Search Results: "Ian Jackson"

2 February 2024

Ian Jackson: UPS, the Useless Parcel Service; VAT and fees

I recently had the most astonishingly bad experience with UPS, the courier company. They severely damaged my parcels, and were very bad about UK import VAT, ultimately ending up harassing me on autopilot. The only thing that got their attention was my draft Particulars of Claim for intended legal action. Surprisingly, I got them to admit in writing that the disbursement fee they charge recipients alongside the actual VAT, is just something they made up with no legal basis. What happened Autumn last year I ordered some furniture from a company in Germany. This was to be shipped by them to me by courier. The supplier chose UPS. UPS misrouted one of the three parcels to Denmark. When everything arrived, it had been sat on by elephants. The supplier had to replace most of it, with considerable inconvenience and delay to me, and of course a loss to the supplier. But this post isn t mostly about that. This post is about VAT. You see, import VAT was due, because of fucking Brexit. UPS made a complete hash of collecting that VAT. Their computers can t issue coherent documents, their email helpdesk is completely useless, and their automated debt collection systems run along uninfluenced by any external input. The crazy, including legal threats and escalating late payment fees, continued even after I paid the VAT discrepancy (which I did despite them not yet having provided any coherent calculation for it). This kind of behaviour is a very small and mild version of the kind of things British Gas did to Lisa Ferguson, who eventually won substantial damages for harassment, plus 10K of costs. Having tried asking nicely, and sending stiff letters, I too threatened litigation. I would have actually started a court claim, but it would have included a claim under the Protection from Harassment Act. Those have to be filed under the Part 8 procedure , which involves sending all of the written evidence you re going to use along with the claim form. Collating all that would be a good deal of work, especially since UPS and ControlAccount didn t engage with me at all, so I had no idea which things they might actually dispute. So I decided that before issuing proceedings, I d send them a copy of my draft Particulars of Claim, along with an offer to settle if they would pay me a modest sum and stop being evil robots at me. Rather than me typing the whole tale in again, you can read the full gory details in the PDF of my draft Particulars of Claim. (I ve redacted the reference numbers). Outcome The draft Particulars finally got their attention. UPS sent me an offer: they agreed to pay me 50, in full and final settlement. That was close enough to my offer that I accepted it. I mostly wanted them to stop, and they do seem to have done so. And I ve received the 50. VAT calculation They also finally included an actual explanation of the VAT calculation. It s absurd, but it s not UPS s absurd:
The clearance was entered initially with estimated import charges of 400.03, consisting of 387.83 VAT, and 12.20 disbursement fee. This original entry regrettably did not include the freight cost for calculating the VAT, and as such when submitted for final entry the VAT value was adjusted to include this and an amended invoice was issued for an additional 39.84. HMRC calculate the amount against which VAT is raised using the value of goods, insurance and freight, however they also may apply a VAT adjustment figure. The VAT Adjustment is based on many factors (Incidental costs in regards to a shipment), which includes charge for currency conversion if the invoice does not list values in Sterling, but the main is due to the inland freight from airport of destination to the final delivery point, as this charge varies, for example, from EMA to Edinburgh would be 150, from EMA to Derby would be 1, so each year UPS must supply HMRC with all values incurred for entry build up and they give an average which UPS have to use on the entry build up as the VAT Adjustment. The correct calculation for the import charges is therefore as follows: Goods value divided by exchange rate 2,489.53 EUR / 1.1683 = 2,130.89 GBP Duty: Goods value plus freight (%) 2,130.89 GBP + 5% = 2,237.43 GBP. That total times the duty rate. X 0 % = 0 GBP VAT: Goods value plus freight (100%) 2,130.89 GBP + 0 = 2,130.89 GBP That total plus duty and VAT adjustment 2,130.89 GBP + 0 GBP + 7.49 GBP = 2,348.08 GBP. That total times 20% VAT = 427.67 GBP As detailed above we must confirm that the final VAT charges applied to the shipment were correct, and that no refund of this is therefore due.
This looks very like HMRC-originated nonsense. If only they had put it on the original bills! It s completely ridiculous that it took four months and near-litigation to obtain it. Disbursement fee One more thing. UPS billed me a 12 disbursement fee . When you import something, there s often tax to pay. The courier company pays that to the government, and the consignee pays it to the courier. Usually the courier demands it before final delivery, since otherwise they end up having to chase it as a debt. It is common for parcel companies to add a random fee of their own. As I note in my Particulars, there isn t any legal basis for this. In my own offer of settlement I proposed that UPS should:
State under what principle of English law (such as, what enactment or principle of Common Law), you levy the disbursement fee (or refund it).
To my surprise they actually responded to this in their own settlement letter. (They didn t, for example, mention the harassment at all.) They said (emphasis mine):
A disbursement fee is a fee for amounts paid or processed on behalf of a client. It is an established category of charge used by legal firms, amongst other companies, for billing of various ancillary costs which may be incurred in completion of service. Disbursement fees are not covered by a specific law, nor are they legally prohibited. Regarding UPS disbursement fee this is an administrative charge levied for the use of UPS deferment account to prepay import charges for clearance through CDS. This charge would therefore be billed to the party that is responsible for the import charges, normally the consignee or receiver of the shipment in question. The disbursement fee as applied is legitimate, and as you have stated is a commonly used and recognised charge throughout the courier industry, and I can confirm that this was charged correctly in this instance.
On UPS s analysis, they can just make up whatever fee they like. That is clearly not right (and I don t even need to refer to consumer protection law, which would also make it obviously unlawful). And, that everyone does it doesn t make it lawful. There are so many things that are ubiquitous but unlawful, especially nowadays when much of the legal system - especially consumer protection regulators - has been underfunded to beyond the point of collapse. Next time this comes up I might have a go at getting the fee back. (Obviously I ll have to pay it first, to get my parcel.) ParcelForce and Royal Mail I think this analysis doesn t apply to ParcelForce and (probably) Royal Mail. I looked into this in 2009, and I found that Parcelforce had been given the ability to write their own private laws: Schemes made under section 89 of the Postal Services Act 2000. This is obviously ridiculous but I think it was the law in 2009. I doubt the intervening governments have fixed it. Furniture Oh, yes, the actual furniture. The replacements arrived intact and are great :-).

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28 December 2023

Antonio Terceiro: Debian CI: 10 years later

It was 2013, and I was on a break from work between Christmas and New Year of 2013. I had been working at Linaro for well over a year, on the LAVA project. I was living and breathing automated testing infrastructure, mostly for testing low-level components such as kernels and bootloaders, on real hardware. At this point I was also a Debian contributor for quite some years, and had become an official project members two years prior. Most of my involvement was in the Ruby team, where we were already consistently running upstream test suites during package builds. During that break, I put these two contexts together, and came to the conclusion that Debian needed a dedicated service that would test the contents of the Debian archive. I was aware of the existance of autopkgtest, and started working on a very simple service that would later become Debian CI. In January 2014, debci was initially announced on that month's Misc Developer News, and later uploaded to Debian. It's been continuously developed for the last 10 years, evolved from a single shell script running tests in a loop into a distributed system with 47 geographically-distributed machines as of writing this piece, became part of the official Debian release process gating migrations to testing, had 5 Summer of Code and Outrechy interns working on it, and processed beyond 40 million test runs. In there years, Debian CI has received contributions from a lot of people, but I would like to give special credits to the following:

4 December 2023

Ian Jackson: Don t use apt-get source; use dgit

tl;dr: If you are a Debian user who knows git, don t work with Debian source packages. Don t use apt source, or dpkg-source. Instead, use dgit and work in git. Also, don t use: VCS links on official Debian web pages, debcheckout, or Debian s (semi-)official gitlab, Salsa. These are suitable for Debian experts only; for most people they can be beartraps. Instead, use dgit. > Struggling with Debian source packages? A friend of mine recently asked for help on IRC. They re an experienced Debian administrator and user, and were trying to: make a change to a Debian package; build and install and run binary packages from it; and record that change for their future self, and their colleagues. They ended up trying to comprehend quilt. quilt is an ancient utility for managing sets of source code patches, from well before the era of modern version control. It has many strange behaviours and footguns. Debian s ancient and obsolete tarballs-and-patches source package format (which I designed the initial version of in 1993) nowadays uses quilt, at least for most packages. You don t want to deal with any of this nonsense. You don t want to learn quilt, and suffer its misbehaviours. You don t want to learn about Debian source packages and wrestle dpkg-source. Happily, you don t need to. Just use dgit One of dgit s main objectives is to minimise the amount of Debian craziness you need to learn. dgit aims to empower you to make changes to the software you re running, conveniently and with a minimum of fuss. You can use dgit to get the source code to a Debian package, as a git tree, with dgit clone (and dgit fetch). The git tree can be made into a binary package directly. The only things you really need to know are:
  1. By default dgit fetches from Debian unstable, the main work-in-progress branch. You may want something like dgit clone PACKAGE bookworm,-security (yes, with a comma).
  2. You probably want to edit debian/changelog to make your packages have a different version number.
  3. To build binaries, run dpkg-buildpackage -uc -b.
  4. Debian package builds are often disastrously messsy: builds might modify source files; and the official debian/rules clean can be inadequate, or crazy. Always commit before building, and use git clean and git reset --hard instead of running clean rules from the package.
Don t try to make a Debian source package. (Don t read the dpkg-source manual!) Instead, to preserve and share your work, use the git branch. dgit pull or dgit fetch can be used to get updates. There is a more comprehensive tutorial, with example runes, in the dgit-user(7) manpage. (There is of course complete reference documentation, but you don t need to bother reading it.) Objections But I don t want to learn yet another tool One of dgit s main goals is to save people from learning things you don t need to. It aims to be straightforward, convenient, and (so far as Debian permits) unsurprising. So: don t learn dgit. Just run it and it will be fine :-). Shouldn t I be using official Debian git repos? Absolutely not. Unless you are a Debian expert, these can be terrible beartraps. One possible outcome is that you might build an apparently working program but without the security patches. Yikes! I discussed this in more detail in 2021 in another blog post plugging dgit. Gosh, is Debian really this bad? Yes. On behalf of the Debian Project, I apologise. Debian is a very conservative institution. Change usually comes very slowly. (And when rapid or radical change has been forced through, the results haven t always been pretty, either technically or socially.) Sadly this means that sometimes much needed change can take a very long time, if it happens at all. But this tendency also provides the stability and reliability that people have come to rely on Debian for. I m a Debian maintainer. You tell me dgit is something totally different! dgit is, in fact, a general bidirectional gateway between the Debian archive and git. So yes, dgit is also a tool for Debian uploaders. You should use it to do your uploads, whenever you can. It s more convenient and more reliable than git-buildpackage and dput runes, and produces better output for users. You too can start to forget how to deal with source packages! A full treatment of this is beyond the scope of this blog post.

