feat: sets the host automatically to Backend

internal/controller/sink.go

@@ -4,9 +4,11 @@ import (
 	"context"
 	"fmt"
 
+	egv1a1 "github.com/envoyproxy/gateway/api/v1alpha1"
 	"github.com/go-logr/logr"
 	appsv1 "k8s.io/api/apps/v1"
 	corev1 "k8s.io/api/core/v1"
+	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/client-go/kubernetes"
 	"k8s.io/utils/ptr"
@@ -18,7 +20,10 @@ import (
 	"github.com/envoyproxy/ai-gateway/filterconfig"
 )
 
-const selectedBackendHeaderKey = "x-ai-eg-selected-backend"
+const (
+	selectedBackendHeaderKey  = "x-ai-eg-selected-backend"
+	hostRewriteHTTPFilterName = "ai-eg-host-rewrite"
+)
 
 // mountedExtProcSecretPath specifies the secret file mounted on the external proc. The idea is to update the mounted
 //
@@ -110,16 +115,39 @@ func (c *configSink) handleEvent(event ConfigSinkEvent) {
 }
 
 func (c *configSink) syncAIGatewayRoute(aiGatewayRoute *aigv1a1.AIGatewayRoute) {
+	// Check if the HTTPRouteFilter exists in the namespace.
+	var httpRouteFilter egv1a1.HTTPRouteFilter
+	err := c.client.Get(context.Background(),
+		client.ObjectKey{Name: hostRewriteHTTPFilterName, Namespace: aiGatewayRoute.Namespace}, &httpRouteFilter)
+	if apierrors.IsNotFound(err) {
+		httpRouteFilter = egv1a1.HTTPRouteFilter{
+			ObjectMeta: metav1.ObjectMeta{
+				Name:      hostRewriteHTTPFilterName,
+				Namespace: aiGatewayRoute.Namespace,
+			},
+			Spec: egv1a1.HTTPRouteFilterSpec{
+				URLRewrite: &egv1a1.HTTPURLRewriteFilter{
+					Hostname: &egv1a1.HTTPHostnameModifier{
+						Type: egv1a1.BackendHTTPHostnameModifier,
+					},
+				},
+			},
+		}
+		if err := c.client.Create(context.Background(), &httpRouteFilter); err != nil {
+			c.logger.Error(err, "failed to create HTTPRouteFilter", "namespace", aiGatewayRoute.Namespace, "name", hostRewriteHTTPFilterName)
+			return
+		}
+	} else if err != nil {
+		c.logger.Error(err, "failed to get HTTPRouteFilter", "namespace", aiGatewayRoute.Namespace, "name", hostRewriteHTTPFilterName, "error", err)
+		return
+	}
+
 	// Check if the HTTPRoute exists.
 	c.logger.Info("syncing AIGatewayRoute", "namespace", aiGatewayRoute.Namespace, "name", aiGatewayRoute.Name)
 	var httpRoute gwapiv1.HTTPRoute
-	err := c.client.Get(context.Background(), client.ObjectKey{Name: aiGatewayRoute.Name, Namespace: aiGatewayRoute.Namespace}, &httpRoute)
+	err = c.client.Get(context.Background(), client.ObjectKey{Name: aiGatewayRoute.Name, Namespace: aiGatewayRoute.Namespace}, &httpRoute)
 	existingRoute := err == nil
-	if client.IgnoreNotFound(err) != nil {
-		c.logger.Error(err, "failed to get HTTPRoute", "namespace", aiGatewayRoute.Namespace, "name", aiGatewayRoute.Name)
-		return
-	}
-	if !existingRoute {
+	if apierrors.IsNotFound(err) {
 		// This means that this AIGatewayRoute is a new one.
 		httpRoute = gwapiv1.HTTPRoute{
 			ObjectMeta: metav1.ObjectMeta{
@@ -129,6 +157,9 @@ func (c *configSink) syncAIGatewayRoute(aiGatewayRoute *aigv1a1.AIGatewayRoute)
 			},
 			Spec: gwapiv1.HTTPRouteSpec{},
 		}
+	} else if err != nil {
+		c.logger.Error(err, "failed to get HTTPRoute", "namespace", aiGatewayRoute.Namespace, "name", aiGatewayRoute.Name, "error", err)
+		return
 	}
 
