GSoC 2018 – Better map for nodewatcher (2nd update)

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LibreNet6 – update 2

This is an quick update on my work on LibreNet6 and LibreMesh within the last weeks. The exam period in Tokyo started and I had a cold which slowed me a bit down, once both passed I will focus with doubled concentration on the project again!

Multiple servers

The approach of using Tinc allows the usage of more then one IPv6 server, allowing to connect the servers of multiple communities with different IPv6 subnets. Babeld automatically detects where to route traffic when using external subnetworks. This is fortunate as it is possible that there is a high latency between mesh gateway and IPv6 server which would slow down traffic. However, using Tinc and babeld I ran a setup with two mesh gateways both using two different IPv6 subnets. While pings to the other network had high latencies at first (me in Tokyo, one IPv6 server in London and one in Argentina), Tinc automatically exchanged the IPv6 addresses of the mesh gateways which then could connect directly, lowering the latencies. Summarizing this experiment, using Tinc makes the network independent of the public IPv6 addresses.

No lime-app plugin

Initially I though of creating a lime-app plugin which allows to easily requests access to a Tinc mesh. However, after an evolution with my mentor and reading more about Tinc, we decided against it: The new 1.1 release of Tinc not only simplifies joining a mesh by offering the invite and join commands, but also allows to do all configuration automatically with the help of an invitation file. These new features simplify the project much more then I though, following the Spanish documentation on Altermundi.

Adding some security

As mentioned above some parts where easier as excepted, I though of looking into additional tasks for the project. Currently the usage of babeld requires all users of the mesh to fully trust one another as babeld does not provide any security (I could find) regarding announced routes. Mesh routing with security is offered by BMX7, which introduces a model to set (dis)trust between nodes. For this reason I’ve been in contact with Axel Neumann, the developer of BMX7, to fix an long standing error in OpenWrt which lead to false MTU rates in BMX7. The fix was merged upstream and thereby allows to test BMX7 over Tinc as a secure babeld alternative.

English documentation

Beneath the experiments I’ve started to translate (and simplify) the Spanish documentation of LibreNet6 and will upload it to the GitHub repository once finished. Important part is also how to configure 6to4 tunnels as surprisingly few VM providers offer any IPv6 connectivity per default but only a single public IPv4 address.

nodewatcher: Build system rework and package upstreaming – Second update

Hi,

Last weeks have been spent solely on reworking the build system.

First, it was a matter of rebranding the current LEDE back into OpenWrt and fixing a couple of hard-coded names that would cause issues with OpenWrt name. It also involved dropping the old OpenWrt build system which has not been used for years and most likely never will again, so that removes unnecessary code to maintain.

After rebranding, I spent some time verifying that the whole system still works.
Fortunately, there were only small bugs which were simple to fix.

And then came the main task of this project, to completely rework and massively simplify the whole building the image builder job a lot easier and resource intensive.

Firstly, since I was still gonna use Docker to images for a build environment updating the base image which is the actual build environment was needed from old Trusty 14.04 to fresh 18.04 Bionic. This proved to be mostly trial and error as a lot less of default packages were included in 18.04 so getting all dependencies working. After a while base image is now working fine and is relatively small, actually smaller than 14.04 base image.
This is due to less unnecessary packages.

Once the base image was sorted out I finally got working on dropping the unnecessary scripts, docker files and all of the hardcoded build files.

This proved to be not so hard, so work on a new docker based build system started.

So far it’s broken into only 4 separate scripts:

  1. docker-prepare-build system: Like its name hints it builds the base image and installs the needed packages. I am still thinking to maybe pull this from the auto built image on Docker Hub.
  2. generate-docker files: Which generates the temporary docker files needed for building inside a Docker 18.04 base image.
  3. docker-build: Which actually “builds” the image builder and SDK.
  4. build: Main script, which simply calls others to configure and build everything.

Number of scripts will most likely grow by one or two since the built image builder with all of the packages need to be packaged and then deployed in a runtime specific image which will only contain the bare minimum of packages to keep it as lightweight as possible.

