feat(gateway): support URL rewriting (#4638)

Closes #4179, closes #3908

* feat(gateway): support URL rewriting
* test(e2e): enable experimental channel in tests
* test(e2e): add gatewy URL rewrite test
* chore(api): remove unused Messages
* refactor(gatewayapi): extract helper method
* test(e2e): fix path handling
* refactor(gateway): var naming
* feat(gateway): add validation for replacePrefixMatch

Signed-off-by: Mike Beaumont <mjboamail@gmail.com>

api/mesh/v1alpha1/gateway_route.proto

@@ -245,10 +245,18 @@ message MeshGatewayRoute {
         ];
       };
 
+      message Rewrite {
+        oneof path {
+          string replace_full = 1;
+          string replace_prefix_match = 2;
+        }
+      }
+
       oneof filter {
         RequestHeader request_header = 1;
         Mirror mirror = 2;
         Redirect redirect = 3;
+        Rewrite rewrite = 4;
       }
     };
 

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

@@ -101,6 +101,7 @@ func validateMeshGatewayRouteHTTPRule(
 	conf *mesh_proto.MeshGatewayRoute_HttpRoute_Rule,
 ) validators.ValidationError {
 	var hasRedirect bool
+	var hasPrefixMatch bool
 
 	if len(conf.GetMatches()) < 1 {
 		return validators.MakeRequiredFieldErr(path.Field("matches"))
@@ -110,14 +111,18 @@ func validateMeshGatewayRouteHTTPRule(
 
 	for i, m := range conf.GetMatches() {
 		err.Add(validateMeshGatewayRouteHTTPMatch(path.Field("matches").Index(i), m))
+
+		if p := m.GetPath(); p != nil && p.GetMatch() == mesh_proto.MeshGatewayRoute_HttpRoute_Match_Path_PREFIX {
+			hasPrefixMatch = true
+		}
 	}
 
 	for i, f := range conf.GetFilters() {
 		if f.GetRedirect() != nil {
 			hasRedirect = true
 		}
 
-		err.Add(validateMeshGatewayRouteHTTPFilter(path.Field("filters").Index(i), f))
+		err.Add(validateMeshGatewayRouteHTTPFilter(path.Field("filters").Index(i), f, hasPrefixMatch))
 	}
 
 	// It doesn't make sense to redirect and also mirror or rewrite request headers.
@@ -199,6 +204,7 @@ func validateMeshGatewayRouteHTTPMatch(
 func validateMeshGatewayRouteHTTPFilter(
 	path validators.PathBuilder,
 	conf *mesh_proto.MeshGatewayRoute_HttpRoute_Filter,
+	hasPrefixMatch bool,
 ) validators.ValidationError {
 	var err validators.ValidationError
 
@@ -267,6 +273,13 @@ func validateMeshGatewayRouteHTTPFilter(
 		))
 	}
 
+	if m := conf.GetRewrite(); m != nil {
+		path := path.Field("rewrite")
+		if _, ok := m.GetPath().(*mesh_proto.MeshGatewayRoute_HttpRoute_Filter_Rewrite_ReplacePrefixMatch); ok && !hasPrefixMatch {
+			err.AddViolationAt(path.Field("replacePrefixMatch"), "cannot be used without a match on path prefix")
+		}
+	}
+
 	return err
 }
 

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

@@ -649,6 +649,30 @@ conf:
         - weight: 5
           destination:
             kuma.io/service: target-2
+`),
+		ErrorCase("prefix match replacement without prefix match filter", validators.Violation{
+			Field:   "conf.http.rules[0].filters[0].rewrite.replacePrefixMatch",
+			Message: "cannot be used without a match on path prefix",
+		}, `
+type: MeshGatewayRoute
+name: route
+mesh: default
+selectors:
+- match:
+    kuma.io/service: gateway
+conf:
+  http:
+    rules:
+    - matches:
+      - path:
+          value: /exact_path
+      filters:
+      - rewrite:
+          replacePrefixMatch: "/"
+      backends:
+      - weight: 5
+        destination:
+          kuma.io/service: target-2
 `),
 	)
 })

