Fighting Buffer Bloat With OpenWrt and Traffic Shaping

Earlier this year, I discovered ‘wondershaper‘ a great Linux tool that configures traffic shaping on my notebook to fight buffer bloat on an upstream router. Without it, video calls and other interactive Internet use become impossible to use on some connections when sending large amounts of data in the uplink direction. This works on a device basis, so several devices in the local network, all sending data to the Internet at the same time, can still cause buffers to bloat in unsophisticated access routers. The solution: Apply traffic shaping on a local Wi-Fi access point that is inserted before the router where the bloat happens. It turned out that configuring traffic shaping on OpenWrt is a piece of cake!

Continue reading Fighting Buffer Bloat With OpenWrt and Traffic Shaping

My Codium Weekend

Apart from having fun and providing useful software for researchers, my quality time software project I’ve been working on for almost a decade, is to stay up to date with the latest software development methods and tools. Earlier this year, I’ve switched my development environment and deployment method to Docker containers. Once set up, this made my software development routine much easier and users of my Document Research Database software can swiftly install an instance from Gitlab on a server of their choice. While the software is in constant evolution, one thing however has remained the same throughout: The development environment. So far, I’ve been using Eclipse, as once upon a time, that was the standard development environment for PHP. But things have changed over the years and VSCode now seems to be the preferred editor for software developers. And indeed, it looks very nice. Unfortunately, it has one major flaw: It’s maintained by a company that, like no other, stood for fighting against Linux and open source.

Continue reading My Codium Weekend

Wireguard, OpenWrt and a Linksys Router

One VPN technology I wanted to try out for quite some time now is Wireguard. Everybody I talk to about the topic speaks very highly of it but unfortunately, the stable version was just released a bit too late for proper NetworkManager support to be included in Ubuntu 20.04 last year. While I could live with a couple of scripts to establish and tear down a tunnel to my home network, that’s unfortunately not an option for others I work with. But then I remembered that OpenWrt, the open source Linux operating system for embedded network devices such as Wi-Fi access points, has support for the protocol. And as I just needed to update a Linksys WRT-1200 AC Wi-Fi Router to the latest OpenWrt version anyway, I used the opportunity to gain some experience with the protocol along the way.

Continue reading Wireguard, OpenWrt and a Linksys Router

My New Thinkpad X13 with 16 CPU Threads – First Impressions

O.k. I admit it, the sheer performance of video calls on current notebook processors made me go for a new instead of a used notebook, as incidentally, a couple of other unforeseen developments required the move anyway. So instead of buying a used Lenovo X270 with a 7th generation Intel processor from 2017 with 2 cores and 4 CPU threads, I went for a new Thinkpad X13 Gen 1 from 2020 with an AMD Ryzen 7 4750U CPU with 8 cores and 16 CPU threads. So here’s the story of how that went.

Continue reading My New Thinkpad X13 with 16 CPU Threads – First Impressions

Booting From /dev/sdb

When installing a new OS, I am quite used to booting a computer from a USB drive. However, from way back in the days I faintly remember that connecting a drive with an installed Linux system with a SATA to USB adapter to a notebook / server would not work. Particularly so when the notebook / server already contains a disk drive that uses the default SATA port (/dev/sda). But I recently discovered that things have become way better these days!

Continue reading Booting From /dev/sdb

Routing it Your Way Part 3: Socat for OpenVPN Forwarding

O.k., I’m going deeper and deeper down the layer 7 routing rabbit hole. As I like to have a plan B when it comes to my infrastructure at home, I have backup Internet connectivity over a separate Internet connection and a separate router. When main connectivity fails, a script detects that my services are no longer reachable. It then changes the DynDNS entries of all domains I use at home to point to the IP address of the backup connectivity. So far, so good.

But here is the catch: Backup connectivity is routed through a VM on the Internet that terminates ssh reverse port mapping tunnels from my VMs at home. These tunnels do not use the main Internet link so they don’t break when connectivity is lost. Instead, the VMs at home have an entry in the routing table for the IP address of the cloud VM that points to the backup connectivity router. This works great but has one major shortcoming: ssh can only tunnel TCP ports. Unfortunately, OpenVPN and similar products use UDP as transport protocol, and hence, ssh tunneling doesn’t work. But there’s another way!

Continue reading Routing it Your Way Part 3: Socat for OpenVPN Forwarding

Routing it Your Way Part 2: ssh + socat to Simplify Tunneling

In a previous post I’ve described of how ssh reverse tcp forwarding and socat forwarding can be used in combination to make the services of a server without a public IP address and no ssh access available to the outside world. The setup requires two intermediate gateway servers, one on the Internet and one in the local network. On the one hand, this is complicated but on the other hand offers a number of interesting simplifications if you have more than just one server in your local network that you want to expose to the world. Let me explain…

Continue reading Routing it Your Way Part 2: ssh + socat to Simplify Tunneling

Routing It Your Way Part 1: ssh + socat

Every now and then I get questions that make me think in new directions and the results are often useful far beyond the original intent. Here’s an example: For many years I’ve been using ssh reverse tcp port forwarding to make servers available on the Internet that are behind a NAT, for example in a home network without a public IP address. Here’s my original post from back in 2014 and here’s a post about a talk I gave on the topic in 2019. But what if one can’t initiate an ssh tunnel from the server behind the NAT? Well, I have a solution for that as well now: Combining ssh and socat!

Continue reading Routing It Your Way Part 1: ssh + socat