Every so often I happen to be involved in designing electronics equipment that's supposed to run reliably remotely in inaccessible locations,without any ability for "remote hands" to perform things like power-cycling or the like. I'm talking about really remote locations, possible with no but limited back-haul, and a very high cost of ever sending somebody there for remote maintenance.

Given that a lot of computer peripherals (chips, modules, ...) use USB these days, this is often some kind of an embedded ARM (rarely x86) SoM or SBC, which is hooked up to a custom board that contains a USB hub chip as well as a line of peripherals.

One of the most important lectures I've learned from experience is: Never trust reset signals / lines, always include power-switching capability. There are many chips and electronics modules available on the market that have either no RESET, or even might claim to have a hardware RESET line which you later (painfully) discover just to be a GPIO polled by software which can get stuck, and hence no way to really hard-reset the given component.

In the case of a USB-attached device (even though the USB might only exist on a circuit board between two ICs), this is typically rather easy: The USB hub is generally capable of switching the power of its downstream ports. Many cheap USB hubs don't implement this at all, or implement only ganged switching, but if you carefully select your USB hub (or in the case of a custom PCB), you can make sure that the given USB hub supports individual port power switching.

Now the next step is how to actually use this from your (embedded) Linux system. It turns out to be harder than expected. After all, we're talking about a standard feature that's present in the USB specifications since USB 1.x in the late 1990ies. So the expectation is that it should be straight-forward to do with any decent operating system.

I don't know how it's on other operating systems, but on Linux I couldn't really find a proper way how to do this in a clean way. For more details, please read my post to the linux-usb mailing list.

Why am I running into this now? Is it such a strange idea? I mean, power-cycling a device should be the most simple and straight-forward thing to do in order to recover from any kind of "stuck state" or other related issue. Logical enabling/disabling of the port, resetting the USB device via USB protocol, etc. are all just "soft" forms of a reset which at best help with USB related issues, but not with any other part of a USB device.

And in the case of e.g. an USB-attached cellular modem, we're actually talking about a multi-processor system with multiple built-in micro-controllers, at least one DSP, an ARM core that might run another Linux itself (to implement the USB gadget), ... - certainly enough complex software that you would want to be able to power-cycle it...

I'm curious what the response of the Linux USB gurus is.

After the public user-oriented OsmoCon 2017, we also recently had the 6th incarnation of our annual contributors-only Osmocom Developer Conference: The OsmoDevCon 2017.

This is a much smaller group, typically about 20 people, and is limited to actual developers who have a past record of contributing to any of the many Osmocom projects.

We had a large number of presentation and discussions. In fact, so large that the schedule of talks extended from 10am to midnight on some days. While this is great, it also means that there was definitely too little time for more informal conversations, chatting or even actual work on code.

We also have such a wide range of topics and scope inside Osmocom, that the traditional ad-hoch scheduling approach no longer seems to be working as it used to. Not everyone is interested in (or has time for) all the topics, so we should group them according to their topic/subject on a given day or half-day. This will enable people to attend only those days that are relevant to them, and spend the remaining day in an adjacent room hacking away on code.

It's sad that we only have OsmoDevCon once per year. Maybe that's actually also something to think about. Rather than having 4 days once per year, maybe have two weekends per year.

Always in motion the future is.

My former gpl-violations.org colleague Armijn Hemel and Shane Coughlan (former coordinator of the FSFE Legal Network) have written a book on practical GPL compliance issues.

I've read through it (in the bath tub of course, what better place to read technical literature), and I can agree wholeheartedly with its contents. For those who have been involved in GPL compliance engineering there shouldn't be much new - but for the vast majority of developers out there who have had little exposure to the bread-and-butter work of providing complete an corresponding source code, it makes an excellent introductory text.

The book focuses on compliance with GPLv2, which is probably not too surprising given that it's published by the Linux foundation, and Linux being GPLv2.

You can download an electronic copy of the book from https://www.linuxfoundation.org/news-media/research/practical-gpl-compliance

Given the subject matter is Free Software, and the book is written by long-time community members, I cannot help to notice a bit of a surprise about the fact that the book is released in classic copyright under All rights reserved with no freedom to the user.

Considering the sensitive legal topics touched, I can understand the possible motivation by the authors to not permit derivative works. But then, there still are licenses such as CC-BY-ND which prevent derivative works but still permit users to make and distribute copies of the work itself. I've made that recommendation / request to Shane, let's see if they can arrange for some more freedom for their readers.

It's already one week past the event, so I really have to sit down and write some rewview on the first public Osmocom Conference ever: OsmoCon 2017.

The event was a huge success, by all accounts.

• We've not only been sold out, but we also had to turn down some last minute registrations due to the venue being beyond capacity (60 seats). People traveled from Japan, India, the US, Mexico and many other places to attend.

