使用 istio 创建外部服务的内部别名

Question

使用 istio 是否可以为使用定义的服务网格外部的服务创建内部别名ServieEntry并控制对外部服务的访问？

例如假设我有一个服务条目

apiVersion: networking.istio.io/v1beta1
kind: ServiceEntry
metadata:
  name: mypgsql
  namespace: externalapps
spec:
  hosts:
  - mypgsql.example.com
  location: MESH_EXTERNAL
  ports:
  - number: 5432
    protocol: TCP
  resolution: DNS
---
apiVersion: security.istio.io/v1beta1
kind: AuthorizationPolicy
metadata:
  name: default-deny
  namespace:  externalapps
spec:
  selector:
  ... How would I select the service entry ...

我可以在引用 mypsql 服务条目的应用程序命名空间中创建另一个服务条目或其他资源吗？

apiVersion: networking.istio.io/v1beta1
kind: ServiceEntry
metadata:
  name: dbsvc
  namespace: someapp
spec:
  hosts:
  - mypsql.externalapps
  location: MESH_EXTERNAL
  ports:
  - number: 5432
    protocol: TCP
  resolution: DNS
---
apiVersion: security.istio.io/v1beta1
kind: AuthorizationPolicy
metadata:
  name: default-deny-db
  namespace:  someapp
spec:
  selector:
  ... How would I select the dbsvc service entry ...
---
apiVersion: security.istio.io/v1beta1
kind: AuthorizationPolicy
metadata:
  name: allow-backend-to-db
  namespace:  someapp
spec:
  selector:
  ... How would I select the dbsvc service entry ...
  action: ALLOW
  rules:
  - from:
     - source:
         principals:
         - app_backend