Keeping the source IP intact means you'll have troubles routing back the traffic through host B.

Basically host A won't be able to access the internet without going through B, which could not be what you want.

Here's how it works:

On host A:

• add a /32 route to host B public IP through your local ISP gateway (eg. 192.168.1.1)
• setup a wireguard tunnel between A and B
• host A: 172.17.0.1/30
• host B: 172.17.0.2/30
• add a default route to host B wireguard IP

On host B:

• setup wireguard (same config)
• add PAT rules to the firewall so to DNAT incoming requests on the ports you need to 172.17.0.1
• add an SNAT masquerade rule so all outbound request from 172.17.0.1 are NATed with host B public address.

This should do what you need. However, if I may comment it out, I'd say you should give up on carrying the source IP address down to host A. This setup I described is clunky and can fail in many ways. Also I can see no benefits of doing that besides having "pretty logs" on host A. If you really need good logs, I'd suggest setting up a good reverse proxy on host B and forwarding it's logs to a collector on host A.

Tailscale maybe? They have a mode where you can configure a site to site links, you could route the docker networks. https://tailscale.com/kb/1019/subnets

You can do this with a site-to-site wireguard VPN. You will need to set up the proper routing rules on each termination. On the Internet facing side you will want to do DNAT (modifies destination, keeps source) to redirect the incoming traffic to your non- internet facing side through the tunnel. Then on the non- internet facing you need to set up Routing rules to ensure all traffic headed for public IPs is traversing the tunnel. Then back on the Internet facing side you need to SNAT (modify source, keep destination) the traffic coming through the tunnel headed for the Internet. Hopefully this helps. People saying this goes against standards are not really correct as this is a great application for NAT.

I've been looking at setting up something similar and plan on following this guide, and putting Traefik in front of it as a tcp reverse proxy .

https://blog.aiquiral.me/bypass-cgnat

Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:

8 acronyms in this thread; the most compressed thread commented on today has 15 acronyms.

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You could try using ssh reverse proxy and proxy the port to the vps.

Another way is to setup wireguard on the vps, connect the powerfull machine to it and keep it always connected there. ( This isn't really a good options since then all traffic is moved thrkught the vps )

There is also grok I think that's the name.

In general I think ssh reverse port proxy would be a decent way and then you can use a reverse proxy on the vps like nginx or caddy ( you need one that works on the host network )

Preserve the source IP you say, why?

The thing is that if you could (without circumventing the standards) do so then that implies that IP isn't actually a unique identifier, which is needs to be. It would also mean circumventing whitelists / blacklists would be trivial (it's not hard by any means but has some specific requirements).

The correct way to do this, even if there might be some hack you could do to get the actual source IP through, is to put the source in a 'X-Forwarded-For' header.

As for ready solutions I use NetBird which has open source clients for Windows, Linux and Android that I use without issues and it's perfectly self-hostable and easy to integrate with your own IDP.