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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:

Why is my Rust build so slow?

Dec 30, 2021

36 min #rust · #release-engineering

I’ve recently come back to an older project of mine (that powers this website), and as I did some maintenance work: upgrade to newer crates, upgrade to a newer rustc, I noticed that my build was taking too damn long!

For me, this is a big issue. Because I juggle a lot of things at any given time, and I have less and less time to just hyperfocus on an issue, I try to make my setup as productive as possible.

Veronica Mars and NTLM password hashes

Oct 28, 2020

30 min #tv

When I started my Patreon, I had no idea if it would work at all. The whole thing seemed like a gamble: spend an inordinate amount of time writing quality articles, and hope that folks will like it enough to kick in 5, 10, or 50 bucks a month just to see more of them.

I’m happy to say the gamble paid off - literally. Take that, impostor syndrome!

Highlighted code in slides

Nov 23, 2024

15 min #html · #css · #javascript · #color

I have obsessed about this long enough, I think it’s only fair I (and you!) get some content out of it.

When I started writing this article, I was working on my P99 CONF slides. Those slides happen to include some bits of code. And because I’m a perfectionist, I would like this code to be syntax highlighted, like this:

let addr: SocketAddr = config.address.parse()?;
let ln = TcpListener::bind(&addr).await?;
info!("🦊 {}", config.base_url);

Day 11 (Advent of Code 2022)

Dec 12, 2022

8 min #rust · #advent-of-code · #nom

It’s a new day, it’s a new advent of code puzzle.

In that one, we have to apparently cosplay as an IBM mainframe and just.. crunch them numbers. This doesn’t look fun, and I can’t think of a clever twist to make it fun, so let’s try to make it short and sweet.

Parsing

Our input looks like this:

Monkey 0:
  Starting items: 79, 98
  Operation: new = old * 19
  Test: divisible by 23
    If true: throw to monkey 2
    If false: throw to monkey 3

Monkey 1:
  Starting items: 54, 65, 75, 74
  Operation: new = old + 6
  Test: divisible by 19
    If true: throw to monkey 2
    If false: throw to monkey 0

(etc)

Day 8 (Advent of Code 2020)

Dec 22, 2020

6 min #rust · #advent-of-code

Time for another Advent of Code 2020 problem!

That one sounds like it’s going to be fun. Our input is pretty much assembly, like this:

nop +0
acc +1
jmp +4
acc +3
jmp -3
acc -99
acc +1
jmp -4
acc +6

So, the first thing we’re going to do is write down some types.

There’s more than one way to approach this problem, but let’s go with this:

#[derive(Debug, Clone, Copy)]
enum InstructionKind {
    Nop,
    Acc,
    Jmp,
}

#[derive(Debug, Clone, Copy)]
struct Instruction {
    kind: InstructionKind,
    operand: isize,
}

type Program = Vec<Instruction>;

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

A terminal case of Linux

Sep 24, 2021

29 min #rust · #linux

Has this ever happened to you?

You want to look at a JSON file in your terminal, so you pipe it into jq so you can look at it with colors and stuff.

Cool Bear's hot tip

That’s a useless use of cat.

…oh hey cool bear. No warm-up today huh.

Sure, fine, okay, I’ll read the darn man page for jq… okay it takes a “filter” and then some files. And the filter we want is.. . which, just like files, means “the current thing”:

Intro

Parsing