Revert "ci: Drop docker tests"

This reverts commit d82eb8d0f1.

.github/workflows/basic-ci-amd64.yaml

@@ -269,6 +269,50 @@ jobs:
         timeout-minutes: 15
         run: bash tests/functional/vfio/gha-run.sh run
 
+  run-docker-tests:
+    name: run-docker-tests
+    strategy:
+      # We can set this to true whenever we're 100% sure that
+      # all the tests are not flaky, otherwise we'll fail them
+      # all due to a single flaky instance.
+      fail-fast: false
+      matrix:
+        vmm:
+          - qemu
+    runs-on: ubuntu-22.04
+    env:
+      KATA_HYPERVISOR: ${{ matrix.vmm }}
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+        with:
+          ref: ${{ inputs.commit-hash }}
+          fetch-depth: 0
+          persist-credentials: false
+
+      - name: Rebase atop of the latest target branch
+        run: |
+          ./tests/git-helper.sh "rebase-atop-of-the-latest-target-branch"
+        env:
+          TARGET_BRANCH: ${{ inputs.target-branch }}
+
+      - name: Install dependencies
+        run: bash tests/integration/docker/gha-run.sh install-dependencies
+        env:
+          GH_TOKEN: ${{ github.token }}
+
+      - name: get-kata-tarball
+        uses: actions/download-artifact@d3f86a106a0bac45b974a628896c90dbdf5c8093 # v4.3.0
+        with:
+          name: kata-static-tarball-amd64${{ inputs.tarball-suffix }}
+          path: kata-artifacts
+
+      - name: Install kata
+        run: bash tests/integration/docker/gha-run.sh install-kata kata-artifacts
+
+      - name: Run docker smoke test
+        timeout-minutes: 5
+        run: bash tests/integration/docker/gha-run.sh run
+
   run-nerdctl-tests:
     name: run-nerdctl-tests
     strategy:

.github/workflows/basic-ci-s390x.yaml

@@ -123,3 +123,44 @@ jobs:
       - name: Run containerd-stability tests
         timeout-minutes: 15
         run: bash tests/stability/gha-run.sh run
+
+  run-docker-tests:
+    name: run-docker-tests
+    strategy:
+      # We can set this to true whenever we're 100% sure that
+      # all the tests are not flaky, otherwise we'll fail them
+      # all due to a single flaky instance.
+      fail-fast: false
+      matrix:
+        vmm: ['qemu']
+    runs-on: s390x-large
+    env:
+      KATA_HYPERVISOR: ${{ matrix.vmm }}
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+        with:
+          ref: ${{ inputs.commit-hash }}
+          fetch-depth: 0
+          persist-credentials: false
+
+      - name: Rebase atop of the latest target branch
+        run: |
+          ./tests/git-helper.sh "rebase-atop-of-the-latest-target-branch"
+        env:
+          TARGET_BRANCH: ${{ inputs.target-branch }}
+
+      - name: Install dependencies
+        run: bash tests/integration/docker/gha-run.sh install-dependencies
+
+      - name: get-kata-tarball
+        uses: actions/download-artifact@d3f86a106a0bac45b974a628896c90dbdf5c8093 # v4.3.0
+        with:
+          name: kata-static-tarball-s390x${{ inputs.tarball-suffix }}
+          path: kata-artifacts
+
+      - name: Install kata
+        run: bash tests/integration/docker/gha-run.sh install-kata kata-artifacts
+
+      - name: Run docker smoke test
+        timeout-minutes: 5
+        run: bash tests/integration/docker/gha-run.sh run

src/runtime-rs/crates/hypervisor/src/firecracker/fc_api.rs

@@ -111,7 +111,7 @@ impl FcInner {
 
         let body_config: String = json!({
             "mem_size_mib": self.config.memory_info.default_memory,
-            "vcpu_count": self.config.cpu_info.default_vcpus,
+            "vcpu_count": self.config.cpu_info.default_vcpus.ceil() as u8,
         })
         .to_string();
         let body_kernel: String = json!({
@@ -191,13 +191,10 @@ impl FcInner {
                 .disk_rate_limiter_ops_one_time_burst,
         );
 
-        let rate_limiter = serde_json::to_string(&block_rate_limit)
-            .with_context(|| format!("serde {block_rate_limit:?} to json"))?;
-
         let body: String = json!({
             "drive_id": format!("drive{drive_id}"),
             "path_on_host": new_drive_path,
-            "rate_limiter": rate_limiter,
+            "rate_limiter": block_rate_limit,
         })
         .to_string();
         self.request_with_retry(

src/runtime/pkg/containerd-shim-v2/start.go

@@ -9,9 +9,9 @@ import (
 	"context"
 	"fmt"
 
+	"github.com/containerd/containerd/api/types/task"
 	"github.com/sirupsen/logrus"
 
-	"github.com/containerd/containerd/api/types/task"
 	"github.com/kata-containers/kata-containers/src/runtime/pkg/katautils"
 )
 