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30 November 2023

Russell Coker: Links November 2023

The Long Now has an insightful article about air quality [1]. Every country needs food labelling laws like Mexico has [2]. Also we need to abolish the investor state tribunals, companies should just accept local laws and obey them or be treated in the same way as pirates on the high seas. Ian Jackson wrote a good post about conference policies regarding Covid19 [3]. We really need to do more about this, conservatives like to imagine that it s gone away but people are still getting sick and dying of it. John Goerzen wrote an informative article about air gaps and ways they can be part of a useful and usable security system [4]. This YouTube video has a good introduction to LLMs (Large Languge Models) for machine learning [5]. This eye tracker is interesting technology [6]. The video shows it being used for MS Flight Simulator but it can be used for other things. Unfortunately the price of about $550 Australian puts it out of range of a lot of free software work. I think this would be good for tracking the user FOR THEIR BENEFIT so that notifications won t be delivered when the user is concentrating. This ABC article about the risk of a past Covid19 infection exacerbating or accelerating Parkinson s or Alzheimer s is a worry [7]. Sam Hartman wrote an insightful blog post about AI safety, consent, and discussions of sex [8].

26 November 2023

Ian Jackson: Hacking my filter coffee machine

I hacked my coffee machine to let me turn it on from upstairs in bed :-). Read on for explanation, circuit diagrams, 3D models, firmware source code, and pictures. Background: the Morphy Richards filter coffee machine I have a Morphy Richards filter coffee machine. It makes very good coffee. But the display and firmware are quite annoying: Also, I m lazy and wanted to be able to cause coffee to exist from upstairs in bed, without having to make a special trip down just to turn the machine on. Planning My original feeling was I can t be bothered dealing with the coffee machine innards so I thought I would make a mechanical contraption to physically press the coffee machine s on button. I could have my contraption press the button to turn the machine on (timed, or triggered remotely), and then periodically in pairs to reset the 25-minute keep-warm timer. But a friend pointed me at a blog post by Andy Bradford, where Andy recounts modifying his coffee machine, adding an ESP8266 and connecting it to his MQTT-based Home Assistant setup. I looked at the pictures and they looked very similar to my machine. I decided to take a look inside. Inside the Morphy Richards filter coffee machine My coffee machine seemed to be very similar to Andy s. His disassembly report was very helpful. Inside I found the high-voltage parts with the heating elements, and the front panel with the display and buttons. I spent a while poking about, masuring things, and so on. Unexpected electrical hazard At one point I wanted to use my storage oscilloscope to capture the duration and amplitude of the beep signal. I needed to connect the scope ground to the UI board s ground plane, but then when I switched the coffee machine on at the wall socket, it tripped the house s RCD. It turns out that the low voltage UI board is coupled to the mains. In my setting, there s an offset of about 8V between the UI board ground plane, and true earth. (In my house the neutral is about 2-3V away from true earth.) This alarmed me rather. To me, this means that my modifications needed to still properly electrically isolate everything connected to the UI board from anything external to the coffee machine s housing. In Andy s design, I think the internal UI board ground plane is directly brought out to an external USB-A connector. This means that if there were a neutral fault, the USB-A connector would be at live potential, possibly creating an electrocution or fire hazard. I made a comment in Andy Bradford s blog, reporting this issue, but it doesn t seem to have appeared. This is all quite alarming. I hope Andy is OK! Design approach I don t have an MQTT setup at home, or an installation of Home Assistant. I didn t feel like adding a lot of complicated software to my life, if I could avoid it. Nor did I feel like writing a web UI myself. I ve done that before, but I m lazy and in this case my requirements were quite modest. Also, the need for electrical isolation would further complicate any attempt to do something sophisticated (that could, for example, sense the state of the coffee machine). I already had a Tasmota-based cloud-free smart plug, which controls the fairy lights on our gazebo. We just operate that through its web UI. So, I decided I would add a small and stupid microcontroller. The microcontroller would be powered via a smart plug and an off-the-shelf USB power supply. The microcontroller would have no inputs. It would simply simulate an on button press once at startup, and thereafter two presses every 24 minutes. After the 4th double press the microcontroller would stop, leaving the coffee machine to time out itself, after a total period of about 2h. Implementation - hardware I used a DigiSpark board with an ATTiny85. One of the GPIOs is connected to an optoisolator, whose output transistor is wired across the UI board s on button. circuit diagram; board layout diagram; (click for diagram scans as pdfs). The DigiSpark has just a USB tongue, which is very wobbly in a normal USB socket. I designed a 3D printed case which also had an approximation of the rest of the USB A plug. The plug is out of spec; our printer won t go fine enough - and anyway, the shield is supposed to be metal, not fragile plastic. But it fit in the USB PSU I was using, satisfactorily if a bit stiffly, and also into the connector for programming via my laptop. Inside the coffee machine, there s the boundary between the original, coupled to mains, UI board, and the isolated low voltage of the microcontroller. I used a reasonably substantial cable to bring out the low voltage connection, past all the other hazardous innards, to make sure it stays isolated. I added a drain power supply resistor on another of the GPIOs. This is enabled, with a draw of about 30mA, when the microcontroller is soon going to off / on cycle the coffee machine. That reduces the risk that the user will turn off the smart plug, and turn off the machine, but that the microcontroller turns the coffee machine back on again using the remaining power from USB PSU. Empirically in my setup it reduces the time from smart plug off to microcontroller stops from about 2-3s to more like 1s. Optoisolator board (inside coffee machine) pictures (Click through for full size images.) optoisolator board, front; optoisolator board, rear; optoisolator board, fitted. Microcontroller board (in USB-plug-ish housing) pictures microcontroller board, component side; microcontroller board, wiring side, part fitted; microcontroller in USB-plug-ish housing. Implementation - software I originally used the Arduino IDE, writing my program in C. I had a bad time with that and rewrote it in Rust. The firmware is in a repository on Debian s gitlab Results I can now cause the coffee to start, from my phone. It can be programmed more than 12h in advance. And it stays warm until we ve drunk it. UI is worse There s one aspect of the original Morphy Richards machine that I haven t improved: the user interface is still poor. Indeed, it s now even worse: To turn the machine on, you probably want to turn on the smart plug instead. Unhappily, the power button for that is invisible in its installed location. In particular, in the usual case, if you want to turn it off, you should ideally turn off both the smart plug (which can be done with the button on it) and the coffee machine itself. If you forget to turn off the smart plug, the machine can end up being turned on, very briefly, a handful of times, over the next hour or two. Epilogue We had used the new features a handful of times when one morning the coffee machine just wouldn t make coffee. The UI showed it turning on, but it wouldn t get hot, so no coffee. I thought oh no, I ve broken it! But, on investigation, I found that the machine s heating element was open circuit (ie, completely broken). I didn t mess with that part. So, hooray! Not my fault. Probably, just being inverted a number of times and generally lightly jostled, had precipitated a latent fault. The machine was a number of years old. Happily I found a replacement, identical, machine, online. I ve transplanted my modification and now it all works well. Bonus pictures (Click through for full size images.) probing the innards; machine base showing new cable route.
edited 2023-11-26 14:59 UTC in an attempt to fix TOC links


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25 November 2023

Andrew Cater: Afternoon talks - MiniDebConf ARM Cambridge - Day 1

A great talk on SteamOS progress to effective boot loaders for atomic OS updates.How to produce something that will allow instant updates and instant fallbacks when updating a whole OS image - lots of explanation - and it's good when three or four people who are directly interested in problems and solutions round, for example, Secure Boot are in the room.Jessica Clarke on CHERI, Morello and security protections in hardware, software and programming hardware which has verifiable pointers and routines. A couple of flourishes which had the room breaking out in applause.Roberto Sanchez and Santiago Rincon on suggestions for LTS and ways forward. The presentation very clearly set out what LTS is, is not, and maybe should be.Last presentation of the day was from Ian Jackson on a potential change to git based working and tagging. Then lots of chasing around to get people out of the building. Thanks very much to the Arm personnel, especially the security staff who have been helpful throughout the day with getting us all in and out

Thanks to all involved with Arm, Codethink and Pexip for hosting and sponsorship without which this would not have been possible.