 	// Update the HTTPRoute with the new AIGatewayRoute.
@@ -300,6 +331,16 @@ func (c *configSink) newHTTPRoute(dst *gwapiv1.HTTPRoute, aiGatewayRoute *aigv1a
 		}
 	}
 
+	rewriteFilters := []gwapiv1.HTTPRouteFilter{
+		{
+			Type: gwapiv1.HTTPRouteFilterExtensionRef,
+			ExtensionRef: &gwapiv1.LocalObjectReference{
+				Group: "gateway.envoyproxy.io",
+				Kind:  "HTTPRouteFilter",
+				Name:  hostRewriteHTTPFilterName,
+			},
+		},
+	}
 	rules := make([]gwapiv1.HTTPRouteRule, len(backends))
 	for i, b := range backends {
 		key := fmt.Sprintf("%s.%s", b.Name, b.Namespace)
@@ -310,6 +351,7 @@ func (c *configSink) newHTTPRoute(dst *gwapiv1.HTTPRoute, aiGatewayRoute *aigv1a
 			Matches: []gwapiv1.HTTPRouteMatch{
 				{Headers: []gwapiv1.HTTPHeaderMatch{{Name: selectedBackendHeaderKey, Value: key}}},
 			},
+			Filters: rewriteFilters,
 		}
 		rules[i] = rule
 	}
@@ -322,6 +364,7 @@ func (c *configSink) newHTTPRoute(dst *gwapiv1.HTTPRoute, aiGatewayRoute *aigv1a
 		BackendRefs: []gwapiv1.HTTPBackendRef{
 			{BackendRef: gwapiv1.BackendRef{BackendObjectReference: backends[0].Spec.BackendRef}},
 		},
+		Filters: rewriteFilters,
 	})
 
 	dst.Spec.Rules = rules

internal/controller/sink_test.go

@@ -8,6 +8,7 @@ import (
 	"testing"
 	"time"
 
+	egv1a1 "github.com/envoyproxy/gateway/api/v1alpha1"
 	"github.com/go-logr/logr"
 	"github.com/stretchr/testify/require"
 	corev1 "k8s.io/api/core/v1"
@@ -81,10 +82,8 @@ func TestConfigSink_syncAIGatewayRoute(t *testing.T) {
 		}, metav1.CreateOptions{})
 		require.NoError(t, err)
 
-		// Then sync.
+		// Then sync, which should update the HTTPRoute.
 		s.syncAIGatewayRoute(route)
-		// Referencing backends should be updated.
-		// Also HTTPRoute should be updated.
 		var updatedHTTPRoute gwapiv1.HTTPRoute
 		err = fakeClient.Get(context.Background(), client.ObjectKey{Name: "route1", Namespace: "ns1"}, &updatedHTTPRoute)
 		require.NoError(t, err)
@@ -98,6 +97,12 @@ func TestConfigSink_syncAIGatewayRoute(t *testing.T) {
 		require.Equal(t, "some-backend1", string(updatedHTTPRoute.Spec.Rules[2].BackendRefs[0].BackendRef.Name))
 		require.Equal(t, "/", *updatedHTTPRoute.Spec.Rules[2].Matches[0].Path.Value)
 	})
+
+	// Check the namespace has the default host rewrite filter.
+	var f egv1a1.HTTPRouteFilter
+	err := s.client.Get(context.Background(), client.ObjectKey{Name: hostRewriteHTTPFilterName, Namespace: "ns1"}, &f)
+	require.NoError(t, err)
+	require.Equal(t, hostRewriteHTTPFilterName, f.Name)
 }
 
 func TestConfigSink_syncAIServiceBackend(t *testing.T) {
@@ -221,6 +226,12 @@ func Test_newHTTPRoute(t *testing.T) {
 				require.Equal(t, expRules[i].Matches, r.Matches)
 				require.Equal(t, expRules[i].BackendRefs, r.BackendRefs)
 			}
+
+			// Each rule should have a host rewrite filter by default.
+			require.Len(t, r.Filters, 1)
+			require.Equal(t, gwapiv1.HTTPRouteFilterExtensionRef, r.Filters[0].Type)
+			require.NotNil(t, r.Filters[0].ExtensionRef)
+			require.Equal(t, hostRewriteHTTPFilterName, string(r.Filters[0].ExtensionRef.Name))
 		})
 	}
 }

