Fix race in GN pod for out-of-order RemoteEndpoint events

When there is a gateway migration in a remote cluster or if there
is any stale endpoint on the Broker associated with the remoteCluster,
the events might come in out of order which can create issues for
datapath connectivity. This PR includes the necessary checks in
Globalnet pod to ignore any stale events.

Related to: submariner-io#2399
Signed-off-by: Sridhar Gaddam <sgaddam@redhat.com>

pkg/globalnet/controllers/gateway_monitor.go

@@ -37,6 +37,7 @@ import (
 	"github.com/submariner-io/submariner/pkg/netlink"
 	routeAgent "github.com/submariner-io/submariner/pkg/routeagent_driver/constants"
 	corev1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/util/sets"
 	"k8s.io/client-go/dynamic"
@@ -47,11 +48,12 @@ import (
 func NewGatewayMonitor(spec Specification, localCIDRs []string, config *watcher.Config) (Interface, error) {
 	// We'll panic if config is nil, this is intentional
 	gatewayMonitor := &gatewayMonitor{
-		baseController: newBaseController(),
-		spec:           spec,
-		isGatewayNode:  atomic.Bool{},
-		localSubnets:   sets.New(localCIDRs...).UnsortedList(),
-		remoteSubnets:  sets.New[string](),
+		baseController:          newBaseController(),
+		spec:                    spec,
+		isGatewayNode:           atomic.Bool{},
+		localSubnets:            sets.New(localCIDRs...).UnsortedList(),
+		remoteSubnets:           sets.New[string](),
+		remoteEndpointTimeStamp: map[string]metav1.Time{},
 	}
 
 	var err error
@@ -143,6 +145,14 @@ func (g *gatewayMonitor) handleCreatedOrUpdatedEndpoint(obj runtime.Object, _ in
 	logger.V(log.DEBUG).Infof("In processNextEndpoint, endpoint info: %+v", endpoint)
 
 	if endpoint.Spec.ClusterID != g.spec.ClusterID {
+		lastProcessedTime, ok := g.remoteEndpointTimeStamp[endpoint.Spec.ClusterID]
+
+		if ok && lastProcessedTime.After(endpoint.CreationTimestamp.Time) {
+			logger.Infof("Ignoring new remote %#v since a later endpoint was already"+
+				"processed", endpoint)
+			return false
+		}
+
 		logger.V(log.DEBUG).Infof("Endpoint %q, host: %q belongs to a remote cluster",
 			endpoint.Spec.ClusterID, endpoint.Spec.Hostname)
 
@@ -168,6 +178,8 @@ func (g *gatewayMonitor) handleCreatedOrUpdatedEndpoint(obj runtime.Object, _ in
 			}
 		}
 
+		g.remoteEndpointTimeStamp[endpoint.Spec.ClusterID] = endpoint.CreationTimestamp
+
 		return false
 	}
 
@@ -206,6 +218,16 @@ func (g *gatewayMonitor) handleCreatedOrUpdatedEndpoint(obj runtime.Object, _ in
 func (g *gatewayMonitor) handleRemovedEndpoint(obj runtime.Object, _ int) bool {
 	endpoint := obj.(*v1.Endpoint)
 
+	lastProcessedTime, ok := g.remoteEndpointTimeStamp[endpoint.Spec.ClusterID]
+
+	if ok && lastProcessedTime.After(endpoint.CreationTimestamp.Time) {
+		logger.Infof("Ignoring deleted remote %#v since a later endpoint was already"+
+			"processed", endpoint)
+		return false
+	}
+
+	delete(g.remoteEndpointTimeStamp, endpoint.Spec.ClusterID)
+
 	logger.V(log.DEBUG).Infof("Informed of removed endpoint for gateway monitor: %v", endpoint)
 
 	hostname, err := os.Hostname()

pkg/globalnet/controllers/types.go

@@ -91,16 +91,17 @@ type baseController struct {
 
 type gatewayMonitor struct {
 	*baseController
-	syncerConfig     *syncer.ResourceSyncerConfig
-	endpointWatcher  watcher.Interface
-	spec             Specification
-	ipt              iptables.Interface
-	isGatewayNode    atomic.Bool
-	nodeName         string
-	localSubnets     []string
-	remoteSubnets    sets.Set[string]
-	controllersMutex sync.Mutex // Protects controllers
-	controllers      []Interface
+	syncerConfig            *syncer.ResourceSyncerConfig
+	endpointWatcher         watcher.Interface
+	remoteEndpointTimeStamp map[string]metav1.Time
+	spec                    Specification
+	ipt                     iptables.Interface
+	isGatewayNode           atomic.Bool
+	nodeName                string
+	localSubnets            []string
+	remoteSubnets           sets.Set[string]
+	controllersMutex        sync.Mutex // Protects controllers
+	controllers             []Interface
 }
 
 type baseSyncerController struct {