22 October 2023

Ian Jackson: DigiSpark (ATTiny85) - Arduino, C, Rust, build systems

Recently I completed a small project, including an embedded microcontroller. For me, using the popular Arduino IDE, and C, was a mistake. The experience with Rust was better, but still very exciting, and not in a good way. Here follows the rant. Introduction In a recent project (I ll write about the purpose, and the hardware in another post) I chose to use a DigiSpark board. This is a small board with a USB-A tongue (but not a proper plug), and an ATTiny85 microcontroller, This chip has 8 pins and is quite small really, but it was plenty for my application. By choosing something popular, I hoped for convenient hardware, and an uncomplicated experience. Convenient hardware, I got. Arduino IDE The usual way to program these boards is via an IDE. I thought I d go with the flow and try that. I knew these were closely related to actual Arduinos and saw that the IDE package arduino was in Debian. But it turns out that the Debian package s version doesn t support the DigiSpark. (AFAICT from the list it offered me, I m not sure it supports any ATTiny85 board.) Also, disturbingly, its board manager seemed to be offering to install board support, suggesting it would download stuff from the internet and run it. That wouldn t be acceptable for my main laptop. I didn t expect to be doing much programming or debugging, and the project didn t have significant security requirements: the chip, in my circuit, has only a very narrow ability do anything to the real world, and no network connection of any kind. So I thought it would be tolerable to do the project on my low-security video laptop . That s the machine where I m prepared to say yes to installing random software off the internet. So I went to the upstream Arduino site and downloaded a tarball containing the Arduino IDE. After unpacking that in /opt it ran and produced a pointy-clicky IDE, as expected. I had already found a 3rd-party tutorial saying I needed to add a magic URL (from the DigiSpark s vendor) in the preferences. That indeed allowed it to download a whole pile of stuff. Compilers, bootloader clients, god knows what. However, my tiny test program didn t make it to the board. Half-buried in a too-small window was an error message about the board s bootloader ( Micronucleus ) being too new. The boards I had came pre-flashed with micronucleus 2.2. Which is hardly new, But even so the official Arduino IDE (or maybe the DigiSpark s board package?) still contains an old version. So now we have all the downsides of curl bash-ware, but we re lacking the it s up to date and it just works upsides. Further digging found some random forum posts which suggested simply downloading a newer micronucleus and manually stuffing it into the right place: one overwrites a specific file, in the middle the heaps of stuff that the Arduino IDE s board support downloader squirrels away in your home directory. (In my case, the home directory of the untrusted shared user on the video laptop,) So, whatever . I did that. And it worked! Having demo d my ability to run code on the board, I set about writing my program. Writing C again The programming language offered via the Arduino IDE is C. It s been a little while since I started a new thing in C. After having spent so much of the last several years writing Rust. C s primitiveness quickly started to grate, and the program couldn t easily be as DRY as I wanted (Don t Repeat Yourself, see Wilson et al, 2012, 4, p.6). But, I carried on; after all, this was going to be quite a small job. Soon enough I had a program that looked right and compiled. Before testing it in circuit, I wanted to do some QA. So I wrote a simulator harness that #included my Arduino source file, and provided imitations of the few Arduino library calls my program used. As an side advantage, I could build and run the simulation on my main machine, in my normal development environment (Emacs, make, etc.). The simulator runs confirmed the correct behaviour. (Perhaps there would have been some more faithful simulation tool, but the Arduino IDE didn t seem to offer it, and I wasn t inclined to go further down that kind of path.) So I got the video laptop out, and used the Arduino IDE to flash the program. It didn t run properly. It hung almost immediately. Some very ad-hoc debugging via led-blinking (like printf debugging, only much worse) convinced me that my problem was as follows: Arduino C has 16-bit ints. My test harness was on my 64-bit Linux machine. C was autoconverting things (when building for the micrcocontroller). The way the Arduino IDE ran the compiler didn t pass the warning options necessary to spot narrowing implicit conversions. Those warnings aren t the default in C in general because C compilers hate us all for compatibility reasons. I don t know why those warnings are not the default in the Arduino IDE, but my guess is that they didn t want to bother poor novice programmers with messages from the compiler explaining how their program is quite possibly wrong. After all, users don t like error messages so we shouldn t report errors. And novice programmers are especially fazed by error messages so it s better to just let them struggle themselves with the arcane mysteries of undefined behaviour in C? The Arduino IDE does offer a dropdown for compiler warnings . The default is None. Setting it to All didn t produce anything about my integer overflow bugs. And, the output was very hard to find anyway because the log window has a constant stream of strange messages from javax.jmdns, with hex DNS packet dumps. WTF. Other things that were vexing about the Arduino IDE: it has fairly fixed notions (which don t seem to be documented) about how your files and directories ought to be laid out, and magical machinery for finding things you put nearby its sketch (as it calls them) and sticking them in its ear, causing lossage. It has a tendency to become confused if you edit files under its feet (e.g. with git checkout). It wasn t really very suited to a workflow where principal development occurs elsewhere. And, important settings such as the project s clock speed, or even the target board, or the compiler warning settings to use weren t stored in the project directory along with the actual code. I didn t look too hard, but I presume they must be in a dotfile somewhere. This is madness. Apparently there is an Arduino CLI too. But I was already quite exasperated, and I didn t like the idea of going so far off the beaten path, when the whole point of using all this was to stay with popular tooling and share fate with others. (How do these others cope? I have no idea.) As for the integer overflow bug: I didn t seriously consider trying to figure out how to control in detail the C compiler options passed by the Arduino IDE. (Perhaps this is possible, but not really documented?) I did consider trying to run a cross-compiler myself from the command line, with appropriate warning options, but that would have involved providing (or stubbing, again) the Arduino/DigiSpark libraries (and bugs could easily lurk at that interface). Instead, I thought, if only I had written the thing in Rust . But that wasn t possible, was it? Does Rust even support this board? Rust on the DigiSpark I did a cursory web search and found a very useful blog post by Dylan Garrett. This encouraged me to think it might be a workable strategy. I looked at the instructions there. It seemed like I could run them via the privsep arrangement I use to protect myself when developing using upstream cargo packages from crates.io. I got surprisingly far surprisingly quickly. It did, rather startlingly, cause my rustup to download a random recent Nightly Rust, but I have six of those already for other Reasons. Very quickly I got the trinket LED blink example, referenced by Dylan s blog post, to compile. Manually copying the file to the video laptop allowed me to run the previously-downloaded micronucleus executable and successfully run the blink example on my board! I thought a more principled approach to the bootloader client might allow a more convenient workflow. I found the upstream Micronucleus git releases and tags, and had a look over its source code, release dates, etc. It seemed plausible, so I compiled v2.6 from source. That was a success: now I could build and install a Rust program onto my board, from the command line, on my main machine. No more pratting about with the video laptop. I had got further, more quickly, with Rust, than with the Arduino IDE, and the outcome and workflow was superior. So, basking in my success, I copied the directory containing the example into my own project, renamed it, and adjusted the path references. That didn t work. Now it didn t build. Even after I copied about .cargo/config.toml and rust-toolchain.toml it didn t build, producing a variety of exciting messages, depending what precisely I tried. I don t have detailed logs of my flailing: the instructions say to build it by cd ing to the subdirectory, and, given that what I was trying to do was to not follow those instructions, it didn t seem sensible to try to prepare a proper repro so I could file a ticket. I wasn t optimistic about investigating it more deeply myself: I have some experience of fighting cargo, and it s not usually fun. Looking at some of the build control files, things seemed quite complicated. Additionally, not all of the crates are on crates.io. I have no idea why not. So, I would need to supply local copies of them anyway. I decided to just git subtree add the avr-hal git tree. (That seemed better than the approach taken by the avr-hal project s cargo template, since that template involve a cargo dependency on a foreign git repository. Perhaps it would be possible to turn them into path dependencies, but given that I had evidence of file-location-sensitive behaviour, which I didn t feel like I wanted to spend time investigating, using that seems like it would possibly have invited more trouble. Also, I don t like package templates very much. They re a form of clone-and-hack: you end up stuck with whatever bugs or oddities exist in the version of the template which was current when you started.) Since I couldn t get things to build outside avr-hal, I edited the example, within avr-hal, to refer to my (one) program.rs file outside avr-hal, with a #[path] instruction. That s not pretty, but it worked. I also had to write a nasty shell script to work around the lack of good support in my nailing-cargo privsep tool for builds where cargo must be invoked in a deep subdirectory, and/or Cargo.lock isn t where it expects, and/or the target directory containing build products is in a weird place. It also has to filter the output from cargo to adjust the pathnames in the error messages. Otherwise, running both cd A; cargo build and cd B; cargo build from a Makefile produces confusing sets of error messages, some of which contain filenames relative to A and some relative to B, making it impossible for my Emacs to reliably find the right file. RIIR (Rewrite It In Rust) Having got my build tooling sorted out I could go back to my actual program. I translated the main program, and the simulator, from C to Rust, more or less line-by-line. I made the Rust version of the simulator produce the same output format as the C one. That let me check that the two programs had the same (simulated) behaviour. Which they did (after fixing a few glitches in the simulator log formatting). Emboldened, I flashed the Rust version of my program to the DigiSpark. It worked right away! RIIR had caused the bug to vanish. Of course, to rewrite the program in Rust, and get it to compile, it was necessary to be careful about the types of all the various integers, so that s not so surprising. Indeed, it was the point. I was then able to refactor the program to be a bit more natural and DRY, and improve some internal interfaces. Rust s greater power, compared to C, made those cleanups easier, so making them worthwhile. However, when doing real-world testing I found a weird problem: my timings were off. Measured, the real program was too fast by a factor of slightly more than 2. A bit of searching (and searching my memory) revealed the cause: I was using a board template for an Adafruit Trinket. The Trinket has a clock speed of 8MHz. But the DigiSpark runs at 16.5MHz. (This is discussed in a ticket against one of the C/C++ libraries supporting the ATTiny85 chip.) The Arduino IDE had offered me a choice of clock speeds. I have no idea how that dropdown menu took effect; I suspect it was adding prelude code to adjust the clock prescaler. But my attempts to mess with the CPU clock prescaler register by hand at the start of my Rust program didn t bear fruit. So instead, I adopted a bodge: since my code has (for code structure reasons, amongst others) only one place where it dealt with the underlying hardware s notion of time, I simply changed my delay function to adjust the passed-in delay values, compensating for the wrong clock speed. There was probably a more principled way. For example I could have (re)based my work on either of the two unmerged open MRs which added proper support for the DigiSpark board, rather than abusing the Adafruit Trinket definition. But, having a nearly-working setup, and an explanation for the behaviour, I preferred the narrower fix to reopening any cans of worms. An offer of help As will be obvious from this posting, I m not an expert in dev tools for embedded systems. Far from it. This area seems like quite a deep swamp, and I m probably not the person to help drain it. (Frankly, much of the improvement work ought to be done, and paid for, by hardware vendors.) But, as a full Member of the Debian Project, I have considerable gatekeeping authority there. I also have much experience of software packaging, build systems, and release management. If anyone wants to try to improve the situation with embedded tooling in Debian, and is willing to do the actual packaging work. I would be happy to advise, and to review and sponsor your contributions. An obvious candidate: it seems to me that micronucleus could easily be in Debian. Possibly a DigiSpark board definition could be provided to go with the arduino package. Unfortunately, IMO Debian s Rust packaging tooling and workflows are very poor, and the first of my suggestions for improvement wasn t well received. So if you need help with improving Rust packages in Debian, please talk to the Debian Rust Team yourself. Conclusions Embedded programming is still rather a mess and probably always will be. Embedded build systems can be bizarre. Documentation is scant. You re often expected to download board support packages full of mystery binaries, from the board vendor (or others). Dev tooling is maddening, especially if aimed at novice programmers. You want version control? Hermetic tracking of your project s build and install configuration? Actually to be told by the compiler when you write obvious bugs? You re way off the beaten track. As ever, Free Software is under-resourced and the maintainers are often busy, or (reasonably) have other things to do with their lives. All is not lost Rust can be a significantly better bet than C for embedded software: The Rust compiler will catch a good proportion of programming errors, and an experienced Rust programmer can arrange (by suitable internal architecture) to catch nearly all of them. When writing for a chip in the middle of some circuit, where debugging involves staring an LED or a multimeter, that s precisely what you want. Rust embedded dev tooling was, in this case, considerably better. Still quite chaotic and strange, and less mature, perhaps. But: significantly fewer mystery downloads, and significantly less crazy deviations from the language s normal build system. Overall, less bad software supply chain integrity. The ATTiny85 chip, and the DigiSpark board, served my hardware needs very well. (More about the hardware aspects of this project in a future posting.)

