silverstripe-framework/_config/requestprocessors.yml

---
Name: requestprocessors
---
SilverStripe\Core\Injector\Injector:
  SilverStripe\Control\Director:
    # Note: Don't add 'class' config here, as it will affect ErrorDirector as well
    properties:
      Middlewares:
        TrustedProxyMiddleware: '%$SilverStripe\Control\Middleware\TrustedProxyMiddleware'
        AllowedHostsMiddleware: '%$SilverStripe\Control\Middleware\AllowedHostsMiddleware'
        SessionMiddleware: '%$SilverStripe\Control\Middleware\SessionMiddleware'
        RequestProcessorMiddleware: '%$SilverStripe\Control\RequestProcessor'
        FlushMiddleware: '%$SilverStripe\Control\Middleware\FlushMiddleware'
  SilverStripe\Control\AllowedHostsMiddleware:
    properties:
      AllowedHosts: "`SS_ALLOWED_HOSTS`"
  SilverStripe\Control\TrustedProxyMiddleware:
    properties:
      TrustedProxyIPs: "`SS_TRUSTED_PROXY_IPS`"
---
Name: errorrequestprocessors
After:
  - requestprocessors
---
SilverStripe\Core\Injector\Injector:
  # Note: If Director config changes, take note it will affect this config too
  SilverStripe\Core\Startup\ErrorDirector: '%$SilverStripe\Control\Director'