pkg/plugins/runtime/gateway/gateway_route_generator.go

@@ -192,6 +192,19 @@ func makeHttpRouteEntry(name string, rule *mesh_proto.MeshGatewayRoute_HttpRoute
 
 			entry.RequestHeaders.Delete = append(
 				entry.RequestHeaders.Delete, h.GetRemove()...)
+		} else if r := f.GetRewrite(); r != nil {
+			rewrite := route.Rewrite{}
+
+			if p := r.GetPath(); p != nil {
+				switch t := p.(type) {
+				case *mesh_proto.MeshGatewayRoute_HttpRoute_Filter_Rewrite_ReplaceFull:
+					rewrite.ReplaceFullPath = &t.ReplaceFull
+				case *mesh_proto.MeshGatewayRoute_HttpRoute_Filter_Rewrite_ReplacePrefixMatch:
+					rewrite.ReplacePrefixMatch = &t.ReplacePrefixMatch
+				}
+			}
+
+			entry.Rewrite = &rewrite
 		}
 	}
 

pkg/plugins/runtime/gateway/route/configurers.go

@@ -323,6 +323,42 @@ func RouteActionRedirect(redirect *Redirection) RouteConfigurer {
 	})
 }
 
+func RouteRewrite(rewrite *Rewrite) RouteConfigurer {
+	if rewrite == nil {
+		return RouteConfigureFunc(nil)
+	}
+
+	return RouteConfigureFunc(func(r *envoy_config_route.Route) error {
+		if r.GetAction() == nil {
+			return errors.New("cannot configure rewrite before the route action")
+		}
+
+		action := r.GetRoute()
+
+		if action == nil {
+			return errors.New("cannot configure rewrite on a non-forwarding route")
+		}
+
+		if rewrite.ReplaceFullPath != nil {
+			action.RegexRewrite = &envoy_type_matcher.RegexMatchAndSubstitute{
+				Pattern: &envoy_type_matcher.RegexMatcher{
+					EngineType: &envoy_type_matcher.RegexMatcher_GoogleRe2{
+						GoogleRe2: &envoy_type_matcher.RegexMatcher_GoogleRE2{},
+					},
+					Regex: `.*`,
+				},
+				Substitution: *rewrite.ReplaceFullPath,
+			}
+		}
+
+		if rewrite.ReplacePrefixMatch != nil {
+			action.PrefixRewrite = *rewrite.ReplacePrefixMatch
+		}
+
+		return nil
+	})
+}
+
 // RouteActionForward configures the route to forward traffic to the
 // given destinations, with the appropriate weights. This replaces any
 // previous action specification.

pkg/plugins/runtime/gateway/route/table.go

@@ -36,6 +36,8 @@ type Entry struct {
 	// RequestHeaders specifies transformations on the HTTP
 	// request headers.
 	RequestHeaders *Headers
+
+	Rewrite *Rewrite
 }
 
 // KeyValue is a generic pairing of key and value strings. Route table
@@ -115,6 +117,12 @@ type Headers struct {
 	Delete []string
 }
 
+type Rewrite struct {
+	ReplaceFullPath *string
+
+	ReplacePrefixMatch *string
+}
+
 // Mirror specifies a traffic mirroring operation.
 type Mirror struct {
 	Forward    Destination

pkg/plugins/runtime/gateway/route_table_generator.go

@@ -124,6 +124,8 @@ func GenerateVirtualHost(
 			routeBuilder.Configure(route.RouteMirror(m.Percentage, m.Forward))
 		}
 
+		routeBuilder.Configure(route.RouteRewrite(e.Rewrite))
+
 		vh.Configure(route.VirtualHostRoute(&routeBuilder))
 	}
 

pkg/plugins/runtime/k8s/controllers/gatewayapi/http_route_conversion.go

@@ -59,14 +59,14 @@ func (r *HTTPRouteReconciler) gapiToKumaRule(
 	var filters []*mesh_proto.MeshGatewayRoute_HttpRoute_Filter
 
 	for _, filter := range rule.Filters {
-		kumaFilter, filterCondition, err := r.gapiToKumaFilter(ctx, mesh, route.Namespace, filter)
+		kumaFilters, filterCondition, err := r.gapiToKumaFilters(ctx, mesh, route.Namespace, filter)
 		if err != nil {
 			return nil, condition, err
 		}
 		if filterCondition != nil {
 			condition = filterCondition
 		} else {
-			filters = append(filters, kumaFilter)
+			filters = append(filters, kumaFilters...)
 		}
 	}
 
