Search Results: "cts"

8 October 2020

Dirk Eddelbuettel: littler 0.3.12: Exciting updates

max-heap image The thirteenth release of littler as a CRAN package became available today (after a three day rest at CRAN for no real reason), following in the fourteen-ish year history as a package started by Jeff in 2006, and joined by me a few weeks later. littler is the first command-line interface for R as it predates Rscript. It allows for piping as well for shebang scripting via #!, uses command-line arguments more consistently and still starts faster. It also always loaded the methods package which Rscript only started to do in recent years. littler lives on Linux and Unix, has its difficulties on macOS due to yet-another-braindeadedness there (who ever thought case-insensitive filesystems as a default where a good idea?) and simply does not exist on Windows (yet the build system could be extended see RInside for an existence proof, and volunteers are welcome!). See the FAQ vignette on how to add it to your PATH. A few examples are highlighted at the Github repo, as well as in the examples vignette. This release brings five new example scripts and command wrappers: A number of commands were also extended or updated (see below for more). We have a new and very slick documentation website once again utilising Material for MkDocs. Last but not least the two included vignettes now use minidown and the fabulous water css theme which reduced the file sizes of the two vignettes from, respectively, 884kb and 873kb to 47kb and 15kb. Yes, that is correct. That alone brought the package file size down from 641kb to 116kb. Incredible. The NEWS file entry is below.

Changes in littler version 0.3.12 (2020-10-04)
  • Changes in examples
    • Updates to scripts tt.r, cos.r, cow.r, c4r.r, com.r
    • New script installDeps.r to install dependencies
    • Several updates tp script check.r
    • New script installBSPM.r and installRSPM.r for binary package installation (Dirk and I aki in #81)
    • New script cranIncoming.r to check in Incoming
    • New script urlUpdate.r validates URLs as R does
  • Changes in package
    • Travis CI now uses BSPM
    • A package documentation website was added
    • Vignettes now use minidown resulting in much reduced filesizes: from over 800kb to under 50kb (Dirk in #83)

My CRANberries provides a comparison to the previous release. Full details for the littler release are provided as usual at the ChangeLog page, and now also on the new package docs website. The code is available via the GitHub repo, from tarballs and now of course also from its CRAN page and via install.packages("littler"). Binary packages are available directly in Debian as well as soon via Ubuntu binaries at CRAN thanks to the tireless Michael Rutter. Comments and suggestions are welcome at the GitHub repo. If you like this or other open-source work I do, you can now sponsor me at GitHub. For the first year, GitHub will match your contributions.

This post by Dirk Eddelbuettel originated on his Thinking inside the box blog. Please report excessive re-aggregation in third-party for-profit settings.

5 October 2020

Reproducible Builds: Reproducible Builds in September 2020

Welcome to the September 2020 report from the Reproducible Builds project. In our monthly reports, we attempt to summarise the things that we have been up to over the past month, but if you are interested in contributing to the project, please visit our main website. This month, the Reproducible Builds project was pleased to announce a donation from Amateur Radio Digital Communications (ARDC) in support of its goals. ARDC s contribution will propel the Reproducible Builds project s efforts in ensuring the future health, security and sustainability of our increasingly digital society. Amateur Radio Digital Communications (ARDC) is a non-profit which was formed to further research and experimentation with digital communications using radio, with a goal of advancing the state of the art of amateur radio and to educate radio operators in these techniques. You can view the full announcement as well as more information about ARDC on their website.
In August s report, we announced that Jennifer Helsby (redshiftzero) launched a new reproduciblewheels.com website to address the lack of reproducibility of Python wheels . This month, Kushal Das posted a brief follow-up to provide an update on reproducible sources as well. The Threema privacy and security-oriented messaging application announced that within the next months , their apps will become fully open source, supporting reproducible builds :
This is to say that anyone will be able to independently review Threema s security and verify that the published source code corresponds to the downloaded app.
You can view the full announcement on Threema s website.

Events Sadly, due to the unprecedented events in 2020, there will be no in-person Reproducible Builds event this year. However, the Reproducible Builds project intends to resume meeting regularly on IRC, starting on Monday, October 12th at 18:00 UTC (full announcement). The cadence of these meetings will probably be every two weeks, although this will be discussed and decided on at the first meeting. (An editable agenda is available.) On 18th September, Bernhard M. Wiedemann gave a presentation in German titled Wie reproducible builds Software sicherer machen ( How reproducible builds make software more secure ) at the Internet Security Digital Days 2020 conference. (View video.) On Saturday 10th October, Morten Linderud will give a talk at Arch Conf Online 2020 on The State of Reproducible Builds in the Arch Linux distribution:
The previous year has seen great progress in Arch Linux to get reproducible builds in the hands of the users and developers. In this talk we will explore the current tooling that allows users to reproduce packages, the rebuilder software that has been written to check packages and the current issues in this space.
During the Reproducible Builds summit in Marrakesh, GNU Guix, NixOS and Debian were able to produce a bit-for-bit identical binary when building GNU Mes, despite using three different major versions of GCC. Since the summit, additional work resulted in a bit-for-bit identical Mes binary using tcc and this month, a fuller update was posted by the individuals involved.

Development work In openSUSE, Bernhard M. Wiedemann published his monthly Reproducible Builds status update.

Debian Chris Lamb uploaded a number of Debian packages to address reproducibility issues that he had previously provided patches for, including cfingerd (#831021), grap (#870573), splint (#924003) & schroot (#902804) Last month, an issue was identified where a large number of Debian .buildinfo build certificates had been tainted on the official Debian build servers, as these environments had files underneath the /usr/local/sbin directory to prevent the execution of system services during package builds. However, this month, Aurelien Jarno and Wouter Verhelst fixed this issue in varying ways, resulting in a special policy-rcd-declarative-deny-all package. Building on Chris Lamb s previous work on reproducible builds for Debian .ISO images, Roland Clobus announced his work in progress on making the Debian Live images reproducible. [ ] Lucas Nussbaum performed an archive-wide rebuild of packages to test enabling the reproducible=+fixfilepath Debian build flag by default. Enabling the fixfilepath feature will likely fix reproducibility issues in an estimated 500-700 packages. The test revealed only 33 packages (out of 30,000 in the archive) that fail to build with fixfilepath. Many of those will be fixed when the default LLVM/Clang version is upgraded. 79 reviews of Debian packages were added, 23 were updated and 17 were removed this month adding to our knowledge about identified issues. Chris Lamb added and categorised a number of new issue types, including packages that captures their build path via quicktest.h and absolute build directories in documentation generated by Doxygen , etc. Lastly, Lukas Puehringer s uploaded a new version of the in-toto to Debian which was sponsored by Holger Levsen. [ ]

diffoscope diffoscope is our in-depth and content-aware diff utility that can not only locate and diagnose reproducibility issues, it provides human-readable diffs of all kinds too. In September, Chris Lamb made the following changes to diffoscope, including preparing and uploading versions 159 and 160 to Debian:
  • New features:
    • Show ordering differences only in strings(1) output by applying the ordering check to all differences across the codebase. [ ]
  • Bug fixes:
    • Mark some PGP tests that they require pgpdump, and check that the associated binary is actually installed before attempting to run it. (#969753)
    • Don t raise exceptions when cleaning up after guestfs cleanup failure. [ ]
    • Ensure we check FALLBACK_FILE_EXTENSION_SUFFIX, otherwise we run pgpdump against all files that are recognised by file(1) as data. [ ]
  • Codebase improvements:
    • Add some documentation for the EXTERNAL_TOOLS dictionary. [ ]
    • Abstract out a variable we use a couple of times. [ ]
  • diffoscope.org website improvements:
    • Make the (long) demonstration GIF less prominent on the page. [ ]
In addition, Paul Spooren added support for automatically deploying Docker images. [ ]

Website and documentation This month, a number of updates to the main Reproducible Builds website and related documentation. Chris Lamb made the following changes: In addition, Holger Levsen re-added the documentation link to the top-level navigation [ ] and documented that the jekyll-polyglot package is required [ ]. Lastly, diffoscope.org and reproducible-builds.org were transferred to Software Freedom Conservancy. Many thanks to Brett Smith from Conservancy, J r my Bobbio (lunar) and Holger Levsen for their help with transferring and to Mattia Rizzolo for initiating this.

Upstream patches The Reproducible Builds project detects, dissects and attempts to fix as many currently-unreproducible packages as possible. We endeavour to send all of our patches upstream where appropriate. This month, we wrote a large number of these patches, including: Bernhard M. Wiedemann also reported issues in git2-rs, pyftpdlib, python-nbclient, python-pyzmq & python-sidpy.

Testing framework The Reproducible Builds project operates a Jenkins-based testing framework to power tests.reproducible-builds.org. This month, Holger Levsen made the following changes:
  • Debian:
    • Shorten the subject of nodes have gone offline notification emails. [ ]
    • Also track bugs that have been usertagged with usrmerge. [ ]
    • Drop abort-related codepaths as that functionality has been removed from Jenkins. [ ]
    • Update the frequency we update base images and status pages. [ ][ ][ ][ ]
  • Status summary view page:
    • Add support for monitoring systemctl status [ ] and the number of diffoscope processes [ ].
    • Show the total number of nodes [ ] and colourise critical disk space situations [ ].
    • Improve the visuals with respect to vertical space. [ ][ ]
  • Debian rebuilder prototype:
    • Resume building random packages again [ ] and update the frequency that packages are rebuilt. [ ][ ]
    • Use --no-respect-build-path parameter until sbuild 0.81 is available. [ ]
    • Treat the inability to locate some packages as a debrebuild problem, and not as a issue with the rebuilder itself. [ ]
  • Arch Linux:
    • Update various components to be compatible with Arch Linux s move to the xz compression format. [ ][ ][ ]
    • Allow scheduling of old packages to catch up on the backlog. [ ][ ][ ]
    • Improve formatting on the summary page. [ ][ ]
    • Update HTML pages once every hour, not every 30 minutes. [ ]
    • Use the Ubuntu (!) GPG keyserver to validate packages. [ ]
  • System health checks:
    • Highlight important bad conditions in colour. [ ][ ]
    • Add support for detecting more problems, including Jenkins shutdown issues [ ], failure to upgrade Arch Linux packages [ ], kernels with wrong permissions [ ], etc.
  • Misc:
    • Delete old schroot sessions after 2 days, not 3. [ ]
    • Use sudo to cleanup diffoscope schroot sessions. [ ]
In addition, stefan0xC fixed a query for unknown results in the handling of Arch Linux packages [ ] and Mattia Rizzolo updated the template that notifies maintainers by email of their newly-unreproducible packages to ensure that it did not get caught in junk/spam folders [ ]. Finally, build node maintenance was performed by Holger Levsen [ ][ ][ ][ ], Mattia Rizzolo [ ][ ] and Vagrant Cascadian [ ][ ][ ].
If you are interested in contributing to the Reproducible Builds project, please visit our Contribute page on our website. However, you can get in touch with us via:

3 October 2020

Ritesh Raj Sarraf: First Telescope

Curiosity I guess this would be common to most of us. While I grew up, right from the childhood itself, the sky was always an intriguing view. The Stars, the Moon, the Eclipses; were all fascinating. As a child, in my region, religion and culture; the mythology also built up stories around it. Lunar Eclipses have a story of its own. During Solar Eclipses, parents still insist that we do not go out. And to be done with the food eating before/after the eclipse. Then there s the Hindu Astrology part, which claims its own theories and drags in mythology along. For example, you ll still find the Hindu Astrology making recommendations to follow certain practices with the planets, to get auspicious personal results. As far as I know, other religions too have similar beliefs about the planets. As a child, we are told the Moon to be addressed as an Uncle ( ). There s also a rhyme around it, that many of us must have heard. And if you look at our god, Lord Mahadev, he s got a crescent on his head
Lord Mahadev
Lord Mahadev

Reality Fast-forward to today, as I grew, so did some of my understanding. It is fascinating how mankind has achieved so much understanding of our surrounding. You could go through the documentaries on Mars Exploration, for example; to see how the rovers are providing invaluable data. As a mere individual, there s a limit to what one can achieve. But the questions flow in free.
  • Is there life beyond us
  • What s out there in the sky
  • Why is all this the way it is

Hobby The very first step, for me, for every such curiosity, has been to do the ground work, with the resources I have. To study on the subject. I have done this all my life. For example, I started into the Software domain as: A curiosity => A Hobby => A profession Same was the case with some of the other hobbies, equally difficult as Astronomy, that I developed a liking for. Just did the ground work, studied on those topics and then applied the knowledge to further improve it and build up some experience. And star gazing came in no different. As a complete noob, had to start with the A B C on the subject of Astronomy. Familiarize myself with the usual terms. As so on PS: Do keep in mind that not all hobbies have a successful end. For example, I always craved to be good with graphic designing, image processing and the likes, where I ve always failed. Never was able to keep myself motivated enough. Similar was my experience when trying to learn playing a musical instrument. Just didn t work out for me, then. There s also a phase in it, where you fail and then learn from the failures and proceed further, and then eventually succeed. But we all like to talk about the successes. :-)

Astronomy So far, my impression has been that this topic/domain will not suit most of the people. While the initial attraction may be strong, given the complexity and perseverance that Astronomy requires, most people would lose interest in it very soon. Then there s the realization factor. If one goes with an expectation to get quick results, they may get disappointed. It isn t like a point and shoot device that d give you results on the spot. There s also the expectation side of things. If you are a person more accustomed to taking pretty selfies, which always come right because the phone manufacturer does heavy processing on the images to ensure that you get to see the pretty fake self, for the most of the times; then star gazing with telescopes could be a frustrating experience altogether. What you get to see in the images on the internet will be very different than what you d be able to see with your eyes and your basic telescope. There s also the cost aspect. The more powerful (and expensive) your telescope, the better your view. And all things aside, it still may get you lose interest, after you ve done all the ground work and spent a good chunk of money on it. Simply because the object you are gazing at is more a still image, which can quickly get boring for many. On the other hand, if none of the things obstruct, then the domain of Astronomy can be quite fascinating. It is a continuous learning domain (reminds me of CI in our software field these days). It is just the beginning for us here, and we hope to have a lasting experience in it.

