`Host` header extraction not working

[phlax]

I think this is a bug in axum-server

i have been writing an echo server in axum, and use axum-server for https

im extracting the headers with HeaderMap

when i make an https query - the Host header is missing

$ curl -vk https://localhost:2323
* Host localhost:2323 was resolved.
... snip ...
* ALPN: server accepted h2
* Connected to localhost (127.0.0.1) port 2323
* using HTTP/2
* [HTTP/2] [1] OPENED stream for https://localhost:2323/
* [HTTP/2] [1] [:method: GET]
* [HTTP/2] [1] [:scheme: https]
* [HTTP/2] [1] [:authority: localhost:2323]
* [HTTP/2] [1] [:path: /]
* [HTTP/2] [1] [user-agent: curl/8.12.1]
* [HTTP/2] [1] [accept: */*]
> GET / HTTP/2
> Host: localhost:2323
> User-Agent: curl/8.12.1
> Accept: */*
>
* Request completely sent off
< HTTP/2 200
< content-type: application/json
< content-length: 167
< date: Tue, 18 Mar 2025 15:20:09 GMT
<
{
  "hostname": "echo",
  "method": "GET",
  "headers": {
    "user-agent": "curl/8.12.1",
    "accept": "*/*"
  },
  "query_params": {},
  "body": "",
  "path": ""
}

querying for http 1 or 2 the host is extracted as expected

$ curl -v http://localhost:8787
* Host localhost:8787 was resolved.
* IPv6: ::1
* IPv4: 127.0.0.1
*   Trying [::1]:8787...
* Connected to localhost (::1) port 8787
* using HTTP/1.x
> GET / HTTP/1.1
> Host: localhost:8787
> User-Agent: curl/8.12.1
> Accept: */*
>
* Request completely sent off
< HTTP/1.1 200 OK
< content-type: application/json
< content-length: 197
< date: Tue, 18 Mar 2025 15:24:15 GMT
<
{
  "hostname": "echo",
  "method": "GET",
  "headers": {
    "host": "localhost:8787",
    "user-agent": "curl/8.12.1",
    "accept": "*/*"
  },
  "query_params": {},
  "body": "",
  "path": ""
}

[GrantGryczan]

This is not a bug. The Host header is superseded by the :authority pseudo-header as of HTTP/2. And for whatever reason, curl displays the Host header for HTTP/2 even though it isn't actually sent.

If you want to get the URI authority from your request, you should do something like this:

use axum::http::header::HOST;

// The `:authority` pseudo-header must take priority over the `Host` header as per RFC 9113 (section
// 8.3.1).
let authority = match request.uri().authority() {
    Some(authority) => Some(authority.as_str()),
    None => request
        .headers()
        .get(HOST)
        .and_then(|host| host.to_str().ok()),
};