fix: use targeted patch in calcSubnetStatusIP to prevent U2O status overwrite

calcSubnetStatusIP previously used subnet.Status.Bytes() which serialized
the entire SubnetStatus and patched all fields to etcd. This caused a race
condition where handleUpdateSubnetStatus could overwrite U2OInterconnectionVPC
with stale data from its informer cache, leading to flaky e2e test failures
in "should support underlay to overlay subnet interconnection".

The race condition occurs when:
1. handleAddOrUpdateSubnet sets U2OInterconnectionVPC and patches status
2. handleUpdateSubnetStatus retries (from IP inconsistency requeue), reads
   stale cache without U2OInterconnectionVPC, and calcSubnetStatusIP
   overwrites all status fields including U2OInterconnectionVPC=""

Fix by using a targeted JSON merge patch that only includes the 8 IP-related
fields, leaving non-IP fields like U2OInterconnectionVPC untouched.

Signed-off-by: Mengxin Liu <liumengxinfly@gmail.com>
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: oilbeater

pkg/controller/subnet_status.go

@@ -242,7 +242,30 @@ func (c *Controller) calcSubnetStatusIP(subnet *kubeovnv1.Subnet) (*kubeovnv1.Su
 	subnet.Status.V6UsingIPRange = v6UsingIPStr
 	subnet.Status.V4AvailableIPRange = v4AvailableIPStr
 	subnet.Status.V6AvailableIPRange = v6AvailableIPStr
-	bytes, err := subnet.Status.Bytes()
+
+	// Use a targeted patch with only IP-related fields to avoid overwriting
+	// non-IP status fields (e.g., U2OInterconnectionVPC) set by other handlers.
+	ipStatusPatch := struct {
+		Status struct {
+			V4AvailableIPs     float64 `json:"v4availableIPs"`
+			V4AvailableIPRange string  `json:"v4availableIPrange"`
+			V4UsingIPs         float64 `json:"v4usingIPs"`
+			V4UsingIPRange     string  `json:"v4usingIPrange"`
+			V6AvailableIPs     float64 `json:"v6availableIPs"`
+			V6AvailableIPRange string  `json:"v6availableIPrange"`
+			V6UsingIPs         float64 `json:"v6usingIPs"`
+			V6UsingIPRange     string  `json:"v6usingIPrange"`
+		} `json:"status"`
+	}{}
+	ipStatusPatch.Status.V4AvailableIPs = v4availableIPs
+	ipStatusPatch.Status.V4AvailableIPRange = v4AvailableIPStr
+	ipStatusPatch.Status.V4UsingIPs = v4UsingIPs
+	ipStatusPatch.Status.V4UsingIPRange = v4UsingIPStr
+	ipStatusPatch.Status.V6AvailableIPs = v6availableIPs
+	ipStatusPatch.Status.V6AvailableIPRange = v6AvailableIPStr
+	ipStatusPatch.Status.V6UsingIPs = v6UsingIPs
+	ipStatusPatch.Status.V6UsingIPRange = v6UsingIPStr
+	bytes, err := json.Marshal(ipStatusPatch)
 	if err != nil {
 		klog.Error(err)
 		return nil, err