align getting iptables legacy with iptables

Author: QxBytes

cns/restserver/internalapi_linux.go

@@ -23,8 +23,8 @@ func (c *IPtablesProvider) GetIPTables() (iptablesClient, error) {
 	client, err := goiptables.New()
 	return client, errors.Wrap(err, "failed to get iptables client")
 }
-func (c *IPtablesProvider) GetIPTablesLegacy() iptablesLegacyClient {
-	return &iptablesLegacy{}
+func (c *IPtablesProvider) GetIPTablesLegacy() (iptablesLegacyClient, error) {
+	return &iptablesLegacy{}, nil
 }
 
 type iptablesLegacy struct{}
@@ -43,8 +43,12 @@ func (service *HTTPRestService) programSNATRules(req *cns.CreateNetworkContainer
 	// in podsubnet case, ncPrimaryIP is the pod subnet's primary ip
 	// in vnet scale case, ncPrimaryIP is the node's ip
 	ncPrimaryIP, _, _ := net.ParseCIDR(req.IPConfiguration.IPSubnet.IPAddress + "/" + fmt.Sprintf("%d", req.IPConfiguration.IPSubnet.PrefixLength))
-	iptl := service.iptables.GetIPTablesLegacy()
-	err := iptl.Delete(iptables.Nat, iptables.Postrouting, "-j", SWIFTPOSTROUTING)
+
+	iptl, err := service.iptables.GetIPTablesLegacy()
+	if err != nil {
+		return types.UnexpectedError, fmt.Sprintf("[Azure CNS] Error. Failed to create iptables legacy interface : %v", err)
+	}
+	err = iptl.Delete(iptables.Nat, iptables.Postrouting, "-j", SWIFTPOSTROUTING)
 	// ignore if command fails
 	if err == nil {
 		logger.Printf("[Azure CNS] Deleted legacy jump to SWIFT-POSTROUTING Chain")

cns/restserver/internalapi_linux_test.go

@@ -27,11 +27,11 @@ func (c *FakeIPTablesProvider) GetIPTables() (iptablesClient, error) {
 	return c.iptables, nil
 }
 
-func (c *FakeIPTablesProvider) GetIPTablesLegacy() iptablesLegacyClient {
+func (c *FakeIPTablesProvider) GetIPTablesLegacy() (iptablesLegacyClient, error) {
 	if c.iptablesLegacy == nil {
 		c.iptablesLegacy = &fakes.IPTablesLegacyMock{}
 	}
-	return c.iptablesLegacy
+	return c.iptablesLegacy, nil
 }
 
 func TestAddSNATRules(t *testing.T) {

cns/restserver/restserver.go

@@ -70,7 +70,7 @@ type iptablesLegacyClient interface {
 
 type iptablesGetter interface {
 	GetIPTables() (iptablesClient, error)
-	GetIPTablesLegacy() iptablesLegacyClient
+	GetIPTablesLegacy() (iptablesLegacyClient, error)
 }
 
 // HTTPRestService represents http listener for CNS - Container Networking Service.