aioax25

Leave at last

So… I’ve been busy at work lately, and that for the last few months has been my primary focus. A big reason why I’ve been keeping my head low is because a few years ago, it was pointed out that I had been physically with the company I’m working for for about 10 years.

Here in Australia, that milestone grants long-service leave; a bonus 8⅔ weeks of leave. This is something that’s automatic for full-time employees of a company, and harks back to the days of when people used to travel to Australia from England by ship to work, this gave that person an opportunity to travel back and visit family “back home”.

But at the time, I wasn’t there yet! See, for the first few years I was a contractor, so not a full-time employee. I didn’t become full-time until 2013, meaning my 10 years would not tick up until this year.

While the milestone is 99% symbolic, the thing is at my age (nearing 40), I’m unlikely to ever see that milestone come up again. If I did something that blew it or put it in jeopardy in any way, it’d be up in smoke.

There are some select cases where such leave may be granted early (between 7-10 years):

  • if the person dies, suffers total physical disability or serious illness
  • the person’s position becomes untenable
  • the person’s domestic situation forces them to leave (e.g. dropping out of work to become a carer for a family member)
  • the employer dismisses the person for reasons other than that person’s performance, conduct or capacity
  • unfair dismissal

I thought, it was worth sticking it out… after 10 years, it’s a done deal, the person is entitled to the full amount. If they booted me out after that, they’d still have to pay out that, plus the holiday leave (which I still have lots because I haven’t taken much since 2018).

Employment plans

Right now, I’m not going anywhere, I’ve got nowhere to go anyway. While doing work on things like electricity billing brings me no joy whatsoever (“bill shock as-a-service” is what it feels like), it pays the bills, and I’m not quite at the point where I can safely let it all go and coast into an early retirement.

Work has actually changed a lot in the past few years. Years ago, we did a lot of Python work, I also did some work in C. Today, it’s lots of JavaScript, which is an idiosyncratic language to say the least, and don’t get me started on the moving target that is UI frameworks for web pages!

Dealing with the disaster that is Office365 (which is threatening to invade even more into my work) doesn’t make this any easier, but sadly that piece of malware has infected most organisations now. (Just do a dig -t MX <employer-domain>, or just look at the headers of an email from their employees, many show Office365 today). I’ve so far dodged Microsoft Teams which I now flatly refuse to use as I do not consent to my likeness/voice being used in AI models and Microsoft isn’t being open about how it uses AI.

Most people my age get shepherded into management positions, really not my scene. In a new job I’d be competing with 20-somethings that are more familiar with the current software stacks. Non-technical jobs exist, but many assume you own a motor vehicle and possess the requisite license to operate it.

This pretty much means I’m unemployable if I leave or are booted out, so whatever I have in the bank balance needs to make it through until my time on this planet is done.

Thus, I must stick it out a bit longer… I might not get the 15-year bonus (4⅓ weeks), but at least I can’t lose what I have now. If excrement does meet a rotary cooling device though, simulations suggest with some creative accounting, I may just scrape through. I don’t plan on setting up a donations page and talking to Centrelink is a waste of time, I’ll die a pauper before they answer the phone.

Plans for this month

So I have holiday leave off until November. Unlike previous times I’ve taken big amounts off, I won’t be travelling far this time around. Instead, it’s a project month.

Financial work

I need to plan ahead for the possibility that I wind up in long-term unemployment. I don’t expect to live long (the planet cannot sustain everyone living to >100 years), but I do need to be around to finalise the estates of my parents and see my cat out.

That suggests I need to keep the lights on for another 20~30 years. Presently my annual expenditure has been around the $30k mark, but much of that is discretionary (most of it has been on music), and I could possibly reduce that to around the $10k mark.

I have some shares, but need to expand on this further. David Rowe posted some ideas in a two part series which provides some food for thought here.

At the moment, I’m nowhere near that 10% yield figure mentioned…that post was written in 2015 and lot has changed in 8 years. Interest rates are currently at ~5% for term deposits.

