Simple question, difficult solution. I can’t work it out. I have a server at home with a site-to-site VPN to a server in the cloud. The server in the cloud has a public IP.
I want people to access server in the cloud and it should forward traffic through the VPN. I have tried this and it works. I’ve tried with nginx streams, frp and also HAProxy. They all work, but, in the server at home logs I can only see that people are connecting from the site-to-site VPN, not their actual source IP.
Is there any solution (program/Docker image) that will take a port, forward it to another host (or maybe another program listening on the host) that then modifies the traffic to contain the real source IP. The whole idea is that in the server logs I want to see people’s real IP addresses, not the server in the cloud private VPN IP.
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Short answer no, but you can add the source IP as part of the http header https://www.nginx.com/resources/wiki/start/topics/examples/forwarded/ then you have to log that bit of the header at the app level.
There can be ways of your are using ipv6, basically turning your cloud host into a router, but but ipv4 you would have to have a 1:1 mapping and setup the routing carefully to make it work.
Isn’t that what the logs on the proxy are for?
The way I would solve this is by putting nginx or other reverse proxy directly on your instance in the cloud. You can use this to set one of the well known proxy headers and proxies as others have mentioned and have this then proxy to your backend instances over the VPN (even if it’s pointing to an internal nginx instance). Then the access logs on your cloud instance will also contain the actual IP address of the client, setting headers will obviously only work for HTTP traffic, there really isn’t a similar mechanism for TCP/UDP traffic as those are layer 3 and HTTP is layer 4. If you are concerned about it you can always ship the logs to somewhere on prem as well.
I realised I forgot to update this. Thank you to everyone that contributed, I appreciate it. This was a weird use case and barely anyone online has documented it, only a handful of places. Nevertheless, I figured it out.
So basically, you run HAProxy with the send-proxy-v2 protocol. Let’s say I’m forwarding SSH from VPS to home, I’d have the VPS running HAProxy listening on port 22. Then I’d have it forward to home on port 220. Then, on the home server, you run this amazing piece of software called go-mmproxy. Configure that to listen on port 220 and forward to localhost 22. And there you have it.
HAProxy passes the real source IP to go-mmproxy with the proxy protocol, go-mmproxy takes the proxy header and strips it from the request, spoofs the source IP address from localhost to the real source IP contained in the proxy header then makes the request to localhost. And then you also have to configure traffic to go back through localhost so go-mmproxy can pick it up and add the proxy header back to the request, to be sent back to the source.