macvlan: set mac address from CNI_ARGS

This change sets the mac address if specified during the creation of the
macvlan interface. This is superior to setting it via the tuning plugin
because this ensures the mac address is set before an IP is set,
allowing a container to get a reserved IP address from DHCP.

Related containernetworking#450

plugins/main/macvlan/macvlan.go

@@ -45,6 +45,13 @@ type NetConf struct {
 	Master string `json:"master"`
 	Mode   string `json:"mode"`
 	MTU    int    `json:"mtu"`
+	Mac    string `json:"mac,omitempty"`
+}
+
+// MacEnvArgs represents CNI_ARG
+type MacEnvArgs struct {
+	types.CommonArgs
+	MAC types.UnmarshallableString `json:"mac,omitempty"`
 }
 
 func init() {
@@ -73,7 +80,7 @@ func getDefaultRouteInterfaceName() (string, error) {
 	return "", fmt.Errorf("no default route interface found")
 }
 
-func loadConf(bytes []byte) (*NetConf, string, error) {
+func loadConf(bytes []byte, envArgs string) (*NetConf, string, error) {
 	n := &NetConf{}
 	if err := json.Unmarshal(bytes, n); err != nil {
 		return nil, "", fmt.Errorf("failed to load netconf: %v", err)
@@ -95,6 +102,18 @@ func loadConf(bytes []byte) (*NetConf, string, error) {
 		return nil, "", fmt.Errorf("invalid MTU %d, must be [0, master MTU(%d)]", n.MTU, masterMTU)
 	}
 
+	if envArgs != "" {
+		e := MacEnvArgs{}
+		err := types.LoadArgs(envArgs, &e)
+		if err != nil {
+			return nil, "", err
+		}
+
+		if e.MAC != "" {
+			n.Mac = string(e.MAC)
+		}
+	}
+
 	return n, n.CNIVersion, nil
 }
 
@@ -156,14 +175,24 @@ func createMacvlan(conf *NetConf, ifName string, netns ns.NetNS) (*current.Inter
 		return nil, err
 	}
 
+	linkAttrs := netlink.LinkAttrs{
+		MTU:         conf.MTU,
+		Name:        tmpName,
+		ParentIndex: m.Attrs().Index,
+		Namespace:   netlink.NsFd(int(netns.Fd())),
+	}
+
+	if conf.Mac != "" {
+		addr, err := net.ParseMAC(conf.Mac)
+		if err != nil {
+			return nil, fmt.Errorf("invalid args %v for MAC addr: %v", conf.Mac, err)
+		}
+		linkAttrs.HardwareAddr = addr
+	}
+
 	mv := &netlink.Macvlan{
-		LinkAttrs: netlink.LinkAttrs{
-			MTU:         conf.MTU,
-			Name:        tmpName,
-			ParentIndex: m.Attrs().Index,
-			Namespace:   netlink.NsFd(int(netns.Fd())),
-		},
-		Mode: mode,
+		LinkAttrs: linkAttrs,
+		Mode:      mode,
 	}
 
 	if err := netlink.LinkAdd(mv); err != nil {
@@ -204,7 +233,7 @@ func createMacvlan(conf *NetConf, ifName string, netns ns.NetNS) (*current.Inter
 }
 
 func cmdAdd(args *skel.CmdArgs) error {
-	n, cniVersion, err := loadConf(args.StdinData)
+	n, cniVersion, err := loadConf(args.StdinData, args.Args)
 	if err != nil {
 		return err
 	}
@@ -311,7 +340,7 @@ func cmdAdd(args *skel.CmdArgs) error {
 }
 
 func cmdDel(args *skel.CmdArgs) error {
-	n, _, err := loadConf(args.StdinData)
+	n, _, err := loadConf(args.StdinData, args.Args)
 	if err != nil {
 		return err
 	}
@@ -349,7 +378,7 @@ func main() {
 
 func cmdCheck(args *skel.CmdArgs) error {
 
-	n, _, err := loadConf(args.StdinData)
+	n, _, err := loadConf(args.StdinData, args.Args)
 	if err != nil {
 		return err
 	}