fix(rustproxy-http): prevent HTTP/3 response body streaming from hanging on backend completion

rust/crates/rustproxy-http/src/h3_service.rs

@@ -259,6 +259,12 @@ async fn handle_h3_request(
         h3_response = h3_response.header(name, value);
     }
 
+    // Extract content-length for body loop termination (must be before into_body())
+    let content_length: Option<u64> = response.headers()
+        .get(hyper::header::CONTENT_LENGTH)
+        .and_then(|v| v.to_str().ok())
+        .and_then(|s| s.parse().ok());
+
     // Add Alt-Svc for HTTP/3 advertisement
     let alt_svc = route.action.udp.as_ref()
         .and_then(|u| u.quic.as_ref())
@@ -279,21 +285,52 @@ async fn handle_h3_request(
 
     // Stream response body back
     use http_body_util::BodyExt;
+    use http_body::Body as _;
     let mut body = response.into_body();
     let mut total_bytes_out: u64 = 0;
-    while let Some(frame) = body.frame().await {
-        match frame {
-            Ok(frame) => {
+
+    // Per-frame idle timeout: if no frame arrives within this duration, assume
+    // the body is complete (or the backend has stalled). This prevents indefinite
+    // hangs on close-delimited bodies or when hyper's internal trailers oneshot
+    // never resolves after all data has been received.
+    const FRAME_IDLE_TIMEOUT: Duration = Duration::from_secs(30);
+
+    loop {
+        // Layer 1: If the body already knows it is finished (Content-Length
+        // bodies track remaining bytes internally), break immediately to
+        // avoid blocking on hyper's internal trailers oneshot.
+        if body.is_end_stream() {
+            break;
+        }
+
+        // Layer 3: Per-frame idle timeout safety net
+        match tokio::time::timeout(FRAME_IDLE_TIMEOUT, body.frame()).await {
+            Ok(Some(Ok(frame))) => {
                 if let Some(data) = frame.data_ref() {
                     total_bytes_out += data.len() as u64;
                     stream.send_data(Bytes::copy_from_slice(data)).await
                         .map_err(|e| anyhow::anyhow!("Failed to send H3 data: {}", e))?;
+
+                    // Layer 2: Content-Length byte count check
+                    if let Some(cl) = content_length {
+                        if total_bytes_out >= cl {
+                            break;
+                        }
+                    }
                 }
             }
-            Err(e) => {
+            Ok(Some(Err(e))) => {
                 warn!("Backend body read error: {}", e);
                 break;
             }
+            Ok(None) => break, // Body ended naturally
+            Err(_) => {
+                debug!(
+                    "H3 body frame idle timeout ({:?}) after {} bytes; finishing stream",
+                    FRAME_IDLE_TIMEOUT, total_bytes_out
+                );
+                break;
+            }
         }
     }