SSH into private machines from anywhere using Cloudflare Tunnel

Answer: ZeroTier -- on Mac, Linux (home & cloud), Windows, Android

I actually setup DNS entries resolving to private IPs as configured in ZeroTier so I didn't have to login to dig them up but my default DNS provider won't resolve them. I guess newer ZeroTier versions optionally have DNS covered these days but I haven't looked into it.

IIRC, I tried both ZeroTier and Tailscale but at the time Tailscale did not yet have a simple setup to run as an unattended Windows service (and still does not have the equivalent for Mac). Being able to access a machine without staying logged in was table stakes so I decided Tailscale needed more time to bake.

Downsides I'm aware of:

- Less attention to their encryption implementation than the current hotness (WireGuard).

- Did not work with minimal effort from the local public library.

- Mac Activity Monitor shows unexpectedly high amounts of traffic even though I use it very rarely, it's not clear what's going on within that network. As in currently 100's of MB's I can't think of why would have passed through.

- It's 50 hosts + 1 admin per network for free, unlimited networks (unless you setup your own "controller"/proxy).

Re: access control brought up in another comment contrasting exposing only SSH vs. VPN connections, ZeroTier includes some off-puttingly complex access control configuration mechanism I will probably never look into.

Hope this detailed anecdata helps someone, I'm glad to be in a position to try to give back to the community by sharing my experience. Any other ZeroTier gotchas would be appreciated in case I have to dodge something in the future. I debated setting it up as permanent "route-all-internet-access-back-through-home-internet" VPN on my phone but was scared off by the complexity of setting up routing/bridging on the endpoint at home.

So in addition to ZeroTier, I use AutoSSH [1] to setup and maintain a persistent ssh tunnel on a high port on my vps. It's a lot faster than ZeroTier's relay because the vps is in a neighboring city instead of in another country. It's pretty reliable too, automatically reconnect when the tunnel is down. I'm still using ZeroTier for backup connection though.

Simply use `autossh -M 0 -o "ServerAliveInterval 30" -o "ServerAliveCountMax 3" -v -N -R 22222:localhost:22 user@my-vps-domain` to forward port 22222 on your vps into your local machine. I also configured a supervisord instance to automatically start it on my machine so it'll always running.

[1] https://linux.die.net/man/1/autossh