejected.

Generally speaking, the longer it has had a chance to "soak" in

mainline, the better the odds that it is an OK candidate for stable.  So

scrambling to request a commit be added the day after it appears should

be avoided.

Q: I have created a network patch and I think it should be backported to stable.

--------------------------------------------------------------------------------

Q: Should I add a Cc: stable@vger.kernel.org like the references in the

kernel's Documentation/ directory say?

A: No.  See above answer.  In short, if you think it really belongs in

stable, then ensure you write a decent commit log that describes who

gets impacted by the bug fix and how it manifests itself, and when the

bug was introduced.  If you do that properly, then the commit will get

handled appropriately and most likely get put in the patchworks stable

queue if it really warrants it.

If you think there is some valid information relating to it being in

stable that does *not* belong in the commit log, then use the three dash

marker line as described in

:ref:`Documentation/process/submitting-patches.rst <the_canonical_patch_format>`

to temporarily embed that information into the patch that you send.

Q: Are all networking bug fixes backported to all stable releases?

------------------------------------------------------------------

A: Due to capacity, Dave could only take care of the backports for the

last two stable releases. For earlier stable releases, each stable

branch maintainer is supposed to take care of them. If you find any

patch is missing from an earlier stable branch, please notify

stable@vger.kernel.org with either a commit ID or a formal patch

backported, and CC Dave and other relevant networking developers.

Q: Is the comment style convention different for the networking content?

------------------------------------------------------------------------

A: Yes, in a largely trivial way.  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

   */

Q: I am working in existing code that has the former comment style and not the latter.

--------------------------------------------------------------------------------------

Q: Should I submit new code in the former style or the latter?

A: Make it the latter style, so that eventually all code in the domain

of netdev is of this format.

Q: I found a bug that might have possible security implications or similar.

---------------------------------------------------------------------------

Q: Should I mail the main netdev maintainer off-list?**

A: No. 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.

Q: What level of testing is expected before I submit my change?

---------------------------------------------------------------

A: If your changes are against ``net-next``, the expectation is that you

have tested by layering your changes on top of ``net-next``.  Ideally

you will have done run-time testing specific to your change, but at a

minimum, your changes should survive an ``allyesconfig`` and an

``allmodconfig`` build without new warnings or failures.

Q: Any other tips to help ensure my net/net-next patch gets OK'd?

-----------------------------------------------------------------

A: Attention to detail.  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.

Information you need to know about netdev

-----------------------------------------

Q: What is netdev?

A: It 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.

   The netdev list is managed (like many other Linux mailing lists) through

   VGER ( http://vger.kernel.org/ ) and archives can be found below:

	http://marc.info/?l=linux-netdev

	http://www.spinics.net/lists/netdev/

   Aside from subsystems like that mentioned above, all network-related Linux

   development (i.e. RFC, review, comments, etc.) takes place on netdev.

Q: How do the changes posted to netdev make their way into Linux?

A: There are always two 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/davem/net.git

        https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git

Q: How often do changes from these trees make it to the mainline Linus tree?

A: To understand this, you need to know 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.

   Relating that to netdev:  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.

   IMPORTANT:  Do not send new net-next content to netdev during the

   period during which net-next tree is closed.

   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:

        http://vger.kernel.org/~davem/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 bugfixes.

   Finally, the vX.Y gets released, and the whole cycle starts over.

Q: So where are we now in this cycle?

A: 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.

Q: How do I indicate which tree (net vs. net-next) my patch should be in?

A: Firstly, think whether you have a bug fix or new "next-like" content.

   Then once decided, assuming that you use git, use the prefix flag, i.e.

	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.  If you don't use git, then note the only magic in

   the above is just the subject text of the outgoing e-mail, and you can

   manually change it yourself with whatever MUA you are comfortable with.

Q: I sent a patch and I'm wondering what happened to it.  How can I tell

   whether it got merged?

A: Start by looking at the main patchworks queue for netdev:

	http://patchwork.ozlabs.org/project/netdev/list/

   The "State" field will tell you exactly where things are at with

   your patch.

Q: The above only says "Under Review".  How can I find out more?

A: Generally speaking, the patches get triaged quickly (in less than 48h).

   So be patient.  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.