The Internet I have been indebted to the internet right from the beginning. The internet is what helped me be able to achieve all I wanted. It is one field with no boundaries. If there is a will, there is a way; and often times, the internet is the way.
  • I learnt computers over the internet.
  • Learnt more about gardening and plants over the internet
  • Learnt more about fish care-taking over the internet
And many many more things. Some of the communities over the internet are a great way to participation. They bridge the age gap, the regional gap and many more. For my Astronomy need, I was glad to see so many active communities, with great participants, on the internet.

Telescope While there are multiple options to start star gazing, I chose to start with a telescope. But as someone completely new to this domain, there was a long way to go. And to add to that, the real life: work + family I spent a good 12+ months reading up on the different types of telescopes, what they are, their differences, their costs, their practical availability etc. The good thing is that the market has offerings for everything. From a very basic binocular to a fully automatic Maksutov-Cassegrain scope. It all would depend on your budget.

Automatic vs Manual To make it easy for the users, the market has multiple options in the offering. One could opt-in for a cheap, basic and manually operated telescope; which would require the user to do a lot of ground study. On the other hand, users also have the option of automatic telescopes which do the hard work of locating and tracking the planetary objects. Either option aside, the end result of how much you ll be able to observe the sky, still depends on many many more factors: Enthusiasm over time, Light Pollution, Clear Skies, Timing etc. PS: The planetary objects move at a steady pace. Objects you lock into your view now will be gone out of the FOV in just a matter of minutes.

My Telescope After spending so much of the time reading up on types of telescopes, my conclusion was that a scope with high aperture and focal length was the way to go forward. This made me shorten the list to Dobsonians. But the Dobsonians aren t a very cheap telescope, whether manual or automatic. My final decision made me acquire a 6" Dobsonian Telescope. It is a Newtonian Reflecting Telescope with a 1200mm focal length and 150mm diameter. Another thing about this subject is that most of the stuff you do in Astronomy; right from the telescope selection, to installation, to star gazing; most of it is DIY, so your mileage may vary with the end result and experience. For me, installation wasn t very difficult. I was able to assemble the base Dobsonian mount and the scope in around 2 hours. But the installation manual, I had been provided with, was very brief. I ended up with one module in the mount wrongly fit, which I was able to fix later, with the help of online forums.
Dobsonian Mount
Dobsonian Mount
In this image you can see that the side facing out, where the handle will go, is wrong. If fit this way, the handle will not withstand any weight at all.
Correct Panel Side
Correct Panel Side
The right fix of the handle base board. In this image, the handle is on the other side that I m holding. Because the initial fit put in some damage to the engineered wood, I fixed it up by sealing with some adhesive. With that, this is what my final telescope looks like.
Final Telescope
Final Telescope

Clear Skies While the telescope was ready, the skies were not. For almost next 10 days, we had no clear skies at all. All I could do was wait. Wait so much that I had forgotten to check on the skies. Luckily, my wife noticed clear skies this week for a single day. Clear enough that we could try out our telescope for the very first time.
Me posing for a shot
Me posing for a shot

Telescope As I said earlier, in my opinion, it takes a lot of patience and perseverance on this subject. And most of the things here are DIY. To start with, we targeted the Moon. Because it is easy. I pointed the scope to the moon, then looked into the finder scope to center it, and then looked through the eyepiece. And blank. Nothing out there. Turns out, the finder scope and the viewer s angle weren t aligned. This is common and the first DIY step, when you plan to use your telescope for viewing. Since our first attempt was unplanned and just random because we luckily spotted that the skies were clear, we weren t prepared for this. Lucky enough, mapping the difference in the alignment, in the head, is not very difficult. After a couple of minutes, I could make out the point in the finder scope, where the object if projected, would show proper in the viewer. With that done, it was just mesmerizing to see the Moon, in a bit more detail, than what I ve seen all these years of my life.
Moon
Moon
Moon
Moon
Moon
Moon
Moon
Moon
The images are not exactly what we saw with our eyes. The view was much more vivid than these pictures. But as a first timer, I really wanted to capture this first moment of a closer view of the Moon. In the whole process; that of ground work studying about telescopes, installation of the telescope, astronomy basics and many other things; the most difficult part in this entire journey, was to point my phone to the viewing eyepiece, to get a shot of the object. This requirement just introduced me to astrophotography. And then, Dobsonians aren t the best model for astrophotography, to what I ve learnt so far. Hopefully, I ll find my ways to do some DIY astrophotography with the tools I have. Or extend my arsenal over time. But overall, we ve been very pleased with the subject of Astronomy. It is a different feel altogether and we re glad to have forayed into it.

2 October 2020

Ian Jackson: Mailman vs DKIM - a novel solution

tl;dr: Do not configure Mailman to replace the mail domains in From: headers. Instead, try out my small new program which can make your Mailman transparent, so that DKIM signatures survive. Background and narrative DKIM NB: This explanation is going to be somewhat simplified. I am going to gloss over some details and make some slightly approximate statements. DKIM is a new anti-spoofing mechanism for Internet email, intended to help fight spam. DKIM, paired with the DMARC policy system, has been remarkably successful at stemming the flood of joe-job spams. As usually deployed, DKIM works like this: When a message is originally sent, the author's MUA sends it to the MTA for their From: domain for outward delivery. The From: domain mailserver calculates a cryptographic signature of the message, and puts the signature in the headers of the message. Obviously not the whole message can be signed, since at the very least additional headers need to be added in transit, and sometimes headers need to be modified too. The signing MTA gets to decide what parts of the message are covered by the signature: they nominate the header fields that are covered by the signature, and specify how to handle the body. A recipient MTA looks up the public key for the From: domain in the DNS, and checks the signature. If the signature doesn't match, depending on policy (originator's policy, in the DNS, and recipient's policy of course), typically the message will be treated as spam. The originating site has a lot of control over what happens in practice. They get to publish a formal (DMARC) policy in the DNS which advises recipients what they should do with mails claiming to be from their site. As mentioned, they can say which headers are covered by the signature - including the ability to sign the absence of a particular headers - so they can control which headers downstreams can get away with adding or modifying. And they can set a normalisation policy, which controls how precisely the message must match the one that they sent. Mailman Mailman is, of course, the extremely popular mailing list manager. There are a lot of things to like about it. I choose to run it myself not just because it's popular but also because it provides a relatively competent web UI and a relatively competent email (un)subscription interfaces, decent bounce handling, and a pretty good set of moderation and posting access controls. The Xen Project mailing lists also run on mailman. Recently we had some difficulties with messages sent by Citrix staff (including myself), to Xen mailing lists, being treated as spam. Recipient mail systems were saying the DKIM signatures were invalid. This was in fact true. Citrix has chosen a fairly strict DKIM policy; in particular, they have chosen "simple" normalisation - meaning that signed message headers must precisely match in syntax as well as in a semantic sense. Examining the the failing-DKIM messages showed that this was definitely a factor. Applying my Opinions about email My Bayesian priors tend to suggest that a mail problem involving corporate email is the fault of the corporate email. However in this case that doesn't seem true to me. My starting point is that I think mail systems should not not modify messages unnecessarily. None of the DKIM-breaking modifications made by Mailman seemed necessary to me. I have on previous occasions gone to corporate IT and requested quite firmly that things I felt were broken should be changed. But it seemed wrong to go to corporate IT and ask them to change their published DKIM/DMARC policy to accomodate a behaviour in Mailman which I didn't agree with myself. I felt that instead I shoud put (with my Xen Project hat on) my own house in order. Getting Mailman not to modify messages So, I needed our Mailman to stop modifying the headers. I needed it to not even reformat them. A brief look at the source code to Mailman showed that this was not going to be so easy. Mailman has a lot of features whose very purpose is to modify messages. Personally, as I say, I don't much like these features. I think the subject line tags, CC list manipulations, and so on, are a nuisance and not really Proper. But they are definitely part of why Mailman has become so popular and I can definitely see why the Mailman authors have done things this way. But these features mean Mailman has to disassemble incoming messages, and then reassemble them again on output. It is very difficult to do that and still faithfully reassemble the original headers byte-for-byte in the case where nothing actually wanted to modify them. There are existing bug reports[1] [2] [3] [4]; I can see why they are still open. Rejected approach: From:-mangling This situation is hardly unique to the Xen lists. Many other have struggled with it. The best that seems to have been come up with so far is to turn on a new Mailman feature which rewrites the From: header of the messages that go through it, to contain the list's domain name instead of the originator's. I think this is really pretty nasty. It breaks normal use of email, such as reply-to-author. It is having Mailman do additional mangling of the message in order to solve the problems caused by other undesirable manglings! Solution! As you can see, I asked myself: I want Mailman not modify messages at all; how can I get it to do that? Given the existing structure of Mailman - with a lot of message-modifying functionality - that would really mean adding a bypass mode. It would have to spot, presumably depending on config settings, that messages were not to be edited; and then, it would avoid disassembling and reassembling the message at at all, and bypass the message modification stages. The message would still have to be parsed of course - it's just that the copy send out ought to be pretty much the incoming message. When I put it to myself like that I had a thought: couldn't I implement this outside Mailman? What if I took a copy of every incoming message, and then post-process Mailman's output to restore the original? It turns out that this is quite easy and works rather well! outflank-mailman outflank-mailman is a 233-line script, plus documentation, installation instructions, etc. It is designed to run from your MTA, on all messages going into, and coming from, Mailman. On input, it saves a copy of the message in a sqlite database, and leaves a note in a new Outflank-Mailman-Id header. On output, it does some checks, finds the original message, and then combines the original incoming message with carefully-selected headers from the version that Mailman decided should be sent. This was deployed for the Xen Project lists on Tuesday morning and it seems to be working well so far. If you administer Mailman lists, and fancy some new software to address this problem, please do try it out. Matters arising - Mail filtering, DKIM Overall I think DKIM is a helpful contribution to the fight against spam (unlike SPF, which is fundamentally misdirected and also broken). Spam is an extremely serious problem; most receiving mail servers experience more attempts to deliver spam than real mail, by orders of magnitude. But DKIM is not without downsides. Inherent in the design of anything like DKIM is that arbitrary modification of messages by list servers is no longer possible. In principle it might be possible to design a system which tolerated modifications reasonable for mailing lists but it would be quite complicated and have to somehow not tolerate similar modifications in other contexts. So DKIM means that lists can no longer add those unsubscribe footers to mailing list messages. The "new way" (RFC2369, July 1998), to do this is with the List-Unsubscribe header. Hopefully a good MUA will be able to deal with unsubscription semiautomatically, and I think by now an adequate MUA should at least display these headers by default. Sender: There are implications for recipient-side filtering too. The "traditional" correct way to spot mailing list mail was to look for Resent-To:, which can be added without breaking DKIM; the "new" (RFC2919, March 2001) correct way is List-Id:, likewise fine. But during the initial deployment of outflank-mailman I discovered that many subscribers were detecting that a message was list traffic by looking at the Sender: header. I'm told that some mail systems (apparently Microsoft's included) make it inconvenient to filter on List-Id. Really, I think a mailing list ought not to be modifying Sender:. Given Sender:'s original definition and semantics, there might well be reasonable reasons for a mailing list posting to have different From: and and then the original Sender: ought not to be lost. And a mailing list's operation does not fit well into the original definition of Sender:. I suspect that list software likes to put in Sender mostly for historical reasons; notably, a long time ago it was not uncommon for broken mail systems to send bounces to the Sender: header rather than the envelope sender (SMTP MAIL FROM). DKIM makes this more of a problem. Unfortunately the DKIM specifications are vague about what headers one should sign, but they pretty much definitely include Sender: if it is present, and some materials encourage signing the absence of Sender:. The latter is Exim's default configuration when DKIM-signing is enabled. Franky there seems little excuse for systems to not readily support and encourage filtering on List-Id, 20 years later, but I don't want to make life hard for my users. For now we are running a compromise configuration: if there wasn't a Sender: in the original, take Mailman's added one. This will result in (i) misfiltering for some messages whose poster put in a Sender:, and (ii) DKIM failures for messages whose originating system signed the absence of a Sender:. I'm going to mine the db for some stats after it's been deployed for a week or so, to see which of these problems is worst and decide what to do about it. Mail routing For DKIM to work, messages being sent From: a particular mail domain must go through a system trusted by that domain, so they can be signed. Most users tend to do this anyway: their mail provider gives them an IMAP server and an authenticated SMTP submission server, and they configure those details in their MUA. The MUA has a notion of "accounts" and according to the user's selection for an outgoing message, connects to the authenticated submission service (usually using TLS over the global internet). Trad unix systems where messages are sent using the local sendmail or localhost SMTP submission (perhaps by automated systems, or perhaps by human users) are fine too. The smarthost can do the DKIM signing. But this solution is awkward for a user of a trad MUA in what I'll call "alias account" setups: where a user has an address at a mail domain belonging to different people to the system on which they run their MUA (perhaps even several such aliases for different hats). Traditionally this worked by the mail domain forwarding incoming the mail, and the user simply self-declaring their identity at the alias domain. Without DKIM there is nothing stopping anyone self-declaring their own From: line. If DKIM is to be enabled for such a user (preventing people forging mail as that user), the user will have to somehow arrange that their trad unix MUA's outbound mail stream goes via their mail alias provider. For a single-user sending unix system this can be done with tolerably complex configuration in an MTA like Exim. For shared systems this gets more awkward and might require some hairy shell scripting etc.
edited 2020-10-01 21:22 and 21:35 and -02 10:50 +0100 to fix typos and 21:28 to linkify "my small program" in the tl;dr


comment count unavailable comments

30 September 2020

Utkarsh Gupta: FOSS Activites in September 2020

Here s my (twelfth) monthly update about the activities I ve done in the F/L/OSS world.

