/root/bitcoin/src/private_broadcast.h

Source
// Copyright (c) 2023-present The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or https://opensource.org/license/mit/.

#ifndef BITCOIN_PRIVATE_BROADCAST_H
#define BITCOIN_PRIVATE_BROADCAST_H

#include <net.h>
#include <primitives/transaction.h>
#include <primitives/transaction_identifier.h>
#include <sync.h>
#include <util/time.h>

#include <optional>
#include <tuple>
#include <unordered_map>
#include <vector>

/**
 * Store a list of transactions to be broadcast privately. Supports the following operations:
 * - Add a new transaction
 * - Remove a transaction
 * - Pick a transaction for sending to one recipient
 * - Query which transaction has been picked for sending to a given recipient node
 * - Mark that a given recipient node has confirmed receipt of a transaction
 * - Query whether a given recipient node has confirmed reception
 * - Query whether any transactions that need sending are currently on the list
 */
class PrivateBroadcast
{
public:

    /// If a transaction is not sent to any peer for this duration,
    /// then we consider it stale / for rebroadcasting.
    static constexpr auto INITIAL_STALE_DURATION{5min};

    /// If a transaction is not received back from the network for this duration
    /// after it is broadcast, then we consider it stale / for rebroadcasting.
    static constexpr auto STALE_DURATION{1min};

    /// Maximum number of transactions tracked simultaneously.
    /// Additions that would exceed this are rejected (see Add()).
    static constexpr size_t MAX_TRANSACTIONS{10'000};

    /// Maximum number of send attempts for a transaction. Once this limit is
    /// reached, the transaction remains tracked but is not sent again unless
    /// explicitly re-added.
    static constexpr size_t MAX_SEND_ATTEMPTS{1'000};

    /// @param[in] max_transactions Cap on the number of simultaneously tracked
    /// transactions. Defaults to MAX_TRANSACTIONS.
    /// @param[in] max_send_attempts Cap on the number of send attempts per
    /// transaction. Defaults to MAX_SEND_ATTEMPTS.
    explicit PrivateBroadcast(size_t max_transactions = MAX_TRANSACTIONS,
                              size_t max_send_attempts = MAX_SEND_ATTEMPTS)
        : m_max_transactions{max_transactions}, m_max_send_attempts{max_send_attempts} {}

    struct PeerSendInfo {
        CService address;
        NodeClock::time_point sent;
        std::optional<NodeClock::time_point> received;
    };

    struct TxBroadcastInfo {
        CTransactionRef tx;
        NodeClock::time_point time_added;
        /// Number of additional send attempts allowed for this transaction (0 if exhausted).
        size_t attempts_remaining;
        std::vector<PeerSendInfo> peers;
    };

    /// Outcome of Add().
    enum class AddResult {
        //! The transaction was newly added or reset after exhausting its send attempts.
        Added,
        //! The transaction was already present with send attempts remaining; no change.
        AlreadyPresent,
        //! Rejected: the queue is already at MAX_TRANSACTIONS.
        QueueFull,
    };

    /**
     * Add a transaction to the storage, or reset an exhausted transaction so it
     * can be broadcast again.
     * @param[in] tx The transaction to add.
     * @return Whether the transaction was newly added or reset, was already
     * present with send attempts remaining, or was rejected because the queue is
     * full (see AddResult).
     */
    [[nodiscard]] AddResult Add(const CTransactionRef& tx)
        EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);

    /**
     * Forget a transaction.
     * @param[in] tx Transaction to forget.
     * @retval !nullopt The number of times the transaction was sent and confirmed
     * by the recipient (if the transaction existed and was removed).
     * @retval nullopt The transaction was not in the storage.
     */
    std::optional<size_t> Remove(const CTransactionRef& tx)
        EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);

