Envoy is the proxy that does the heavy lifting. Istio is just a glorified configuration system. Even if you choose to use Istio you're still using Envoy.
You might be able to re-use some of that. It should be pretty easy to get metrics for outbound/inbound http requests, but I don't remember the exact yaml incantation.
lol i’m not quite following how manually injecting envoy, “configuring envoy yourself/by hand” in a pod and “copying istio code for iptables re-direction” and then trying to maintain this yourself is easier than just using istio?
You're spot-on about using iptables rules. There is an example here with a yaml configuration and some iptables commands: https://github.com/envoyproxy/envoy/blob/main/configs/origin...
You might be able to re-use some of that. It should be pretty easy to get metrics for outbound/inbound http requests, but I don't remember the exact yaml incantation.