TCP Tunneling: Optionally propagate response trailers to downstream info (#25023)

* TCP Tunneling: Optionally propagate response trailers to downstream info

Signed-off-by: IssaAbuKalbein <isaqalbein@gmail.com>

Mirrored from https://github.com/envoyproxy/envoy @ b12e777be479d7ceeb1abece48352d20557b34b1

envoy/extensions/filters/network/tcp_proxy/v3/tcp_proxy.proto

@@ -64,7 +64,7 @@ message TcpProxy {
   // Configuration for tunneling TCP over other transports or application layers.
   // Tunneling is supported over both HTTP/1.1 and HTTP/2. Upstream protocol is
   // determined by the cluster configuration.
-  // [#next-free-field: 6]
+  // [#next-free-field: 7]
   message TunnelingConfig {
     option (udpa.annotations.versioning).previous_message_type =
         "envoy.config.filter.network.tcp_proxy.v2.TcpProxy.TunnelingConfig";
@@ -109,6 +109,10 @@ message TcpProxy {
     // :ref:`use_post field <envoy_v3_api_field_extensions.filters.network.tcp_proxy.v3.TcpProxy.TunnelingConfig.use_post>`
     // isn't true, it will be rejected.
     string post_path = 5;
+
+    // Save the response trailers to the downstream info filter state for consumption
+    // by the network filters. The filter state key is ``envoy.tcp_proxy.propagate_response_trailers``.
+    bool propagate_response_trailers = 6;
   }
 
   message OnDemand {