    /**
     * Pick the transaction with the fewest send attempts, and confirmations,
     * and oldest send/confirm times.
     * @param[in] will_send_to_nodeid Will remember that the returned transaction
     * was picked for sending to this node. Calling this method more than once with
     * the same `will_send_to_nodeid` is not allowed because sending more than one
     * transaction to one node would be a privacy leak.
     * @param[in] will_send_to_address Address of the peer to which this transaction
     * will be sent.
     * @return Most urgent transaction or nullopt if there are no transactions
     * with send attempts remaining.
     */
    std::optional<CTransactionRef> PickTxForSend(const NodeId& will_send_to_nodeid, const CService& will_send_to_address)
        EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);

    /**
     * Get the transaction that was picked for sending to a given node by PickTxForSend().
     * @param[in] nodeid Node to which a transaction is being (or was) sent.
     * @return Transaction or nullopt if the nodeid is unknown.
     */
    std::optional<CTransactionRef> GetTxForNode(const NodeId& nodeid)
        EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);

    /**
     * Mark that the node has confirmed reception of the transaction we sent it by
     * responding with `PONG` to our `PING` message.
     * @param[in] nodeid Node that we sent a transaction to.
     */
    void NodeConfirmedReception(const NodeId& nodeid)
        EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);

    /**
     * Check if the node has confirmed reception of the transaction.
     * @retval true Node has confirmed, `NodeConfirmedReception()` has been called.
     * @retval false Node has not confirmed, `NodeConfirmedReception()` has not been called.
     */
    bool DidNodeConfirmReception(const NodeId& nodeid)
        EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);

    /**
     * Check if there are transactions with send attempts remaining.
     */
    bool HavePendingTransactions()
        EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);

    /**
     * Get the transactions that have not been broadcast recently and have send
     * attempts remaining.
     */
    std::vector<CTransactionRef> GetStale() const
        EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);

    /**
     * Get stats about all transactions currently being privately broadcast.
     */
    std::vector<TxBroadcastInfo> GetBroadcastInfo() const
        EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);

private:
    /// Status of a transaction sent to a given node.
    struct SendStatus {
        /// Node to which the transaction will be sent (or was sent).
        const NodeId nodeid;
        /// Address of the node.
        const CService address;
        /// When was the transaction picked for sending to the node.
        const NodeClock::time_point picked;
        /// When was the transaction reception confirmed by the node (by PONG).
        std::optional<NodeClock::time_point> confirmed;

        SendStatus(const NodeId& nodeid, const CService& address, const NodeClock::time_point& picked) : nodeid{nodeid}, address{address}, picked{picked} {}
    };

    /// Cumulative stats from all the send attempts for a transaction. Used to prioritize transactions.
    struct Priority {
        size_t num_picked{0}; ///< Number of times the transaction was picked for sending.
        NodeClock::time_point last_picked{}; ///< The most recent time when the transaction was picked for sending.
        size_t num_confirmed{0}; ///< Number of nodes that have confirmed reception of a transaction (by PONG).
        NodeClock::time_point last_confirmed{}; ///< The most recent time when the transaction was confirmed.

        auto operator<=>(const Priority& other) const
        {
            // Invert `other` and `this` in the comparison because smaller num_picked, num_confirmed or
            // earlier times mean greater priority. In other words, if this.num_picked < other.num_picked
            // then this > other.
            return std::tie(other.num_picked, other.num_confirmed, other.last_picked, other.last_confirmed) <=>
                   std::tie(num_picked, num_confirmed, last_picked, last_confirmed);
        }
    };

    /// A pair of a transaction and a sent status for a given node. Convenience return type of GetSendStatusByNode().
    struct TxAndSendStatusForNode {
        const CTransactionRef& tx;
        SendStatus& send_status;
    };

    // No need for salted hasher because we are going to store just a bunch of locally originating transactions.

    struct CTransactionRefHash {
        size_t operator()(const CTransactionRef& tx) const
        {
            return static_cast<size_t>(tx->GetWitnessHash().ToUint256().GetUint64(0));
        }
    };

    struct CTransactionRefComp {
        bool operator()(const CTransactionRef& a, const CTransactionRef& b) const
        {
            return a->GetWitnessHash() == b->GetWitnessHash(); // If wtxid equals, then txid also equals.
        }
    };

