@@ -300,6 +300,11 @@ func (cli *DaemonCli) start(opts daemonOptions) (err error) {

 	if err != nil {

 		logrus.Fatalf("Error creating cluster component: %v", err)

 	}

+	d.SetCluster(c)

+	err = c.Start()

+	if err != nil {

+		logrus.Fatalf("Error starting cluster component: %v", err)

+	}

 	// Restart all autostart containers which has a swarm endpoint

 	// and is not yet running now that we have successfully

@@ -316,7 +321,6 @@ func (cli *DaemonCli) start(opts daemonOptions) (err error) {

 	cli.d = d

-	d.SetCluster(c)

 	initRouter(api, d, c)

 	cli.setupConfigReloadTrap()

@@ -2,12 +2,14 @@ package daemon

 import (

 	apitypes "github.com/docker/docker/api/types"

+	lncluster "github.com/docker/libnetwork/cluster"

 )

 // Cluster is the interface for github.com/docker/docker/daemon/cluster.(*Cluster).

 type Cluster interface {

 	ClusterStatus

 	NetworkManager

+	SendClusterEvent(event lncluster.ConfigEventType)

 }

 // ClusterStatus interface provides information about the Swarm status of the Cluster

@@ -51,6 +51,7 @@ import (

 	types "github.com/docker/docker/api/types/swarm"

 	executorpkg "github.com/docker/docker/daemon/cluster/executor"

 	"github.com/docker/docker/pkg/signal"

+	lncluster "github.com/docker/libnetwork/cluster"

 	swarmapi "github.com/docker/swarmkit/api"

 	swarmnode "github.com/docker/swarmkit/node"

 	"github.com/pkg/errors"

@@ -115,7 +116,7 @@ type Cluster struct {

 	root         string

 	runtimeRoot  string

 	config       Config

-	configEvent  chan struct{} // todo: make this array and goroutine safe

+	configEvent  chan lncluster.ConfigEventType // todo: make this array and goroutine safe

 	attachers    map[string]*attacher

 }

@@ -147,22 +148,30 @@ func New(config Config) (*Cluster, error) {

 	c := &Cluster{

 		root:        root,

 		config:      config,

-		configEvent: make(chan struct{}, 10),

+		configEvent: make(chan lncluster.ConfigEventType, 10),

 		runtimeRoot: config.RuntimeRoot,

 		attachers:   make(map[string]*attacher),

 	}

+	return c, nil

+}

+

+// Start the Cluster instance

+// TODO The split between New and Start can be join again when the SendClusterEvent

+// method is no longer required

+func (c *Cluster) Start() error {

+	root := filepath.Join(c.config.Root, swarmDirName)

 	nodeConfig, err := loadPersistentState(root)

 	if err != nil {

 		if os.IsNotExist(err) {

-			return c, nil

+			return nil

 		}

-		return nil, err

+		return err

 	}

 	nr, err := c.newNodeRunner(*nodeConfig)

 	if err != nil {

-		return nil, err

+		return err

 	}

 	c.nr = nr

@@ -172,10 +181,10 @@ func New(config Config) (*Cluster, error) {

 	case err := <-nr.Ready():

 		if err != nil {

 			logrus.WithError(err).Error("swarm component could not be started")

-			return c, nil

+			return nil

 		}

 	}

-	return c, nil

+	return nil

 }

 func (c *Cluster) newNodeRunner(conf nodeStartConfig) (*nodeRunner, error) {

@@ -308,7 +317,7 @@ func (c *Cluster) getRemoteAddressList() []string {

 // ListenClusterEvents returns a channel that receives messages on cluster

 // participation changes.

 // todo: make cancelable and accessible to multiple callers

-func (c *Cluster) ListenClusterEvents() <-chan struct{} {

+func (c *Cluster) ListenClusterEvents() <-chan lncluster.ConfigEventType {

 	return c.configEvent

 }

@@ -413,3 +422,13 @@ func (c *Cluster) lockedManagerAction(fn func(ctx context.Context, state nodeSta

 	return fn(ctx, state)

 }

+

+// SendClusterEvent allows to send cluster events on the configEvent channel

+// TODO This method should not be exposed.

