[rudra]

Excellent !! it can be done using HE GRE tunnel.

I have experimented on this on a lot of different platforms. I even tried to use the firewall on Android phones and configure anyway I liked needed wanted. ( though the problem there is the triggers.. like disconnection or network change tend to ruin all the custom settings and reset the whole thing, requiring a reapplication).

I also did a reverse tethering totally manually.

one can route packets through tor or using vpn to control entry and access. but the issue is the increasing latency. another issue is robustness / fault tolerance.

also it will become hard to start conversations when you want it to start from an incoming request. BGP is better there. or you will have to assign ports on the alternate/ vpn gateway ip for this incoming purpose, if it is a shared ip (on that vps/system). i have seen port multiplexers working for specific ports used to server multiple processes. i dunno if someone can device an ip multiplexer where you can access a background machine directly when you perform some magic ritual on that ip or otherwise you access the front machine. hahah