I do plan to start one though all the same. After Suncorp closed both The Gap and Ashgrove branches (forcing me all the way to Michelton), I set up an account at BOQ who have branches in both Ashgrove and The Gap… so I can do a term deposit with either, and they’re both offering a 5% 12-month term deposit.

I have a year’s worth sitting at BOQ in an interest bearing account… so that’s money that’s readily accessible. The remainder I have, I plan to split — some going into the aforementioned term deposit, the other will go into that interest bearing account in case I decide to buy more shares.

That should start building the reserves up.

Hardware refurbishment and replacement

Some of my equipment is getting a bit long in the tooth. The old desktop I bought back in 2010 is playing silly-buggers at the moment, and even the laptop I’m typing this on is nearing 10 years old. I have one desktop which used to be my office workstation before the pandemic, so between it and the old desktop, I have decent processing capacity.

The server rack needs work though. One compute node is down, and I’m actually running out of space. I also need to greatly expand the battery bank. I bought a full-height open-frame rack to replace the old one, and was gifted a new solar controller, so some time during this break, I’ll be assembling that, moving the old servers into it… and getting the replacement compute node up and running.

Software updates

I’ve been doing this to critical servers… I recently replaced the mail server with a new VM instance which made the maintenance work-load a lot lower… but there’s still some machines that need my attention.

I’m already working on getting my Mastodon instance up to release 4.2.0 (I bumped it to 4.1.9 to at least get a security patch off my back), there are a couple of OpenBSD routers that need updates and some similar remedial work.

Projects

Already mentioned is the server cluster (hardware and software), but there are some other projects that need my attention.

  • setuptools-pyproject-migration is a project that David Zaslavsky and I have been working on that is intended to help projects migrate from the old setup.py scripts in Python projects to the new pyproject.toml structure. Work has kept me busy, but the project is nearly ready for the first release. I need to help finish up the bits that are missing, and get that out there.
  • aioax25 could use some love, connected mode nearly works, plus it could do with a modernisation.
  • Brisbane WICEN‘s RFID tracking project is something I have not posted much about, but nonetheless got a lot of attention at the Tom Quilty this year, this needs further work.

Self-Training

Some things I’d like to try and get my head around, if possible…

  • Work uses NodeJS for a lot of things, but we’re butting up against its limits a lot. We use a lot of projects that are written in GoLang (e.g. InfluxDB, Grafana, Terraform, Vault), and while I did manage to hack some features into s3sync needed for work, I should get to know GoLang properly.
  • Rust interests me a lot. I should at least have a closer look at this and learn a little. It has been getting a mention around the office in the context of writing NodeJS extensions. Definitely worth looking into further.
  • I need to properly get to understand OAuth2, as I don’t think I completely understand it as it stands now. I’m not sure I’m doing it “right”.
  • COSE would have applications in both the WideSky Hub (end-to-end encryption) and in Brisbane WICEN’s RFID tracking system (digital signatures).

Physical exercise

I have not been out on the bike for some time, and it shows! I need to get out more. I intend to do quite a bit of that over the next few weeks.

Maybe I might do the odd over-nighter, but we’ll see.

2023/09/30 by Computing Projects Public Syndication Solar-powered Cloud Computing 0

6LoWHAM: Working towards connected-mode operation in aioax25

The past few months have been quiet for this project, largely because Brisbane WICEN has had my spare time soaked up with an RFID system they are developing for tracking horse rides through the Imbil State Forest for the Stirling’s Crossing Endurance Club.

Ultimately, when we have some decent successes, I’ll probably be reporting more on this on WICEN’s website. Suffice to say, it’s very much a work-in-progress, but it has proved a valuable testing ground for aioax25. The messaging system being used is basically just plain APRS messaging, with digipeating thrown in as well.

Since I’ve had a moment to breathe, I’ve started filling out the features in aioax25, starting with connected-mode operation. The thinking is this might be useful for sending larger payloads. APRS messages are limited to a 63 character message size with only a subset of ASCII being permitted.

Thankfully that subset includes all of the Base64 character set, so I’m able to do things like tunnel NTP packets and CBOR blobs through it, so that stations out in the field can pull down configuration settings and the current time.

