NET-5530 Support response header modifiers on http-route config entry

.changelog/18646.txt

@@ -0,0 +1,3 @@
+```release-note:feature
+api-gateway: Add support for response header modifiers on http-route configuration entry
+```

agent/consul/discoverychain/gateway.go

@@ -27,9 +27,10 @@ type GatewayChainSynthesizer struct {
 }
 
 type hostnameMatch struct {
-	match    structs.HTTPMatch
-	filters  structs.HTTPFilters
-	services []structs.HTTPService
+	match           structs.HTTPMatch
+	filters         structs.HTTPFilters
+	responseFilters structs.HTTPResponseFilters
+	services        []structs.HTTPService
 }
 
 // NewGatewayChainSynthesizer creates a new GatewayChainSynthesizer for the
@@ -87,9 +88,10 @@ func initHostMatches(hostname string, route *structs.HTTPRouteConfigEntry, curre
 			// Add all matches for this rule to the list for this hostname
 			for _, match := range rule.Matches {
 				matches = append(matches, hostnameMatch{
-					match:    match,
-					filters:  rule.Filters,
-					services: rule.Services,
+					match:           match,
+					filters:         rule.Filters,
+					responseFilters: rule.ResponseFilters,
+					services:        rule.Services,
 				})
 			}
 		}
@@ -226,9 +228,10 @@ func consolidateHTTPRoutes(matchesByHostname map[string][]hostnameMatch, listene
 		// Add all rules for this hostname
 		for _, rule := range rules {
 			route.Rules = append(route.Rules, structs.HTTPRouteRule{
-				Matches:  []structs.HTTPMatch{rule.match},
-				Filters:  rule.filters,
-				Services: rule.services,
+				Matches:         []structs.HTTPMatch{rule.match},
+				Filters:         rule.filters,
+				ResponseFilters: rule.responseFilters,
+				Services:        rule.services,
 			})
 		}
 

agent/consul/discoverychain/gateway_httproute.go

@@ -79,7 +79,8 @@ func httpRouteToDiscoveryChain(route structs.HTTPRouteConfigEntry) (*structs.Ser
 	var defaults []*structs.ServiceConfigEntry
 
 	for idx, rule := range route.Rules {
-		modifier := httpRouteFiltersToServiceRouteHeaderModifier(rule.Filters.Headers)
+		requestModifier := httpRouteFiltersToServiceRouteHeaderModifier(rule.Filters.Headers)
+		responseModifier := httpRouteFiltersToServiceRouteHeaderModifier(rule.ResponseFilters.Headers)
 		prefixRewrite := httpRouteFiltersToDestinationPrefixRewrite(rule.Filters.URLRewrite)
 
 		var destination structs.ServiceRouteDestination
@@ -90,16 +91,29 @@ func httpRouteToDiscoveryChain(route structs.HTTPRouteConfigEntry) (*structs.Ser
 			if service.Filters.URLRewrite == nil {
 				servicePrefixRewrite = prefixRewrite
 			}
-			serviceModifier := httpRouteFiltersToServiceRouteHeaderModifier(service.Filters.Headers)
-			modifier.Add = mergeMaps(modifier.Add, serviceModifier.Add)
-			modifier.Set = mergeMaps(modifier.Set, serviceModifier.Set)
-			modifier.Remove = append(modifier.Remove, serviceModifier.Remove...)
+
+			// Merge service request header modifier(s) onto route rule modifiers
+			// Note: Removals for the same header may exist on the rule + the service and
+			//   will result in idempotent duplicate values in the modifier w/ service coming last
+			serviceRequestModifier := httpRouteFiltersToServiceRouteHeaderModifier(service.Filters.Headers)
+			requestModifier.Add = mergeMaps(requestModifier.Add, serviceRequestModifier.Add)
+			requestModifier.Set = mergeMaps(requestModifier.Set, serviceRequestModifier.Set)
+			requestModifier.Remove = append(requestModifier.Remove, serviceRequestModifier.Remove...)
+
+			// Merge service response header modifier(s) onto route rule modifiers
+			// Note: Removals for the same header may exist on the rule + the service and
+			//   will result in idempotent duplicate values in the modifier w/ service coming last
+			serviceResponseModifier := httpRouteFiltersToServiceRouteHeaderModifier(service.ResponseFilters.Headers)
+			responseModifier.Add = mergeMaps(responseModifier.Add, serviceResponseModifier.Add)
+			responseModifier.Set = mergeMaps(responseModifier.Set, serviceResponseModifier.Set)
+			responseModifier.Remove = append(responseModifier.Remove, serviceResponseModifier.Remove...)
 