Currently, building works fine for most custom packages using SDK, but its stuck at building ncurses with a weird LC_TIME assertion error which I need to fix.

So next period will be strictly for fixing the bugs and finishing the build system.
After that is done I will update the custom packages and try to get them upstreamed.

GSoC 2018 – DAWN a decentralized WiFi controller (2st update)

Hi,
I still try to get my patches upstream.
For the libiwinfo patch I had to add the lua bindings. I never used lua so first I had to get comfortable with this. Additionally I wanted to add the channel utilization in the luci statistics app. But suddenly Luci is giving me a null pointer exception in the dev branch.


Additionally I tried to get comfortable with Luci for developing my own app.
Meanwhile another developer created nearly the same patch for iwinfo that add the survey data for the nl802.11 driver… This patch is still not accepted. The only difference is that it returns all survey data for all channels (like iw dev wlan0 survey dump)…
Furthermore, my pull request for the hostapd ubus bindings that add information about the ht and vht capabilities had to be rewritten. (https://github.com/openwrt/openwrt/pull/898). Again I have to wait for some feedback. While rewriting this patch, I had a new idea: If you subscribe to the hostapd via ubus and want to notify on the messages you have to activate it. It would be possible to add flags in the hostapd_ubus_bss to select what information should be published via the ubus bus. Before doing so, I want some feedback if this is a good idea.If somebody is interested why I am interested in the capabilities: I want to create a hearing map for every client. I’m building this hearing map using probe request messages. This probe request messages contain information like (rssi, capabilities, ht capabilities, vht capabilities, …). VHT give clients the opportunity to transfer up to 1,750 Gigabits (theoretical…) If you want to select some AP you should consider capabilities… In the normal hostapd configuration you can even set a flag that forbids 802.11b rates. If you are interested what happens if a 802.11b joins your network search for: WiFi performance anomaly. 🙂

Summarizing, I spent a lot of time waiting for feedback, debugging, modifying my patches or replying on the email lists. It is a bit frustrating.
The cool stuff was that I had my first pull request. 🙂 (it was just a typo ^^) But somebody took the time to fork my project and create a pull request. 😉
Furthermore, it is exam time and I have a lot of stuff to do for the university.

Actually I wanted to go on with more interesting stuff like connecting to the netifd demo to get more information.

Or to look at PLC. There is an interesting paper EMPoWER Hybrid Networks: Exploiting Multiple Paths over Wireless and ElectRical Mediums.

 

VRConfig Update 2

Hi,

I spent the last weeks mainly developing the LuCI Application for VRConfig. As soon as you want to do advanced things with LuCI, it gets cumbersome.
As the API is mostly undocumented, you have to dig through the LuCI’s source code trying out functions which could be useful according to their name.
It’s a bit of a trial and error game.
Currently the LuCI app does the following.
It displays an image of the router and parses the JSON file, which contains the locations of the components.
With this information it can mark the associated physical ports to the currently selected network interface and display those network ports, which are connected to a cable. You can also hover over the components and click on them, which leads you to their respective settings page.

I also improved the annotation app. It now lets you choose the router name from a list of all currently supported router models of OpenWrt. I got that list with a series of grep and sed commands from the OpenWrt git repository.
For your information, there are currently around 1100 different router models supported. 🙂

In the next weeks I will polish the LuCI Application and try to integrate VRConfig into the openwrt build system to be able to select the correct router image and JSON file at build time.

GSoC 2018 – Easily Expandable WIDS – Second Update

In this blog post I’d like to present the recent progress made for Eewids. This time, our main focus was the performance of the current setup. Besides we did some minor improvements, mostly adding some more dashboards to Grafana to visualize the data captured. This blog post focuses the results regarding Kismet as a component of Eewids. Continue reading “GSoC 2018 – Easily Expandable WIDS – Second Update”

OpenWLANMap App: Update 2

Hi,

In the last weeks I was working on  the storing process as described in the architecture in the last blog post [0].

