bug: HTTPRoute ignores appProtocol setting for ExternalName types

[ronnybremer]

Current Behavior

A configured HTTPRoute pointing to an internal service can be configured with appProtocol: kubernetes.io/ws. However, if the service is of type ExternalName the same setting gets applied by Kubernetes but not read by the Apisix controller.
This seems to be due to this code:

apisix-ingress-controller/internal/adc/translator/httproute.go

Lines 420 to 446 in 11635a1

	if service.Spec.Type == corev1.ServiceTypeExternalName {
	port := 80
	if ref.Port != nil {
	port = int(*ref.Port)
	}
	return adctypes.UpstreamNodes{
	{
	Host: service.Spec.ExternalName,
	Port: port,
	Weight: weight,
	},
	}, protocol, nil
	}
	var portName *string
	if ref.Port != nil {
	for _, p := range service.Spec.Ports {
	if int(p.Port) == int(*ref.Port) {
	portName = ptr.To(p.Name)
	protocol = ptr.Deref(p.AppProtocol, "")
	break
	}
	}
	if portName == nil {
	return adctypes.UpstreamNodes{}, protocol, nil
	}
	}

Expected Behavior

I expect the appProtocol to be read from both internal end external services.

Error Logs

No response

Steps to Reproduce

1. Install Apisix with helm chart
2. configure an internal service
3. configure an external service
4. create a HTTPRoute config for the internal service
5. create a HTTPRoute config for the external service
6. specify "appProtocol: kubernetes.io/ws" in both services
7. kubectl apply both services and routes
8. observe the Kubernetes resources get created correctly
9. establish a web socket connection to the internal service and observe the connection gets established
10. establish a web socket connection to the external service and observe the connection receiving an error due to the filtering of "connection: upgrade" form the request to the backend

---
apiVersion: v1
kind: Service
metadata:
  name: test-portal
spec:
  selector:
    app: test-portal
  ports:
    - protocol: TCP
      port: 5000
      targetPort: 5000
      appProtocol: kubernetes.io/ws
---
apiVersion: v1
kind: Service
metadata:
  name: test-portal-ext
spec:
  ports:
    - protocol: TCP
      port: 8000
      appProtocol: kubernetes.io/ws
  type: ExternalName
  externalName: testportal.dev.local

Environment

• APISIX Ingress controller version: 2.1.0
• Kubernetes cluster version: 1.35.0