thanks for your reply and sorry for not explaining in detail.
So I will do now.
Tor and I2P are anonymizing tools. http://www.torproject.org/ I2P Anonymous Network - I2P
Both provide a technique to run services like webserver, irc etc. isolated from the internet. But there's a drawback: Addressing is not achieved with IP-addresses. Tor uses 16 character long adresses containing numbers from 2-7 and letters from a-z. I2P uses so called base-32 and base-64 addresses. They are only reachable through a proxy which this anonymizing tools provide. For such servers/services you can point a so called tunnel to your localhost address, thats no big deal but clients only work if they provide proxy support and are able to resolve the addresses through that proxy. Tor only transport TCP.
That brings us to OnionCat and GarliCat. OnionCat
Both are basically the same. OnionCat is for Tor and Garlicat for I2P.
Onion/GarliCat creates a TUN/TAP device, perhaps you know them fom the VPN-World. That device gets a IPv6-address out of the private addres range of IPv6. You can imagine this like a Point-toMultipoint VPN. Its a transparent IP-layer, so it can transport every IP-based data.
I want to run gtk-gnutella insideof I2P without connecting to a single node on the internet.
Thats the reason I want to use IPv6 only but that option doesn't make gtk-gnutella use IPv6 only.
With disutility I mean that it is not needed to connect to internet peers. The oppoisite is the case, I dont want it to connect to internet peers.
But that is not the main problem, to prevent connecting to IPv4 you can use firewalling. The main problem is that you can't bootstrap over IPv6 as far as I see. The best would be If to provide a static ultrapeer list to gtk-gnutella but I think this is not forseen. My hope is that the developers provide something like this for testing purposes and I stumble over it at any time.
Perhaps you know something about that...
And BTW, this is not linux stuff. Tor, I2P and Onion/GarliCat is available for Windows, Mac, Linux and *nix (Unix and Unix like operating systems).