I want to control/intercept the load balancer traffic using Istio. Istio gives you the ability to add a mixer on a service level but I want to add some code on a higher level just before the request traffic rules get executed. Thus instead of adding actions per service I want to have some actions executed just after the request was received from the load balancer.
As per official Istio Documentation istio-ingressgateway is the main entry point for exposing nested services outside the cluster. Therefore, Istio Gateway collects information about incoming or outgoing HTTP/TCP connections and also specifies the set of ports that should be exposed, the type of protocol to use, etc. Gateway can be applied on the corresponded Envoy sidecar in the Pod through the labels.
Keep in mind that Istio Gateway operates within L4-L6 layers of load balancing and it's not aware of network source provider.
More information about Istio load balancing architecture you can find here.