nftables accelerated datapath (flowtables)

The kernel implement a flowtables infrastructure that allow to accelerate packet forwarding using nftables. Since connections with a small number of packets will not benefit of the offloading, add a new option to the nftables kube-proxy so users can define the minimum number of packets required to offload a connection to the datapath. It also allow users to completely disable the behavior by setting this option to 0. By default connections with more than 20 packets are considered large connections and offloaded to the fastpath.
kubernetes · Dec 9, 2024 · a211e4b · a211e4b
1 parent 8ad9607
commit a211e4b
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Showing 13 changed files with 193 additions and 37 deletions.
diff --git a/cmd/kube-proxy/app/options.go b/cmd/kube-proxy/app/options.go
@@ -171,6 +171,8 @@ func (o *Options) AddFlags(fs *pflag.FlagSet) {
 	fs.Int32Var(&o.metricsPort, "metrics-port", o.metricsPort, "The port to bind the metrics server. Use 0 to disable.")
 	_ = fs.MarkDeprecated("metrics-port", "This flag is deprecated and will be removed in a future release. Please use --metrics-bind-address instead.")
 
+	fs.Int32Var(o.config.NFTables.FastpathPacketThreshold, "fastpath-packet-threshold", ptr.Deref(o.config.NFTables.FastpathPacketThreshold, 20),
+		"Number of packets required for the proxy to offload the connection to the fastpath. Use 0 to disable.")
 	logsapi.AddFlags(&o.config.Logging, fs)
 }
 

diff --git a/cmd/kube-proxy/app/server_linux.go b/cmd/kube-proxy/app/server_linux.go
@@ -305,6 +305,7 @@ func (s *ProxyServer) createProxier(ctx context.Context, config *proxyconfigapi.
 				s.Recorder,
 				s.HealthzServer,
 				config.NodePortAddresses,
+				int(*config.NFTables.FastpathPacketThreshold),
 				initOnly,
 			)
 		} else {
@@ -323,6 +324,7 @@ func (s *ProxyServer) createProxier(ctx context.Context, config *proxyconfigapi.
 				s.Recorder,
 				s.HealthzServer,
 				config.NodePortAddresses,
+				int(*config.NFTables.FastpathPacketThreshold),
 				initOnly,
 			)
 		}

diff --git a/pkg/generated/openapi/zz_generated.openapi.go b/pkg/generated/openapi/zz_generated.openapi.go
diff --git a/pkg/proxy/apis/config/scheme/testdata/KubeProxyConfiguration/after/v1alpha1.yaml b/pkg/proxy/apis/config/scheme/testdata/KubeProxyConfiguration/after/v1alpha1.yaml
@@ -52,6 +52,7 @@ logging:
 metricsBindAddress: 127.0.0.1:10249
 mode: ""
 nftables:
+  fastpathPacketThreshold: 20
   masqueradeAll: false
   masqueradeBit: 14
   minSyncPeriod: 0s

diff --git a/pkg/proxy/apis/config/scheme/testdata/KubeProxyConfiguration/roundtrip/default/v1alpha1.yaml b/pkg/proxy/apis/config/scheme/testdata/KubeProxyConfiguration/roundtrip/default/v1alpha1.yaml
@@ -52,6 +52,7 @@ logging:
 metricsBindAddress: 127.0.0.1:10249
 mode: ""
 nftables:
+  fastpathPacketThreshold: 20
   masqueradeAll: false
   masqueradeBit: 14
   minSyncPeriod: 0s

diff --git a/pkg/proxy/apis/config/types.go b/pkg/proxy/apis/config/types.go
@@ -83,6 +83,11 @@ type KubeProxyNFTablesConfiguration struct {
 	// masqueradeBit is the bit of the iptables fwmark space to use for SNAT if using
 	// the nftables proxy mode. Values must be within the range [0, 31].
 	MasqueradeBit *int32
+
+	// FastpathPacketThreshold is the number of packets untile the proxy starts offloading
+	// the connection to the fast path and skipping the kernel stack.
+	// Set to 0 to disable it.
+	FastpathPacketThreshold *int32
 }
 
 // KubeProxyConntrackConfiguration contains conntrack settings for

diff --git a/pkg/proxy/apis/config/v1alpha1/defaults.go b/pkg/proxy/apis/config/v1alpha1/defaults.go
@@ -132,6 +132,14 @@ func SetDefaults_KubeProxyConfiguration(obj *kubeproxyconfigv1alpha1.KubeProxyCo
 	if obj.ClientConnection.Burst == 0 {
 		obj.ClientConnection.Burst = 10
 	}
+	if obj.NFTables.FastpathPacketThreshold == nil {
+		// Number of packets required to offload the connection to the fastpath.
+		// Short connections will not benefit much from the switch to fastpath,
+		// so we consider that a connection that has exchanged more than 20 packets
+		// in each direction should be offloaded by default.
+		temp := int32(20)
+		obj.NFTables.FastpathPacketThreshold = &temp
+	}
 	if obj.FeatureGates == nil {
 		obj.FeatureGates = make(map[string]bool)
 	}

diff --git a/pkg/proxy/apis/config/v1alpha1/zz_generated.conversion.go b/pkg/proxy/apis/config/v1alpha1/zz_generated.conversion.go
diff --git a/pkg/proxy/apis/config/zz_generated.deepcopy.go b/pkg/proxy/apis/config/zz_generated.deepcopy.go
diff --git a/pkg/proxy/nftables/helpers_test.go b/pkg/proxy/nftables/helpers_test.go
@@ -32,7 +32,7 @@ import (
 	"github.com/google/go-cmp/cmp"
 	"github.com/lithammer/dedent"
 
-	"k8s.io/api/core/v1"
+	v1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/util/sets"
 	netutils "k8s.io/utils/net"
 	"sigs.k8s.io/knftables"
@@ -286,6 +286,9 @@ var ignoredRegexp = regexp.MustCompile(strings.Join(
 		// The trace tests only check new connections, so for our purposes, this
 		// check always succeeds (and thus can be ignored).
 		`^ct state new`,
+
+		// The trace tests does not check flowtables offloading
+		`^.*flow offload.*$`,
 	},
 	"|",
 ))

diff --git a/pkg/proxy/nftables/proxier.go b/pkg/proxy/nftables/proxier.go
@@ -37,6 +37,10 @@ import (
 	"sync/atomic"
 	"time"
 
+	"golang.org/x/time/rate"
+
+	"github.com/vishvananda/netlink"
+
 	v1 "k8s.io/api/core/v1"
 	discovery "k8s.io/api/discovery/v1"
 	"k8s.io/apimachinery/pkg/types"
@@ -101,6 +105,9 @@ const (
 	// masquerading
 	markMasqChain     = "mark-for-masquerade"
 	masqueradingChain = "masquerading"
+
+	// flowtables
+	serviceFlowTable = "kube-proxy-flowtable"
 )
 
 // NewDualStackProxier creates a MetaProxier instance, with IPv4 and IPv6 proxies.
@@ -116,21 +123,22 @@ func NewDualStackProxier(
 	recorder events.EventRecorder,
 	healthzServer *healthcheck.ProxierHealthServer,
 	nodePortAddresses []string,
+	fastpathPacketThreshold int,
 	initOnly bool,
 ) (proxy.Provider, error) {
 	// Create an ipv4 instance of the single-stack proxier
 	ipv4Proxier, err := NewProxier(ctx, v1.IPv4Protocol,
 		syncPeriod, minSyncPeriod, masqueradeAll, masqueradeBit,
 		localDetectors[v1.IPv4Protocol], hostname, nodeIPs[v1.IPv4Protocol],
-		recorder, healthzServer, nodePortAddresses, initOnly)
+		recorder, healthzServer, nodePortAddresses, fastpathPacketThreshold, initOnly)
 	if err != nil {
 		return nil, fmt.Errorf("unable to create ipv4 proxier: %v", err)
 	}
 
 	ipv6Proxier, err := NewProxier(ctx, v1.IPv6Protocol,
 		syncPeriod, minSyncPeriod, masqueradeAll, masqueradeBit,
 		localDetectors[v1.IPv6Protocol], hostname, nodeIPs[v1.IPv6Protocol],
-		recorder, healthzServer, nodePortAddresses, initOnly)
+		recorder, healthzServer, nodePortAddresses, fastpathPacketThreshold, initOnly)
 	if err != nil {
 		return nil, fmt.Errorf("unable to create ipv6 proxier: %v", err)
 	}
@@ -195,12 +203,13 @@ type Proxier struct {
 
 	logger klog.Logger
 
-	clusterIPs          *nftElementStorage
-	serviceIPs          *nftElementStorage
-	firewallIPs         *nftElementStorage
-	noEndpointServices  *nftElementStorage
-	noEndpointNodePorts *nftElementStorage
-	serviceNodePorts    *nftElementStorage
+	fastpathPacketThreshold int
+	clusterIPs              *nftElementStorage
+	serviceIPs              *nftElementStorage
+	firewallIPs             *nftElementStorage
+	noEndpointServices      *nftElementStorage
+	noEndpointNodePorts     *nftElementStorage
+	serviceNodePorts        *nftElementStorage
 }
 
 // Proxier implements proxy.Provider
@@ -221,6 +230,7 @@ func NewProxier(ctx context.Context,
 	recorder events.EventRecorder,
 	healthzServer *healthcheck.ProxierHealthServer,
 	nodePortAddressStrings []string,
+	fastpathPacketThreshold int,
 	initOnly bool,
 ) (*Proxier, error) {
 	logger := klog.LoggerWithValues(klog.FromContext(ctx), "ipFamily", ipFamily)
@@ -245,33 +255,34 @@ func NewProxier(ctx context.Context,
 	serviceHealthServer := healthcheck.NewServiceHealthServer(hostname, recorder, nodePortAddresses, healthzServer)
 
 	proxier := &Proxier{
-		ipFamily:            ipFamily,
-		svcPortMap:          make(proxy.ServicePortMap),
-		serviceChanges:      proxy.NewServiceChangeTracker(newServiceInfo, ipFamily, recorder, nil),
-		endpointsMap:        make(proxy.EndpointsMap),
-		endpointsChanges:    proxy.NewEndpointsChangeTracker(hostname, newEndpointInfo, ipFamily, recorder, nil),
-		needFullSync:        true,
-		syncPeriod:          syncPeriod,
-		nftables:            nft,
-		masqueradeAll:       masqueradeAll,
-		masqueradeMark:      masqueradeMark,
-		conntrack:           conntrack.New(),
-		localDetector:       localDetector,
-		hostname:            hostname,
-		nodeIP:              nodeIP,
-		recorder:            recorder,
-		serviceHealthServer: serviceHealthServer,
-		healthzServer:       healthzServer,
-		nodePortAddresses:   nodePortAddresses,
-		networkInterfacer:   proxyutil.RealNetwork{},
-		staleChains:         make(map[string]time.Time),
-		logger:              logger,
-		clusterIPs:          newNFTElementStorage("set", clusterIPsSet),
-		serviceIPs:          newNFTElementStorage("map", serviceIPsMap),
-		firewallIPs:         newNFTElementStorage("map", firewallIPsMap),
-		noEndpointServices:  newNFTElementStorage("map", noEndpointServicesMap),
-		noEndpointNodePorts: newNFTElementStorage("map", noEndpointNodePortsMap),
-		serviceNodePorts:    newNFTElementStorage("map", serviceNodePortsMap),
+		ipFamily:                ipFamily,
+		svcPortMap:              make(proxy.ServicePortMap),
+		serviceChanges:          proxy.NewServiceChangeTracker(newServiceInfo, ipFamily, recorder, nil),
+		endpointsMap:            make(proxy.EndpointsMap),
+		endpointsChanges:        proxy.NewEndpointsChangeTracker(hostname, newEndpointInfo, ipFamily, recorder, nil),
+		needFullSync:            true,
+		syncPeriod:              syncPeriod,
+		nftables:                nft,
+		masqueradeAll:           masqueradeAll,
+		masqueradeMark:          masqueradeMark,
+		conntrack:               conntrack.New(),
+		localDetector:           localDetector,
+		hostname:                hostname,
+		nodeIP:                  nodeIP,
+		recorder:                recorder,
+		serviceHealthServer:     serviceHealthServer,
+		healthzServer:           healthzServer,
+		nodePortAddresses:       nodePortAddresses,
+		networkInterfacer:       proxyutil.RealNetwork{},
+		staleChains:             make(map[string]time.Time),
+		logger:                  logger,
+		clusterIPs:              newNFTElementStorage("set", clusterIPsSet),
+		serviceIPs:              newNFTElementStorage("map", serviceIPsMap),
+		firewallIPs:             newNFTElementStorage("map", firewallIPsMap),
+		noEndpointServices:      newNFTElementStorage("map", noEndpointServicesMap),
+		noEndpointNodePorts:     newNFTElementStorage("map", noEndpointNodePortsMap),
+		serviceNodePorts:        newNFTElementStorage("map", serviceNodePortsMap),
+		fastpathPacketThreshold: fastpathPacketThreshold,
 	}
 
 	burstSyncs := 2
@@ -707,6 +718,21 @@ func (proxier *Proxier) setupNFTables(tx *knftables.Transaction) {
 		})
 	}
 
+	// Offload the connection after the defined number of packets
+	if proxier.fastpathPacketThreshold > 0 {
+		tx.Add(&knftables.Flowtable{
+			Name: serviceFlowTable,
+		})
+		tx.Add(&knftables.Rule{
+			Chain: filterForwardChain,
+			Rule: knftables.Concat(
+				"ct original", ipX, "daddr", "@", clusterIPsSet,
+				"ct packets >", proxier.fastpathPacketThreshold,
+				"flow offload", "@", serviceFlowTable,
+			),
+		})
+	}
+
 	// flush containers
 	proxier.clusterIPs.reset(tx)
 	proxier.serviceIPs.reset(tx)
@@ -747,13 +773,98 @@ func (proxier *Proxier) Sync() {
 	proxier.syncRunner.Run()
 }
 
+func (proxier *Proxier) syncNodeInterfaces() {
+	minInterval := 5 * time.Second
+	maxInterval := 1 * time.Minute
+	rateLimiter := rate.NewLimiter(rate.Every(minInterval), 1)
+	// Resources are published periodically or if there is a netlink notification
+	// indicating a new interfaces was added or changed
+	nlChannel := make(chan netlink.LinkUpdate)
+	doneCh := make(chan struct{})
+	defer close(doneCh)
+	if err := netlink.LinkSubscribe(nlChannel, doneCh); err != nil {
+		proxier.logger.Error(err, "error subscribing to netlink interfaces, only syncing periodically", "interval", maxInterval.String())
+	}
+
+	for {
+		err := rateLimiter.Wait(context.Background())
+		if err != nil {
+			proxier.logger.Error(err, "unexpected rate limited error trying to get system interfaces")
+		}
+		ifnames, err := proxier.getNodeInterfaces()
+		if err != nil {
+			proxier.logger.Error(err, "failed to list system network interfaces")
+		}
+		if len(ifnames) > 0 {
+			tx := proxier.nftables.NewTransaction()
+			tx.Add(&knftables.Flowtable{
+				Name:    serviceFlowTable,
+				Devices: ifnames,
+			})
+			err := proxier.nftables.Run(context.Background(), tx)
+			if err != nil {
+				proxier.logger.Error(err, "failed to add network interfaces to the flowtable")
+			}
+		}
+
+		select {
+		// trigger a reconcile
+		case <-nlChannel:
+			// drain the channel so we only sync once
+			for len(nlChannel) > 0 {
+				<-nlChannel
+			}
+		case <-time.After(maxInterval):
+		}
+	}
+
+}
+
+func (proxier *Proxier) getNodeInterfaces() ([]string, error) {
+	ifNames := []string{}
+
+	ifaces, err := net.Interfaces()
+	if err != nil {
+		return ifNames, err
+	}
+
+	for _, iface := range ifaces {
+		klog.V(7).InfoS("Checking network interface", "name", iface.Name)
+		// skip down interfaces
+		if iface.Flags&net.FlagUp == 0 {
+			continue
+		}
+		// skip loopback interfaces
+		if iface.Flags&net.FlagLoopback != 0 {
+			continue
+		}
+
+		var ifaceType string
+		link, err := netlink.LinkByName(iface.Name)
+		// allow to match only by name if it is not possible to get the type
+		if err != nil {
+			klog.ErrorS(err, "error getting link by name")
+		} else {
+			ifaceType = link.Type()
+		}
+
+		klog.V(7).InfoS("Checking network interface", "name", iface.Name, "type", ifaceType)
+	}
+
+	return ifNames, nil
+}
+
 // SyncLoop runs periodic work.  This is expected to run as a goroutine or as the main loop of the app.  It does not return.
 func (proxier *Proxier) SyncLoop() {
 	// Update healthz timestamp at beginning in case Sync() never succeeds.
 	if proxier.healthzServer != nil {
 		proxier.healthzServer.Updated(proxier.ipFamily)
 	}
 
+	if proxier.fastpathPacketThreshold > 0 {
+		go proxier.syncNodeInterfaces()
+	}
+
 	// synthesize "last change queued" time as the informers are syncing.
 	metrics.SyncProxyRulesLastQueuedTimestamp.SetToCurrentTime()
 	proxier.syncRunner.Loop(wait.NeverStop)

diff --git a/staging/src/k8s.io/kube-proxy/config/v1alpha1/types.go b/staging/src/k8s.io/kube-proxy/config/v1alpha1/types.go
@@ -94,6 +94,10 @@ type KubeProxyNFTablesConfiguration struct {
 	// '1m', '2h22m'). A value of 0 means every Service or EndpointSlice change will
 	// result in an immediate iptables resync.
 	MinSyncPeriod metav1.Duration `json:"minSyncPeriod"`
+	// FastpathPacketThreshold is the number of packets untile the proxy starts offloading
+	// the connection to the fast path and skipping the kernel stack.
+	// Set to 0 to disable it.
+	FastpathPacketThreshold *int32 `json:"fastpathPacketThreshold"`
 }
 
 // KubeProxyConntrackConfiguration contains conntrack settings for