http: Introduce preserve_upstream_date option (#11077)

The preserve_upstream_date option allows the HTTP Connection Manager to be configured to pass through the original date header from the upstream response rather than overwriting it. The default behaviour for the date response header remains the same as before -- the header value will be overwritten by Envoy.

Signed-off-by: Craig Radcliffe <craig.radcliffe@broadcom.com>

Mirrored from https://github.com/envoyproxy/envoy @ 10c755e9d9b8acd7cf1702a4f49dbcbdf0696198

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

@@ -30,7 +30,7 @@ option (udpa.annotations.file_status).package_version_status = ACTIVE;
 // HTTP connection manager :ref:`configuration overview <config_http_conn_man>`.
 // [#extension: envoy.filters.network.http_connection_manager]
 
-// [#next-free-field: 38]
+// [#next-free-field: 39]
 message HttpConnectionManager {
   option (udpa.annotations.versioning).previous_message_type =
       "envoy.config.filter.network.http_connection_manager.v2.HttpConnectionManager";
@@ -506,6 +506,11 @@ message HttpConnectionManager {
   //
   // 3. Tracing decision (sampled, forced, etc) is set in 14th byte of the UUID.
   RequestIDExtension request_id_extension = 36;
+
+  // If `preserve_upstream_date` is true, the value of the `date` header sent by the upstream
+  // host will not be overwritten by the HTTP Connection Manager. The default behaviour is
+  // to overwrite the `date` header unconditionally.
+  bool preserve_upstream_date = 38;
 }
 
 message Rds {

envoy/extensions/filters/network/http_connection_manager/v4alpha/http_connection_manager.proto

@@ -30,7 +30,7 @@ option (udpa.annotations.file_status).package_version_status = NEXT_MAJOR_VERSIO
 // HTTP connection manager :ref:`configuration overview <config_http_conn_man>`.
 // [#extension: envoy.filters.network.http_connection_manager]
 
-// [#next-free-field: 38]
+// [#next-free-field: 39]
 message HttpConnectionManager {
   option (udpa.annotations.versioning).previous_message_type =
       "envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager";
@@ -506,6 +506,11 @@ message HttpConnectionManager {
   //
   // 3. Tracing decision (sampled, forced, etc) is set in 14th byte of the UUID.
   RequestIDExtension request_id_extension = 36;
+
+  // If `preserve_upstream_date` is true, the value of the `date` header sent by the upstream
+  // host will not be overwritten by the HTTP Connection Manager. The default behaviour is
+  // to overwrite the `date` header unconditionally.
+  bool preserve_upstream_date = 38;
 }
 
 message Rds {