I have deployed two services to a Kubernetes Cluster on GCP:

One is a Spring Cloud Api Gateway implementation:

apiVersion: v1
kind: Service
metadata:
  name: api-gateway
spec:
  ports:
  - name: main
    port: 80
    targetPort: 8080
    protocol: TCP
  selector:
    app: api-gateway
    tier: web
  type: NodePort

The other one is a backend chat service implementation which exposes a WebSocket at /ws/ path.

apiVersion: v1
kind: Service
metadata:
 name: chat-api
spec:
  ports:
  - name: main
    port: 80
    targetPort: 8080
    protocol: TCP
  selector:
    app: chat
    tier: web
  type: NodePort

The API Gateway is exposed to internet through a Contour Ingress Controller:

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: api-gateway-ingress
  annotations:
    kubernetes.io/tls-acme: "true"
    certmanager.k8s.io/cluster-issuer: "letsencrypt-prod"
    ingress.kubernetes.io/force-ssl-redirect: "true"
spec:
  tls:
  - secretName: api-gateway-tls
    hosts:
    - api.mydomain.com.br
  rules:
  - host: api.mydomain.com.br
    http:
      paths:
      - backend:
          serviceName: api-gateway
          servicePort: 80

The gateway routes incoming calls to /chat/ path to the chat service on /ws/:

@Bean
public RouteLocator routes(RouteLocatorBuilder builder) {
    return builder.routes()
            .route(r -> r.path("/chat/**")
                    .filters(f -> f.rewritePath("/chat/(?<segment>.*)", "/ws/(?<segment>.*)"))
                    .uri("ws://chat-api"))
            .build();
}

When I try to connect to the WebSocket through the gateway I get a 403 error:

error: Unexpected server response: 403

I even tried to connect using http, https, ws and wss but the error remains.

Anyone has a clue?