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30 September 2023

Ian Jackson: DKIM: rotate and publish your keys

If you are an email system administrator, you are probably using DKIM to sign your outgoing emails. You should be rotating the key regularly and automatically, and publishing old private keys. I have just released dkim-rotate 1.0; dkim-rotate is a tool to do this key rotation and publication. If you are an email user, your email provider ought to be doing this. If this is not done, your emails are non-repudiable , meaning that if they are leaked, anyone (eg, journalists, haters) can verify that they are authentic, and prove that to others. This is not desirable (for you). Non-repudiation of emails is undesirable This problem was described at some length in Matthew Green s article Ok Google: please publish your DKIM secret keys. Avoiding non-repudiation sounds a bit like lying. After all, I m advising creating a situation where some people can t verify that something is true, even though it is. So I m advocating casting doubt. Crucially, though, it s doubt about facts that ought to be private. When you send an email, that s between you and the recipient. Normally you don t intend for anyone, anywhere, who happens to get a copy, to be able to verify that it was really you that sent it. In practical terms, this verifiability has already been used by journalists to verify stolen emails. Associated Press provide a verification tool. Advice for all email users As a user, you probably don t want your emails to be non-repudiable. (Other people might want to be able to prove you sent some email, but your email system ought to serve your interests, not theirs.) So, your email provider ought to be rotating their DKIM keys, and publishing their old ones. At a rough guess, your provider probably isn t :-(. How to tell by looking at email headers A quick and dirty way to guess is to have a friend look at the email headers of a message you sent. (It is important that the friend uses a different email provider, since often DKIM signatures are not applied within a single email system.) If your friend sees a DKIM-Signature header then the message is DKIM signed. If they don t, then it wasn t. Most email traversing the public internet is DKIM signed nowadays; so if they don t see the header probably they re not looking using the right tools, or they re actually on the same email system as you. In messages signed by a system running dkim-rotate, there will also be a header about the key rotation, to notify potential verifiers of the situation. Other systems that avoid non-repudiation-through-DKIM might do something similar. dkim-rotate s header looks like this:
DKIM-Signature-Warning: NOTE REGARDING DKIM KEY COMPROMISE
 https://www.chiark.greenend.org.uk/dkim-rotate/README.txt
 https://www.chiark.greenend.org.uk/dkim-rotate/ae/aeb689c2066c5b3fee673355309fe1c7.pem
But an email system might do half of the job of dkim-rotate: regularly rotating the key would cause the signatures of old emails to fail to verify, which is a good start. In that case there probably won t be such a header. Testing verification of new and old messages You can also try verifying the signatures. This isn t entirely straightforward, especially if you don t have access to low-level mail tooling. Your friend will need to be able to save emails as raw whole headers and body, un-decoded, un-rendered. If your friend is using a traditional Unix mail program, they should save the message as an mbox file. Otherwise, ProPublica have instructions for attaching and transferring and obtaining the raw email. (Scroll down to How to Check DKIM and ARC .) Checking that recent emails are verifiable Firstly, have your friend test that they can in fact verify a DKIM signature. This will demonstrate that the next test, where the verification is supposed to fail, is working properly and fails for the right reasons. Send your friend a test email now, and have them do this on a Linux system:
    # save the message as test-email.mbox
    apt install libmail-dkim-perl # or equivalent on another distro
    dkimproxy-verify <test-email.mbox
You should see output containing something like this:
    originator address: ijackson@chiark.greenend.org.uk
    signature identity: @chiark.greenend.org.uk
    verify result: pass
    ...
If the output ontains verify result: fail (body has been altered) then probably your friend didn t manage to faithfully save the unalterered raw message. Checking old emails cannot be verified When you both have that working, have your friend find an older email of yours, from (say) month ago. Perform the same steps. Hopefully they will see something like this:
    originator address: ijackson@chiark.greenend.org.uk
    signature identity: @chiark.greenend.org.uk
    verify result: fail (bad RSA signature)
or maybe
    verify result: invalid (public key: not available)
This indicates that this old email can no longer be verified. That s good: it means that anyone who steals a copy, can t verify it either. If it s leaked, the journalist who receives it won t know it s genuine and unmodified; they should then be suspicious. If your friend sees verify result: pass, then they have verified that that old email of yours is genuine. Anyone who had a copy of the mail can do that. This is good for email thieves, but not for you. For email admins: announcing dkim-rotate 1.0 I have been running dkim-rotate 0.4 on my infrastructure, since last August. and I had entirely forgotten about it: it has run flawlessly for a year. I was reminded of the topic by seeing DKIM in other blog posts. Obviously, it is time to decreee that dkim-rotate is 1.0. If you re a mail system administrator, your users are best served if you use something like dkim-rotate. The package is available in Debian stable, and supports Exim out of the box, but other MTAs should be easy to support too, via some simple ad-hoc scripting. Limitation of this approach Even with this key rotation approach, emails remain nonrepudiable for a short period after they re sent - typically, a few days. Someone who obtains a leaked email very promptly, and shows it to the journalist (for example) right away, can still convince the journalist. This is not great, but at least it doesn t apply to the vast bulk of your email archive. There are possible email protocol improvements which might help, but they re quite out of scope for this article.
Edited 2023-10-01 00:20 +01:00 to fix some grammar


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Russell Coker: Links September 2023

Interesting article in Wired about adversarial attacks on ML systems to get them to do things that they are explicitely programmed not to do such as describe how to make illegal drugs [1]. The most interesting part of this is that the attacks work on most GPT systems which is probably due to the similar data used to train them. Vice has an interesting article about the Danish Synthetic Party , a political partyled by an AI [2]. Citizens can vote for candidates who will try to get laws passed that match the AI generated goals, there is no option of voting for an AI character. The policies they are advocating for are designed to appeal to the 20% of Danes who don t vote. They are also trying to inspire similar parties in other countries. I think this has the potential to improve democracy. Vice reports that in 2021 a man tried to assasinate the Queen of England with inspiration from Star Wars and an AI chat bot [3]. While someone who wants to be a real-life Sith is probably going to end up doing something bad we still don t want to have chat bots encourage it. Bruce Schneier wrote an interesting article about milestones for AI involvement in the political process [4]. Sam Varghese wrote an interesting article about the allegations that India is following the example of Saudi Arabia and assasinating people in other countries who disagree with their government [5]. We need to stop this. Ian Jackson wrote an interesting blog post advocating that DKIM PRIVATE keys be rotated and PUBLISHED [6]. The idea is that if a hostile party gets access to the mailbox of someone who received private email from you then in the normal DKIM setup of keys never changing they can prove that the email is authentic when they leak it. While if you mail server publishes the old keys as Ian advocates then the hostile party can t prove that you sent the email in question as anyone could have forged a signature. Anything that involves publishing a private key gets an immediate negative reaction but I can t fault the logic here.