Debian
This was my 21st month of contributing to Debian. I became a DM in late March last year and a DD last Christmas! \o/ I ve been busy with my undergraduation stuff but I still squeezed out some time for the regular Debian work. Here are the following things I did in Debian this month:

Uploads and bug fixes:

Other $things:
  • Attended the Debian Ruby team meeting. Logs here.
  • Mentoring for newcomers.
  • FTP Trainee reviewing.
  • Moderation of -project mailing list.
  • Sponsored trace-cmd for Sudip, ruby-asset-sync for Nilesh, and mariadb-mysql-kbs for William.

RuboCop::Packaging - Helping the Debian Ruby team! \o/ This Google Summer of Code, I worked on writing a linter that could flag offenses for lines of code that are very troublesome for Debian maintainers while trying to package and maintain Ruby libraries and applications! Whilst the GSoC period is over, I ve been working on improving that tool and have extended that linter to now auto-correct these offenses by itself! \o/
You can now just use the -A flag and you re done! Boom! The ultimate game-changer! Here s a quick demo for this feature: A few quick updates on RuboCop::Packaging: I ve also spent a considerable amount of time in raising awareness about this and in more general sense, about downstream maintenance.
As a result, I raised a bunch of PRs which got really good response. I got all of the 20 PRs merged upstream, fixing these issues.

Debian (E)LTS
Debian Long Term Support (LTS) is a project to extend the lifetime of all Debian stable releases to (at least) 5 years. Debian LTS is not handled by the Debian security team, but by a separate group of volunteers and companies interested in making it a success. And Debian Extended LTS (ELTS) is its sister project, extending support to the Jessie release (+2 years after LTS support). This was my twelfth month as a Debian LTS and third month as a Debian ELTS paid contributor.
I was assigned 19.75 hours for LTS and 15.00 hours for ELTS and worked on the following things:
(for LTS, I over-worked for 11 hours last month on the survey so only had 8.75 hours this month!)

LTS CVE Fixes and Announcements:

ELTS CVE Fixes and Announcements:
  • Issued ELA 274-1, fixing CVE-2020-11984, for uwsgi.
    For Debian 8 Jessie, these problems have been fixed in version 2.0.7-1+deb8u3.
  • Issued ELA 275-1, fixing CVE-2020-14363, for libx11.
    For Debian 8 Jessie, these problems have been fixed in version 2:1.6.2-3+deb8u4.
  • Issued ELA 278-1, fixing CVE-2020-8184, for ruby-rack.
    For Debian 8 Jessie, these problems have been fixed in version 1.5.2-3+deb8u4.
  • Also worked on updating the version of clamAV from v0.101.5 to v0.102.4.
    This was a bit tricky package to work on since it involved an ABI/API change and was more or less a transition. Super thanks to Emilio for his invaluable help and him taking over the package, finishing, and uploading it in the end.

Other (E)LTS Work:
  • Front-desk duty from 31-08 to 06-09 and from 28-09 onward for both LTS and ELTS.
  • Triaged apache2, cryptsetup, nasm, node-bl, plinth, qemu, rsync, ruby-doorkeeper, and uwsgi.
  • Marked CVE-2020-15094/symfony as not-affected for Stretch.
  • Marked CVE-2020- 9490,11993 /apache2 as ignored for Stretch.
  • Marked CVE-2020-8244/node-bl as no-dsa for Stretch.
  • Marked CVE-2020-24978/nasm as no-dsa for Stretch.
  • Marked CVE-2020-25073/plinth as no-dsa for Stretch.
  • Marked CVE-2020-15094/symfony as not-affected for Jessie.
  • Marked CVE-2020-14382/cryptsetup as not-affected for Jessie.
  • Marked CVE-2020-14387/rsync as not-affected for Jessie.
  • Auto EOL ed ark, collabtive, linux, nasm, node-bl, and thunderbird for Jessie.
  • Use mktemp instead of tempfile in bin/auto-add-end-of-life.sh.
  • Attended the fifth LTS meeting. Logs here.
  • General discussion on LTS private and public mailing list.

Until next time.
:wq for today.

Antoine Beaupr : Presentation tools

I keep forgetting how to make presentations. I had a list of tools in a wiki from a previous job, but that's now private and I don't see why I shouldn't share this (even if for myself!). So here it is. What's your favorite presentation tool?

Tips
  • if you have some text to present, outline keywords so that you can present your subject without reading every word
  • ideally, don't read from your slides - they are there to help people follow, not for people to read
  • even better: make your slides pretty with only a few words, or don't make slides at all
Further advice: I'm currently using Pandoc with PDF input (with a trip through LaTeX) for most slides, because PDFs are more reliable and portable than web pages. I've also used Libreoffice, Pinpoint, and S5 (through RST) in the past. I miss Pinpoint, too bad that it died. Some of my presentations are available in my GitLab.com account: See also my list of talks and presentations which I can't seem to keep up to date.

Tools

Beamer (LaTeX)
  • LaTeX class
  • Do not use directly unless you are a LaTeX expert or masochist, see Pandoc below
  • see also powerdot
  • Home page

Darkslide
  • HTML, Javascript
  • presenter notes, table of contents, Markdown, RST, Textile, themes, code samples, auto-reload
  • Home page, demo

Impress.js

Impressive
  • simply displays PDFs or images
  • page transitions, overview screen, highlighting
  • Home page

Libreoffice Impress
  • Powerpoint clone
  • Makes my life miserable
  • PDF export, presenter notes, outline view, etc
  • Home page, screenshots

Magicpoint
  • ancestor of everyone else (1997!)
  • text input format, image support, talk timer, slide guides, HTML/Postscript export, draw on slides, X11 output
  • no release since 2008
  • Home page

mdp and lookatme (commandline)

Pandoc
  • Allows converting from basically whatever into slides, including Beamer, DZSlides, reveal.js, slideous, slidy, Powerpoint
  • PDF, HTML, Powerpoint export, presentation notes, full screen background images
  • nice plain text or markdown input format
  • Home page, documentation

PDF Presenter
  • PDF presentation tool, shows presentation notes
  • basically "Keynote for Linux"
  • Home page, pdf-presenter-console in Debian

Pinpoint
  • Native GNOME app
  • Full screen slides, PDF export, live change, presenter notes, pango markup, video, image backgrounds
  • Home page
  • Abandoned since at least 2019

Reveal.js
  • HTML, Javascript
  • PDF export, Markdown, LaTeX support, syntax-highlighting, nested slides, speaker notes
  • Source code, demo

S5
  • HTML, CSS
  • incremental, bookmarks, keyboard controls
  • can be transformed from ReStructuredText (RST) with rst2s5 with python-docutils
  • Home page, demo

sent
  • X11 only
  • plain text, black on white, image support, and that's it
  • from the suckless.org elitists
  • Home page

Sozi
  • Entire presentation is one poster, zooming and jumping around
  • SVG + Javascript
  • Home page, demo

Other options Another option I have seriously considered is just generate a series of images with good resolution, hopefully matching the resolution (or at least aspect ratio) of the output device. Then you flip through a series of images one by one. In that case, any of those image viewers (not an exhaustive list) would work: Update: it turns out I already wrote a somewhat similar thing when I did a recent presentation. If you're into rants, you might enjoy the README file accompanying the Kubecon rant presentation. TL;DR: "makes me want to scream" and "yet another unsolved problem space, sigh" (refering to "display images full-screen" specifically).

Bastian Blank: Booting Debian on ThinkPad X13 AMD

Running new hardware is always fun. The problems are endless. The solutions not so much. So I've got a brand new ThinkPad X13 AMD. It features an AMD Ryzen 5 PRO 4650U, 16GB of RAM and a 256GB NVME SSD. The internal type identifier is 20UF. It runs the latest firmware as of today with version 1.09. So far I found two problems with it: Disable Secure Boot The system silently fails to boot a signed shim and grub from an USB thumb drive. I used on of the Debian Cloud images, which should properly work in this setup and do on my other systems. The only fix I found was to disable Secure Boot alltogether. Select Linux in firmware Running a Linux 5.8 with default firmware setting produces ACPI errors on each key press.
ACPI BIOS Error (bug): Could not resolve symbol [\_SB.PCI0.GPP3], AE_NOT_FOUND (20200528/psargs-330)
ACPI Error: Aborting method \_SB.GPIO._EVT due to previous error (AE_NOT_FOUND) (20200528/psparse-529)
This can be "fixed" by setting a strategic setting inside the firmware:
Config > Power > Sleep State to Linux

Chris Lamb: Free software activities in September 2020

Here is my monthly update covering what I have been doing in the free software world during September 2020 (previous month):

Reproducible Builds One of the original promises of open source software is that distributed peer review and transparency of process results in enhanced end-user security. However, whilst anyone may inspect the source code of free and open source software for malicious flaws, almost all software today is distributed as pre-compiled binaries. This allows nefarious third-parties to compromise systems by injecting malicious code into ostensibly secure software during the various compilation and distribution processes. The motivation behind the Reproducible Builds effort is to ensure no flaws have been introduced during this compilation process by promising identical results are always generated from a given source, thus allowing multiple third-parties to come to a consensus on whether a build was compromised. The project is proud to be a member project of the Software Freedom Conservancy. Conservancy acts as a corporate umbrella allowing projects to operate as non-profit initiatives without managing their own corporate structure. If you like the work of the Conservancy or the Reproducible Builds project, please consider becoming an official supporter. This month, I:

diffoscope I made the following changes to diffoscope, including preparing and uploading versions 159 and 160 to Debian:

Debian Lintian For Lintian, the static analysis tool for Debian packages, I uploaded versions 2.93.0, 2.94.0, 2.95.0 & 2.96.0 (not counting uploads to the backports repositories), as well as: Debian LTS This month I've worked 18 hours on Debian Long Term Support (LTS) and 12 hours on its sister Extended LTS project. You can find out more about the project via the following video:
Uploads Bugs filed

29 September 2020

Mike Gabriel: UBports: Packaging of Lomiri Operating Environment for Debian (part 03)

Before and during FOSDEM 2020, I agreed with the people (developers, supporters, managers) of the UBports Foundation to package the Unity8 Operating Environment for Debian. Since 27th Feb 2020, Unity8 has now become Lomiri. Recent Uploads to Debian related to Lomiri Over the past 4 months I worked on the following bits and pieces regarding Lomiri in Debian: The next two big projects / packages ahead are lomiri-ui-toolkit and qtmir. Credits Many big thanks go to Marius and Dalton for their work on the UBports project and being always available for questions, feedback, etc. Thanks to Ratchanan Srirattanamet for providing some of his time for debugging some non-thread safe unit tests (currently unsure, what package we actually looked at...). Thanks for Florian Leeber for being my point of contact for topcis regarding my cooperation with the UBports Foundation. Previous Posts about my Debian UBports Team Efforts

Vincent Bernat: Speeding up bgpq4 with IRRd in a container

When building route filters with bgpq4 or bgpq3, the speed of rr.ntt.net or whois.radb.net can be a bottleneck. Updating many filters may take several tens of minutes, depending on the load:
$ time bgpq4 -h whois.radb.net AS-HURRICANE   wc -l
909869
1.96s user 0.15s system 2% cpu 1:17.64 total
$ time bgpq4 -h rr.ntt.net AS-HURRICANE   wc -l
927865
1.86s user 0.08s system 12% cpu 14.098 total
A possible solution is to run your own IRRd instance in your network, mirroring the main routing registries. A close alternative is to bundle IRRd with all the data in a ready-to-use Docker image. This also has the advantage of easy integration into a Docker-based CI/CD pipeline.
$ git clone https://github.com/vincentbernat/irrd-legacy.git -b blade/master
$ cd irrd-legacy
$ docker build . -t irrd-snapshot:latest
[ ]
Successfully built 58c3e83a1d18
Successfully tagged irrd-snapshot:latest
$ docker container run --rm --detach --publish=43:43 irrd-snapshot
4879cfe7413075a0c217089dcac91ed356424c6b88808d8fcb01dc00eafcc8c7
$ time bgpq4 -h localhost AS-HURRICANE   wc -l
904137
1.72s user 0.11s system 96% cpu 1.881 total
The Dockerfile contains three stages:
  1. building IRRd,1
  2. retrieving various IRR databases, and
  3. assembling the final container with the result of the two previous stages.
The second stage fetches the databases used by rr.ntt.net: NTTCOM, RADB, RIPE, ALTDB, BELL, LEVEL3, RGNET, APNIC, JPIRR, ARIN, BBOI, TC, AFRINIC, ARIN-WHOIS, and REGISTROBR. However, it misses RPKI.2 Feel free to adapt! The image can be scheduled to be rebuilt daily or weekly, depending on your needs. The repository includes a .gitlab-ci.yaml file automating the build and triggering the compilation of all filters by your CI/CD upon success.

