// GC enters the pod by fork/exec()ing the stage1's /gc similar to /init.
// /gc can expect to have its CWD set to the pod root.
// stage1Path is the path of the stage1 rootfs
func GC(pdir string, uuid *types.UUID, stage1Path string, debug bool) error {
	err := unregisterPod(pdir, uuid)
	if err != nil {
		// Probably not worth abandoning the rest
		log.Printf("Warning: could not unregister pod with metadata service: %v", err)
	}

	ep, err := getStage1Entrypoint(pdir, gcEntrypoint)
	if err != nil {
		return fmt.Errorf("error determining gc entrypoint: %v", err)
	}

	args := []string{filepath.Join(stage1Path, ep)}
	if debug {
		args = append(args, "--debug")
	}
	args = append(args, uuid.String())

	c := exec.Cmd{
		Path:   args[0],
		Args:   args,
		Stderr: os.Stderr,
		Dir:    pdir,
	}
	return c.Run()
}

// registerPod registers pod with metadata service.
// Returns authentication token to be passed in the URL
func registerPod(root string, uuid *types.UUID, apps schema.AppList) (token string, rerr error) {
	u := uuid.String()

	var err error
	token, err = generateMDSToken()
	if err != nil {
		rerr = fmt.Errorf("failed to generate MDS token: %v", err)
		return
	}

	pmfPath := common.PodManifestPath(root)
	pmf, err := os.Open(pmfPath)
	if err != nil {
		rerr = fmt.Errorf("failed to open runtime manifest (%v): %v", pmfPath, err)
		return
	}

	pth := fmt.Sprintf("/pods/%v?token=%v", u, token)
	err = httpRequest("PUT", pth, pmf)
	pmf.Close()
	if err != nil {
		rerr = fmt.Errorf("failed to register pod with metadata svc: %v", err)
		return
	}

	defer func() {
		if rerr != nil {
			unregisterPod(root, uuid)
		}
	}()

	rf, err := os.Create(filepath.Join(root, mdsRegisteredFile))
	if err != nil {
		rerr = fmt.Errorf("failed to create mds-register file: %v", err)
		return
	}
	rf.Close()

	for _, app := range apps {
		ampath := common.ImageManifestPath(root, app.Name)
		amf, err := os.Open(ampath)
		if err != nil {
			rerr = fmt.Errorf("failed reading app manifest %q: %v", ampath, err)
			return
		}

		err = registerApp(u, app.Name.String(), amf)
		amf.Close()
		if err != nil {
			rerr = fmt.Errorf("failed to register app with metadata svc: %v", err)
			return
		}
	}

	return
}

// unregisterPod unregisters pod with the metadata service.
func unregisterPod(root string, uuid *types.UUID) error {
	_, err := os.Stat(filepath.Join(root, mdsRegisteredFile))
	switch {
	case err == nil:
		pth := path.Join("/pods", uuid.String())
		return httpRequest("DELETE", pth, nil)

	case os.IsNotExist(err):
		return nil

	default:
		return err
	}
}

// setupTapDevice creates persistent tap devices
// and returns a newly created netlink.Link structure
func setupTapDevice(podID types.UUID) (netlink.Link, error) {
	// network device names are limited to 16 characters
	// the suffix %d will be replaced by the kernel with a suitable number
	nameTemplate := fmt.Sprintf("rkt-%s-tap%%d", podID.String()[0:4])
	ifName, err := tuntap.CreatePersistentIface(nameTemplate, tuntap.Tap)
	if err != nil {
		return nil, fmt.Errorf("tuntap persist %v", err)
	}
	link, err := netlink.LinkByName(ifName)
	if err != nil {
		return nil, fmt.Errorf("cannot find link %q: %v", ifName, err)
	}
	err = netlink.LinkSetUp(link)
	if err != nil {
		return nil, fmt.Errorf("cannot set link up %q: %v", ifName, err)
	}
	return link, nil
}

