95 lines
5 KiB
Markdown
95 lines
5 KiB
Markdown
# 300
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No, not the movie. I'm a nerd who's spent half their day so far configuring nginx, it should be obvious at this point.
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---
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Since I have my code 1) [on my Gitea (now Forgejo) instance](https://git.askiiart.net/askiiart/askiiart-net), and 2) [mirrored](https://github.com/askiiart/askiiart.github.io) on GitHub, I didn't just want to set up a simple [308 Permanent Redirect](https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/308) from [/.git](/.git) to my code in one place. I wanted users to be able to see both options, both Gitea and GitHub, and apparently there's actually a thing for that already, I can just use that!
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## ok but how?
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300 seems great, but there's no standardized way to use it. The number, and the `Location` header as the preferred choice is all that's actually standardized. Straight from [RFC 9110](https://httpwg.org/specs/rfc9110.html#status.300):
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> If the server has a preferred choice, the server *SHOULD* generate a Location header field containing a preferred choice's URI reference. The user agent MAY use the Location field value for automatic redirection.
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>
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> For request methods other than HEAD, the server *SHOULD* generate content in the 300 response containing a list of representation metadata and URI reference(s) from which the user or user agent can choose the one most preferred.
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Does this mean to return some HTML? A JSON dict? YAML? An image of a pickle with that info overlaid on top of it!? *Nobody knows!* And from the Mozilla docs:
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> As there is no standardized way of choosing one of the responses, this response code is very rarely used.
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Very helpful.
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## ok but actually how?
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After a bit of Googling, I found [this Stack Overflow thread](https://stackoverflow.com/questions/8905545/what-is-the-exact-response-structure-for-http-status-code-300-multiple-choices), which just says this<sup>[<a href="#browser-specific-info">note</a>]</sup>:
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> The "multiple choices" are done by sending the links in hypertext (HTML) content and let the *user* pick.
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Well, that's boring. Guess I'll do that then.
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```language-nginx
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location /.git {
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add_header Location "https://git.askiiart.net/askiiart/askiiart-net";
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return 300 '<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"></head><body><a href="https://git.askiiart.net/askiiart/askiiart-net">Self-hosted</a><br><a href="https://github.com/askiiart/askiiart.github.io">GitHub</a></body></html>';
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}
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```
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## nginx is hard
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That config looks fine, right? It just sets the `Location` header and returns this basic menu to pick from. But it won't open in any browsers, Firefox displays nothing, and has `NS_ERROR_WONT_HANDLE_CONTENT` in the developer tools, and Chrome shows a `ERR_INVALID_RESPONSE` error. Running `curl -I https://askiiart.net`, and...
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```sh
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HTTP/1.1 300
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Server: nginx/1.25.3
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Date: Wed, 06 Dec 2023 16:36:01 GMT
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Content-Type: application/octet-stream
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Content-Length: 223
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Connection: keep-alive
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```
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There's no Location header there! And the browsers are probably refusing to show it because of the wrong `Content-Type` – and no, adding a header with `add_header` doesn't work for that one, either.
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Turns out in order to be able to use `add_header`, you first need to set `default_type` (which sets a default `Content-Type`). I could've set that in the `location /.git` block, but I just decided to make it global.
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So here's the fixed config:
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```language-nginx
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# actually much higher in file
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default_type "text/html";
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location /.git {
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add_header Location "https://git.askiiart.net/askiiart/askiiart-net";
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return 300 '<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"></head><body><a href="https://git.askiiart.net/askiiart/askiiart-net">Self-hosted</a><br><a href="https://github.com/askiiart/askiiart-net">GitHub</a></body></html>';
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}
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```
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Yep, that works! I had set up my IP address pages the same way, so let's fix that:
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```language-nginx
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location /ip {
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default_type text/plain;
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return 200 "$remote_addr";
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}
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location /ip/json {
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default_type application/json;
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return 200 '{"ip":"$remote_addr"}';
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}
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```
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These still don't work, they just return my reverse proxy container's gateway's address, but that's for another time.
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## Open your eyes... wake up, *Link*
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Turns out might be a standard way to do it! From [RFC 9110](https://httpwg.org/specs/rfc9110.html#status.300), again:
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> It is possible to communicate the list using a set of Link header fields [RFC5988](https://httpwg.org/specs/rfc9110.html#RFC8288), each with a relationship of "alternate", though deployment is a chicken-and-egg problem.
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I'll probably figure out the `Link` header some other time and will add this later, at which point I'll post an addendum. Until then, bye I guess!
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## Footnotes and stuff
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#### browser-specific info
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Elsewhere in the Quora thread it says, in short, that Firefox and Chrome just displays the HTML, and Safari will follow the `Location` header. Edit: Apparently I forgot to link the Quora thread, so I've got no idea what I'm referencing here. Sorry! \[[Back](#ok-but-actually-how)\]
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