  1. Instead of using the latest version of IRRd, the image relies on an older version that does not require a PostgreSQL instance and uses flat files instead.
  2. Unlike the others, the RPKI database is built from the published RPKI ROAs. They can be retrieved with rpki-client and transformed into RPSL objects to be imported in IRRd.

28 September 2020

Vincent Bernat: Syncing RIPE, ARIN and APNIC objects with a custom Ansible module

Internet is split into five regional Internet registry: AFRINIC, ARIN, APNIC, LACNIC and RIPE. Each RIR maintains an Internet Routing Registry. An IRR allows one to publish information about the routing of Internet number resources.1 Operators use this to determine the owner of an IP address and to construct and maintain routing filters. To ensure your routes are widely accepted, it is important to keep the prefixes you announce up-to-date in an IRR. There are two common tools to query this database: whois and bgpq4. The first one allows you to do a query with the WHOIS protocol:
$ whois -BrG 2a0a:e805:400::/40
[ ]
inet6num:       2a0a:e805:400::/40
netname:        FR-BLADE-CUSTOMERS-DE
country:        DE
geoloc:         50.1109 8.6821
admin-c:        BN2763-RIPE
tech-c:         BN2763-RIPE
status:         ASSIGNED
mnt-by:         fr-blade-1-mnt
remarks:        synced with cmdb
created:        2020-05-19T08:04:58Z
last-modified:  2020-05-19T08:04:58Z
source:         RIPE
route6:         2a0a:e805:400::/40
descr:          Blade IPv6 - AMS1
origin:         AS64476
mnt-by:         fr-blade-1-mnt
remarks:        synced with cmdb
created:        2019-10-01T08:19:34Z
last-modified:  2020-05-19T08:05:00Z
source:         RIPE
The second one allows you to build route filters using the information contained in the IRR database:
$ bgpq4 -6 -S RIPE -b AS64476
NN = [
    2a0a:e805::/40,
    2a0a:e805:100::/40,
    2a0a:e805:300::/40,
    2a0a:e805:400::/40,
    2a0a:e805:500::/40
];
There is no module available on Ansible Galaxy to manage these objects. Each IRR has different ways of being updated. Some RIRs propose an API but some don t. If we restrict ourselves to RIPE, ARIN and APNIC, the only common method to update objects is email updates, authenticated with a password or a GPG signature.2 Let s write a custom Ansible module for this purpose!

Notice I recommend that you read Writing a custom Ansible module as an introduction, as well as Syncing MySQL tables for a more instructive example.

Code The module takes a list of RPSL objects to synchronize and returns the body of an email update if a change is needed:
- name: prepare RIPE objects
  irr_sync:
    irr: RIPE
    mntner: fr-blade-1-mnt
    source: whois-ripe.txt
  register: irr

Prerequisites The source file should be a set of objects to sync using the RPSL language. This would be the same content you would send manually by email. All objects should be managed by the same maintainer, which is also provided as a parameter. Signing and sending the result is not the responsibility of this module. You need two additional tasks for this purpose:
- name: sign RIPE objects
  shell:
    cmd: gpg --batch --user noc@example.com --clearsign
    stdin: "  irr.objects  "
  register: signed
  check_mode: false
  changed_when: false
- name: update RIPE objects by email
  mail:
    subject: "NEW: update for RIPE"
    from: noc@example.com
    to: "auto-dbm@ripe.net"
    cc: noc@example.com
    host: smtp.example.com
    port: 25
    charset: us-ascii
    body: "  signed.stdout  "
You also need to authorize the PGP keys used to sign the updates by creating a key-cert object and adding it as a valid authentication method for the corresponding mntner object:
key-cert:  PGPKEY-A791AAAB
certif:    -----BEGIN PGP PUBLIC KEY BLOCK-----
certif:    
certif:    mQGNBF8TLY8BDADEwP3a6/vRhEERBIaPUAFnr23zKCNt5YhWRZyt50mKq1RmQBBY
[ ]
certif:    -----END PGP PUBLIC KEY BLOCK-----
mnt-by:    fr-blade-1-mnt
source:    RIPE
mntner:    fr-blade-1-mnt
[ ]
auth:      PGPKEY-A791AAAB
mnt-by:    fr-blade-1-mnt
source:    RIPE

Module definition Starting from the skeleton described in the previous article, we define the module:
module_args = dict(
    irr=dict(type='str', required=True),
    mntner=dict(type='str', required=True),
    source=dict(type='path', required=True),
)
result = dict(
    changed=False,
)
module = AnsibleModule(
    argument_spec=module_args,
    supports_check_mode=True
)

Getting existing objects To grab existing objects, we use the whois command to retrieve all the objects from the provided maintainer.
# Per-IRR variations:
# - whois server
whois =  
    'ARIN': 'rr.arin.net',
    'RIPE': 'whois.ripe.net',
    'APNIC': 'whois.apnic.net'
 
# - whois options
options =  
    'ARIN': ['-r'],
    'RIPE': ['-BrG'],
    'APNIC': ['-BrG']
 
# - objects excluded from synchronization
excluded = ["domain"]
if irr == "ARIN":
    # ARIN does not return these objects
    excluded.extend([
        "key-cert",
        "mntner",
    ])
# Grab existing objects
args = ["-h", whois[irr],
        "-s", irr,
        *options[irr],
        "-i", "mnt-by",
        module.params['mntner']]
proc = subprocess.run("whois", *args, capture_output=True)
if proc.returncode != 0:
    raise AnsibleError(
        f"unable to query whois:  args ")
output = proc.stdout.decode('ascii')
got = extract(output, excluded)
The first part of the code setup some IRR-specific constants: the server to query, the options to provide to the whois command and the objects to exclude from synchronization. The second part invokes the whois command, requesting all objects whose mnt-by field is the provided maintainer. Here is an example of output:
$ whois -h whois.ripe.net -s RIPE -BrG -i mnt-by fr-blade-1-mnt
[ ]
inet6num:       2a0a:e805:300::/40
netname:        FR-BLADE-CUSTOMERS-FR
country:        FR
geoloc:         48.8566 2.3522
admin-c:        BN2763-RIPE
tech-c:         BN2763-RIPE
status:         ASSIGNED
mnt-by:         fr-blade-1-mnt
remarks:        synced with cmdb
created:        2020-05-19T08:04:59Z
last-modified:  2020-05-19T08:04:59Z
source:         RIPE
[ ]
route6:         2a0a:e805:300::/40
descr:          Blade IPv6 - PA1
origin:         AS64476
mnt-by:         fr-blade-1-mnt
remarks:        synced with cmdb
created:        2019-10-01T08:19:34Z
last-modified:  2020-05-19T08:05:00Z
source:         RIPE
[ ]
The result is passed to the extract() function. It parses and normalizes the results into a dictionary mapping object names to objects. We store the result in the got variable.
def extract(raw, excluded):
    """Extract objects."""
    # First step, remove comments and unwanted lines
    objects = "\n".join([obj
                         for obj in raw.split("\n")
                         if not obj.startswith((
                                 "#",
                                 "%",
                         ))])
    # Second step, split objects
    objects = [RPSLObject(obj.strip())
               for obj in re.split(r"\n\n+", objects)
               if obj.strip()
               and not obj.startswith(
                   tuple(f" x :" for x in excluded))]
    # Last step, put objects in a dict
    objects =  repr(obj): obj
               for obj in objects 
    return objects
RPSLObject() is a class enabling normalization and comparison of objects. Look at the module code for more details.
>>> output="""
... inet6num:       2a0a:e805:300::/40
... [ ]
... """
>>> pprint( k: str(v) for k,v in extract(output, excluded=[]) )
 '<Object:inet6num:2a0a:e805:300::/40>':
   'inet6num:       2a0a:e805:300::/40\n'
   'netname:        FR-BLADE-CUSTOMERS-FR\n'
   'country:        FR\n'
   'geoloc:         48.8566 2.3522\n'
   'admin-c:        BN2763-RIPE\n'
   'tech-c:         BN2763-RIPE\n'
   'status:         ASSIGNED\n'
   'mnt-by:         fr-blade-1-mnt\n'
   'remarks:        synced with cmdb\n'
   'source:         RIPE',
 '<Object:route6:2a0a:e805:300::/40>':
   'route6:         2a0a:e805:300::/40\n'
   'descr:          Blade IPv6 - PA1\n'
   'origin:         AS64476\n'
   'mnt-by:         fr-blade-1-mnt\n'
   'remarks:        synced with cmdb\n'
   'source:         RIPE' 

Comparing with wanted objects Let s build the wanted dictionary using the same structure, thanks to the extract() function we can use verbatim:
with open(module.params['source']) as f:
    source = f.read()
wanted = extract(source, excluded)
The next step is to compare got and wanted to build the diff object:
if got != wanted:
    result['changed'] = True
    if module._diff:
        result['diff'] = [
            dict(before_header=k,
                 after_header=k,
                 before=str(got.get(k, "")),
                 after=str(wanted.get(k, "")))
            for k in set((*wanted.keys(), *got.keys()))
            if k not in wanted or k not in got or wanted[k] != got[k]]

Returning updates The module does not have a side effect. If there is a difference, we return the updates to send by email. We choose to include all wanted objects in the updates (contained in the source variable) and let the IRR ignore unmodified objects. We also append the objects to be deleted by adding a delete: attribute to each them them.
# We send all source objects and deleted objects.
deleted_mark = f" 'delete:':16 deleted by CMDB"
deleted = "\n\n".join([f" got[k].raw \n deleted_mark "
                       for k in got
                       if k not in wanted])
result['objects'] = f" source \n\n deleted "
module.exit_json(**result)

The complete code is available on GitHub. The module supports both --diff and --check flags. It does not return anything if no change is detected. It can work with APNIC, RIPE and ARIN. It is not perfect: it may not detect some changes,3 it is not able to modify objects not owned by the provided maintainer4 and some attributes cannot be modified, requiring to manually delete and recreate the updated object.5 However, this module should automate 95% of your needs.

  1. Other IRRs exist without being attached to a RIR. The most notable one is RADb.
  2. ARIN is phasing out this method in favor of IRR-online. RIPE has an API available, but email updates are still supported and not planned to be deprecated. APNIC plans to expose an API.
  3. For ARIN, we cannot query key-cert and mntner objects and therefore we cannot detect changes in them. It is also not possible to detect changes to the auth mechanisms of a mntner object.
  4. APNIC do not assign top-level objects to the maintainer associated with the owner.
  5. Changing the status of an inetnum object requires deleting and recreating the object.

