I'm looking for software that supports custom UDP proxying/load-balancing based on an external routing table. The general idea is that some external service maintains a routing table (maybe using redis/memcached etc) that maps an downstream IP/Port combo to the address of an upstream internal service. Downstream clients would send all UDP traffic to the load balancer, which should then forward (preserving downstream IP/Port to support Direct Server Return) to the appropriate internal service based on the routing table.
I've looked at a range of existing load balancers (Envoy, Traefik, nginx etc) but can't seem to find any that would do what I need. Is there something out there that satisfies (or can be twisted into satisfying) these requirements?
I found this question which seems quite similar, but still doesn't satisfy my goals fully: UDP load balancing using customised balancing method with session id inside UDP body.
According to this blog, NGINX seems like a good option for providing the transparent proxying & DRS, but I'm not sure how to achieve the custom routing using an external table.
Thanks!