So, I was able to accomplish my goal by adding proxy_ssl_insecure_skip_verify to gateway config and adding a transformation replacing the X-FORWARDED-FOR header IP with the correct one.
Adding routes and messing with iptables within my docker container did not work because of TCP handshake protocol
Is this solution ok or am i tempting fate by using the X-FORWARDED-FOR header. I am pretty new Tyk so i don’t fully know the implications of this. The upstream host seemingly uses that for IP identification.