Merge pull request #35490 from bprashanth/dockershim_probe_net

Automatic merge from submit-queue

Migrate Network Logic into runtime II

- [x] Probing
- [x] Bootstrap CIDR
- [x] Setup/Teardown
- [ ] ~~Hostports~~
- [ ] ~~BWShaping~~

https://github.com/kubernetes/kubernetes/pull/34780

pkg/kubelet/container/runtime.go

@@ -118,6 +118,10 @@ type Runtime interface {
 	ContainerAttacher
 	// ImageService provides methods to image-related methods.
 	ImageService
+	// UpdatePodCIDR sends a new podCIDR to the runtime.
+	// This method just proxies a new runtimeConfig with the updated
+	// CIDR value down to the runtime shim.
+	UpdatePodCIDR(podCIDR string) error
 }
 
 type ImageService interface {

pkg/kubelet/container/testing/fake_runtime.go

@@ -118,6 +118,11 @@ func (f *FakeRuntime) ClearCalls() {
 	f.StatusErr = nil
 }
 
+// UpdatePodCIDR fulfills the cri interface.
+func (f *FakeRuntime) UpdatePodCIDR(c string) error {
+	return nil
+}
+
 func (f *FakeRuntime) assertList(expect []string, test []string) error {
 	if !reflect.DeepEqual(expect, test) {
 		return fmt.Errorf("expected %#v, got %#v", expect, test)

pkg/kubelet/container/testing/runtime_mock.go

@@ -153,3 +153,8 @@ func (r *Mock) ImageStats() (*ImageStats, error) {
 	args := r.Called()
 	return args.Get(0).(*ImageStats), args.Error(1)
 }
+
+// UpdatePodCIDR fulfills the cri interface.
+func (r *Mock) UpdatePodCIDR(c string) error {
+	return nil
+}

pkg/kubelet/dockershim/BUILD

@@ -27,11 +27,15 @@ go_library(
     tags = ["automanaged"],
     deps = [
         "//pkg/api:go_default_library",
+        "//pkg/apis/componentconfig:go_default_library",
         "//pkg/kubelet/api:go_default_library",
         "//pkg/kubelet/api/v1alpha1/runtime:go_default_library",
         "//pkg/kubelet/container:go_default_library",
         "//pkg/kubelet/dockertools:go_default_library",
         "//pkg/kubelet/leaky:go_default_library",
+        "//pkg/kubelet/network:go_default_library",
+        "//pkg/kubelet/network/cni:go_default_library",
+        "//pkg/kubelet/network/kubenet:go_default_library",
         "//pkg/kubelet/qos:go_default_library",
         "//pkg/kubelet/server/streaming:go_default_library",
         "//pkg/kubelet/types:go_default_library",
@@ -63,12 +67,16 @@ go_test(
     deps = [
         "//pkg/api:go_default_library",
         "//pkg/kubelet/api/v1alpha1/runtime:go_default_library",
+        "//pkg/kubelet/container:go_default_library",
         "//pkg/kubelet/container/testing:go_default_library",
         "//pkg/kubelet/dockertools:go_default_library",
+        "//pkg/kubelet/network:go_default_library",
+        "//pkg/kubelet/network/mock_network:go_default_library",
         "//pkg/kubelet/types:go_default_library",
         "//pkg/security/apparmor:go_default_library",
         "//pkg/util/clock:go_default_library",
         "//vendor:github.com/docker/engine-api/types",
+        "//vendor:github.com/golang/mock/gomock",
         "//vendor:github.com/stretchr/testify/assert",
     ],
 )

pkg/kubelet/dockershim/docker_sandbox.go

@@ -25,6 +25,7 @@ import (
 	"github.com/golang/glog"
 
 	runtimeApi "k8s.io/kubernetes/pkg/kubelet/api/v1alpha1/runtime"
+	kubecontainer "k8s.io/kubernetes/pkg/kubelet/container"
 	"k8s.io/kubernetes/pkg/kubelet/qos"
 	"k8s.io/kubernetes/pkg/kubelet/types"
 )
@@ -37,6 +38,9 @@ const (
 
 	// Termination grace period
 	defaultSandboxGracePeriod int = 10
+
+	// Name of the underlying container runtime
+	runtimeName = "docker"
 )
 
 // RunPodSandbox creates and starts a pod-level sandbox. Runtimes should ensure
@@ -72,12 +76,48 @@ func (ds *dockerService) RunPodSandbox(config *runtimeApi.PodSandboxConfig) (str
 	// Assume kubelet's garbage collector would remove the sandbox later, if
 	// startContainer failed.
 	err = ds.client.StartContainer(createResp.ID)
+	if err != nil {
+		return createResp.ID, fmt.Errorf("failed to start sandbox container for pod %q: %v", config.Metadata.GetName(), err)
+	}
+	if config.GetLinux().GetNamespaceOptions().GetHostNetwork() {
+		return createResp.ID, nil
+	}
+
+	// Step 4: Setup networking for the sandbox.
+	// All pod networking is setup by a CNI plugin discovered at startup time.
+	// This plugin assigns the pod ip, sets up routes inside the sandbox,
+	// creates interfaces etc. In theory, its jurisdiction ends with pod
+	// sandbox networking, but it might insert iptables rules or open ports
+	// on the host as well, to satisfy parts of the pod spec that aren't
+	// recognized by the CNI standard yet.
+	cID := kubecontainer.BuildContainerID(runtimeName, createResp.ID)
+	err = ds.networkPlugin.SetUpPod(config.GetMetadata().GetNamespace(), config.GetMetadata().GetName(), cID)
+	// TODO: Do we need to teardown on failure or can we rely on a StopPodSandbox call with the given ID?
 	return createResp.ID, err
 }
 
 // StopPodSandbox stops the sandbox. If there are any running containers in the
 // sandbox, they should be force terminated.
+// TODO: This function blocks sandbox teardown on networking teardown. Is it
+// better to cut our losses assuming an out of band GC routine will cleanup
+// after us?
 func (ds *dockerService) StopPodSandbox(podSandboxID string) error {
+	status, err := ds.PodSandboxStatus(podSandboxID)
+	if err != nil {
+		return fmt.Errorf("Failed to get sandbox status: %v", err)
+	}
+	if !status.GetLinux().GetNamespaces().GetOptions().GetHostNetwork() {
+		m := status.GetMetadata()
+		cID := kubecontainer.BuildContainerID(runtimeName, podSandboxID)
+		if err := ds.networkPlugin.TearDownPod(m.GetNamespace(), m.GetName(), cID); err != nil {
+			// TODO: Figure out a way to retry this error. We can't
+			// right now because the plugin throws errors when it doesn't find
+			// eth0, which might not exist for various reasons (setup failed,
+			// conf changed etc). In theory, it should teardown everything else
+			// so there's no need to retry.
+			glog.Errorf("Failed to teardown sandbox %v for pod %v/%v: %v", m.GetNamespace(), m.GetName(), podSandboxID, err)
+		}
+	}
 	return ds.client.StopContainer(podSandboxID, defaultSandboxGracePeriod)
 	// TODO: Stop all running containers in the sandbox.
 }
@@ -89,6 +129,53 @@ func (ds *dockerService) RemovePodSandbox(podSandboxID string) error {
 	// TODO: remove all containers in the sandbox.
 }
 