    /**
     * Derive the sending priority of a transaction.
     * @param[in] sent_to List of nodes that the transaction has been sent to.
     */
    static Priority DerivePriority(const std::vector<SendStatus>& sent_to);

    /**
     * Find which transaction we sent to a given node (marked by PickTxForSend()).
     * @return That transaction together with the send status or nullopt if we did not
     * send any transaction to the given node.
     */
    std::optional<TxAndSendStatusForNode> GetSendStatusByNode(const NodeId& nodeid)
        EXCLUSIVE_LOCKS_REQUIRED(m_mutex);
    struct TxSendStatus {
        NodeClock::time_point time_added{NodeClock::now()};
        std::vector<SendStatus> send_statuses;
    };
    bool IsPending(const TxSendStatus& status) const;
    /// Cap on the number of simultaneously tracked transactions (see Add()).
    const size_t m_max_transactions;
    /// Cap on the number of send attempts per transaction (see PickTxForSend()).
    const size_t m_max_send_attempts;
    mutable Mutex m_mutex;
    std::unordered_map<CTransactionRef, TxSendStatus, CTransactionRefHash, CTransactionRefComp>
        m_transactions GUARDED_BY(m_mutex);
};

#endif // BITCOIN_PRIVATE_BROADCAST_H

Coverage Report

Created: 2026-08-25 19:02

Line	Count	Source
1		// Copyright (c) 2023-present The Bitcoin Core developers
2		// Distributed under the MIT software license, see the accompanying
3		// file COPYING or https://opensource.org/license/mit/.
4
5		#ifndef BITCOIN_PRIVATE_BROADCAST_H
6		#define BITCOIN_PRIVATE_BROADCAST_H
7
8		#include <net.h>
9		#include <primitives/transaction.h>
10		#include <primitives/transaction_identifier.h>
11		#include <sync.h>
12		#include <util/time.h>
13
14		#include <optional>
15		#include <tuple>
16		#include <unordered_map>
17		#include <vector>
18
19		/**
20		* Store a list of transactions to be broadcast privately. Supports the following operations:
21		* - Add a new transaction
22		* - Remove a transaction
23		* - Pick a transaction for sending to one recipient
24		* - Query which transaction has been picked for sending to a given recipient node
25		* - Mark that a given recipient node has confirmed receipt of a transaction
26		* - Query whether a given recipient node has confirmed reception
27		* - Query whether any transactions that need sending are currently on the list
28		*/
29		class PrivateBroadcast
30		{
31		public:
32
33		/// If a transaction is not sent to any peer for this duration,
34		/// then we consider it stale / for rebroadcasting.
35		static constexpr auto INITIAL_STALE_DURATION{5min};
36
37		/// If a transaction is not received back from the network for this duration
38		/// after it is broadcast, then we consider it stale / for rebroadcasting.
39		static constexpr auto STALE_DURATION{1min};
40
41		/// Maximum number of transactions tracked simultaneously.
42		/// Additions that would exceed this are rejected (see Add()).
43		static constexpr size_t MAX_TRANSACTIONS{10'000};
44
45		/// Maximum number of send attempts for a transaction. Once this limit is
46		/// reached, the transaction remains tracked but is not sent again unless
47		/// explicitly re-added.
48		static constexpr size_t MAX_SEND_ATTEMPTS{1'000};
49
50		/// @param[in] max_transactions Cap on the number of simultaneously tracked
51		/// transactions. Defaults to MAX_TRANSACTIONS.
52		/// @param[in] max_send_attempts Cap on the number of send attempts per
53		/// transaction. Defaults to MAX_SEND_ATTEMPTS.
54		explicit PrivateBroadcast(size_t max_transactions = MAX_TRANSACTIONS,
55		size_t max_send_attempts = MAX_SEND_ATTEMPTS)
56	20.7k	: m_max_transactions{max_transactions}, m_max_send_attempts{max_send_attempts} {}
57
58		struct PeerSendInfo {
59		CService address;
60		NodeClock::time_point sent;
61		std::optional<NodeClock::time_point> received;
62		};
63
64		struct TxBroadcastInfo {
65		CTransactionRef tx;