31 August 2023

Ian Jackson: Conferences take note: the pandemic is not over

Many people seem to be pretending that the pandemic is over. It isn t. People are still getting Covid, becoming sick, and even in some cases becoming disabled. People s plans are still being disrupted. Vulnerable people are still hiding. Conference organisers: please make robust Covid policies, publish them early, and enforce them. And, clearly set expectations for your attendees. Attendees: please don t be the superspreader. Two conferences This year I have attended a number of in-person events. For Eastercon I chose to participate online, remotely. This turns out to have been a very good decision. At least a quarter of attendees got Covid. At BiCon we had about 300 attendees. I m not aware of any Covid cases. Part of the difference between the two may have been in the policies. BiCon s policy was rather more robust. Unlike Eastercon s it had a much better refund policy for people who got Covid and therefore shouldn t come; also BiCon asked attendees to actually show evidence of a negative test. Another part of the difference will have been the venue. The NTU buildings we used at BiCon were modern and well ventilated. But, I think the biggest difference was attendees' attitudes. BiCon attendees are disproportionately likely (compared to society at large) to have long term medical conditions. And the cultural norms are to value and protect those people. Conversely, in my experience, a larger proportion of Eastercon attendees don t always have the same level of consideration. I don t want to give details, but I have reliable reports of quite reprehensible behaviour by some attendees - even members of the convention volunteer staff. Policies Your conference should IMO at the very least: The rules should be published very early, so that people can see them, and decide if they want to go, before they have to book anything. Don t recommend that people don t spread disease Most of the things that attendees can do to about Covid primarily protect others, rather than themselves. Making those things recommendations or advice is grossly unfair. You re setting up an arsehole filter: nice people will want to protect others, but less public spirited people will tell themselves it s only a recommendation. Make the rules mandatory. But won t we be driving people away ? If you don t have a robust Covid policy, you are already driving people away. And the people who won t come because of reasonable measures like I ve asked for above, are dickheads. You don t want them putting your other attendees at risk. And probably they re annoying in other ways too. Example of something that is not OK Yesterday (2023-08-30 13:44 UTC), less than two weeks before the conference, Debconf 23 s Covid policy still looked like you see below. Today there is a policy, but it is still weak.
Edited 2023-09-01 00:58 +01:00 to fix the link to the Debconf policy.


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25 August 2023

Ian Jackson: I cycled to all the villages in alphabetical order

This last weekend I completed a bike rides project I started during the first Covid lockdown in 2020: I ve cycled to every settlement (and radio observatory) within 20km of my house, in alphabetical order. Stir crazy In early 2020, during the first lockdown, I was going a bit stir crazy. Clare said you re going very strange, you have to go out and get some exercise . After a bit of discussion, we came up with this plan: I d visit all the local villages, in alphabetical order. Choosing the radius I decided that I would pick a round number of kilometers, as the crow flies, from my house. 20km seemed about right. 25km would have included Ely, which would have been nice, but it would have added a great many places, all of them quite distant. Software I wrote a short Rust program to process OSM data into a list of places to visit, and their distances and bearings. You can download a tarball of the alphabetical villages scanner. (I haven t published the git history because it has my house s GPS coordinates in it, and because I committed the output files from which that location can be derived.) The Rides I set off on my first ride, to Aldreth, on Sunday the 31st of May 2020. The final ride collected Yelling, on Saturday the 19th of August 2023. I did quite a few rides in June and July 2020 - more than one a week. (I d read the lockdown rules, and although some of the government messaging said you should stay near your house, that wasn t in the legislation. Of course I didn t go into any buildings or anything.) I m not much of a morning person, so I often set off after lunch. For the longer rides I would usually pack a picnic. Almost all of the rides I did just by myself. There were a handful where I had friends along: Dry Drayton, which I collected with Clare, at night. I held my bike up so the light shone at the village sign, so we could take a photo of it. Madingley, Melbourn and Meldreth, which was quite an expedition with my friend Ben. We went out as far as Royston and nearby Barley (both outside my radius and not on my list) mostly just so that my project would have visited Hertfordshire. The Hemingfords, where I had my friend Matthew along, and we had a very nice pub lunch. Girton and Wilburton, where I visited friends. Indeed, I stopped off in Wilburton on one or two other occasions. And, of course, Yelling, for which there were four of us, again with a nice lunch (in Eltisley). I had relatively little mechanical trouble. My worst ride for this was Exning: I got three punctures that day. Luckily the last one was close to home. I often would stop to take lots of photos en-route. My mum in particular appreciated all the pretty pictures. Rules I decided on these rules: I would cycle to each destination, in order, and it would count as collected if I rode both there and back. I allowed collecting multiple villages in the same outing, provided I did them in the right order. (And obviously I was allowed to pass through places out of order, without counting them.) I tried to get a picture of the village sign, where there was one. Failing that, I got a picture of something in the village with the village s name on it. I think the only one I didn t manage this for was Westley Bottom; I had to make do with the word Westley on some railway level crossing equipment. In Barway I had to make do with a planning application, stuck to a pole. I tried not to enter and leave a village by the same road, if possible. Edge cases I had to make some decisions: I decided that I would consider the project complete if I visited everywhere whose centre was within my radius. But the centre of a settlement is rather hard to define. I needed a hard criterion for my OpenStreetMap data mining: a place counted if there was any node, way or relation, with the relevant place tag, any part of which was within my ambit. That included some places that probably oughtn t to have counted, but, fine. I also decided that I wouldn t visit suburbs of Cambridge, separately from Cambridge itself. I don t consider them separate settlements, at least, not if they re conurbated with Cambridge. So that excluded Trumpington, for example. But I decided that Girton and Fen Ditton were (just) separable. Although the place where I consider Girton and Cambridge to nearly touch, is administratively well inside Girton, I chose to look at land use (on the ground, and in OSM data), rather than administrative boundaries. But I did visit both Histon and Impington, and all each of the Shelfords and Stapleford, as separate entries in my list. Mostly because otherwise I d have to decide whether to skip (say) Impington, or Histon. Whereas skipping suburbs of Cambridge in favour of Cambridge itself was an easy decision, and it also got rid of a bunch of what would have been quite short, boring, urban expeditions. I sorted all the Greats and Littles under G and L, rather than (say) Shelford, Great , which seemed like it would be cheating because then I would be able to do Shelford, Great and Shelford, Little in one go. Northstowe turned from mostly a building site into something that was arguably a settlement, during my project. It wasn t included in the output of my original data mining. Of course it s conurbated with Oakington - but happily, Northstowe inserts right before Oakington in the alphabetical list, so I decided to add it, visiting both the old and new in the same day. There are a bunch of other minor edge cases. Some villages have an outlying hamlet. Mostly I included these. There are some individual farms, which I generally didn t count. Some stats I visited 150 villages plus the Lords Bridge radio observatory. The project took 3 years and 3 months to complete. There were 96 rides, totalling about 4900km. So my mean distance was around 51km. The median distance per ride was a little higher, at around 52 km, and the median duration (including stoppages) was about 2h40. The total duration, if you add them all up, including stoppages, was about 275h, giving a mean speed including photo stops, lunches and all, of 18kph. The longest ride was 89.8km, collecting Scotland Farm, Shepreth, and Six Mile Bottom, so riding across the Cam valley. The shortest ride was 7.9km, collecting Cambridge (obviously); and I think that s the only one I did on my Brompton. The rest were all on my trusty Thorn Audax. My fastest ride (ranking by distance divided by time spent in motion) was to collect Haddenham, where I covered 46.3km in 1h39, giving an average speed in motion of 28.0kph. The most I collected in one day was 5 places: West Wickham, West Wratting, Westley Bottom, Westley Waterless, and Weston Colville. That was the day of the Wests. (There s only one East: East Hatley.) Map Here is a pretty picture of all of my tracklogs:
Edited 2023-08-25 01:32 BST to correct a slip.


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11 August 2023

Ian Jackson: Private posts

I have started to make private posts, accessible only to my Dreamwidth access list. If you re a friend of mine and would like to be on that list, please contact me with your Dreamwidth username (or your OpenID).

