From 12d34624ba44d23db28e33ff24020151c83d9cec Mon Sep 17 00:00:00 2001
From: Natasha Sarkar <natashasarkar@google.com>
Date: Thu, 6 Mar 2025 20:14:32 +0000
Subject: [PATCH] add observedGeneration to pod's dropDisabledStatusFields

---
 pkg/api/pod/util.go      |  29 ++++++++---
 pkg/api/pod/util_test.go | 101 ++++++++++++++++++++++++++++++++++++++-
 2 files changed, 123 insertions(+), 7 deletions(-)

diff --git a/pkg/api/pod/util.go b/pkg/api/pod/util.go
index 06a2573fcd2..aff5745c966 100644
--- a/pkg/api/pod/util.go
+++ b/pkg/api/pod/util.go
@@ -854,6 +854,13 @@ func dropDisabledPodStatusFields(podStatus, oldPodStatus *api.PodStatus, podSpec
 		dropUserField(podStatus.ContainerStatuses)
 		dropUserField(podStatus.EphemeralContainerStatuses)
 	}
+
+	if !utilfeature.DefaultFeatureGate.Enabled(features.PodObservedGenerationTracking) && !podObservedGenerationTrackingInUse(oldPodStatus) {
+		podStatus.ObservedGeneration = 0
+		for i := range podStatus.Conditions {
+			podStatus.Conditions[i].ObservedGeneration = 0
+		}
+	}
 }
 
 // dropDisabledDynamicResourceAllocationFields removes pod claim references from
@@ -1050,18 +1057,28 @@ func nodeTaintsPolicyInUse(podSpec *api.PodSpec) bool {
 
 // hostUsersInUse returns true if the pod spec has spec.hostUsers field set.
 func hostUsersInUse(podSpec *api.PodSpec) bool {
-	if podSpec != nil && podSpec.SecurityContext != nil && podSpec.SecurityContext.HostUsers != nil {
-		return true
-	}
-
-	return false
+	return podSpec != nil && podSpec.SecurityContext != nil && podSpec.SecurityContext.HostUsers != nil
 }
 
 func supplementalGroupsPolicyInUse(podSpec *api.PodSpec) bool {
-	if podSpec != nil && podSpec.SecurityContext != nil && podSpec.SecurityContext.SupplementalGroupsPolicy != nil {
+	return podSpec != nil && podSpec.SecurityContext != nil && podSpec.SecurityContext.SupplementalGroupsPolicy != nil
+}
+
+func podObservedGenerationTrackingInUse(podStatus *api.PodStatus) bool {
+	if podStatus == nil {
+		return false
+	}
+
+	if podStatus.ObservedGeneration != 0 {
 		return true
 	}
 
+	for _, condition := range podStatus.Conditions {
+		if condition.ObservedGeneration != 0 {
+			return true
+		}
+	}
+
 	return false
 }
 
diff --git a/pkg/api/pod/util_test.go b/pkg/api/pod/util_test.go
index 42678e29b8b..bd52ff183eb 100644
--- a/pkg/api/pod/util_test.go
+++ b/pkg/api/pod/util_test.go
@@ -21,6 +21,7 @@ import (
 	"reflect"
 	"strings"
 	"testing"
+	"time"
 
 	"github.com/google/go-cmp/cmp"
 	"github.com/stretchr/testify/assert"
@@ -1016,7 +1017,7 @@ func TestValidatePodDeletionCostOption(t *testing.T) {
 	}
 }
 
-func TestDropDisabledPodStatusFields(t *testing.T) {
+func TestDropDisabledPodStatusFields_HostIPs(t *testing.T) {
 	podWithHostIPs := func() *api.PodStatus {
 		return &api.PodStatus{
 			HostIPs: makeHostIPs("10.0.0.1", "fd00:10::1"),
@@ -1083,6 +1084,104 @@ func makeHostIPs(ips ...string) []api.HostIP {
 	return ret
 }
 
+func TestDropDisabledPodStatusFields_ObservedGeneration(t *testing.T) {
+	now := metav1.NewTime(time.Now())
+
+	podWithObservedGen := func() *api.PodStatus {
+		return &api.PodStatus{
+			ObservedGeneration: 1,
+			Conditions: []api.PodCondition{{
+				LastProbeTime:      now,
+				LastTransitionTime: now,
+			}},
+		}
+	}
+	podWithObservedGenInConditions := func() *api.PodStatus {
+		return &api.PodStatus{
+			Conditions: []api.PodCondition{{
+				LastProbeTime:      now,
+				LastTransitionTime: now,
+				ObservedGeneration: 1,
+			}},
+		}
+	}
+
+	podWithoutObservedGen := func() *api.PodStatus {
+		return &api.PodStatus{
+			Conditions: []api.PodCondition{{
+				LastProbeTime:      now,
+				LastTransitionTime: now,
+			}},
+		}
+	}
+
+	tests := []struct {
+		name          string
+		podStatus     *api.PodStatus
+		oldPodStatus  *api.PodStatus
+		wantPodStatus *api.PodStatus
+	}{
+		{
+			name:         "old=without, new=without",
+			oldPodStatus: podWithoutObservedGen(),
+			podStatus:    podWithoutObservedGen(),
+
+			wantPodStatus: podWithoutObservedGen(),
+		},
+		{
+			name:         "old=without, new=with",
+			oldPodStatus: podWithoutObservedGen(),
+			podStatus:    podWithObservedGen(),
+
+			wantPodStatus: podWithoutObservedGen(),
+		},
+		{
+			name:         "old=with, new=without",
+			oldPodStatus: podWithObservedGen(),
+			podStatus:    podWithoutObservedGen(),
+
+			wantPodStatus: podWithoutObservedGen(),
+		},
+		{
+			name:         "old=with, new=with",
+			oldPodStatus: podWithObservedGen(),
+			podStatus:    podWithObservedGen(),
+
+			wantPodStatus: podWithObservedGen(),
+		},
+		{
+			name:         "old=without, new=withInConditions",
+			oldPodStatus: podWithoutObservedGen(),
+			podStatus:    podWithObservedGenInConditions(),
+
+			wantPodStatus: podWithoutObservedGen(),
+		},
+		{
+			name:         "old=withInConditions, new=without",
+			oldPodStatus: podWithObservedGenInConditions(),
+			podStatus:    podWithoutObservedGen(),
+
+			wantPodStatus: podWithoutObservedGen(),
+		},
+		{
+			name:         "old=withInConditions, new=withInCondtions",
+			oldPodStatus: podWithObservedGenInConditions(),
+			podStatus:    podWithObservedGenInConditions(),
+
+			wantPodStatus: podWithObservedGenInConditions(),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			dropDisabledPodStatusFields(tt.podStatus, tt.oldPodStatus, &api.PodSpec{}, &api.PodSpec{})
+
+			if !reflect.DeepEqual(tt.podStatus, tt.wantPodStatus) {
+				t.Errorf("dropDisabledStatusFields() = %v, want %v", tt.podStatus, tt.wantPodStatus)
+			}
+		})
+	}
+}
+
 func TestDropNodeInclusionPolicyFields(t *testing.T) {
 	ignore := api.NodeInclusionPolicyIgnore
 	honor := api.NodeInclusionPolicyHonor