implement header manipulation for nginxingress

pkg/i2gw/providers/ingressnginx/converter.go

@@ -33,6 +33,7 @@ func newResourcesToIRConverter() *resourcesToIRConverter {
 	return &resourcesToIRConverter{
 		featureParsers: []i2gw.FeatureParser{
 			canaryFeature,
+			headerModifierFeature,
 		},
 	}
 }

pkg/i2gw/providers/ingressnginx/headers.go

@@ -0,0 +1,124 @@
+/*
+Copyright 2023 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package ingressnginx
+
+import (
+	"fmt"
+
+	"github.com/kubernetes-sigs/ingress2gateway/pkg/i2gw/intermediate"
+	"github.com/kubernetes-sigs/ingress2gateway/pkg/i2gw/notifications"
+	networkingv1 "k8s.io/api/networking/v1"
+	"k8s.io/apimachinery/pkg/types"
+	"k8s.io/apimachinery/pkg/util/validation/field"
+	gatewayv1 "sigs.k8s.io/gateway-api/apis/v1"
+)
+
+const (
+	xForwardedPrefixAnnotation      = "nginx.ingress.kubernetes.io/x-forwarded-prefix"
+	upstreamVhostAnnotation         = "nginx.ingress.kubernetes.io/upstream-vhost"
+	connectionProxyHeaderAnnotation = "nginx.ingress.kubernetes.io/connection-proxy-header"
+)
+
+func headerModifierFeature(_ []networkingv1.Ingress, _ map[types.NamespacedName]map[string]int32, ir *intermediate.IR) field.ErrorList {
+	for _, httpRouteContext := range ir.HTTPRoutes {
+		for i := range httpRouteContext.HTTPRoute.Spec.Rules {
+			if i >= len(httpRouteContext.RuleBackendSources) {
+				continue
+			}
+			sources := httpRouteContext.RuleBackendSources[i]
+			if len(sources) == 0 {
+				continue
+			}
+
+			// Check the first source for the annotation
+			ingress := sources[0].Ingress
+			if ingress == nil {
+				continue
+			}
+
+			headersToSet := make(map[string]string)
+
+			// 1. x-forwarded-prefix
+			if val, ok := ingress.Annotations[xForwardedPrefixAnnotation]; ok && val != "" {
+				headersToSet["X-Forwarded-Prefix"] = val
+			}
+
+			// 2. upstream-vhost -> Host header
+			if val, ok := ingress.Annotations[upstreamVhostAnnotation]; ok && val != "" {
+				headersToSet["Host"] = val
+			}
+
+			// 3. connection-proxy-header -> Connection header
+			if val, ok := ingress.Annotations[connectionProxyHeaderAnnotation]; ok && val != "" {
+				headersToSet["Connection"] = val
+			}
+
+			// 4. custom-headers -> Warn unsupported
+			if _, ok := ingress.Annotations["nginx.ingress.kubernetes.io/custom-headers"]; ok {
+				notify(notifications.WarningNotification, fmt.Sprintf("Ingress %s/%s uses 'nginx.ingress.kubernetes.io/custom-headers' which is not supported as it requires cluster access to read ConfigMaps.", ingress.Namespace, ingress.Name), &httpRouteContext.HTTPRoute)
+			}
+
+			if len(headersToSet) > 0 {
+				// Create or append to RequestHeaderModifier filter
+				applyHeaderModifiers(ingress, &httpRouteContext.HTTPRoute, i, headersToSet)
+			}
+		}
+	}
+	return nil
+}
+
+func applyHeaderModifiers(ingress *networkingv1.Ingress, httpRoute *gatewayv1.HTTPRoute, ruleIndex int, headersToSet map[string]string) {
+	// Check if a RequestHeaderModifier filter already exists
+	var filter *gatewayv1.HTTPRouteFilter
+	for j, f := range httpRoute.Spec.Rules[ruleIndex].Filters {
+		if f.Type == gatewayv1.HTTPRouteFilterRequestHeaderModifier && f.RequestHeaderModifier != nil {
+			filter = &httpRoute.Spec.Rules[ruleIndex].Filters[j]
+			break
+		}
+	}
+
+	if filter == nil {
+		f := gatewayv1.HTTPRouteFilter{
+			Type: gatewayv1.HTTPRouteFilterRequestHeaderModifier,
+			RequestHeaderModifier: &gatewayv1.HTTPHeaderFilter{
+				Set: []gatewayv1.HTTPHeader{},
+			},
+		}
+		httpRoute.Spec.Rules[ruleIndex].Filters = append(httpRoute.Spec.Rules[ruleIndex].Filters, f)
+		// Get pointer to the newly added filter
+		filter = &httpRoute.Spec.Rules[ruleIndex].Filters[len(httpRoute.Spec.Rules[ruleIndex].Filters)-1]
+	}
+
+	for name, value := range headersToSet {
+		// Check if header is already being set to avoid duplicates?
+		// Simply append for now, or check existence.
+		exists := false
+		for _, h := range filter.RequestHeaderModifier.Set {
+			if string(h.Name) == name {
+				exists = true
+				break
+			}
+		}
+		if !exists {
+			filter.RequestHeaderModifier.Set = append(filter.RequestHeaderModifier.Set, gatewayv1.HTTPHeader{
+				Name:  gatewayv1.HTTPHeaderName(name),
+				Value: value,
+			})
+			notify(notifications.InfoNotification, fmt.Sprintf("Applied header modifier %s: %s to rule %d of route %s/%s", name, value, ruleIndex, httpRoute.Namespace, httpRoute.Name), httpRoute)
+		}
+	}
+}