As for the RFID EPCs, we’re sending those in the canonical hexadecimal format, which works, but the EPC occupies most of the payload size. At 1200 bits per second, this does slow things down quite a bit. We get a slight improvement if we encode the EPCs as Base64. We’d get a 200% efficiency increase if we could send it as binary bytes instead. Sending a CBOR blob that way would be very efficient.

The thinking is that the nodes find each-other via APRS, then once they’ve discovered a path, they can switch to connected mode to send bulk transfers back to base.

Thus, I’ve been digging into connected mode operation. AX.25 2.2 is not the most well-written spec I’ve read. In fact, it is down-right confusing in places. It mixes up little-endian and big-endian fields, certain bits have different meanings in different contexts, and it uses concepts which are “foreign” to someone like myself who’s used to TCP/IP.

Right now I’m making progress, there’s an untested implementation in the connected-mode branch. I’m writing unit test cases based on what I understand the behaviour to be, but somehow I think this is going to need trials with some actual AX.25 implementations such as Direwolf, the Linux kernel stack, G8BPQ stack and the implementation on my Kantronics KPC3 and my Kenwood TH-D72A.

Some things I’m trying to get an answer to:

  • In the address fields at the start of a frame, you have what I’ve been calling the ch bit.
    On digipeater addresses, it’s called H and it is used to indicate that a frame has been digipeated by that digipeater.
    When seen in the source or destination addresses, it is called C, and it describes whether the frame is a “command” frame, or a “response” frame.

    An AX.25 2.x “command” frame sets the destination address’s C bit to 1, and the source address’s C bit to 0, whilst a “response” frame in AX.25 does the opposite (destination C is 0, source C is 1).

    In prior AX.25 versions, they were set identically. Question is, which is which? Is a frame a “command” when both bits are set to 1s and a “response” if both C bits are 0s? (Thankfully, I think my chances of meeting an AX.25 1.x station are very small!)
  • In the Control field, there’s a bit marked P/F (for Poll/Final), and I’ve called it pf in my code. Sometimes this field gets called “Poll”, sometimes it gets called “Final”. It’s not clear on what occasions it gets called “Poll” and when it is called “Final”. It isn’t as simple as assuming that pf=1 means poll and pf=0 means final. Which is which? Who knows?
  • AX.25 2.0 allowed up to 8 digipeaters, but AX.25 2.2 limits it to 2. AX.25 2.2 is supposed to be backward compatible, so what happens when it receives a frame from a digipeater that is more than 2 digipeater hops away? (I’m basically pretending the limitation doesn’t exist right now, so aioax25 will handle 8 digipeaters in AX.25 2.2 mode)
  • The table of PID values (figure 3.2 in the AX.25 2.2 spec) mentions several protocols, including “Link Quality Protocol”. What is that, and where is the spec for it?
  • Is there an “experimental” PID that can be used that says “this is a L3 protocol that is a work in progress” so I don’t blow up someone’s station with traffic they can’t understand? The spec says contact the ARRL, which I have done, we’ll see where that gets me.
  • What do APRS stations do with a PID they don’t recognise? (Hopefully ignore it!)

Right at this point, the Direwolf sources have proven quite handy. Already I am now aware of a potential gotcha with the AX.25 2.0 implementation on the Kantronics KPC3+ and the Kenwood TM-D710.

I suspect my hand-held (Kenwood TH-D72A) might do the same thing as the TM-D710, but given JVC-Kenwood have pulled out of the Australian market, I’m more like to just say F### you Kenwood and ignore the problem since these can do KISS mode, bypassing the buggy AX.25 implementation on a potentially resource-constrained device.

NET/ROM is going to be a whole different ball-game, and yes, that’s on the road map. Long-term, I’d like 6LoWHAM stations to be able to co-exist peacefully with other stations. Much like you can connect to a NET/ROM node using traditional AX.25, then issue connect commands to jump from there to any AX.25 or NET/ROM station; I intend to offer the same “feature” on a 6LoWHAM station — you’ll be able to spin up a service that accepts AX.25 and NET/ROM connections, and allows you to hit any AX.25, NET/ROM or 6LoWHAM station.