27 September 2020

Iain R. Learmonth: Multicast IPTV

For almost a decade, I ve been very slowly making progress on a multicast IPTV system. Recently I ve made a significant leap forward in this project, and I wanted to write a little on the topic so I ll have something to look at when I pick this up next. I was aspiring to have a useable system by the end of today, but for a couple of reasons, it wasn t possible. When I started thinking about this project, it was still common to watch broadcast television. Over time the design of this system has been changing as new technologies have become available. Multicast IP is probably the only constant, although I m now looking at IPv6 rather than IPv4. Initially, I d been looking at DVB-T PCI cards. USB devices have become common and are available cheaply. There are also DVB-T hats available for the Raspberry Pi. I m now looking at a combination of Raspberry Pi hats and USB devices with one of each on a couple of Pis.
Two Raspberry Pis with DVB hats installed, TV antenna sockets showing Two Raspberry Pis with DVB hats installed, TV antenna sockets showing
The Raspberry Pi devices will run DVBlast, an open-source DVB demultiplexer and streaming server. Each of the tuners will be tuned to a different transponder giving me the ability to stream any combination of available channels simultaneously. This is everything that would be needed to watch TV on PCs on the home network with VLC. I ve not yet worked out if Kodi will accept multicast streams as a TV source, but I do know that Tvheadend will. Tvheadend can also act as a PVR to record programmes for later playback so is useful even if the multicast streams can be viewed directly. So how far did I get? I have built two Raspberry Pis in cases with the DVB-T hats on. They need to sit in the lounge as that s where the antenna comes down from the roof. There s no wired network connection in the lounge. I planned to use an OpenBSD box as a gateway, bridging the wireless network to a wired network. Two problems quickly emerged. The first being that the wireless card I had purchased only supported 2.4GHz, no 5GHz, and I have enough noise from neighbours that the throughput rate and packet loss are unacceptable. The second problem is that I had forgotten the problems with bridging wireless networks. To create a bridge, you need to be able to spoof the MAC addresses of wired devices on the wireless interface, but this can only be done when the wireless interface is in access point mode. So when I come back to this, I will have to look at routing rather than bridging to work around the MAC address issue, and I ll also be on the lookout for a cheap OpenBSD supported mini-PCIe wireless card that can do 5GHz.

25 September 2020

Reproducible Builds: ARDC sponsors the Reproducible Builds project

The Reproducible Builds project is pleased to announce a donation from Amateur Radio Digital Communications (ARDC) in support of its goals. ARDC s contribution will propel the Reproducible Builds project s efforts in ensuring the future health, security and sustainability of our increasingly digital society.

About Amateur Radio Digital Communications (ARDC) Amateur Radio Digital Communications (ARDC) is a non-profit that was formed to further research and experimentation with digital communications using radio, with a goal of advancing the state of the art of amateur radio and to educate radio operators in these techniques. It does this by managing the allocation of network resources, encouraging research and experimentation with networking protocols and equipment, publishing technical articles and number of other activities to promote the public good of amateur radio and other related fields. ARDC has recently begun to contribute funding to organisations, groups, individuals and projects towards these and related goals, and their grant to the Reproducible Builds project is part of this new initiative. Amateur radio is an entirely volunteer activity performed by knowledgeable hobbyists who have proven their ability by passing the appropriate government examinations. No remuneration is permitted. Ham radio, as it is also known, has proven its value in advancements of the state of the communications arts, as well as in public service during disasters and in times of emergency. For more information about ARDC, please see their website at ampr.org.

About the Reproducible Builds project One of the original promises of open source software was that peer review would result in greater end-user security and stability of our digital ecosystem. However, although it is theoretically possible to inspect and build the original source code in order to avoid maliciously-inserted flaws, almost all software today is distributed in prepackaged form. This disconnect allows third-parties to compromise systems by injecting code into seemingly secure software during the build process, as well as by manipulating copies distributed from app stores and other package repositories. In order to address this, Reproducible builds are a set of software development practices, ideas and tools that create an independently-verifiable path from the original source code, all the way to what is actually running on our machines. Reproducible builds can reveal the injection of backdoors introduced by the hacking of developers own computers, build servers and package repositories, but can also expose where volunteers or companies have been coerced into making changes via blackmail, government order, and so on. A world without reproducible builds is a world where our digital infrastructure cannot be trusted and where online communities are slower to grow, collaborate less and are increasingly fragile. Without reproducible builds, we leave space for greater encroachments on our liberties both by individuals as well as powerful, unaccountable actors such as governments, large corporations and autocratic regimes. The Reproducible Builds project began as a project within the Debian community, but is now working with many crucial and well-known free software projects such as Coreboot, openSUSE, OpenWrt, Tails, GNU Guix, Arch Linux, Tor, and many others. It is now an entirely Linux distribution independent effort and serves as the central clearing house for all issues related to securing build systems and software supply chains of all kinds. For more about the Reproducible Builds project, please see their website at reproducible-builds.org.
If you are interested in ensuring the ongoing security of the software that underpins our civilisation, and wish to sponsor the Reproducible Builds project, please reach out to the project by emailing contact@reproducible-builds.org.

22 September 2020

Russ Allbery: Review: Unconquerable Sun

Review: Unconquerable Sun, by Kate Elliott
Series: Sun Chronicles #1
Publisher: Tor
Copyright: 2020
ISBN: 1-250-19725-2
Format: Kindle
Pages: 526
Sun is the daughter and heir of the mercurial Queen-Marshal Eirene, ruler of the Republic of Chaonia. Chaonia, thanks to Eirene and her ancestors, has carved out a fiercely independent position between the Yele League and the Phene Empire. Sun's father, Prince Jo o, is one of Eirene's three consorts, all chosen for political alliances to shore up that fragile position. Jo o is Gatoi, a civilization of feared fighters and supposed barbarians from outside Chaonia who normally ally with the Phene, which complicates Sun's position as heir. Sun attempts to compensate for that by winning battles for the Republic, following in the martial footsteps of her mother. The publisher's summary of this book is not great (I'm a huge fan of Princess Leia, but that is... not the analogy that comes to mind), so let me try to help. This is gender-swapped Alexander the Great in space. However, it is gender-swapped Alexander the Great in space with her Companions, which means the DNA of this novel is half space opera and half heist story (without, to be clear, an actual heist, although there are some heist-like maneuvers). It's also worth mentioning that Sun, like Alexander, is not heterosexual. The other critical thing to know before reading, mostly because it will get you through the rather painful start, is that the most interesting viewpoint character in this book is not Sun, the Alexander analogue. It's Persephone, who isn't introduced until chapter seven. Significant disclaimer up front: I got a reasonably typical US grade school history of Alexander the Great, which means I was taught that he succeeded his father, conquered a whole swath of the middle of the Eurasian land mass at a very young age, and then died and left his empire to his four generals who promptly divided it into four uninteresting empires that no one's ever heard of, and that's why Rome is more important than Greece. (I put in that last bit to troll one specific person.) I am therefore not the person to judge the parallels between this story and known history, or to notice any damage done to Greek pride, or to pick up on elements that might cause someone with a better grasp of that history to break out in hives. I did enough research to know that one scene in this book is lifted directly out of Alexander's life, but I'm not sure how closely the other parallels track. Yele is probably southern Greece and Phene is probably Persia, but I'm not certain even of that, and some of the details don't line up. If I had to hazard a guess, I'd say that Elliott has probably mangled history sufficiently to make it clear that this isn't intended to be a retelling, but if the historical parallels are likely to bother you, you may want to do more research before reading. What I can say is that the space opera setup, while a bit stock, has all the necessary elements to make me happy. Unconquerable Sun is firmly in the "lost Earth" tradition: The Argosy fleet fled the now-mythical Celestial Empire and founded a new starfaring civilization without any contact with their original home. Eventually, they invented (or discovered; the characters don't know) the beacons, which allow for instantaneous travel between specific systems without the long (but still faster-than-light) journeys of the knnu drive. More recently, the beacon network has partly collapsed, cutting off the characters' known world from the civilization that was responsible for the beacons and guarded their secrets. It's a fun space opera history with lots of lost knowledge to reference and possibly discover, and with plot-enabling military choke points at the surviving beacons that link multiple worlds. This is all background to the story, which is the ongoing war between Chaonia and the Phene Empire mixed with cutthroat political maneuvering between the great houses of the Chaonian Republic. This is where the heist aspects come in. Each house sends one representative to join the household of the Queen-Marshal and (more to the point for this story) another to join her heir. Sun has encouraged the individual and divergent talents of her Companions and their cee-cees (an unfortunate term that I suspect is short for Companion's Companion) and forged them into a good working team. A team that's about to be disrupted by the maneuverings of a rival house and the introduction of a new team member whom no one wants. A problem with writing tactical geniuses is that they often aren't good viewpoint characters. Sun's tight third-person chapters, which is a little less than half the book, advance the plot and provide analysis of the interpersonal dynamics of the characters, but aren't the strength of the story. That lies with the interwoven first-person sections that follow Persephone, an altogether more interesting character. Persephone is the scion of the house that is Sun's chief rival, but she has no interest in being part of that house or its maneuverings. When the story opens, she's a cadet in a military academy for recruits from the commoners, having run away from home, hidden her identity, and won a position through the open entrance exams. She of course doesn't stay there; her past catches up with her and she gets assigned to Sun, to a great deal of mutual suspicion. She also is assigned an impeccably dressed and stunningly beautiful cee-cee, Tiana, who has her own secrets and who was my favorite character in the book. Somewhat unusually for the space opera tradition, this is a book that knows that common people exist and have interesting lives. It's primarily focused on the ruling houses, but that focus is not exclusive and the rulers do not have a monopoly on competence. Elliott also avoids narrowing the political field too far; the Gatoi are separate from the three rival powers, and there are other groups with traditions older than the Chaonian Republic and their own agendas. Sun and her Companions are following a couple of political threads, but there is clearly more going on in this world than that single plot. This is exactly the kind of story I think of when I think space opera. It's not doing anything that original or groundbreaking, and it's not going to make any of my lists of great literature, but it's a fun romp with satisfyingly layered bits of lore, a large-scale setting with lots of plot potential, and (once we get through the confusing and somewhat tedious process of introducing rather too many characters in short succession) some great interpersonal dynamics. It's the kind of book in which the characters are in the middle of decisive military action in an interstellar war and are also near-teenagers competing for ratings in an ad hoc reality TV show, primarily as an excuse to create tactical distractions for Sun's latest scheme. The writing is okay but not great, and the first few chapters have some serious infodumping problems, but I thoroughly enjoyed the whole book and will pre-order the sequel. One Amazon review complained that Unconquerable Sun is not a space opera like Hyperion or Use of Weapons. That is entirely true, but if that's your standard for space opera, the world may be a disappointing place. This is a solid entry in a subgenre I love, with some great characters, sarcasm, competence porn, plenty of pages to keep turning, a few twists, and the promise of more to come. Recommended. Followed by the not-yet-published Furious Heaven. Rating: 7 out of 10

21 September 2020

Kees Cook: security things in Linux v5.7

Previously: v5.6 Linux v5.7 was released at the end of May. Here s my summary of various security things that caught my attention: arm64 kernel pointer authentication
While the ARMv8.3 CPU Pointer Authentication (PAC) feature landed for userspace already, Kristina Martsenko has now landed PAC support in kernel mode. The current implementation uses PACIASP which protects the saved stack pointer, similar to the existing CONFIG_STACKPROTECTOR feature, only faster. This also paves the way to sign and check pointers stored in the heap, as a way to defeat function pointer overwrites in those memory regions too. Since the behavior is different from the traditional stack protector, Amit Daniel Kachhap added an LKDTM test for PAC as well. BPF LSM
The kernel s Linux Security Module (LSM) API provide a way to write security modules that have traditionally implemented various Mandatory Access Control (MAC) systems like SELinux, AppArmor, etc. The LSM hooks are numerous and no one LSM uses them all, as some hooks are much more specialized (like those used by IMA, Yama, LoadPin, etc). There was not, however, any way to externally attach to these hooks (not even through a regular loadable kernel module) nor build fully dynamic security policy, until KP Singh landed the API for building LSM policy using BPF. With this, it is possible (for a privileged process) to write kernel LSM hooks in BPF, allowing for totally custom security policy (and reporting). execve() deadlock refactoring
There have been a number of long-standing races in the kernel s process launching code where ptrace could deadlock. Fixing these has been attempted several times over the last many years, but Eric W. Biederman and Ernd Edlinger decided to dive in, and successfully landed the a series of refactorings, splitting up the problematic locking and refactoring their uses to remove the deadlocks. While he was at it, Eric also extended the exec_id counter to 64 bits to avoid the possibility of the counter wrapping and allowing an attacker to send arbitrary signals to processes they normally shouldn t be able to. slub freelist obfuscation improvements
After Silvio Cesare observed some weaknesses in the implementation of CONFIG_SLAB_FREELIST_HARDENED s freelist pointer content obfuscation, I improved their bit diffusion, which makes attacks require significantly more memory content exposures to defeat the obfuscation. As part of the conversation, Vitaly Nikolenko pointed out that the freelist pointer s location made it relatively easy to target too (for either disclosures or overwrites), so I moved it away from the edge of the slab, making it harder to reach through small-sized overflows (which usually target the freelist pointer). As it turns out, there were a few assumptions in the kernel about the location of the freelist pointer, which had to also get cleaned up. RISCV page table dumping
Following v5.6 s generic page table dumping work, Zong Li landed the RISCV page dumping code. This means it s much easier to examine the kernel s page table layout when running a debug kernel (built with PTDUMP_DEBUGFS), visible in /sys/kernel/debug/kernel_page_tables. array index bounds checking
This is a pretty large area of work that touches a lot of overlapping elements (and history) in the Linux kernel. The short version is: C is bad at noticing when it uses an array index beyond the bounds of the declared array, and we need to fix that. For example, don t do this:
int foo[5];
...
foo[8] = bar;
The long version gets complicated by the evolution of flexible array structure members, so we ll pause for a moment and skim the surface of this topic. While things like CONFIG_FORTIFY_SOURCE try to catch these kinds of cases in the memcpy() and strcpy() family of functions, it doesn t catch it in open-coded array indexing, as seen in the code above. GCC has a warning (-Warray-bounds) for these cases, but it was disabled by Linus because of all the false positives seen due to fake flexible array members. Before flexible arrays were standardized, GNU C supported zero sized array members. And before that, C code would use a 1-element array. These were all designed so that some structure could be the header in front of some data blob that could be addressable through the last structure member:
/* 1-element array */
struct foo  
    ...
    char contents[1];
 ;
/* GNU C extension: 0-element array */
struct foo  
    ...
    char contents[0];
 ;
/* C standard: flexible array */
struct foo  
    ...
    char contents[];
 ;
instance = kmalloc(sizeof(struct foo) + content_size);
Converting all the zero- and one-element array members to flexible arrays is one of Gustavo A. R. Silva s goals, and hundreds of these changes started landing. Once fixed, -Warray-bounds can be re-enabled. Much more detail can be found in the kernel s deprecation docs. However, that will only catch the visible at compile time cases. For runtime checking, the Undefined Behavior Sanitizer has an option for adding runtime array bounds checking for catching things like this where the compiler cannot perform a static analysis of the index values:
int foo[5];
...
for (i = 0; i < some_argument; i++)  
    ...
    foo[i] = bar;
    ...
 