 			destination.Service = service.Name
 			destination.Namespace = service.NamespaceOrDefault()
 			destination.Partition = service.PartitionOrDefault()
 			destination.PrefixRewrite = servicePrefixRewrite
-			destination.RequestHeaders = modifier
+			destination.RequestHeaders = requestModifier
+			destination.ResponseHeaders = responseModifier
 
 			// since we have already validated the protocol elsewhere, we
 			// create a new service defaults here to make sure we pass validation
@@ -115,7 +129,8 @@ func httpRouteToDiscoveryChain(route structs.HTTPRouteConfigEntry) (*structs.Ser
 			destination.Namespace = route.NamespaceOrDefault()
 			destination.Partition = route.PartitionOrDefault()
 			destination.PrefixRewrite = prefixRewrite
-			destination.RequestHeaders = modifier
+			destination.RequestHeaders = requestModifier
+			destination.ResponseHeaders = responseModifier
 
 			splitter := &structs.ServiceSplitterConfigEntry{
 				Kind:           structs.ServiceSplitter,

agent/consul/discoverychain/gateway_test.go

@@ -518,8 +518,70 @@ func TestGatewayChainSynthesizer_Synthesize(t *testing.T) {
 					Kind: structs.HTTPRoute,
 					Name: "http-route",
 					Rules: []structs.HTTPRouteRule{{
+						Filters: structs.HTTPFilters{
+							Headers: []structs.HTTPHeaderFilter{
+								{
+									Add:    map[string]string{"add me to the rule request": "present"},
+									Set:    map[string]string{"set me on the rule request": "present"},
+									Remove: []string{"remove me from the rule request"},
+								},
+								{
+									Add: map[string]string{"add me to the rule and service request": "rule"},
+									Set: map[string]string{"set me on the rule and service request": "rule"},
+								},
+								{
+									Remove: []string{"remove me from the rule and service request"},
+								},
+							},
+						},
+						ResponseFilters: structs.HTTPResponseFilters{
+							Headers: []structs.HTTPHeaderFilter{{
+								Add: map[string]string{
+									"add me to the rule response":             "present",
+									"add me to the rule and service response": "rule",
+								},
+								Set: map[string]string{
+									"set me on the rule response":             "present",
+									"set me on the rule and service response": "rule",
+								},
+								Remove: []string{
+									"remove me from the rule response",
+									"remove me from the rule and service response",
+								},
+							}},
+						},
 						Services: []structs.HTTPService{{
 							Name: "foo",
+							Filters: structs.HTTPFilters{
+								Headers: []structs.HTTPHeaderFilter{
+									{
+										Add: map[string]string{"add me to the service request": "present"},
+									},
+									{
+										Set:    map[string]string{"set me on the service request": "present"},
+										Remove: []string{"remove me from the service request"},
+									},
+									{
+										Add:    map[string]string{"add me to the rule and service request": "service"},
+										Set:    map[string]string{"set me on the rule and service request": "service"},
+										Remove: []string{"remove me from the rule and service request"},
+									},
+								},
+							},
+							ResponseFilters: structs.HTTPResponseFilters{
+								Headers: []structs.HTTPHeaderFilter{
+									{
+										Add:    map[string]string{"add me to the service response": "present"},
+										Set:    map[string]string{"set me on the service response": "present"},
+										Remove: []string{"remove me from the service response"},
+									},
+									{
+										Add:    map[string]string{"add me to the rule and service response": "service"},
+										Set:    map[string]string{"set me on the rule and service response": "service"},
+										Remove: []string{"remove me from the rule and service response"},
+									},
+								},
+							},
 						}},
 					}},
 				},
@@ -557,8 +619,40 @@ func TestGatewayChainSynthesizer_Synthesize(t *testing.T) {
 									Partition: "default",
 									Namespace: "default",
 									RequestHeaders: &structs.HTTPHeaderModifiers{
-										Add: make(map[string]string),
-										Set: make(map[string]string),
+										Add: map[string]string{
+											"add me to the rule request":             "present",
+											"add me to the service request":          "present",
+											"add me to the rule and service request": "service",
+										},
+										Set: map[string]string{
+											"set me on the rule request":             "present",
+											"set me on the service request":          "present",
+											"set me on the rule and service request": "service",
+										},
+										Remove: []string{
+											"remove me from the rule request",
+											"remove me from the rule and service request",
+											"remove me from the service request",
+											"remove me from the rule and service request",
+										},
+									},
+									ResponseHeaders: &structs.HTTPHeaderModifiers{
+										Add: map[string]string{
+											"add me to the rule response":             "present",
+											"add me to the service response":          "present",
+											"add me to the rule and service response": "service",
+										},
+										Set: map[string]string{
+											"set me on the rule response":             "present",
+											"set me on the service response":          "present",
+											"set me on the rule and service response": "service",
+										},
+										Remove: []string{
+											"remove me from the rule response",
+											"remove me from the rule and service response",
+											"remove me from the service response",
+											"remove me from the rule and service response",
+										},
 									},
 								},
 							},
@@ -663,6 +757,10 @@ func TestGatewayChainSynthesizer_Synthesize(t *testing.T) {
 										Add: make(map[string]string),
 										Set: make(map[string]string),
 									},
+									ResponseHeaders: &structs.HTTPHeaderModifiers{
+										Add: make(map[string]string),
+										Set: make(map[string]string),
+									},
 								},
 							},
 							NextNode: "resolver:foo-2.default.default.dc2",
@@ -850,6 +948,10 @@ func TestGatewayChainSynthesizer_ComplexChain(t *testing.T) {
 										Add: make(map[string]string),
 										Set: make(map[string]string),
 									},
+									ResponseHeaders: &structs.HTTPHeaderModifiers{
+										Add: make(map[string]string),
+										Set: make(map[string]string),
+									},
 								},
 							},
 							NextNode: "splitter:splitter-one.default.default",

