Rfrain from adding Egress IP to public LB backend pool

This PR is to stop adding Egress IP to public load balancer
backend pool regardless of presence of an OutBoundRule in any
Azure cluster.

This change comes with a consequence of no outbound connectivity
except to the infrastructure subnet even if there is no OutBoundRule.

However this is required to tackle following situation:

- If an infra node is being used as an egressNode then health
check for egress IP also succeeds when it is added to public load
balancer and LB considers it as a legitimate ingress router backend.

- Limits the number of egress IP which can be created on a cluster
due to some Azure specific limitation.

Signed-off-by: Arnab Ghosh <[email protected]>

Author: arghosh93

pkg/cloudprovider/azure.go

@@ -48,7 +48,6 @@ type Azure struct {
 	vmClient                     *armcompute.VirtualMachinesClient
 	virtualNetworkClient         *armnetwork.VirtualNetworksClient
 	networkClient                *armnetwork.InterfacesClient
-	backendAddressPoolClient     *armnetwork.LoadBalancerBackendAddressPoolsClient
 	nodeMapLock                  sync.Mutex
 	nodeLockMap                  map[string]*sync.Mutex
 	azureWorkloadIdentityEnabled bool
@@ -162,11 +161,6 @@ func (a *Azure) initCredentials() error {
 		return fmt.Errorf("failed to initialize new VirtualNetworksClient: %w", err)
 	}
 
-	a.backendAddressPoolClient, err = armnetwork.NewLoadBalancerBackendAddressPoolsClient(cfg.subscriptionID, cred, options)
-	if err != nil {
-		return fmt.Errorf("failed to initialize new LoadBalancerBackendAddressPoolsClient: %w", err)
-	}
-
 	return nil
 }
 
@@ -198,65 +192,14 @@ func (a *Azure) AssignPrivateIP(ip net.IP, node *corev1.Node) error {
 	name := fmt.Sprintf("%s_%s", node.Name, ipc)
 	untrue := false
 
-	// In some Azure setups (Azure private, public ARO, private ARO) outbound connectivity is achieved through
-	// outbound rules tied to the backend address pool of the primary IP of the VM NIC. An Azure constraint
-	// forbids the creation of a secondary IP tied to such address pool and would result in
-	// OutboundRuleCannotBeUsedWithBackendAddressPoolThatIsReferencedBySecondaryIpConfigs.
-	// Work around it by not specifying the backend address pool when an outbound rule is set, even though
-	// that means preventing outbound connectivity to the egress IP, which will be able to reach the
-	// infrastructure subnet nonetheless. In public Azure clusters, outbound connectivity is achieved through
-	// UserDefinedRouting, which doesn't impose such constraints on secondary IPs.
-	loadBalancerBackendAddressPoolsArgument := networkInterface.Properties.IPConfigurations[0].Properties.LoadBalancerBackendAddressPools
-	var attachedOutboundRule *armnetwork.SubResource
-OuterLoop:
-	for _, ipconfig := range networkInterface.Properties.IPConfigurations {
-		if ipconfig.Properties.LoadBalancerBackendAddressPools != nil {
-			for _, pool := range ipconfig.Properties.LoadBalancerBackendAddressPools {
-				if pool.ID == nil {
-					continue
-				}
-				// for some reason, the struct for the pool above is not entirely filled out:
-				//     BackendAddressPoolPropertiesFormat:(*network.BackendAddressPoolPropertiesFormat)(nil)
-				// Do a separate get for this pool in order to check whether there are any outbound rules
-				// attached to it
-				realPool, err := a.getBackendAddressPool(ptr.Deref(pool.ID, ""))
-				if err != nil {
-					return fmt.Errorf("error looking up backend address pool %s with ID %s: %v", ptr.Deref(pool.Name, ""), ptr.Deref(pool.ID, ""), err)
-				}
-				if len(realPool.Properties.LoadBalancerBackendAddresses) > 0 {
-					if realPool.Properties.OutboundRule != nil {
-						loadBalancerBackendAddressPoolsArgument = nil
-						attachedOutboundRule = realPool.Properties.OutboundRule
-						break OuterLoop
-					}
-					if len(realPool.Properties.OutboundRules) > 0 {
-						loadBalancerBackendAddressPoolsArgument = nil
-						attachedOutboundRule = (realPool.Properties.OutboundRules)[0]
-						break OuterLoop
-					}
-				}
-			}
-		}
-	}
-	if loadBalancerBackendAddressPoolsArgument == nil {
-		outboundRuleStr := ""
-		if attachedOutboundRule != nil && attachedOutboundRule.ID != nil {
-			// https://issues.redhat.com/browse/OCPBUGS-33617 showed that there can be a rule without an ID...
-			outboundRuleStr = fmt.Sprintf(": %s", ptr.Deref(attachedOutboundRule.ID, ""))
-		}
-		klog.Warningf("Egress IP %s will have no outbound connectivity except for the infrastructure subnet: "+
-			"omitting backend address pool when adding secondary IP: it has an outbound rule already%s",
-			ipc, outboundRuleStr)
-	}
 	newIPConfiguration := &armnetwork.InterfaceIPConfiguration{
 		Name: &name,
 		Properties: &armnetwork.InterfaceIPConfigurationPropertiesFormat{
-			PrivateIPAddress:                &ipc,
-			PrivateIPAllocationMethod:       ptr.To(armnetwork.IPAllocationMethodStatic),
-			Subnet:                          networkInterface.Properties.IPConfigurations[0].Properties.Subnet,
-			Primary:                         &untrue,
-			LoadBalancerBackendAddressPools: loadBalancerBackendAddressPoolsArgument,
-			ApplicationSecurityGroups:       applicationSecurityGroups,
+			PrivateIPAddress:          &ipc,
+			PrivateIPAllocationMethod: ptr.To(armnetwork.IPAllocationMethodStatic),
+			Subnet:                    networkInterface.Properties.IPConfigurations[0].Properties.Subnet,
+			Primary:                   &untrue,
+			ApplicationSecurityGroups: applicationSecurityGroups,
 		},
 	}
 	for _, ipCfg := range ipConfigurations {
@@ -272,6 +215,8 @@ OuterLoop:
 	ipConfigurations = append(ipConfigurations, newIPConfiguration)
 	networkInterface.Properties.IPConfigurations = ipConfigurations
 	// Send the request
+	klog.Warningf("Egress IP %s will have no outbound connectivity except for the infrastructure subnet: "+
+		"omitting backend address pool when adding secondary IP", ipc)
 	poller, err := a.createOrUpdate(networkInterface)
 	if err != nil {
 		return err
@@ -491,46 +436,6 @@ func (a *Azure) getNetworkInterfaces(instance *armcompute.VirtualMachine) ([]arm
 	return networkInterfaces, nil
 }
 
