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[release-1.33] server: ensure CNI teardown prevents IP leaks with missing netns #9382

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Merged
merged 1 commit into from
Aug 6, 2025
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[release-1.33] server: ensure CNI teardown prevents IP leaks with missing netns #9382

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58 changes: 48 additions & 10 deletions server/sandbox_network.go
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,8 @@ import (
"fmt"
"math"
"os"
"path/filepath"
"strings"
"time"

cnitypes "github.com/containernetworking/cni/pkg/types"
Expand All @@ -18,6 +20,10 @@ import (
"github.com/cri-o/cri-o/server/metrics"
)

const (
cacheDir = "/var/lib/cni/results"
)

// networkStart sets up the sandbox's network and returns the pod IP on success
// or an error.
func (s *Server) networkStart(ctx context.Context, sb *sandbox.Sandbox) (podIPs []string, result cnitypes.Result, retErr error) {
Expand Down Expand Up @@ -185,43 +191,75 @@ func (s *Server) networkStop(ctx context.Context, sb *sandbox.Sandbox) error {
}

// Check if the network namespace file exists and is valid before attempting CNI teardown.
// If the file doesn't exist or is invalid, skip CNI teardown and mark network as stopped.
// If the file doesn't exist or is invalid, we should still attempt CNI teardown using cached information
// to prevent IP leaks, but we'll mark the network as stopped regardless of the outcome.
netnsValid := true

if podNetwork.NetNS != "" {
if _, statErr := os.Stat(podNetwork.NetNS); statErr != nil {
// Network namespace file doesn't exist, mark network as stopped and return success
log.Debugf(ctx, "Network namespace file %s does not exist for pod sandbox %s(%s), skipping CNI teardown",
// Network namespace file doesn't exist, but we should still attempt CNI teardown
log.Debugf(ctx, "Network namespace file %s does not exist for pod sandbox %s(%s), attempting CNI teardown with cached info",
podNetwork.NetNS, sb.Name(), sb.ID())

return sb.SetNetworkStopped(ctx, true)
}

if validateErr := s.validateNetworkNamespace(podNetwork.NetNS); validateErr != nil {
netnsValid = false
} else if validateErr := s.validateNetworkNamespace(podNetwork.NetNS); validateErr != nil {
// Network namespace file exists but is invalid (e.g., corrupted or fake file)
log.Warnf(ctx, "Network namespace file %s is invalid for pod sandbox %s(%s): %v, removing and skipping CNI teardown",
log.Warnf(ctx, "Network namespace file %s is invalid for pod sandbox %s(%s): %v, removing and attempting CNI teardown with cached info",
podNetwork.NetNS, sb.Name(), sb.ID(), validateErr)
s.cleanupNetns(ctx, podNetwork.NetNS, sb)

return sb.SetNetworkStopped(ctx, true)
netnsValid = false
}
}

// Always attempt CNI teardown to prevent IP leaks, even if netns is invalid.
if err := s.config.CNIPlugin().TearDownPodWithContext(stopCtx, podNetwork); err != nil {
log.Warnf(ctx, "Failed to destroy network for pod sandbox %s(%s): %v", sb.Name(), sb.ID(), err)

// If the network namespace exists but CNI teardown failed, try to clean it up.
if podNetwork.NetNS != "" {
if podNetwork.NetNS != "" && netnsValid {
if _, statErr := os.Stat(podNetwork.NetNS); statErr == nil {
// Clean up the netns file since CNI teardown failed.
s.cleanupNetns(ctx, podNetwork.NetNS, sb)
}
}

// Clean up CNI result files if CNI teardown failed.
s.cleanupCNIResultFiles(ctx, sb.ID())

// Even if CNI teardown failed, mark network as stopped to prevent retry loops.
if setErr := sb.SetNetworkStopped(ctx, true); setErr != nil {
log.Warnf(ctx, "Failed to set network stopped for pod sandbox %s(%s): %v", sb.Name(), sb.ID(), setErr)
}

return fmt.Errorf("network teardown failed for pod sandbox %s(%s): %w", sb.Name(), sb.ID(), err)
}

return sb.SetNetworkStopped(ctx, true)
}

// cleanupCNIResultFiles removes CNI result files for a given container ID.
// This is called when CNI teardown fails to prevent stale result files from accumulating.
func (s *Server) cleanupCNIResultFiles(ctx context.Context, containerID string) {
entries, err := os.ReadDir(cacheDir)
if err != nil {
log.Warnf(ctx, "Failed to read CNI cache directory %s: %v", cacheDir, err)

return
}

for _, entry := range entries {
if !entry.IsDir() && strings.Contains(entry.Name(), containerID) {
filePath := filepath.Join(cacheDir, entry.Name())
if err := os.Remove(filePath); err != nil {
log.Warnf(ctx, "Failed to remove CNI result file %s: %v", filePath, err)
} else {
log.Infof(ctx, "Cleaned up CNI result file %s for container %s", entry.Name(), containerID)
}
}
}
}

func (s *Server) newPodNetwork(ctx context.Context, sb *sandbox.Sandbox) (ocicni.PodNetwork, error) {
_, span := log.StartSpan(ctx)
defer span.End()
Expand Down
29 changes: 29 additions & 0 deletions test/network.bats
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Original file line number Diff line number Diff line change
Expand Up @@ -224,3 +224,32 @@ function check_networking() {
crictl stopp "$new_pod_id"
crictl rmp "$new_pod_id"
}

@test "CNI teardown called even with missing or invalid netns to prevent IP leaks" {
start_crio

pod_id=$(crictl runp "$TESTDATA"/sandbox_config.json)

# Get the network namespace path
NETNS_PATH=/var/run/netns/
NS=$(crictl inspectp "$pod_id" |
jq -er '.info.runtimeSpec.linux.namespaces[] | select(.type == "network").path | sub("'$NETNS_PATH'"; "")')

output=$(crictl inspectp "$pod_id" | jq -r '.status.state')
[[ "$output" == "SANDBOX_READY" ]]

# Stop the pod first to release the network namespace.
crictl stopp "$pod_id"

# Now remove the network namespace file to simulate the issue.
rm -f "$NETNS_PATH$NS"

# Remove the pod - this should still call CNI teardown.
crictl rmp "$pod_id"

# Verify CNI teardown was called by checking logs.
grep -q "Deleting pod.*from CNI network" "$CRIO_LOG"

# Verify the pod is gone.
run ! crictl inspectp "$pod_id"
}
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