+// getIPFromPlugin interrogates the network plugin for an IP.
+func (ds *dockerService) getIPFromPlugin(sandbox *dockertypes.ContainerJSON) (string, error) {
+	metadata, err := parseSandboxName(sandbox.Name)
+	if err != nil {
+		return "", err
+	}
+	msg := fmt.Sprintf("Couldn't find network status for %s/%s through plugin", *metadata.Namespace, *metadata.Name)
+	if sharesHostNetwork(sandbox) {
+		return "", fmt.Errorf("%v: not responsible for host-network sandboxes", msg)
+	}
+	cID := kubecontainer.BuildContainerID(runtimeName, sandbox.ID)
+	networkStatus, err := ds.networkPlugin.GetPodNetworkStatus(*metadata.Namespace, *metadata.Name, cID)
+	if err != nil {
+		// This might be a sandbox that somehow ended up without a default
+		// interface (eth0). We can't distinguish this from a more serious
+		// error, so callers should probably treat it as non-fatal.
+		return "", fmt.Errorf("%v: %v", msg, err)
+	}
+	if networkStatus == nil {
+		return "", fmt.Errorf("%v: invalid network status for", msg)
+	}
+	return networkStatus.IP.String(), nil
+}
+
+// getIP returns the ip given the output of `docker inspect` on a pod sandbox,
+// first interrogating any registered plugins, then simply trusting the ip
+// in the sandbox itself. We look for an ipv4 address before ipv6.
+func (ds *dockerService) getIP(sandbox *dockertypes.ContainerJSON) (string, error) {
+	if sandbox.NetworkSettings == nil {
+		return "", nil
+	}
+	if IP, err := ds.getIPFromPlugin(sandbox); err != nil {
+		glog.Warningf("%v", err)
+	} else if IP != "" {
+		return IP, nil
+	}
+	// TODO: trusting the docker ip is not a great idea. However docker uses
+	// eth0 by default and so does CNI, so if we find a docker IP here, we
+	// conclude that the plugin must have failed setup, or forgotten its ip.
+	// This is not a sensible assumption for plugins across the board, but if
+	// a plugin doesn't want this behavior, it can throw an error.
+	if sandbox.NetworkSettings.IPAddress != "" {
+		return sandbox.NetworkSettings.IPAddress, nil
+	}
+	return sandbox.NetworkSettings.GlobalIPv6Address, nil
+}
+
 // PodSandboxStatus returns the status of the PodSandbox.
 func (ds *dockerService) PodSandboxStatus(podSandboxID string) (*runtimeApi.PodSandboxStatus, error) {
 	// Inspect the container.
@@ -109,20 +196,9 @@ func (ds *dockerService) PodSandboxStatus(podSandboxID string) (*runtimeApi.PodS
 	if r.State.Running {
 		state = runtimeApi.PodSandBoxState_READY
 	}
-
-	// TODO: We can't really get the IP address from the network plugin, which
-	// is handled by kubelet as of now. Should we amend the interface? How is
-	// this handled in the new remote runtime integration?
-	// See DockerManager.determineContainerIP() for more details.
-	// For now, just assume that there is no network plugin.
-	// Related issue: https://github.com/kubernetes/kubernetes/issues/28667
-	var IP string
-	if r.NetworkSettings != nil {
-		IP = r.NetworkSettings.IPAddress
-		// Fall back to IPv6 address if no IPv4 address is present
-		if IP == "" {
-			IP = r.NetworkSettings.GlobalIPv6Address
-		}
+	IP, err := ds.getIP(r)
+	if err != nil {
+		return nil, err
 	}
 	network := &runtimeApi.PodSandboxNetworkStatus{Ip: &IP}
 	netNS := getNetworkNamespace(r)
@@ -131,7 +207,7 @@ func (ds *dockerService) PodSandboxStatus(podSandboxID string) (*runtimeApi.PodS
 	if err != nil {
 		return nil, err
 	}
-
+	hostNetwork := sharesHostNetwork(r)
 	labels, annotations := extractLabels(r.Config.Labels)
 	return &runtimeApi.PodSandboxStatus{
 		Id:          &r.ID,
@@ -141,7 +217,14 @@ func (ds *dockerService) PodSandboxStatus(podSandboxID string) (*runtimeApi.PodS
 		Labels:      labels,
 		Annotations: annotations,
 		Network:     network,
-		Linux:       &runtimeApi.LinuxPodSandboxStatus{Namespaces: &runtimeApi.Namespace{Network: &netNS}},
+		Linux: &runtimeApi.LinuxPodSandboxStatus{
+			Namespaces: &runtimeApi.Namespace{
+				Network: &netNS,
+				Options: &runtimeApi.NamespaceOption{
+					HostNetwork: &hostNetwork,
+				},
+			},
+		},
 	}, nil
 }
 
@@ -279,6 +362,15 @@ func (ds *dockerService) makeSandboxDockerConfig(c *runtimeApi.PodSandboxConfig,
 	return createConfig, nil
 }
 
+// sharesHostNetwork true if the given container is sharing the hosts's
+// network namespace.
+func sharesHostNetwork(container *dockertypes.ContainerJSON) bool {
+	if container != nil && container.HostConfig != nil {
+		return string(container.HostConfig.NetworkMode) == namespaceModeHost
+	}
+	return false
+}
+
 func setSandboxResources(hc *dockercontainer.HostConfig) {
 	hc.Resources = dockercontainer.Resources{
 		MemorySwap: -1, // Always disable memory swap.

pkg/kubelet/dockershim/docker_sandbox_test.go

@@ -25,6 +25,7 @@ import (
 	"github.com/stretchr/testify/assert"
 
 	runtimeApi "k8s.io/kubernetes/pkg/kubelet/api/v1alpha1/runtime"
+	kubecontainer "k8s.io/kubernetes/pkg/kubelet/container"
 	"k8s.io/kubernetes/pkg/kubelet/types"
 )
 
@@ -99,12 +100,13 @@ func TestSandboxStatus(t *testing.T) {
 
 	state := runtimeApi.PodSandBoxState_READY
 	ct := int64(0)
+	hostNetwork := false
 	expected := &runtimeApi.PodSandboxStatus{
 		State:       &state,
 		CreatedAt:   &ct,
 		Metadata:    config.Metadata,
 		Network:     &runtimeApi.PodSandboxNetworkStatus{Ip: &fakeIP},
-		Linux:       &runtimeApi.LinuxPodSandboxStatus{Namespaces: &runtimeApi.Namespace{Network: &fakeNS}},
+		Linux:       &runtimeApi.LinuxPodSandboxStatus{Namespaces: &runtimeApi.Namespace{Network: &fakeNS, Options: &runtimeApi.NamespaceOption{HostNetwork: &hostNetwork}}},
 		Labels:      labels,
 		Annotations: annotations,
 	}
@@ -138,3 +140,57 @@ func TestSandboxStatus(t *testing.T) {
 	status, err = ds.PodSandboxStatus(id)
 	assert.Error(t, err, fmt.Sprintf("status of sandbox: %+v", status))
 }
+
+// TestNetworkPluginInvocation checks that the right SetUpPod and TearDownPod
+// calls are made when we run/stop a sandbox.
+func TestNetworkPluginInvocation(t *testing.T) {
+	ds, _, _ := newTestDockerService()
+	mockPlugin := newTestNetworkPlugin(t)
+	ds.networkPlugin = mockPlugin
+	defer mockPlugin.Finish()
+
+	name := "foo0"
+	ns := "bar0"
+	c := makeSandboxConfigWithLabelsAndAnnotations(
+		name, ns, "0", 0,
+		map[string]string{"label": name},
+		map[string]string{"annotation": ns},
+	)
+	cID := kubecontainer.ContainerID{Type: runtimeName, ID: fmt.Sprintf("/%v", makeSandboxName(c))}
+
+	setup := mockPlugin.EXPECT().SetUpPod(ns, name, cID)
+	// StopPodSandbox performs a lookup on status to figure out if the sandbox
+	// is running with hostnetworking, as all its given is the ID.
+	mockPlugin.EXPECT().GetPodNetworkStatus(ns, name, cID)
+	mockPlugin.EXPECT().TearDownPod(ns, name, cID).After(setup)
+
+	_, err := ds.RunPodSandbox(c)
+	assert.NoError(t, err)
+	err = ds.StopPodSandbox(cID.ID)
+	assert.NoError(t, err)
+}
+
+// TestHostNetworkPluginInvocation checks that *no* SetUp/TearDown calls happen
+// for host network sandboxes.
+func TestHostNetworkPluginInvocation(t *testing.T) {
+	ds, _, _ := newTestDockerService()
+	mockPlugin := newTestNetworkPlugin(t)
+	ds.networkPlugin = mockPlugin
+	defer mockPlugin.Finish()
+
+	name := "foo0"
+	ns := "bar0"
+	c := makeSandboxConfigWithLabelsAndAnnotations(
+		name, ns, "0", 0,
+		map[string]string{"label": name},
+		map[string]string{"annotation": ns},
+	)
+	hostNetwork := true
+	c.Linux = &runtimeApi.LinuxPodSandboxConfig{NamespaceOptions: &runtimeApi.NamespaceOption{HostNetwork: &hostNetwork}}
+	cID := kubecontainer.ContainerID{Type: runtimeName, ID: fmt.Sprintf("/%v", makeSandboxName(c))}
+
+	// No calls to network plugin are expected
+	_, err := ds.RunPodSandbox(c)
+	assert.NoError(t, err)
+	assert.NoError(t, ds.StopPodSandbox(cID.ID))
+}