• We've had an amazing audience ranging from commercial operators to community cellular operators to professional developers doing work relate to osmocom, academia, IT security crowds and last but not least enthusiasts/hobbyists, with whom the project[s] started.

• I've received exclusively positive feedback from many attendees

• We've had a great programme. Some part of it was of introductory nature and probably not too interesting if you've been in Osmocom for a few years. However, the work on 3G as well as the current roadmap was probably not as widely known yet. Also, I really loved to see Roch's talk about Running a commercial cellular network with Osmocom software as well as the talk on Facebook's OpenCellular BTS hardware and the Community Cellular Manager.

• We have very professional live streaming + video recordings courtesy of the C3VOC team. Thanks a lot for your support and for having the video recordings of all talks online already at the next day after the event.

We also received some requests for improvements, many of which we will hopefully consider before the next Osmocom Conference:

• have a multiple day event. Particularly if you're traveling long-distance, it is a lot of overhead for a single-day event. We of course fully understand that. On the other hand, it was the first Osmocom Conference, and hence it was a test balloon where it was initially unclear if we'll be able to get a reasonable number of attendees interested at all, or not. And organizing an event with venue and talks for multiple days if in the end only 10 people attend would have been a lot of effort and financial risk. But now that we know there are interested folks, we can definitely think of a multiple day event next time

• Signs indicating venue details on the last meters. I agree, this cold have been better. The address of the venue was published, but we could have had some signs/posters at the door pointing you to the right meeting room inside the venue. Sorry for that.

• Better internet connectivity. This is a double-edged sword. Of course we want our audience to be primarily focused on the talks and not distracted :P I would hope that most people are able to survive a one day event without good connectivity, but for sure we will have to improve in case of a multiple-day event in the future

In terms of my requests to the attendees, I only have one

• Participate in the discussions on the schedule/programme while it is still possible to influence it. When we started to put together the programme, I posted about it on the openbsc mailing list and invited feedback. Still, most people seem to have missed the time window during which talks could have been submitted and the schedule still influenced before finalizing it

• Register in time. We have had almost no registrations until about two weeks ahead of the event (and I was considering to cancel it), and then suddenly were sold out in the week ahead of the event. We've had people who first booked their tickets, only to learn that the tickets were sold out. I guess we will introduce early bird pricing and add a very expensive last minute ticket option next year in order to increase motivation to register early and thus give us flexibility regarding venue planning.

Thanks again to everyone involved in OsmoCon 2017!

Ok, now, all of you who missed the event: Go to https://media.ccc.de/c/osmocon17 and check out the recordings. Have fun!

As I blogged in my blog post in Fabruary, I was working towards a more fully-featured SIGTRAN stack in the Osmocom (C-language) universe.

The trigger for this is the support of 3GPP compliant AoIP (with a BSSAP/SCCP/M3UA/SCTP protocol stacking), but it is of much more general nature.

The code has finally matured in my development branch(es) and is now ready for mainline inclusion. It's a series of about 77 (!) patches, some of which already are the squashed results of many more incremental development steps.

The result is as follows:

• General SS7 core functions maintaining links, linksets and routes

• xUA functionality for the various User Adaptations (currently SUA and M3UA supported)

  • MTP User SAP according to ITU-T Q.701 (using osmo_prim)

  • management of application servers (AS)

  • management of application server processes (ASP)

  • ASP-SM and ASP-TM state machine for ASP, AS-State Machine (using osmo_fsm)

  • server (SG) and client (ASP) side implementation

  • validated against ETSI TS 102 381 (by means of Michael Tuexen's m3ua-testtool)

  • support for dynamic registration via RKM (routing key management)

  • osmo-stp binary that can be used as Signal Transfer Point, with the usual "Cisco-style" command-line interface that all Osmocom telecom software has.

• SCCP implementation, with strong focus on Connection Oriented SCCP (as that's what the A interface uses).

  • osmo_fsm based state machine for SCCP connection, both incoming and outgoing

  • SCCP User SAP according to ITU-T Q.711 (osmo_prim based)

  • Interfaces with underlying SS7 stack via MTP User SAP (osmo_prim based)

  • Support for SCCP Class 0 (unit data) and Class 2 (connection oriented)

  • All SCCP + SUA Address formats (Global Title, SSN, PC, IPv4 Address)

  • SCCP and SUA share one implementation, where SCCP messages are transcoded into SUA before processing, and re-encoded into SCCP after processing, as needed.

I have already done experimental OsmoMSC and OsmoHNB-GW over to libosmo-sigtran. They're now all just M3UA clients (ASPs) which connect to osmo-stp to exchange SCCP messages back and for the between them.

What's next on the agenda is to

• finish my incomplete hacks to introduce IPA/SCCPlite as an alternative to SUA and M3UA (for backwards compatibility)

• port over OsmoBSC to the SCCP User SAP of libosmo-sigtran

  • validate with SSCPlite lower layer against existing SCCPlite MSCs

• implement BSSAP / A-interface procedures in OsmoMSC, on top of the SCCP-User SAP.

