NAS: Run HTTP header filters in a detached goroutine

nas/listener.go

@@ -29,9 +29,16 @@ func (l *nasListener) Accept() (net.Conn, error) {
 		return nil, err
 	}
 
+	pr, pw := io.Pipe()
+	go func() {
+		r := bufio.NewReader(conn)
+		filterDuplicateHost(r, pw)
+		_, err := io.Copy(pw, r)
+		_ = pw.CloseWithError(err)
+	}()
 	return &nasConn{
 		Conn:   conn,
-		reader: filterDuplicateHost(conn),
+		reader: pr,
 	}, nil
 }
 
@@ -41,17 +48,17 @@ func (c *nasConn) Read(b []byte) (int, error) {
 
 // filterDuplicateHost wraps a net.Conn and filters out duplicate Host headers from the HTTP request,
 // making the invalid requests sent by DWC acceptable to the standard library's HTTP server.
-func filterDuplicateHost(c net.Conn) io.Reader {
-	r := bufio.NewReader(c)
-
+func filterDuplicateHost(r *bufio.Reader, p *io.PipeWriter) {
 	// Read the first line of the HTTP request
 	line, err := r.ReadString('\n')
 	if err != nil {
-		return io.MultiReader(strings.NewReader(line), r)
+		_, _ = p.Write([]byte(line))
+		return
 	}
 	// Is this an HTTP request?
 	if !strings.HasSuffix(line, "HTTP/1.1\r\n") {
-		return io.MultiReader(strings.NewReader(line), r)
+		_, _ = p.Write([]byte(line))
+		return
 	}
 
 	// Iterate through the HTTP headers and remove any duplicate Host headers
@@ -72,7 +79,7 @@ func filterDuplicateHost(c net.Conn) io.Reader {
 		headers.WriteString(headerLine)
 	}
 
-	return io.MultiReader(strings.NewReader(line+headers.String()), r)
+	_, _ = p.Write([]byte(line + headers.String()))
 }
 
 func listenAndServe(address string) {