@@ -46,6 +46,19 @@ func startContainer(ctx context.Context, s *service, c *container) (retErr error
 		}
 		go watchSandbox(ctx, s)
 
+		// If no network endpoints were discovered during sandbox creation,
+		// schedule an async rescan. This handles runtimes that configure
+		// networking after task creation (e.g. Docker 26+ configures
+		// networking after the Start response, and prestart hooks may
+		// not have run yet on slower architectures).
+		// RescanNetwork is idempotent — it returns immediately if
+		// endpoints already exist.
+		go func() {
+			if err := s.sandbox.RescanNetwork(s.ctx); err != nil {
+				shimLog.WithError(err).Error("async network rescan failed — container may lack networking")
+			}
+		}()
+
 		// We use s.ctx(`ctx` derived from `s.ctx`) to check for cancellation of the
 		// shim context and the context passed to startContainer for tracing.
 		go watchOOMEvents(ctx, s)

src/runtime/pkg/katautils/create.go

@@ -19,6 +19,7 @@ import (
 	vc "github.com/kata-containers/kata-containers/src/runtime/virtcontainers"
 	vf "github.com/kata-containers/kata-containers/src/runtime/virtcontainers/factory"
 	vcAnnotations "github.com/kata-containers/kata-containers/src/runtime/virtcontainers/pkg/annotations"
+	"github.com/kata-containers/kata-containers/src/runtime/virtcontainers/utils"
 	specs "github.com/opencontainers/runtime-spec/specs-go"
 )
 
@@ -140,6 +141,17 @@ func CreateSandbox(ctx context.Context, vci vc.VC, ociSpec specs.Spec, runtimeCo
 		sandboxConfig.Containers[0].RootFs = rootFs
 	}
 
+	// Docker 26+ may set up networking before task creation instead of using
+	// prestart hooks. The netns path is not in the OCI spec but can be
+	// discovered from Docker's libnetwork hook args which contain the sandbox
+	// ID that maps to /var/run/docker/netns/<sandbox_id>.
+	if sandboxConfig.NetworkConfig.NetworkID == "" && !sandboxConfig.NetworkConfig.DisableNewNetwork {
+		if dockerNetns := utils.DockerNetnsPath(&ociSpec); dockerNetns != "" {
+			sandboxConfig.NetworkConfig.NetworkID = dockerNetns
+			kataUtilsLogger.WithField("netns", dockerNetns).Info("discovered Docker network namespace from hook args")
+		}
+	}
+
 	// Important to create the network namespace before the sandbox is
 	// created, because it is not responsible for the creation of the
 	// netns if it does not exist.

src/runtime/pkg/katautils/network_linux.go

@@ -20,7 +20,9 @@ import (
 	"golang.org/x/sys/unix"
 )
 
-const procMountInfoFile = "/proc/self/mountinfo"
+const (
+	procMountInfoFile = "/proc/self/mountinfo"
+)
 
 // EnterNetNS is free from any call to a go routine, and it calls
 // into runtime.LockOSThread(), meaning it won't be executed in a
@@ -29,27 +31,30 @@ func EnterNetNS(networkID string, cb func() error) error {
 	return vc.EnterNetNS(networkID, cb)
 }
 
-// SetupNetworkNamespace create a network namespace
+// SetupNetworkNamespace creates a network namespace if one is not already
+// provided via NetworkID. When NetworkID is empty and networking is not
+// disabled, a new namespace is created as a placeholder; the actual
+// hypervisor namespace will be discovered later by addAllEndpoints after
+// the VM has started.
 func SetupNetworkNamespace(config *vc.NetworkConfig) error {
 	if config.DisableNewNetwork {
 		kataUtilsLogger.Info("DisableNewNetNs is on, shim and hypervisor are running in the host netns")
 		return nil
 	}
 
-	var err error
-	var n ns.NetNS
-
 	if config.NetworkID == "" {
+		var (
+			err error
+			n   ns.NetNS
+		)
+
 		if rootless.IsRootless() {
 			n, err = rootless.NewNS()
-			if err != nil {
-				return err
-			}
 		} else {
 			n, err = testutils.NewNS()
-			if err != nil {
-				return err
-			}
+		}
+		if err != nil {
+			return err
 		}
 
 		config.NetworkID = n.Path()
@@ -71,11 +76,23 @@ func SetupNetworkNamespace(config *vc.NetworkConfig) error {
 }
 
 const (
-	netNsMountType    = "nsfs"
-	mountTypeFieldIdx = 8
-	mountDestIdx      = 4
+	netNsMountType = "nsfs"
+	mountDestIdx   = 4
 )
 
