add headers via EnvoyFilter to all hosts and routes

add-x-cluster-client-ip-header.yaml

apiVersion: networking.istio.io/v1alpha3
kind: EnvoyFilter
metadata:
  name: add-x-cluster-client-ip-header
  namespace: istio-system
spec:
  configPatches:
  - applyTo: ROUTE_CONFIGURATION
    match:
      context: SIDECAR_INBOUND
    patch:
      operation: MERGE
      value:
        request_headers_to_add:
          - header:
              key: 'x-cluster-client-ip'
              value: '%DOWNSTREAM_REMOTE_ADDRESS_WITHOUT_PORT%'
            append: false
        # the following is used to debug
        response_headers_to_add:
          - header:
              key: 'x-cluster-client-ip'
              value: '%DOWNSTREAM_REMOTE_ADDRESS_WITHOUT_PORT%'
            append: false