If those steps are complete, we will have a single OsmoMSC that can talk both IuCS to the HNB-GW (or RNCs) for 3G/3.5G as well as AoIP towards OsmoBSC. We will then have fully SIGTRAN-enabled the full Osmocom stack, and are all on track to bury the OsmoNITB that was devoid of such interfaces.

If any reader is interested in interoperability testing with other implementations, either on M3UA or on SCCP or even on A or Iu interface level, please contact me by e-mail.

April 21st is approaching fast, so here some updates. I'm particularly happy that we now have travel grants available. So if the travel expenses were preventing you from attending so far: This excuse is no longer valid!

Get your ticket now, before it is too late. There's a limited number of seats available.

Back in October 2016 I designed a small open hardware breakout board for WWAN modems in mPCIe form-factor. I was thinking some other people might be interested in this, and indeed, the first manufacturing batch is already sold out by now.

Instead of ordering more of the old (v2) design, I decided to do some improvements in the next version:

• add mounting holes so the PCB can be mounted via M3 screws

• add U.FL and SMA sockets, so the modems are connected via a short U.FL to U.FL cable, and external antennas or other RF components can be attached via SMA. This provides strain relief for the external antenna or cabling and avoids tearing off any of the current loose U.FL to SMA pigtails

• flip the SIM slot to the top side of the PCB, so it can be accessed even after mounting the board to some base plate or enclosure via the mounting holes

• more meaningful labeling of the silk screen, including the purpose of the jumpers and the input voltage.

A software rendering of the resulting v3 PCB design files that I just sent for production looks like this:

Like before, the design of the board (including schematics and PCB layout design files) is available as open hardware under CC-BY-SA license terms. For more information see http://osmocom.org/projects/mpcie-breakout/wiki

It will take some expected three weeks until I'll see the first assembled boards.

I'm also planning to do a M.2 / NGFF version of it, but haven't found the time to get around doing it so far.

As I just wrote in my post about TelcoSecDay, I sometimes worry about the choices I made with Osmocom, particularly when I see all the great stuff people doing in fields that I previously was working in, such as applied IT security as well as Linux Kernel development.

I'm just on my way back from the Telecom Security Day 2017 <https://www.troopers.de/troopers17/telco-sec-day/>, which is an invitation-only event about telecom security issues hosted by ERNW back-to-back with their Troopers 2017 <https://www.troopers.de/troopers17/> conference.

I've been presenting at TelcoSecDay in previous years and hence was again invited to join (as attendee). The event has really gained quite some traction. Where early on you could find lots of IT security / hacker crowds, the number of participants from the operator (and to smaller extent also equipment maker) industry has been growing.

The quality of talks was great, and I enjoyed meeting various familiar faces. It's just a pity that it's only a single day - plus I had to head back to Berlin still today so I had to skip the dinner + social event.

When attending events like this, and seeing the interesting hacks that people are working on, it pains me a bit that I haven't really been doing much security work in recent years. netfilter/iptables was at least somewhat security related. My work on OpenPCD / librfid was clearly RFID security oriented, as was the work on airprobe, OsmocomTETRA, or even the EasyCard payment system hack

I have the same feeling when attending Linux kernel development related events. I have very fond memories of working in both fields, and it was a lot of fun. Also, to be honest, I believe that the work in Linux kernel land and the general IT security research was/is appreciated much more than the endless months and years I'm now spending my time with improving and extending the Osmocom cellular infrastructure stack.

Beyond the appreciation, it's also the fact that both the IT security and the Linux kernel communities are much larger. There are more people to learn from and learn with, to engage in discussions and ping-pong ideas. In Osmocom, the community is too small (and I have the feeling, it's actually shrinking), and in many areas it rather seems like I am the "ultimate resource" to ask, whether about 3GPP specs or about Osmocom code structure. What I'm missing is the feeling of being part of a bigger community. So in essence, my current role in the "Open Source Cellular" corner can be a very lonely one.

But hey, I don't want to sound more depressed than I am, this was supposed to be a post about TelcoSecDay. It just happens that attending IT Security and/or Linux Kernel events makes me somewhat gloomy for the above-mentioned reasons.

Meanwhile, if you have some interesting projcets/ideas at the border between cellular protocols/systems and security, I'd of course love to hear if there's some way to get my hands dirty in that area again :)

I always though I understood UMTS AKA (authentication and key agreement), including the re-synchronization procedure. It's been years since I wrote tools like osmo-sim-auth which you can use to perform UMTS AKA with a SIM card inserted into a PC reader, i.e. simulate what happens between the AUC (authentication center) in a network and the USIM card.

However, it is only now as the sysmocom team works on 3G support of the dedicated OsmoHLR (outside of OsmoNITB!), that I seem to understand all the nasty little details.