It was, however, not separate (via kernel Kconfig) until Elena Petrova and I split it out into CONFIG_UBSAN_BOUNDS, which is fast enough for production kernel use. With this enabled, it's now possible to instrument the kernel to catch these conditions, which seem to come up with some regularity in Wi-Fi and Bluetooth drivers for some reason. Since UBSAN (and the other Sanitizers) only WARN() by default, system owners need to set panic_on_warn=1 too if they want to defend against attacks targeting these kinds of flaws. Because of this, and to avoid bloating the kernel image with all the warning messages, I introduced CONFIG_UBSAN_TRAP which effectively turns these conditions into a BUG() without needing additional sysctl settings. Fixing "additive" snprintf() usage
A common idiom in C for building up strings is to use sprintf()'s return value to increment a pointer into a string, and build a string with more sprintf() calls:
/* safe if strlen(foo) + 1 < sizeof(string) */
wrote  = sprintf(string, "Foo: %s\n", foo);
/* overflows if strlen(foo) + strlen(bar) > sizeof(string) */
wrote += sprintf(string + wrote, "Bar: %s\n", bar);
/* writing way beyond the end of "string" now ... */
wrote += sprintf(string + wrote, "Baz: %s\n", baz);
The risk is that if these calls eventually walk off the end of the string buffer, it will start writing into other memory and create some bad situations. Switching these to snprintf() does not, however, make anything safer, since snprintf() returns how much it would have written:
/* safe, assuming available <= sizeof(string), and for this example
 * assume strlen(foo) < sizeof(string) */
wrote  = snprintf(string, available, "Foo: %s\n", foo);
/* if (strlen(bar) > available - wrote), this is still safe since the
 * write into "string" will be truncated, but now "wrote" has been
 * incremented by how much snprintf() *would* have written, so "wrote"
 * is now larger than "available". */
wrote += snprintf(string + wrote, available - wrote, "Bar: %s\n", bar);
/* string + wrote is beyond the end of string, and availabe - wrote wraps
 * around to a giant positive value, making the write effectively 
 * unbounded. */
wrote += snprintf(string + wrote, available - wrote, "Baz: %s\n", baz);
So while the first overflowing call would be safe, the next one would be targeting beyond the end of the array and the size calculation will have wrapped around to a giant limit. Replacing this idiom with scnprintf() solves the issue because it only reports what was actually written. To this end, Takashi Iwai has been landing a bunch scnprintf() fixes. That's it for now! Let me know if there is anything else you think I should mention here. Next up: Linux v5.8.

2020, Kees Cook. This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 License.
CC BY-SA 4.0

Antoine Beaupr : PSA: Mailman used to harrass people

It seems that Mailman instances are being abused to harrass people with subscribe spam. If some random people complain to you that they "never wanted to subscribe to your mailing list", you may be a victim to that attack, even if you run the latest Mailman 2.

TL;DR: IKR! HOW DO I FIX THIS!? Make sure you have SUBSCRIBE_FORM_SECRET set in your mailman configuration:
SECRET=$(tr -dc 'A-Za-z0-9' < /dev/urandom   head -c 30)'
echo "SUBSCRIBE_FORM_SECRET = '$SECRET'" >> /etc/mailman/mm.cfg
This will add a magic token to all forms in the Mailman web forms that will force the attacker to at least get a token before asking for registration. There are, of course, other ways of performing the attack then, but it's more expensive than a single request for the attacker and keeps most of the junk out.

Other solutions I originally deployed a different fix, using referrer checks and an IP block list:
RewriteMap hosts-deny  txt:/etc/apache2/blocklist.txt
RewriteCond $ hosts-deny:% REMOTE_ADDR NOT-FOUND  !=NOT-FOUND [OR]
RewriteCond $ hosts-deny:% REMOTE_HOST NOT-FOUND  !=NOT-FOUND [OR]
RewriteCond % HTTP_REFERER  !^https://lists.torproject.org/$ [NC]
RewriteRule ^/cgi-bin/mailman/subscribe/ - [F]
# see also https://www.w3.org/TR/referrer-policy/#referrer-policy-origin
Header always set Referrer-Policy "origin"
I kept those restrictions in place because it keeps the spammers from even hitting the Mailman CGI, which is useful to preserve our server resources. But if "they" escalate with smarter crawlers, the block list will still be useful. You can use this query to extract the top 10 IP addresses used for subscription attempts:
awk '  print $NF  ' /var/log/mailman/subscribe   sort   uniq -c   sort -n   tail -10    awk '  print $2 " " $1  '
Note that this might include email-based registration, but in our logs those are extremely rare: only two in three weeks, out of over 73,000 requests. I also use this to keep an eye on the logs:
tail -f  /var/log/mailman/subscribe /var/log/apache2/lists.torproject.org-access.log   grep -v 'GET /pipermail/'
The server-side mitigations might also be useful if you happen to run an extremely old version of Mailman, that is pre-2.1.18, but it's now over 6 years old and part of every supported Debian release out there (all the way back to Debian 8 jessie).

Why does that attack work? Because Mailman 2 doesn't have CSRF tokens in its forms by default, anyone can send a POST request to /mailman/subscribe/LISTNAME to have Mailman send an email to the user. In the old "Internet is for nice people" universe, that wasn't a problem: all it does is ask the victim if they want to subscribe to LISTNAME. Innocuous, right? But in the brave, new, post-Eternal-September, "Internet is for stupid" universe, some assholes think it's a good idea to make a form that collects hundreds of mailing list URLs and spam them through an iframe. To see what that looks like, you can look at the rendered source code behind samedyfreeday.co.uk (not linking to avoid promoting it). That site does what is basically a distributed cross-site scripting attack against Mailman servers. Obviously, CSRF protection should be enabled by default in Mailman, but there you go. Hopefully this will help some folks... (The latest Mailman 3 release doesn't suffer from such idiotic defaults and ships with proper CSRF protection out of the box.)

Jonathan McDowell: Mainline Linux on the MikroTik RB3011

I upgraded my home internet connection to fibre (FTTP) last October. I m still on an 80M/20M service, so it s no faster than my old VDSL FTTC connection was, and as a result for a long time I continued to use my HomeHub 5A running OpenWRT. However the FTTP ONT meant I was using up an additional ethernet port on the router, and I was already short, so I ended up with a GigE switch in use as well. Also my wifi is handled by a UniFi, which takes its power via Power-over-Ethernet. That mean I had a router, a switch and a PoE injector all in close proximity. I wanted to reduce the number of devices, and ideally upgrade to something that could scale once I decide to upgrade my FTTP service speed. Looking around I found the MikroTik RB3011UiAS-RM, which is a rack mountable device with 10 GigE ports (plus an SFP slot) and a dual core Qualcomm IPQ8064 ARM powering it. There s 1G RAM and 128MB NAND flash, as well as a USB3 port. It also has PoE support. On paper it seemed like an ideal device. I wasn t particularly interested in running RouterOS on it (the provided software), but that s based on Linux and there was some work going on within OpenWRT to add support, so it seemed like a worthwhile platform to experiment with (what, you expected this to be about me buying an off the shelf device and using it with only the supplied software?). As an added bonus a friend said he had one he wasn t using, and was happy to sell it to me for a bargain price. RB3011 router in use I did try out RouterOS to start with, but I didn t find it particularly compelling. I m comfortable configuring firewalling and routing at a Linux command line, and I run some additional services on the router like my MQTT broker, and mqtt-arp, my wifi device presence monitor. I could move things around such that they ran on the house server, but I consider them core services and as a result am happier with them on the router. The first step was to get something booting on the router. Luckily it has an RJ45 serial console port on the back, and a reasonably featured bootloader that can manage to boot via tftp over the network. It wants an ELF binary rather than a plain kernel, but Sergey Sergeev had done the hard work of getting u-boot working for the IPQ8064, which mean I could just build normal u-boot images to try out. Linux upstream already had basic support for a lot of the pieces I was interested in. There s a slight fudge around AUTO_ZRELADDR because the network coprocessors want a chunk of memory at the start of RAM, but there s ongoing discussions about how to handle this cleanly that I m hopeful will eventually mean I can drop that hack. Serial, ethernet, the QCA8337 switches (2 sets of 5 ports, tied to different GigE devices on the processor) and the internal NOR all had drivers, so it was a matter of crafting an appropriate DTB to get them working. That left niggles. First, the second switch is hooked up via SGMII. It turned out the IPQ806x stmmac driver didn t initialise the clocks in this mode correctly, and neither did the qca8k switch driver. So I need to fix up both of those (Sergey had handled the stmmac driver, so I just had to clean up and submit his patch). Next it turned out the driver for talking to the Qualcomm firmware (SCM) had been updated in a way that broke the old method needed on the IPQ8064. Some git archaeology figured that one out and provided a solution. Ansuel Smith helpfully provided the DWC3 PHY driver for the USB port. That got me to the point I could put a Debian armhf image onto a USB stick and mount that as root, which made debugging much easier. At this point I started to play with configuring up the device to actually act as a router. I make use of a number of VLANs on my home network, so I wanted to make sure I could support those. Turned out the stmmac driver wasn t happy reconfiguring its MTU because the IPQ8064 driver doesn t configure the FIFO sizes. I found what seem to be the correct values and plumbed them in. Then the qca8k driver only supported port bridging. I wanted the ability to have a trunk port to connect to the upstairs switch, while also having ports that only had a single VLAN for local devices. And I wanted the switch to handle this rather than requiring the CPU to bridge the traffic. Thankfully it s easy to find a copy of the QCA8337 datasheet and the kernel Distributed Switch Architecture is pretty flexible, so I was able to implement the necessary support. I stuck with Debian on the USB stick for actually putting the device into production. It makes it easier to fix things up if necessary, and the USB stick allows for a full Debian install which would be tricky on the 128M of internal NAND. That means I can use things like nftables for my firewalling, and use the standard Debian packages for things like collectd and mosquitto. Plus for debug I can fire up things like tcpdump or tshark. Which ended up being useful because when I put the device into production I started having weird IPv6 issues that turned out to be a lack of proper Ethernet multicast filter support in the IPQ806x ethernet device. The driver would try and setup the multicast filter for the IPv6 NDP related packets, but it wouldn t actually work. The fix was to fall back to just receiving all multicast packets - this is what the vendor driver does. Most of this work will be present once the 5.9 kernel is released - the basics are already in 5.8. Currently not queued up that I can think of are the following: Overall I consider the device a success, and it s been entertaining getting it working properly. I m running a mostly mainline kernel, it s handling my house traffic without breaking a sweat, and the fact it s running Debian makes it nice and easy to throw more things on it as I desire. However it turned out the RB3011 isn t as perfect device as I d hoped. The PoE support is passive, and the UniFi wants 802.1af. So I was going to end up with 2 devices. As it happened I picked up a cheap D-Link DGS-1210-10P switch, which provides the PoE support as well as some additional switch ports. Plus it runs Linux, so more on that later

