[Bandwidth-Limit] Fix bandwidth delay calculation logic (#24024)

* Fix bandwidth delay calculation logic

Signed-off-by: Zhiyong Yang <gayang@miccrosoft.com>

Mirrored from https://github.com/envoyproxy/envoy @ 230a1780c62299b0bce0b99f8a76c90ca4207855

envoy/extensions/filters/http/bandwidth_limit/v3/bandwidth_limit.proto

@@ -72,11 +72,13 @@ message BandwidthLimit {
   //
   // .. note::
   //
-  //   * If set true, the response trailers ``bandwidth-request-delay-ms`` and ``bandwidth-response-delay-ms`` will be added, prefixed by ``response_trailer_prefix``.
-  //   * bandwidth-request-delay-ms: delay time in milliseconds it took for the request stream transfer.
-  //   * bandwidth-response-delay-ms: delay time in milliseconds it took for the response stream transfer.
-  //   * If :ref:`enable_mode <envoy_v3_api_field_extensions.filters.http.bandwidth_limit.v3.BandwidthLimit.enable_mode>` is ``DISABLED`` or ``REQUEST``, the trailers will not be set.
-  //   * If both the request and response delay time is 0, the trailers will not be set.
+  //   If set true, the following 4 trailers will be added, prefixed by ``response_trailer_prefix``:
+  //   * bandwidth-request-delay-ms: delay time in milliseconds it took for the request stream transfer including request body transfer time and the time added by the filter.
+  //   * bandwidth-response-delay-ms: delay time in milliseconds it took for the response stream transfer including response body transfer time and the time added by the filter.
+  //   * bandwidth-request-filter-delay-ms: delay time in milliseconds in request stream transfer added by the filter.
+  //   * bandwidth-response-filter-delay-ms: delay time in milliseconds that added by the filter.
+  //   If :ref:`enable_mode <envoy_v3_api_field_extensions.filters.http.bandwidth_limit.v3.BandwidthLimit.enable_mode>` is ``DISABLED`` or ``REQUEST``, the trailers will not be set.
+  //   If both the request and response delay time is 0, the trailers will not be set.
   //
   bool enable_response_trailers = 6;