// GC enters the pod by fork/exec()ing the stage1's /gc similar to /init.
// /gc can expect to have its CWD set to the pod root.
// stage1Path is the path of the stage1 rootfs
func GC(pdir string, uuid *types.UUID, stage1Path string, debug bool) error {
	ep, err := getStage1Entrypoint(pdir, gcEntrypoint)
	if err != nil {
		return fmt.Errorf("error determining gc entrypoint: %v", err)
	}

	args := []string{filepath.Join(stage1Path, ep)}
	if debug {
		args = append(args, "--debug")
	}
	args = append(args, uuid.String())

	c := exec.Cmd{
		Path:   args[0],
		Args:   args,
		Stderr: os.Stderr,
		Dir:    pdir,
	}
	return c.Run()
}

// setupTapDevice creates persistent macvtap device
// and returns a newly created netlink.Link structure
func setupMacVTapDevice(podID types.UUID, config MacVTapNetConf) (netlink.Link, error) {
	master, err := netlink.LinkByName(config.Master)
	if err != nil {
		return nil, fmt.Errorf("Cannot find master device '%v': %v", config.Master, err)
	}
	var mode netlink.MacvlanMode
	switch config.Mode {
	// if not set - defaults to bridge mode as in:
	// https://github.com/coreos/rkt/blob/master/Documentation/networking.md#macvlan
	case "", "bridge":
		mode = netlink.MACVLAN_MODE_BRIDGE
	case "private":
		mode = netlink.MACVLAN_MODE_PRIVATE
	case "vepa":
		mode = netlink.MACVLAN_MODE_VEPA
	case "passthru":
		mode = netlink.MACVLAN_MODE_PASSTHRU
	default:
		return nil, fmt.Errorf("Unsupported macvtap mode: %v", config.Mode)
	}
	mtu := master.Attrs().MTU
	if config.MTU != 0 {
		mtu = config.MTU
	}
	nameTemplate := fmt.Sprintf("rkt-%s-vtap%%d", podID.String()[0:4])
	link := &netlink.Macvtap{
		Macvlan: netlink.Macvlan{
			LinkAttrs: netlink.LinkAttrs{
				Name:        nameTemplate,
				MTU:         mtu,
				ParentIndex: master.Attrs().Index,
			},
			Mode: mode,
		},
	}

	if err := netlink.LinkAdd(link); err != nil {
		return nil, fmt.Errorf("Cannot create macvtap interface: %v", err)
	}
	return link, nil
}

// kvmSetup prepare new Networking to be used in kvm environment based on tuntap pair interfaces
// to allow communication with virtual machine created by lkvm tool
// right now it only supports default "ptp" network type (other types ends with error)
func kvmSetup(podRoot string, podID types.UUID, fps []ForwardedPort, privateNetList common.PrivateNetList, localConfig string) (*Networking, error) {
	network := Networking{
		podEnv: podEnv{
			podRoot:      podRoot,
			podID:        podID,
			netsLoadList: privateNetList,
			localConfig:  localConfig,
		},
	}
	var e error
	network.nets, e = network.loadNets()
	if e != nil {
		return nil, fmt.Errorf("error loading network definitions: %v", e)
	}

	for _, n := range network.nets {
		switch n.conf.Type {
		case "ptp":
			link, err := setupTapDevice()
			if err != nil {
				return nil, err
			}
			ifName := link.Attrs().Name
			n.runtime.IfName = ifName

			err = kvmSetupNetAddressing(&network, n, ifName)
			if err != nil {
				return nil, err
			}

			// add address to host tap device
			err = netlink.AddrAdd(
				link,
				&netlink.Addr{
					IPNet: &net.IPNet{
						IP:   n.runtime.HostIP,
						Mask: net.IPMask(n.runtime.Mask),
					},
					Label: ifName,
				})
			if err != nil {
				return nil, fmt.Errorf("cannot add address to host tap device %q: %v", ifName, err)
			}

			if n.conf.IPMasq {
				h := sha512.Sum512([]byte(podID.String()))
				chain := fmt.Sprintf("CNI-%s-%x", n.conf.Name, h[:8])
				if err = ip.SetupIPMasq(&net.IPNet{
					IP:   n.runtime.IP,
					Mask: net.IPMask(n.runtime.Mask),
				}, chain); err != nil {
					return nil, err
				}
			}
		default:
			return nil, fmt.Errorf("network %q have unsupported type: %q", n.conf.Name, n.conf.Type)
		}
	}
	err := network.forwardPorts(fps, network.GetDefaultIP())
	if err != nil {
		return nil, err
	}

	return &network, nil
}

// unregisterPod unregisters pod with the metadata service.
func unregisterPod(uuid *types.UUID) error {
	pth := path.Join("/pods", uuid.String())
	return httpRequest("DELETE", pth, nil)
}