pkg/kubelet/dockershim/docker_service.go

@@ -20,11 +20,16 @@ import (
 	"fmt"
 	"io"
 
+	"github.com/golang/glog"
 	"k8s.io/kubernetes/pkg/api"
+	"k8s.io/kubernetes/pkg/apis/componentconfig"
 	internalApi "k8s.io/kubernetes/pkg/kubelet/api"
 	runtimeApi "k8s.io/kubernetes/pkg/kubelet/api/v1alpha1/runtime"
 	kubecontainer "k8s.io/kubernetes/pkg/kubelet/container"
 	"k8s.io/kubernetes/pkg/kubelet/dockertools"
+	"k8s.io/kubernetes/pkg/kubelet/network"
+	"k8s.io/kubernetes/pkg/kubelet/network/cni"
+	"k8s.io/kubernetes/pkg/kubelet/network/kubenet"
 	"k8s.io/kubernetes/pkg/kubelet/server/streaming"
 	"k8s.io/kubernetes/pkg/util/term"
 )
@@ -53,10 +58,41 @@ const (
 	sandboxIDLabelKey           = "io.kubernetes.sandbox.id"
 )
 
+// NetworkPluginArgs is the subset of kubelet runtime args we pass
+// to the container runtime shim so it can probe for network plugins.
+// In the future we will feed these directly to a standalone container
+// runtime process.
+type NetworkPluginSettings struct {
+	// HairpinMode is best described by comments surrounding the kubelet arg
+	HairpinMode componentconfig.HairpinMode
+	// NonMasqueradeCIDR is the range of ips which should *not* be included
+	// in any MASQUERADE rules applied by the plugin
+	NonMasqueradeCIDR string
+	// PluginName is the name of the plugin, runtime shim probes for
+	PluginName string
+	// PluginBinDir is the directory in which the binaries for the plugin with
+	// PluginName is kept. The admin is responsible for provisioning these
+	// binaries before-hand.
+	PluginBinDir string
+	// PluginConfDir is the directory in which the admin places a CNI conf.
+	// Depending on the plugin, this may be an optional field, eg: kubenet
+	// generates its own plugin conf.
+	PluginConfDir string
+	// MTU is the desired MTU for network devices created by the plugin.
+	MTU int
+
+	// RuntimeHost is an interface that serves as a trap-door from plugin back
+	// into the kubelet.
+	// TODO: This shouldn't be required, remove once we move host ports into CNI
+	// and figure out bandwidth shaping. See corresponding comments above
+	// network.Host interface.
+	LegacyRuntimeHost network.LegacyHost
+}
+
 var internalLabelKeys []string = []string{containerTypeLabelKey, containerLogPathLabelKey, sandboxIDLabelKey}
 
 // NOTE: Anything passed to DockerService should be eventually handled in another way when we switch to running the shim as a different process.
-func NewDockerService(client dockertools.DockerInterface, seccompProfileRoot string, podSandboxImage string, streamingConfig *streaming.Config) (DockerService, error) {
+func NewDockerService(client dockertools.DockerInterface, seccompProfileRoot string, podSandboxImage string, streamingConfig *streaming.Config, pluginSettings *NetworkPluginSettings) (DockerService, error) {
 	ds := &dockerService{
 		seccompProfileRoot: seccompProfileRoot,
 		client:             dockertools.NewInstrumentedDockerInterface(client),
@@ -76,6 +112,19 @@ func NewDockerService(client dockertools.DockerInterface, seccompProfileRoot str
 			return nil, err
 		}
 	}
+	// dockershim currently only supports CNI plugins.
+	cniPlugins := cni.ProbeNetworkPlugins(pluginSettings.PluginConfDir, pluginSettings.PluginBinDir)
+	cniPlugins = append(cniPlugins, kubenet.NewPlugin(pluginSettings.PluginBinDir))
+	netHost := &dockerNetworkHost{
+		pluginSettings.LegacyRuntimeHost,
+		&namespaceGetter{ds},
+	}
+	plug, err := network.InitNetworkPlugin(cniPlugins, pluginSettings.PluginName, netHost, pluginSettings.HairpinMode, pluginSettings.NonMasqueradeCIDR, pluginSettings.MTU)
+	if err != nil {
+		return nil, fmt.Errorf("didn't find compatible CNI plugin with given settings %+v: %v", pluginSettings, err)
+	}
+	ds.networkPlugin = plug
+	glog.Infof("Docker cri networking managed by %v", plug.Name())
 	return ds, nil
 }
 
@@ -105,6 +154,7 @@ type dockerService struct {
 	podSandboxImage    string
 	streamingRuntime   *streamingRuntime
 	streamingServer    streaming.Server
+	networkPlugin      network.NetworkPlugin
 }
 
 // Version returns the runtime name, runtime version and runtime API version
@@ -126,6 +176,41 @@ func (ds *dockerService) Version(_ string) (*runtimeApi.VersionResponse, error)
 	}, nil
 }
 
