post: new article about recent changes

Covering different topics: Bug-fixes, improvements, apps support,
conferences, what's next.

Signed-off-by: Matthieu Baerts (NGI0) <[email protected]>

_posts/2024-10-28-summer-update.md

@@ -0,0 +1,217 @@
+---
+layout: post
+title:  "Summer update"
+---
+
+A bit more than 3 months after the last update, I think it is really time to
+share some updates about MPTCP! I have been quiet recently, not because I was on
+holiday -- even if I should probably take some :) -- but because there were
+always higher priority tasks than writing a new blog post which is something I'm
+slow at! Bug-fixes, improvements, apps support, conferences, what's next: read
+on to find out more about what happened recently!
+
+<!--more-->
+
+## More bug fixes
+
+In my [previous post]({% post_url 2024-07-21-maintainers-responsibilities %}), I
+mentioned I was working on fixing issues around the path-manager. A few more
+fixes have been added since then, and a lot of backports have been done:
+hundreds of commits have been added to the different stable kernels, up to v5.10
+when needed. If you see odd behaviour with the MPTCP path-manager, please check
+with an up-to-date kernel version first, maybe your issue has already been
+fixed!
+
+One important [issue](https://github.com/multipath-tcp/mptcp_net-next/issues/518)
+has also been fixed recently: some (weird) middleboxes were causing MPTCP
+connections to be reset, because MPTCP options were dropped later on during the
+connection, but not at the beginning. When possible, such connections are now
+forced to fall back to TCP. Middleboxes are still able to surprise us! :)
+
+## New improvements
+
+Some improvements have also been added during the last few months, e.g.
+
+- If MPTCP is explicitly blocked by a firewall, after 3 unsuccessful connection
+  requests, the kernel will fall back to TCP, and future connections will
+  directly use TCP for a configurable period of time -- 1 hour by default, then
+  it is exponential.
+
+- `SO_KEEPALIVE` socket option -- to send keep-alive packets in case of
+  connection inactivity -- has been supported by MPTCP for a few years now. But
+  it was not possible to fine tune this behaviour using `TCP_KEEP*` socket
+  options. This has been fixed, and exceptionally backported to stable versions,
+  because it was not normal to support the main option, but not these other
+  ones, this was blocking some deployments, and the code to support these socket
+  options is simple and not impacting the rest.
+
+- More `MIB` counters -- visible with `nstat` -- have been added, some of them
+  have also been backported: this will help kernel developers and users to
+  understand some behaviour like why an expected additional subflow has not been
+  established, without having to instrument the kernel.
+
+- The documentation about MPTCP endpoints configuration has been improved to
+  avoid confusion. These modifications are visible in the IPRoute manual, and on
+  our [website](https://www.mptcp.dev/pm.html).
+
+- The CI now generates code coverage [stats](https://ci-results.mptcp.dev/lcov/)
+  (also published on
+  [Coveralls](https://coveralls.io/github/multipath-tcp/mptcp_net-next)). Code
+  coverage is a valuable piece of information to know how much we can trust a
+  test suite, and easily find out what needs to be improved. A majority of the
+  code is covered (~90%), which is great! There are some areas that can be
+  improved -- e.g.
+  [diag](https://github.com/multipath-tcp/mptcp_net-next/issues/524) and [socket
+  options](https://github.com/multipath-tcp/mptcp_net-next/issues/525) -- but
+  not critical ones. We can also notice many error branches are not covered by
+  the MPTCP test suite: that's because that would be a lot of work to cover most
+  of them while most of the time the action that has to be taken in this case is
+  very simple. That's why we rely on Syzkaller, a fuzzing tool, to cover most of
+  these error branches.
+
+- Still about the CI, the BPF MPTCP selftests are now also executed with a debug
+  kernel config. More analytic tools will cover this area that is growing.