+// mountinfoFsType finds the filesystem type in a parsed mountinfo line.
+// The mountinfo format has optional tagged fields (shared:, master:, etc.)
+// between field 7 and a "-" separator. The fs type is the field immediately
+// after "-". Returns "" if the separator is not found.
+func mountinfoFsType(fields []string) string {
+	for i, f := range fields {
+		if f == "-" && i+1 < len(fields) {
+			return fields[i+1]
+		}
+	}
+	return ""
+}
+
 // getNetNsFromBindMount returns the network namespace for the bind-mounted path
 func getNetNsFromBindMount(nsPath string, procMountFile string) (string, error) {
 	// Resolve all symlinks in the path as the mountinfo file contains
@@ -100,16 +117,15 @@ func getNetNsFromBindMount(nsPath string, procMountFile string) (string, error)
 		// "711 26 0:3 net:[4026532009] /run/docker/netns/default rw shared:535 - nsfs nsfs rw"
 		//
 		// Reference: https://www.kernel.org/doc/Documentation/filesystems/proc.txt
-
-		// We are interested in the first 9 fields of this file,
-		// to check for the correct mount type.
+		// The "-" separator has a variable position due to optional tagged
+		// fields, so we locate the fs type dynamically.
 		fields := strings.Split(text, " ")
 		if len(fields) < 9 {
 			continue
 		}
 
 		// We check here if the mount type is a network namespace mount type, namely "nsfs"
-		if fields[mountTypeFieldIdx] != netNsMountType {
+		if mountinfoFsType(fields) != netNsMountType {
 			continue
 		}
 

src/runtime/pkg/katautils/network_test.go

@@ -149,3 +149,23 @@ func TestSetupNetworkNamespace(t *testing.T) {
 	err = SetupNetworkNamespace(config)
 	assert.NoError(err)
 }
+
+func TestMountinfoFsType(t *testing.T) {
+	assert := assert.New(t)
+
+	// Standard mountinfo line with optional tagged fields
+	fields := []string{"711", "26", "0:3", "net:[4026532009]", "/run/docker/netns/default", "rw", "shared:535", "-", "nsfs", "nsfs", "rw"}
+	assert.Equal("nsfs", mountinfoFsType(fields))
+
+	// Multiple optional tags before separator
+	fields = []string{"711", "26", "0:3", "net:[4026532009]", "/run/docker/netns/default", "rw", "shared:535", "master:1", "-", "nsfs", "nsfs", "rw"}
+	assert.Equal("nsfs", mountinfoFsType(fields))
+
+	// No separator
+	fields = []string{"711", "26", "0:3", "net:[4026532009]", "/run/docker/netns/default", "rw"}
+	assert.Equal("", mountinfoFsType(fields))
+
+	// Separator at end (malformed)
+	fields = []string{"711", "26", "-"}
+	assert.Equal("", mountinfoFsType(fields))
+}

src/runtime/virtcontainers/interfaces.go

@@ -72,6 +72,8 @@ type VCSandbox interface {
 
 	GetOOMEvent(ctx context.Context) (string, error)
 	GetHypervisorPid() (int, error)
+	// RescanNetwork re-scans the network namespace for late-discovered endpoints.
+	RescanNetwork(ctx context.Context) error
 
 	UpdateRuntimeMetrics() error
 	GetAgentMetrics(ctx context.Context) (string, error)

src/runtime/virtcontainers/network_linux.go

@@ -17,9 +17,11 @@ import (
 	"runtime"
 	"sort"
 	"strconv"
+	"strings"
 	"time"
 
 	"github.com/containernetworking/plugins/pkg/ns"
+	"github.com/sirupsen/logrus"
 	"github.com/vishvananda/netlink"
 	"github.com/vishvananda/netns"
 	otelTrace "go.opentelemetry.io/otel/trace"
@@ -45,6 +47,11 @@ type LinuxNetwork struct {
 	interworkingModel NetInterworkingModel
 	netNSCreated      bool
 	danConfigPath     string
+	// placeholderNetNS holds the path to a placeholder network namespace
+	// that we created but later abandoned in favour of the hypervisor's
+	// netns. If best-effort deletion in addAllEndpoints fails, teardown
+	// retries the cleanup via RemoveEndpoints.
+	placeholderNetNS string
 }
 
 // NewNetwork creates a new Linux Network from a NetworkConfig.
@@ -68,11 +75,11 @@ func NewNetwork(configs ...*NetworkConfig) (Network, error) {
 	}
 
 	return &LinuxNetwork{
-		config.NetworkID,
-		[]Endpoint{},
-		config.InterworkingModel,
-		config.NetworkCreated,
-		config.DanConfigPath,
+		netNSPath:         config.NetworkID,
+		eps:               []Endpoint{},
+		interworkingModel: config.InterworkingModel,
+		netNSCreated:      config.NetworkCreated,
+		danConfigPath:     config.DanConfigPath,
 	}, nil
 }
 