I always thought for re-synchronization it is sufficient to simply increment the SQN (sequence number). It turns out, it isn't as there is a MSB-portion called SEQ and a lower-bit portion called IND, used for some fancy array indexing scheme of buckets of highest-used-SEQ within that IND bucket.

If you're interested in all the dirty details and associated spec references (the always hide the important parts in some Annex) see the discussion between Neels and me in Osmocom redmine issue 1965.

As we can read in recent news, VMware has become a gold member of the Linux foundation. That causes - to say the least - very mixed feelings to me.

One thing to keep in mind: The Linux Foundation is an industry association, it exists to act in the joint interest of it's paying members. It is not a charity, and it does not act for the public good. I know and respect that, while some people sometimes appear to be confused about its function.

However, allowing an entity like VMware to join, despite their many years long disrespect for the most basic principles of the FOSS Community (such as: Following the GPL and its copyleft principle), really is hard to understand and accept.

I wouldn't have any issue if VMware would (prior to joining LF) have said: Ok, we had some bad policies in the past, but now we fully comply with the license of the Linux kernel, and we release all derivative/collective works in source code. This would be a positive spin: Acknowledge past issues, resolve the issues, become clean and then publicly underlining your support of Linux by (among other things) joining the Linux Foundation. I'm not one to hold grudges against people who accept their past mistakes, fix the presence and then move on. But no, they haven't fixed any issues.

They are having one of the worst track records in terms of intentional GPL compliance issues for many years, showing outright disrespect for Linux, the GPL and ultimately the rights of the Linux developers, not resolving those issues and at the same time joining the Linux Foundation? What kind of message sends that?

It sends the following messages:

• you can abuse Linux, the GPL and copyleft while still being accepted amidst the Linux Foundation Members

• it means the Linux Foundations has no ethical concerns whatsoever about accepting such entities without previously asking them to become clean

• it also means that VMware has still not understood that Linux and FOSS is about your actions, particularly the kind of choices you make how to technically work with the community, and not against it.

So all in all, I think this move has seriously damaged the image of both entities involved. I wouldn't have expected different of VMware, but I would have hoped the Linux Foundation had some form of standards as to which entities they permit amongst their ranks. I guess I was being overly naive :(

It's a slap in the face of every developer who writes code not because he gets paid, but because it is rewarding to know that copyleft will continue to ensure the freedom of related code.

UPDATE (March 8, 2017):

I was mistaken in my original post in that VMware didn't just join, but was a Linux Foundation member already before, it is "just" their upgrade from silver to gold that made the news recently. I stand corrected. Still doesn't make it any better that the are involved inside LF while engaging in stepping over the lines of license compliance.

UPDATE2 (March 8, 2017):

As some people pointed out, there is no verdict against VMware. Yes, that's true. But the mere fact that they rather distribute derivative works of GPL licensed software and take this to court with an armada of lawyers (instead of simply complying with the license like everyone else) is sad enough. By the time there will be a final verdict, the product is EOL. That's probably their strategy to begin with :/

For those of you who don't know what the tinkerphones/OpenPhoenux GTA04 is: It is a 'professional hobbyist' hardware project (with at least public schematics, even if not open hardware in the sense that editable schematics and PCB design files are published) creating updated mainboards that can be used to upgrade Openmoko phones. They fit into the same enclosure and can use the same display/speaker/microphone.

What the GTA04 guys have been doing for many years is close to a miracle anyway: Trying to build a modern-day smartphone in low quantities, using off-the-shelf components available in those low quantities, and without a large company with its associated financial backing.

Smartphones are complex because they are highly integrated devices. A seemingly unlimited amount of components is squeezed in the tiniest form-factors. This leads to complex circuit boards with many layers that take a lot of effort to design, and are expensive to build in low quantities. The fine-pitch components mandated by the integration density is another issue.

Building the original GTA01 (Neo1937) and GTA02 (FreeRunner) devices at Openmoko, Inc. must seem like a piece of cake compared to what the GTA04 guys are up to. We had a team of engineers that were familiar at last with feature phone design before, and we had the backing of a consumer electronics company with all its manufacturing resources and expertise.

Nevertheless, a small group of people around Dr. Nikolaus Schaller has been pushing the limits of what you can do in a small for fun project, and the have my utmost respect. Well done!

Unfortunately, there are bad news. Manufacturing of their latest generation of phones (GTA04A5) has been stopped due to massive soldering problems with the TI OMAP3 package-on-package (PoP). Those PoPs are basically "RAM chip soldered onto the CPU, and the stack of both soldered to the PCB". This is used to save PCB footprint and to avoid having to route tons of extra (sensitive, matched) traces between the SDRAM and the CPU.

According to the mailing list posts, it seems to be incredibly difficult to solder the PoP stack due to the way TI has designed the packaging of the DM3730. If you want more gory details, see this post and yet another post.

