[Xylakant]

Ok, why would I want to do that? Because when Microsoft bought Minecraft they decided to split the ecosystem into the Java Edition (everyone playing on a computer) and Bedrock Edition (Consoles, Tablets, ...) and cross-play is not possible on the official realms. That leaves out the option to just pay and rent a realm for the group.

So we're hosting our own minecraft server and a suitable connector for cross-play - and it's easy to join on tablets, computers and so on because there's a button that allows you to enter an address. But on the switch, Microsoft in its wisdom decided that there'd be no "join random server" button. But there are some official realm servers, and they just happen to host a lobby and the client understands some interface commands sent by the server (1). Some folks in the community devised a great hack - you just host a lobby yourself that presents a list of servers of your choice. But to do that, you need to bend the DNS entries of a few select hostnames that host the "official" lobbies so that they now point to your lobby. Which means you need to run a resolver that is capable of resolving all hostnames, because you need to set it in the switchs networking settings as the primary DNS server.

Now, there are people that run resolvers in the community and that might be one option, but I'm honestly a bit picky about who gets to see what hostnames my kids switch wants to resolve.

Whitelisting networks is impossible - it's residential internet.

The reason I'd be interested in running this behind a VPN is that I don't want to run an open resolver and become part of an amplification attack. (And sadly, the Switch 1 does not have a sufficiently modern DNS stack so that I can just enable DNS cookies and be done with it. The Switch 2 supports it).

Sorry if this sounds complicated. It's just hacks on hacks on hacks. But it works.

(1) judging from the looks and feel, this is actually implemented as a minecraft game interface and the client just treats that as a game server. It even reports the number of players hanging out in the lobby.

[ssl-3]

Thanks. I suspected that this is where things were heading. I don't see a problem with using hacks-on-hacks to get a thing done with closed systems; one does what one must.

On the DNS end, it seems the constraints are shaped like this:

  1.  Provides custom responses for arbitrary DNS requests, and resolves regular [global] DNS
  2.  Works with residential internet
  3.  Uses no open resolvers (because of amplification attacks)
  4.  Works with standalone [Internet-connected] Nintendo Switch devices
  5.  Avoids VPN (because #4 -- Switch doesn't grok VPN)

With that set of rules, I think the idea is constrained completely out of existence. One or more of them need to be relaxed in order for it to get off the ground.

The most obvious one to relax seems to to be #3, open resolvers. If an open resolver is allowed then the rest of the constraints fit just fine.

DNS amplification can be mitigated well-enough for limited-use things like this Minecraft server in various ways, like implementing per-address rate limiting and denying AXFR completely. These kinds of mitigations can be problematic with popular services, but a handful of Switch devices won't trip over them at all.

Or: VPN could be used. But that will require non-zero hardware for remote players (which can be cheap-ish, but not free), and that hardware will need power, and the software running on that hardware will need configured for each WLAN it is needed to work with. That path is something I wouldn't wish upon a network engineer, much less a kid with a portable game console. It's possible, but it's feels like a complete non-starter.

[Xylakant]

Yep, I agree. It's essentially impossible given the contraints. I'm mostly responding to a post that says "just run it on a VPN" with an example that just can't run on a VPN.

(3) would be easy to handle if DNS Cookies were sufficiently well supported because they solve reflection attacks and that's the most prominent. Rate limiting also helps.

At the moment I'm at selectively running the DNS server when the kids want to play because we're still at the supervised pre-planned play-session. And I hope that by the time they plan their own sessions, they've all moved on to a Switch 2.

[MayeulC]

Thank you for the explanation, it was most interesting, I had no idea Bedrock could be coerced into talking to java servers.

Here are a few ideas:

1. Geoblocking. Not ideal, but it can make your resolver public for fewer people.

2. What if your DNS only answers queries for a single domain? Depending on the system, the fallback DNS server may handle other requests?

3. You could always hand out a device that connects to the WLAN. Think a cheap esp32. Only needs to be powered on when doing the resolution. Then you have a bit more freedom: ipv6 RADV + VPN, or try hijacking DNS queries (will not work with client isolation), or set it as resolver (may need manual config on each LAN, impractical).

4. IP whitelist, but ask them to visit a HTTP server from their LAN if it does not work (the switch has a browser, I think), this will give you the IP to allow, you can even password-protect it.

I'd say 2. Is worth a try. 4. Is easy enough to implement, but not entirely frictionless.

[0x00cl]

You could run a DNS server and configure the server with a whitelist of allowed IPs on the network level, so connections are dropped before even reaching your DNS service.

For example, any red-hat based linux distro comes with Firewalld, you could set rules that by default will block all external connections and only allow your kids and their friends IP addresses to connect to your server (and only specifically on port 53). So your DNS server will only receive connections from the whitelisted IPs. Of course the only downside is that if their IP changes, you'll have to troubleshoot and whitelist the new IP, and there is the tiny possibility that they might be behind CGNAT where their IPv4 is shared with another random person, who is looking to exploit DNS servers.

But I'd say that is a pretty good solution, no one will know you are even running a DNS service except for the whitelisted IPs.

[Xylakant]

They're all playing from home, connected to their residential internet. I don't know their IP addresses.

[simoncion]

Correct me if I misunderstand what you're trying to do:

What you want to do is -on each LAN that has a Switch that you want to play on your specific Minecraft server- report that the IP for the hostname of the Minecraft server the Switch would ordinarily connect to is the server that you're hosting?

If you're using OpenWRT, it looks like you can add the relevant entries to '/etc/hosts' on the system and dnsmasq will serve up that name data. [0] I'd be a little shocked (but only a little) if something similar were impossible on all non-OpenWRT consumer-grade routers.

My Switch 1 is more than happy to use the DNS server that DHCP tells it to. I assume the Switch 2 is the same way.

[0] <https://openwrt.org/docs/guide-user/base-system/dhcp.dnsmasq>

[Xylakant]

I can do that for my network - but the group is multiple kids that play from their home. I'm not going to teach all of those parents how to mess with their network. There's just way too many things that can go wrong. Also, won't work if the kid is traveling.

[akdev1l]

From all this what I got is that Microsoft is connecting to some random servers not using TLS and then somehow outputting that data straight into the Nintendo Switch