@@ -325,28 +332,91 @@ func (n *LinuxNetwork) GetEndpointsNum() (int, error) {
 // Scan the networking namespace through netlink and then:
 // 1. Create the endpoints for the relevant interfaces found there.
 // 2. Attach them to the VM.
+//
+// If no usable interfaces are found and the hypervisor is running in a
+// different network namespace (e.g. Docker 26+ places QEMU in its own
+// pre-configured namespace), switch to the hypervisor's namespace and
+// rescan there. This handles the case where the OCI spec does not
+// communicate the network namespace path.
 func (n *LinuxNetwork) addAllEndpoints(ctx context.Context, s *Sandbox, hotplug bool) error {
-	netnsHandle, err := netns.GetFromPath(n.netNSPath)
+	endpoints, err := n.scanEndpointsInNs(ctx, s, n.netNSPath, hotplug)
 	if err != nil {
 		return err
 	}
+
+	// If the scan found no usable endpoints, check whether the
+	// hypervisor is running in a different namespace and retry there.
+	if len(endpoints) == 0 && s != nil {
+		if hypervisorNs, ok := n.detectHypervisorNetns(s); ok {
+			networkLogger().WithFields(logrus.Fields{
+				"original_netns":   n.netNSPath,
+				"hypervisor_netns": hypervisorNs,
+			}).Debug("no endpoints in original netns, switching to hypervisor netns")
+
+			origPath := n.netNSPath
+			origCreated := n.netNSCreated
+			n.netNSPath = hypervisorNs
+
+			_, err = n.scanEndpointsInNs(ctx, s, n.netNSPath, hotplug)
+			if err != nil {
+				n.netNSPath = origPath
+				n.netNSCreated = origCreated
+				return err
+			}
+
+			// Clean up the placeholder namespace we created — we're now
+			// using the hypervisor's namespace and the placeholder is empty.
+			// Only clear netNSCreated once deletion succeeds; on failure,
+			// stash the path so RemoveEndpoints can retry during teardown.
+			if origCreated {
+				if delErr := deleteNetNS(origPath); delErr != nil {
+					networkLogger().WithField("netns", origPath).WithError(delErr).Warn("failed to delete placeholder netns, will retry during teardown")
+					n.placeholderNetNS = origPath
+				}
+			}
+			// The hypervisor's namespace was not created by us.
+			n.netNSCreated = false
+		}
+	}
+
+	sort.Slice(n.eps, func(i, j int) bool {
+		return n.eps[i].Name() < n.eps[j].Name()
+	})
+
+	networkLogger().WithField("endpoints", n.eps).Info("endpoints found after scan")
+
+	return nil
+}
+
+// scanEndpointsInNs scans a network namespace for usable (non-loopback,
+// configured) interfaces and adds them as endpoints. Returns the list of
+// newly added endpoints.
+func (n *LinuxNetwork) scanEndpointsInNs(ctx context.Context, s *Sandbox, nsPath string, hotplug bool) ([]Endpoint, error) {
+	netnsHandle, err := netns.GetFromPath(nsPath)
+	if err != nil {
+		return nil, err
+	}
 	defer netnsHandle.Close()
 
 	netlinkHandle, err := netlink.NewHandleAt(netnsHandle)
 	if err != nil {
-		return err
+		return nil, err
 	}
 	defer netlinkHandle.Close()
 
 	linkList, err := netlinkHandle.LinkList()
 	if err != nil {
-		return err
+		return nil, err
 	}
 
+	epsBefore := len(n.eps)
+	var added []Endpoint
+
 	for _, link := range linkList {
 		netInfo, err := networkInfoFromLink(netlinkHandle, link)
 		if err != nil {
-			return err
+			// No rollback needed — no endpoints were added in this iteration yet.
+			return nil, err
 		}
 
 		// Ignore unconfigured network interfaces. These are
@@ -368,22 +438,62 @@ func (n *LinuxNetwork) addAllEndpoints(ctx context.Context, s *Sandbox, hotplug
 			continue
 		}
 
-		if err := doNetNS(n.netNSPath, func(_ ns.NetNS) error {
-			_, err = n.addSingleEndpoint(ctx, s, netInfo, hotplug)
-			return err
+		if err := doNetNS(nsPath, func(_ ns.NetNS) error {
+			ep, addErr := n.addSingleEndpoint(ctx, s, netInfo, hotplug)
+			if addErr == nil {
+				added = append(added, ep)
+			}
+			return addErr
 		}); err != nil {
-			return err
+			// Rollback: remove any endpoints added during this scan
+			// so that a failed scan does not leave partial side effects.
+			n.eps = n.eps[:epsBefore]
+			return nil, err
 		}
-
 	}
 
-	sort.Slice(n.eps, func(i, j int) bool {
-		return n.eps[i].Name() < n.eps[j].Name()
-	})
+	return added, nil
+}
 
-	networkLogger().WithField("endpoints", n.eps).Info("endpoints found after scan")
+// detectHypervisorNetns checks whether the hypervisor process is running in a
+// network namespace different from the one we are currently tracking. If so it
+// returns the procfs path to the hypervisor's netns and true.
+func (n *LinuxNetwork) detectHypervisorNetns(s *Sandbox) (string, bool) {
+	pid, err := s.GetHypervisorPid()
+	if err != nil || pid <= 0 {
+		return "", false
+	}
 
