TCP routing

Gateway API is designed to work with multiple protocols and TCPRoute is one such route which allows for managing TCP traffic.

In this example, we have one Gateway resource and two TCPRoute resources that distribute the traffic with the following rules:

• All TCP streams on port 8080 of the Gateway are forwarded to port 6000 of my-foo-service Kubernetes Service.
• All TCP streams on port 8090 of the Gateway are forwarded to port 6000 of my-bar-service Kubernetes Service.

In this example two TCP listeners will be applied to the Gateway in order to route them to two separate backend TCPRoutes, note that the protocol set for the listeners on the Gateway is TCP:

apiVersion: gateway.networking.k8s.io/v1
kind: Gateway
metadata:
  name: my-tcp-gateway
spec:
  gatewayClassName: my-tcp-gateway-class
  listeners:
    - name: foo
      protocol: TCP
      port: 8080
      allowedRoutes:
        kinds:
          - kind: TCPRoute
    - name: bar
      protocol: TCP
      port: 8090
      allowedRoutes:
        kinds:
          - kind: TCPRoute
---
apiVersion: gateway.networking.k8s.io/v1
kind: TCPRoute
metadata:
  name: tcp-app-1
spec:
  parentRefs:
    - name: my-tcp-gateway
      sectionName: foo
  rules:
    - backendRefs:
        - name: my-foo-service
          port: 6000
---
apiVersion: gateway.networking.k8s.io/v1
kind: TCPRoute
metadata:
  name: tcp-app-2
spec:
  parentRefs:
    - name: my-tcp-gateway
      sectionName: bar
  rules:
    - backendRefs:
        - name: my-bar-service
          port: 6000

In the above example we separate the traffic for the two separate backend TCP Services by using the sectionName field in the parentRefs:

spec:
  parentRefs:
    - name: my-tcp-gateway
      sectionName: foo

This corresponds directly with the name in the listeners in the Gateway:

listeners:
  - name: foo
    protocol: TCP
    port: 8080
  - name: bar
    protocol: TCP
    port: 8090

In this way each TCPRoute “attaches” itself to a different port on the Gateway so that the service my-foo-service is taking traffic for port 8080 from outside the cluster and my-bar-service takes the port 8090 traffic.

Note that you can achieve this same result by binding the Routes to the Gateway listeners using the port field in the parentRefs:

spec:
  parentRefs:
    - name: my-tcp-gateway
      port: 8080

Using the port field instead of sectionName for the attachment has the downside of more tightly coupling the relationship between the Gateway and its associated Routes. Refer to Attaching to Gateways for more details.