-func (ds *dockerService) UpdateRuntimeConfig(runtimeConfig *runtimeApi.RuntimeConfig) error {
-	return nil
+// UpdateRuntimeConfig updates the runtime config. Currently only handles podCIDR updates.
+func (ds *dockerService) UpdateRuntimeConfig(runtimeConfig *runtimeApi.RuntimeConfig) (err error) {
+	if runtimeConfig == nil {
+		return
+	}
+	glog.Infof("docker cri received runtime config %+v", runtimeConfig)
+	if ds.networkPlugin != nil && runtimeConfig.NetworkConfig.PodCidr != nil {
+		event := make(map[string]interface{})
+		event[network.NET_PLUGIN_EVENT_POD_CIDR_CHANGE_DETAIL_CIDR] = *runtimeConfig.NetworkConfig.PodCidr
+		ds.networkPlugin.Event(network.NET_PLUGIN_EVENT_POD_CIDR_CHANGE, event)
+	}
+	return
+}
+
+// namespaceGetter is a wrapper around the dockerService that implements
+// the network.NamespaceGetter interface.
+type namespaceGetter struct {
+	*dockerService
+}
+
+// GetNetNS returns the network namespace of the given containerID. The ID
+// supplied is typically the ID of a pod sandbox. This getter doesn't try
+// to map non-sandbox IDs to their respective sandboxes.
+func (ds *dockerService) GetNetNS(podSandboxID string) (string, error) {
+	r, err := ds.client.InspectContainer(podSandboxID)
+	if err != nil {
+		return "", err
+	}
+	return getNetworkNamespace(r), nil
+}
+
+// dockerNetworkHost implements network.Host by wrapping the legacy host
+// passed in by the kubelet and adding NamespaceGetter methods. The legacy
+// host methods are slated for deletion.
+type dockerNetworkHost struct {
+	network.LegacyHost
+	*namespaceGetter
 }

pkg/kubelet/dockershim/docker_service_test.go

@@ -17,15 +17,25 @@ limitations under the License.
 package dockershim
 
 import (
+	"github.com/golang/mock/gomock"
+	"testing"
 	"time"
 
 	containertest "k8s.io/kubernetes/pkg/kubelet/container/testing"
 	"k8s.io/kubernetes/pkg/kubelet/dockertools"
+	"k8s.io/kubernetes/pkg/kubelet/network"
+	"k8s.io/kubernetes/pkg/kubelet/network/mock_network"
 	"k8s.io/kubernetes/pkg/util/clock"
 )
 
+// newTestNetworkPlugin returns a mock plugin that implements network.NetworkPlugin
+func newTestNetworkPlugin(t *testing.T) *mock_network.MockNetworkPlugin {
+	ctrl := gomock.NewController(t)
+	return mock_network.NewMockNetworkPlugin(ctrl)
+}
+
 func newTestDockerService() (*dockerService, *dockertools.FakeDockerClient, *clock.FakeClock) {
 	fakeClock := clock.NewFakeClock(time.Time{})
 	c := dockertools.NewFakeDockerClientWithClock(fakeClock)
-	return &dockerService{client: c, os: &containertest.FakeOS{}}, c, fakeClock
+	return &dockerService{client: c, os: &containertest.FakeOS{}, networkPlugin: &network.NoopNetworkPlugin{}}, c, fakeClock
 }

pkg/kubelet/dockertools/docker_manager.go

@@ -1321,6 +1321,12 @@ func (dm *DockerManager) PortForward(pod *kubecontainer.Pod, port uint16, stream
 	return PortForward(dm.client, podInfraContainer.ID.ID, port, stream)
 }
 
+// UpdatePodCIDR updates the podCIDR for the runtime.
+// Currently no-ops, just implemented to satisfy the cri.
+func (dm *DockerManager) UpdatePodCIDR(podCIDR string) error {
+	return nil
+}
+
 // Temporarily export this function to share with dockershim.
 func PortForward(client DockerInterface, podInfraContainerID string, port uint16, stream io.ReadWriteCloser) error {
 	container, err := client.InspectContainer(podInfraContainerID)

pkg/kubelet/kubelet.go

@@ -456,7 +456,7 @@ func NewMainKubelet(kubeCfg *componentconfig.KubeletConfiguration, kubeDeps *Kub
 	}
 	glog.Infof("Hairpin mode set to %q", klet.hairpinMode)
 
-	if plug, err := network.InitNetworkPlugin(kubeDeps.NetworkPlugins, kubeCfg.NetworkPluginName, &networkHost{klet}, klet.hairpinMode, klet.nonMasqueradeCIDR, int(kubeCfg.NetworkPluginMTU)); err != nil {
+	if plug, err := network.InitNetworkPlugin(kubeDeps.NetworkPlugins, kubeCfg.NetworkPluginName, &criNetworkHost{&networkHost{klet}}, klet.hairpinMode, klet.nonMasqueradeCIDR, int(kubeCfg.NetworkPluginMTU)); err != nil {
 		return nil, err
 	} else {
 		klet.networkPlugin = plug
@@ -482,6 +482,26 @@ func NewMainKubelet(kubeCfg *componentconfig.KubeletConfiguration, kubeDeps *Kub
 		}
 	}
 
+	// TODO: These need to become arguments to a standalone docker shim.
+	binDir := kubeCfg.CNIBinDir
+	if binDir == "" {
+		binDir = kubeCfg.NetworkPluginDir
+	}
+	pluginSettings := dockershim.NetworkPluginSettings{
+		HairpinMode:       klet.hairpinMode,
+		NonMasqueradeCIDR: klet.nonMasqueradeCIDR,
+		PluginName:        kubeCfg.NetworkPluginName,
+		PluginConfDir:     kubeCfg.CNIConfDir,
+		PluginBinDir:      binDir,
+		MTU:               int(kubeCfg.NetworkPluginMTU),
+	}
+
+	// Remote runtime shim just cannot talk back to kubelet, so it doesn't
+	// support bandwidth shaping or hostports till #35457. To enable legacy
+	// features, replace with networkHost.
+	var nl *noOpLegacyHost
+	pluginSettings.LegacyRuntimeHost = nl
+
 	// Initialize the runtime.
 	switch kubeCfg.ContainerRuntime {
 	case "docker":
@@ -489,10 +509,7 @@ func NewMainKubelet(kubeCfg *componentconfig.KubeletConfiguration, kubeDeps *Kub
 		case "cri":
 			// Use the new CRI shim for docker. This is needed for testing the
 			// docker integration through CRI, and may be removed in the future.
-			dockerService, err := dockershim.NewDockerService(klet.dockerClient, kubeCfg.SeccompProfileRoot, kubeCfg.PodInfraContainerImage, nil)
-			if err != nil {
-				return nil, err
-			}
+			dockerService, err := dockershim.NewDockerService(klet.dockerClient, kubeCfg.SeccompProfileRoot, kubeCfg.PodInfraContainerImage, nil, &pluginSettings)
 			runtimeService := dockerService.(internalApi.RuntimeService)
 			imageService := dockerService.(internalApi.ImageManagerService)
 
@@ -520,6 +537,13 @@ func NewMainKubelet(kubeCfg *componentconfig.KubeletConfiguration, kubeDeps *Kub
 					return nil, err
 				}
 			}
+
+			// kubelet defers to the runtime shim to setup networking. Setting
+			// this to nil will prevent it from trying to invoke the plugin.
+			// It's easier to always probe and initialize plugins till cri
+			// becomes the default.
+			klet.networkPlugin = nil
+
 			klet.containerRuntime, err = kuberuntime.NewKubeGenericRuntimeManager(
 				kubecontainer.FilterEventRecorder(kubeDeps.Recorder),
 				klet.livenessManager,
@@ -1202,6 +1226,13 @@ func (kl *Kubelet) Run(updates <-chan kubetypes.PodUpdate) {
 	kl.syncLoop(updates, kl)
 }
 
+// GetKubeClient returns the Kubernetes client.
+// TODO: This is currently only required by network plugins. Replace
+// with more specific methods.
+func (kl *Kubelet) GetKubeClient() clientset.Interface {
+	return kl.kubeClient
+}
+
 // GetClusterDNS returns a list of the DNS servers and a list of the DNS search
 // domains of the cluster.
 func (kl *Kubelet) GetClusterDNS(pod *api.Pod) ([]string, []string, error) {

pkg/kubelet/kubelet_network.go

@@ -191,7 +191,20 @@ func (kl *Kubelet) cleanupBandwidthLimits(allPods []*api.Pod) error {
 