agent/structs/config_entry_routes.go

@@ -457,6 +457,12 @@ type HTTPFilters struct {
 	JWT           *JWTFilter
 }
 
+// HTTPResponseFilters specifies a list of filters used to modify the
+// response returned by an upstream
+type HTTPResponseFilters struct {
+	Headers []HTTPHeaderFilter
+}
+
 // HTTPHeaderFilter specifies how HTTP headers should be modified.
 type HTTPHeaderFilter struct {
 	Add    map[string]string
@@ -486,6 +492,9 @@ type HTTPRouteRule struct {
 	// Filters is a list of HTTP-based filters used to modify a request prior
 	// to routing it to the upstream service
 	Filters HTTPFilters
+	// ResponseFilters is a list of HTTP-based filters used to modify a response
+	// returned by the upstream service
+	ResponseFilters HTTPResponseFilters
 	// Matches specified the matching criteria used in the routing table. If a
 	// request matches the given HTTPMatch configuration, then traffic is routed
 	// to services specified in the Services field.
@@ -505,6 +514,10 @@ type HTTPService struct {
 	// to routing it to the upstream service
 	Filters HTTPFilters
 
+	// ResponseFilters is a list of HTTP-based filters used to modify the
+	// response returned from the upstream service
+	ResponseFilters HTTPResponseFilters
+
 	acl.EnterpriseMeta `hcl:",squash" mapstructure:",squash"`
 }
 

api/config_entry_routes.go

@@ -204,6 +204,12 @@ type HTTPFilters struct {
 	JWT           *JWTFilter
 }
 
+// HTTPResponseFilters specifies a list of filters used to modify a
+// response returned by an upstream
+type HTTPResponseFilters struct {
+	Headers []HTTPHeaderFilter
+}
+
 // HTTPHeaderFilter specifies how HTTP headers should be modified.
 type HTTPHeaderFilter struct {
 	Add    map[string]string
@@ -238,6 +244,9 @@ type HTTPRouteRule struct {
 	// Filters is a list of HTTP-based filters used to modify a request prior
 	// to routing it to the upstream service
 	Filters HTTPFilters
+	// ResponseFilters is a list of HTTP-based filters used to modify a response
+	// returned by the upstream service
+	ResponseFilters HTTPResponseFilters
 	// Matches specified the matching criteria used in the routing table. If a
 	// request matches the given HTTPMatch configuration, then traffic is routed
 	// to services specified in the Services field.
@@ -253,10 +262,15 @@ type HTTPService struct {
 	// Weight is an arbitrary integer used in calculating how much
 	// traffic should be sent to the given service.
 	Weight int
+
 	// Filters is a list of HTTP-based filters used to modify a request prior
 	// to routing it to the upstream service
 	Filters HTTPFilters
 
+	// ResponseFilters is a list of HTTP-based filters used to modify the
+	// response returned from the upstream service
+	ResponseFilters HTTPResponseFilters
+
 	// Partition is the partition the config entry is associated with.
 	// Partitioning is a Consul Enterprise feature.
 	Partition string `json:",omitempty"`