feat(kuma-cp) add GatewayRoute route generation

api/mesh/v1alpha1/gateway_route.proto

@@ -272,12 +272,16 @@ message GatewayRoute {
 
       // Filters are request processing steps that are applied to
       // matched requests.
+      //
+      // If the redirect filter is specified, it must be the only
+      // filter given.
       repeated Filter filters = 2;
 
       // Backends is the set of services to which the gateway will
-      // forward requests.
-      repeated Backend backends = 3
-          [ (doc.required) = true, (validate.rules).repeated .min_items = 1 ];
+      // forward requests. If a redirect filter is specified, no
+      // backends are allowed. Otherwise, at least one backend
+      // must be given.
+      repeated Backend backends = 3 [ (doc.required) = false ];
     };
 
     // Hostnames lists the server names for which this route is valid. The

pkg/core/resources/apis/mesh/gateway_route_validator.go

@@ -104,24 +104,46 @@ func validateGatewayRouteHTTPRule(
 	path validators.PathBuilder,
 	conf *mesh_proto.GatewayRoute_HttpRoute_Rule,
 ) validators.ValidationError {
+	var hasRedirect bool
+
 	if len(conf.GetMatches()) < 1 {
 		return validators.MakeRequiredFieldErr(path.Field("matches"))
 	}
 
-	if len(conf.GetBackends()) < 1 {
-		return validators.MakeRequiredFieldErr(path.Field("backends"))
-	}
-
 	var err validators.ValidationError
 
 	for i, m := range conf.GetMatches() {
 		err.Add(validateGatewayRouteHTTPMatch(path.Field("matches").Index(i), m))
 	}
 
 	for i, f := range conf.GetFilters() {
+		if f.GetRedirect() != nil {
+			hasRedirect = true
+		}
+
 		err.Add(validateGatewayRouteHTTPFilter(path.Field("filters").Index(i), f))
 	}
 
+	// It doesn't make sense to redirect and also mirror or rewrite request headers.
+	if hasRedirect && len(conf.GetFilters()) != 1 {
+		err.AddViolationAt(path.Field("filters"), "redirects cannot be used with other filters")
+
+		// Return since the redirect filter error makes the backend length check ambiguous.
+		return err
+	}
+
+	switch len(conf.GetBackends()) {
+	case 0:
+		// Redirection doesn't forward, so there must not be any backend.
+		if !hasRedirect {
+			err.AddViolationAt(path.Field("backends"), "cannot be empty")
+		}
+	default:
+		if hasRedirect {
+			err.AddViolationAt(path.Field("backends"), "must be empty when using redirect filters")
+		}
+	}
+
 	for i, b := range conf.GetBackends() {
 		err.Add(validateGatewayRouteBackend(path.Field("backends").Index(i), b))
 	}

pkg/core/resources/apis/mesh/gateway_route_validator_test.go

@@ -23,6 +23,7 @@ func (g GatewayRouteGenerator) New() model.Resource {
 
 var _ = Describe("GatewayRoute", func() {
 	DescribeValidCases(GatewayRouteGenerator(NewGatewayRouteResource),
+
 		Entry("HTTP route", `
 type: GatewayRoute
 name: route
@@ -53,19 +54,18 @@ conf:
           value: kong
       filters:
       - request_header:
-        set:
-        - name: x-foo
-          value: foo
-        add:
-        - name: x-added
-          value: added
-        remove:
-        - x-deleted
-      - redirect:
-         scheme: http
-         hostname: foo.example.com
-         port: 80
-         status_code: 307
+          set:
+          - name: x-foo
+            value: foo
+          - name: x-foo
+            value: foo
+          add:
+          - name: x-added
+            value: added
+          - name: x-added
+            value: added
+          remove:
+          - x-deleted
       - mirror:
          percentage: 1.12
          backend:
@@ -78,6 +78,41 @@ conf:
       - weight: 5
         destination:
           kuma.io/service: target-2
+`),
+		Entry("HTTP redirect", `
+type: GatewayRoute
+name: route
+mesh: default
+selectors:
+- match:
+    kuma.io/service: gateway
+conf:
+  http:
+    hostnames:
+    - foo.example.com
+    rules:
+    - matches:
+      - method: GET
+        path:
+          match: EXACT
+          value: /
+        headers:
+        - match: EXACT
+          name: x-foo
+          value: "my great foo"
+        - match: REGEX
+          name: x-count
+          value: "[0-9]+"
+        query_parameters:
+        - match: EXACT
+          name: customer
+          value: kong
+      filters:
+      - redirect:
+         scheme: http
+         hostname: foo.example.com
+         port: 80
+         status_code: 307
 `),
 	)
 
@@ -496,10 +531,6 @@ conf:
       - redirect:
           hostname: example.com
           status_code: 301
-      backends:
-      - weight: 5
-        destination:
-          kuma.io/service: target-2
 `),
 		ErrorCase("redirect filter with empty hostname", validators.Violation{
 			Field:   "conf.http.rules[0].filters[0].redirect.hostname",
@@ -521,10 +552,6 @@ conf:
       - redirect:
           scheme: https
           status_code: 301
-      backends:
-      - weight: 5
-        destination:
-          kuma.io/service: target-2
 `),
 		ErrorCase("redirect filter with invalid port", validators.Violation{
 			Field:   "conf.http.rules[0].filters[0].redirect.port",
@@ -548,10 +575,6 @@ conf:
           hostname: example.com
           port: 128555
           status_code: 301
-      backends:
-      - weight: 5
-        destination:
-          kuma.io/service: target-2
 `),
 		ErrorCase("redirect filter with invalid status", validators.Violation{
 			Field:   "conf.http.rules[0].filters[0].redirect.status_code",
@@ -574,10 +597,59 @@ conf:
           scheme: https
           hostname: example.com
           status_code: 500
+`),
+		ErrorCase("redirect filter with backend routes", validators.Violation{
+			Field:   "conf.http.rules[0].backends",
+			Message: "must be empty when using redirect filters",
+		}, `
+type: GatewayRoute
+name: route
+mesh: default
+selectors:
+- match:
+    kuma.io/service: gateway
+conf:
+  http:
+    rules:
+    - matches:
+      - path:
+          value: /
+      filters:
+      - redirect:
+          scheme: https
+          hostname: example.com
+          status_code: 300
       backends:
       - weight: 5
         destination:
           kuma.io/service: target-2
+`),
+		ErrorCase("redirect prevents other filters", validators.Violation{
+			Field:   "conf.http.rules[0].filters",
+			Message: "redirects cannot be used with other filters",
+		}, `
+type: GatewayRoute
+name: route
+mesh: default
+selectors:
+- match:
+    kuma.io/service: gateway
+conf:
+  http:
+    rules:
+    - matches:
+      - path:
+          value: /
+      filters:
+      - redirect:
+          scheme: https
+          hostname: example.com
+          status_code: 300
+      - mirror:
+        backends:
+        - weight: 5
+          destination:
+            kuma.io/service: target-2
 `),
 	)
 })