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Create redirect URLs

Extract the values of common headers to generate a redirect URL.

About pseudo headers

Pseudo headers are special headers that are used in HTTP/2 to provide metadata about the request or response in a structured way. Although they look like traditional HTTP/1.x headers, they come with specific characteristics:

• Must always start with a colon (:).
• Must appear before regular headers in the HTTP/2 frame.
• Contain details about the request or response.

Common pseudo headers include:

• :method: The HTTP method that is used, such as GET or POST.
• :scheme: The protocol that is used, such as http or https.
• :authority: The hostname and port number that the request is sent to.
• :path: The path of the request.

Before you begin

1. Follow the Get started guide to install kgateway.

2. Follow the Sample app guide to create a gateway proxy with an HTTP listener and deploy the httpbin sample app.

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

   Cloud Provider LoadBalancerPort-forward for local testing

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

   kubectl port-forward deployment/http -n kgateway-system 8080:8080

Set up redirect URLs

1. Create a TrafficPolicy resource with the following transformation rules:

   • Build a redirect URL with the values of the :authority and :path pseudo headers. These headers are extracted from the request with the request_header function that is provided in kgateway.
   • The :authority pseudo header contains the hostname that the request is sent to.
   • The :path pseudo header is set to the request path.
   • The redirect URL is added to the x-forwarded-uri response header.

   kubectl apply -f- <<EOF
   apiVersion: gateway.kgateway.dev/v1alpha1
   kind: TrafficPolicy
   metadata:
     name: transformation
     namespace: httpbin
   spec:
     targetRefs:
     - group: gateway.networking.k8s.io
       kind: HTTPRoute
       name: httpbin
     transformation:
       request:  
         add:
         - name: x-forwarded-uri
           value: 'https://{{ request_header(":authority") }}{{ request_header(":path") }}'
   EOF

2. Send a request to the httpbin app. Verify that you get back a 200 HTTP response code and that you see the redirect URL in the x-forwarded-uri response header.

   Cloud Provider LoadBalancerPort-forward for local testing

   curl -vi http://$INGRESS_GW_ADDRESS:8080/get \
    -H "host: www.example.com:8080" 

   curl -vi localhost:8080/get \
   -H "host: www.example.com" 

   Example output:

   ...
   < HTTP/1.1 200 OK
   HTTP/1.1 200 OK
   ...
   
   {
     "args": {},
     "headers": {
       "Accept": [
         "*/*"
       ],
       "Host": [
         "www.example.com:8080"
       ],
       "User-Agent": [
         "curl/8.7.1"
       ],
       "X-Envoy-Expected-Rq-Timeout-Ms": [
         "15000"
       ],
       "X-Envoy-External-Address": [
         "10.0.9.76"
       ],
       "X-Forwarded-For": [
         "10.0.9.76"
       ],
       "X-Forwarded-Proto": [
         "http"
       ],
       "X-Forwarded-Uri": [
         "https://www.example.com:8080/get"
       ],
       "X-Request-Id": [
         "55140fab-c68e-44d3-a4fc-7f6242ba8194"
       ]
     },
     "origin": "10.0.9.76",
     "url": "http://www.example.com:8080/get"
   }
   

Cleanup

kubectl delete TrafficPolicy transformation -n httpbin