macvlan: Assign random MAC address

Macvtap interfaces require mac addresses to be unique even
though they may be in a separate namespace. Hence use a randomly
generate MAC address.

Signed-off-by: Archana Shinde <[email protected]>

virtcontainers/network.go

@@ -6,6 +6,7 @@
 package virtcontainers
 
 import (
+	cryptoRand "crypto/rand"
 	"encoding/hex"
 	"encoding/json"
 	"fmt"
@@ -1345,7 +1346,10 @@ func createVirtualNetworkEndpoint(idx int, ifName string, interworkingModel NetI
 		return &VirtualEndpoint{}, fmt.Errorf("invalid network endpoint index: %d", idx)
 	}
 
-	netPair := createNetworkInterfacePair(idx, ifName, interworkingModel)
+	netPair, err := createNetworkInterfacePair(idx, ifName, interworkingModel)
+	if err != nil {
+		return nil, err
+	}
 
 	endpoint := &VirtualEndpoint{
 		// TODO This is too specific. We may need to create multiple
@@ -1366,7 +1370,10 @@ func createBridgedMacvlanNetworkEndpoint(idx int, ifName string, interworkingMod
 		return &BridgedMacvlanEndpoint{}, fmt.Errorf("invalid network endpoint index: %d", idx)
 	}
 
-	netPair := createNetworkInterfacePair(idx, ifName, interworkingModel)
+	netPair, err := createNetworkInterfacePair(idx, ifName, interworkingModel)
+	if err != nil {
+		return nil, err
+	}
 
 	endpoint := &BridgedMacvlanEndpoint{
 		NetPair:      netPair,
@@ -1466,26 +1473,44 @@ func generateInterfacesAndRoutes(networkNS NetworkNamespace) ([]*grpc.Interface,
 	return ifaces, routes, nil
 }
 
-func createNetworkInterfacePair(idx int, ifName string, interworkingModel NetInterworkingModel) NetworkInterfacePair {
+func createNetworkInterfacePair(idx int, ifName string, interworkingModel NetInterworkingModel) (NetworkInterfacePair, error) {
 	uniqueID := uuid.Generate().String()
 
-	hardAddr := net.HardwareAddr{0x02, 0x00, 0xCA, 0xFE, byte(idx >> 8), byte(idx)}
+	randomMacAddr, err := generateRandomPrivateMacAddr()
+	if err != nil {
+		return NetworkInterfacePair{}, fmt.Errorf("Could not generate random mac address: %s", err)
+	}
 
 	netPair := NetworkInterfacePair{
 		ID:   uniqueID,
 		Name: fmt.Sprintf("br%d_kata", idx),
 		VirtIface: NetworkInterface{
 			Name:     fmt.Sprintf("eth%d", idx),
-			HardAddr: hardAddr.String(),
+			HardAddr: randomMacAddr,
 		},
 		TAPIface: NetworkInterface{
 			Name: fmt.Sprintf("tap%d_kata", idx),
 		},
 		NetInterworkingModel: interworkingModel,
 	}
 
-	return netPair
+	return netPair, nil
+}
+
+func generateRandomPrivateMacAddr() (string, error) {
+	buf := make([]byte, 6)
+	_, err := cryptoRand.Read(buf)
+	if err != nil {
+		return "", err
+	}
+
+	// Set the local bit for local addresses
+	// Addresses in this range are local mac addresses:
+	// x2-xx-xx-xx-xx-xx , x6-xx-xx-xx-xx-xx , xA-xx-xx-xx-xx-xx , xE-xx-xx-xx-xx-xx
+	buf[0] = (buf[0] | 2) & 0xfe
 
+	hardAddr := net.HardwareAddr(buf)
+	return hardAddr.String(), nil
 }
 
 func networkInfoFromLink(handle *netlink.Handle, link netlink.Link) (NetworkInfo, error) {

virtcontainers/network_test.go

@@ -230,8 +230,11 @@ func TestCreateVirtualNetworkEndpoint(t *testing.T) {
 	// the resulting ID  will be random - so let's overwrite to test the rest of the flow
 	result.NetPair.ID = "uniqueTestID-4"
 
+	// the resulting mac address will be random - so lets overwrite it
+	result.NetPair.VirtIface.HardAddr = macAddr.String()
+
 	if reflect.DeepEqual(result, expected) == false {
-		t.Fatal()
+		t.Fatalf("\nGot: %+v, \n\nExpected: %+v", result, expected)
 	}
 }
 
@@ -262,8 +265,11 @@ func TestCreateVirtualNetworkEndpointChooseIfaceName(t *testing.T) {
 	// the resulting ID will be random - so let's overwrite to test the rest of the flow
 	result.NetPair.ID = "uniqueTestID-4"
 
+	// the resulting mac address will be random - so lets overwrite it
+	result.NetPair.VirtIface.HardAddr = macAddr.String()
+
 	if reflect.DeepEqual(result, expected) == false {
-		t.Fatal()
+		t.Fatalf("\nGot: %+v, \n\nExpected: %+v", result, expected)
 	}
 }