# EnvoyFilter for adding the X-Forwarded-Host header.
# Needed for the Rok GW to work correctly.
# Older manifests used an Istio rule, but that relies on Mixer which
# is deprecated. This way is more performant and up-to-date.
#
# TODO: X-Forwarded-Host needs to be applied in two steps:
# 1. Put old host in `X-Forwarded-Host`
# 2. Update Host in request
#
# This filter only does (1). It can't do (2) because it doesn't know the new
# host yet. See if we can add an EnvoyFilter for (2). We currently have to do
# this per VirtualService, in each app that needs it.
apiVersion: networking.istio.io/v1alpha3
kind: EnvoyFilter
metadata:
  name: x-forwarded-host
spec:
  workloadSelector:
    labels:
      istio: ingressgateway
  configPatches:
    # The first patch adds the lua filter to the listener/http connection manager
  - applyTo: HTTP_FILTER
    match:
      context: GATEWAY
      listener:
        filterChain:
          filter:
            name: "envoy.http_connection_manager"
            subFilter:
              name: "envoy.router"
    patch:
      operation: INSERT_BEFORE
      value:
       name: envoy.filters.http.lua
       typed_config:
          "@type": "type.googleapis.com/envoy.extensions.filters.http.lua.v3.Lua"
          inlineCode: |
            function envoy_on_request(request_handle)
              local host = request_handle:headers():get(":authority")
              request_handle:headers():add("x-forwarded-host", host)
            end