Add a new transport "IND" (indirect) which publishes a leaseSet hash in the
RouterAddress structure: "IND: [key=aababababababababb]". This transport bids
the lowest priority when the target router publishes it. To send to a peer via
this transport, fetch the leaseset from a ff peer as usual, and send it
directly to the lease.
A peer advertising IND must build and maintain a set of tunnels to another
peer. These are not exploratory tunnels and not client tunnels, but a second
set of router tunnels.
1-hop is sufficient?
How to select peers for these tunnels?
They need to be "non-restricted" but how do you know that? Reachability
mapping? Graph theory, algorithms, data structures may help here. Need to
read up on this. See tunnels TODO.
If you have IND tunnels then your IND transport must bid (low-priority) to
send messages out these tunnels.