+
+## More apps natively supporting MPTCP
+
+Thanks to the help from [Anthony Doeraene](https://github.com/Aperence/),
+even more [apps](https://www.mptcp.dev/apps.html) are now natively supporting
+MPTCP:
+- [Apache HTTP](https://httpd.apache.org/) ([v2.5.1](https://svn.apache.org/viewvc?view=revision&revision=1920586))
+- [HAProxy](https://www.haproxy.org/) ([v3.1.0](https://git.haproxy.org/?p=haproxy.git;a=commit;h=20efb856e))
+- [VLC in iOS](https://www.videolan.org/vlc/) ([v4.0](https://github.com/videolan/vlc-ios/commit/210c88b3e4))
+- [Firefox in iOS](https://www.mozilla.org/en-US/firefox/browsers/mobile/ios/) ([v132](https://github.com/mozilla-mobile/firefox-ios/pull/21480))
+
+[NGinx](https://github.com/nginx/nginx/pull/130) and
+[FreeNGinx](https://freenginx.org/pipermail/nginx-devel/2024-August/000465.html)
+might support it soon too!
+
+An important change as well is on the Go Language: the next version will have
+MPTCP enabled by default on the server side.
+([src](https://go-review.googlesource.com/c/go/+/607715))
+
+Additionally, Anthony added more languages in the [MPTCP
+Hello](https://github.com/mptcp-apps/mptcp-hello) repository: Elixir, Erlang,
+Swift (macOS), and Objective-C (macOS). Plus a dedicated page about how to use
+MPTCP on [macOS](https://www.mptcp.dev/macOS.html).
+
+Other apps and tools also gained MPTCP support recently:
+
+- [cURL](https://curl.se) ([v8.9.0](https://github.com/curl/curl/pull/13278))
+- [dae](https://github.com/daeuniverse/dae) ([v0.8.0](https://github.com/daeuniverse/dae/pull/601))
+- [lighttpd](https://www.lighttpd.net/) ([v1.4.76](https://github.com/lighttpd/lighttpd1.4/pull/132))
+- [SystemD](https://systemd.io) ([v257](https://github.com/systemd/systemd/pull/32958))
+- [v2ray-core](https://github.com/v2fly/v2ray-core) ([v5.17.0](https://github.com/v2fly/v2ray-core/pull/3109))
+- [ptcpdump](https://github.com/mozillazg/ptcpdump) ([v0.24.0](https://github.com/mozillazg/ptcpdump/pull/152))
+
+OpenWrt v24 will also have MPTCP support available by default!
+([src](https://github.com/openwrt/openwrt/pull/16786))
+
+## Conferences
+
+### Netconf 2024
+
+[Netconf](https://netdev.bots.linux.dev/netconf/) is *a Linux community
+conference, by-invitation-only. The agenda has a clear focus on kernel level
+networking. Attendees are the main maintainers and developers of the Linux
+networking subsystem*.
+
+This year, I was grateful to have been invited to the
+[2024](https://netdev.bots.linux.dev/netconf/2024/index.html) edition in Vienna,
+and I learned a lot. Even if MPTCP has been invoked, I was mostly there to
+discuss [CI aspects](https://netdev.bots.linux.dev/netconf/2024/mattbe.pdf). For
+a while now, there is an MPTCP CI validating patches that are shared on the
+mailing list. It took quite sometime to put that in place, and it regularly
+needs tweaking. There is still some work to do, like having a proper performance
+lab in place which is what I'm currently looking at that. On Netdev side, that's
+only for less than one year the CI is validating functional tests. A good time
+to discuss it, how useful it is, what can be improved, and what is important to
+know about it.
+
+We had very useful
+[discussions](https://netdev.bots.linux.dev/netconf/2024/notes.html) there.
+Amongst the topics that have been discussed around the CI, we have:
+- How important it is to know the code coverage.
+- A container image would be useful to easily reproduce issues locally.
+- A debug kernel config causes a very slow environment, and results in tests to
+  be more unstable, but that can maybe be ignored: what is important here is to
+  look at new kernel warnings found by the debug tools.
