My situation is as follows: I have a server (A) set up with a VPN connection to a third-party server (B). I have a collection of other servers (C, D, E...) that share the same private network as my VPN-connected server (A).
The third-party server (B) provides a RESTful API that is accessible through HTTP. For instance, from server A I can request some URL:
$ curl http://<server-B-vpn-ip-address>/path/to/whatever
And I will receive a JSON response with the appropriate data.
I want to be able to access server B's API from any server (C, D, E...) by making a call to server A. For instance:
$ curl http://<server-A-private-ip-address>/path/to/whatever
Server A should then forward that request to server B, and it should return the JSON response to whichever server initially requested it.
I've looked at a few possible ways to solve this with iptables without success, but honestly I don't know what the right tool for the job is in this case. Does anyone have any ideas?