fix: send http requests in origin not absolute form

Absolute form is meant for proxies and for example
nginx rejects it with 400 if the host contains an underscore, breaking autoconfig discovery.

src/net/http.rs

@@ -258,6 +258,15 @@ pub(crate) async fn http_cache_cleanup(context: &Context) -> Result<()> {
     Ok(())
 }
 
+/// Returns the request target in origin form, i.e. the path and query of `url`.
+///
+/// The absolute form is only for proxy requests and
+/// nginx rejects it if the host starts contains an underscore.
+fn origin_form(url: &hyper::Uri) -> &str {
+    url.path_and_query()
+        .map_or("/", |path_and_query| path_and_query.as_str())
+}
+
 /// Fetches URL and updates the cache.
 ///
 /// URL is fetched regardless of whether there is an existing result in the cache.
@@ -276,7 +285,7 @@ async fn fetch_url(context: &Context, original_url: &str, strict_tls: bool) -> R
             .context("URL has no authority")?
             .clone();
 
-        let req = hyper::Request::builder().uri(parsed_url);
+        let req = hyper::Request::builder().uri(origin_form(&parsed_url));
 
         // OSM usage policy requires
         // that User-Agent is set for HTTP GET requests
@@ -409,7 +418,7 @@ pub(crate) async fn post_empty(context: &Context, url: &str) -> Result<(String,
         .authority()
         .context("URL has no authority")?
         .clone();
-    let req = hyper::Request::post(parsed_url)
+    let req = hyper::Request::post(origin_form(&parsed_url))
         .header(hyper::header::HOST, authority.as_str())
         .body(http_body_util::Empty::<Bytes>::new())?;
 
@@ -432,6 +441,20 @@ mod tests {
     use crate::test_utils::TestContext;
     use crate::tools::SystemTime;
 
+    #[test]
+    fn test_origin_form() {
+        let url = "https://_cm0.localchat/autoconfig?emailaddress=x%40_cm0.localchat"
+            .parse()
+            .unwrap();
+        assert_eq!(
+            origin_form(&url),
+            "/autoconfig?emailaddress=x%40_cm0.localchat"
+        );
+
+        let url = "https://example.org".parse().unwrap();
+        assert_eq!(origin_form(&url), "/");
+    }
+
     #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
     async fn test_http_cache() -> Result<()> {
         let t = &TestContext::new().await;