If you've already terminated SSL, you can do this easily by using iptables nflog rule to duplicate traffic and send it to mitmproxy. Or you can setup a transpar

If you've already terminated SSL, you can do this easily by using iptables nflog rule to duplicate traffic and send it to mitmproxy. Or you can setup a transparent proxy (but sounds like that violates your requirement). Either way, if SSL is not terminated you're not going to be able to do much.