feat: support backup hooks on native sidecars

changelogs/unreleased/9403-GabriFedi97

@@ -0,0 +1 @@
+Include InitContainer configured as Sidecars when validating the existence of the target containers configured for the Backup Hooks

pkg/podexec/pod_command_executor.go

@@ -20,6 +20,7 @@ import (
 	"bytes"
 	"context"
 	"net/url"
+	"slices"
 	"time"
 
 	"github.com/pkg/errors"
@@ -184,10 +185,22 @@ func (e *defaultPodCommandExecutor) ExecutePodCommand(log logrus.FieldLogger, it
 }
 
 func ensureContainerExists(pod *corev1api.Pod, container string) error {
-	for _, c := range pod.Spec.Containers {
-		if c.Name == container {
-			return nil
-		}
+	existsAsMainContainer := slices.ContainsFunc(pod.Spec.Containers, func(c corev1api.Container) bool {
+		return c.Name == container
+	})
+
+	if existsAsMainContainer {
+		return nil
+	}
+
+	existsAsSidecar := slices.ContainsFunc(pod.Spec.InitContainers, func(c corev1api.Container) bool {
+		return c.RestartPolicy != nil &&
+			*c.RestartPolicy == corev1api.ContainerRestartPolicyAlways &&
+			c.Name == container
+	})
+
+	if existsAsSidecar {
+		return nil
 	}
 
 	return errors.Errorf("no such container: %q", container)

pkg/podexec/pod_command_executor_test.go

@@ -35,6 +35,7 @@ import (
 	"k8s.io/apimachinery/pkg/runtime/schema"
 	"k8s.io/client-go/rest"
 	"k8s.io/client-go/tools/remotecommand"
+	"k8s.io/utils/ptr"
 
 	v1 "github.com/vmware-tanzu/velero/pkg/apis/velero/v1"
 	velerotest "github.com/vmware-tanzu/velero/pkg/test"
@@ -253,14 +254,29 @@ func TestEnsureContainerExists(t *testing.T) {
 					Name: "foo",
 				},
 			},
+			InitContainers: []corev1api.Container{
+				{
+					Name: "baz",
+				},
+				{
+					Name:          "qux",
+					RestartPolicy: ptr.To(corev1api.ContainerRestartPolicyAlways),
+				},
+			},
 		},
 	}
 
 	err := ensureContainerExists(pod, "bar")
 	require.EqualError(t, err, `no such container: "bar"`)
 
 	err = ensureContainerExists(pod, "foo")
-	assert.NoError(t, err)
+	require.NoError(t, err)
+
+	err = ensureContainerExists(pod, "baz")
+	require.EqualError(t, err, `no such container: "baz"`)
+
+	err = ensureContainerExists(pod, "qux")
+	require.NoError(t, err)
 }
 
 func TestPodCompeted(t *testing.T) {