Storage Handler:

Old app: the old app saves the data as byte in a file. A data entry is 28 bytes of MAC-address(12 bytes for 12 characters) and latitude(8 bytes for double) and longitude(8 bytes for double). An entry could be saved more than once in the file. There are 2 files, one for data which should be updated and one for data which should be deleted from backend.

New app: Firstly I wanted to adapt the structure from the old app. But since I saw some unreasonable points such as saving redundant data, flash workload, maintenance problem and unstructured storage, I decided for a standard database with more structure and easy to maintain: sqlite. Also I am using the new persistence lib, which provides an abstract layer for database: Room, newly released last year, as a part of android architecture components, with a lot of bug fixed since then. A lib with a lot of advantage when working with sqlite database: verify queries at compile time, reduce a lot of duplicate code in comparison with the last approach with DbHelper etc. In order to store the access point in the database, I implemented a seperate thread, which reads data from a blocking queue and saves it in the database, which works parallel with the scan thread and will be interrupted if there is nothing in the queue to store. Also to save energy and not force the store thread to run the whole time, a list of access points will be put into the blocking queue as an element. To pretend redundant data in storage, a data entry with BSSID will not be saved many times as in the old app but only once. The BSSID is used as primary key in the sqlite table. It will be updated the next time if the received signal strength is better than the last entry in the database. An explicit transaction is implemented to solve this case since the lib Room has only supported annotation for standard update/insert. To decide if a access point should be deleted or updated from backend, a flag is set.

Upload Handler:

The WifiUploader is in process. I did take a look at the uploading format in the old app and how it communicates with the current backend. Also the upload sequence is already defined, mean the scanning thread will be interrupted, all the rest of access point will be stored, the store thread will be interrupted to pretend conflict while 2 threads try to access same database at the same time before the uploading process is started. Also the WifiUploader will read maximum a number of data entries from the database and upload it, not the whole database like old app but one after another,  in order to pretend out-of-memory problem at device with small ram. (see more in the below diagram)

flowchart of uploading process

 

But since I am in the middle of my final exam period, there will be a small delay until this weekend for the WifiUploader to be published. Also from next week I will spend full time making the other features done includes implementing all saving resource features such as adaptive scanning, implementing all settings option. A clean and full documentation will be provided at the end as well.

Available issue: Permission request and handling

[0] https://blog.freifunk.net/2018/06/10/openwlanmap-app-update-1/

WiFi Direct and Bluetooth Meshing

As hinted in my last blog article, for us to really be able to move forward we needed to do some experimentation with the new technologies we have to adapt. The primary candidate in the beginning of that phase was WiFi Direct, a type of WiFi mode setting which is an official standard published by the WiFi consortium which is meant to replace the ad-hoc wifi mode. But only partially: WiFi Direct was mostly designed to make integration with IoT products easier. As such, using it for the meshing applications is a bit outside of it’s primary use case. The idea behind it is to make two WiFi devices talk to each other without needing a router to be the middleman for negotiation and frequency selection. Even groups of devices are possible create, electing a group leader that then manages the group.

Unfortunately…that sounded a lot better in theory than it turned out to be in practice.

Also as hinted in my last blog post we built some little prototype applications to test WiFi direct between multiple devices and ran into some issues. The APIs that are provided by Android are okay to use, but not super convenient. But most of the issues come from bugs that we haven’t exactly been able to trace down yet. The system WiFi Direct interface (System Settings > WiFi > Advanced > WiFi Direct) detects all devices in the vicinity whereas our application, using the WiFi Direct interface in the Android SDK would sometimes (nondeterministically) fail to detect devices or open sessions between them. We also had some bad experience creating groups between the devices.

All in all…it was underwhelming. WiFi Direct really wasn’t meant to do the kind of networking we’re trying to do with it and even if we can figure out the bugs we encountered, there are other concerns to work out. Debugging these issues aren’t easy but there are a few things we can do. For one, there are other (open source) applications that exist (serbal, briar, …) that use this technology and we can study to see how they solved these issues. There is also the option of wireshark-ing packets that are being transmitted between the two devices to get a better understanding of where handshakes are going wrong. Simple debugging via Android/ Java debugger unfortunately hasn’t yielded many useful results.