tests/controller/controller_test.go

@@ -211,10 +211,32 @@ func TestStartControllers(t *testing.T) {
 				require.Len(t, httpRoute.Spec.Rules[1].Matches[0].Headers, 1)
 				require.Equal(t, "x-ai-eg-selected-backend", string(httpRoute.Spec.Rules[1].Matches[0].Headers[0].Name))
 				require.Equal(t, "backend2.default", httpRoute.Spec.Rules[1].Matches[0].Headers[0].Value)
+
+				// Check all rule has the host rewrite filter.
+				for _, rule := range httpRoute.Spec.Rules {
+					require.Len(t, rule.Filters, 1)
+					require.NotNil(t, rule.Filters[0].ExtensionRef)
+					require.Equal(t, "ai-eg-host-rewrite", string(rule.Filters[0].ExtensionRef.Name))
+				}
 				return true
 			}, 30*time.Second, 200*time.Millisecond)
 		})
 	}
+
+	// Check if the host rewrite filter exists in the default namespace.
+	t.Run("verify host rewrite filter", func(t *testing.T) {
+		require.Eventually(t, func() bool {
+			var filter egv1a1.HTTPRouteFilter
+			err := c.Get(ctx, client.ObjectKey{Name: "ai-eg-host-rewrite", Namespace: "default"}, &filter)
+			if err != nil {
+				t.Logf("failed to get filter: %v", err)
+				return false
+			}
+			require.Equal(t, "default", filter.Namespace)
+			require.Equal(t, "ai-eg-host-rewrite", filter.Name)
+			return true
+		}, 30*time.Second, 200*time.Millisecond)
+	})
 }
 
 func TestAIGatewayRouteController(t *testing.T) {

tests/e2e/testdata/translation_testupstream.yaml

@@ -57,8 +57,8 @@ spec:
     name: OpenAI
   backendRef:
     name: testupstream
-    kind: Service
-    port: 80
+    kind: Backend
+    group: gateway.envoyproxy.io
 ---
 apiVersion: aigateway.envoyproxy.io/v1alpha1
 kind: AIServiceBackend
@@ -70,5 +70,27 @@ spec:
     name: AWSBedrock
   backendRef:
     name: testupstream-canary
-    kind: Service
-    port: 80
+    kind: Backend
+    group: gateway.envoyproxy.io
+---
+apiVersion: gateway.envoyproxy.io/v1alpha1
+kind: Backend
+metadata:
+  name: testupstream
+  namespace: default
+spec:
+  endpoints:
+    - fqdn:
+        hostname: testupstream.default.svc.cluster.local
+        port: 80
+---
+apiVersion: gateway.envoyproxy.io/v1alpha1
+kind: Backend
+metadata:
+  name: testupstream-canary
+  namespace: default
+spec:
+  endpoints:
+    - fqdn:
+        hostname: testupstream-canary.default.svc.cluster.local
+        port: 80

tests/e2e/translation_testupstream_test.go

@@ -34,6 +34,7 @@ func TestTranslationWithTestUpstream(t *testing.T) {
 		for _, tc := range []struct {
 			name              string
 			modelName         string
+			expHost           string
 			expTestUpstreamID string
 			expPath           string
 			fakeResponseBody  string
@@ -43,12 +44,14 @@ func TestTranslationWithTestUpstream(t *testing.T) {
 				modelName:         "some-cool-model",
 				expTestUpstreamID: "primary",
 				expPath:           "/v1/chat/completions",
+				expHost:           "testupstream.default.svc.cluster.local",
 				fakeResponseBody:  `{"choices":[{"message":{"content":"This is a test."}}]}`,
 			},
 			{
 				name:              "aws-bedrock",
 				modelName:         "another-cool-model",
 				expTestUpstreamID: "canary",
+				expHost:           "testupstream-canary.default.svc.cluster.local",
 				expPath:           "/model/another-cool-model/converse",
 				fakeResponseBody:  `{"output":{"message":{"content":[{"text":"response"},{"text":"from"},{"text":"assistant"}],"role":"assistant"}},"stopReason":null,"usage":{"inputTokens":10,"outputTokens":20,"totalTokens":30}}`,
 			},
@@ -66,7 +69,9 @@ func TestTranslationWithTestUpstream(t *testing.T) {
 							"x-expected-path", base64.StdEncoding.EncodeToString([]byte(tc.expPath))),
 						option.WithHeader("x-response-body",
 							base64.StdEncoding.EncodeToString([]byte(tc.fakeResponseBody)),
-						))
+						),
+						option.WithHeader("x-expected-host", tc.expHost),
+					)
 
