Fix: Add default route on delegatedNIC interface (#3109)

* add default route on delegatedNIC interface

* remove logger import

* fix linter issue

* fix comments

* format codes

* gofumpt file

* enhance comment

* Update cns/middlewares/k8sSwiftV2_linux.go

Co-authored-by: Evan Baker <[email protected]>
Signed-off-by: Paul Yu <[email protected]>

---------

Signed-off-by: Paul Yu <[email protected]>
Co-authored-by: Evan Baker <[email protected]>

Author: paulyufan2

cns/middlewares/k8sSwiftV2.go

@@ -237,6 +237,8 @@ func (k *K8sSWIFTv2Middleware) getIPConfig(ctx context.Context, podInfo cns.PodI
 					return nil, errors.Wrap(err, "failed to parse mtpnc subnetAddressSpace prefix")
 				}
 				podIPInfos = append(podIPInfos, podIPInfo)
+				// for windows scenario, it is required to add default route with gatewayIP from CNS
+				k.addDefaultRoute(&podIPInfo, interfaceInfo.GatewayIP)
 			}
 		}
 	}

cns/middlewares/k8sSwiftV2_linux.go

@@ -101,3 +101,5 @@ func addRoutes(cidrs []string, gatewayIP string) []cns.Route {
 func (k *K8sSWIFTv2Middleware) assignSubnetPrefixLengthFields(_ *cns.PodIpInfo, _ v1alpha1.InterfaceInfo, _ string) error {
 	return nil
 }
+
+func (k *K8sSWIFTv2Middleware) addDefaultRoute(*cns.PodIpInfo, string) {}

cns/middlewares/k8sSwiftV2_windows.go

@@ -2,7 +2,6 @@ package middlewares
 
 import (
 	"github.com/Azure/azure-container-networking/cns"
-	"github.com/Azure/azure-container-networking/cns/logger"
 	"github.com/Azure/azure-container-networking/cns/middlewares/utils"
 	"github.com/Azure/azure-container-networking/crd/multitenancy/api/v1alpha1"
 	"github.com/pkg/errors"
@@ -12,7 +11,15 @@ import (
 // default route is set for secondary interface NIC(i.e,delegatedNIC)
 func (k *K8sSWIFTv2Middleware) setRoutes(podIPInfo *cns.PodIpInfo) error {
 	if podIPInfo.NICType == cns.InfraNIC {
-		logger.Printf("[SWIFTv2Middleware] skip setting default route on InfraNIC interface")
+		// as a workaround, HNS will not set this dummy default route(0.0.0.0/0, nexthop:0.0.0.0) on infraVnet interface eth0
+		// the only usage for this dummy default is to bypass HNS setting default route on eth0
+		// TODO: Remove this once HNS fix is ready
+		route := cns.Route{
+			IPAddress:        "0.0.0.0/0",
+			GatewayIPAddress: "0.0.0.0",
+		}
+		podIPInfo.Routes = append(podIPInfo.Routes, route)
+
 		podIPInfo.SkipDefaultRoutes = true
 	}
 	return nil
@@ -42,3 +49,12 @@ func (k *K8sSWIFTv2Middleware) assignSubnetPrefixLengthFields(podIPInfo *cns.Pod
 	}
 	return nil
 }
+
+// add default route with gateway IP to podIPInfo
+func (k *K8sSWIFTv2Middleware) addDefaultRoute(podIPInfo *cns.PodIpInfo, gwIP string) {
+	route := cns.Route{
+		IPAddress:        "0.0.0.0/0",
+		GatewayIPAddress: gwIP,
+	}
+	podIPInfo.Routes = append(podIPInfo.Routes, route)
+}

cns/middlewares/k8sSwiftV2_windows_test.go

@@ -1,6 +1,7 @@
 package middlewares
 
 import (
+	"reflect"
 	"testing"
 
 	"github.com/Azure/azure-container-networking/cns"
@@ -66,3 +67,36 @@ func TestAssignSubnetPrefixSuccess(t *testing.T) {
 	assert.Equal(t, ipInfo.HostPrimaryIPInfo.Gateway, intInfo.GatewayIP)
 	assert.Equal(t, ipInfo.HostPrimaryIPInfo.Subnet, intInfo.SubnetAddressSpace)
 }
+
+func TestAddDefaultRoute(t *testing.T) {
+	middleware := K8sSWIFTv2Middleware{Cli: mock.NewClient()}
+
+	podIPInfo := cns.PodIpInfo{
+		PodIPConfig: cns.IPSubnet{
+			IPAddress:    "20.240.1.242",
+			PrefixLength: 32,
+		},
+		NICType:    cns.DelegatedVMNIC,
+		MacAddress: "12:34:56:78:9a:bc",
+	}
+
+	gatewayIP := "20.240.1.1"
+	intInfo := v1alpha1.InterfaceInfo{
+		GatewayIP:          gatewayIP,
+		SubnetAddressSpace: "20.240.1.0/16",
+	}
+
+	ipInfo := podIPInfo
+	middleware.addDefaultRoute(&ipInfo, intInfo.GatewayIP)
+
+	expectedRoutes := []cns.Route{
+		{
+			IPAddress:        "0.0.0.0/0",
+			GatewayIPAddress: gatewayIP,
+		},
+	}
+
+	if !reflect.DeepEqual(ipInfo.Routes, expectedRoutes) {
+		t.Errorf("got '%+v', expected '%+v'", ipInfo.Routes, expectedRoutes)
+	}
+}