-	return nil
+	// Guard against PID recycling: verify the process belongs to this
+	// sandbox by checking its command line for the sandbox ID. QEMU is
+	// started with -name sandbox-<id>, so the ID will appear in cmdline.
+	// /proc/pid/cmdline uses null bytes as argument separators; replace
+	// them so the substring search works on the joined argument string.
+	cmdlineRaw, err := os.ReadFile(fmt.Sprintf("/proc/%d/cmdline", pid))
+	if err != nil {
+		return "", false
+	}
+	cmdline := strings.ReplaceAll(string(cmdlineRaw), "\x00", " ")
+	if !strings.Contains(cmdline, s.id) {
+		return "", false
+	}
+
+	hypervisorNs := fmt.Sprintf("/proc/%d/ns/net", pid)
+
+	// Compare device and inode numbers. Inode numbers are only unique
+	// within a device, so both must match to confirm the same namespace.
+	var currentStat, hvStat unix.Stat_t
+	if err := unix.Stat(n.netNSPath, &currentStat); err != nil {
+		return "", false
+	}
+	if err := unix.Stat(hypervisorNs, &hvStat); err != nil {
+		return "", false
+	}
+
+	if currentStat.Dev != hvStat.Dev || currentStat.Ino != hvStat.Ino {
+		return hypervisorNs, true
+	}
+	return "", false
 }
 
 func convertDanDeviceToNetworkInfo(device *vctypes.DanDevice) (*NetworkInfo, error) {
@@ -571,6 +681,17 @@ func (n *LinuxNetwork) RemoveEndpoints(ctx context.Context, s *Sandbox, endpoint
 		return deleteNetNS(n.netNSPath)
 	}
 
+	// Retry cleanup of a placeholder namespace whose earlier deletion
+	// failed in addAllEndpoints.
+	if n.placeholderNetNS != "" && endpoints == nil {
+		if delErr := deleteNetNS(n.placeholderNetNS); delErr != nil {
+			networkLogger().WithField("netns", n.placeholderNetNS).WithError(delErr).Warn("failed to delete placeholder netns during teardown")
+		} else {
+			networkLogger().WithField("netns", n.placeholderNetNS).Info("placeholder network namespace deleted")
+			n.placeholderNetNS = ""
+		}
+	}
+
 	return nil
 }
 

src/runtime/virtcontainers/network_linux_test.go

@@ -363,11 +363,11 @@ func TestConvertDanDeviceToNetworkInfo(t *testing.T) {
 func TestAddEndpoints_Dan(t *testing.T) {
 
 	network := &LinuxNetwork{
-		"net-123",
-		[]Endpoint{},
-		NetXConnectDefaultModel,
-		true,
-		"testdata/dan-config.json",
+		netNSPath:         "net-123",
+		eps:               []Endpoint{},
+		interworkingModel: NetXConnectDefaultModel,
+		netNSCreated:      true,
+		danConfigPath:     "testdata/dan-config.json",
 	}
 
 	ctx := context.TODO()

src/runtime/virtcontainers/pkg/vcmock/sandbox.go

@@ -255,6 +255,10 @@ func (s *Sandbox) GetHypervisorPid() (int, error) {
 	return 0, nil
 }
 
+func (s *Sandbox) RescanNetwork(ctx context.Context) error {
+	return nil
+}
+
 func (s *Sandbox) GuestVolumeStats(ctx context.Context, path string) ([]byte, error) {
 	return nil, nil
 }

src/runtime/virtcontainers/sandbox.go

@@ -20,6 +20,7 @@ import (
 	"strings"
 	"sync"
 	"syscall"
+	"time"
 
 	v1 "github.com/containerd/cgroups/stats/v1"
 	v2 "github.com/containerd/cgroups/v2/stats"
@@ -330,6 +331,81 @@ func (s *Sandbox) GetHypervisorPid() (int, error) {
 	return pids[0], nil
 }
 
