Create skeleton for degraded mode procedure

Create skeleton for degraded mode procedure

pkg/neg/syncers/transaction.go

@@ -242,6 +242,10 @@ func (s *transactionSyncer) syncInternalImpl() error {
 			endpointSlices[i] = slice.(*discovery.EndpointSlice)
 		}
 		if s.inErrorState() {
+			targetMap, endpointPodMap, err = s.computeTargetMapInDegradedMode(endpointSlices)
+			if err != nil {
+				return err
+			}
 			s.resetErrorState()
 		} else {
 			targetMap, endpointPodMap, err = s.computeTargetMap(endpointSlices)
@@ -314,6 +318,47 @@ func (s *transactionSyncer) computeTargetMap(endpointSlices []*discovery.Endpoin
 	return targetMap, endpointPodMap, err
 }
 
+// degradedMode does endpoint calculation differently to fix the error in NEG controller
+func (s *transactionSyncer) computeTargetMapInDegradedMode(slices []*discovery.EndpointSlice) (map[string]negtypes.NetworkEndpointSet, negtypes.EndpointPodMap, error) {
+	var targetMap map[string]negtypes.NetworkEndpointSet
+	var endpointPodMap negtypes.EndpointPodMap
+	var err error
+
+	for _, slice := range slices {
+		// if it is a custom endpoint slice, don't include it
+		// so it won't block the neg api call from succeeding
+		if val, ok := slice.ObjectMeta.Labels[discovery.LabelManagedBy]; !ok || val != "endpointslice-controller.k8s.io" {
+			continue
+		}
+
+		for _, ep := range slice.Endpoints {
+			if ep.TargetRef == nil {
+				continue
+			}
+			networkEndpoint, valid := s.validateEndpoint(ep)
+			if valid {
+				zone, err := s.zoneGetter.GetZoneForNode(networkEndpoint.Node)
+				if err != nil {
+					continue
+				}
+				if targetMap[zone] == nil {
+					targetMap[zone] = negtypes.NewNetworkEndpointSet()
+				}
+				targetMap[zone].Insert(networkEndpoint)
+				endpointPodMap[networkEndpoint] = types.NamespacedName{Namespace: ep.TargetRef.Namespace, Name: ep.TargetRef.Name}
+			}
+		}
+	}
+	return targetMap, endpointPodMap, err
+}
+
+// validateEndpoint fill in endpoint's nodeName if missing,
+// validate it against the nodeName from the pod
+// and determine whether it should be kept based on the pod
+func (s *transactionSyncer) validateEndpoint(ep discovery.Endpoint) (negtypes.NetworkEndpoint, bool) {
+	return negtypes.NetworkEndpoint{}, true
+}
+
 // syncLock must already be acquired before execution
 func (s *transactionSyncer) inErrorState() bool {
 	return s.inError