You are browsing documentation for an older version. See the latest documentation here.

Exposing a TCP Service

Overview

Create TCP routing configuration for Kong Gateway in Kubernetes using either the TCPIngress custom resource or TCPRoute and TLSRoute Gateway APIs resource.

TCP-based Ingress means that Kong Gateway simply forwards the TCP stream to a Pod of a Service that’s running inside Kubernetes. Kong Gateway does not perform any sort of transformations.

There are two modes available:

• Port based routing: Kong Gateway simply proxies all traffic it receives on a specific port to the Kubernetes Service. TCP connections are load balanced across all the available Pods of the Service.
• SNI based routing: {site.base_gateway}} accepts a TLS-encrypted stream at the specified port and can route traffic to different services based on the SNI present in the TLS handshake. Kong Gateway also terminates the TLS handshake and forward the TCP stream to the Kubernetes Service.

Expose additional ports

Kong Gateway does not include any TCP listen configuration by default. To expose TCP listens, update the Deployment’s environment variables and port configuration.

1. Update the Deployment.

    kubectl patch deploy -n kong kong-gateway --patch '{
      "spec": {
        "template": {
          "spec": {
            "containers": [
              {
                "name": "proxy",
                "env": [
                  {
                    "name": "KONG_STREAM_LISTEN",
                    "value": "0.0.0.0:9000, 0.0.0.0:9443 ssl"
                  }
                ],
                "ports": [
                  {
                    "containerPort": 9000,
                    "name": "stream9000",
                    "protocol": "TCP"
                  },
                  {
                    "containerPort": 9443,
                    "name": "stream9443",
                    "protocol": "TCP"
                  }
                ]
              }
            ]
          }
        }
      }
    }'
   

   The results should look like this:

    deployment.apps/kong-gateway patched
   

   The ssl parameter after the 9443 listen instructs Kong Gateway to expect TLS-encrypted TCP traffic on that port. The 9000 listen has no parameters, and expects plain TCP traffic.

2. Update the proxy Service to indicate the new ports.

   kubectl patch service -n kong kong-gateway-proxy --patch '{
     "spec": {
       "ports": [
         {
           "name": "stream9000",
           "port": 9000,
           "protocol": "TCP",
           "targetPort": 9000
         },
         {
           "name": "stream9443",
           "port": 9443,
           "protocol": "TCP",
           "targetPort": 9443
         }
       ]
     }
   }'
   

   The results should look like this:

   service/kong-gateway-proxy patched
   

3. Configure TCPRoute (Gateway API Only)

   If you are using the Gateway APIs (TCPRoute), your Gateway needs additional configuration under listeners.

   kubectl patch --type=json gateway kong -p='[
       {
           "op":"add",
           "path":"/spec/listeners/-",
           "value":{
               "name":"stream9000",
               "port":9000,
               "protocol":"TCP"
           }
       },
       {
           "op":"add",
           "path":"/spec/listeners/-",
           "value":{
               "name":"stream9443",
               "port":9443,
               "protocol":"TLS",
               "hostname":"tls9443.kong.example",
               "tls": {
                   "certificateRefs":[{
                       "group":"",
                       "kind":"Secret",
                       "name":"tls9443.kong.example"
                    }]
               }
           }
       }
   ]'
   

   The results should look like this:

   gateway.gateway.networking.k8s.io/kong patched
   

Install TCP echo service

Install an example TCP service:

kubectl apply -f https://docs.konghq.com/assets/kubernetes-ingress-controller/examples/echo-service.yaml

The results should look like this:

service/echo created
deployment.apps/echo created

Route based on ports

To expose the service to the outside world, create a TCPIngress resource.

echo "apiVersion: configuration.konghq.com/v1beta1
kind: TCPIngress
metadata:
  name: echo-plaintext
  annotations:
    kubernetes.io/ingress.class: kong
spec:
  rules:
  - port: 9000
    backend:
      serviceName: echo
      servicePort: 1025
" | kubectl apply -f -

tcpingress.configuration.konghq.com/echo-plaintext created

echo "apiVersion: gateway.networking.k8s.io/v1alpha2
kind: TCPRoute
metadata:
  name: echo-plaintext
spec:
  parentRefs:
  - name: kong
  rules:
  - backendRefs:
    - name: echo
      port: 1025
" | kubectl apply -f -

tcproute.gateway.networking.k8s.io/echo-plaintext created

This configuration instructs Kong Gateway to forward all traffic it receives on port 9000 to echo service on port 1025.

