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91 lines
3.8 KiB
C++
91 lines
3.8 KiB
C++
// Copyright (c) 2022 The Bitcoin Core developers
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// Distributed under the MIT software license, see the accompanying
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// file COPYING or http://www.opensource.org/licenses/mit-license.php.
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#ifndef BITCOIN_NODE_TXRECONCILIATION_H
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#define BITCOIN_NODE_TXRECONCILIATION_H
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#include <net.h>
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#include <sync.h>
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#include <memory>
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#include <tuple>
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/** Whether transaction reconciliation protocol should be enabled by default. */
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static constexpr bool DEFAULT_TXRECONCILIATION_ENABLE{false};
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/** Supported transaction reconciliation protocol version */
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static constexpr uint32_t TXRECONCILIATION_VERSION{1};
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enum class ReconciliationRegisterResult {
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NOT_FOUND,
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SUCCESS,
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ALREADY_REGISTERED,
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PROTOCOL_VIOLATION,
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};
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/**
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* Transaction reconciliation is a way for nodes to efficiently announce transactions.
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* This object keeps track of all txreconciliation-related communications with the peers.
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* The high-level protocol is:
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* 0. Txreconciliation protocol handshake.
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* 1. Once we receive a new transaction, add it to the set instead of announcing immediately.
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* 2. At regular intervals, a txreconciliation initiator requests a sketch from a peer, where a
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* sketch is a compressed representation of short form IDs of the transactions in their set.
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* 3. Once the initiator received a sketch from the peer, the initiator computes a local sketch,
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* and combines the two sketches to attempt finding the difference in *sets*.
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* 4a. If the difference was not larger than estimated, see SUCCESS below.
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* 4b. If the difference was larger than estimated, initial txreconciliation fails. The initiator
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* requests a larger sketch via an extension round (allowed only once).
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* - If extension succeeds (a larger sketch is sufficient), see SUCCESS below.
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* - If extension fails (a larger sketch is insufficient), see FAILURE below.
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*
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* SUCCESS. The initiator knows full symmetrical difference and can request what the initiator is
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* missing and announce to the peer what the peer is missing.
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*
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* FAILURE. The initiator notifies the peer about the failure and announces all transactions from
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* the corresponding set. Once the peer received the failure notification, the peer
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* announces all transactions from their set.
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* This is a modification of the Erlay protocol (https://arxiv.org/abs/1905.10518) with two
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* changes (sketch extensions instead of bisections, and an extra INV exchange round), both
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* are motivated in BIP-330.
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*/
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class TxReconciliationTracker
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{
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private:
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class Impl;
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const std::unique_ptr<Impl> m_impl;
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public:
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explicit TxReconciliationTracker(uint32_t recon_version);
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~TxReconciliationTracker();
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/**
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* Step 0. Generates initial part of the state (salt) required to reconcile txs with the peer.
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* The salt is used for short ID computation required for txreconciliation.
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* The function returns the salt.
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* A peer can't participate in future txreconciliations without this call.
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* This function must be called only once per peer.
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*/
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uint64_t PreRegisterPeer(NodeId peer_id);
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/**
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* Step 0. Once the peer agreed to reconcile txs with us, generate the state required to track
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* ongoing reconciliations. Must be called only after pre-registering the peer and only once.
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*/
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ReconciliationRegisterResult RegisterPeer(NodeId peer_id, bool is_peer_inbound,
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uint32_t peer_recon_version, uint64_t remote_salt);
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/**
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* Attempts to forget txreconciliation-related state of the peer (if we previously stored any).
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* After this, we won't be able to reconcile transactions with the peer.
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*/
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void ForgetPeer(NodeId peer_id);
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/**
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* Check if a peer is registered to reconcile transactions with us.
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*/
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bool IsPeerRegistered(NodeId peer_id) const;
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};
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#endif // BITCOIN_NODE_TXRECONCILIATION_H
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