It is very sad to see that what appears to be bad design choices at TI are going to bring the GTA04 project to a halt. The financial hit by having only 33% yield is already more than the small community can take, let alone unused parts that are now in stock or even thinking about further experiments related to the manufacturability of those chips.

If there's anyone with hands-on manufacturing experience on the DM3730 (or similar) TI PoP reading this: Please reach out to the GTA04 guys and see if there's anything that can be done to help them.

UPDATE (March 8, 2017):

In an earlier post I was asserting that the GTA04 is open hardware (which I actually believed up to that point) until some readers have pointed out to me that it isn't. It's sad it isn't, but still it has my sympathies.

In May 2016 we got the GTP-U tunnel encapsulation/decapsulation module developed by Pablo Neira, Andreas Schultz and myself merged into the 4.8.0 mainline kernel.

During the second half of 2016, the code basically stayed untouched. In early 2017, several patch series of (at least) three authors have been published on the netdev mailing list for review and merge.

This poses the very valid question on how do we test those (sometimes quite intrusive) changes. Setting up a complete cellular network with either GPRS/EGPRS or even UMTS/HSPA is possible using OsmoSGSN and related Osmocom components. But it's of course a luxury that not many Linux kernel networking hackers have, as it involves the availability of a supported GSM BTS or UMTS hNodeB. And even if that is available, there's still the issue of having a spectrum license, or a wired setup with coaxial cable.

So as part of the recent discussions on netdev, I tested and described a minimal test setup using libgtpnl, OpenGGSN and sgsnemu.

This setup will start a mobile station + SGSN emulator inside a Linux network namespace, which talks GTP-C to OpenGGSN on the host, as well as GTP-U to the Linux kernel GTP-U implementation.

In case you're interested, feel free to check the following wiki page: https://osmocom.org/projects/linux-kernel-gtp-u/wiki/Basic_Testing

This is of course just for manual testing, and for functional (not performance) testing only. It would be great if somebody would pick up on my recent mail containing some suggestions about an automatic regression testing setup for the kernel GTP-U code. I have way too many spare-time projects in desperate need of some attention to work on this myself. And unfortunately, none of the telecom operators (who are the ones benefiting most from a Free Software accelerated GTP-U implementation) seems to be interested in at least co-funding or otherwise contributing to this effort :/

I've recently attended a seminar that (among other topics) also covered RF interference hunting. The speaker was talking about various real-world cases of RF interference and illustrating them in detail.

Of course everyone who has any interest in RF or cellular will know about fundamental issues of radio frequency interference. To the biggest part, you have

• cells of the same operator interfering with each other due to too frequent frequency re-use, adjacent channel interference, etc.

• cells of different operators interfering with each other due to intermodulation products and the like

• cells interfering with cable TV, terrestrial TV

• DECT interfering with cells

• cells or microwave links interfering with SAT-TV reception

• all types of general EMC problems

But what the speaker of this seminar covered was actually a cellular base-station being re-broadcast all over Europe via a commercial satellite (!).

It is a well-known fact that most satellites in the sky are basically just "bent pipes", i.e. they consist of a RF receiver on one frequency, a mixer to shift the frequency, and a power amplifier. So basically whatever is sent up on one frequency to the satellite gets re-transmitted back down to earth on another frequency. This is abused by "satellite hijacking" or "transponder hijacking" and has been covered for decades in various publications.

Ok, but how does cellular relate to this? Well, apparently some people are running VSAT terminals (bi-directional satellite terminals) with improperly shielded or broken cables/connectors. In that case, the RF emitted from a nearby cellular base station leaks into that cable, and will get amplified + up-converted by the block up-converter of that VSAT terminal.

The bent-pipe satellite subsequently picks this signal up and re-transmits it all over its coverage area!

I've tried to find some public documents about this, an there's surprisingly little public information about this phenomenon.

However, I could find a slide set from SES, presented at a Satellite Interference Reduction Group: Identifying Rebroadcast (GSM)

It describes a surprisingly manual and low-tech approach at hunting down the source of the interference by using an old nokia net-monitor phone to display the MCC/MNC/LAC/CID of the cell. Even in 2011 there were already open source projects such as airprobe that could have done the job based on sampled IF data. And I'm not even starting to consider proprietary tools.

It should be relatively simple to have a SDR that you can tune to a given satellite transponder, and which then would look for any GSM/UMTS/LTE carrier within its spectrum and dump their identities in a fully automatic way.

But then, maybe it really doesn't happen all that often after all to rectify such a development...

In the good old days ever since the late 1980ies - and a surprising amount even still today - telecom signaling traffic is still carried over circuit-switched SS7 with its TDM lines as physical layer, and not an IP/Ethernet based transport.

