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// Copyright (c) 2012 Pieter Wuille
// Copyright (c) 2012-2022 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 <netgroup.h>
#include <protocol.h>
#include <streams.h>
#include <util/time.h>
#include <cstdint>
#include <memory>
#include <optional>
#include <unordered_set>
#include <utility>
#include <vector>
class InvalidAddrManVersionError : public std::ios_base::failure
{
public:
InvalidAddrManVersionError(std::string msg) : std::ios_base::failure(msg) { }
};
class AddrManImpl;
class AddrInfo;
/** Default for -checkaddrman */
static constexpr int32_t DEFAULT_ADDRMAN_CONSISTENCY_CHECKS{0};
/** Location information for an address in AddrMan */
struct AddressPosition {
// Whether the address is in the new or tried table
const bool tried;
// Addresses in the tried table should always have a multiplicity of 1.
// Addresses in the new table can have multiplicity between 1 and
// ADDRMAN_NEW_BUCKETS_PER_ADDRESS
const int multiplicity;
// If the address is in the new table, the bucket and position are
// populated based on the first source who sent the address.
// In certain edge cases, this may not be where the address is currently
// located.
const int bucket;
const int position;
bool operator==(AddressPosition other) {
return std::tie(tried, multiplicity, bucket, position) ==
std::tie(other.tried, other.multiplicity, other.bucket, other.position);
}
explicit AddressPosition(bool tried_in, int multiplicity_in, int bucket_in, int position_in)
: tried{tried_in}, multiplicity{multiplicity_in}, bucket{bucket_in}, position{position_in} {}
};
/** 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(const NetGroupManager& netgroupman, bool deterministic, int32_t consistency_check_ratio);
~AddrMan();
template <typename Stream>
void Serialize(Stream& s_) const;
template <typename Stream>
void Unserialize(Stream& s_);
/**
* Return size information about addrman.
*
* @param[in] net Select addresses only from specified network (nullopt = all)
* @param[in] in_new Select addresses only from one table (true = new, false = tried, nullopt = both)
* @return Number of unique addresses that match specified options.
*/
size_t Size(std::optional<Network> net = std::nullopt, std::optional<bool> in_new = std::nullopt) const;
/**
* Attempt to add one or more addresses to addrman's new table.
* If an address already exists in addrman, the existing entry may be updated
* (e.g. adding additional service flags). If the existing entry is in the new table,
* it may be added to more buckets, improving the probability of selection.
*
* @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] time_penalty 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 - time_penalty).
* @return true if at least one address is successfully added, or added to an additional bucket. Unaffected by updates. */
bool Add(const std::vector<CAddress>& vAddr, const CNetAddr& source, std::chrono::seconds time_penalty = 0s);
/**
* 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] time 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, NodeSeconds time = Now<NodeSeconds>());
//! Mark an entry as connection attempted to.
void Attempt(const CService& addr, bool fCountFailure, NodeSeconds time = Now<NodeSeconds>());
//! 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.
* seconds The last time we attempted to connect to that peer.
*/
std::pair<CAddress, NodeSeconds> SelectTriedCollision();
/**
* Choose an address to connect to.
*
* @param[in] new_only Whether to only select addresses from the new table. Passing `true` returns
* an address from the new table or an empty pair. Passing `false` will return an
* empty pair or an address from either the new or tried table (it does not
* guarantee a tried entry).
* @param[in] networks Select only addresses of these networks (empty = all). Passing networks may
* slow down the search.
* @return CAddress The record for the selected peer.
* seconds The last time we attempted to connect to that peer.
*/
std::pair<CAddress, NodeSeconds> Select(bool new_only = false, const std::unordered_set<Network>& networks = {}) 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).
* @param[in] filtered Select only addresses that are considered good quality (false = 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 bool filtered = true) const;
/**
* Returns an information-location pair for all addresses in the selected addrman table.
* If an address appears multiple times in the new table, an information-location pair
* is returned for each occurrence. Addresses only ever appear once in the tried table.
*
* @param[in] from_tried Selects which table to return entries from.
*
* @return A vector consisting of pairs of AddrInfo and AddressPosition.
*/
std::vector<std::pair<AddrInfo, AddressPosition>> GetEntries(bool from_tried) 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] time The time that we were last connected to this peer
*/
void Connected(const CService& addr, NodeSeconds time = Now<NodeSeconds>());
//! Update an entry's service bits.
void SetServices(const CService& addr, ServiceFlags nServices);
/** Test-only function
* Find the address record in AddrMan and return information about its
* position.
* @param[in] addr The address record to look up.
* @return Information about the address record in AddrMan
* or nullopt if address is not found.
*/
std::optional<AddressPosition> FindAddressEntry(const CAddress& addr);
};
#endif // BITCOIN_ADDRMAN_H
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