1.. SPDX-License-Identifier: GPL-2.0
2
3.. _netdev-FAQ:
4
5==========
6netdev FAQ
7==========
8
9tl;dr
10-----
11
12 - designate your patch to a tree - ``[PATCH net]`` or ``[PATCH net-next]``
13 - for fixes the ``Fixes:`` tag is required, regardless of the tree
14 - don't post large series (> 15 patches), break them up
15 - don't repost your patches within one 24h period
16 - reverse xmas tree
17
18What is netdev?
19---------------
20It is a mailing list for all network-related Linux stuff.  This
21includes anything found under net/ (i.e. core code like IPv6) and
22drivers/net (i.e. hardware specific drivers) in the Linux source tree.
23
24Note that some subsystems (e.g. wireless drivers) which have a high
25volume of traffic have their own specific mailing lists.
26
27The netdev list is managed (like many other Linux mailing lists) through
28VGER (http://vger.kernel.org/) with archives available at
29https://lore.kernel.org/netdev/
30
31Aside from subsystems like those mentioned above, all network-related
32Linux development (i.e. RFC, review, comments, etc.) takes place on
33netdev.
34
35How do the changes posted to netdev make their way into Linux?
36--------------------------------------------------------------
37There are always two trees (git repositories) in play.  Both are
38driven by David Miller, the main network maintainer.  There is the
39``net`` tree, and the ``net-next`` tree.  As you can probably guess from
40the names, the ``net`` tree is for fixes to existing code already in the
41mainline tree from Linus, and ``net-next`` is where the new code goes
42for the future release.  You can find the trees here:
43
44- https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git
45- https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git
46
47How do I indicate which tree (net vs. net-next) my patch should be in?
48----------------------------------------------------------------------
49To help maintainers and CI bots you should explicitly mark which tree
50your patch is targeting. Assuming that you use git, use the prefix
51flag::
52
53  git format-patch --subject-prefix='PATCH net-next' start..finish
54
55Use ``net`` instead of ``net-next`` (always lower case) in the above for
56bug-fix ``net`` content.
57
58How often do changes from these trees make it to the mainline Linus tree?
59-------------------------------------------------------------------------
60To understand this, you need to know a bit of background information on
61the cadence of Linux development.  Each new release starts off with a
62two week "merge window" where the main maintainers feed their new stuff
63to Linus for merging into the mainline tree.  After the two weeks, the
64merge window is closed, and it is called/tagged ``-rc1``.  No new
65features get mainlined after this -- only fixes to the rc1 content are
66expected.  After roughly a week of collecting fixes to the rc1 content,
67rc2 is released.  This repeats on a roughly weekly basis until rc7
68(typically; sometimes rc6 if things are quiet, or rc8 if things are in a
69state of churn), and a week after the last vX.Y-rcN was done, the
70official vX.Y is released.
71
72Relating that to netdev: At the beginning of the 2-week merge window,
73the ``net-next`` tree will be closed - no new changes/features.  The
74accumulated new content of the past ~10 weeks will be passed onto
75mainline/Linus via a pull request for vX.Y -- at the same time, the
76``net`` tree will start accumulating fixes for this pulled content
77relating to vX.Y
78
79An announcement indicating when ``net-next`` has been closed is usually
80sent to netdev, but knowing the above, you can predict that in advance.
81
82.. warning::
83  Do not send new ``net-next`` content to netdev during the
84  period during which ``net-next`` tree is closed.
85
86RFC patches sent for review only are obviously welcome at any time
87(use ``--subject-prefix='RFC net-next'`` with ``git format-patch``).
88
89Shortly after the two weeks have passed (and vX.Y-rc1 is released), the
90tree for ``net-next`` reopens to collect content for the next (vX.Y+1)
91release.
92
93If you aren't subscribed to netdev and/or are simply unsure if
94``net-next`` has re-opened yet, simply check the ``net-next`` git
95repository link above for any new networking-related commits.  You may
96also check the following website for the current status:
97
98  http://vger.kernel.org/~davem/net-next.html
99
100The ``net`` tree continues to collect fixes for the vX.Y content, and is
101fed back to Linus at regular (~weekly) intervals.  Meaning that the
102focus for ``net`` is on stabilization and bug fixes.
103
104Finally, the vX.Y gets released, and the whole cycle starts over.
105
106So where are we now in this cycle?