When Holger first created OsmoBSC, the BSC-only version of OpenBSC some 7-8 years ago, he needed to implement a minimal subset of SCCP wrapped in TCP called SCCP Lite. This was due to the simple fact that the MSC to which it should operate implemented this non-standard protocol stacking that was developed + deployed before the IETF SIGTRAN WG specified M3UA or SUA came around. But even after those were specified in 2004, the 3GPP didn't specify how to carry A over IP in a standard way until the end of 2008, when a first A interface over IP study was released.

As time passese, more modern MSCs of course still implement classic circuit-switched SS7, but appear to have dropped SCCPlite in favor of real AoIP as specified by 3GPP meanwhile. So it's time to add this to the osmocom universe and OsmoBSC.

A couple of years ago (2010-2013) implemented both classic SS7 (MTP2/MTP3/SCCP) as well as SIGTRAN stackings (M2PA/M2UA/M3UA/SUA in Erlang. The result has been used in some production deployments, but only with a relatively limited feature set. Unfortunately, this code has nto received any contributions in the time since, and I have to say that as an open source community project, it has failed. Also, while Erlang might be fine for core network equipment, running it on a BSC really is overkill. Keep in miond that we often run OpenBSC on really small ARM926EJS based embedded systems, much more resource constrained than any single smartphone during the late decade.

In the meantime (2015/2016) we also implemented some minimal SUA support for interfacing with UMTS femto/small cells via Iuh (see OsmoHNBGW).

So in order to proceed to implement the required SCCP-over-M3UA-over-SCTP stacking, I originally thought well, take Holgers old SCCP code, remove it from the IPA multiplex below, stack it on top of a new M3UA codebase that is copied partially from SUA.

However, this falls short of the goals in several ways:

• The application shouldn't care whether it runs on top of SUA or SCCP, it should use a unified interface towards the SCCP Provider. OsmoHNBGW and the SUA code already introduce such an interface baed on the SCCP-User-SAP implemented using Osmocom primitives (osmo_prim). However, the old OsmoBSC/SCCPlite code doesn't have such abstraction.

• The code should be modular and reusable for other SIGTRAN stackings as required in the future

So I found myself sketching out what needs to be done and I ended up pretty much with a re-implementation of large parts. Not quite fun, but definitely worth it.

The strategy is:

• Implement the SCCP SCOC state machines for connection-oriented SCCP (of which Iu and A interface are probably the only users) using Osmcoom Finite State Machines (osmo_fsm).

• Migrate the existing SUA code on top of that, maintaining the existing osmo_prim based SCCP User SAP

• Implement SCCP to SUA and vice-versa message transcoding to makes sure the bulk of the code has to deal only with one message format (parsed SUA).

• Introduce a MTP SAP at the lower boundary of the SCCP code

• Implement xUA ASP and AS statemachines using osmo_fsm and add ASPTM/ASPSM support to SUA (was missing so far) * Implement

• Implement M3UA using the xUA ASP and AS FSMs as well as the general xUA message encoder/decoder, offering the MTP SAP toward SCCP

And then finally stack all those bits on top of each other, rendering a fairly clean and modern implementation that can be used with the IuCS of the virtually unmodified OsmmoHNBGW, OsmoCSCN and OsmoSGSN for testing.

Next steps in the direction of the AoIP are:

• Implementation of the MTP-SAP based on the IPA transport

• Binding the new SCCP code on top of that

• Converting OsmoBSC code base to use the SCCP-User-SAP for its signaling connection

From that point onwards, OsmoBSC doesn't care anymore whether it transports the BSSAP/BSSMAP messages of the A interface over SCCP/IPA/TCP/IP (SCCPlite) SCCP/M3UA/SCTP/IP (3GPP AoIP), or even something like SUA/SCTP/IP.

However, the 3GPP AoIP specs (unlike SCCPlite) actually modify the BSSAP/BSSMAP payload. Rather than using Circuit Identifier Codes and then mapping the CICs to UDP ports based on some secret conventions, they actually encapsulate the IP address and UDP port information for the RTP streams. This is of course the cleaner and more flexible approach, but it means we'll have to do some further changes inside the actual BSC code to accommodate this.

When implementing any kind of communication protocol, one always dreams of some existing test suite that one can simply run against the implementation to check if it performs correct in at least those use cases that matter to the given application.

Of course in the real world, there rarely are protocols where this is true. If test specifications exist at all, they are often just very abstract texts for human consumption that you as the reader should implement yourself.

For some (by far not all) of the protocols found in cellular networks, every so often I have seen some formal/abstract machine-parseable test specifications. Sometimes it was TTCN-2, and sometimes TTCN-3.

If you haven't heard about TTCN-3, it is basically a way to create functional tests in an abstract description (textual + graphical), and then compile that into an actual executable tests suite that you can run against the implementation under test.

However, when I last did some research into this several years ago, I couldn't find any Free / Open Source tools to actually use those formally specified test suites. This is not a big surprise, as even much more fundamental tools for many telecom protocols are missing, such as good/complete ASN.1 compilers, or even CSN.1 compilers.