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19 July 2023

Ian Jackson: Installing Debian bookworm without systemd

Instructions
  1. Get the official installation image from the usual locations. I got the netinst CD image via BitTorrent.
  2. Boot from the image and go through the installation in the normal way.
    1. You may want to select an alternative desktop environment (and unselect GNOME). These steps have been tested with MATE.
    2. Stop when you are asked to remove the installation media and reboot.
  3. Press Alt + Right arrow to switch to the text VC. Hit return to activate the console and run the following commands (answering yes as appropriate):
chroot /target bash
apt-get install sysvinit-core elogind ntp dbus-x11
apt-get autoremove
exit
  1. Observe the output from the apt-get install. If your disk arrangements are unusual, that may generate some error messages from update-initramfs.
  2. Go back to the installer VC with Alt + Left arrow. If there were no error messages above, you may tell it to reboot.
  3. If there were error messages (for example, I found that if there was disk encryption, alarming messages were printed), tell the installer to go Back . Then ask it to Install GRUB bootloader (again). After that has completed, you may reboot.
  4. Enjoy your Debian system without systemd.
Discussion This is pleasingly straightforward, albeit with an ugly wart. This recipe was not formally developed and tested; it s just what happened when I tried to actually perform this task. The official installation guide has similar instructions although they don t seem to have the initramfs workaround. update-initramfs The need to go back and have the installer reinstall grub is because if your storage is not very straightforward, the update-initramfs caused by apt-get install apparently doesn t have all the right context. I haven t investigated this at all; indeed, I don t even really know that the initramfs generated in step 3 above was broken, although the messages did suggest to me that important pieces or config might have been omitted. Instead, I simply chose to bet that it might be broken, but that the installer would know what to do. So I used the installer s install GRUB bootloader option, which does regenerate the initramfs. So, I don t know that step 6 is necessary. In principle it would be better to do the switch from systemd to sysvinit earlier in the installation process, and under the control of the installer. But by default the installer goes straight from the early setup questions through to the set the time or reboot questions, without stopping. One could use the expert mode, or modify the command line, or something, but all of those things are, in practice, a lot more typing and/or interaction. And as far as I m aware the installer doesn t have an option for avoiding systemd . The apt-get install line sysvinit-core is the principal part of the sysvinit init system. Asking to install that causes the deinstallation of systemd s init and ancillary packages. systemd refuses to allow itself to be deinstalled, if it is already running, so if you boot into the systemd system you can t then switch init system. This is why the switch is best done at install time. If you re too late, there are instructions for changing init system post-installation. elogind is a forked version of some of systemd s user desktop session functionality. In practice modern desktop environments need this; without it, apt will want to remove things you probably want to keep. Even if you force it, you may find that your desktop environment can t adjust the audio volume, etc. ntp is needed because nowadays the default network time client is systemd-timesyncd (which is a bad idea even on systems with systemd as init). We need to specify it because the package dependencies don t automatically give you any replacement for systemd-timesyncd. dbus-x11 is a glue component. In theory it ought to be installed automatically. However, there have been problems with the dependencies that meant that (for example) asking for emacs would try to switch the init system. Specifying dbus-x11 explicitly is a workaround for that, which I nowadays adopt out of caution. Perhaps it is no longer needed. (On existing systems, it may be necessary to manually install orphan-sysvinit-scripts, which exists as a suboptimal technical workaround for the sociopolitical problems of hostile package maintainers and Debian s governance failures. The recipe above seems to install this package automatically.) usrmerge This recipe results in a system which has merged-/usr via symlinks. This configuration is a bad one. Ideally usrmerge-via-symlinks would be avoided. The un-merged system is declared not officially supported by Debian and key packages try very hard to force it on users. However, merged-/usr-via-symlinks is full of bugs (mostly affecting package management) which are far too hard to fix (a project by some folks to try to do so has given up). I suspect un-merged systems will suffer from fewer bugs in practice. But I don t know how to persuade d-i to make one. Installer images I think there is room in the market for an unofficial installer image which installs without systemd and perhaps without usrmerge. I don t have the effort for making such a thing myself. Conclusion Installing Debian without systemd is fairly straightforward. Operating Debian without systemd is a pleasure and every time one of my friends has some systemd-induced lossage I get to feel smug.

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19 April 2023

Ian Jackson: The Rust Foundation's bad draft trademark policy

tl;dr The Rust Foundation s proposed new trademark policy is far too restrictive, and will cause (more) drama unless it is substantially revised. Process Rust is a trademark owned by the Foundation. The Rust Foundation still seems to be finding its feet. Evidently, one of the items on its backlog was to update the trademark policy. Apparently they have been working on this for some time, in an informal working group. In August, there was a survey. (I saw it in This Week In Rust, the community-curated newsletter where most important stuff appears, and responded.) I don t think the results of this survey have been published anywhere. Last week (12th April) the Foundation published an official Inside Rust blog post linking to a draft. They included a link to a feedback survey, closing on the 17th of April i.e., it was open for 5 days. This is far too short a period for formal feedback on such a draft. Especially given that this process has apparently already been generating significant controversy within parts of the Rust community. Substance Overall, this policy is poor. It is far too restrictive. It is likely to lead to (further) controversy and argument, including conflicts with Rust s downstreams. It does not serve the needs of the Rust community. In particular, the Rust community does not need the trademark to: The community does need the trademark to: It might be useful to use the trademark to strengthen licensing or CoC compliance. For example, good faith redistributions of a modified Rust, as Rust , would be Free Software, even though the copyright licence permits proprietary derivatives; so use of the Rust trademark should probably require use of a Free licence. There should be a series of blanket permissions to use the word Rust in for example: Currently there aren t. For example the current Debian practice of calling Rust libraries rust-<name-of-crate> is probably in violation. There are a number of more detailed problems with the wording. Values The policy has all the hallmarks of excessive influence from traditional trademark lawyers and not enough influence from the Free Software community. I would like to remind the Free Software activists on the inside of this process that the lawyers are there to serve you and the community. The values embodied in trademark law often conflict with the values of the Free Software community. The Rust Project should adopt a trademark policy which follows the community s values - even if that might weaken our ability to sue evildoers. Next steps The Foundation should take a step back and pause the process. Then, the Foundation should restart the process from a much earlier stage, with much wider publicity. Each stage should be widely advertised to the whole community, with opportunities for feedback. This should include publishing the results of the August 2022 survey. The Foundation should publish a sketch of the legal advice they have received, publicly say what the plausible options are and what their consequences might be (for the community, for downstreams, and for the Foundation s enforcement ability). (Some of this will no doubt repeat the work that has been done in the informal trademark working group. That work wasn t widely enough advertised.) Echoes of a dispute from 2006 Mozilla made a very similar mistake with Firefox in 2006. The official policy stated that no-one was allowed to distribute Firefox with any patches, unless those patches had been pre-approved by Mozilla. Debian is committed to Software Freedom. This must includes the freedom to modify the software as one sees fit, even if the original authors don t agree. Now, overly-restrictive trademark policies are hardly new. Debian often takes the practical view that usually the upstream with such a policy doesn t really mean it. But Mozilla decided they did mean it. They contacted Debian asking for Debian to get their patches approved. Since that wasn t acceptable to Debian, they stopped using the word Firefox . For a decade, Debian s Firefox browser was called Iceweasel . We don t want something similar happening to Rust .

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2 March 2023

Ian Jackson: Never use git submodules

tl;dr git submodules are always the wrong solution. Yes, even the to the problem they were specifically invented to solve. ( Read more... )

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3 February 2023

Ian Jackson: derive-adhoc: powerful pattern-based derive macros for Rust

tl;dr Have you ever wished that you could that could write a new derive macro without having to mess with procedural macros? Now you can! derive-adhoc lets you write a #[derive] macro, using a template syntax which looks a lot like macro_rules!. It s still 0.x - so unstable, and maybe with sharp edges. We want feedback! And, the documentation is still very terse. It is doesn t omit anything, but, it is severely lacking in examples, motivation, and so on. It will suit readers who enjoy dense reference material. ( Read more... )

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14 January 2023

Ian Jackson: SGO (and my) VPN and network access tools - in bookworm

Recently, we managed to get secnet and hippotat into Debian. They are on track to go into Debian bookworm. This completes in Debian the set of VPN/networking tools I (and other Greenend) folks have been using for many years. The Sinister Greenend Organisation s suite of network access tools consists mainly of: secnet secnet is our very mature VPN system. Its basic protocol idea is similar to that in Wireguard, but it s much older. Differences from Wireguard include: secnet was originally written by Stephen Early, starting in 1996 or so. I inherited it some years ago and have been maintaining it since. It s mostly written in C. Hippotat Hippotat is best described by copying the intro from the docs:
Hippotat is a system to allow you to use your normal VPN, ssh, and other applications, even in broken network environments that are only ever tested with web stuff . Packets are parcelled up into HTTP POST requests, resembling form submissions (or JavaScript XMLHttpRequest traffic), and the returned packets arrive via the HTTP response bodies.
It doesn t rely on TLS tunnelling so can work even if the local network is trying to intercept TLS. I recently rewrote Hippotat in Rust. userv ipif userv ipif is one of the userv utilities. It allows safe delegation of network routing to unprivileged users. The delegation is of a specific address range, so different ranges can be delegated to different users, and the authorised user cannot interfere with other traffic. This is used in the default configuration of hippotat packages, so that an ordinary user can start up the hippotat client as needed. On chiark userv-ipif is used to delegate networking to users, including administrators of allied VPN realms. So chiark actually runs at least 4 VPN-ish systems in production: secnet, hippotat, Mark Wooding s Tripe, and still a few links managed by the now-superseded udptunnel system. userv userv ipif is a userv service. That is, it is a facility which uses userv to bridge a privilege boundary. userv is perhaps my most under-appreciated program. userv can be used to straightforwardly bridge (local) privilege boundaries on Unix systems. So for example it can: userv services can be defined by the called user, not only by the system administrator. This allows a user to reconfigure or divert a system-provided default implementation, and even allows users to define and implement ad-hoc services of their own. (Although, the system administrator can override user config.) Acknowledgements Thanks for the help I had in this effort. In particular, thanks to Sean Whitton for encouragement, and the ftpmaster review; and to the Debian Rust Team for their help navigating the complexities of handling Rust packages within the Debian Rust Team workflow.