+- Other subsystems can re-use code from the MPTCP CI if they want a similar CI
+  setup on their side. Still, it would be good to have an "official" service
+  applying patches in a Git repository to ease the bootstrap of new CIs.
+- Stable kernel are often being validated using the last version of the kernel
+  [selftests](https://docs.kernel.org/dev-tools/kselftest.html). In theory, that
+  makes sense, and looks good to have the biggest coverage and check for
+  regressions, but most network related selftests expect to be executed on the
+  kernel version it is linked to, and then fail if a feature is missing. That's
+  an issue because older stable kernels have a lot of failed tests due to that,
+  and probably nobody is monitoring the different results. Maybe there should be
+  an exception for the network tests, because many tests are looking at the
+  internals like how packets are created, not only at what is exposed to the
+  userspace via the different simple APIs, like the socket one that hides all
+  the complexity to the userspace.
+- Managing the CI takes time, and resources, plus it might be good to have some
+  hardware tests done in the same conditions, from a neutral lab. It might be
+  good to create a dedicated entity to share costs.
+
+### LPC 2024
+
+The [Linux Plumbers Conference](https://lpc.events/) (or LPC) is *the premier
+event for developers working at all levels of the plumbing layer and beyond*.
+
+The [2024 edition](https://lpc.events/event/18/page/224-lpc-2024-overview) was
+also in Vienna, just after Netconf.
+
+There as well, I [talked](https://lpc.events/event/18/contributions/1961/) about
+the CI. The Netdev CI is particular: it runs many different tests, while there
+are many patches regularly posted on the list. That's why patches are validated
+by batches. Due to the complexity -- but also to avoid increasing the traffic on
+the Netdev mailing with people sending patches just to fix unworthy details
+reported by the CI, instead of checking that upfront -- what is being done by
+the CI is supposed to be checked by experienced reviewers and maintainers. It is
+then important to agree on what should be advertised, and what to expect from
+kernel developers, reviewers and maintainers.
+
+(Note that my [presentation](https://lpc.events/event/18/contributions/1961/)
+has been [recorded](https://www.youtube.com/watch?v=ApDDRrrXN9w), but there were
+some issues with the microphone at the beginning, apparently.)
+
+## What's next?
+
+Good news, my work will continue to be supported by the [NGI0
+Core](https://nlnet.nl/core/) fund -- managed by the [NLnet
+Foundation](https://nlnet.nl) (a big thank you :)) -- for another
+[round](https://nlnet.nl/project/MPTCP-deployability-II/). NGI0 Core is made
+possible with [financial support](https://nlnet.nl/core/acknowledgement.pdf)
+from the [European Commission](https://ec.europa.eu/)'s [Next Generation
+Internet](https://ngi.eu/) programme, under the aegis of [DG Communications
+Networks, Content and
+Technology](https://ec.europa.eu/info/departments/communications-networks-content-and-technology_en).
+This project has received funding from the European Union's [Horizon
+Europe](https://ec.europa.eu/programmes/horizoneurope/) research and innovation
+programme under grant agreement No 101092990.
+
+<center>
+  <a href="https://nlnet.nl">
+    <img src="https://nlnet.nl/logo/banner.png" alt="NLnet foundation logo" width="20%" />
+  </a>
+  &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
+  <a href="https://nlnet.nl/core">
+    <img src="https://nlnet.nl/image/logos/NGI0_tag.svg" alt="NGI Zero Logo" width="20%" />
+  </a>
+</center>
+
+This support will help to cover the maintenance, and some new features I will
+hopefully talk about soon!
+
+## Team work
+
+As always, it is important to note that what I presented here so far is mostly
+what I was working on. But I'm not alone in this project. For example, Geliang
+is looking at BPF `iter` for the subflows, and having a path-manage controlled
+with BPF ; Paolo helped fix some issues found by Syzbot, but also by users
+around the path-manager ; Davide switched to a better RST code in case of
+middleboxes interference ; Paolo and Mat helped with the code reviews ;
+Christoph continued the SyzKaller infrastructure maintenance.
+
+A great community!