To my big surprise I now discovered that Ericsson had released their (formerly internal) TITAN TTCN3 Toolset as Free / Open Source Software under EPL 1.0. The project is even part of the Eclipse Foundation. Now I'm certainly not a friend of Java or Eclipse by all means, but well, for running tests I'd certainly not complain.

The project also doesn't seem like it was a one-time code-drop but seems very active with many repositories on gitub. For example for the core module, titan.core shows plenty of activity on an almost daily basis. Also, binary releases for a variety of distributions are made available. They even have a video showing the installation ;)

If you're curious about TTCN-3 and TITAN, Ericsson also have made available a great 200+ pages slide set about TTCN-3 and TITAN.

I haven't yet had time to play with it, but it definitely is rather high on my TODO list to try.

ETSI provides a couple of test suites in TTCN-3 for protocols like DIAMETER, GTP2-C, DMR, IPv6, S1AP, LTE-NAS, 6LoWPAN, SIP, and others at http://forge.etsi.org/websvn/ (It's also the first time I've seen that ETSI has a SVN server. Everyone else is using git these days, but yes, revision control systems rather than periodic ZIP files is definitely a big progress. They should do that for their reference codecs and ASN.1 files, too.

I'm not sure once I'll get around to it. Sadly, there is no TTCN-3 for SCCP, SUA, M3UA or any SIGTRAN related stuff, otherwise I would want to try it right away. But it definitely seems like a very interesting technology (and tool).

Last weekend I had the pleasure of attending FOSDEM 2017. For many years, it is probably the most exciting event exclusively on Free Software to attend every year.

My personal highlights (next to meeting plenty of old and new friends) in terms of the talks were:

• 20 Years of Linux Virtual Memory by MM-Guru Andrea Arcangeli

• GPU-Enabled Polyphase Filterbanks by Jan Kraemer

• Virtual multi-antenna arrays for estimating the bearing of radio transmitters by Francois Quitin

• Secure Microkernel for Deeply Embedded Devices by Jim "jserv" Huang

• A discussion of Fedora's Legal state by Tom Callaway

• Radio Lockdown Directive by Max Mehl

I was attending but not so excited by Georg Greve's OpenPOWER talk. It was a great talk, and it is an important topic, but the engineer in me would have hoped for some actual beefy technical stuff. But well, I was just not the right audience. I had heard about OpenPOWER quite some time ago and have been following it from a distance.

The LoRaWAN talk couldn't have been any less technical, despite stating technical, political and cultural in the topic. But then, well, just recently 33C3 had the most exciting LoRa PHY Reverse Engineering Talk by Matt Knight.

Other talks whose recordings I still want to watch one of these days:

• Smart Card Forwarding

• AF_KTLS - TLS/DTLS Linux kernel module

• Overview of gr-inspector

• Frosted Embedded POSIX OS

I'm very happy that in 2017, we will have the first ever technical conference on the Osmocom cellular infrastructure projects.

For many years, we have had a small, invitation only event by Osmocom developers for Osmocom developers called OsmoDevCon. This was fine for the early years of Osmocom, but during the last few years it became apparent that we also need a public event for our many users. Those range from commercial cellular operators to community based efforts like Rhizomatica, and of course include the many research/lab type users with whom we started.

So now we'll have the public OsmoCon on April 21st, back-to-back with the invitation-only OsmoDevcon from April 22nd through 23rd.

I'm hoping we can bring together a representative sample of our user base at OsmoCon 2017 in April. Looking forward to meet you all. I hope you're also curious to hear more from other users, and of course the development team.

Regards,

Harald

A few days ago, Autodesk has announecd that the popular EAGLE electronics design automation (EDA) software is moving to a subscription based model.

When previously you paid once for a license and could use that version/license as long as you wanted, there now is a monthly subscription fee. Once you stop paying, you loose the right to use the software. Welcome to the brave new world.

I have remotely observed this subscription model as a general trend in the proprietary software universe. So far it hasn't affected me at all, as the only two proprietary applications I use on a regular basis during the last decade are IDA and EAGLE.

I already have ethical issues with using non-free software, but those two cases have been the exceptions, in order to get to the productivity required by the job. While I can somehow convince my consciousness in those two cases that it's OK - using software under a subscription model is completely out of the question, period. Not only would I end up paying for the rest of my professional career in order to be able to open and maintain old design files, but I would also have to accept software that "calls home" and has "remote kill" features. This is clearly not something I would ever want to use on any of my computers. Also, I don't want software to be associated with any account, and it's not the bloody business of the software maker to know when and where I use my software.

For me - and I hope for many, many other EAGLE users - this move is utterly unacceptable and certainly marks the end of any business between the EAGLE makers and myself and/or my companies. I will happily use my current "old-style" EAGLE 7.x licenses for the near future, and theS see what kind of improvements I would need to contribute to KiCAD or other FOSS EDA software in order to eventually migrate to those.

