VHost/Route-local filter configurations (#605)

This patch begins addressing #540, adding per_filter_config fields to both VirtualHost. ClusterWeight and Route configs. A following PR will, as an initial PoC/example, implement vhost/route specific configs for the HTTP buffer filter.

Signed-off-by: Chris Roche <croche@lyft.com>

envoy/api/v2/route/route.proto

@@ -9,6 +9,7 @@ import "envoy/api/v2/auth/auth.proto";
 import "envoy/type/range.proto";
 
 import "google/protobuf/duration.proto";
+import "google/protobuf/struct.proto";
 import "google/protobuf/wrappers.proto";
 
 import "validate/validate.proto";
@@ -99,6 +100,13 @@ message VirtualHost {
   // [#not-implemented-hide:]
   // Return a 401/403 when auth checks fail.
   auth.AuthAction auth = 9;
+
+  // The per_filter_config field can be used to provide virtual host-specific
+  // configurations for filters. The key should match the filter name, such as
+  // *envoy.buffer* for the HTTP buffer filter. Use of this field is filter
+  // specific; see the :ref:`HTTP filter documentation <config_http_filters>`
+  // for if and how it is utilized.
+  map<string, google.protobuf.Struct> per_filter_config = 12;
 }
 
 // A route is both a specification of how to match a request as well as an indication of what to do
@@ -138,6 +146,13 @@ message Route {
   // [#not-implemented-hide:]
   // Return a 401/403 when auth checks fail.
   auth.AuthAction auth = 6;
+
+  // The per_filter_config field can be used to provide route-specific
+  // configurations for filters. The key should match the filter name, such as
+  // *envoy.buffer* for the HTTP buffer filter. Use of this field is filter
+  // specific; see the :ref:`HTTP filter documentation <config_http_filters>` for
+  // if and how it is utilized.
+  map<string, google.protobuf.Struct> per_filter_config = 8;
 }
 
 // Compared to the :ref:`cluster <envoy_api_field_route.RouteAction.cluster>` field that specifies a
@@ -197,6 +212,13 @@ message WeightedCluster {
     // :ref:`cluster_metadata <envoy_api_field_route.RouteAction.cluster_metadata>` from the
     // enclosing :ref:`envoy_api_msg_route.RouteAction`.
     core.Metadata cluster_metadata = 7;
+
+    // The per_filter_config field can be used to provide weighted cluster-specific
+    // configurations for filters. The key should match the filter name, such as
+    // *envoy.buffer* for the HTTP buffer filter. Use of this field is filter
+    // specific; see the :ref:`HTTP filter documentation <config_http_filters>`
+    // for if and how it is utilized.
+    map<string, google.protobuf.Struct> per_filter_config = 8;
   }
 
   // Specifies one or more upstream clusters associated with the route.