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20 December 2022

Ian Jackson: Rust for the Polyglot Programmer, December 2022 edition

I have reviewed, updated and revised my short book about the Rust programming language, Rust for the Polyglot Programmer. It now covers some language improvements from the past year (noting which versions of Rust they re available in), and has been updated for changes in the Rust library ecosystem. With (further) assistance from Mark Wooding, there is also a new table of recommendations for numerical conversion. Recap about Rust for the Polyglot Programmer There are many introductory materials about Rust. This one is rather different. Compared to much other information about Rust, Rust for the Polyglot Programmer is: After reading Rust for the Polyglot Programmer, you won t know everything you need to know to use Rust for any project, but should know where to find it. Comments are welcome of course, via the Dreamwidth comments or Salsa issue or MR. (If you re making a contribution, please indicate your agreement with the Developer Certificate of Origin.)
edited 2022-12-20 01:48 to fix a typo


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18 December 2022

Ian Jackson: Rust needs #[throws]

tl;dr: Ok-wrapping as needed in today s Rust is a significant distraction, because there are multiple ways to do it. They are all slightly awkward in different ways, so are least-bad in different situations. You must choose a way for every fallible function, and sometimes change a function from one pattern to another. Rust really needs #[throws] as a first-class language feature. Code using #[throws] is simpler and clearer. Please try out withoutboats s fehler. I think you will like it. Contents A recent personal experience in coding style Ever since I read withoutboats s 2020 article about fehler, I have been using it in most of my personal projects. For Reasons I recently had a go at eliminating the dependency on fehler from Hippotat. So, I made a branch, deleted the dependency and imports, and started on the whack-a-mole with the compiler errors. After about a half hour of this, I was starting to feel queasy. After an hour I had decided that basically everything I was doing was making the code worse. And, bizarrely, I kept having to make individual decisons about what idiom to use in each place. I couldn t face it any more. After sleeping on the question I decided that Hippotat would be in Debian with fehler, or not at all. Happily the Debian Rust Team generously helped me out, so the answer is that fehler is now in Debian, so it s fine. For me this experience, of trying to convert Rust-with-#[throws] to Rust-without-#[throws] brought the Ok wrapping problem into sharp focus. What is Ok wrapping? Intro to Rust error handling (You can skip this section if you re already a seasoned Rust programer.) In Rust, fallibility is represented by functions that return Result<SuccessValue, Error>: this is a generic type, representing either whatever SuccessValue is (in the Ok variant of the data-bearing enum) or some Error (in the Err variant). For example, std::fs::read_to_string, which takes a filename and returns the contents of the named file, returns Result<String, std::io::Error>. This is a nice and typesafe formulation of, and generalisation of, the traditional C practice, where a function indicates in its return value whether it succeeded, and errors are indicated with an error code. Result is part of the standard library and there are convenient facilities for checking for errors, extracting successful results, and so on. In particular, Rust has the postfix ? operator, which, when applied to a Result, does one of two things: if the Result was Ok, it yields the inner successful value; if the Result was Err, it returns early from the current function, returning an Err in turn to the caller. This means you can write things like this:
    let input_data = std::fs::read_to_string(input_file)?;
and the error handling is pretty automatic. You get a compiler warning, or a type error, if you forget the ?, so you can t accidentally ignore errors. But, there is a downside. When you are returning a successful outcome from your function, you must convert it into a Result. After all, your fallible function has return type Result<SuccessValue, Error>, which is a different type to SuccessValue. So, for example, inside std::fs::read_to_string, we see this:
        let mut string = String::new();
        file.read_to_string(&mut string)?;
        Ok(string)
     
string has type String; fs::read_to_string must return Result<String, ..>, so at the end of the function we must return Ok(string). This applies to return statements, too: if you want an early successful return from a fallible function, you must write return Ok(whatever). This is particularly annoying for functions that don t actually return a nontrivial value. Normally, when you write a function that doesn t return a value you don t write the return type. The compiler interprets this as syntactic sugar for -> (), ie, that the function returns (), the empty tuple, used in Rust as a dummy value in these kind of situations. A block ( ... ) whose last statement ends in a ; has type (). So, when you fall off the end of a function, the return value is (), without you having to write it. So you simply leave out the stuff in your program about the return value, and your function doesn t have one (i.e. it returns ()). But, a function which either fails with an error, or completes successfuly without returning anything, has return type Result<(), Error>. At the end of such a function, you must explicitly provide the success value. After all, if you just fall off the end of a block, it means the block has value (), which is not of type Result<(), Error>. So the fallible function must end with Ok(()), as we see in the example for std::fs::read_to_string. A minor inconvenience, or a significant distraction? I think the need for Ok-wrapping on all success paths from fallible functions is generally regarded as just a minor inconvenience. Certainly the experienced Rust programmer gets very used to it. However, while trying to remove fehler s #[throws] from Hippotat, I noticed something that is evident in codebases using vanilla Rust (without fehler) but which goes un-remarked. There are multiple ways to write the Ok-wrapping, and the different ways are appropriate in different situations. See the following examples, all taken from a real codebase. (And it s not just me: I do all of these in different places, - when I don t have fehler available - but all these examples are from code written by others.) Idioms for Ok-wrapping - a bestiary Wrap just a returned variable binding If you have the return value in a variable, you can write Ok(reval) at the end of the function, instead of retval.
    pub fn take_until(&mut self, term: u8) -> Result<&'a [u8]>  
        // several lines of code
        Ok(result)
     
If the returned value is not already bound to variable, making a function fallible might mean choosing to bind it to a variable. Wrap a nontrivial return expression Even if it s not just a variable, you can wrap the expression which computes the returned value. This is often done if the returned value is a struct literal:
    fn take_from(r: &mut Reader<'_>) -> Result<Self>  
        // several lines of code
        Ok(AuthChallenge   challenge, methods  )
     
Introduce Ok(()) at the end For functions returning Result<()>, you can write Ok(()). This is usual, but not ubiquitous, since sometimes you can omit it. Wrap the whole body If you don t have the return value in a variable, you can wrap the whole body of the function in Ok( ). Whether this is a good idea depends on how big and complex the body is.
    fn from_str(s: &str) -> std::result::Result<Self, Self::Err>  
        Ok(match s  
            "Authority" => RelayFlags::AUTHORITY,
            // many other branches
            _ => RelayFlags::empty(),
         )
     
Omit the wrap when calling fallible sub-functions If your function wraps another function call of the same return and error type, you don t need to write the Ok at all. Instead, you can simply call the function and not apply ?. You can do this even if your function selects between a number of different sub-functions to call:
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result  
        if flags::unsafe_logging_enabled()  
            std::fmt::Display::fmt(&self.0, f)
          else  
            self.0.display_redacted(f)
         
     
But this doesn t work if the returned error type isn t the same, but needs the autoconversion implied by the ? operator. Convert a fallible sub-function error with Ok( ... ?) If the final thing a function does is chain to another fallible function, but with a different error type, the error must be converted somehow. This can be done with ?.
     fn try_from(v: i32) -> Result<Self, Error>  
         Ok(Percentage::new(v.try_into()?))
      
Convert a fallible sub-function error with .map_err Or, rarely, people solve the same problem by converting explicitly with .map_err:
     pub fn create_unbootstrapped(self) -> Result<TorClient<R>>  
         // several lines of code
         TorClient::create_inner(
             // several parameters
         )
         .map_err(ErrorDetail::into)
      
What is to be done, then? The fehler library is in excellent taste and has the answer. With fehler: fehler provides: This is precisely correct. It is very ergonomic. Consequences include: Limitations of fehler But, fehler is a Rust procedural macro, so it cannot get everything right. Sadly there are some wrinkles. But, Rust-with-#[throws] is so much nicer a language than Rust-with-mandatory-Ok-wrapping, that these are minor inconveniences. Please can we have #[throws] in the Rust language This ought to be part of the language, not a macro library. In the compiler, it would be possible to get the all the corner cases right. It would make the feature available to everyone, and it would quickly become idiomatic Rust throughout the community. It is evident from reading writings from the time, particularly those from withoutboats, that there were significant objections to automatic Ok-wrapping. It seems to have become quite political, and some folks burned out on the topic. Perhaps, now, a couple of years later, we can revisit this area and solve this problem in the language itself ? Explicitness An argument I have seen made against automatic Ok-wrapping, and, in general, against any kind of useful language affordance, is that it makes things less explicit. But this argument is fundamentally wrong for Ok-wrapping. Explicitness is not an unalloyed good. We humans have only limited attention. We need to focus that attention where it is actually needed. So explicitness is good in situtions where what is going on is unusual; or would otherwise be hard to read; or is tricky or error-prone. Generally: explicitness is good for things where we need to direct humans attention. But Ok-wrapping is ubiquitous in fallible Rust code. The compiler mechanisms and type systems almost completely defend against mistakes. All but the most novice programmer knows what s going on, and the very novice programmer doesn t need to. Rust s error handling arrangments are designed specifically so that we can avoid worrying about fallibility unless necessary except for the Ok-wrapping. Explicitness about Ok-wrapping directs our attention away from whatever other things the code is doing: it is a distraction. So, explicitness about Ok-wrapping is a bad thing. Appendix - examples showning code with Ok wrapping is worse than code using #[throws] Observe these diffs, from my abandoned attempt to remove the fehler dependency from Hippotat. I have a type alias AE for the usual error type (AE stands for anyhow::Error). In the non-#[throws] code, I end up with a type alias AR<T> for Result<T, AE>, which I think is more opaque but at least that avoids typing out -> Result< , AE> a thousand times. Some people like to have a local Result alias, but that means that the standard Result has to be referred to as StdResult or std::result::Result.
With fehler and #[throws] Vanilla Rust, Result<>, mandatory Ok-wrapping