107----------------------------------
108
109Load the mainline (Linus) page here:
110
111  https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
112
113and note the top of the "tags" section.  If it is rc1, it is early in
114the dev cycle.  If it was tagged rc7 a week ago, then a release is
115probably imminent. If the most recent tag is a final release tag
116(without an ``-rcN`` suffix) - we are most likely in a merge window
117and ``net-next`` is closed.
118
119How can I tell the status of a patch I've sent?
120-----------------------------------------------
121Start by looking at the main patchworks queue for netdev:
122
123  https://patchwork.kernel.org/project/netdevbpf/list/
124
125The "State" field will tell you exactly where things are at with your
126patch. Patches are indexed by the ``Message-ID`` header of the emails
127which carried them so if you have trouble finding your patch append
128the value of ``Message-ID`` to the URL above.
129
130How long before my patch is accepted?
131-------------------------------------
132Generally speaking, the patches get triaged quickly (in less than
13348h). But be patient, if your patch is active in patchwork (i.e. it's
134listed on the project's patch list) the chances it was missed are close to zero.
135Asking the maintainer for status updates on your
136patch is a good way to ensure your patch is ignored or pushed to the
137bottom of the priority list.
138
139Should I directly update patchwork state of my own patches?
140-----------------------------------------------------------
141It may be tempting to help the maintainers and update the state of your
142own patches when you post a new version or spot a bug. Please do not do that.
143Interfering with the patch status on patchwork will only cause confusion. Leave
144it to the maintainer to figure out what is the most recent and current
145version that should be applied. If there is any doubt, the maintainer
146will reply and ask what should be done.
147
148How do I divide my work into patches?
149-------------------------------------
150
151Put yourself in the shoes of the reviewer. Each patch is read separately
152and therefore should constitute a comprehensible step towards your stated
153goal.
154
155Avoid sending series longer than 15 patches. Larger series takes longer
156to review as reviewers will defer looking at it until they find a large
157chunk of time. A small series can be reviewed in a short time, so Maintainers
158just do it. As a result, a sequence of smaller series gets merged quicker and
159with better review coverage. Re-posting large series also increases the mailing
160list traffic.
161
162I made changes to only a few patches in a patch series should I resend only those changed?
163------------------------------------------------------------------------------------------
164No, please resend the entire patch series and make sure you do number your
165patches such that it is clear this is the latest and greatest set of patches
166that can be applied.
167
168I have received review feedback, when should I post a revised version of the patches?
169-------------------------------------------------------------------------------------
170Allow at least 24 hours to pass between postings. This will ensure reviewers
171from all geographical locations have a chance to chime in. Do not wait
172too long (weeks) between postings either as it will make it harder for reviewers
173to recall all the context.
174
175Make sure you address all the feedback in your new posting. Do not post a new
176version of the code if the discussion about the previous version is still
177ongoing, unless directly instructed by a reviewer.
178
179I 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?
180----------------------------------------------------------------------------------------------------------------------------------------
181There is no revert possible, once it is pushed out, it stays like that.
182Please send incremental versions on top of what has been merged in order to fix
183the patches the way they would look like if your latest patch series was to be
184merged.
185
186Are there special rules regarding stable submissions on netdev?
187---------------------------------------------------------------
188While it used to be the case that netdev submissions were not supposed
189to carry explicit ``CC: stable@vger.kernel.org`` tags that is no longer
190the case today. Please follow the standard stable rules in
191:ref:`Documentation/process/stable-kernel-rules.rst <stable_kernel_rules>`,
192and make sure you include appropriate Fixes tags!
193
194Is the comment style convention different for the networking content?
195---------------------------------------------------------------------
196Yes, in a largely trivial way.  Instead of this::
197
198  /*
199   * foobar blah blah blah
200   * another line of text
201   */
202
203it is requested that you make it look like this::
204
205  /* foobar blah blah blah
206   * another line of text
207   */
208
209What is "reverse xmas tree"?
210----------------------------
211
212Netdev has a convention for ordering local variables in functions.
213Order the variable declaration lines longest to shortest, e.g.::
214
215  struct scatterlist *sg;
216  struct sk_buff *skb;
217  int err, i;
218
219If there are dependencies between the variables preventing the ordering
220move the initialization out of line.
221
222I am working in existing code which uses non-standard formatting. Which formatting should I use?