66		NodeClock::time_point time_added;
67		/// Number of additional send attempts allowed for this transaction (0 if exhausted).
68		size_t attempts_remaining;
69		std::vector<PeerSendInfo> peers;
70		};
71
72		/// Outcome of Add().
73		enum class AddResult {
74		//! The transaction was newly added or reset after exhausting its send attempts.
75		Added,
76		//! The transaction was already present with send attempts remaining; no change.
77		AlreadyPresent,
78		//! Rejected: the queue is already at MAX_TRANSACTIONS.
79		QueueFull,
80		};
81
82		/**
83		* Add a transaction to the storage, or reset an exhausted transaction so it
84		* can be broadcast again.
85		* @param[in] tx The transaction to add.
86		* @return Whether the transaction was newly added or reset, was already
87		* present with send attempts remaining, or was rejected because the queue is
88		* full (see AddResult).
89		*/
90		[[nodiscard]] AddResult Add(const CTransactionRef& tx)
91		EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
92
93		/**
94		* Forget a transaction.
95		* @param[in] tx Transaction to forget.
96		* @retval !nullopt The number of times the transaction was sent and confirmed
97		* by the recipient (if the transaction existed and was removed).
98		* @retval nullopt The transaction was not in the storage.
99		*/
100		std::optional<size_t> Remove(const CTransactionRef& tx)
101		EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
102
103		/**
104		* Pick the transaction with the fewest send attempts, and confirmations,
105		* and oldest send/confirm times.
106		* @param[in] will_send_to_nodeid Will remember that the returned transaction
107		* was picked for sending to this node. Calling this method more than once with
108		* the same `will_send_to_nodeid` is not allowed because sending more than one
109		* transaction to one node would be a privacy leak.
110		* @param[in] will_send_to_address Address of the peer to which this transaction
111		* will be sent.
112		* @return Most urgent transaction or nullopt if there are no transactions
113		* with send attempts remaining.
114		*/
115		std::optional<CTransactionRef> PickTxForSend(const NodeId& will_send_to_nodeid, const CService& will_send_to_address)
116		EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
117
118		/**
119		* Get the transaction that was picked for sending to a given node by PickTxForSend().
120		* @param[in] nodeid Node to which a transaction is being (or was) sent.
121		* @return Transaction or nullopt if the nodeid is unknown.
122		*/
123		std::optional<CTransactionRef> GetTxForNode(const NodeId& nodeid)
124		EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
125
126		/**
127		* Mark that the node has confirmed reception of the transaction we sent it by
128		* responding with `PONG` to our `PING` message.
129		* @param[in] nodeid Node that we sent a transaction to.
130		*/
131		void NodeConfirmedReception(const NodeId& nodeid)
132		EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
133
134		/**
135		* Check if the node has confirmed reception of the transaction.
136		* @retval true Node has confirmed, `NodeConfirmedReception()` has been called.
137		* @retval false Node has not confirmed, `NodeConfirmedReception()` has not been called.
138		*/
139		bool DidNodeConfirmReception(const NodeId& nodeid)
140		EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
141
142		/**
143		* Check if there are transactions with send attempts remaining.
144		*/
145		bool HavePendingTransactions()
146		EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
147
148		/**
149		* Get the transactions that have not been broadcast recently and have send
150		* attempts remaining.
151		*/
152		std::vector<CTransactionRef> GetStale() const
153		EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
154
155		/**
156		* Get stats about all transactions currently being privately broadcast.
