NET-5531 Translate response header modifier(s) from HTTPRoute onto Consul config entry

.changelog/2904.txt

@@ -0,0 +1,3 @@
+```release-note:feature
+api-gateway: Add support for response header modifiers in HTTPRoute filters
+```

control-plane/api-gateway/common/diff.go

@@ -148,6 +148,7 @@ func (e entryComparator) httpRoutesEqual(a, b api.HTTPRouteConfigEntry) bool {
 func (e entryComparator) httpRouteRulesEqual(a, b api.HTTPRouteRule) bool {
 	return slices.EqualFunc(a.Filters.Headers, b.Filters.Headers, e.httpHeaderFiltersEqual) &&
 		bothNilOrEqualFunc(a.Filters.URLRewrite, b.Filters.URLRewrite, e.urlRewritesEqual) &&
+		slices.EqualFunc(a.ResponseFilters.Headers, b.ResponseFilters.Headers, e.httpHeaderFiltersEqual) &&
 		slices.EqualFunc(a.Matches, b.Matches, e.httpMatchesEqual) &&
 		slices.EqualFunc(a.Services, b.Services, e.httpServicesEqual) &&
 		bothNilOrEqualFunc(a.Filters.RetryFilter, b.Filters.RetryFilter, e.retryFiltersEqual) &&
@@ -160,7 +161,8 @@ func (e entryComparator) httpServicesEqual(a, b api.HTTPService) bool {
 		orDefault(a.Namespace, e.namespaceA) == orDefault(b.Namespace, e.namespaceB) &&
 		orDefault(a.Partition, e.partitionA) == orDefault(b.Partition, e.partitionB) &&
 		slices.EqualFunc(a.Filters.Headers, b.Filters.Headers, e.httpHeaderFiltersEqual) &&
-		bothNilOrEqualFunc(a.Filters.URLRewrite, b.Filters.URLRewrite, e.urlRewritesEqual)
+		bothNilOrEqualFunc(a.Filters.URLRewrite, b.Filters.URLRewrite, e.urlRewritesEqual) &&
+		slices.EqualFunc(a.ResponseFilters.Headers, b.ResponseFilters.Headers, e.httpHeaderFiltersEqual)
 }
 
 func (e entryComparator) httpMatchesEqual(a, b api.HTTPMatch) bool {

control-plane/api-gateway/common/translation.go

@@ -178,12 +178,13 @@ func (t ResourceTranslator) translateHTTPRouteRule(route gwv1beta1.HTTPRoute, ru
 	}
 
 	matches := ConvertSliceFunc(rule.Matches, t.translateHTTPMatch)
-	filters := t.translateHTTPFilters(rule.Filters, resources, route.Namespace)
+	filters, responseFilters := t.translateHTTPFilters(rule.Filters, resources, route.Namespace)
 
 	return api.HTTPRouteRule{
-		Services: services,
-		Matches:  matches,
-		Filters:  filters,
+		Filters:         filters,
+		Matches:         matches,
+		ResponseFilters: responseFilters,
+		Services:        services,
 	}, true
 }
 
@@ -196,28 +197,30 @@ func (t ResourceTranslator) translateHTTPBackendRef(route gwv1beta1.HTTPRoute, r
 	isServiceRef := NilOrEqual(ref.Group, "") && NilOrEqual(ref.Kind, "Service")
 
 	if isServiceRef && resources.HasService(id) && resources.HTTPRouteCanReferenceBackend(route, ref.BackendRef) {
-		filters := t.translateHTTPFilters(ref.Filters, resources, route.Namespace)
+		filters, responseFilters := t.translateHTTPFilters(ref.Filters, resources, route.Namespace)
 		service := resources.Service(id)
 		return api.HTTPService{
-			Name:      service.Name,
-			Namespace: service.Namespace,
-			Partition: t.ConsulPartition,
-			Filters:   filters,
-			Weight:    DerefIntOr(ref.Weight, 1),
+			Name:            service.Name,
+			Namespace:       service.Namespace,
+			Partition:       t.ConsulPartition,
+			Filters:         filters,
+			ResponseFilters: responseFilters,
+			Weight:          DerefIntOr(ref.Weight, 1),
 		}, true
 	}
 
 	isMeshServiceRef := DerefEqual(ref.Group, v1alpha1.ConsulHashicorpGroup) && DerefEqual(ref.Kind, v1alpha1.MeshServiceKind)
 	if isMeshServiceRef && resources.HasMeshService(id) && resources.HTTPRouteCanReferenceBackend(route, ref.BackendRef) {
-		filters := t.translateHTTPFilters(ref.Filters, resources, route.Namespace)
+		filters, responseFilters := t.translateHTTPFilters(ref.Filters, resources, route.Namespace)
 		service := resources.MeshService(id)
 
 		return api.HTTPService{
-			Name:      service.Name,
-			Namespace: service.Namespace,
-			Partition: t.ConsulPartition,
-			Filters:   filters,
-			Weight:    DerefIntOr(ref.Weight, 1),
+			Name:            service.Name,
+			Namespace:       service.Namespace,
+			Partition:       t.ConsulPartition,
+			Filters:         filters,
+			ResponseFilters: responseFilters,
+			Weight:          DerefIntOr(ref.Weight, 1),
 		}, true
 	}
 