@@ -296,10 +296,30 @@ func gapiToKumaMatch(match gatewayapi.HTTPRouteMatch) (*mesh_proto.MeshGatewayRo
 	return kumaMatch, nil
 }
 
-func (r *HTTPRouteReconciler) gapiToKumaFilter(
+func pathRewriteToKuma(modifier gatewayapi.HTTPPathModifier) mesh_proto.MeshGatewayRoute_HttpRoute_Filter {
+	rewrite := mesh_proto.MeshGatewayRoute_HttpRoute_Filter_Rewrite{}
+
+	switch modifier.Type {
+	case gatewayapi.FullPathHTTPPathModifier:
+		rewrite.Path = &mesh_proto.MeshGatewayRoute_HttpRoute_Filter_Rewrite_ReplaceFull{
+			ReplaceFull: *modifier.ReplaceFullPath,
+		}
+	case gatewayapi.PrefixMatchHTTPPathModifier:
+		rewrite.Path = &mesh_proto.MeshGatewayRoute_HttpRoute_Filter_Rewrite_ReplacePrefixMatch{
+			ReplacePrefixMatch: *modifier.ReplacePrefixMatch,
+		}
+	}
+	return mesh_proto.MeshGatewayRoute_HttpRoute_Filter{
+		Filter: &mesh_proto.MeshGatewayRoute_HttpRoute_Filter_Rewrite_{
+			Rewrite: &rewrite,
+		},
+	}
+}
+
+func (r *HTTPRouteReconciler) gapiToKumaFilters(
 	ctx context.Context, mesh string, namespace string, filter gatewayapi.HTTPRouteFilter,
-) (*mesh_proto.MeshGatewayRoute_HttpRoute_Filter, *ResolvedRefsConditionFalse, error) {
-	var kumaFilter *mesh_proto.MeshGatewayRoute_HttpRoute_Filter
+) ([]*mesh_proto.MeshGatewayRoute_HttpRoute_Filter, *ResolvedRefsConditionFalse, error) {
+	var kumaFilters []*mesh_proto.MeshGatewayRoute_HttpRoute_Filter
 
 	var condition *ResolvedRefsConditionFalse
 
@@ -319,11 +339,11 @@ func (r *HTTPRouteReconciler) gapiToKumaFilter(
 
 		requestHeader.Remove = filter.Remove
 
-		kumaFilter = &mesh_proto.MeshGatewayRoute_HttpRoute_Filter{
+		kumaFilters = append(kumaFilters, &mesh_proto.MeshGatewayRoute_HttpRoute_Filter{
 			Filter: &mesh_proto.MeshGatewayRoute_HttpRoute_Filter_RequestHeader_{
 				RequestHeader: &requestHeader,
 			},
-		}
+		})
 	case gatewayapi.HTTPRouteFilterRequestMirror:
 		filter := filter.RequestMirror
 
@@ -342,14 +362,19 @@ func (r *HTTPRouteReconciler) gapiToKumaFilter(
 			Percentage: util_proto.Double(100),
 		}
 
-		kumaFilter = &mesh_proto.MeshGatewayRoute_HttpRoute_Filter{
+		kumaFilters = append(kumaFilters, &mesh_proto.MeshGatewayRoute_HttpRoute_Filter{
 			Filter: &mesh_proto.MeshGatewayRoute_HttpRoute_Filter_Mirror_{
 				Mirror: &mirror,
 			},
-		}
+		})
 	case gatewayapi.HTTPRouteFilterRequestRedirect:
 		filter := filter.RequestRedirect
 