// kvmSetup prepare new Networking to be used in kvm environment based on tuntap pair interfaces
// to allow communication with virtual machine created by lkvm tool
func kvmSetup(podRoot string, podID types.UUID, fps []ForwardedPort, netList common.NetList, localConfig string) (*Networking, error) {
	network := Networking{
		podEnv: podEnv{
			podRoot:      podRoot,
			podID:        podID,
			netsLoadList: netList,
			localConfig:  localConfig,
		},
	}
	var e error
	network.nets, e = network.loadNets()
	if e != nil {
		return nil, fmt.Errorf("error loading network definitions: %v", e)
	}

	for i, n := range network.nets {
		if n.conf.Type == "flannel" {
			if err := kvmTransformFlannelNetwork(&n); err != nil {
				return nil, fmt.Errorf("cannot transform flannel network into basic network: %v", err)
			}
		}
		switch n.conf.Type {
		case "ptp":
			link, err := setupTapDevice(podID)
			if err != nil {
				return nil, err
			}
			ifName := link.Attrs().Name
			n.runtime.IfName = ifName

			err = kvmSetupNetAddressing(&network, n, ifName)
			if err != nil {
				return nil, err
			}

			// add address to host tap device
			err = ensureHasAddr(
				link,
				&net.IPNet{
					IP:   n.runtime.IP4.Gateway,
					Mask: net.IPMask(n.runtime.Mask),
				},
			)
			if err != nil {
				return nil, fmt.Errorf("cannot add address to host tap device %q: %v", ifName, err)
			}

			if err := removeAllRoutesOnLink(link); err != nil {
				return nil, fmt.Errorf("cannot remove route on host tap device %q: %v", ifName, err)
			}

			if err := addRoute(link, n.runtime.IP); err != nil {
				return nil, fmt.Errorf("cannot add on host direct route to pod: %v", err)
			}

		case "bridge":
			config := BridgeNetConf{
				NetConf: NetConf{
					MTU: defaultMTU,
				},
				BrName: defaultBrName,
			}
			if err := json.Unmarshal(n.confBytes, &config); err != nil {
				return nil, fmt.Errorf("error parsing %q result: %v", n.conf.Name, err)
			}

			br, err := ensureBridgeIsUp(config.BrName, config.MTU)
			if err != nil {
				return nil, fmt.Errorf("error in time of bridge setup: %v", err)
			}
			link, err := setupTapDevice(podID)
			if err != nil {
				return nil, fmt.Errorf("can not setup tap device: %v", err)
			}
			err = netlink.LinkSetMaster(link, br)
			if err != nil {
				rErr := tuntap.RemovePersistentIface(n.runtime.IfName, tuntap.Tap)
				if rErr != nil {
					log.Printf("Warning: could not cleanup tap interface: %v", rErr)
				}
				return nil, fmt.Errorf("can not add tap interface to bridge: %v", err)
			}

			ifName := link.Attrs().Name
			n.runtime.IfName = ifName

			err = kvmSetupNetAddressing(&network, n, ifName)
			if err != nil {
				return nil, err
			}

			if config.IsGw {
				err = ensureHasAddr(
					br,
					&net.IPNet{
						IP:   n.runtime.IP4.Gateway,
						Mask: net.IPMask(n.runtime.Mask),
					},
//.........这里部分代码省略.........

func writeUUIDToFile(uuid *types.UUID, path string) error {
	return ioutil.WriteFile(path, []byte(uuid.String()), 0644)
}