Added "host" driver and test code.

Signed-off-by: Jana Radhakrishnan <mrjana@docker.com>

drivers.go

@@ -3,6 +3,7 @@ package libnetwork
 import (
 	"github.com/docker/libnetwork/driverapi"
 	"github.com/docker/libnetwork/drivers/bridge"
+	"github.com/docker/libnetwork/drivers/host"
 	"github.com/docker/libnetwork/drivers/null"
 )
 
@@ -11,7 +12,11 @@ type driverTable map[string]driverapi.Driver
 func enumerateDrivers() driverTable {
 	drivers := make(driverTable)
 
-	for _, fn := range [](func() (string, driverapi.Driver)){bridge.New, null.New} {
+	for _, fn := range [](func() (string, driverapi.Driver)){
+		bridge.New,
+		host.New,
+		null.New,
+	} {
 		name, driver := fn()
 		drivers[name] = driver
 	}

drivers/host/host.go

@@ -0,0 +1,60 @@
+package host
+
+import (
+	"github.com/docker/libnetwork/driverapi"
+	"github.com/docker/libnetwork/sandbox"
+	"github.com/docker/libnetwork/types"
+)
+
+const networkType = "host"
+
+type driver struct{}
+
+// New provides a new instance of host driver
+func New() (string, driverapi.Driver) {
+	return networkType, &driver{}
+}
+
+func (d *driver) Config(option map[string]interface{}) error {
+	return nil
+}
+
+func (d *driver) CreateNetwork(id types.UUID, option map[string]interface{}) error {
+	return nil
+}
+
+func (d *driver) DeleteNetwork(nid types.UUID) error {
+	return nil
+}
+
+func (d *driver) CreateEndpoint(nid, eid types.UUID, epOptions map[string]interface{}) (*sandbox.Info, error) {
+	return nil, nil
+}
+
+func (d *driver) DeleteEndpoint(nid, eid types.UUID) error {
+	return nil
+}
+
+func (d *driver) EndpointInfo(nid, eid types.UUID) (map[string]interface{}, error) {
+	return make(map[string]interface{}, 0), nil
+}
+
+// Join method is invoked when a Sandbox is attached to an endpoint.
+func (d *driver) Join(nid, eid types.UUID, sboxKey string, options map[string]interface{}) (*driverapi.JoinInfo, error) {
+	jInfo := &driverapi.JoinInfo{
+		SandboxKey:      sandbox.GenerateKey("host"),
+		NoSandboxCreate: true,
+		HostsPath:       "/etc/hosts",
+	}
+
+	return jInfo, nil
+}
+
+// Leave method is invoked when a Sandbox detaches from an endpoint.
+func (d *driver) Leave(nid, eid types.UUID, options map[string]interface{}) error {
+	return nil
+}
+
+func (d *driver) Type() string {
+	return networkType
+}

libnetwork_test.go

@@ -89,6 +89,39 @@ func TestNull(t *testing.T) {
 	}
 }
 
+func TestHost(t *testing.T) {
+	network, err := createTestNetwork("host", "testnetwork", options.Generic{})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	ep, err := network.CreateEndpoint("testep")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = ep.Join("host_container",
+		libnetwork.JoinOptionHostname("test"),
+		libnetwork.JoinOptionDomainname("docker.io"),
+		libnetwork.JoinOptionExtraHost("web", "192.168.0.1"))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = ep.Leave("host_container")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if err := ep.Delete(); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := network.Delete(); err != nil {
+		t.Fatal(err)
+	}
+}
+
 func TestBridge(t *testing.T) {
 	defer netutils.SetupTestNetNS(t)()
 	ip, subnet, err := net.ParseCIDR("192.168.100.1/24")