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Crafting ICMP-bearing IPv4 packets with the help of bitvec

Dec 12, 2019

35 min #networking · #icmp · #rust · #ip · #parsing

So. Serializing IPv4 packets. Easy? Well, not exactly.

IPv4 was annoying to parse, because we had 3-bit integers, and 13-bit integers, and who knows what else. Serializing it is going to be exactly the same.

Right now, we don’t have a way to serialize that.

Let’s take the version and ihl fields, both of which are supposed to take 4 bits, together making a byte. We could serialize them like this:

Thumbnail for Day 13 (Advent of Code 2022)

Program in C (Parody song)

Oct 31, 2019

1 min #song

Once upon a time, @Cinememer wrote some alternative lyrics to “Under The Sea”. I couldn’t resist singing them!

I unfortunately lost the audio files for this. Oh well.

Instrumental (Neverland Orchestra)

Isaac rubs his back on non-existent doors

Mar 20, 2013

4 min #gamedev · #programming

Haven’t blogged in a while. Life’s fine, project are a-plenty, but I just wanted to make a more lasting post about one particular issue that struck me as funny when programming Paper Isaac.

What’s infuriating when letting others play an early prototype is that you hear constantly the same things. Some bugs are non-trivial to fix, some you’re just not motivated to fix now… sometimes you just have your head elsewhere, gotta focus, or are elbow-deep in some other piece of code and the damn walls can wait.

Game Design: The Binding of Isaac

Jun 22, 2013

3 min #perspective · #gamedesign

In hours, I have played more of The Binding of Isaac than any other game in my Steam library. Edmund McMillen said he wasn’t expecting it to be a hit, and has since proceeded to be proven thoroughly wrong.

It is kind of a big deal among a certain crowd: as I’m writing this, the second season of the Binding of Isaac Racing League, hosted and commented by Crumps, is in full swing - even though the game was certainly not designed for that!

2020 Retrospective

Dec 31, 2020

23 min #retrospective

Against all odds, it looks like the year 2020 will actually come to an end - in less than a day now. I know! Hard to believe for me too.

A lot of things have happened for me personally, and professionally. It’s been a big year in many ways, and I feel like, to get some closure, I need to highlight some of them.

From “looking at graphs” to “driving to the hospital”

GDB scripting and Indirect functions

Feb 27, 2020

41 min #rust · #gdb · #nom

In the last article, we cleaned up our dynamic linker a little. We even implemented the Dynamic relocation.

But it’s still pretty far away from running real-world applications.

Let’s try running a simple C application with it:



// in `samples/puts.c`

#include <stdio.h>

int main() {
    puts("Hello from C");
    return 0;
}



$ cd samples/
$ gcc puts.c -o puts
$ ../target/debug/elk ./puts
Loading "/home/amos/ftl/elk/samples/puts"
Loading "/usr/lib/libc-2.32.so"
Fatal error: Could not read symbols from ELF object: Parsing error: String("Unknown SymType 10 (0xa)"):
input: 1a 00 10 00 a0 bf 0b 00 00 00 00 00 c1 00 00 00 00 00 00 00

itch.io app timeline 2016

Oct 01, 2016

2 min #itch.io

I’ve been working on the itch.io desktop app for about a year now, so I thought I’d make a quick recap:

At the time of this writing, the app has been downloaded about 460K times (including updates). Not counting the back-end, the app and its various components are made up of around 100K lines of code (mostly javascript and golang), most of which is open-source.

The builder pattern, and a macro that keeps FFI code DRY

Oct 12, 2019

12 min #networking · #icmp · #rust · #macros

Our ping API is simple, but it’s also very limited:



pub fn ping(dest: ipv4::Addr) -> Result<(), String>

// called as:
ping(ipv4::Addr([8, 8, 8, 8])).unwrap();

It doesn’t allow specifying the TTL (time to live) of packets, it doesn’t allow specifying the timeout, it doesn’t let one specify the data to send along, and it doesn’t give us any kind of information on the reply.

Printing ASCII cats to the terminal

Mar 05, 2023

20 min #rust · #reqwest

Now that our development environment is all set up, let’s make something useful!

Creating the `catscii` crate

From a VS Code window connected to our VM (as we just set up), let’s make a new Rust project:



amos@miles:~$ cargo new catscii
     Created binary (application) `catscii` package

And open it in a new VSCode window:



amos@miles:~$ code catscii

Bugs, bugs, bugs

From “looking at graphs” to “driving to the hospital”

Creating the catscii crate

Creating the `catscii` crate