+// RescanNetwork re-scans the network namespace for endpoints if none have
+// been discovered yet. This is idempotent: if endpoints already exist it
+// returns immediately. It enables Docker 26+ support where networking is
+// configured after task creation but before Start.
+//
+// Docker 26+ configures networking (veth pair, IP addresses) between
+// Create and Start. The interfaces may not be present immediately, so
+// this method polls until they appear or a timeout is reached.
+//
+// When new endpoints are found, the guest agent is informed about the
+// interfaces and routes so that networking becomes functional inside the VM.
+func (s *Sandbox) RescanNetwork(ctx context.Context) error {
+	if s.config.NetworkConfig.DisableNewNetwork {
+		return nil
+	}
+	if len(s.network.Endpoints()) > 0 {
+		return nil
+	}
+
+	const maxWait = 5 * time.Second
+	const pollInterval = 50 * time.Millisecond
+	deadline := time.NewTimer(maxWait)
+	defer deadline.Stop()
+	ticker := time.NewTicker(pollInterval)
+	defer ticker.Stop()
+
+	s.Logger().Debug("waiting for network interfaces in namespace")
+
+	for {
+		if _, err := s.network.AddEndpoints(ctx, s, nil, true); err != nil {
+			return err
+		}
+		if len(s.network.Endpoints()) > 0 {
+			return s.configureGuestNetwork(ctx)
+		}
+
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		case <-deadline.C:
+			s.Logger().Warn("no network interfaces found after timeout — networking may be configured by prestart hooks")
+			return nil
+		case <-ticker.C:
+		}
+	}
+}
+
+// configureGuestNetwork informs the guest agent about discovered network
+// endpoints so that interfaces and routes become functional inside the VM.
+func (s *Sandbox) configureGuestNetwork(ctx context.Context) error {
+	endpoints := s.network.Endpoints()
+	s.Logger().WithField("endpoints", len(endpoints)).Info("configuring hotplugged network in guest")
+
+	// Note: ARP neighbors (3rd return value) are not propagated here
+	// because the agent interface only exposes per-entry updates. The
+	// full setupNetworks path in kataAgent handles them; this path is
+	// only reached for late-discovered endpoints where neighbor entries
+	// are populated dynamically by the kernel.
+	interfaces, routes, _, err := generateVCNetworkStructures(ctx, endpoints)
+	if err != nil {
+		return fmt.Errorf("generating network structures: %w", err)
+	}
+	for _, ifc := range interfaces {
+		if _, err := s.agent.updateInterface(ctx, ifc); err != nil {
+			return fmt.Errorf("updating interface %s in guest: %w", ifc.Name, err)
+		}
+	}
+	if len(routes) > 0 {
+		if _, err := s.agent.updateRoutes(ctx, routes); err != nil {
+			return fmt.Errorf("updating routes in guest: %w", err)
+		}
+	}
+	return nil
+}
+
 // GetAllContainers returns all containers.
 func (s *Sandbox) GetAllContainers() []VCContainer {
 	ifa := make([]VCContainer, len(s.containers))

src/runtime/virtcontainers/utils/utils.go

@@ -12,6 +12,7 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"regexp"
 	"strings"
 	"syscall"
 	"time"
@@ -493,17 +494,38 @@ func RevertBytes(num uint64) uint64 {
 	return 1024*RevertBytes(a) + b
 }
 
+// dockerLibnetworkSetkey is the hook argument that identifies Docker's
+// network configuration hook. The argument following it is the sandbox ID.
+const dockerLibnetworkSetkey = "libnetwork-setkey"
+
+// dockerNetnsPrefixes are the well-known filesystem paths where the Docker
+// daemon bind-mounts container network namespaces.
+var dockerNetnsPrefixes = []string{"/var/run/docker/netns/", "/run/docker/netns/"}
+
+// validSandboxID matches Docker sandbox IDs: exactly 64 lowercase hex characters.
+var validSandboxID = regexp.MustCompile(`^[0-9a-f]{64}$`)
+
 // IsDockerContainer returns if the container is managed by docker
-// This is done by checking the prestart hook for `libnetwork` arguments.
+// This is done by checking the prestart and createRuntime hooks for
+// `libnetwork` arguments. Docker 26+ may use CreateRuntime hooks
+// instead of the deprecated Prestart hooks.
 func IsDockerContainer(spec *specs.Spec) bool {
 	if spec == nil || spec.Hooks == nil {
 		return false
 	}
 
-	for _, hook := range spec.Hooks.Prestart { //nolint:all
-		for _, arg := range hook.Args {
-			if strings.HasPrefix(arg, "libnetwork") {
-				return true
+	// Check both Prestart (Docker < 26) and CreateRuntime (Docker >= 26) hooks.
+	hookSets := [][]specs.Hook{
+		spec.Hooks.Prestart, //nolint:all
+		spec.Hooks.CreateRuntime,
+	}
+
+	for _, hooks := range hookSets {
+		for _, hook := range hooks {
+			for _, arg := range hook.Args {
+				if strings.HasPrefix(arg, "libnetwork") {
+					return true
+				}
 			}
 		}
 	}
@@ -511,6 +533,50 @@ func IsDockerContainer(spec *specs.Spec) bool {
 	return false
 }
 
