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:

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:

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:

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:

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:

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:

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:

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 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.

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 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 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 Documentation/process/submitting-patches.rst to be sure you are not repeating some common mistake documented there.