Q: I submitted multiple versions of the patch series, should I directly update

   patchwork for the previous versions of these patch series?

A: No, please don't interfere with the patch status on patchwork, leave it to

   the maintainer to figure out what is the most recent and current version that

   should be applied. If there is any doubt, the maintainer will reply and ask

   what should be done.

Q: How can I tell what patches are queued up for backporting to the

   various stable releases?

A: Normally Greg Kroah-Hartman collects stable commits himself, but

   for networking, Dave collects up patches he deems critical for the

   networking subsystem, and then hands them off to Greg.

   There is a patchworks queue that you can see here:

	http://patchwork.ozlabs.org/bundle/davem/stable/?state=*

   It contains the patches which Dave has selected, but not yet handed

   off to Greg.  If Greg already has the patch, then it will be here:

	https://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git

   A quick way to find whether the patch is in this stable-queue is

   to simply clone the repo, and then git grep the mainline commit ID, e.g.

	stable-queue$ git grep -l 284041ef21fdf2e

	releases/3.0.84/ipv6-fix-possible-crashes-in-ip6_cork_release.patch

	releases/3.4.51/ipv6-fix-possible-crashes-in-ip6_cork_release.patch

	releases/3.9.8/ipv6-fix-possible-crashes-in-ip6_cork_release.patch

	stable/stable-queue$

Q: I see a network patch and I think it should be backported to stable.

   Should I request it via "stable@vger.kernel.org" like the references in

   the kernel's Documentation/process/stable-kernel-rules.rst file say?

A: No, not for networking.  Check the stable queues as per above 1st to see

   if it is already queued.  If not, then send a mail to netdev, listing

   the upstream commit ID and why you think it should be a stable candidate.

   Before you jump to go do the above, do note that the normal stable rules

   in Documentation/process/stable-kernel-rules.rst still apply.  So you need to

   explicitly indicate why it is a critical fix and exactly what users are

   impacted.  In addition, you need to convince yourself that you _really_

   think it has been overlooked, vs. having been considered and rejected.

   Generally speaking, the longer it has had a chance to "soak" in mainline,

   the better the odds that it is an OK candidate for stable.  So scrambling

   to request a commit be added the day after it appears should be avoided.

Q: I have created a network patch and I think it should be backported to

   stable.  Should I add a "Cc: stable@vger.kernel.org" like the references

   in the kernel's Documentation/ directory say?

A: No.  See above answer.  In short, if you think it really belongs in

   stable, then ensure you write a decent commit log that describes who

   gets impacted by the bugfix and how it manifests itself, and when the

   bug was introduced.  If you do that properly, then the commit will

   get handled appropriately and most likely get put in the patchworks

   stable queue if it really warrants it.

   If you think there is some valid information relating to it being in

   stable that does _not_ belong in the commit log, then use the three

   dash marker line as described in Documentation/process/submitting-patches.rst to

   temporarily embed that information into the patch that you send.

Q: Are all networking bug fixes backported to all stable releases?

A: Due to capacity, Dave could only take care of the backports for the last

   2 stable releases. For earlier stable releases, each stable branch maintainer

   is supposed to take care of them. If you find any patch is missing from an

   earlier stable branch, please notify stable@vger.kernel.org with either a

   commit ID or a formal patch backported, and CC Dave and other relevant

   networking developers.

Q: Someone said that the comment style and coding convention is different

   for the networking content.  Is this true?

A: Yes, in a largely trivial way.  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

	 */

Q: I am working in existing code that has the former comment style and not the

   latter.  Should I submit new code in the former style or the latter?

A: Make it the latter style, so that eventually all code in the domain of

   netdev is of this format.

Q: I found a bug that might have possible security implications or similar.

   Should I mail the main netdev maintainer off-list?

A: No. 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.

Q: What level of testing is expected before I submit my change?

A: If your changes are against net-next, the expectation is that you

   have tested by layering your changes on top of net-next.  Ideally you

   will have done run-time testing specific to your change, but at a

   minimum, your changes should survive an "allyesconfig" and an

   "allmodconfig" build without new warnings or failures.

Q: Any other tips to help ensure my net/net-next patch gets OK'd?

A: Attention to detail.  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 Documentation/process/submitting-patches.rst to be

   sure you are not repeating some common mistake documented there.