Jan Schaumann

Everybody's Lost Their Minds

The AI brain worms have been spreading and I don't have a solution, I just want to get off this ride.

There is no 'printf'

In C, 'main' returns an int. What happens when you don't explicitly return a value, though? C99 provides a return value of 0, but C89... well, that's undefined, my favorite kind of behavior.

Complexities of e-mail validation logic

Nope, you don't know how to validate an email address. Even if you think you'd get the domain part right, fuggeddabout the local part. Seriously.

Time is an illusion, Unix time doubly so

Unix counts time as seconds since the epoch. Seems straight forward. What could possibly go wrong?

A few ops lessons we all learn the hard way (2020)

Ops is hard. What have learned so far?

URLs: It's Complicated

Let's play silly games with URLs...

If Programming Languages Were Futurama Characters

Map your (least) favorite programming language to your favorite Planet Express crew member based on its characteristics.

Software Engineering Laws Everybody Loves to Ignore

Sure, we all pretend to know them, but rarely do we think they apply to us. Your manager certainly doesn't...

Who reads your email?

A look at diversity of MX records across all gTLDs and the Top 1M domains, indicating where SMTP is concentrated and what organizations might have broad access to the world's emails.

DNS Security: Threat Modeling DNSSEC, DoT, and DoH

There's been a lot of talk about DNS-over-HTTPS aka DoH lately, primarily due to Mozilla's and Google's respective plans to move forward with enabling it in their browsers. There's also a lot of misunderstanding and conflation of speculated plans for world domination with practical benefits of the technology; it…

AI errno(2) values

errno(2) values for the AI age

Whois: Fragile, Unparseable, Obsolete

A rather unstructured look at one of the older and infuriatingly trivial internet protocols: WHOIS

Infosec Core Competencies

An incomplete list of (technical) things just about anybody working in Information Security would benefit from knowing.

(All) DNS Resource Records

Just how many weird Resource Records can you stuff into a zone file? And what do these weird RRs actually return?

Basic Network Troubleshooting

A quick explanation of the differences between network failures most commonly observed in day to day operatoins. And no, it's not (always) DNS.

The Art of Plain Text (2015)

What’s the maximum size of a DNS response?

Everybody knows a DNS response needs to fit into a 512 byte UDP packet, right? But suppose it doesn't fit...