https://kubernetes.io/docs/api-reference/v1.5/#servicespec-v1
If specified and supported by the platform, this will restrict traffic through the cloud-provider load-balancer will be restricted to the specified client IPs. This field will be ignored if the cloud-provider does not support the feature.
http://kubernetes.io/docs/user-guide/services-firewalls
https://kubernetes.io/docs/api-reference/v1.5/#servicespec-v1
http://kubernetes.io/docs/user-guide/services-firewalls