 // syncNetworkStatus updates the network state
 func (kl *Kubelet) syncNetworkStatus() {
-	kl.runtimeState.setNetworkState(kl.networkPlugin.Status())
+	// TODO(#35701): cri shim handles network plugin but we currently
+	// don't have a cri status hook, so network plugin status isn't
+	// reported if --experimental-runtime-integration=cri. This isn't
+	// too bad, because kubenet is the only network plugin that
+	// implements status(), and it just checks for plugin binaries
+	// on the filesystem.
+	if kl.networkPlugin != nil {
+		kl.runtimeState.setNetworkState(kl.networkPlugin.Status())
+	} else if kl.runtimeState.podCIDR() != "" {
+		// Don't mark the node ready till we've successfully executed
+		// the first UpdatePodCIDR call through cri. See comment above
+		// setPodCIDR call.
+		kl.runtimeState.setNetworkState(nil)
+	}
 }
 
 // updatePodCIDR updates the pod CIDR in the runtime state if it is different
@@ -203,14 +216,26 @@ func (kl *Kubelet) updatePodCIDR(cidr string) {
 		return
 	}
 
-	glog.Infof("Setting Pod CIDR: %v -> %v", podCIDR, cidr)
-	kl.runtimeState.setPodCIDR(cidr)
-
+	// kubelet -> network plugin
+	// cri runtime shims are responsible for their own network plugins
 	if kl.networkPlugin != nil {
 		details := make(map[string]interface{})
 		details[network.NET_PLUGIN_EVENT_POD_CIDR_CHANGE_DETAIL_CIDR] = cidr
 		kl.networkPlugin.Event(network.NET_PLUGIN_EVENT_POD_CIDR_CHANGE, details)
 	}
+
+	// kubelet -> generic runtime -> runtime shim -> network plugin
+	// docker/rkt non-cri implementations have a passthrough UpdatePodCIDR
+	if err := kl.GetRuntime().UpdatePodCIDR(cidr); err != nil {
+		glog.Errorf("Failed to update pod CIDR: %v", err)
+		return
+	}
+
+	// We need to be careful about setting podCIDR. Till #35839 lands we're
+	// using it to indicate network plugin status for cri shims. See comment
+	// in syncNetworkStatus.
+	glog.Infof("Setting Pod CIDR: %v -> %v", podCIDR, cidr)
+	kl.runtimeState.setPodCIDR(cidr)
 }
 
 // shapingEnabled returns whether traffic shaping is enabled.
@@ -219,6 +244,16 @@ func (kl *Kubelet) shapingEnabled() bool {
 	if kl.networkPlugin != nil && kl.networkPlugin.Capabilities().Has(network.NET_PLUGIN_CAPABILITY_SHAPING) {
 		return false
 	}
+	// This is not strictly true but we need to figure out how to handle
+	// bandwidth shaping anyway. If the kubelet doesn't have a networkPlugin,
+	// it could mean:
+	// a. the kubelet is responsible for bandwidth shaping
+	// b. the kubelet is using cri, and the cri has a network plugin
+	// Today, the only plugin that understands bandwidth shaping is kubenet, and
+	// it doesn't support bandwidth shaping when invoked through cri, so it
+	// effectively boils down to letting the kubelet decide how to handle
+	// shaping annotations. The combination of (cri + network plugin that
+	// handles bandwidth shaping) may not work because of this.
 	return true
 }
 

pkg/kubelet/kuberuntime/kuberuntime_manager.go

@@ -641,41 +641,16 @@ func (m *kubeGenericRuntimeManager) SyncPod(pod *api.Pod, _ api.PodStatus, podSt
 			return
 		}
 
-		setupNetworkResult := kubecontainer.NewSyncResult(kubecontainer.SetupNetwork, podSandboxID)
-		result.AddSyncResult(setupNetworkResult)
-		if !kubecontainer.IsHostNetworkPod(pod) {
-			glog.V(3).Infof("Calling network plugin %s to setup pod for %s", m.networkPlugin.Name(), format.Pod(pod))
-			// Setup pod network plugin with sandbox id
-			// TODO: rename the last param to sandboxID
-			err = m.networkPlugin.SetUpPod(pod.Namespace, pod.Name, kubecontainer.ContainerID{
-				Type: m.runtimeName,
-				ID:   podSandboxID,
-			})
-			if err != nil {
-				message := fmt.Sprintf("Failed to setup network for pod %q using network plugins %q: %v", format.Pod(pod), m.networkPlugin.Name(), err)
-				setupNetworkResult.Fail(kubecontainer.ErrSetupNetwork, message)
-				glog.Error(message)
-
-				killPodSandboxResult := kubecontainer.NewSyncResult(kubecontainer.KillPodSandbox, format.Pod(pod))
-				result.AddSyncResult(killPodSandboxResult)
-				if err := m.runtimeService.StopPodSandbox(podSandboxID); err != nil {
-					killPodSandboxResult.Fail(kubecontainer.ErrKillPodSandbox, err.Error())
-					glog.Errorf("Kill sandbox %q failed for pod %q: %v", podSandboxID, format.Pod(pod), err)
-				}
-				return
-			}
-
-			podSandboxStatus, err := m.runtimeService.PodSandboxStatus(podSandboxID)
-			if err != nil {
-				glog.Errorf("Failed to get pod sandbox status: %v; Skipping pod %q", err, format.Pod(pod))
-				result.Fail(err)
-				return
-			}
-
-			// Overwrite the podIP passed in the pod status, since we just started the infra container.
-			podIP = m.determinePodSandboxIP(pod.Namespace, pod.Name, podSandboxStatus)
-			glog.V(4).Infof("Determined the ip %q for pod %q after sandbox changed", podIP, format.Pod(pod))
+		podSandboxStatus, err := m.runtimeService.PodSandboxStatus(podSandboxID)
+		if err != nil {
+			glog.Errorf("Failed to get pod sandbox status: %v; Skipping pod %q", err, format.Pod(pod))
+			result.Fail(err)
+			return
 		}
+
+		// Overwrite the podIP passed in the pod status, since we just started the pod sandbox.
+		podIP = m.determinePodSandboxIP(pod.Namespace, pod.Name, podSandboxStatus)
+		glog.V(4).Infof("Determined the ip %q for pod %q after sandbox changed", podIP, format.Pod(pod))
 	}
 
 	// Get podSandboxConfig for containers to start.
@@ -815,33 +790,6 @@ func (m *kubeGenericRuntimeManager) killPodWithSyncResult(pod *api.Pod, runningP
 		result.AddSyncResult(containerResult)
 	}
 
