TCP CRD: Enable multiple backends on the same frontend port by allowing backend-only TCP objects

[cfabriziohivemq]

This is more of a feature request than an issue. I would like the ability to create a backend using the TCP CRD without requiring a frontend. This would allow a scenario where one listener on a specific port can serve multiple backends.

Example
Consider a broker traffic serving the MQTTS port 8883

apiVersion: ingress.v1.haproxy.org/v1
kind: TCP
metadata:
  name: broker01-service-tcp
  annotations:
    ingress.class: haproxy
spec:
  - name: broker01-tcp
    frontend:
      name: broker01-frontend
      tcplog: true
      clitcpka: enabled
      tcp_request_rule_list:
        - type: inspect-delay
          timeout: 5000
          index: 0
        - cond: if
          cond_test: "{ req_ssl_hello_type 1 }"
          action: accept
          type: content
          index: 1
      backend_switching_rule_list:
        - cond: if
          cond_test: "{ req_ssl_sni -i broker01.example.com }"
          index: 0
          name: default_broker-mqtt_broker-mqtts-0
      binds:
        - name: mqtts
          port: 8883
          accept_proxy: true
    service:
      name: nginx-reject-all-service
      port: 30000
    services:
      - name: broker-mqtt
        port: 8883

This configuration generates the following HAProxy configuration:

frontend tcpcr_default_broker01-frontend
  mode tcp
  bind :8883 name mqtts accept-proxy
  option tcplog
  option clitcpka
  tcp-request inspect-delay 5000
  tcp-request content accept if { req_ssl_hello_type 1 }
  use_backend default_broker-mqtt_broker-mqtts-0 if { req_ssl_sni -i broker01.example.com }
  default_backend default_nginx-reject-all-service_broker-mqtts-0


backend default_broker-mqtt_broker-mqtts-0
  mode tcp
  balance roundrobin
  option srvtcpka
  option httpchk
  http-check send meth GET uri /api/v1/health/readiness
  default-server check port 9090
  server SRV_1 100.64.100.72:8883 enabled

As noted, the frontend listens on port 8883. Therefore I cannot create any additional TCP objects that bind to the same port.
Is it possible to omit the frontend part of the CRD and only create the backend?
Is there a workaround to achieve this using the current CRD?

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[jsturmics]

As a workaround I've done this by creating new frontends on a random port. But that's not a good solution. Ideally, the TCP CRD would let you define frontend/backend resources independently.