 					chatCompletion, err := client.Chat.Completions.New(ctx, openai.ChatCompletionNewParams{
 						Messages: openai.F([]openai.ChatCompletionMessageParamUnion{

tests/envtest.go

@@ -28,12 +28,15 @@ func NewEnvTest(t *testing.T) (c client.Client, cfg *rest.Config, k kubernetes.I
 	for _, file := range files {
 		crds = append(crds, filepath.Join(crdPath, file.Name()))
 	}
-	const (
-		extensionPolicyURL = "https://raw.githubusercontent.com/envoyproxy/gateway/refs/tags/v1.2.4/charts/gateway-helm/crds/generated/gateway.envoyproxy.io_envoyextensionpolicies.yaml"
-		httpRouteURL       = "https://raw.githubusercontent.com/kubernetes-sigs/gateway-api/refs/tags/v1.2.1/config/crd/standard/gateway.networking.k8s.io_httproutes.yaml"
-	)
-	crds = append(crds, requireThirdPartyCRDDownloaded(t, "envoyextensionpolicies_crd_for_tests.yaml", extensionPolicyURL))
-	crds = append(crds, requireThirdPartyCRDDownloaded(t, "httproutes_crd_for_tests.yaml", httpRouteURL))
+
+	for _, url := range []string{
+		"https://raw.githubusercontent.com/envoyproxy/gateway/refs/tags/v1.2.4/charts/gateway-helm/crds/generated/gateway.envoyproxy.io_envoyextensionpolicies.yaml",
+		"https://raw.githubusercontent.com/envoyproxy/gateway/refs/tags/v1.2.5/charts/gateway-helm/crds/generated/gateway.envoyproxy.io_httproutefilters.yaml",
+		"https://raw.githubusercontent.com/kubernetes-sigs/gateway-api/refs/tags/v1.2.1/config/crd/standard/gateway.networking.k8s.io_httproutes.yaml",
+	} {
+		path := filepath.Base(url) + "_for_tests.yaml"
+		crds = append(crds, requireThirdPartyCRDDownloaded(t, path, url))
+	}
 
 	env := &envtest.Environment{CRDDirectoryPaths: crds}
 	cfg, err = env.Start()

tests/testupstream/main.go

@@ -55,6 +55,8 @@ const (
 	// If the values do not match, the request will be rejected, meaning that the request
 	// was routed to the wrong upstream.
 	expectedTestUpstreamIDKey = "x-expected-testupstream-id"
+	// expectedHostKey is the key for the expected host in the request.
+	expectedHostKey = "x-expected-host"
 )
 
 // main starts a server that listens on port 1063 and responds with the expected response body and headers
@@ -94,6 +96,16 @@ func handler(w http.ResponseWriter, r *http.Request) {
 	for k, v := range r.Header {
 		logger.Printf("header %q: %s\n", k, v)
 	}
+	if v := r.Header.Get(expectedHostKey); v != "" {
+		if r.Host != v {
+			fmt.Printf("unexpected host: got %q, expected %q\n", r.Host, v)
+			http.Error(w, "unexpected host: got "+r.Host+", expected "+v, http.StatusBadRequest)
+			return
+		}
+		fmt.Println("host matched:", v)
+	} else {
+		fmt.Println("no expected host: got", r.Host)
+	}
 	if v := r.Header.Get(expectedHeadersKey); v != "" {
 		expectedHeaders, err := base64.StdEncoding.DecodeString(v)
 		if err != nil {