Return value clearer, error return less wordy:
impl Parseable for Secret impl Parseable for Secret
#[throws(AE)]
fn parse(s: Option<&str>) -> Self fn parse(s: Option<&str>) -> AR<Self>
let s = s.value()?; let s = s.value()?;
if s.is_empty() throw!(anyhow!( secret value cannot be empty )) if s.is_empty() return Err(anyhow!( secret value cannot be empty ))
Secret(s.into()) Ok(Secret(s.into()))
No need to wrap whole match statement in Ok( ):
#[throws(AE)]
pub fn client<T>(&self, key: & static str, skl: SKL) -> T pub fn client<T>(&self, key: & static str, skl: SKL) -> AR<T>
where T: Parseable + Default where T: Parseable + Default
match self.end Ok(match self.end
LinkEnd::Client => self.ordinary(key, skl)?, LinkEnd::Client => self.ordinary(key, skl)?,
LinkEnd::Server => default(), LinkEnd::Server => default(),
)
Return value and Ok(()) entirely replaced by #[throws]:
impl Display for Loc impl Display for Loc
#[throws(fmt::Error)]
fn fmt(&self, f: &mut fmt::Formatter) fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result
write!(f, :? : , &self.file, self.lno)?; write!(f, :? : , &self.file, self.lno)?;
if let Some(s) = &self.section if let Some(s) = &self.section
write!(f, )?; write!(f, )?;
Ok(())
Call to write! now looks the same as in more complex case shown above:
impl Debug for Secret impl Debug for Secret
#[throws(fmt::Error)]
fn fmt(&self, f: &mut fmt::Formatter) fn fmt(&self, f: &mut fmt::Formatter)-> fmt::Result
write!(f, "Secret(***)")?; write!(f, "Secret(***)")
Much tiresome return Ok() noise removed:
impl FromStr for SectionName impl FromStr for SectionName
type Err = AE; type Err = AE;
#[throws(AE)]
fn from_str(s: &str) -> Self fn from_str(s: &str) ->AR< Self>
match s match s
COMMON => return SN::Common, COMMON => return Ok(SN::Common),
LIMIT => return SN::GlobalLimit, LIMIT => return Ok(SN::GlobalLimit),
_ => _ =>
; ;
if let Ok(n@ ServerName(_)) = s.parse() return SN::Server(n) if let Ok(n@ ServerName(_)) = s.parse() return Ok(SN::Server(n))
if let Ok(n@ ClientName(_)) = s.parse() return SN::Client(n) if let Ok(n@ ClientName(_)) = s.parse() return Ok(SN::Client(n))
if client == LIMIT return SN::ServerLimit(server) if client == LIMIT return Ok(SN::ServerLimit(server))
let client = client.parse().context( client name in link section name )?; let client = client.parse().context( client name in link section name )?;
SN::Link(LinkName server, client ) Ok(SN::Link(LinkName server, client ))
edited 2022-12-18 19:58 UTC to improve, and 2022-12-18 23:28 to fix, formatting


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16 November 2022

Ian Jackson: Stop writing Rust linked list libraries!

tl;dr: Don t write a Rust linked list library: they are hard to do well, and usually useless. Use VecDeque, which is great. If you actually need more than VecDeque can do, use one of the handful of libraries that actually offer a significantly more useful API. If you are writing your own data structure, check if someone has done it already, and consider slotmap or generation_arena, (or maybe Rc/Arc). Contents Survey of Rust linked list libraries I have updated my Survey of Rust linked list libraries. Background In 2019 I was writing plag-mangler, a tool for planar graph layout. I needed a data structure. Naturally I looked for a library to help. I didn t find what I needed, so I wrote rc-dlist-deque. However, on the way I noticed an inordinate number of linked list libraries written in Rust. Most all of these had no real reason for existing. Even the one in the Rust standard library is useless. Results Now I have redone the survey. The results are depressing. In 2019 there were 5 libraries which, in my opinion, were largely useless. In late 2022 there are now thirteen linked list libraries that ought probably not ever to be used. And, a further eight libraries for which there are strictly superior alternatives. Many of these have the signs of projects whose authors are otherwise competent: proper documentation, extensive APIs, and so on. There is one new library which is better for some applications than those available in 2019. (I m referring to generational_token_list, which makes a plausible alternative to dlv-list which I already recommended in 2019.) Why are there so many poor Rust linked list libraries ? Linked lists and Rust do not go well together. But (and I m guessing here) I presume many people are taught in programming school that a linked list is a fundamental data structure; people are often even asked to write one as a teaching exercise. This is a bad idea in Rust. Or maybe they ve heard that writing linked lists in Rust is hard and want to prove they can do it. Double-ended queues One of the main applications for a linked list in a language like C, is a queue, where you put items in at one end, and take them out at the other. The Rust standard library has a data structure for that, VecDeque. Five of the available libraries: For these you could, and should, just use VecDeque instead. The Cursor concept A proper linked list lets you identify and hold onto an element in the middle of the list, and cheaply insert and remove elements there. Rust s ownership and borrowing rules make this awkward. One idea that people have many times reinvented and reimplemented, is to have a Cursor type, derived from the list, which is a reference to an element, and permits insertion and removal there. Eight libraries have implemented this in the obvious way. However, there is a serious API limitation: To prevent a cursor being invalidated (e.g. by deletion of the entry it points to) you can t modify the list while the cursor exists. You can only have one cursor (that can be used for modification) at a time. The practical effect of this is that you cannot retain cursors. You can make and use such a cursor for a particular operation, but you must dispose of it soon. Attempts to do otherwise will see you losing a battle with the borrow checker. If that s good enough, then you could just use a VecDeque and use array indices instead of the cursors. It s true that deleting or adding elements in the middle involves a lot of copying, but your algorithm is O(n) even with the single-cursor list libraries, because it must first walk the cursor to the desired element. Formally, I believe any algorithm using these exclusive cursors can be rewritten, in an obvious way, to simply iterate and/or copy from the start or end (as one can do with VecDeque) without changing the headline O() performance characteristics. IMO the savings available from avoiding extra copies etc. are not worth the additional dependency, unsafe code, and so on, especially as there are other ways of helping with that (e.g. boxing the individual elements). Even if you don t find that convincing, generational_token_list and dlv_list are strictly superior since they offer a more flexible and convenient API and better performance, and rely on much less unsafe code. Rustic approaches to pointers-to-and-between-nodes data structures Most of the time a VecDeque is great. But if you actually want to hold onto (perhaps many) references to the middle of the list, and later modify it through those references, you do need something more. This is a specific case of a general class of problems where the naive approach (use Rust references to the data structure nodes) doesn t work well. But there is a good solution: Keep all the nodes in an array (a Vec<Option<T>> or similar) and use the index in the array as your node reference. This is fast, and quite ergonomic, and neatly solves most of the problems. If you are concerned that bare indices might cause confusion, as newly inserted elements would reuse indices, add a per-index generation count. These approaches have been neatly packaged up in libraries like slab, slotmap, generational-arena and thunderdome. And they have been nicely applied to linked lists by the authors of generational_token_list. and dlv-list. The alternative for nodey data structures in safe Rust: Rc/Arc Of course, you can just use Rust s interior mutability and reference counting smart pointers, to directly implement the data structure of your choice. In many applications, a single-threaded data structure is fine, in which case Rc and Cell/RefCell will let you write safe code, with cheap refcount updates and runtime checks inserted to defend against unexpected aliasing, use-after-free, etc. I took this approach in rc-dlist-deque, because I wanted each node to be able to be on multiple lists. Rust s package ecosystem demonstrating software s NIH problem The Rust ecosystem is full of NIH libraries of all kinds. In my survey, there are: five good options; seven libraries which are plausible, but just not as good as the alternatives; and fourteen others. There is a whole rant I could have about how the whole software and computing community is pathologically neophilic. Often we seem to actively resist reusing ideas, let alone code; and are ignorant and dismissive of what has gone before. As a result, we keep solving the same problems, badly - making the same mistakes over and over again. In some subfields, working software, or nearly working software, is frequently replaced with something worse, maybe more than once. One aspect of this is a massive cultural bias towards rewriting rather than reusing, let alone fixing and using. Many people can come out of a degree, trained to be a programmer, and have no formal training in selecting and evaluating software; this is even though working effectively with computers requires making good use of everyone else s work. If one isn t taught these skills (when and how to search for prior art, how to choose between dependencies, and so on) one must learn it on the job. The result is usually an ad-hoc and unsystematic approach, often dominated by fashion rather than engineering. The package naming paradox The more experienced and competent programmer is aware of all the other options that exist - after all they have evaluated other choices before writing their own library. So they will call their library something like generational_token_list or vecdeque-stableix. Whereas the novice straight out of a pre-Rust programming course just thinks what they are doing is the one and only obvious thing (even though it s a poor idea) and hasn t even searched for a previous implementation. So they call their package something obvious like linked list . As a result, the most obvious names seem to refer to the least useful libraries.
Edited 2022-11-16 23:55 UTC to update numbers of libraries in various categories following updates to the survey (including updates prompted by feedback received after this post first published).


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