tests/testdata/config/rule-default-route-append-headers.yaml

apiVersion: networking.istio.io/v1alpha3
kind: ServiceEntry
metadata:
  name: appendh
  namespace: testns
spec:
   hosts:
   - appendh.test.istio.io
   ports:
   - number: 80
     name: http
     protocol: HTTP
   resolution: STATIC
   endpoints:
    - address: 127.0.0.2
      ports:
        http: 7072
---
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: appendh-route
  namespace: testns
spec:
  hosts:
    - appendh.test.istio.io
  http:
    - route:
      - destination:
          host: appendh.test.istio.io
      headers:
        request:
          add:
            istio-custom-header: user-defined-value