157		*/
158		std::vector<TxBroadcastInfo> GetBroadcastInfo() const
159		EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
160
161		private:
162		/// Status of a transaction sent to a given node.
163		struct SendStatus {
164		/// Node to which the transaction will be sent (or was sent).
165		const NodeId nodeid;
166		/// Address of the node.
167		const CService address;
168		/// When was the transaction picked for sending to the node.
169		const NodeClock::time_point picked;
170		/// When was the transaction reception confirmed by the node (by PONG).
171		std::optional<NodeClock::time_point> confirmed;
172
173	12.5k	SendStatus(const NodeId& nodeid, const CService& address, const NodeClock::time_point& picked) : nodeid{nodeid}, address{address}, picked{picked} {}
174		};
175
176		/// Cumulative stats from all the send attempts for a transaction. Used to prioritize transactions.
177		struct Priority {
178		size_t num_picked{0}; ///< Number of times the transaction was picked for sending.
179		NodeClock::time_point last_picked{}; ///< The most recent time when the transaction was picked for sending.
180		size_t num_confirmed{0}; ///< Number of nodes that have confirmed reception of a transaction (by PONG).
181		NodeClock::time_point last_confirmed{}; ///< The most recent time when the transaction was confirmed.
182
183		auto operator<=>(const Priority& other) const
184	26.1k	{
185		// Invert `other` and `this` in the comparison because smaller num_picked, num_confirmed or
186		// earlier times mean greater priority. In other words, if this.num_picked < other.num_picked
187		// then this > other.
188	26.1k	return std::tie(other.num_picked, other.num_confirmed, other.last_picked, other.last_confirmed) <=>
189	26.1k	std::tie(num_picked, num_confirmed, last_picked, last_confirmed);
190	26.1k	}
191		};
192
193		/// A pair of a transaction and a sent status for a given node. Convenience return type of GetSendStatusByNode().
194		struct TxAndSendStatusForNode {
195		const CTransactionRef& tx;
196		SendStatus& send_status;
197		};
198
199		// No need for salted hasher because we are going to store just a bunch of locally originating transactions.
200
201		struct CTransactionRefHash {
202		size_t operator()(const CTransactionRef& tx) const
203	97.7k	{
204	97.7k	return static_cast<size_t>(tx->GetWitnessHash().ToUint256().GetUint64(0));
205	97.7k	}
206		};
207
208		struct CTransactionRefComp {
209		bool operator()(const CTransactionRef& a, const CTransactionRef& b) const
210	6.78k	{
211	6.78k	return a->GetWitnessHash() == b->GetWitnessHash(); // If wtxid equals, then txid also equals.
212	6.78k	}
213		};
214
215		/**
216		* Derive the sending priority of a transaction.
217		* @param[in] sent_to List of nodes that the transaction has been sent to.
218		*/
219		static Priority DerivePriority(const std::vector<SendStatus>& sent_to);
220
221		/**
222		* Find which transaction we sent to a given node (marked by PickTxForSend()).
223		* @return That transaction together with the send status or nullopt if we did not
224		* send any transaction to the given node.
225		*/
226		std::optional<TxAndSendStatusForNode> GetSendStatusByNode(const NodeId& nodeid)
227		EXCLUSIVE_LOCKS_REQUIRED(m_mutex);
228		struct TxSendStatus {
229		NodeClock::time_point time_added{NodeClock::now()};
230		std::vector<SendStatus> send_statuses;
231		};
232		bool IsPending(const TxSendStatus& status) const;
233		/// Cap on the number of simultaneously tracked transactions (see Add()).
234		const size_t m_max_transactions;
235		/// Cap on the number of send attempts per transaction (see PickTxForSend()).
236		const size_t m_max_send_attempts;
237		mutable Mutex m_mutex;
238		std::unordered_map<CTransactionRef, TxSendStatus, CTransactionRefHash, CTransactionRefComp>
239		m_transactions GUARDED_BY(m_mutex);
240		};
241
242		#endif // BITCOIN_PRIVATE_BROADCAST_H