TCP

Set up a TCP listener on your API gateway.

The following guide deploys a sample TCP echo app, sets up a TCP listener on the gateway, and creates a TCPRoute to the sample app.

TCPRoutes are an experimental feature in the upstream Kubernetes Gateway API, and are subject to change.

Before you begin

Follow the Get started guide to install Gloo Gateway.

Install the experimental channel of the Kubernetes Gateway API so that you can use TCPRoutes.

kubectl apply -f https://github.com/kubernetes-sigs/gateway-api/releases/download/v1.1.0/experimental-install.yaml

Deploy the sample TCP echo app.

kubectl apply -f- <<EOF
apiVersion: v1
kind: Pod
metadata:
  labels:
    app: tcp-echo
  name: tcp-echo
  namespace: default
spec:
  containers:
  - image: soloio/tcp-echo:latest
    imagePullPolicy: IfNotPresent
    name: tcp-echo
  restartPolicy: Always
---
apiVersion: v1
kind: Service
metadata:
  labels:
    app: tcp-echo
  name: tcp-echo
  namespace: default
spec:
  ports:
  - name: http
    port: 1025
    protocol: TCP
    targetPort: 1025
  selector:
    app: tcp-echo
EOF

Create a ReferenceGrant to allow TCPRoutes to refer to the TCP echo service.

kubectl apply -f- <<EOF
apiVersion: gateway.networking.k8s.io/v1beta1
kind: ReferenceGrant
metadata:
  name: allow-gw-to-default-service
  namespace: default
spec:
  from:
  - group: gateway.networking.k8s.io
    kind: TCPRoute
    namespace: gloo-system
  to:
  - group: ""  # core API group
    kind: Service
    name: tcp-echo  # Optionally remove this name field to allow any service
EOF

Set up the Gateway for TCP routes

Create a TCP listener so that the gateway can route TCP traffic. In the following example, all TCP streams on port 8000 of the gateway are forwarded to port 1025 of the example TCP echo service.

Create a Gateway resource with a TCP listener.

kubectl apply -f- <<EOF
apiVersion: gateway.networking.k8s.io/v1
kind: Gateway
metadata:
  name: tcp-gateway
  namespace: gloo-system
  labels:
    app: tcp-echo
spec:
  gatewayClassName: gloo-gateway
  listeners:
  - protocol: TCP
    port: 8000
    name: tcp
    allowedRoutes:
      kinds:
      - kind: TCPRoute
EOF

Setting	Description
`spec.gatewayClassName`	The name of the Kubernetes gateway class that you want to use to configure the gateway. When you set up Gloo Gateway, a default gateway class is set up for you. To view the gateway class configuration, see Gateway classes and types.
`spec.listeners`	Configure the listeners for this gateway. In this example, you configure a TCP gateway that listens for incoming traffic on port 8000. The gateway can serve TCPRoutes from any namespace.

Check the status of the gateway to make sure that your configuration is accepted and no conflicts exist in your cluster.

kubectl get gateway tcp-gateway -n gloo-system -o yaml

Example output:

status:
  addresses:
  - type: IPAddress
    value: ${INGRESS_GW_ADDRESS}
  conditions:
  - lastTransitionTime: "2024-11-20T16:01:25Z"
    message: ""
    observedGeneration: 2
    reason: Accepted
    status: "True"
    type: Accepted
  - lastTransitionTime: "2024-11-20T16:01:25Z"
    message: ""
    observedGeneration: 2
    reason: Programmed
    status: "True"
    type: Programmed

Create a TCPRoute resource for the TCP echo app that is served by the gateway that you created.

kubectl apply -f- <<EOF
apiVersion: gateway.networking.k8s.io/v1alpha2
kind: TCPRoute
metadata:
  name: tcp-route-echo
  namespace: gloo-system
  labels:
    app: tcp-echo
spec:
  parentRefs:
    - name: tcp-gateway
      namespace: gloo-system
      sectionName: tcp
  rules:
    - backendRefs:
        - group: ""
          kind: Service
          name: tcp-echo
          port: 1025
          namespace: default
          weight: 1
EOF

Verify that the TCPRoute is applied successfully.

kubectl get tcproute/tcp-route-echo -n gloo-system -o yaml

Example output:

status:
  parents:
  - conditions:
    - lastTransitionTime: "2024-11-21T16:22:52Z"
      message: ""
      observedGeneration: 1
      reason: Accepted
      status: "True"
      type: Accepted
    - lastTransitionTime: "2024-11-21T16:22:52Z"
      message: ""
      observedGeneration: 1
      reason: ResolvedRefs
      status: "True"
      type: ResolvedRefs
    controllerName: solo.io/gloo-gateway
    parentRef:
      group: gateway.networking.k8s.io
      kind: Gateway
      name: tcp-gateway
      sectionName: tcp

Get the external address of the gateway and save it in an environment variable.

export INGRESS_GW_ADDRESS=$(kubectl get svc -n gloo-system gloo-proxy-tcp-gateway -o jsonpath="{.status.loadBalancer.ingress[0]['hostname','ip']}")
echo $INGRESS_GW_ADDRESS

kubectl port-forward deployment/gloo-proxy-tcp-gateway -n gloo-system 8080:8080

Send a TCP request to the external address of the TCP gateway on port 8000. You might use a tool such as telnet or netcat as in the following example.
nc $INGRESS_GW_ADDRESS 8000
nc localhost 8080
Example output:
```
Connection to ${INGRESS_GW_ADDRESS} port 8000 [tcp/irdmi] succeeded!
```
Enter any string to verify that the TCP echo service “echoes,” returning the same string back.
```
hello
```
Example output:
```
hello
hello
```

Cleanup

You can optionally remove the resources that you set up as part of this guide.

kubectl delete -A gateways,tcproutes,pod,svc -l app=tcp-echo

SNI