Russ Allbery: Review: Lower Ed

Review: Lower Ed, by Tressie McMillan Cottom
Publisher: The New Press
Copyright: 2017
Printing: 2018
ISBN: 1-62097-472-X
Format: Kindle
Pages: 217
Lower Ed (subtitled The Troubling Rise of For-Profit Colleges in the New Economy) is the first book by sociologist Tressie McMillan Cottom. (I previously reviewed her second book, the excellent essay collection Thick.) It is a deep look at the sociology of for-profit higher education in the United States based on interviews with students and executives, analysis of Wall Street filings, tests of the admissions process, and her own personal experiences working for two of the schools. One of the questions that McMillan Cottom tries to answer is why students choose to enroll in these institutions, particularly the newer type of institution funded by federal student loans and notorious for being more expensive and less valuable than non-profit colleges and universities. I was hesitant to read this book because I find for-profit schools depressing. I grew up with the ubiquitous commercials, watched the backlash develop, and have a strongly negative impression of the industry, partly influenced by having worked in traditional non-profit higher education for two decades. The prevailing opinion in my social group is that they're a con job. I was half-expecting a reinforcement of that opinion by example, and I don't like reading infuriating stories about people being defrauded. I need not have worried. This is not that sort of book (nor, in retrospect, do I think McMillan Cottom would approach a topic from that angle). Sociology is broader than reporting. Lower Ed positions for-profit colleges within a larger social structure of education, credentialing, and changes in workplace expectations; takes a deep look at why they are attractive to their students; and humanizes and complicates the motives and incentives of everyone involved, including administrators and employees of for-profit colleges as well as the students. McMillan Cottom does of course talk about the profit motive and the deceptions surrounding that, but the context is less that of fraud that people are unable to see through and more a balancing of the drawbacks of a set of poor choices embedded in institutional failures. One of my metrics for a good non-fiction book is whether it introduces me to a new idea that changes how I analyze the world. Lower Ed does that twice. The first idea is the view of higher education through the lens of risk shifting. It used to be common for employers to hire people without prior job-specific training and do the training in-house, possibly through an apprenticeship structure. More notably, once one was employed by a particular company, the company routinely arranged or provided ongoing training. This went hand-in-hand with a workplace culture of long tenure, internal promotion, attempts to avoid layoffs, and some degree of mutual loyalty. Companies expected to invest significantly in an employee over their career and thus also had an incentive to retain that employee rather than train someone for a competitor. However, from a purely financial perspective, this is a risk and an inefficiency, similar to the risk of carrying a large inventory of parts and components. Companies have responded to investor-driven focus on profits and efficiency by reducing overhead and shifting risk. This leads to the lean supply chain, where no one pays for parts to sit around in warehouses and companies aren't caught with large stockpiles of now-useless components, but which is more sensitive to any disruption (such as from a global pandemic). And, for employment, it leads to a desire to hire pre-trained workers, retain only enough workers to do the current amount of work, and replace them with new workers who already have appropriate training rather than retrain them. The effect of the corporate decision to only hire pre-trained employees is to shift the risk and expense of training from the company to the prospective employee. The individual has to seek out training at their own expense in the hope (not guarantee) that at the conclusion of that training they will get or retain a job. People therefore turn to higher education to both provide that training and to help them decide what type of training will eventually be valuable. This has a long history with certain professional fields (doctors and lawyers, for example), but the requirements for completing training in those fields are relatively clear (a professional license to practice) and the compensation reflects the risk. What's new is the shift of training risk to the individual in more mundane jobs, without any corresponding increase in compensation. This, McMillan Cottom explains, is the background for the growth in demand for higher education in general and the the type of education offered by for-profit colleges in particular. Workers who in previous eras would be trained by their employers are now responsible for their own training. That training is no longer judged by the standards of a specific workplace, but is instead evaluated by a hiring process that expects constant job-shifting. This leads to increased demand by both workers and employers for credentials: some simple-to-check certificate of completion of training that says that this person has the skills to immediately start doing some job. It also leads to a demand for more flexible class hours, since the student is now often someone older with a job and a family to balance. Their ongoing training used to be considered a cost of business and happen during their work hours; now it is something they have to fit around the contours of their life because their employer has shifted that risk to them. The risk-shifting frame makes sense of the "investment" language so common in for-profit education. In this job economy, education as investment is not a weird metaphor for the classic benefits of a liberal arts education: broadened perspective, deeper grounding in philosophy and ethics, or heightened aesthetic appreciation. It's an investment in the literal financial sense; it is money that you spend now in order to get a financial benefit (a job) in the future. People have to invest in their own training because employers are no longer doing so, but still require the outcome of that investment. And, worse, it's primarily a station-keeping investment. Rather than an optional expenditure that could reap greater benefits later, it's a mandatory expenditure to prevent, at best, stagnation in a job paying poverty wages, and at worst the disaster of unemployment. This explains renewed demand for higher education, but why for-profit colleges? We know they cost more and have a worse reputation (and therefore their credentials have less value) than traditional non-profit colleges. Flexible hours and class scheduling explains some of this but not all of it. That leads to the second perspective-shifting idea I got from Lower Ed: for-profit colleges are very good at what they focus time and resources on, and they focus on enrolling students. It is hard to enroll in a university! More precisely, enrolling in a university requires bureaucracy navigation skills, and those skills are class-coded. The people who need them the most are the least likely to have them. Universities do not reach out to you, nor do they guide you through the process. You have to go to them and discover how to apply, something that is often made harder by the confusing state of many university web sites. The language and process is opaque unless other people in your family have experience with universities and can explain it. There might be someone you can reach on the phone to ask questions, but they're highly unlikely to proactively guide you through the remaining steps. It's your responsibility to understand deadlines, timing, and sequence of operations, and if you miss any of the steps (due to, for example, the overscheduled life of someone in need of better education for better job prospects), the penalty in time and sometimes money can be substantial. And admission is just the start; navigating financial aid, which most students will need, is an order of magnitude more daunting. Community colleges are somewhat easier (and certainly cheaper) than universities, but still have similar obstacles (and often even worse web sites). It's easy for people like me, who have long professional expertise with bureaucracies, family experience with higher education, and a support network of people to nag me about deadlines, to underestimate this. But the application experience at a for-profit college is entirely different in ways far more profound than I had realized. McMillan Cottom documents this in detail from her own experience working for two different for-profit colleges and from an experiment where she indicated interest in multiple for-profit colleges and then stopped responding before signing admission paperwork. A for-profit college is fully invested in helping a student both apply and get financial aid, devotes someone to helping them through that process, does not expect them to understand how to navigate bureaucracies or decipher forms on their own, does not punish unexpected delays or missed appointments, and goes to considerable lengths to try to keep anyone from falling out of the process before they are enrolled. They do not expect their students to already have the skills that one learns from working in white-collar jobs or from being surrounded by people who do. They provide the kind of support that an educational institution should provide to people who, by definition, don't understand something and need to learn. Reading about this was infuriating. Obviously, this effort to help people enroll is largely for predatory reasons. For-profit schools make their money off federal loans and they don't get that money unless they can get someone to enroll and fill out financial paperwork (and to some extent keep them enrolled), so admissions is their cash cow and they act accordingly. But that's not why I found it infuriating; that's just predictable capitalism. What I think is inexcusable is that nothing they do is that difficult. We could being doing the same thing for prospective community college students but have made the societal choice not to. We believe that education is valuable, we constantly advocate that people get more job training and higher education, and yet we demand prospective students navigate an unnecessarily baroque and confusing application process with very little help, and then stereotype and blame them for failing to do so. This admission support is not a question of resources. For-profit colleges are funded almost entirely by federally-guaranteed student loans. We are paying them to help people apply. It is, in McMillan Cottom's term, a negative social insurance program. Rather than buffering people against the negative effects of risk-shifting of employers by helping them into the least-expensive and most-effective training programs (non-profit community colleges and universities), we are spending tax dollars to enrich the shareholders of for-profit colleges while underfunding the alternatives. We are choosing to create a gap that routes government support to the institution that provides worse training at higher cost but is very good at helping people apply. It's as if the unemployment system required one to use payday lenders to get one's unemployment check. There is more in this book I want to talk about, but this review is already long enough. Suffice it to say that McMillan Cottom's analysis does not stop with market forces and the admission process, and the parts of her analysis that touch on my own personal experience as someone with a somewhat unusual college path ring very true. Speaking as a former community college student, the discussion of class credit transfer policies and the way that institutional prestige gatekeeping and the desire to push back against low-quality instruction becomes a trap that keeps students in the for-profit system deserves another review this length. So do the implications of risk-shifting and credentialism on the morality of "cheating" on schoolwork. As one would expect from the author of the essay "Thick" about bringing context to sociology, Lower Ed is personal and grounded. McMillan Cottom doesn't shy away from including her own experiences and being explicit about her sources and research. This is backed up by one of the best methodological notes sections I've seen in a book. One of the things I love about McMillan Cottom's writing is that it's solidly academic, not in the sense of being opaque or full of jargon (the text can be a bit dense, but I rarely found it hard to follow), but in the sense of being clear about the sources of knowledge and her methods of extrapolation and analysis. She brings her receipts in a refreshingly concrete way. I do have a few caveats. First, I had trouble following a structure and line of reasoning through the whole book. Each individual point is meticulously argued and supported, but they are not always organized into a clear progression or framework. That made Lower Ed feel at times like a collection of high-quality but somewhat unrelated observations about credentials, higher education, for-profit colleges, their student populations, their business models, and their relationships with non-profit schools. Second, there are some related topics that McMillan Cottom touches on but doesn't expand sufficiently for me to be certain I understood them. One of the big ones is credentialism. This is apparently a hot topic in sociology and is obviously important to this book, but it's referenced somewhat glancingly and was not satisfyingly defined (at least for me). There are a few similar places where I almost but didn't quite follow a line of reasoning because the book structure didn't lay enough foundation. Caveats aside, though, this was meaty, thought-provoking, and eye-opening, and I'm very glad that I read it. This is a topic that I care more about than most people, but if you have watched for-profit colleges with distaste but without deep understanding, I highly recommend Lower Ed. Rating: 8 out of 10

19 September 2020

Vincent Bernat: Keepalived and unicast over multiple interfaces

Keepalived is a Linux implementation of VRRP. The usual role of VRRP is to share a virtual IP across a set of routers. For each VRRP instance, a leader is elected and gets to serve the IP address, ensuring the high availability of the attached service. Keepalived can also be used for a generic leader election, thanks to its ability to use scripts for healthchecking and run commands on state change. A simple configuration looks like this:
vrrp_instance gateway1  
  state BACKUP          #  
  interface eth0        #  
  virtual_router_id 12  #  
  priority 101          #  
  virtual_ipaddress  
    2001:db8:ff/64
   
 
The state keyword in instructs Keepalived to not take the leader role when starting. Otherwise, incoming nodes create a temporary disruption by taking over the IP address until the election settles. The interface keyword in defines the interface for sending and receiving VRRP packets. It is also the default interface to configure the virtual IP address. The virtual_router_id directive in is common to all nodes sharing the virtual IP. The priority keyword in helps choosing which router will be elected as leader. If you need more information around Keepalived, be sure to check the documentation. VRRP design is tied to Ethernet networks and requires a multicast-enabled network for communication between nodes. In some environments, notably public clouds, multicast is unavailable. In this case, Keepalived can send VRRP packets using unicast:
vrrp_instance gateway1  
  state BACKUP
  interface eth0
  virtual_router_id 12
  priority 101
  unicast_peer  
    2001:db8::11
    2001:db8::12
   
  virtual_ipaddress  
    2001:db8:ff/64 dev lo
   
 
Another process, like a BGP daemon, should advertise the virtual IP address to the network . If needed, Keepalived can trigger whatever action is needed for this by using notify_* scripts. Until version 2.21 (not released yet), the interface directive is mandatory and Keepalived will transmit and receive VRRP packets on this interface only. If peers are reachable through several interfaces, like on a BGP on the host setup, you need a workaround. A simple one is to use a VXLAN interface:
$ ip -6 link add keepalived6 type vxlan id 6 dstport 4789 local 2001:db8::10 nolearning
$ bridge fdb append 00:00:00:00:00:00 dev keepalived6 dst 2001:db8::11
$ bridge fdb append 00:00:00:00:00:00 dev keepalived6 dst 2001:db8::12
$ ip link set up dev keepalived6
Learning of MAC addresses is disabled and one generic entry for each peer is added in the forwarding database: transmitted packets are broadcasted to all peers, notably VRRP packets. Have a look at VXLAN & Linux for additional details.
vrrp_instance gateway1  
  state BACKUP
  interface keepalived6
  mcast_src_ip 2001:db8::10
  virtual_router_id 12
  priority 101
  virtual_ipaddress  
    2001:db8:ff/64 dev lo
   
 
Starting from Keepalived 2.21, unicast_peer can be used without the interface directive. I think using VXLAN is still a neat trick applicable to other situations where communication using broadcast or multicast is needed, while the underlying network provide no support for this.

Vincent Bernat: Syncing NetBox with a custom Ansible module

The netbox.netbox collection from Ansible Galaxy provides several modules to update NetBox objects:
- name: create a device in NetBox
  netbox_device:
    netbox_url: http://netbox.local
    netbox_token: s3cret
    data:
      name: to3-p14.sfo1.example.com
      device_type: QFX5110-48S
      device_role: Compute Switch
      site: SFO1
However, if NetBox is not your source of truth, you may want to ensure it stays in sync with your configuration management database1 by removing outdated devices or IP addresses. While it should be possible to glue together a playbook with a query, a loop and some filtering to delete unwanted elements, it feels clunky, inefficient and an abuse of YAML as a programming language. A specific Ansible module solves this issue and is likely more flexible.

