Mastodawn

Lukas Jul 18, 2025

Mildly cursed factoid about UNC paths:

- UNC Paths can contain IP addresses such as \\192.168.1.1\share
- IPv6 addresses are supported as well
- IPv6 addresses contain colons
- can't have colons in Windows paths since colons are reserved for drive letters

So Microsoft came up with the the ipv6-literal.net domain that's special-cased by Windows so you can to write IPv6 addresses in UNC paths as 2a0e-3c0--21.ipv6-literal.net without it hitting any resolvers.

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radentscheiderin :ferris:

@karotte TIL why colons are forbidden in Windows paths! I was confused when a colleague of mine using Windows wasn't able to open a file with a timestamp in the name that I sent them

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Jernej Simončič �Jul 18, 2025

@pmmeurcatpics @karotte It's worse than that – : is used as stream separator on NTFS, so foo:bar refers to a named stream bar in file (or directory) named foo.

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Klaus Frank Jul 18, 2025

@jernej__s @pmmeurcatpics @karotte

It's even worse than that, a few years (oh or was it almost 10 by now?) where the spooler service was able to write raw filenames to disk that bypassed all of the usual validations and you could end up with such files on disk. And you probably can imagine what trying to access such a file could have caused. I think there wasn't a way to get rid of these names except for reformatting C or Hexeditor edits of the filesystem...