macvlan: make master config as optional

To ease of config, make master config as optional parameter.
In default case, default route interface will be used for master.

plugins/main/macvlan/README.md

@@ -23,7 +23,7 @@ Since each macvlan interface has its own MAC address, it makes it easy to use wi
 
 * `name` (string, required): the name of the network
 * `type` (string, required): "macvlan"
-* `master` (string, required): name of the host interface to enslave
+* `master` (string, optional): name of the host interface to enslave. Defaults to default route interace.
 * `mode` (string, optional): one of "bridge", "private", "vepa", "passthru". Defaults to "bridge".
 * `mtu` (integer, optional): explicitly set MTU to the specified value. Defaults to the value chosen by the kernel.
 * `ipam` (dictionary, required): IPAM configuration to be used for this network.

plugins/main/macvlan/macvlan.go

@@ -51,13 +51,33 @@ func init() {
 	runtime.LockOSThread()
 }
 
+func getDefaultRouteInterfaceName() string {
+	routeToDstIP, err := netlink.RouteList(nil, netlink.FAMILY_ALL)
+	if err != nil {
+		return ""
+	}
+
+	for _, v := range routeToDstIP {
+		l, _ := netlink.LinkByIndex(v.LinkIndex)
+		if v.Dst == nil {
+			return l.Attrs().Name
+		}
+	}
+
+	return ""
+}
+
 func loadConf(bytes []byte) (*NetConf, string, error) {
 	n := &NetConf{}
 	if err := json.Unmarshal(bytes, n); err != nil {
 		return nil, "", fmt.Errorf("failed to load netconf: %v", err)
 	}
 	if n.Master == "" {
-		return nil, "", fmt.Errorf(`"master" field is required. It specifies the host interface name to virtualize`)
+		defaultRouteInterface := getDefaultRouteInterfaceName()
+		if defaultRouteInterface == "" {
+			return nil, "", fmt.Errorf(`cannot get default route interface for master`)
+		}
+		n.Master = defaultRouteInterface
 	}
 	return n, n.CNIVersion, nil
 }

plugins/main/macvlan/macvlan_test.go

@@ -399,4 +399,115 @@ var _ = Describe("macvlan Operations", func() {
 		})
 		Expect(err).NotTo(HaveOccurred())
 	})
+
+	It("configures and deconfigures a macvlan link with ADD/DEL, without master config", func() {
+		const IFNAME = "macvl0"
+
+		conf := `{
+    "cniVersion": "0.3.1",
+    "name": "mynet",
+    "type": "macvlan",
+    "ipam": {
+        "type": "host-local",
+        "subnet": "10.1.2.0/24"
+    }
+}`
+
+		targetNs, err := testutils.NewNS()
+		Expect(err).NotTo(HaveOccurred())
+		defer targetNs.Close()
+
+		args := &skel.CmdArgs{
+			ContainerID: "dummy",
+			Netns:       targetNs.Path(),
+			IfName:      IFNAME,
+			StdinData:   []byte(conf),
+		}
+
+		// Make MASTER_NAME as default route interface
+		err = originalNS.Do(func(ns.NetNS) error {
+			defer GinkgoRecover()
+
+			link, err := netlink.LinkByName(MASTER_NAME)
+			Expect(err).NotTo(HaveOccurred())
+			err = netlink.LinkSetUp(link)
+			Expect(err).NotTo(HaveOccurred())
+
+			var address = &net.IPNet{IP: net.IPv4(192, 0, 0, 1), Mask: net.CIDRMask(24, 32)}
+			var addr = &netlink.Addr{IPNet: address}
+			err = netlink.AddrAdd(link, addr)
+			Expect(err).NotTo(HaveOccurred())
+
+			// add default gateway into MASTER
+			dst := &net.IPNet{
+				IP:   net.IPv4(0, 0, 0, 0),
+				Mask: net.CIDRMask(0, 0),
+			}
+			ip := net.IPv4(192, 0, 0, 254)
+			route := netlink.Route{LinkIndex: link.Attrs().Index, Dst: dst, Gw: ip}
+			err = netlink.RouteAdd(&route)
+			Expect(err).NotTo(HaveOccurred())
+			return nil
+		})
+		Expect(err).NotTo(HaveOccurred())
+
+		var result *current.Result
+		err = originalNS.Do(func(ns.NetNS) error {
+			r, _, err := testutils.CmdAddWithArgs(args, func() error {
+				return cmdAdd(args)
+			})
+			Expect(err).NotTo(HaveOccurred())
+
+			result, err = current.GetResult(r)
+			Expect(err).NotTo(HaveOccurred())
+
+			Expect(len(result.Interfaces)).To(Equal(1))
+			Expect(result.Interfaces[0].Name).To(Equal(IFNAME))
+			Expect(len(result.IPs)).To(Equal(1))
+			return nil
+		})
+		Expect(err).NotTo(HaveOccurred())
+
+		// Make sure macvlan link exists in the target namespace
+		err = targetNs.Do(func(ns.NetNS) error {
+			defer GinkgoRecover()
+
+			link, err := netlink.LinkByName(IFNAME)
+			Expect(err).NotTo(HaveOccurred())
+			Expect(link.Attrs().Name).To(Equal(IFNAME))
+
+			hwaddr, err := net.ParseMAC(result.Interfaces[0].Mac)
+			Expect(err).NotTo(HaveOccurred())
+			Expect(link.Attrs().HardwareAddr).To(Equal(hwaddr))
+
+			addrs, err := netlink.AddrList(link, syscall.AF_INET)
+			Expect(err).NotTo(HaveOccurred())
+			Expect(len(addrs)).To(Equal(1))
+			return nil
+		})
+		Expect(err).NotTo(HaveOccurred())
+
+		err = originalNS.Do(func(ns.NetNS) error {
+			defer GinkgoRecover()
+
+			err := testutils.CmdDelWithArgs(args, func() error {
+				return cmdDel(args)
+			})
+			Expect(err).NotTo(HaveOccurred())
+			return nil
+		})
+		Expect(err).NotTo(HaveOccurred())
+
+		// Make sure macvlan link has been deleted
+		err = targetNs.Do(func(ns.NetNS) error {
+			defer GinkgoRecover()
+
+			link, err := netlink.LinkByName(IFNAME)
+			Expect(err).To(HaveOccurred())
+			Expect(link).To(BeNil())
+			return nil
+		})
+		Expect(err).NotTo(HaveOccurred())
+	})
+
 })