We need a convenient way for people to be able to join the network. We need to figure out a way to create a captive portal for people just connecting without the software. The handoff between a WiFi Direct network section and a legacy ad-hoc section that might be created between infrastructure nodes that don’t support WiFi Direct. The last week or so I’ve had my head in the WiFi Direct specification, trying to answer these questions. And while I think we have solved most problems, there’s still a few left to answer.

The second technology we are investigating to complement WiFi Direct wherever it isn’t applicable is Bluetooth P2P Meshing. In contrast to WiFi Direct, it was actually developed for devices to mesh with each other which makes the adaptation of it easier for us in the long run. So far we’ve only done some simple experiments with 2 devices (due to a lack of Android devices in one location 😉 ) but these have been a lot more promising than what WiFi Direct has offered.

The biggest take-away from the last 2 weeks of experimentation is that we can’t dedicate the routing core to a single networking backend.

In the design of the actual code interface that I’ve built in the first few weeks of GSoC this means that there are some adjustments to be made before writing more code. This includes being more generic when binding interfaces and allowing a client to use multiple backends at the same time. This was not intended to be used in the initial design. But for the time being those interfaces will simply be mocked by some stub methods or maybe a simple simulation so we can test the actual routing algorithms. This is an interesting challenge because so many parts of qaul.net will have to change in lockstep with each other to make it all work.

There are some corner cases to test when it comes to bluetooth mesh networking such as groups and how they handle devices joining in and out of them

The Turnantenna – Second evaluation update

Time is passing, and work is proceeding.

Last month I reported a problem concerning speed of our beloved Turnantenna: the acceleration was not constant during movement of the stepper engine, as I wanted. The error was caused by implementation of a bad algorithm. A constant acceleration is important to provide a smoother movement, and is needed to reduce the load on the engine. Force is equal to mass times the acceleration; if the acceleration is constant, so is the force; but if the acceleration grows, the stepper’s force grows as well, as long as it can keep up. Uncontrollable acceleration lead to unpredictable forces (or better, toques).

To understand the issue, a brief summary should be given: the way to control the stepper’s speed consists of changing the time between two consecutive steps. The shorter the time, the faster the movement. The previous (and wrong) algorithm, is documented in the older post. It wasn’t a good way to control a torque-limited engine because, as said before, the acceleration was not constant. In the previous algorithm, speed was taken like this:

vn = vn-1 + const

namely, at time tn the speed was a fixed amount more than tn-1.
Time between two steps was

dt = (n – n-1)/vn = 1 / vn

It may appear correct, but the resulting graph was the following:

As can be seen, the speed is not linear. This mean that the acceleration is not constant, but increasing.

I found a solution thanks to a document written by Atmel Corporation. It made me think about the relationships between speed (v), space (s), time (t) and acceleration (a) that comes from physics laws:

s = a ½  t² + v₀ * t + s₀

this equation is always true, when accelerating, when the speed is constant, and even when decelerating. Quantities change inside the formula, but it always remain true.

Now, to keep it simple, let’s consider the first phase: the acceleration. A the beginning of its movement, the engine is still (v0 = 0), and it starts without having already done one single step (s0 = 0). The resulting equation is evaluated at v₀ =0  and s₀= 0:

s = a ½  t² + 0 * t + 0
s = a ½  t²

Now, let’s think about what is known: the acceleration a, that it is constant (because I want it so), s and t; s is the number of steps already done at time t. If I know how many steps -s- I have to do I can find how much time I have to wait –t-, and vice versa.

To find the time between two steps (the step #n and the step #n+1) the formula is:

s = a ½  t²
==>  t = sqrt(2 * s / a)

# at the step number ‘n’
tn = sqrt(2 * n / a)

# time between step ‘n’ and ‘n+1’
dt = tn-1 – tn = sqrt(2 / a) * (sqrt(n+1)-sqrt(n))

Using this calculation, acceleration is constant, and speed increases linearly, as it can be seen in the graph below:

AAAAAH.. a perfect blue line! 😀

Problem: Solved!