Notice I recommend that you read Writing a custom Ansible module as an introduction, as well as Syncing MySQL tables for a first simpler example.

Code The module has the following signature and it syncs NetBox with the content of the provided YAML file:
netbox_sync:
  source: netbox.yaml
  api: https://netbox.example.com
  token: s3cret
The synchronized objects are:
  • sites,
  • manufacturers,
  • device types,
  • device roles,
  • devices, and
  • IP addresses.
In our environment, the YAML file is generated from our configuration management database and contains a set of devices and a list of IP addresses:
devices:
  ad2-p6.sfo1.example.com:
     datacenter: sfo1
     manufacturer: Cisco
     model: Catalyst 2960G-48TC-L
     role: net_tor_oob_switch
  to1-p6.sfo1.example.com:
     datacenter: sfo1
     manufacturer: Juniper
     model: QFX5110-48S
     role: net_tor_gpu_switch
# [ ]
ips:
  - device: ad2-p6.example.com
    ip: 172.31.115.18/21
    interface: oob
  - device: to1-p6.example.com
    ip: 172.31.115.33/21
    interface: oob
  - device: to1-p6.example.com
    ip: 172.31.254.33/32
    interface: lo0.0
# [ ]
The network team is not the sole tenant in NetBox. While adding new objects or modifying existing ones should be relatively safe, deleting unwanted objects can be risky. The module only deletes objects it did create or modify. To identify them, it marks them with a specific tag, cmdb. Most objects in NetBox accept tags.

Module definition Starting from the skeleton described in the previous article, we define the module:
module_args = dict(
    source=dict(type='path', required=True),
    api=dict(type='str', required=True),
    token=dict(type='str', required=True, no_log=True),
    max_workers=dict(type='int', required=False, default=10)
)
result = dict(
    changed=False
)
module = AnsibleModule(
    argument_spec=module_args,
    supports_check_mode=True
)
It contains an additional optional arguments defining the number of workers to talk to NetBox and query the existing objects in parallel to speedup the execution.

Abstracting synchronization We need to synchronize different object types, but once we have a list of objects we want in NetBox, the grunt work is always the same:
  • check if the objects already exist,
  • retrieve them and put them in a form suitable for comparison,
  • retrieve the extra objects we don t want anymore,
  • compare the two sets, and
  • add missing objects, update existing ones, delete extra ones.
We code these behaviours into a Synchronizer abstract class. For each kind of object, a concrete class is built with the appropriate class attributes to tune its behaviour and a wanted() method to provide the objects we want. I am not explaining the abstract class code here. Have a look at the source if you want.

Synchronizing tags and tenants As a starter, here is how we define the class synchronizing the tags:
class SyncTags(Synchronizer):
    app = "extras"
    table = "tags"
    key = "name"
    def wanted(self):
        return  "cmdb": dict(
            slug="cmdb",
            color="8bc34a",
            description="synced by network CMDB") 
The app and table attributes defines the NetBox objects we want to manipulate. The key attribute is used to determine how to lookup for existing objects. In this example, we want to lookup tags using their names. The wanted() method is expected to return a dictionary mapping object keys to the list of wanted attributes. Here, the keys are tag names and we create only one tag, cmdb, with the provided slug, color and description. This is the tag we will use to mark the objects we create or modify. If the tag does not exist, it is created. If it exists, the provided attributes are updated. Other attributes are left untouched. We also want to create a specific tenant for objects accepting such an attribute (devices and IP addresses):
class SyncTenants(Synchronizer):
    app = "tenancy"
    table = "tenants"
    key = "name"
    def wanted(self):
        return  "Network": dict(slug="network",
                                description="Network team") 

Synchronizing sites We also need to synchronize the list of sites. This time, the wanted() method uses the information provided in the YAML file: it walks the devices and builds a set of datacenter names.
class SyncSites(Synchronizer):
    app = "dcim"
    table = "sites"
    key = "name"
    only_on_create = ("status", "slug")
    def wanted(self):
        result = set(details["datacenter"]
                     for details in self.source['devices'].values()
                     if "datacenter" in details)
        return  k: dict(slug=k,
                        status="planned")
                for k in result 
Thanks to the use of the only_on_create attribute, the specified attributes are not updated if they are different. The goal of this synchronizer is mostly to collect the references to the different sites for other objects.
>>> pprint(SyncSites(**sync_args).wanted())
 'sfo1':  'slug': 'sfo1', 'status': 'planned' ,
 'chi1':  'slug': 'chi1', 'status': 'planned' ,
 'nyc1':  'slug': 'nyc1', 'status': 'planned' 

Synchronizing manufacturers, device types and device roles The synchronization of manufacturers is pretty similar, except we do not use the only_on_create attribute:
class SyncManufacturers(Synchronizer):
    app = "dcim"
    table = "manufacturers"
    key = "name"
    def wanted(self):
        result = set(details["manufacturer"]
                     for details in self.source['devices'].values()
                     if "manufacturer" in details)
        return  k:  "slug": slugify(k) 
                for k in result 
Regarding the device types, we use the foreign attribute linking a NetBox attribute to the synchronizer handling it.
class SyncDeviceTypes(Synchronizer):
    app = "dcim"
    table = "device_types"
    key = "model"
    foreign =  "manufacturer": SyncManufacturers 
    def wanted(self):
        result = set((details["manufacturer"], details["model"])
                     for details in self.source['devices'].values()
                     if "model" in details)
        return  k[1]: dict(manufacturer=k[0],
                           slug=slugify(k[1]))
                for k in result 
The wanted() method refers to the manufacturer using its key attribute. In this case, this is the manufacturer name.
>>> pprint(SyncManufacturers(**sync_args).wanted())
 'Cisco':  'slug': 'cisco' ,
 'Dell':  'slug': 'dell' ,
 'Juniper':  'slug': 'juniper' 
>>> pprint(SyncDeviceTypes(**sync_args).wanted())
 'ASR 9001':  'manufacturer': 'Cisco', 'slug': 'asr-9001' ,
 'Catalyst 2960G-48TC-L':  'manufacturer': 'Cisco',
                           'slug': 'catalyst-2960g-48tc-l' ,
 'MX10003':  'manufacturer': 'Juniper', 'slug': 'mx10003' ,
 'QFX10002-36Q':  'manufacturer': 'Juniper', 'slug': 'qfx10002-36q' ,
 'QFX10002-72Q':  'manufacturer': 'Juniper', 'slug': 'qfx10002-72q' ,
 'QFX5110-32Q':  'manufacturer': 'Juniper', 'slug': 'qfx5110-32q' ,
 'QFX5110-48S':  'manufacturer': 'Juniper', 'slug': 'qfx5110-48s' ,
 'QFX5200-32C':  'manufacturer': 'Juniper', 'slug': 'qfx5200-32c' ,
 'S4048-ON':  'manufacturer': 'Dell', 'slug': 's4048-on' ,
 'S6010-ON':  'manufacturer': 'Dell', 'slug': 's6010-on' 
The device roles are defined like this:
class SyncDeviceRoles(Synchronizer):
    app = "dcim"
    table = "device_roles"
    key = "name"
    def wanted(self):
        result = set(details["role"]
                     for details in self.source['devices'].values()
                     if "role" in details)
        return  k: dict(slug=slugify(k),
                        color="8bc34a")
                for k in result 

Synchronizing devices A device is mostly a name with references to a role, a model, a datacenter and a tenant. These references are declared as foreign keys using the synchronizers defined previously.
class SyncDevices(Synchronizer):
    app = "dcim"
    table = "devices"
    key = "name"
    foreign =  "device_role": SyncDeviceRoles,
               "device_type": SyncDeviceTypes,
               "site": SyncSites,
               "tenant": SyncTenants 
    remove_unused = 10
    def wanted(self):
        return  name: dict(device_role=details["role"],
                           device_type=details["model"],
                           site=details["datacenter"],
                           tenant="Network")
                for name, details in self.source['devices'].items()
                if  "datacenter", "model", "role"  <= set(details.keys()) 
The remove_unused attribute is a safety implemented to fail if we have to delete more than 10 devices: this may be the indication there is a bug somewhere, unless one of your datacenter suddenly caught fire.
>>> pprint(SyncDevices(**sync_args).wanted())
 'ad2-p6.sfo1.example.com':  'device_role': 'net_tor_oob_switch',
                             'device_type': 'Catalyst 2960G-48TC-L',
                             'site': 'sfo1',
                             'tenant': 'Network' ,
 'to1-p6.sfo1.example.com':  'device_role': 'net_tor_gpu_switch',
                             'device_type': 'QFX5110-48S',
                             'site': 'sfo1',
                             'tenant': 'Network' ,
[ ]

Synchronizing IP addresses The last step is to synchronize IP addresses. We do not attach them to a device.2 Instead, we specify the device names in the description of the IP address:
class SyncIPs(Synchronizer):
    app = "ipam"
    table = "ip-addresses"
    key = "address"
    foreign =  "tenant": SyncTenants 
    remove_unused = 1000
    def wanted(self):
        wanted =  
        for details in self.source['ips']:
            if details['ip'] in wanted:
                wanted[details['ip']]['description'] = \
                    f" details['device']  (and others)"
            else:
                wanted[details['ip']] = dict(
                    tenant="Network",
                    status="active",
                    dns_name="",        # information is present in DNS
                    description=f" details['device'] :  details['interface'] ",
                    role=None,
                    vrf=None)
        return wanted
There is a slight difficulty: NetBox allows duplicate IP addresses, so a simple lookup is not enough. In case of multiple matches, we choose the best by preferring those tagged with cmdb, then those already attached to an interface:
def get(self, key):
    """Grab IP address from NetBox."""
    # There may be duplicate. We need to grab the "best".
    results = super(Synchronizer, self).get(key)
    if len(results) == 0:
        return None
    if len(results) == 1:
        return results[0]
    scores = [0]*len(results)
    for idx, result in enumerate(results):
        if "cmdb" in result.tags:
            scores[idx] += 10
        if result.interface is not None:
            scores[idx] += 5
    return sorted(zip(scores, results),
                  reverse=True, key=lambda k: k[0])[0][1]

Getting the current and wanted states Each synchronizer is initialized with a reference to the Ansible module, a reference to a pynetbox s API object, the data contained in the provided YAML file and two empty dictionaries for the current and expected states:
source = yaml.safe_load(open(module.params['source']))
netbox = pynetbox.api(module.params['api'],
                      token=module.params['token'])
sync_args = dict(
    module=module,
    netbox=netbox,
    source=source,
    before= ,
    after= 
)
synchronizers = [synchronizer(**sync_args) for synchronizer in [
    SyncTags,
    SyncTenants,
    SyncSites,
    SyncManufacturers,
    SyncDeviceTypes,
    SyncDeviceRoles,
    SyncDevices,
    SyncIPs
]]
Each synchronizer has a prepare() method whose goal is to compute the current and wanted states. It returns True in case of a difference:
# Check what needs to be synchronized
try:
    for synchronizer in synchronizers:
        result['changed']  = synchronizer.prepare()
except AnsibleError as e:
    result['msg'] = e.message
    module.fail_json(**result)

Applying changes Back to the skeleton described in the previous article, the last step is to apply the changes if there is a difference between these states. Each synchronizer registers the current and wanted states in sync_args["before"][table] and sync_args["after"][table] where table is the name of the table for a given NetBox object type. The diff object is a bit elaborate as it is built table by table. This enables Ansible to display the name of each table before the diff representation:
# Compute the diff
if module._diff and result['changed']:
    result['diff'] = [
        dict(
            before_header=table,
            after_header=table,
            before=yaml.safe_dump(sync_args["before"][table]),
            after=yaml.safe_dump(sync_args["after"][table]))
        for table in sync_args["after"]
        if sync_args["before"][table] != sync_args["after"][table]
    ]
# Stop here if check mode is enabled or if no change
if module.check_mode or not result['changed']:
    module.exit_json(**result)
Each synchronizer also exposes a synchronize() method to apply changes and a cleanup() method to delete unwanted objects. Order is important due to the relation between the objects.
# Synchronize
for synchronizer in synchronizers:
    synchronizer.synchronize()
for synchronizer in synchronizers[::-1]:
    synchronizer.cleanup()
module.exit_json(**result)

The complete code is available on GitHub. Compared to using netbox.netbox collection, the logic is written in Python instead of trying to glue Ansible tasks together. I believe this is both more flexible and easier to read, notably when trying to delete outdated objects. While I did not test it, it should also be faster. An alternative would have been to reuse code from the netbox.netbox collection, as it contains similar primitives. Unfortunately, I didn t think of it until now.

  1. In my opinion, a good option for a source of truth is to use YAML files in a Git repository. You get versioning for free and people can get started with a text editor.
  2. This limitation is mostly due to laziness: we do not really care about this information. Our main motivation for putting IP addresses in NetBox is to keep track of the used IP addresses. However, if an IP address is already attached to an interface, we leave this association untouched.

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