Re: Faking the same LAN over the Internet

On Tue, Mar 31, 2020 at 10:34:39AM +0100, Chris Rawnsley wrote:
> In the period of The Great Isolation, a friend and I wish to play
> a game that has LAN-only multiplayer. We, however, live in different
> locations and, more importantly, different LANs. An often cited
> approach to solving this is to set up a VPN and connect the two
> devices to it. This requires that both devices run a VPN client
> that connects to the third device that manages the connection. And
> then, hey presto! You have a "LAN".
>
> The complication I have found is that we are both using a Nintendo
> Switch (NinSw) and this device comes without a VPN client. Initially,
> I thought it would be possible to use a VPN client on a computer
> which was wired in over Ethernet and then share the wireless to the
> NinSw. This setup would be mirrored on the other side. The diagram
> below tries to make this clearer. Search for "Where my thinking"
> to skip over this.
>
>
> |````````````|
> | | .________.
> | | ) ) ) |:| |:|
> |............| `========'
> .---/::::::::::::::\ [NinSw]
> | [laptop]
> |
> [VPN]
> |
> | \ /
> | _\______/_
> `-----| ... |----[uplink]----// mirrored on the other side
> ``````````
> [gateway]
>
>
> Where my thinking comes stuck is how the wired connection is shared
> to the NinSw over wireless. The laptop, running MacOS in the case
> of my friend, will setup its own NAT to isolate the wireless
> connections from the uplink. The NinSw is then unable to receive
> an IP from the VPN and therefore not appear as part of the same
> network.
>
> Ignoring the particular case of how "Internet Connection Sharing"
> works on MacOS, would it be possible to setup some "VPN bridge"
> (yes, I made that up) on OpenBSD where it handles the details of
> the VPN connection but forwards the IP address to another device?
>
> If anyone has more insight into this and can point me in the right
> direction I would be grateful. Similarly if there's been a mistake
> in my thinking please point it out as that could help too.

I'm using OpenBSD IPSec to connect two LAN's (at two locations, with
different ISP's). Have a look at this article:

https://openbsd.fandom.com/wiki/OpenBSD_IPSec_made_easy

This setup has worked flawlessly for me for years now, only occasionally
broken whenever one or both of the ISP's decide to change my dynamically
assigned IP's, upon which I'll have to manually rename one file and
restart the IPSec service. (It happens so seldom that I haven't bothered
looking into how to automate it.)

This setup may require both you and your friend to have an internet
facing OpenBSD gateway situated at/in front of [uplink].

Nice ASCII btw.

Cheers,

Erling


>
> --
> Chris Rawnsley
>
> P.S. the game in question is Civilization 6 and, yes, they very
> annoyingly restricted it to LAN-only multiplayer...