Merge pull request kubernetes#125866 from aroradaman/can-use-nfacct

nfacct: conditionally ensure counters and register metrics

Author: k8s-ci-robot

pkg/proxy/iptables/proxier.go

@@ -280,7 +280,7 @@ func NewProxier(ctx context.Context,
 	serviceHealthServer := healthcheck.NewServiceHealthServer(hostname, recorder, nodePortAddresses, healthzServer)
 	nfacctRunner, err := nfacct.New()
 	if err != nil {
-		logger.Error(err, "Failed to create nfacct runner")
+		logger.Error(err, "Failed to create nfacct runner, nfacct based metrics won't be available")
 	}
 
 	proxier := &Proxier{

pkg/proxy/metrics/metrics.go

@@ -299,8 +299,12 @@ func RegisterMetrics(mode kubeproxyconfig.ProxyMode) {
 
 		switch mode {
 		case kubeproxyconfig.ProxyModeIPTables:
-			legacyregistry.CustomMustRegister(iptablesCTStateInvalidDroppedMetricCollector)
-			legacyregistry.CustomMustRegister(localhostNodePortsAcceptedMetricsCollector)
+			if iptablesCTStateInvalidDroppedMetricCollector != nil {
+				legacyregistry.CustomMustRegister(iptablesCTStateInvalidDroppedMetricCollector)
+			}
+			if localhostNodePortsAcceptedMetricsCollector != nil {
+				legacyregistry.CustomMustRegister(localhostNodePortsAcceptedMetricsCollector)
+			}
 			legacyregistry.MustRegister(SyncFullProxyRulesLatency)
 			legacyregistry.MustRegister(SyncPartialProxyRulesLatency)
 			legacyregistry.MustRegister(IPTablesRestoreFailuresTotal)
@@ -332,6 +336,7 @@ func newNFAcctMetricCollector(counter string, description *metrics.Desc) *nfacct
 	client, err := nfacct.New()
 	if err != nil {
 		klog.ErrorS(err, "failed to initialize nfacct client")
+		return nil
 	}
 	return &nfacctMetricCollector{
 		client:      client,

pkg/proxy/util/nfacct/nfacct_linux.go

@@ -59,13 +59,26 @@ type runner struct {
 	handler handler
 }
 
-// New returns a new Interface.
+// New returns a new Interface. If the netfilter_nfacct subsystem is
+// not available in the kernel it will return error.
 func New() (Interface, error) {
 	hndlr, err := newNetlinkHandler()
 	if err != nil {
 		return nil, err
 	}
-	return newInternal(hndlr)
+
+	rnr, err := newInternal(hndlr)
+	if err != nil {
+		return nil, err
+	}
+
+	// check if nfacct is supported on the current kernel by attempting to retrieve a counter.
+	// the following GET call should either succeed or return ENOENT.
+	_, err = rnr.Get("IMayExist")
+	if err != nil && !errors.Is(err, ErrObjectNotFound) {
+		return nil, ErrNotSupported
+	}
+	return rnr, nil
 }
 
 // newInternal returns a new Interface with the given handler.
@@ -155,6 +168,7 @@ var ErrObjectAlreadyExists = errors.New("object already exists")
 var ErrNameExceedsMaxLength = fmt.Errorf("object name exceeds the maximum allowed length of %d characters", MaxLength)
 var ErrEmptyName = errors.New("object name cannot be empty")
 var ErrUnexpected = errors.New("unexpected error")
+var ErrNotSupported = errors.New("nfacct sub-system not available")
 
 func handleError(err error) error {
 	switch {