-	// Teardown network plugin
-	if len(runningPod.Sandboxes) == 0 {
-		glog.V(4).Infof("Can not find pod sandbox by UID %q, assuming already removed.", runningPod.ID)
-		return
-	}
-
-	sandboxID := runningPod.Sandboxes[0].ID.ID
-	isHostNetwork, err := m.isHostNetwork(sandboxID, pod)
-	if err != nil {
-		result.Fail(err)
-		return
-	}
-	if !isHostNetwork {
-		teardownNetworkResult := kubecontainer.NewSyncResult(kubecontainer.TeardownNetwork, runningPod.ID)
-		result.AddSyncResult(teardownNetworkResult)
-		// Tear down network plugin with sandbox id
-		if err := m.networkPlugin.TearDownPod(runningPod.Namespace, runningPod.Name, kubecontainer.ContainerID{
-			Type: m.runtimeName,
-			ID:   sandboxID,
-		}); err != nil {
-			message := fmt.Sprintf("Failed to teardown network for pod %s_%s(%s) using network plugins %q: %v",
-				runningPod.Name, runningPod.Namespace, runningPod.ID, m.networkPlugin.Name(), err)
-			teardownNetworkResult.Fail(kubecontainer.ErrTeardownNetwork, message)
-			glog.Error(message)
-		}
-	}
-
 	// stop sandbox, the sandbox will be removed in GarbageCollect
 	killSandboxResult := kubecontainer.NewSyncResult(kubecontainer.KillPodSandbox, runningPod.ID)
 	result.AddSyncResult(killSandboxResult)
@@ -1006,3 +954,17 @@ func (m *kubeGenericRuntimeManager) PortForward(pod *kubecontainer.Pod, port uin
 
 	return fmt.Errorf("not implemented")
 }
+
+// UpdatePodCIDR is just a passthrough method to update the runtimeConfig of the shim
+// with the podCIDR supplied by the kubelet.
+func (m *kubeGenericRuntimeManager) UpdatePodCIDR(podCIDR string) error {
+	// TODO(#35531): do we really want to write a method on this manager for each
+	// field of the config?
+	glog.Infof("updating runtime config through cri with podcidr %v", podCIDR)
+	return m.runtimeService.UpdateRuntimeConfig(
+		&runtimeApi.RuntimeConfig{
+			NetworkConfig: &runtimeApi.NetworkConfig{
+				PodCidr: &podCIDR,
+			},
+		})
+}

pkg/kubelet/kuberuntime/kuberuntime_sandbox.go

@@ -18,13 +18,13 @@ package kuberuntime
 
 import (
 	"fmt"
+	"net"
 	"sort"
 
 	"github.com/golang/glog"
 	"k8s.io/kubernetes/pkg/api"
 	runtimeApi "k8s.io/kubernetes/pkg/kubelet/api/v1alpha1/runtime"
 	kubecontainer "k8s.io/kubernetes/pkg/kubelet/container"
-	"k8s.io/kubernetes/pkg/kubelet/network"
 	"k8s.io/kubernetes/pkg/kubelet/types"
 	"k8s.io/kubernetes/pkg/kubelet/util/format"
 )
@@ -180,27 +180,16 @@ func (m *kubeGenericRuntimeManager) getKubeletSandboxes(all bool) ([]*runtimeApi
 }
 
 // determinePodSandboxIP determines the IP address of the given pod sandbox.
-// TODO: remove determinePodSandboxIP after networking is delegated to the container runtime.
 func (m *kubeGenericRuntimeManager) determinePodSandboxIP(podNamespace, podName string, podSandbox *runtimeApi.PodSandboxStatus) string {
-	ip := ""
-
-	if podSandbox.Network != nil {
-		ip = podSandbox.Network.GetIp()
+	if podSandbox.Network == nil {
+		glog.Warningf("Pod Sandbox status doesn't have network information, cannot report IP")
+		return ""
 	}
-
-	if m.networkPlugin.Name() != network.DefaultPluginName {
-		// TODO: podInfraContainerID in GetPodNetworkStatus() interface should be renamed to sandboxID
-		netStatus, err := m.networkPlugin.GetPodNetworkStatus(podNamespace, podName, kubecontainer.ContainerID{
-			Type: m.runtimeName,
-			ID:   podSandbox.GetId(),
-		})
-		if err != nil {
-			glog.Errorf("NetworkPlugin %s failed on the status hook for pod '%s' - %v", m.networkPlugin.Name(), kubecontainer.BuildPodFullName(podName, podNamespace), err)
-		} else if netStatus != nil {
-			ip = netStatus.IP.String()
-		}
+	ip := podSandbox.Network.GetIp()
+	if net.ParseIP(ip) == nil {
+		glog.Warningf("Pod Sandbox reported an unparseable IP %v", ip)
+		return ""
 	}
-
 	return ip
 }
 

pkg/kubelet/network/cni/cni.go

@@ -193,7 +193,7 @@ func (plugin *cniNetworkPlugin) SetUpPod(namespace string, name string, id kubec
 	if err := plugin.checkInitialized(); err != nil {
 		return err
 	}
-	netnsPath, err := plugin.host.GetRuntime().GetNetNS(id)
+	netnsPath, err := plugin.host.GetNetNS(id.ID)
 	if err != nil {
 		return fmt.Errorf("CNI failed to retrieve network namespace path: %v", err)
 	}
@@ -217,7 +217,7 @@ func (plugin *cniNetworkPlugin) TearDownPod(namespace string, name string, id ku
 	if err := plugin.checkInitialized(); err != nil {
 		return err
 	}
-	netnsPath, err := plugin.host.GetRuntime().GetNetNS(id)
+	netnsPath, err := plugin.host.GetNetNS(id.ID)
 	if err != nil {
 		return fmt.Errorf("CNI failed to retrieve network namespace path: %v", err)
 	}
@@ -228,7 +228,7 @@ func (plugin *cniNetworkPlugin) TearDownPod(namespace string, name string, id ku
 // TODO: Use the addToNetwork function to obtain the IP of the Pod. That will assume idempotent ADD call to the plugin.
 // Also fix the runtime's call to Status function to be done only in the case that the IP is lost, no need to do periodic calls
 func (plugin *cniNetworkPlugin) GetPodNetworkStatus(namespace string, name string, id kubecontainer.ContainerID) (*network.PodNetworkStatus, error) {
-	netnsPath, err := plugin.host.GetRuntime().GetNetNS(id)
+	netnsPath, err := plugin.host.GetNetNS(id.ID)
 	if err != nil {
 		return nil, fmt.Errorf("CNI failed to retrieve network namespace path: %v", err)
 	}

pkg/kubelet/network/cni/cni_test.go

@@ -138,6 +138,14 @@ func (fnh *fakeNetworkHost) GetRuntime() kubecontainer.Runtime {
 	return fnh.runtime
 }
 
+func (fnh *fakeNetworkHost) GetNetNS(containerID string) (string, error) {
+	return fnh.GetRuntime().GetNetNS(kubecontainer.ContainerID{Type: "test", ID: containerID})
+}
+
+func (fnh *fakeNetworkHost) SupportsLegacyFeatures() bool {
+	return true
+}
+
 func TestCNIPlugin(t *testing.T) {
 	// install some random plugin
 	pluginName := fmt.Sprintf("test%d", rand.Intn(1000))

pkg/kubelet/network/kubenet/kubenet_linux.go

@@ -334,6 +334,9 @@ func (plugin *kubenetNetworkPlugin) Capabilities() utilsets.Int {
 	return utilsets.NewInt(network.NET_PLUGIN_CAPABILITY_SHAPING)
 }
 
+// setup sets up networking through CNI using the given ns/name and sandbox ID.
+// TODO: Don't pass the pod to this method, it only needs it for bandwidth
+// shaping and hostport management.
 func (plugin *kubenetNetworkPlugin) setup(namespace string, name string, id kubecontainer.ContainerID, pod *api.Pod) error {
 	// Bring up container loopback interface
 	if _, err := plugin.addContainerToNetwork(plugin.loConfig, "lo", namespace, name, id); err != nil {
@@ -384,6 +387,14 @@ func (plugin *kubenetNetworkPlugin) setup(namespace string, name string, id kube
 		plugin.syncEbtablesDedupRules(macAddr)
 	}
 
