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// Copyright (c) 2012 Pieter Wuille
// Copyright (c) 2012-2021 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#ifndef BITCOIN_ADDRMAN_H
#define BITCOIN_ADDRMAN_H
#include <netaddress.h>
#include <protocol.h>
#include <streams.h>
#include <timedata.h>
#include <cstdint>
#include <memory>
#include <optional>
#include <utility>
#include <vector>
class AddrManImpl;
/** Default for -checkaddrman */
static constexpr int32_t DEFAULT_ADDRMAN_CONSISTENCY_CHECKS{0};
/** Stochastic address manager
*
* Design goals:
* * Keep the address tables in-memory, and asynchronously dump the entire table to peers.dat.
* * Make sure no (localized) attacker can fill the entire table with his nodes/addresses.
*
* To that end:
* * Addresses are organized into buckets that can each store up to 64 entries.
* * Addresses to which our node has not successfully connected go into 1024 "new" buckets.
* * Based on the address range (/16 for IPv4) of the source of information, or if an asmap is provided,
* the AS it belongs to (for IPv4/IPv6), 64 buckets are selected at random.
* * The actual bucket is chosen from one of these, based on the range in which the address itself is located.
* * The position in the bucket is chosen based on the full address.
* * One single address can occur in up to 8 different buckets to increase selection chances for addresses that
* are seen frequently. The chance for increasing this multiplicity decreases exponentially.
* * When adding a new address to an occupied position of a bucket, it will not replace the existing entry
* unless that address is also stored in another bucket or it doesn't meet one of several quality criteria
* (see IsTerrible for exact criteria).
* * Addresses of nodes that are known to be accessible go into 256 "tried" buckets.
* * Each address range selects at random 8 of these buckets.
* * The actual bucket is chosen from one of these, based on the full address.
* * When adding a new good address to an occupied position of a bucket, a FEELER connection to the
* old address is attempted. The old entry is only replaced and moved back to the "new" buckets if this
* attempt was unsuccessful.
* * Bucket selection is based on cryptographic hashing, using a randomly-generated 256-bit key, which should not
* be observable by adversaries.
* * Several indexes are kept for high performance. Setting m_consistency_check_ratio with the -checkaddrman
* configuration option will introduce (expensive) consistency checks for the entire data structure.
*/
class AddrMan
{
protected:
const std::unique_ptr<AddrManImpl> m_impl;
public:
explicit AddrMan(std::vector<bool> asmap, bool deterministic, int32_t consistency_check_ratio);
~AddrMan();
template <typename Stream>
void Serialize(Stream& s_) const;
template <typename Stream>
void Unserialize(Stream& s_);
//! Return the number of (unique) addresses in all tables.
size_t size() const;
/**
* Attempt to add one or more addresses to addrman's new table.
*
* @param[in] vAddr Address records to attempt to add.
* @param[in] source The address of the node that sent us these addr records.
* @param[in] nTimePenalty A "time penalty" to apply to the address record's nTime. If a peer
* sends us an address record with nTime=n, then we'll add it to our
* addrman with nTime=(n - nTimePenalty).
* @return true if at least one address is successfully added. */
bool Add(const std::vector<CAddress>& vAddr, const CNetAddr& source, int64_t nTimePenalty = 0);
/**
* Mark an address record as accessible and attempt to move it to addrman's tried table.
*
* @param[in] addr Address record to attempt to move to tried table.
* @param[in] nTime The time that we were last connected to this peer.
* @return true if the address is successfully moved from the new table to the tried table.
*/
bool Good(const CService& addr, int64_t nTime = GetAdjustedTime());
//! Mark an entry as connection attempted to.
void Attempt(const CService& addr, bool fCountFailure, int64_t nTime = GetAdjustedTime());
//! See if any to-be-evicted tried table entries have been tested and if so resolve the collisions.
void ResolveCollisions();
/**
* Randomly select an address in the tried table that another address is
* attempting to evict.
*
* @return CAddress The record for the selected tried peer.
* int64_t The last time we attempted to connect to that peer.
*/
std::pair<CAddress, int64_t> SelectTriedCollision();
/**
* Choose an address to connect to.
*
* @param[in] newOnly Whether to only select addresses from the new table.
* @return CAddress The record for the selected peer.
* int64_t The last time we attempted to connect to that peer.
*/
std::pair<CAddress, int64_t> Select(bool newOnly = false) const;
/**
* Return all or many randomly selected addresses, optionally by network.
*
* @param[in] max_addresses Maximum number of addresses to return (0 = all).
* @param[in] max_pct Maximum percentage of addresses to return (0 = all).
* @param[in] network Select only addresses of this network (nullopt = all).
*
* @return A vector of randomly selected addresses from vRandom.
*/
std::vector<CAddress> GetAddr(size_t max_addresses, size_t max_pct, std::optional<Network> network) const;
/** We have successfully connected to this peer. Calling this function
* updates the CAddress's nTime, which is used in our IsTerrible()
* decisions and gossiped to peers. Callers should be careful that updating
* this information doesn't leak topology information to network spies.
*
* net_processing calls this function when it *disconnects* from a peer to
* not leak information about currently connected peers.
*
* @param[in] addr The address of the peer we were connected to
* @param[in] nTime The time that we were last connected to this peer
*/
void Connected(const CService& addr, int64_t nTime = GetAdjustedTime());
//! Update an entry's service bits.
void SetServices(const CService& addr, ServiceFlags nServices);
const std::vector<bool>& GetAsmap() const;
};
#endif // BITCOIN_ADDRMAN_H
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