@@ -275,26 +278,61 @@ func (t ResourceTranslator) translateHTTPQueryMatch(match gwv1beta1.HTTPQueryPar
 	}
 }
 
-func (t ResourceTranslator) translateHTTPFilters(filters []gwv1beta1.HTTPRouteFilter, resourceMap *ResourceMap, namespace string) api.HTTPFilters {
-	var urlRewrite *api.URLRewrite
-	consulFilter := api.HTTPHeaderFilter{
-		Add: make(map[string]string),
-		Set: make(map[string]string),
-	}
-	var retryFilter *api.RetryFilter
-	var timeoutFilter *api.TimeoutFilter
-
+func (t ResourceTranslator) translateHTTPFilters(filters []gwv1beta1.HTTPRouteFilter, resourceMap *ResourceMap, namespace string) (api.HTTPFilters, api.HTTPResponseFilters) {
+	var (
+		urlRewrite            *api.URLRewrite
+		retryFilter           *api.RetryFilter
+		timeoutFilter         *api.TimeoutFilter
+		requestHeaderFilters  = []api.HTTPHeaderFilter{}
+		responseHeaderFilters = []api.HTTPHeaderFilter{}
+	)
+
+	// Convert Gateway API filters to portions of the Consul request and response filters.
+	// Multiple filters applying the same or conflicting operations are allowed but may
+	// result in unexpected behavior.
 	for _, filter := range filters {
 		if filter.RequestHeaderModifier != nil {
-			consulFilter.Remove = append(consulFilter.Remove, filter.RequestHeaderModifier.Remove...)
+			newFilter := api.HTTPHeaderFilter{}
 
-			for _, toAdd := range filter.RequestHeaderModifier.Add {
-				consulFilter.Add[string(toAdd.Name)] = toAdd.Value
+			newFilter.Remove = append(newFilter.Remove, filter.RequestHeaderModifier.Remove...)
+
+			if len(filter.RequestHeaderModifier.Add) > 0 {
+				newFilter.Add = map[string]string{}
+				for _, toAdd := range filter.RequestHeaderModifier.Add {
+					newFilter.Add[string(toAdd.Name)] = toAdd.Value
+				}
 			}
 
-			for _, toSet := range filter.RequestHeaderModifier.Set {
-				consulFilter.Set[string(toSet.Name)] = toSet.Value
+			if len(filter.RequestHeaderModifier.Set) > 0 {
+				newFilter.Set = map[string]string{}
+				for _, toSet := range filter.RequestHeaderModifier.Set {
+					newFilter.Set[string(toSet.Name)] = toSet.Value
+				}
 			}
+
+			requestHeaderFilters = append(requestHeaderFilters, newFilter)
+		}
+
+		if filter.ResponseHeaderModifier != nil {
+			newFilter := api.HTTPHeaderFilter{}
+
+			newFilter.Remove = append(newFilter.Remove, filter.ResponseHeaderModifier.Remove...)
+
+			if len(filter.ResponseHeaderModifier.Add) > 0 {
+				newFilter.Add = map[string]string{}
+				for _, toAdd := range filter.ResponseHeaderModifier.Add {
+					newFilter.Add[string(toAdd.Name)] = toAdd.Value
+				}
+			}
+
+			if len(filter.ResponseHeaderModifier.Set) > 0 {
+				newFilter.Set = map[string]string{}
+				for _, toSet := range filter.ResponseHeaderModifier.Set {
+					newFilter.Set[string(toSet.Name)] = toSet.Value
+				}
+			}
+
+			responseHeaderFilters = append(responseHeaderFilters, newFilter)
 		}
 
 		// we drop any path rewrites that are not prefix matches as we don't support those
@@ -338,12 +376,19 @@ func (t ResourceTranslator) translateHTTPFilters(filters []gwv1beta1.HTTPRouteFi
 		}
 
 	}
-	return api.HTTPFilters{
-		Headers:       []api.HTTPHeaderFilter{consulFilter},
+
+	requestFilter := api.HTTPFilters{
+		Headers:       requestHeaderFilters,
 		URLRewrite:    urlRewrite,
 		RetryFilter:   retryFilter,
 		TimeoutFilter: timeoutFilter,
 	}
+
+	responseFilter := api.HTTPResponseFilters{
+		Headers: responseHeaderFilters,
+	}
+
+	return requestFilter, responseFilter
 }
 
 func (t ResourceTranslator) ToTCPRoute(route gwv1alpha2.TCPRoute, resources *ResourceMap) *api.TCPRouteConfigEntry {