+	plugin.podIPs[id] = ip4.String()
+
+	// The host can choose to not support "legacy" features. The remote
+	// shim doesn't support it (#35457), but the kubelet does.
+	if !plugin.host.SupportsLegacyFeatures() {
+		return nil
+	}
+
 	// The first SetUpPod call creates the bridge; get a shaper for the sake of
 	// initialization
 	shaper := plugin.shaper()
@@ -398,8 +409,6 @@ func (plugin *kubenetNetworkPlugin) setup(namespace string, name string, id kube
 		}
 	}
 
-	plugin.podIPs[id] = ip4.String()
-
 	// Open any hostports the pod's containers want
 	activePods, err := plugin.getActivePods()
 	if err != nil {
@@ -423,6 +432,7 @@ func (plugin *kubenetNetworkPlugin) SetUpPod(namespace string, name string, id k
 		glog.V(4).Infof("SetUpPod took %v for %s/%s", time.Since(start), namespace, name)
 	}()
 
+	// TODO: Entire pod object only required for bw shaping and hostport.
 	pod, ok := plugin.host.GetPodByName(namespace, name)
 	if !ok {
 		return fmt.Errorf("pod %q cannot be found", name)
@@ -440,15 +450,20 @@ func (plugin *kubenetNetworkPlugin) SetUpPod(namespace string, name string, id k
 			glog.V(4).Infof("Failed to clean up %s/%s after SetUpPod failure: %v", namespace, name, err)
 		}
 
-		// TODO: Remove this hack once we've figured out how to retrieve the netns
-		// of an exited container. Currently, restarting docker will leak a bunch of
-		// ips. This will exhaust available ip space unless we cleanup old ips. At the
-		// same time we don't want to try GC'ing them periodically as that could lead
-		// to a performance regression in starting pods. So on each setup failure, try
-		// GC on the assumption that the kubelet is going to retry pod creation, and
-		// when it does, there will be ips.
-		plugin.ipamGarbageCollection()
+		// TODO(#34278): Figure out if we need IP GC through the cri.
+		// The cri should always send us teardown events for stale sandboxes,
+		// this obviates the need for GC in the common case, for kubenet.
+		if plugin.host.SupportsLegacyFeatures() {
 
+			// TODO: Remove this hack once we've figured out how to retrieve the netns
+			// of an exited container. Currently, restarting docker will leak a bunch of
+			// ips. This will exhaust available ip space unless we cleanup old ips. At the
+			// same time we don't want to try GC'ing them periodically as that could lead
+			// to a performance regression in starting pods. So on each setup failure, try
+			// GC on the assumption that the kubelet is going to retry pod creation, and
+			// when it does, there will be ips.
+			plugin.ipamGarbageCollection()
+		}
 		return err
 	}
 
@@ -485,6 +500,12 @@ func (plugin *kubenetNetworkPlugin) teardown(namespace string, name string, id k
 		}
 	}
 
+	// The host can choose to not support "legacy" features. The remote
+	// shim doesn't support it (#35457), but the kubelet does.
+	if !plugin.host.SupportsLegacyFeatures() {
+		return utilerrors.NewAggregate(errList)
+	}
+
 	activePods, err := plugin.getActivePods()
 	if err == nil {
 		err = plugin.hostportHandler.SyncHostports(BridgeName, activePods)
@@ -533,7 +554,7 @@ func (plugin *kubenetNetworkPlugin) GetPodNetworkStatus(namespace string, name s
 		return &network.PodNetworkStatus{IP: net.ParseIP(podIP)}, nil
 	}
 
-	netnsPath, err := plugin.host.GetRuntime().GetNetNS(id)
+	netnsPath, err := plugin.host.GetNetNS(id.ID)
 	if err != nil {
 		return nil, fmt.Errorf("Kubenet failed to retrieve network namespace path: %v", err)
 	}
@@ -722,7 +743,7 @@ func podIsExited(p *kubecontainer.Pod) bool {
 }
 
 func (plugin *kubenetNetworkPlugin) buildCNIRuntimeConf(ifName string, id kubecontainer.ContainerID) (*libcni.RuntimeConf, error) {
-	netnsPath, err := plugin.host.GetRuntime().GetNetNS(id)
+	netnsPath, err := plugin.host.GetNetNS(id.ID)
 	if err != nil {
 		return nil, fmt.Errorf("Kubenet failed to retrieve network namespace path: %v", err)
 	}

pkg/kubelet/network/kubenet/kubenet_linux_test.go

@@ -229,4 +229,40 @@ func TestGenerateMacAddress(t *testing.T) {
 	}
 }
 
+// TestInvocationWithoutRuntime invokes the plugin without a runtime.
+// This is how kubenet is invoked from the cri.
+func TestTearDownWithoutRuntime(t *testing.T) {
+	fhost := nettest.NewFakeHost(nil)
+	fhost.Legacy = false
+	fhost.Runtime = nil
+	mockcni := &mock_cni.MockCNI{}
+
+	fexec := &exec.FakeExec{
+		CommandScript: []exec.FakeCommandAction{},
+		LookPathFunc: func(file string) (string, error) {
+			return fmt.Sprintf("/fake-bin/%s", file), nil
+		},
+	}
+
+	kubenet := newFakeKubenetPlugin(map[kubecontainer.ContainerID]string{}, fexec, fhost)
+	kubenet.cniConfig = mockcni
+	kubenet.iptables = ipttest.NewFake()
+
+	details := make(map[string]interface{})
+	details[network.NET_PLUGIN_EVENT_POD_CIDR_CHANGE_DETAIL_CIDR] = "10.0.0.1/24"
+	kubenet.Event(network.NET_PLUGIN_EVENT_POD_CIDR_CHANGE, details)
+
+	existingContainerID := kubecontainer.BuildContainerID("docker", "123")
+	kubenet.podIPs[existingContainerID] = "10.0.0.1"
+
+	mockcni.On("DelNetwork", mock.AnythingOfType("*libcni.NetworkConfig"), mock.AnythingOfType("*libcni.RuntimeConf")).Return(nil)
+
+	if err := kubenet.TearDownPod("namespace", "name", existingContainerID); err != nil {
+		t.Fatalf("Unexpected error in TearDownPod: %v", err)
+	}
+	// Assert that the CNI DelNetwork made it through and we didn't crash
+	// without a runtime.
+	mockcni.AssertExpectations(t)
+}
+
 //TODO: add unit test for each implementation of network plugin interface

pkg/kubelet/network/mock_network/network_plugins.go

@@ -55,6 +55,10 @@ func (_m *MockNetworkPlugin) Capabilities() sets.Int {
 	return ret0
 }
 
+func (_m *MockNetworkPlugin) Finish() {
+	_m.ctrl.Finish()
+}
+
 func (_mr *_MockNetworkPluginRecorder) Capabilities() *gomock.Call {
 	return _mr.mock.ctrl.RecordCall(_mr.mock, "Capabilities")
 }

pkg/kubelet/network/plugins.go

@@ -95,16 +95,53 @@ type PodNetworkStatus struct {
 	IP net.IP `json:"ip" description:"Primary IP address of the pod"`
 }
 
-// Host is an interface that plugins can use to access the kubelet.
-type Host interface {
+// LegacyHost implements the methods required by network plugins that
+// were directly invoked by the kubelet. Implementations of this interface
+// that do not wish to support these features can simply return false
+// to SupportsLegacyFeatures.
+type LegacyHost interface {
 	// Get the pod structure by its name, namespace
+	// Only used for hostport management and bw shaping
 	GetPodByName(namespace, name string) (*api.Pod, bool)
 
 	// GetKubeClient returns a client interface
+	// Only used in testing
 	GetKubeClient() clientset.Interface
 
