access log: add header based filter (#616)

define a access log filter to filter requests based on the
value of a specified header.

This is the initial data plane api change for the issue envoyproxy/envoy#2544.

Signed-off-by: Kevin Chan <kchan@evernote.com>

envoy/config/filter/accesslog/v2/BUILD

@@ -15,6 +15,7 @@ api_proto_library(
         "//envoy/api/v2/core:address",
         "//envoy/api/v2/core:base",
         "//envoy/api/v2/core:grpc_service",
+        "//envoy/api/v2/route",
         "//envoy/type:percent",
     ],
 )
@@ -26,6 +27,7 @@ api_go_proto_library(
         "//envoy/api/v2/core:address_go_proto",
         "//envoy/api/v2/core:base_go_proto",
         "//envoy/api/v2/core:grpc_service_go_proto",
+        "//envoy/api/v2/route:route_go_proto",
         "//envoy/type:percent_go_proto",
     ],
 )

envoy/config/filter/accesslog/v2/accesslog.proto

@@ -5,6 +5,7 @@ option go_package = "v2";
 
 import "envoy/api/v2/core/address.proto";
 import "envoy/api/v2/core/base.proto";
+import "envoy/api/v2/route/route.proto";
 import "envoy/type/percent.proto";
 
 import "google/protobuf/duration.proto";
@@ -331,6 +332,9 @@ message AccessLogFilter {
 
     // Or filter.
     OrFilter or_filter = 7;
+
+    // [#not-implemented-hide:] Header filter.
+    HeaderFilter header_filter = 8;
   }
 }
 
@@ -414,6 +418,13 @@ message OrFilter {
   repeated AccessLogFilter filters = 2 [(validate.rules).repeated .min_items = 2];
 }
 
+// [#not-implemented-hide:] Filters requests based on the presence or value of a request header.
+message HeaderFilter {
+  // Only requests with a header which matches the specified HeaderMatcher will pass the filter
+  // check.
+  envoy.api.v2.route.HeaderMatcher header = 1 [(validate.rules).message.required = true];
+}
+
 // Custom configuration for an AccessLog that writes log entries directly to a file.
 // Configures the built-in *envoy.file_access_log* AccessLog.
 message FileAccessLog {