Every peer that we connect to should get the bloom filter set and it
should also get the 'mempool' call sent once which will make that peer
respond with all matches of the bloom filters which are in the mempool.
The tricky part is that we should have the latest bloom filter set on
each of those peers before the mempool is sent, since they work
together.
Also if we are behind, the mempool should not be sent. (It can cause
problems in the wallet if we receive unconfirmed transactions before
mined transactions)
So, when a peer starts downloading merkle blocks, the bloom filter of all
the other peers becomes invalid the moment a match is found by an actual
wallet.
This is Ok on one peer because the merkleblock automatically updates the
filter on match on the server side, but obviously not on the other peers
we have for that wallet.
The approach we follow is that as soon as a sync-run is done on a single
peer (we do a main and also a backup sync), we tell the wallet to re-
build its bloom filter for _all_ peers and if the sync that peer did
leads us to be at the chain-tip, we also send each peer the mempool
command.
Now we have 3 more logically divided interfaces for the listener
pattern (callbacks).
A P2PNetInterface for peers maintainance.
A DataListenerInterface for the sections getting new data.
And last the new HeaderSyncInterface about the state of the
header-chain (application wide).
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.
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.
We reuse the NetworkManager lower level code in order to connect
to the Bitcoin P2P network.
This implements the basics for anyone wanting to be a player on
this network.
tomFlowee
TomZ