+// Currently it is used to notify the network controller that the keys are

+// available

+func (c *Cluster) SendClusterEvent(event lncluster.ConfigEventType) {

+	c.mu.RLock()

+	defer c.mu.RUnlock()

+	c.configEvent <- event

+}

@@ -11,6 +11,7 @@ import (

 	"github.com/Sirupsen/logrus"

 	types "github.com/docker/docker/api/types/swarm"

 	"github.com/docker/docker/daemon/cluster/executor/container"

+	lncluster "github.com/docker/libnetwork/cluster"

 	swarmapi "github.com/docker/swarmkit/api"

 	swarmnode "github.com/docker/swarmkit/node"

 	"github.com/pkg/errors"

@@ -162,7 +163,7 @@ func (n *nodeRunner) handleControlSocketChange(ctx context.Context, node *swarmn

 		}

 		n.grpcConn = conn

 		n.mu.Unlock()

-		n.cluster.configEvent <- struct{}{}

+		n.cluster.SendClusterEvent(lncluster.EventSocketChange)

 	}

 }

@@ -175,7 +176,7 @@ func (n *nodeRunner) handleReadyEvent(ctx context.Context, node *swarmnode.Node,

 		close(ready)

 	case <-ctx.Done():

 	}

-	n.cluster.configEvent <- struct{}{}

+	n.cluster.SendClusterEvent(lncluster.EventNodeReady)

 }

 func (n *nodeRunner) handleNodeExit(node *swarmnode.Node) {

@@ -217,6 +218,7 @@ func (n *nodeRunner) Stop() error {

 	if err := n.swarmNode.Stop(ctx); err != nil && !strings.Contains(err.Error(), "context canceled") {

 		return err

 	}

+	n.cluster.SendClusterEvent(lncluster.EventNodeLeave)

 	<-n.done

 	return nil

 }

@@ -388,7 +388,6 @@ func (c *Cluster) Leave(force bool) error {

 		}

 	}

-	c.configEvent <- struct{}{}

 	// todo: cleanup optional?

 	if err := clearPersistentState(c.root); err != nil {

 		return err

@@ -16,6 +16,7 @@ import (

 	"github.com/docker/docker/pkg/plugingetter"

 	"github.com/docker/docker/runconfig"

 	"github.com/docker/libnetwork"

+	lncluster "github.com/docker/libnetwork/cluster"

 	"github.com/docker/libnetwork/driverapi"

 	"github.com/docker/libnetwork/ipamapi"

 	networktypes "github.com/docker/libnetwork/types"

@@ -207,7 +208,6 @@ func (daemon *Daemon) setupIngress(create *clustertypes.NetworkCreateRequest, ip

 func (daemon *Daemon) releaseIngress(id string) {

 	controller := daemon.netController

-

 	if err := controller.SandboxDestroy("ingress-sbox"); err != nil {

 		logrus.Errorf("Failed to delete ingress sandbox: %v", err)

 	}

@@ -233,13 +233,17 @@ func (daemon *Daemon) releaseIngress(id string) {

 		logrus.Errorf("Failed to delete ingress network %s: %v", n.ID(), err)

 		return

 	}

-

 	return

 }

 // SetNetworkBootstrapKeys sets the bootstrap keys.

 func (daemon *Daemon) SetNetworkBootstrapKeys(keys []*networktypes.EncryptionKey) error {

-	return daemon.netController.SetKeys(keys)

+	err := daemon.netController.SetKeys(keys)

+	if err == nil {

+		// Upon successful key setting dispatch the keys available event

+		daemon.cluster.SendClusterEvent(lncluster.EventNetworkKeysAvailable)

+	}

+	return err

 }

 // UpdateAttachment notifies the attacher about the attachment config.

@@ -1980,3 +1980,24 @@ func (s *DockerSwarmSuite) TestSwarmInitUnspecifiedDataPathAddr(c *check.C) {

 	c.Assert(err, checker.NotNil)

 	c.Assert(out, checker.Contains, "data path address must be a non-zero IP")

 }

+

+func (s *DockerSwarmSuite) TestSwarmJoinLeave(c *check.C) {

+	d := s.AddDaemon(c, true, true)

+

+	out, err := d.Cmd("swarm", "join-token", "-q", "worker")

+	c.Assert(err, checker.IsNil)

+	c.Assert(strings.TrimSpace(out), checker.Not(checker.Equals), "")

+

+	token := strings.TrimSpace(out)

+

+	// Verify that back to back join/leave does not cause panics

+	d1 := s.AddDaemon(c, false, false)

+	for i := 0; i < 10; i++ {

+		out, err = d1.Cmd("swarm", "join", "--token", token, d.ListenAddr)

+		c.Assert(err, checker.IsNil)

+		c.Assert(strings.TrimSpace(out), checker.Not(checker.Equals), "")

+

+		_, err = d1.Cmd("swarm", "leave")

+		c.Assert(err, checker.IsNil)

+	}

+}