improvement: look at SRV record when sending requests

src/server_server.rs

@@ -1,5 +1,5 @@
 use crate::{client_server, ConduitResult, Database, Error, PduEvent, Result, Ruma};
-use http::header::{HeaderValue, AUTHORIZATION};
+use http::header::{HeaderValue, AUTHORIZATION, HOST};
 use log::warn;
 use rocket::{get, post, put, response::content::Json, State};
 use ruma::{
@@ -23,6 +23,7 @@ use std::{
     fmt::Debug,
     time::{Duration, SystemTime},
 };
+use trust_dns_resolver::AsyncResolver;
 
 pub async fn request_well_known(
     globals: &crate::database::globals::Globals,
@@ -54,16 +55,36 @@ pub async fn send_request<T: OutgoingRequest>(
 where
     T: Debug,
 {
+    let resolver = AsyncResolver::tokio_from_system_conf()
+        .await
+        .map_err(|_| Error::BadConfig("Failed to set up trust dns resolver with system config."))?;
+
+    let mut host = None;
+
     let actual_destination = "https://".to_owned()
-        + &request_well_known(globals, &destination.as_str())
-            .await
-            .unwrap_or_else(|| {
-                let mut destination = destination.as_str().to_owned();
-                if destination.find(':').is_none() {
-                    destination += ":8448";
+        + &if let Some(mut delegated_hostname) =
+            request_well_known(globals, &destination.as_str()).await
+        {
+            if let Ok(Some(srv)) = resolver
+                .srv_lookup(format!("_matrix._tcp.{}", delegated_hostname))
+                .await
+                .map(|srv| srv.iter().next().map(|result| result.target().to_string()))
+            {
+                host = Some(delegated_hostname);
+                srv.trim_end_matches('.').to_owned()
+            } else {
+                if delegated_hostname.find(':').is_none() {
+                    delegated_hostname += ":8448";
                 }
-                destination
-            });
+                delegated_hostname
+            }
+        } else {
+            let mut destination = destination.as_str().to_owned();
+            if destination.find(':').is_none() {
+                destination += ":8448";
+            }
+            destination
+        };
 
     let mut http_request = request
         .try_into_http_request(&actual_destination, Some(""))
@@ -129,9 +150,17 @@ where
         }
     }
 
-    let reqwest_request = reqwest::Request::try_from(http_request)
+    if let Some(host) = host {
+        http_request
+            .headers_mut()
+            .insert(HOST, HeaderValue::from_str(&host).unwrap());
+    }
+
+    let mut reqwest_request = reqwest::Request::try_from(http_request)
         .expect("all http requests are valid reqwest requests");
 
+    *reqwest_request.timeout_mut() = Some(Duration::from_secs(30));
+
     let reqwest_response = globals.reqwest_client().execute(reqwest_request).await;
 
     // Because reqwest::Response -> http::Response is complicated: