[sample #12960] [v2] felix: periodically re-announce proxy-neighbor IPs

api/pkg/apis/projectcalico/v3/felixconfig.go

@@ -1124,6 +1124,15 @@ type FelixConfigurationSpec struct {
 	// +optional
 	LocalSubnetL2Reachability *LocalSubnetL2ReachabilityMode `json:"localSubnetL2Reachability,omitempty" validate:"omitempty,oneof=Disabled PodsAndLoadBalancers"`
 
+	// LocalSubnetL2ReachabilityRefreshInterval controls how often Felix re-announces
+	// (gratuitous ARP / unsolicited NA) every IP it proxies ARP/NDP for when
+	// LocalSubnetL2Reachability is enabled, keeping neighbor caches and switch
+	// forwarding tables warm even when the set of proxied IPs is unchanged. Set to 0
+	// to disable periodic re-announcement, leaving only the one-shot announce when an
+	// IP is added. [Default: 120s]
+	// +optional
+	LocalSubnetL2ReachabilityRefreshInterval *metav1.Duration `json:"localSubnetL2ReachabilityRefreshInterval,omitempty" configv1timescale:"seconds"`
+
 	// WindowsManageFirewallRules configures whether or not Felix will program Windows Firewall rules (to allow inbound access to its own metrics ports). [Default: Disabled]
 	// +optional
 	WindowsManageFirewallRules *WindowsManageFirewallRulesMode `json:"windowsManageFirewallRules,omitempty" validate:"omitempty,oneof=Enabled Disabled"`

felix/config/config_params.go

@@ -380,6 +380,13 @@ type Config struct {
 	// selected LoadBalancer VIPs that overlap the host subnet. [Default: Disabled]
 	LocalSubnetL2Reachability string `config:"oneof(Disabled,PodsAndLoadBalancers);Disabled"`
 
+	// LocalSubnetL2ReachabilityRefreshInterval controls how often Felix re-announces
+	// (gratuitous ARP / unsolicited NA) every IP it proxies ARP/NDP for, keeping
+	// neighbor caches and switch forwarding tables warm even when the set of
+	// proxied IPs is unchanged. Set to 0 to disable periodic re-announcement,
+	// leaving only the one-shot announce when an IP is added. [Default: 120s]
+	LocalSubnetL2ReachabilityRefreshInterval time.Duration `config:"seconds;120"`
+
 	// WindowsManageFirewallRules configures whether or not Felix will program Windows Firewall rules. [Default: Disabled]
 	WindowsManageFirewallRules string `config:"oneof(Enabled,Disabled);Disabled"`
 

felix/dataplane/driver.go

@@ -217,10 +217,11 @@ func StartDataplaneDriver(
 		}
 
 		dpConfig := intdataplane.Config{
-			Hostname:                  felixHostname,
-			NodeZone:                  felixNodeZone,
-			FloatingIPsEnabled:        strings.EqualFold(configParams.FloatingIPs, string(apiv3.FloatingIPsEnabled)),
-			LocalSubnetL2Reachability: configParams.LocalSubnetL2Reachability,
+			Hostname:                                 felixHostname,
+			NodeZone:                                 felixNodeZone,
+			FloatingIPsEnabled:                       strings.EqualFold(configParams.FloatingIPs, string(apiv3.FloatingIPsEnabled)),
+			LocalSubnetL2Reachability:                configParams.LocalSubnetL2Reachability,
+			LocalSubnetL2ReachabilityRefreshInterval: configParams.LocalSubnetL2ReachabilityRefreshInterval,
 			IfaceMonitorConfig: ifacemonitor.Config{
 				InterfaceExcludes: configParams.InterfaceExclude,
 				ResyncInterval:    configParams.InterfaceRefreshInterval,

felix/dataplane/linux/int_dataplane.go

@@ -188,7 +188,8 @@ type Config struct {
 
 	FloatingIPsEnabled bool
 
-	LocalSubnetL2Reachability string
+	LocalSubnetL2Reachability                string
+	LocalSubnetL2ReachabilityRefreshInterval time.Duration
 
 	Wireguard wireguard.Config
 

felix/dataplane/linux/proxy_neigh_mgr.go

@@ -43,13 +43,15 @@ import (
 	"github.com/projectcalico/calico/libcalico-go/lib/set"
 )
 
-// readDeadlineInterval bounds how long an ARP/NDP listener blocks in a
-// single socket read before waking to re-check for context cancellation.
-// A read that hits the deadline simply loops
-const readDeadlineInterval = 1 * time.Second
-
-// ipv6AllNodesMulticast is the IPv6 all-nodes link-local multicast address
-const ipv6AllNodesMulticast = "ff02::1"
+const (
+	// readDeadlineInterval bounds how long an ARP/NDP listener blocks in a
+	// single socket read before waking to re-check for context cancellation.
+	// A read that hits the deadline simply loops
+	readDeadlineInterval = 1 * time.Second
+
+	// ipv6AllNodesMulticast is the IPv6 all-nodes link-local multicast address
+	ipv6AllNodesMulticast = "ff02::1"
+)
 
 // serviceID identifies a Kubernetes Service by namespace and name. Used as a
 // map key for tracking LoadBalancer service IPs.
@@ -94,6 +96,10 @@ type proxyNeighManager struct {
 	// before looping to re-check for cancellation.
 	readTimeout time.Duration
 
+	// announceInterval is how often each listener re-announces every IP it owns.
+	// Zero or negative disables periodic re-announcement.
+	announceInterval time.Duration
+
 	// hostIfaceToCIDRs maps host interface name to the parsed CIDRs on that interface.
 	hostIfaceToCIDRs map[string][]net.IPNet
 
@@ -178,7 +184,7 @@ func newProxyNeighManager(dpConfig Config, ipVersion uint8) *proxyNeighManager {
 			return conn, ifi.HardwareAddr, nil
 		}
 	}
-	return newProxyNeighManagerWithShims(dpConfig, ipVersion, nl, af, nf, readDeadlineInterval)
+	return newProxyNeighManagerWithShims(dpConfig, ipVersion, nl, af, nf, readDeadlineInterval, dpConfig.LocalSubnetL2ReachabilityRefreshInterval)
 }
 
 // setIgnoreOutgoing sets PACKET_IGNORE_OUTGOING on the raw socket so the kernel
@@ -207,6 +213,7 @@ func newProxyNeighManagerWithShims(
 	af arpClientFactory,
 	nf ndpConnFactory,
 	readTimeout time.Duration,
+	announceInterval time.Duration,
 ) *proxyNeighManager {
 	wlIfacesPattern := "^(" + strings.Join(dpConfig.RulesConfig.WorkloadIfacePrefixes, "|") + ").*"
 	wlIfacesRegexp := regexp.MustCompile(wlIfacesPattern)
@@ -217,6 +224,7 @@ func newProxyNeighManagerWithShims(
 		hostname:         dpConfig.Hostname,
 		wlIfacesRegexp:   wlIfacesRegexp,
 		readTimeout:      readTimeout,
+		announceInterval: announceInterval,
 		hostIfaceToCIDRs: make(map[string][]net.IPNet),
 		localWorkloadIPs: make(map[types.WorkloadEndpointID][]string),
 		lbServiceIPs:     make(map[serviceID][]string),
@@ -522,11 +530,12 @@ func (m *proxyNeighManager) publishDesiredIPs(desiredByIface map[string]set.Set[
 // listener goroutine.
 func (m *proxyNeighManager) startListener(ifaceName string) error {
 	l := &ifaceListener{
-		ifaceName:   ifaceName,
-		readTimeout: m.readTimeout,
-		reconcile:   make(chan struct{}, 1),
-		announced:   set.New[string](),
-		done:        make(chan struct{}),
+		ifaceName:        ifaceName,
+		readTimeout:      m.readTimeout,
+		announceInterval: m.announceInterval,
+		reconcile:        make(chan struct{}, 1),
+		announced:        set.New[string](),
+		done:             make(chan struct{}),
 	}
 
 	l.ctx, l.cancel = context.WithCancel(m.ctx)
@@ -578,18 +587,27 @@ type ifaceListener struct {
 
 	// announced tracks the IPs the goroutine has already announced/joined for,
 	// so it can compute the delta against a new desired set. Goroutine-local:
-	// only ever touched by the listener goroutine, so it needs no
-	// synchronization.
+	// only ever touched by the listener goroutine, so it needs no synchronization.
 	announced set.Set[string]
 
 	arpCli      arpClient // IPv4 only
 	ndpCli      ndpConn   // IPv6 only
 	hwAddr      net.HardwareAddr
 	readTimeout time.Duration
-	ctx         context.Context
-	cancel      context.CancelFunc
-	done        chan struct{}
-	failed      atomic.Bool
+
+	// announceInterval is how often the goroutine re-announces every owned IP.
+	// Zero or negative disables periodic re-announcement (only the initial
+	// announce on add fires).
+	announceInterval time.Duration
+
+	// lastAnnounce is when the goroutine last re-announced its full owned set.
+	// Goroutine-local: compared against announceInterval each loop iteration.
+	lastAnnounce time.Time
+
+	ctx    context.Context
+	cancel context.CancelFunc
+	done   chan struct{}
+	failed atomic.Bool
 }
 
 // stop cancels the listener goroutine and waits for it to exit. The goroutine
@@ -663,10 +681,8 @@ func (l *ifaceListener) applyDesiredState() {
 		}
 		if l.ndpCli != nil {
 			l.joinNDPGroup(ip)
-			l.sendUNA(addr)
-		} else {
-			l.sendGARP(addr)
 		}
+		l.announce(addr)
 	}
 
 	// Release the multicast subscription for IPs that dropped out of the desired set.
@@ -682,6 +698,32 @@ func (l *ifaceListener) applyDesiredState() {
 	l.announced = desired
 }
 
+// announce sends a single gratuitous ARP (IPv4) or unsolicited NA (IPv6) for
+// addr. It does not touch multicast group membership, so it is safe to call
+// both for a newly desired IP (after joinNDPGroup) and for periodic refresh of
+// an already-joined IP.
+func (l *ifaceListener) announce(addr netip.Addr) {
+	if l.ndpCli != nil {
+		l.sendUNA(addr)
+	} else {
+		l.sendGARP(addr)
+	}
+}
+
+// reannounceAll re-sends a gratuitous ARP / unsolicited NA for every IP this
+// listener currently owns, refreshing neighbor caches and switch tables without
+// changing group membership. Driven by announceInterval from the listener loop.
+func (l *ifaceListener) reannounceAll() {
+	for ip := range l.announced.All() {
+		addr, err := netip.ParseAddr(ip)
+		if err != nil {
+			logrus.WithError(err).WithField("ip", ip).Debug("Failed to parse IP for re-announce")
+			continue
+		}
+		l.announce(addr)
+	}
+}
+
 // closeSocket leaves any joined NDP multicast groups and closes the raw socket.
 // It runs on the listener goroutine (deferred from runListener) so the socket
 // stays single-owner; stop() only cancels the context and waits.
@@ -795,6 +837,11 @@ func (l *ifaceListener) runListener(proto string, setDeadline func(time.Time) er
 	defer close(l.done)
 	defer l.closeSocket()
 
+	// Anchor the periodic re-announce clock to listener start so the first
+	// refresh fires announceInterval from now, not immediately after the
+	// initial announce that applyDesiredState performs below.
+	l.lastAnnounce = time.Now()
+
 	logCtx := logrus.WithFields(logrus.Fields{"iface": l.ifaceName, "proto": proto})
 	for {
 		if l.ctx.Err() != nil {
@@ -811,6 +858,15 @@ func (l *ifaceListener) runListener(proto string, setDeadline func(time.Time) er
 		default:
 		}
 
+		// Periodically re-announce every owned IP so neighbor caches and switch
+		// forwarding tables stay warm even when the desired set is unchanged.
+		// The loop wakes at least every readTimeout, so this fires within one
+		// readTimeout of the interval elapsing.
+		if l.announceInterval > 0 && time.Since(l.lastAnnounce) >= l.announceInterval {
+			l.reannounceAll()
+			l.lastAnnounce = time.Now()
+		}
+
 		if err := setDeadline(time.Now().Add(l.readTimeout)); err != nil {
 			logCtx.WithError(err).Warn("Failed to set read deadline")
 		}