-func splitObjectID(azureResourceID string) (resourceGroupName, loadBalancerName, backendAddressPoolName string) {
-	// example of an azureResourceID:
-	// "/subscriptions/53b8f551-f0fc-4bea-8cba-6d1fefd54c8a/resourceGroups/huirwang-debug1-2qh9t-rg/providers/Microsoft.Network/loadBalancers/huirwang-debug1-2qh9t/backendAddressPools/huirwang-debug1-2qh9t"
-
-	// Split the Azure resource ID into parts using "/"
-	parts := strings.Split(azureResourceID, "/")
-
-	// Iterate through the parts to find the relevant subIDs
-	for i, part := range parts {
-		switch part {
-		case "resourceGroups":
-			if i+1 < len(parts) {
-				resourceGroupName = parts[i+1]
-			}
-		case "loadBalancers":
-			if i+1 < len(parts) {
-				loadBalancerName = parts[i+1]
-			}
-		case "backendAddressPools":
-			if i+1 < len(parts) {
-				backendAddressPoolName = parts[i+1]
-			}
-		}
-	}
-	return
-}
-
-func (a *Azure) getBackendAddressPool(poolID string) (*armnetwork.BackendAddressPool, error) {
-	ctx, cancel := context.WithTimeout(a.ctx, defaultAzureOperationTimeout)
-	defer cancel()
-	resourceGroupName, loadBalancerName, backendAddressPoolName := splitObjectID(poolID)
-	response, err := a.backendAddressPoolClient.Get(ctx, resourceGroupName, loadBalancerName, backendAddressPoolName, nil)
-	if err != nil {
-		return nil, fmt.Errorf("failed to retrieve backend address pool for backendAddressPoolClient=%s, loadBalancerName=%s, backendAddressPoolName=%s: %w",
-			resourceGroupName, loadBalancerName, backendAddressPoolName, err)
-	}
-	return &response.BackendAddressPool, nil
-
-}
-
 func (a *Azure) getNetworkInterface(id string) (armnetwork.Interface, error) {
 	ctx, cancel := context.WithTimeout(a.ctx, defaultAzureOperationTimeout)
 	defer cancel()