+// DockerNetnsPath attempts to discover Docker's pre-created network namespace
+// path from OCI spec hooks. Docker's libnetwork-setkey hook contains the
+// sandbox ID as its second argument, which maps to the netns file under
+// /var/run/docker/netns/<sandbox_id>.
+func DockerNetnsPath(spec *specs.Spec) string {
+	if spec == nil || spec.Hooks == nil {
+		return ""
+	}
+
+	// Search both Prestart and CreateRuntime hooks for libnetwork-setkey.
+	hookSets := [][]specs.Hook{
+		spec.Hooks.Prestart, //nolint:all
+		spec.Hooks.CreateRuntime,
+	}
+
+	for _, hooks := range hookSets {
+		for _, hook := range hooks {
+			for i, arg := range hook.Args {
+				if arg == dockerLibnetworkSetkey && i+1 < len(hook.Args) {
+					sandboxID := hook.Args[i+1]
+					// Docker sandbox IDs are exactly 64 lowercase hex
+					// characters. Reject anything else to prevent path
+					// traversal and unexpected input.
+					if !validSandboxID.MatchString(sandboxID) {
+						continue
+					}
+					// Docker stores netns under well-known paths.
+					// Use Lstat to reject symlinks (which could point
+					// outside the Docker netns directory) and non-regular
+					// files such as directories.
+					for _, prefix := range dockerNetnsPrefixes {
+						nsPath := prefix + sandboxID
+						if fi, err := os.Lstat(nsPath); err == nil && fi.Mode().IsRegular() {
+							return nsPath
+						}
+					}
+				}
+			}
+		}
+	}
+
+	return ""
+}
+
 // GetGuestNUMANodes constructs guest NUMA nodes mapping to host NUMA nodes and host CPUs.
 func GetGuestNUMANodes(numaMapping []string) ([]types.GuestNUMANode, error) {
 	// Add guest NUMA node for each specified subsets of host NUMA nodes.

src/runtime/virtcontainers/utils/utils_test.go

@@ -579,24 +579,178 @@ func TestRevertBytes(t *testing.T) {
 	assert.Equal(expectedNum, num)
 }
 
+// TestIsDockerContainer validates hook-detection logic in isolation.
+// End-to-end Docker→containerd→kata integration is covered by
+// external tests (see tests/integration/kubernetes/).
 func TestIsDockerContainer(t *testing.T) {
 	assert := assert.New(t)
 
+	// nil spec
+	assert.False(IsDockerContainer(nil))
+
+	// nil hooks
+	assert.False(IsDockerContainer(&specs.Spec{}))
+
+	// Unrelated prestart hook
 	ociSpec := &specs.Spec{
 		Hooks: &specs.Hooks{
-			Prestart: []specs.Hook{
-				{
-					Args: []string{
-						"haha",
-					},
-				},
+			Prestart: []specs.Hook{ //nolint:all
+				{Args: []string{"haha"}},
 			},
 		},
 	}
 	assert.False(IsDockerContainer(ociSpec))
 