Test the configuration

1. Check if the Service is ready on the route.

   Ingress

   Gateway API

   kubectl get tcpingress

   kubectl get tcproute echo-plaintext -ojsonpath='{.status.parents[0].conditions[?(@.reason=="Accepted")]}'

   The results should look like this:

   Ingress

   Gateway API

   NAME             ADDRESS        AGE
   echo-plaintext   <PROXY_IP>   3m18s
   

   {"lastTransitionTime":"2022-11-14T19:48:51Z","message":"","observedGeneration":2,"reason":"Accepted","status":"True","type":"Accepted"}
   

2. Connect to this service using telnet.

    $ telnet $PROXY_IP 9000
   

   After you connect, type some text that you want as a response from the echo Service. To exit, press ctrl+] then ctrl+d.

    Trying 35.247.39.83...
    Connected to 35.247.39.83.
    Escape character is '^]'.
    Welcome, you are connected to node gke-harry-k8s-dev-pool-1-e9ebab5e-c4gw.
    Running on Pod echo-844545646c-gvmkd.
    In namespace default.
    With IP address 10.60.1.17.
    This text will be echoed back.
    This text will be echoed back.
    ^]
    telnet> Connection closed.
   

   The echo Service is now available outside the Kubernetes cluster through Kong Gateway.

Route based on SNI

The routing configuration can include a certificate to present when clients connect over HTTPS. This is not required, as Kong Gateway will serve a default certificate if it cannot find another, but including TLS configuration along with routing configuration is typical.

1. Create a test certificate for the tls9443.kong.example hostname.

   OpenSSL 1.1.1

   OpenSSL 0.9.8

   openssl req -subj '/CN=tls9443.kong.example' -new -newkey rsa:2048 -sha256 \
     -days 365 -nodes -x509 -keyout server.key -out server.crt \
     -addext "subjectAltName = DNS:tls9443.kong.example" \
     -addext "keyUsage = digitalSignature" \
     -addext "extendedKeyUsage = serverAuth" 2> /dev/null;
     openssl x509 -in server.crt -subject -noout

   openssl req -subj '/CN=tls9443.kong.example' -new -newkey rsa:2048 -sha256 \
     -days 365 -nodes -x509 -keyout server.key -out server.crt \
     -extensions EXT -config <( \
      printf "[dn]\nCN=tls9443.kong.example\n[req]\ndistinguished_name = dn\n[EXT]\nsubjectAltName=DNS:tls9443.kong.example\nkeyUsage=digitalSignature\nextendedKeyUsage=serverAuth") 2>/dev/null;
     openssl x509 -in server.crt -subject -noout

   The results should look like this:

   OpenSSL 1.1.1

   OpenSSL 0.9.8

   subject=CN = tls9443.kong.example

   subject=CN = tls9443.kong.example

   Older OpenSSL versions, including the version provided with OS X Monterey, require using the alternative version of this command.

2. Create a Secret containing the certificate.

    kubectl create secret tls tls9443.kong.example --cert=./server.crt --key=./server.key
   

   The results should look like this:

    secret/tls9443.kong.example created
   

3. Create the TCPIngress resource to route TLS-encrypted traffic to the echo service.

   Ingress

   Gateway API

   echo "apiVersion: configuration.konghq.com/v1beta1
   kind: TCPIngress
   metadata:
     name: echo-tls
     annotations:
       kubernetes.io/ingress.class: kong
   spec:
     tls:
     - hosts:
       - tls9443.kong.example
       secretName: tls9443.kong.example
     rules:
     - host: tls9443.kong.example
       port: 9443
       backend:
         serviceName: echo
         servicePort: 1025
   " | kubectl apply -f -

   echo "apiVersion: gateway.networking.k8s.io/v1alpha2
   kind: TLSRoute
   metadata:
     name: echo-tls
   spec:
     parentRefs:
     - name: kong
     hostnames:
     - tls9443.kong.example
     rules:
     - backendRefs:
       - name: echo
         port: 9443
   " | kubectl apply -f -

   The results should look like this:

   Ingress

   Gateway API

   tcpingress.configuration.konghq.com/echo-tls created

   tcproute.gateway.networking.k8s.io/echo-tls created

Test the configuration

You can now access the echo service on port 9443 with SNI tls9443.kong.example.

In real-world usage, you would create a DNS record for tls9443.kong.examplepointing to your proxy Service’s public IP address, which causes TLS clients to add SNI automatically. For this demo, add it manually using the OpenSSL CLI.

echo "hello" | openssl s_client -connect $PROXY_IP:9443 -servername tls9443.kong.example -quiet 2>/dev/null 

Press Ctrl+C to exit.

The results should look like this:

Welcome, you are connected to node kind-control-plane.
Running on Pod echo-5f44d4c6f9-krnhk.
In namespace default.
With IP address 10.244.0.26.
hello