This is an optimisation and possible hardening against traffic analysis.
After a new block is mined, we sometimes receive "blockchain.scripthash.subscribe" notifications. If so, this is often due to the just mined block including mempool txs we already knew about.
Normally we would call the "blockchain.scripthash.get_history" RPC, to get full history of the affected scripthash.
Instead now we first optimistically guess that all mempool txs touching this scripthash just got mined and see if by assuming that we can reproduce the announced sh status.
- if yes, we saved a network RTT by not having to call "blockchain.scripthash.get_history"
- if no, we request the history from the server using the RPC
Prevents the client from accidentally connecting to a server on a
different network.
I noticed its possible to connect to mainnet servers on a signet
instance causing the recent peers to get populated with mainnet peers
rendering the wallet instance barely usable. Doing this check should
prevent this and similar issues.
Often when the wallet creates a tx, the flow is:
- create unsigned tx
- sign tx
- broadcast tx, but don't save it in history
- server sends notification that status of a subscribed address changed
- client calls scripthash.get_history
- client sees txid in scripthash.get_history response
- client calls blockchain.transaction.get to request missing tx
Instead, now when we broadcast a tx on an interface, we cache that tx *for that interface*,
and just before calling blockchain.transaction.get, we lookup in the cache.
Hence this will often save a network request.
