xds: Required Router Filter for both Client and Server side

xds/internal/httpfilter/fault/fault.go

@@ -101,6 +101,10 @@ func (builder) ParseFilterConfigOverride(override proto.Message) (httpfilter.Fil
 	return parseConfig(override)
 }
 
+func (builder) IsTerminal() bool {
+	return false
+}
+
 var _ httpfilter.ClientInterceptorBuilder = builder{}
 
 func (builder) BuildClientInterceptor(cfg, override httpfilter.FilterConfig) (iresolver.ClientInterceptor, error) {

xds/internal/httpfilter/httpfilter.go

@@ -50,6 +50,9 @@ type Filter interface {
 	// not accept a custom type.  The resulting FilterConfig will later be
 	// passed to Build.
 	ParseFilterConfigOverride(proto.Message) (FilterConfig, error)
+	// IsTerminal returns whether this Filter is terminal or not (i.e. it must
+	// be last filter in the filter chain).
+	IsTerminal() bool
 }
 
 // ClientInterceptorBuilder constructs a Client Interceptor.  If this type is

xds/internal/httpfilter/router/router.go

@@ -73,6 +73,10 @@ func (builder) ParseFilterConfigOverride(override proto.Message) (httpfilter.Fil
 	return config{}, nil
 }
 
+func (builder) IsTerminal() bool {
+	return true
+}
+
 var (
 	_ httpfilter.ClientInterceptorBuilder = builder{}
 	_ httpfilter.ServerInterceptorBuilder = builder{}

xds/internal/server/listener_wrapper_test.go

@@ -34,6 +34,8 @@ import (
 	wrapperspb "github.com/golang/protobuf/ptypes/wrappers"
 	"google.golang.org/grpc/internal/grpctest"
 	"google.golang.org/grpc/internal/testutils"
+	_ "google.golang.org/grpc/xds/internal/httpfilter/router"
+	"google.golang.org/grpc/xds/internal/testutils/e2e"
 	"google.golang.org/grpc/xds/internal/testutils/fakeclient"
 	"google.golang.org/grpc/xds/internal/xdsclient"
 )
@@ -82,6 +84,7 @@ var listenerWithRouteConfiguration = &v3listenerpb.Listener{
 									RouteConfigName: "route-1",
 								},
 							},
+							HttpFilters: []*v3httppb.HttpFilter{e2e.RouterHTTPFilter},
 						}),
 					},
 				},
@@ -143,6 +146,7 @@ var listenerWithFilterChains = &v3listenerpb.Listener{
 											Action: &v3routepb.Route_NonForwardingAction{},
 										}}}}},
 							},
+							HttpFilters: []*v3httppb.HttpFilter{e2e.RouterHTTPFilter},
 						}),
 					},
 				},

xds/internal/testutils/e2e/clientresources.go

@@ -97,6 +97,9 @@ func DefaultClientResources(params ResourceParams) UpdateOptions {
 	}
 }
 
+// RouterHTTPFilter is the HTTP Filter configuration for the Router filter.
+var RouterHTTPFilter = HTTPFilter("router", &v3routerpb.Router{})
+
 // DefaultClientListener returns a basic xds Listener resource to be used on
 // the client side.
 func DefaultClientListener(target, routeName string) *v3listenerpb.Listener {
@@ -212,6 +215,7 @@ func DefaultServerListener(host string, port uint32, secLevel SecurityLevel) *v3
 												Action: &v3routepb.Route_NonForwardingAction{},
 											}}}}},
 								},
+								HttpFilters: []*v3httppb.HttpFilter{RouterHTTPFilter},
 							}),
 						},
 					},
@@ -256,6 +260,7 @@ func DefaultServerListener(host string, port uint32, secLevel SecurityLevel) *v3
 												Action: &v3routepb.Route_NonForwardingAction{},
 											}}}}},
 								},
+								HttpFilters: []*v3httppb.HttpFilter{RouterHTTPFilter},
 							}),
 						},
 					},

xds/internal/xdsclient/filter_chain.go

@@ -505,7 +505,7 @@ func processNetworkFilters(filters []*v3listenerpb.Filter) (*FilterChain, error)
 			// HTTPConnectionManager must have valid http_filters." - A36
 			filters, err := processHTTPFilters(hcm.GetHttpFilters(), true)
 			if err != nil {
-				return nil, fmt.Errorf("network filters {%+v} had invalid server side HTTP Filters {%+v}", filters, hcm.GetHttpFilters())
+				return nil, fmt.Errorf("network filters {%+v} had invalid server side HTTP Filters {%+v}: %v", filters, hcm.GetHttpFilters(), err)
 			}
 			if !seenHCM {
 				// TODO: Implement terminal filter logic, as per A36.