Rewriting hosts

Kong Ingress Controller provides two annotations for manipulating the Host header. These annotations allow for three different behaviours:

• Preserve the user-provided Host header
• Default to the Host of the upstream service
• Explicitly set the Host header to a known value

Preserve the Host header

Kong Ingress Controller preserves the hostname in the request by default.

curl -H 'Host:kong.example' "$PROXY_IP/echo?details=true"

HTTP request details
---------------------
Protocol: HTTP/1.1
Host: kong.example
Method: GET
URL: /?details=true

The Host header in the request to the upstream matches the Host header in the request to Kong Gateway.

Use the upstream Host name

You can disable preserve-host if you want the Host header to contain the upstream hostname of your service.

Add the konghq.com/preserve-host annotation to your Route:

kubectl patch httproute NAME --type merge -p '{"metadata":{"annotations":{"konghq.com/preserve-host":"false"}}}'

kubectl patch ingress NAME -p '{"metadata":{"annotations":{"konghq.com/preserve-host":"false"}}}'

The Host header in the response now contains the upstream host and port.

HTTP request details
---------------------
Protocol: HTTP/1.1
Host: 192.168.194.11:1027
Method: GET
URL: /?details=true

Set the Host header explicitly

Using Gateway API v3.2+

You can set the Host header explicitly when using Gateway API’s HTTPRoute with URLRewrite filter’s hostname field. You only need to add a URLRewrite filter to your HTTPRoute rule.

...
filters:
- type: URLRewrite
  urlRewrite:
    hostname: internal.myapp.example.com

Using the konghq.com/host-header annotation

You can set the Host header explicitly if needed by disabling konghq.com/preserve-host and setting the konghq.com/host-header annotation.

1. Add the konghq.com/preserve-host annotation to your Ingress, to disable preserve-host and send the hostname provided in the host-header annotation:

   Gateway API Ingress

   kubectl patch httproute NAME --type merge -p '{"metadata":{"annotations":{"konghq.com/preserve-host":"false"}}}'

   kubectl patch ingress NAME -p '{"metadata":{"annotations":{"konghq.com/preserve-host":"false"}}}'

2. Add the konghq.com/host-header annotation to your Service, which sets the Host header directly:

   kubectl patch service NAME -p '{"metadata":{"annotations":{"konghq.com/host-header":"internal.myapp.example.com"}}}'
   

3. Make a curl request with a Host header:

   curl -H 'Host:kong.example' "$PROXY_IP/echo?details=true"
   

   The request upstream now uses the header from the host-header annotation:

   HTTP request details
   ---------------------
   Protocol: HTTP/1.1
   Host: internal.myapp.example.com:1027
   Method: GET
   URL: /?details=true