Working on tests

Now, more progresses have been done in tests. For those who don’t knows, I’ve started my programming adventure with with this project. Everything for me is anexciting discovery, and during this month I learned and implemented the “argparse” and “logging” libraries. Now it is possible to execute the tests with three verbose levels: the first is silent, the second shows debugging informations and the third shows the info level.
It could appear trivial, but I’d never done it before, and now tests are smarter!

It is not all: I reviewed all the tests, fixed problems and improved their reliability. They’re still not perfect, but I’m working on them daily to get details right.

Fly across borders

It was time to go outside the boundaries, and to think about an interface that bring into communication the web interface and the driver. This is what I’m working on in these days.

To achieve that goal, the problem has to be studied starting from an high level. The main process, which is constantly running, float between a small number of determined states: initialising, still, moving and error handling. Together with the Ninux Florence developers community I built the following state machine graph:

This was realized with the GraphMachine module of the “transmissions” library. Now I’m working on the full representation of this map in code lines. But there is something more.. In fact, at this point, multiprocessing became necessary to provide a safe environment: when the engine is in the MOVING state, for example, and a new command is sent to make a new different rotation, the main process should have the possibility to manage simultaneously the ongoing movement and newer requests.

That’s why we choose to keep the main process always active and make it decide when to run the movement procedure in a dedicated process, like a traffic light.

Turnantenna.me

The greatest effort, this month, was done writing down a full, detailed documentation of the project. 80 pages on what is the Turnantenna, how it works, and when and why to use it.

Many people expressed their interest in the project, someone has offered to support us but, without a complete documentation available, it is difficult to provide a starting point.

The whole doc will be soon available, and this post will be updated with the dedicated link. So, if you are interested in the project, let us know! For the moment, GitHub repository is available here.

See you next month!

— UPDATE —

The link of the full documentation of the project is provided below.
turnantenna.readthedocs.io

Meshenger – P2P local network messenger – Update 2

Just a few days after the first update I figured out how to use WebRTC, which I shortly after implemented into Meshenger.

To shortly describe the way signalling is working in my app:

  1. On phone A a call to phone B is issued by tapping the contact, hence phone A already knows the destination address
  2. A sends a call request to B, which B may accept or decline. This is done through a custom JSON-based protocol designed by me
  3. In case of success A creates a Session Description, also called SDP offer, which it transmits to B, using the same protocol
  4. B creates an SDP answer which it transmits back to A, still using my JSON-based protocol
  5. Using the exchanged offer and answer a RTCPeerconnection is established, where the data is transmitted through separate DataChannels/Streams. Upon this moment, WebRTC handles all the communication
  6. Finally, the phones have a RTCPeerconnection which they use to send Audio/Video as well as service messages, e.g. when a camera is connected

 

Besides the sheer implementation of WebRTC the front/back camera can be turned on and even switched on the fly.

The app has undergone some graphical improvements, all buttons containing text has been replaced with Image Buttons,

many of them even show a animation depending on their effect.

 

I even tried to cover the case of the user switching a network, if the link-local address loses its reachability.

Instead of simply trying to reach the last known address, the app now examines every address the phone has

and tries to replace its own MAC address in those addresses with the MAC of the target.

This leads to a higher chance of re-finding a contact even if the phones have switched networks.

 

As you can see in the following screenshot, bidirectional video-transmission is enabled, and the buttons at the bottom now have cute icons.

 

Phone A
Phone B

 

 

 

 

 

 

 

 

 

 

 

From now on I will focus on polishing the app, cleaning the source code, finding and resolving bugs and,

last but not least, writing sufficient documentation.

I may even write a blog post somewhere, explaining how to archieve a serverless WebRTC connection,

since the documentation i have found so far was not really helpful and mainly focused on JavaScript.