From 62889f416cb60f66b3f04810ef2475c425b8394a Mon Sep 17 00:00:00 2001
From: Aldo Culquicondor <acondor@google.com>
Date: Thu, 16 Mar 2023 16:35:39 -0400
Subject: [PATCH] Preserve UID/ResourceVersion in the BindingREST endpoint

Change-Id: If4023da10c455963a320fdb9fc2a73c099bea3db
---
 pkg/registry/core/pod/storage/storage.go                 | 8 ++++++++
 .../k8s.io/apiserver/pkg/endpoints/handlers/create.go    | 9 +++++++--
 staging/src/k8s.io/apiserver/pkg/registry/rest/rest.go   | 7 +++++++
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/pkg/registry/core/pod/storage/storage.go b/pkg/registry/core/pod/storage/storage.go
index ddc089ab153..5bdf342d068 100644
--- a/pkg/registry/core/pod/storage/storage.go
+++ b/pkg/registry/core/pod/storage/storage.go
@@ -163,6 +163,7 @@ func (r *BindingREST) Destroy() {
 }
 
 var _ = rest.NamedCreater(&BindingREST{})
+var _ = rest.SubresourceObjectMetaPreserver(&BindingREST{})
 
 // Create ensures a pod is bound to a specific host.
 func (r *BindingREST) Create(ctx context.Context, name string, obj runtime.Object, createValidation rest.ValidateObjectFunc, options *metav1.CreateOptions) (out runtime.Object, err error) {
@@ -191,6 +192,13 @@ func (r *BindingREST) Create(ctx context.Context, name string, obj runtime.Objec
 	return
 }
 
+// PreserveRequestObjectMetaSystemFieldsOnSubresourceCreate indicates to a
+// handler that this endpoint requires the UID and ResourceVersion to use as
+// preconditions. Other fields, such as timestamp, are ignored.
+func (r *BindingREST) PreserveRequestObjectMetaSystemFieldsOnSubresourceCreate() bool {
+	return true
+}
+
 // setPodHostAndAnnotations sets the given pod's host to 'machine' if and only if
 // the pod is unassigned and merges the provided annotations with those of the pod.
 // Returns the current state of the pod, or an error.
diff --git a/staging/src/k8s.io/apiserver/pkg/endpoints/handlers/create.go b/staging/src/k8s.io/apiserver/pkg/endpoints/handlers/create.go
index 71f4990a026..78c1d2f52a7 100644
--- a/staging/src/k8s.io/apiserver/pkg/endpoints/handlers/create.go
+++ b/staging/src/k8s.io/apiserver/pkg/endpoints/handlers/create.go
@@ -162,8 +162,13 @@ func createHandler(r rest.NamedCreater, scope *RequestScope, admit admission.Int
 		userInfo, _ := request.UserFrom(ctx)
 
 		if objectMeta, err := meta.Accessor(obj); err == nil {
-			// Wipe fields which cannot take user-provided values
-			rest.WipeObjectMetaSystemFields(objectMeta)
+			preserveObjectMetaSystemFields := false
+			if c, ok := r.(rest.SubresourceObjectMetaPreserver); ok && len(scope.Subresource) > 0 {
+				preserveObjectMetaSystemFields = c.PreserveRequestObjectMetaSystemFieldsOnSubresourceCreate()
+			}
+			if !preserveObjectMetaSystemFields {
+				rest.WipeObjectMetaSystemFields(objectMeta)
+			}
 
 			// ensure namespace on the object is correct, or error if a conflicting namespace was set in the object
 			if err := rest.EnsureObjectNamespaceMatchesRequestNamespace(rest.ExpectedNamespaceForResource(namespace, scope.Resource), objectMeta); err != nil {
diff --git a/staging/src/k8s.io/apiserver/pkg/registry/rest/rest.go b/staging/src/k8s.io/apiserver/pkg/registry/rest/rest.go
index b8d47ff4fe3..78b6ea8b0ef 100644
--- a/staging/src/k8s.io/apiserver/pkg/registry/rest/rest.go
+++ b/staging/src/k8s.io/apiserver/pkg/registry/rest/rest.go
@@ -209,6 +209,13 @@ type NamedCreater interface {
 	Create(ctx context.Context, name string, obj runtime.Object, createValidation ValidateObjectFunc, options *metav1.CreateOptions) (runtime.Object, error)
 }
 
+// SubresourceObjectMetaPreserver adds configuration options to a Creater for subresources.
+type SubresourceObjectMetaPreserver interface {
+	// PreserveRequestObjectMetaSystemFieldsOnSubresourceCreate indicates that a
+	// handler should preserve fields of ObjectMeta that are managed by the system.
+	PreserveRequestObjectMetaSystemFieldsOnSubresourceCreate() bool
+}
+
 // UpdatedObjectInfo provides information about an updated object to an Updater.
 // It requires access to the old object in order to return the newly updated object.
 type UpdatedObjectInfo interface {