+		if p := filter.Path; p != nil {
+			filter := pathRewriteToKuma(*p)
+			kumaFilters = append(kumaFilters, &filter)
+		}
+
 		redirect := mesh_proto.MeshGatewayRoute_HttpRoute_Filter_Redirect{}
 
 		if s := filter.Scheme; s != nil {
@@ -368,14 +393,34 @@ func (r *HTTPRouteReconciler) gapiToKumaFilter(
 			redirect.StatusCode = uint32(*sc)
 		}
 
-		kumaFilter = &mesh_proto.MeshGatewayRoute_HttpRoute_Filter{
+		kumaFilters = append(kumaFilters, &mesh_proto.MeshGatewayRoute_HttpRoute_Filter{
 			Filter: &mesh_proto.MeshGatewayRoute_HttpRoute_Filter_Redirect_{
 				Redirect: &redirect,
 			},
+		})
+	case gatewayapi.HTTPRouteFilterURLRewrite:
+		filter := filter.URLRewrite
+
+		if filter.Hostname != nil {
+			var requestHeader mesh_proto.MeshGatewayRoute_HttpRoute_Filter_RequestHeader
+			requestHeader.Set = append(requestHeader.Set, &mesh_proto.MeshGatewayRoute_HttpRoute_Filter_RequestHeader_Header{
+				Name:  "Host",
+				Value: string(*filter.Hostname),
+			})
+			kumaFilters = append(kumaFilters, &mesh_proto.MeshGatewayRoute_HttpRoute_Filter{
+				Filter: &mesh_proto.MeshGatewayRoute_HttpRoute_Filter_RequestHeader_{
+					RequestHeader: &requestHeader,
+				},
+			})
+		}
+
+		if p := filter.Path; p != nil {
+			filter := pathRewriteToKuma(*p)
+			kumaFilters = append(kumaFilters, &filter)
 		}
 	default:
 		return nil, nil, fmt.Errorf("unsupported filter type %q", filter.Type)
 	}
 
-	return kumaFilter, condition, nil
+	return kumaFilters, condition, nil
 }

test/e2e/gateway/gateway_kubernetes.go

@@ -5,6 +5,7 @@ import (
 	"encoding/base64"
 	"fmt"
 	"net"
+	"path"
 	"strings"
 	"text/template"
 
@@ -169,6 +170,20 @@ spec:
   conf:
     http:
       rules:
+      - matches:
+        - path:
+            match: PREFIX
+            value: /prefix/
+        filters:
+        - requestHeader:
+            set:
+              - name: Host
+                value: other.example.kuma.io
+        - rewrite:
+            replacePrefixMatch: "/"
+        backends:
+        - destination:
+            kuma.io/service: echo-server_kuma-test_svc_80 # Matches the echo-server we deployed.
       - matches:
         - path:
             match: PREFIX
@@ -273,6 +288,16 @@ spec:
 				client.FromKubernetesPod(ClientNamespace, "gateway-client"))
 		})
 
+		It("should rewrite HTTP requests", func() {
+			expectedPath := path.Join("/test", GinkgoT().Name())
+			targetPath := path.Join("prefix", "/test", GinkgoT().Name())
+			expectedHostname := "other.example.kuma.io"
+			ProxyHTTPRequests(cluster, "kubernetes",
+				net.JoinHostPort(GatewayAddress("edge-gateway"), GatewayPort),
+				targetPath, expectedPath, expectedHostname,
+				client.FromKubernetesPod(ClientNamespace, "gateway-client"))
+		})
+
 		It("should proxy TCP connections", func() {
 			ProxyTcpRequest(cluster, "request", "response",
 				net.JoinHostPort(GatewayAddress("edge-gateway"), "8081"),

test/e2e/gateway/gatewayapi/gateway_api.go

@@ -18,7 +18,7 @@ func GatewayAPICRDs(cluster Cluster) error {
 	return k8s.RunKubectlE(
 		cluster.GetTesting(),
 		cluster.GetKubectlOptions(),
-		"apply", "-f", "https://github.com/kubernetes-sigs/gateway-api/releases/download/v0.5.0/standard-install.yaml")
+		"apply", "-f", "https://github.com/kubernetes-sigs/gateway-api/releases/download/v0.5.0/experimental-install.yaml")
 }
 
 const GatewayClass = `