[Bitcoin-development] Tor hidden service support

[grarpamp]

> Additionally, such addresses are exchanged and relayed via the P2P network.
> To do so, we reused the fd87:d87e:eb43::/48 IPv6 range. Each address in this
> 80-bit range is mapped to an onion address, and treated as belonging to a
> separate network. This network range is the same as used by the OnionCat
> application (though we do not use OnionCat in any way), and is part of the
> RFC4193 Unique Local IPv6 range, which is normally not globally routable.
>
> Other clients that wish to implement similar functionality, can use this
> test case: 5wyqrzbvrdsumnok.onion == FD87:D87E:EB43:edb1:8e4:3588:e546:35ca.
> The conversion is simply decoding the base32 onion address, and storing the
> resulting 80 bits of data as low-order bits of an IPv6 address, prefixed by
> fd87:d87e:eb43:. As this range is not routable, there should be no
> compatibility problems: any unaware IPv6-capable code will immediately fail
> when trying to connect.

You are going to want to include the block of the Phatom project as well:
https://code.google.com/p/phantom/
fd00:2522:3493::/48

And the one for 'garlicat' for I2P, which might be more complex due
to I2P's addressing:
fd60:db4d:ddb5::/48

Note that while these blocks are not expected to be routable, that
people may in fact have interfaces, routing tables and packet filters
on their machines configured with up to all three of those networks
for the purposes therein.