N E M E S I S

The Resurrection

Summer is almost upon us. The weather in Sweden has been amazing the last couple of weeks, sunny and warm. This has of course not prevented me from pursuing my favorite indoor activity; coding! This time around I’ve spent some time to resurrect the packet injection tool Nemesis.

[Read More]

Slow Down

Anyone who knows me knows I’m quite stubborn. Whenever I set my sights on something I finish it. The last couple of years I’ve been quite busy on GitHub, making at least one commit per day. I’ve had a lot of things I’ve wanted to do and complete, and this commit regimen has kept me on track to do just that. However, nothing comes for free, and although I’ve achieved my goals, I’ve also had to make a lot of sacrifices. [Read More]

Multicast routing with PIM-SM over GRE

GRE tunnels are useful in many ways. This blog post shows how to set up multicast routing with pimd over a GRE tunnel. To achieve this we will also set up OSPF over GRE with Quagga, because PIM, unlike DVMRP (mrouted), require unicast routing rules to be established.

       .----{ Intranet }----.
      /    192.168.1.0/24    \
     /                        \
.10 /                          \.20
.--'---. .1  GRE Tunnel  .2 .---`--.
|      |====================|      |
|  R1  |   172.16.16.0/30   |  R2  |
|      |                    |      |
'--.---'                    '------'
   | .1                        | .1 
   |    10.0.1.0/24            |    10.0.2.0/24
   | .2                        | .2 
.--'---.                    .--'---.
|      |                    |      |
|  C1  |                    |  C2  |
|      |                    |      |
'------'                    '------'

In this post we are using the home WiFi network, 192.168.1.0/24, to hook up the GRE tunnel. It is just as easy to extend this to a big corporate Intranet with more routers between R1 and R2. As long as that IT department takes care of the unicast routing between R1 and R2 so that the GRE tunnel can be established.

[Read More]

Useful UNIX API:s

Had an interesting conversation with a buddy last night. It started out as a shift-reduce problem with Bison and ended up a ping-pong of useful UNIX API:s. We concluded that despite having worked professionally with UNIX for over a decade, it is still very satisfying finding gems like these.

Most people are completely unaware they exist and end up rolling their own (buggy) implementations. For instance, string manipulation and various forms of linked lists. Which is why I many years ago extracted the frog DNA from Finit to a separate library called libite, or -lite for short. It imports the OpenBSD strlcpy() family of API:s, up-to-date queue.h with the _SAFE iterators, and more. Some people like libbsd for this, but I’ve found many of the ports incomplete and unsafe and prefer to stay closer to the upstream *BSD versions.

Update: This post was originally written Nov 14, 2015. It was a Saturday and I remember being extremely inspired when I wrote it. I’ve continued adding to it over the years, and still do. So, as of Jul 2, 2017 I’m bumping the modification date each time I add something new :-)

[Read More]

Set up a Debian/Ubuntu APT Repository

How to set up a Debian/Ubuntu APT repository with GPG signing.

At first I tried to use Bas Wijnen’s mini-dinstall howto, but never managed to get it working. Probably due to problems with GPG. Then I went down the tried and true path of using reprepro.

I’ve tried to document my steps here, but I’ve very likely missed a few steps that a beginner admin may run into. YMMV B-)

[Read More]

Threads vs Event Loop, Again ...

I still get asked this, from time to time. Maybe it’s because I only use event loops, maybe it’s because I’ve written libuEv, or maybe people still don’t understand:

Why an event loop, why not use threads?

So here’s my response, once more.

[Read More]