223------------------------------------------------------------------------------------------------
224Make your code follow the most recent guidelines, so that eventually all code
225in the domain of netdev is in the preferred format.
226
227I found a bug that might have possible security implications or similar. Should I mail the main netdev maintainer off-list?
228---------------------------------------------------------------------------------------------------------------------------
229No. The current netdev maintainer has consistently requested that
230people use the mailing lists and not reach out directly.  If you aren't
231OK with that, then perhaps consider mailing security@kernel.org or
232reading about http://oss-security.openwall.org/wiki/mailing-lists/distros
233as possible alternative mechanisms.
234
235What level of testing is expected before I submit my change?
236------------------------------------------------------------
237At the very minimum your changes must survive an ``allyesconfig`` and an
238``allmodconfig`` build with ``W=1`` set without new warnings or failures.
239
240Ideally you will have done run-time testing specific to your change,
241and the patch series contains a set of kernel selftest for
242``tools/testing/selftests/net`` or using the KUnit framework.
243
244You are expected to test your changes on top of the relevant networking
245tree (``net`` or ``net-next``) and not e.g. a stable tree or ``linux-next``.
246
247How do I post corresponding changes to user space components?
248-------------------------------------------------------------
249User space code exercising kernel features should be posted
250alongside kernel patches. This gives reviewers a chance to see
251how any new interface is used and how well it works.
252
253When user space tools reside in the kernel repo itself all changes
254should generally come as one series. If series becomes too large
255or the user space project is not reviewed on netdev include a link
256to a public repo where user space patches can be seen.
257
258In case user space tooling lives in a separate repository but is
259reviewed on netdev  (e.g. patches to ``iproute2`` tools) kernel and
260user space patches should form separate series (threads) when posted
261to the mailing list, e.g.::
262
263  [PATCH net-next 0/3] net: some feature cover letter
264   └─ [PATCH net-next 1/3] net: some feature prep
265   └─ [PATCH net-next 2/3] net: some feature do it
266   └─ [PATCH net-next 3/3] selftest: net: some feature
267
268  [PATCH iproute2-next] ip: add support for some feature
269
270Posting as one thread is discouraged because it confuses patchwork
271(as of patchwork 2.2.2).
272
273Can I reproduce the checks from patchwork on my local machine?
274--------------------------------------------------------------
275
276Checks in patchwork are mostly simple wrappers around existing kernel
277scripts, the sources are available at:
278
279https://github.com/kuba-moo/nipa/tree/master/tests
280
281Running all the builds and checks locally is a pain, can I post my patches and have the patchwork bot validate them?
282--------------------------------------------------------------------------------------------------------------------
283
284No, you must ensure that your patches are ready by testing them locally
285before posting to the mailing list. The patchwork build bot instance
286gets overloaded very easily and netdev@vger really doesn't need more
287traffic if we can help it.
288
289netdevsim is great, can I extend it for my out-of-tree tests?
290-------------------------------------------------------------
291
292No, ``netdevsim`` is a test vehicle solely for upstream tests.
293(Please add your tests under ``tools/testing/selftests/``.)
294
295We also give no guarantees that ``netdevsim`` won't change in the future
296in a way which would break what would normally be considered uAPI.
297
298Is netdevsim considered a "user" of an API?
299-------------------------------------------
300
301Linux kernel has a long standing rule that no API should be added unless
302it has a real, in-tree user. Mock-ups and tests based on ``netdevsim`` are
303strongly encouraged when adding new APIs, but ``netdevsim`` in itself
304is **not** considered a use case/user.
305
306Any other tips to help ensure my net/net-next patch gets OK'd?
307--------------------------------------------------------------
308Attention to detail.  Re-read your own work as if you were the
309reviewer.  You can start with using ``checkpatch.pl``, perhaps even with
310the ``--strict`` flag.  But do not be mindlessly robotic in doing so.
311If your change is a bug fix, make sure your commit log indicates the
312end-user visible symptom, the underlying reason as to why it happens,
313and then if necessary, explain why the fix proposed is the best way to
314get things done.  Don't mangle whitespace, and as is common, don't
315mis-indent function arguments that span multiple lines.  If it is your
316first patch, mail it to yourself so you can test apply it to an
317unpatched tree to confirm infrastructure didn't mangle it.
318
319Finally, go back and read
320:ref:`Documentation/process/submitting-patches.rst <submittingpatches>`
321to be sure you are not repeating some common mistake documented there.
322