In an earlier thread I was claiming that http://ai/ was no longer operating, but I belatedly learned that this is because systemd's DNS resolver has hard-coded a refusal to look up addresses with a single label from servers outside the LAN. I misinterpreted the lack of results as implying that it had been removed upstream.
So, (1) there is another site that is as short as the one you mentioned, and (2) Linux systems that default to using systemd-resolve won't be able to see either of them!
Nope! I specifically tried that in the course of researching my post for the other thread, and again now. This doesn't work either on the browser or command line, including using DNS-specific software like dig or host. I think I found a spot in the systemd source code where it specifically says it will refuse to attempt single-label lookups to remote nameservers, and all my Linux systems are relying on systemd-resolve for all of their DNS lookups.
If I specifically change my nameserver away from 127.0.0.53 for a query and point it anywhere else, these single-label names immediately resolve correctly again.
I was also speculating in the other thread that it might be hard to get systemd to reverse this decision just for the one host "ai". Even though we now have twice as many examples of hosts that are broken by this, I still think it might be hard to get it fixed!
I also couldn't see ai, but my nameserver was set to my wifi router. I guess either my wifi router is using systemd-resolve or this practice isn't just done by systemd.
If you're using systemd-resolve either on your own system or on the Pi, single-label DNS lookups won't be propagated. (You can see that you're using this if your upstream resolver is set to 127.0.0.53 anywhere.)
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So, (1) there is another site that is as short as the one you mentioned, and (2) Linux systems that default to using systemd-resolve won't be able to see either of them!
If I specifically change my nameserver away from 127.0.0.53 for a query and point it anywhere else, these single-label names immediately resolve correctly again.
I was also speculating in the other thread that it might be hard to get systemd to reverse this decision just for the one host "ai". Even though we now have twice as many examples of hosts that are broken by this, I still think it might be hard to get it fixed!
> It works!
> This is the default web page for this server.
> The web server software is running but no content has been added, yet.
Also reminds me on this interesting collection of unusual urls (and regular expressions) https://mathiasbynens.be/demo/url-regex