As expected, this doesn't only upset me, but many other customers, some of whom have been loyal to using EAGLE for many years if not decades, back to the DOS version. This is reflected by some media reports (like this one at hackaday or user posts at element14.com or eaglecentral.ca who are similarly critical of this move.

Rest in Peace, EAGLE. I hope Autodesk gets what they deserve: A new influx of migrations away from EAGLE into the direction of Open Source EDA software like KiCAD.

In fact, the more I think about it, I'm actually very much inclined to work on good FOSS migration tools / converters - not only for my own use, but to help more people move away from EAGLE. It's not that I don't have enough projects at my hand already, but at least I'm motivated to do something about this betrayal by Autodesk. Let's see what (if any) will come out of this.

So let's see it that way: What Autodesk is doing is raising the level off pain of using EAGLE so high that more people will use and contribute FOSS EDA software. And that is actually a good thing!

Yesterday, together with Holger 'zecke' Freyther, I co-presented at 33C3 about Dissectiong modern (3G/4G) cellular modems.

This presentation covers some of our recent explorations into a specific type of 3G/4G cellular modems, which next to the regular modem/baseband processor also contain a Cortex-A5 core that (unexpectedly) runs Linux.

We want to use such modems for building self-contained M2M devices that run the entire application inside the modem itself, without any external needs except electrical power, SIM card and antenna.

Next to that, they also pose an ideal platform for testing the Osmocom network-side projects for running GSM, GPRS, EDGE, UMTS and HSPA cellular networks.

You can find the Slides and the Video recordings in case you're interested in more details about our work.

The results of our reverse engineering can be found in the wiki at http://osmocom.org/projects/quectel-modems/wiki together with links to the various git repositories containing related tools.

As with all the many projects that I happen to end up doing, it would be great to get more people contributing to them. If you're interested in cellular technology and want to help out, feel free to register at the osmocom.org site and start adding/updating/correcting information to the wiki.

You can e.g. help by

• playing with the modem and documenting your findings

• reviewing the source code released by Qualcomm + Quectel and documenting your findings

• help us to create a working OE build with our own kernel and rootfs images as well as opkg package feeds for the modems

• help reverse engineering DIAG and QMI protocols as well as the open source programs to interact with them

I've just had the pleasure of attending all four days of 33C3 and have returned home with somewhat mixed feelings.

I've been a regular visitor and speaker at CCC events since 15C3 in 1998, which among other things means I'm an old man now. But I digress ;)

The event has come extremely far in those years. And to be honest, I struggle with the size. Back then, it was a meeting of like-minded hackers. You had the feeling that you know a significant portion of the attendees, and it was easy to connect to fellow hackers.

These days, both the number of attendees and the size of the event make you feel much rather that you're in general public, rather than at some meeting of fellow hackers. Yes, it is good to see that more people are interested in what the CCC (and the selected speakers) have to say, but somehow it comes at the price that I (and I suspect other old-timers) feel less at home. It feels too much like various other technology related events.

One aspect creating a certain feeling of estrangement is also the venue itself. There are an incredible number of rooms, with a labyrinth of hallways, stairs, lobbies, etc. The size of the venue simply makes it impossible to simply _accidentally_ running into all of your fellow hackers and friends. If I want to meet somebody, I have to make an explicit appointment. That is an option that exits most of the rest of the year, too.

While fefe is happy about the many small children attending the event, to me this seems somewhat alien and possibly inappropriate. I guess from teenage years onward it certainly makes sense, as they can follow the talks and participate in the workshop. But below that age?

The range of topics covered at the event also becomes wider, at least I feel that way. Topics like IT security, data protection, privacy, intelligence/espionage and learning about technology have always been present during all those years. But these days we have bloggers sitting on stage and talking about bottles of wine (seriously?).

Contrary to many, I also really don't get the excitement about shows like 'Methodisch Inkorrekt'. Seems to me like mainstream compatible entertainment in the spirit of the 1990ies Knoff Hoff Show without much potential to make the audience want to dig deeper into (information) technology.

In 2016, Osmocom gained initial 3.5G support with osmo-iuh and the Iu interface extensions of our libmsc and OsmoSGSN code. This means you can run your own small open source 3.5G cellular network for SMS, Voice and Data services.

However, the project needs more contributors: Become an active member in the Osmocom development community and get your nano3G femtocell for free.

I'm happy to announce that my company sysmocom hereby issues a call for proposals to the general public. Please describe in a short proposal how you would help us improving the Osmocom project if you were to receive one of those free femtocells.

Details of this proposal can be found at https://sysmocom.de/downloads/accelerate_3g5_cfp.pdf

Please contact mailto:accelerate3g5@sysmocom.de in case of any questions.