Allow disable outbound snat when Azure standard load balancer is used

pkg/cloudprovider/providers/azure/azure.go

@@ -73,6 +73,8 @@ const (
 var (
 	// Master nodes are not added to standard load balancer by default.
 	defaultExcludeMasterFromStandardLB = true
+	// Outbound SNAT is enabled by default.
+	defaultDisableOutboundSNAT = false
 )
 
 // Config holds the configuration parsed from the --cloud-config flag
@@ -145,6 +147,9 @@ type Config struct {
 	// ExcludeMasterFromStandardLB excludes master nodes from standard load balancer.
 	// If not set, it will be default to true.
 	ExcludeMasterFromStandardLB *bool `json:"excludeMasterFromStandardLB" yaml:"excludeMasterFromStandardLB"`
+	// DisableOutboundSNAT disables the outbound SNAT for public load balancer rules.
+	// It should only be set when loadBalancerSku is standard. If not set, it will be default to false.
+	DisableOutboundSNAT *bool `json:"disableOutboundSNAT" yaml:"disableOutboundSNAT"`
 
 	// Maximum allowed LoadBalancer Rule Count is the limit enforced by Azure Load balancer
 	MaximumLoadBalancerRuleCount int `json:"maximumLoadBalancerRuleCount" yaml:"maximumLoadBalancerRuleCount"`
@@ -321,9 +326,20 @@ func NewCloud(configReader io.Reader) (cloudprovider.Interface, error) {
 		config.CloudProviderBackoffDuration = backoffDurationDefault
 	}
 
-	// Do not add master nodes to standard LB by default.
-	if config.ExcludeMasterFromStandardLB == nil {
-		config.ExcludeMasterFromStandardLB = &defaultExcludeMasterFromStandardLB
+	if strings.EqualFold(config.LoadBalancerSku, loadBalancerSkuStandard) {
+		// Do not add master nodes to standard LB by default.
+		if config.ExcludeMasterFromStandardLB == nil {
+			config.ExcludeMasterFromStandardLB = &defaultExcludeMasterFromStandardLB
+		}
+
+		// Enable outbound SNAT by default.
+		if config.DisableOutboundSNAT == nil {
+			config.DisableOutboundSNAT = &defaultDisableOutboundSNAT
+		}
+	} else {
+		if config.DisableOutboundSNAT != nil && *config.DisableOutboundSNAT {
+			return nil, fmt.Errorf("disableOutboundSNAT should only set when loadBalancerSku is standard")
+		}
 	}
 
 	azClientConfig := &azClientConfig{

pkg/cloudprovider/providers/azure/azure_loadbalancer.go

@@ -959,10 +959,11 @@ func (az *Cloud) reconcileLoadBalancerRule(
 					BackendAddressPool: &network.SubResource{
 						ID: to.StringPtr(lbBackendPoolID),
 					},
-					LoadDistribution: loadDistribution,
-					FrontendPort:     to.Int32Ptr(port.Port),
-					BackendPort:      to.Int32Ptr(port.Port),
-					EnableFloatingIP: to.BoolPtr(true),
+					LoadDistribution:    loadDistribution,
+					FrontendPort:        to.Int32Ptr(port.Port),
+					BackendPort:         to.Int32Ptr(port.Port),
+					EnableFloatingIP:    to.BoolPtr(true),
+					DisableOutboundSnat: to.BoolPtr(az.disableLoadBalancerOutboundSNAT()),
 				},
 			}
 			if protocol == v1.ProtocolTCP {

pkg/cloudprovider/providers/azure/azure_wrap.go

@@ -300,6 +300,14 @@ func (az *Cloud) excludeMasterNodesFromStandardLB() bool {
 	return az.ExcludeMasterFromStandardLB != nil && *az.ExcludeMasterFromStandardLB
 }
 
+func (az *Cloud) disableLoadBalancerOutboundSNAT() bool {
+	if !az.useStandardLoadBalancer() || az.DisableOutboundSNAT == nil {
+		return false
+	}
+
+	return *az.DisableOutboundSNAT
+}
+
 // IsNodeUnmanaged returns true if the node is not managed by Azure cloud provider.
 // Those nodes includes on-prem or VMs from other clouds. They will not be added to load balancer
 // backends. Azure routes and managed disks are also not supported for them.