+	// Prestart hook with libnetwork (Docker < 26)
 	ociSpec.Hooks.Prestart = append(ociSpec.Hooks.Prestart, specs.Hook{ //nolint:all
 		Args: []string{"libnetwork-xxx"},
 	})
 	assert.True(IsDockerContainer(ociSpec))
+
+	// CreateRuntime hook with libnetwork (Docker >= 26)
+	ociSpec2 := &specs.Spec{
+		Hooks: &specs.Hooks{
+			CreateRuntime: []specs.Hook{
+				{Args: []string{"/usr/bin/docker-proxy", "libnetwork-setkey", "abc123", "ctrl"}},
+			},
+		},
+	}
+	assert.True(IsDockerContainer(ociSpec2))
+
+	// CreateRuntime hook without libnetwork
+	ociSpec3 := &specs.Spec{
+		Hooks: &specs.Hooks{
+			CreateRuntime: []specs.Hook{
+				{Args: []string{"/some/other/hook"}},
+			},
+		},
+	}
+	assert.False(IsDockerContainer(ociSpec3))
+}
+
+// TestDockerNetnsPath validates netns path discovery from OCI hook args.
+// This does not test the actual namespace opening or endpoint scanning;
+// see integration tests for full-path coverage.
+func TestDockerNetnsPath(t *testing.T) {
+	assert := assert.New(t)
+
+	// Valid 64-char hex sandbox IDs for test cases.
+	validID := strings.Repeat("ab", 32)   // 64 hex chars
+	validID2 := strings.Repeat("cd", 32)  // another 64 hex chars
+	invalidShortID := "abc123"             // too short
+	invalidUpperID := strings.Repeat("AB", 32) // uppercase rejected
+
+	// nil spec
+	assert.Equal("", DockerNetnsPath(nil))
+
+	// nil hooks
+	assert.Equal("", DockerNetnsPath(&specs.Spec{}))
+
+	// Hook without libnetwork-setkey
+	spec := &specs.Spec{
+		Hooks: &specs.Hooks{
+			Prestart: []specs.Hook{ //nolint:all
+				{Args: []string{"/some/binary", "unrelated"}},
+			},
+		},
+	}
+	assert.Equal("", DockerNetnsPath(spec))
+
+	// Prestart hook with libnetwork-setkey but sandbox ID too short (rejected by regex)
+	spec = &specs.Spec{
+		Hooks: &specs.Hooks{
+			Prestart: []specs.Hook{ //nolint:all
+				{Args: []string{"/usr/bin/proxy", "libnetwork-setkey", invalidShortID, "ctrl"}},
+			},
+		},
+	}
+	assert.Equal("", DockerNetnsPath(spec))
+
+	// Prestart hook with libnetwork-setkey but uppercase hex (rejected by regex)
+	spec = &specs.Spec{
+		Hooks: &specs.Hooks{
+			Prestart: []specs.Hook{ //nolint:all
+				{Args: []string{"/usr/bin/proxy", "libnetwork-setkey", invalidUpperID, "ctrl"}},
+			},
+		},
+	}
+	assert.Equal("", DockerNetnsPath(spec))
+
+	// Prestart hook with valid sandbox ID but netns file doesn't exist on disk
+	spec = &specs.Spec{
+		Hooks: &specs.Hooks{
+			Prestart: []specs.Hook{ //nolint:all
+				{Args: []string{"/usr/bin/proxy", "libnetwork-setkey", validID, "ctrl"}},
+			},
+		},
+	}
+	assert.Equal("", DockerNetnsPath(spec))
+
+	// Prestart hook with libnetwork-setkey and existing netns file — success path
+	tmpDir := t.TempDir()
+	fakeNsDir := filepath.Join(tmpDir, "netns")
+	err := os.MkdirAll(fakeNsDir, 0755)
+	assert.NoError(err)
+	fakeNsFile := filepath.Join(fakeNsDir, validID)
+	err = os.WriteFile(fakeNsFile, []byte{}, 0644)
+	assert.NoError(err)
+
+	// Temporarily override dockerNetnsPrefixes so DockerNetnsPath can find
+	// the netns file we created under the temp directory.
+	origPrefixes := dockerNetnsPrefixes
+	dockerNetnsPrefixes = []string{fakeNsDir + "/"}
+	defer func() { dockerNetnsPrefixes = origPrefixes }()
+
+	spec = &specs.Spec{
+		Hooks: &specs.Hooks{
+			Prestart: []specs.Hook{ //nolint:all
+				{Args: []string{"/usr/bin/proxy", "libnetwork-setkey", validID, "ctrl"}},
+			},
+		},
+	}
+	assert.Equal(fakeNsFile, DockerNetnsPath(spec))
+
+	// Sandbox ID that is a directory rather than a regular file — must be rejected
+	dirID := validID2
+	err = os.MkdirAll(filepath.Join(fakeNsDir, dirID), 0755)
+	assert.NoError(err)
+	spec = &specs.Spec{
+		Hooks: &specs.Hooks{
+			Prestart: []specs.Hook{ //nolint:all
+				{Args: []string{"/usr/bin/proxy", "libnetwork-setkey", dirID, "ctrl"}},
+			},
+		},
+	}
+	assert.Equal("", DockerNetnsPath(spec))
+
+	// CreateRuntime hook with valid sandbox ID — file doesn't exist
+	validID3 := strings.Repeat("ef", 32)
+	spec = &specs.Spec{
+		Hooks: &specs.Hooks{
+			CreateRuntime: []specs.Hook{
+				{Args: []string{"/usr/bin/proxy", "libnetwork-setkey", validID3, "ctrl"}},
+			},
+		},
+	}
+	assert.Equal("", DockerNetnsPath(spec))
+
+	// Hook with libnetwork-setkey as last arg (no sandbox ID follows) — no panic
+	spec = &specs.Spec{
+		Hooks: &specs.Hooks{
+			Prestart: []specs.Hook{ //nolint:all
+				{Args: []string{"libnetwork-setkey"}},
+			},
+		},
+	}
+	assert.Equal("", DockerNetnsPath(spec))
+
+	// Empty args slice
+	spec = &specs.Spec{
+		Hooks: &specs.Hooks{
+			Prestart: []specs.Hook{ //nolint:all
+				{Args: []string{}},
+			},
+		},
+	}
+	assert.Equal("", DockerNetnsPath(spec))
 }

tests/integration/docker/gha-run.sh

@@ -0,0 +1,45 @@
+#!/bin/bash
+#
+# Copyright (c) 2023 Intel Corporation
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+set -o errexit
+set -o nounset
+set -o pipefail
+
+kata_tarball_dir="${2:-kata-artifacts}"
+docker_dir="$(dirname "$(readlink -f "$0")")"
+source "${docker_dir}/../../common.bash"
+image="${image:-instrumentisto/nmap:latest}"
+
+function install_dependencies() {
+	info "Installing the dependencies needed for running the docker smoke test"
+
+	sudo -E docker pull "${image}"
+}
+
+function run() {
+	info "Running docker smoke test tests using ${KATA_HYPERVISOR} hypervisor"
+
+	enabling_hypervisor
+
+	info "Running docker with runc"
+	sudo docker run --rm --entrypoint nping "${image}" --tcp-connect -c 2 -p 80 www.github.com
+
+	info "Running docker with Kata Containers (${KATA_HYPERVISOR})"
+	sudo docker run --rm --runtime io.containerd.kata-${KATA_HYPERVISOR}.v2 --entrypoint nping "${image}" --tcp-connect -c 2 -p 80 www.github.com
+}
+
+function main() {
+	action="${1:-}"
+	case "${action}" in
+		install-dependencies) install_dependencies ;;
+		install-kata) install_kata ;;
+		run) run ;;
+		*) >&2 die "Invalid argument" ;;
+	esac
+}
+
+main "$@"