This is done in several steps:
1. Separate my height from the remote peer heights.
Instead of assuming we have one height, recognize that a peer may
not be at the tip at the same time we are. We monitor headers/invs
to update the 'peerHeight' variable.
2. Ask for merkle blocks from a peer to the maximum height of that
peer (but not later than what we validated to be true).
This avoids us asking past the remotes tip which they didn't like.
3. Redo the SyncSPVAction to use all this and make it much more
reliable in finding peers to download from and getting all the
changes as fast as possible.
In most cases headers would be automatically downloaded if we didn't
connect to that peer for a while, but that is not a guarentee so lets
make sure we actually start downloading headers from any peer we can :)
We connect to the "first" priority stated segments first, in order to
allow the UX to be made much better since it may take a bit of time to
find peers.
To send out transactions in the p2p net is quite a lot of work,
you need to find multiple peers to send the transaction to. First
you send an INV, then you respond to a getData to actually send
the transaction and last you wait for 'reject' messages that may
indicate that there is something wrong with the transaction.
This introduces the BroadcastTxData class that wraps a transaction
and gets callbacks for sending and for rejects, abstracting away
all the complexity for the user.
The uint256 and CKeyID classes are the same baseclass with template
differences only, which makes them fragile to use for overloading.
As such rename the convenience overload slightly.
Based on the idea that randomly selecting a peer from our database will
prioritize based on the peers punishment score, this sets the punishment
for never connected-to peers at 10 (out of 1000) just to give a minor
benefit to speeding up the meshing.
this adds a listener interface and a way to emit the callbacks on
changing of the filter.
This also adds a mutex since we expect the Peer to use the filter which
will likely live in its own thread.
This makes the class thread safe and re-entrant.
Notice that we use a recursive mutex to allow various usecase on
altering the bloom filter.
The most involved one is a complete replacement which calls clear and
then various calls to add() style methods.
Second is a single 'add' which can be done without the clear first.
The second needs an explicit lock in the add() methods, which would
deadlock in the first usecase if I didn't pick the recursive mutex.
Instead of forwarding one transaction at a time as the peer sends them
to us, bundle them in a group of transactions known to be merkle-checked
and all belonging together in one block.
Since the peer has no obligation (and with CTOR even less) to send the
transactions in natural order, we should get them per block so we know
all transactions forwarded have parents.
This helps when SPV wallets are still behind on merkle-blocks while the
wallet shut down.
We start instantly again, instead of waiting for the first block to be
mined.
This avoids a peer once sending acceptable headers and never
being bothered again. Instead we now check regularly and keep
track of when the peer was known to follow the same chain as us.
TomZ