 	// GetContainerRuntime returns the container runtime that implements the containers (e.g. docker/rkt)
+	// Only used for hostport management
 	GetRuntime() kubecontainer.Runtime
+
+	// SupportsLegacyFeaturs returns true if this host can support hostports
+	// and bandwidth shaping. Both will either get added to CNI or dropped,
+	// so differnt implementations can choose to ignore them.
+	SupportsLegacyFeatures() bool
+}
+
+// Host is an interface that plugins can use to access the kubelet.
+// TODO(#35457): get rid of this backchannel to the kubelet. The scope of
+// the back channel is restricted to host-ports/testing, and restricted
+// to kubenet. No other network plugin wrapper needs it. Other plugins
+// only require a way to access namespace information, which they can do
+// directly through the embedded NamespaceGetter.
+type Host interface {
+	// NamespaceGetter is a getter for sandbox namespace information.
+	// It's the only part of this interface that isn't currently deprecated.
+	NamespaceGetter
+
+	// LegacyHost contains methods that trap back into the Kubelet. Dependence
+	// *do not* add more dependencies in this interface. In a post-cri world,
+	// network plugins will be invoked by the runtime shim, and should only
+	// require NamespaceGetter.
+	LegacyHost
+}
+
+// NamespaceGetter is an interface to retrieve namespace information for a given
+// sandboxID. Typically implemented by runtime shims that are closely coupled to
+// CNI plugin wrappers like kubenet.
+type NamespaceGetter interface {
+	// GetNetNS returns network namespace information for the given containerID.
+	GetNetNS(containerID string) (string, error)
 }
 
 // InitNetworkPlugin inits the plugin that matches networkPluginName. Plugins must have unique names.

pkg/kubelet/network/testing/fake_host.go

@@ -27,11 +27,14 @@ import (
 )
 
 type fakeNetworkHost struct {
+	fakeNamespaceGetter
 	kubeClient clientset.Interface
+	Legacy     bool
+	Runtime    *containertest.FakeRuntime
 }
 
 func NewFakeHost(kubeClient clientset.Interface) *fakeNetworkHost {
-	host := &fakeNetworkHost{kubeClient: kubeClient}
+	host := &fakeNetworkHost{kubeClient: kubeClient, Legacy: true, Runtime: &containertest.FakeRuntime{}}
 	return host
 }
 
@@ -44,5 +47,17 @@ func (fnh *fakeNetworkHost) GetKubeClient() clientset.Interface {
 }
 
 func (nh *fakeNetworkHost) GetRuntime() kubecontainer.Runtime {
-	return &containertest.FakeRuntime{}
+	return nh.Runtime
+}
+
+func (nh *fakeNetworkHost) SupportsLegacyFeatures() bool {
+	return nh.Legacy
+}
+
+type fakeNamespaceGetter struct {
+	ns string
+}
+
+func (nh *fakeNamespaceGetter) GetNetNS(containerID string) (string, error) {
+	return nh.ns, nil
 }

pkg/kubelet/networks.go

@@ -24,6 +24,11 @@ import (
 
 // This just exports required functions from kubelet proper, for use by network
 // plugins.
+// TODO(#35457): get rid of this backchannel to the kubelet. The scope of
+// the back channel is restricted to host-ports/testing, and restricted
+// to kubenet. No other network plugin wrapper needs it. Other plugins
+// only require a way to access namespace information, which they can do
+// directly through the methods implemented by criNetworkHost.
 type networkHost struct {
 	kubelet *Kubelet
 }
@@ -39,3 +44,45 @@ func (nh *networkHost) GetKubeClient() clientset.Interface {
 func (nh *networkHost) GetRuntime() kubecontainer.Runtime {
 	return nh.kubelet.GetRuntime()
 }
+
+func (nh *networkHost) SupportsLegacyFeatures() bool {
+	return true
+}
+
+// criNetworkHost implements the part of network.Host required by the
+// cri (NamespaceGetter). It leechs off networkHost for all other
+// methods, because networkHost is slated for deletion.
+type criNetworkHost struct {
+	*networkHost
+}
+
+// GetNetNS returns the network namespace of the given containerID.
+// This method satisfies the network.NamespaceGetter interface for
+// networkHost. It's only meant to be used from network plugins
+// that are directly invoked by the kubelet (aka: legacy, pre-cri).
+// Any network plugin invoked by a cri must implement NamespaceGetter
+// to talk directly to the runtime instead.
+func (c *criNetworkHost) GetNetNS(containerID string) (string, error) {
+	return c.kubelet.GetRuntime().GetNetNS(kubecontainer.ContainerID{Type: "", ID: containerID})
+}
+
+// noOpLegacyHost implements the network.LegacyHost interface for the remote
+// runtime shim by just returning empties. It doesn't support legacy features
+// like host port and bandwidth shaping.
+type noOpLegacyHost struct{}
+
+func (n *noOpLegacyHost) GetPodByName(namespace, name string) (*api.Pod, bool) {
+	return nil, true
+}
+
+func (n *noOpLegacyHost) GetKubeClient() clientset.Interface {
+	return nil
+}
+
+func (n *noOpLegacyHost) GetRuntime() kubecontainer.Runtime {
+	return nil
+}
+
+func (nh *noOpLegacyHost) SupportsLegacyFeatures() bool {
+	return false
+}

pkg/kubelet/remote/remote_runtime.go

@@ -36,7 +36,7 @@ type RemoteRuntimeService struct {
 
 // NewRemoteRuntimeService creates a new internalApi.RuntimeService.
 func NewRemoteRuntimeService(addr string, connectionTimout time.Duration) (internalApi.RuntimeService, error) {
-	glog.V(3).Infof("Connecting to runtime service %s", addr)
+	glog.Infof("Connecting to runtime service %s", addr)
 	conn, err := grpc.Dial(addr, grpc.WithInsecure(), grpc.WithTimeout(connectionTimout), grpc.WithDialer(dial))
 	if err != nil {
 		glog.Errorf("Connect remote runtime %s failed: %v", addr, err)
@@ -319,6 +319,23 @@ func (r *RemoteRuntimeService) PortForward(req *runtimeApi.PortForwardRequest) (
 	return resp, nil
 }
 
+// UpdateRuntimeConfig updates the config of a runtime service. The only
+// update payload currently supported is the pod CIDR assigned to a node,
+// and the runtime service just proxies it down to the network plugin.
 func (r *RemoteRuntimeService) UpdateRuntimeConfig(runtimeConfig *runtimeApi.RuntimeConfig) error {
+	ctx, cancel := getContextWithTimeout(r.timeout)
+	defer cancel()
+
+	// Response doesn't contain anything of interest. This translates to an
+	// Event notification to the network plugin, which can't fail, so we're
+	// really looking to surface destination unreachable.
+	_, err := r.runtimeClient.UpdateRuntimeConfig(ctx, &runtimeApi.UpdateRuntimeConfigRequest{
+		RuntimeConfig: runtimeConfig,
+	})
+
+	if err != nil {
+		return err
+	}
+
 	return nil
 }

pkg/kubelet/rkt/rkt.go

@@ -2179,6 +2179,12 @@ func (r *Runtime) PortForward(pod *kubecontainer.Pod, port uint16, stream io.Rea
 	return command.Run()
 }
 
+// UpdatePodCIDR updates the runtimeconfig with the podCIDR.
+// Currently no-ops, just implemented to satisfy the cri.
+func (r *Runtime) UpdatePodCIDR(podCIDR string) error {
+	return nil
+}
+
 // appStateToContainerState converts rktapi.AppState to kubecontainer.ContainerState.
 func appStateToContainerState(state rktapi.AppState) kubecontainer.ContainerState {
 	switch state {