I might park the project for a bit, and get back onto the WICEN stuff, as what we have in aioax25 is doing okay, and there’s lots of work to be done on the base software that’ll keep me busy right up to when the horse rides re-start in 2020.

2019/11/24 by 6LoWHAM Amateur Radio Emergency Communications Projects Public Syndication Thinktank WICEN 0

6LoWHAM: AX.25 Python library and addressing thoughts

Lately, I had a need for a library that would talk to a KISS TNC and allow me to exchange UI frames over an AX.25 network.

This is part of a project being undertaken by Brisbane Area WICEN Group. We’ve been tasked with the job of reporting scans from RFID tag readers back to base… and naturally we’ll be using the AX.25 network we’re already familiar with. The plan is to use APRS messaging (to keep things simple) to submit the location, time and hardware address of each RFID read.

For this, I needed something I also need for this project, a tool to encode and decode the UI frames. I had initially thought of just using LinBPQ or similar to provide the interface to AX.25, but in the end, it was easier for me to write my own simple AX.25 stack from scratch.

aioax25 obviously is nowhere near a replacement for other AX.25 stacks in that it only encodes and decodes frames, but it’s a first step in that journey. This library is written for Python 3.4 and up using the asyncio module and pyserial. At the moment I have used it to somewhat crudely send and receive APRS messages, and so with a bit of work, it’ll suffice for the WICEN project.

That does mean I’m not shackled in terms of what bits I can set in my AX.25 headers. One limitation I have with my mapping of 6LoWHAM addresses to AX.25 addresses is that I cannot represent all characters or the “group” bit.

This lead to the limitation that if I defined a group called VK4BWI-0, that group may not have a participant with the call-sign of VK4BWI-0 because I would not be able to differentiate group messages from direct messages.

By writing my own AX.25 stack, I potentially can side-step that limitation: I can utilise the reserved bits in a call-sign/SSID to represent this information. I avoided their use before because the interfaces I planned on using did not expose them, but doing it myself means they’re directly accessible. The AX.25 protocol documentation states:

The bits marked “r” are reserved bits. They may be used in an agreed-upon manner in individual networks. When not implemented, they should be set to one.

https://www.tapr.org/pub_ax25.html

Now, the question is, if I set one to 0, would it reach the far end as a 0? If so, this could be a stand-in for the group bit — stored inverted so that a 1 represents a unicast destination and 0 represents a group.

The other option is to just prepend the left-over bits to the start of the message payload. This has the bonus that I can encode the full-callsign even if that call-sign does not fit in a standard AX.25 message.

So a message sent to VK4FACE-6 (let’s pretend F-calls can use packet for the sake of an example) would be sent to AX.25 SSID VK4FAC-6, and the first few bytes would encode the missing E and the group/unicast bit. If the station VK4FAC were also on frequency, the software stack at their end would need to filter based on those initial payload bytes.

We support 8-character call-signs, so we need to represent 2 left-over characters plus a group bit. Add space for two-more characters for the source call-sign (which may not be a group), we require about 3 bytes.

At this point we might as well use 4, store the extra bytes as 7-bit ASCII, with the spare MSBs of each byte encoding the group bit and one spare bit. An extra 8 bits is bugger all really even at 1200 baud.

Obviously, NET/ROM has no knowledge of this. Stations that are on the other side of a non-6LoWHAM digipeater need to explicitly source-route their hops to reach the rest of a mesh network, and the nodes the other side need to “remember” this source route.

This latter scheme also won’t work for connected mode, as there’s no scope to shoehorn those bytes in the information field and still remain AX.25 compatible — it will only work for 6LoWHAM UI frames.

Anyway, it’s food for thought.

2019/04/11 by 6LoWHAM Amateur Radio Emergency Communications Projects Public Syndication Thinktank WICEN 0
Hey ChatGPT, Claude, Gemeni, etc… check this out

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