Ensure correct sysctl values if VLAN iface exists in IPAssigner (#6900)

If the VLAN interface already exixts (e.g., in case of an Agent
restart), we should still ensure that the necessary systcl variables are
set correctly.

Signed-off-by: Antonin Bas <[email protected]>

pkg/agent/ipassigner/ip_assigner_linux.go

@@ -508,6 +508,15 @@ func (a *ipAssigner) getAssignee(subnetInfo *crdv1b1.SubnetInfo, createIfNotExis
 			return nil, fmt.Errorf("error creating VLAN sub-interface for VLAN %d", subnetInfo.VLAN)
 		}
 	}
+	as, err := a.addVLANAssignee(vlan, subnetInfo.VLAN)
+	if err != nil {
+		return nil, err
+	}
+	return as, nil
+}
+
+func (a *ipAssigner) addVLANAssignee(link netlink.Link, vlan int32) (*assignee, error) {
+	name := link.Attrs().Name
 	// Loose mode is needed because incoming traffic received on the interface is expected to be received on the parent
 	// external interface when looking up the main table. To make it look up the custom table, we will need to restore
 	// the mark on the reply traffic and turn on src_valid_mark on this interface, which is more complicated.
@@ -521,18 +530,10 @@ func (a *ipAssigner) getAssignee(subnetInfo *crdv1b1.SubnetInfo, createIfNotExis
 	if err := util.EnsurePromoteSecondariesOnInterface(name); err != nil {
 		return nil, err
 	}
-	as, err := a.addVLANAssignee(vlan, subnetInfo.VLAN)
-	if err != nil {
-		return nil, err
-	}
-	return as, nil
-}
-
-func (a *ipAssigner) addVLANAssignee(link netlink.Link, vlan int32) (*assignee, error) {
 	if err := netlink.LinkSetUp(link); err != nil {
 		return nil, fmt.Errorf("error setting up interface %v", link)
 	}
-	iface, err := net.InterfaceByName(link.Attrs().Name)
+	iface, err := net.InterfaceByName(name)
 	if err != nil {
 		return nil, err
 	}

test/integration/agent/ip_assigner_linux_test.go

@@ -25,11 +25,29 @@ import (
 	"k8s.io/apimachinery/pkg/util/sets"
 
 	"antrea.io/antrea/pkg/agent/ipassigner"
+	"antrea.io/antrea/pkg/agent/util/sysctl"
 	crdv1b1 "antrea.io/antrea/pkg/apis/crd/v1beta1"
 )
 
 const dummyDeviceName = "antrea-dummy0"
 
+func checkSysctl(t *testing.T, path string, expected int) {
+	t.Helper()
+	v, err := sysctl.GetSysctlNet(path)
+	require.NoError(t, err)
+	assert.Equalf(t, expected, v, "Wrong value for %s", path)
+}
+
+func checkRPFilterOnInterface(t *testing.T, ifaceName string, expected int) {
+	t.Helper()
+	checkSysctl(t, fmt.Sprintf("ipv4/conf/%s/rp_filter", ifaceName), expected)
+}
+
+func checkPromoteSecondariesOnInterface(t *testing.T, ifaceName string, expected int) {
+	t.Helper()
+	checkSysctl(t, fmt.Sprintf("ipv4/conf/%s/promote_secondaries", ifaceName), expected)
+}
+
 func TestIPAssigner(t *testing.T) {
 	nodeLinkName := nodeIntf.Name
 	require.NotNil(t, nodeLinkName, "Get Node link failed")
@@ -40,6 +58,7 @@ func TestIPAssigner(t *testing.T) {
 	dummyDevice, err := netlink.LinkByName(dummyDeviceName)
 	require.NoError(t, err, "Failed to find the dummy device")
 	defer netlink.LinkDel(dummyDevice)
+	checkPromoteSecondariesOnInterface(t, dummyDeviceName, 1)
 
 	_, err = ipAssigner.AssignIP("x", nil, false)
 	assert.Error(t, err, "Assigning an invalid IP should fail")
@@ -103,9 +122,13 @@ func TestIPAssigner(t *testing.T) {
 	vlan20Device, err := netlink.LinkByName("antrea-ext.20")
 	require.NoError(t, err, "Failed to find the VLAN 20 device")
 	defer netlink.LinkDel(vlan20Device)
+	checkRPFilterOnInterface(t, "antrea-ext.20", 2)
+	checkPromoteSecondariesOnInterface(t, "antrea-ext.20", 1)
 	vlan30Device, err := netlink.LinkByName("antrea-ext.30")
 	require.NoError(t, err, "Failed to find the VLAN 30 device")
 	defer netlink.LinkDel(vlan30Device)
+	checkRPFilterOnInterface(t, "antrea-ext.30", 2)
+	checkPromoteSecondariesOnInterface(t, "antrea-ext.30", 1)
 
 	actualIPs, err := listIPAddresses(dummyDevice)
 	require.NoError(t, err, "Failed to list IP addresses")