src/addrman.cpp

	// Copyright (c) 2012 Pieter Wuille
	// Copyright (c) 2012-present The Bitcoin Core developers
	// Distributed under the MIT software license, see the accompanying
	// file COPYING or http://www.opensource.org/licenses/mit-license.php.

	#include <bitcoin-build-config.h> // IWYU pragma: keep

	#include <addrman.h>
	#include <addrman_impl.h>

	#include <hash.h>
	#include <logging.h>
	#include <logging/timer.h>
	#include <netaddress.h>
	#include <protocol.h>
	#include <random.h>
	#include <serialize.h>
	#include <streams.h>
	#include <tinyformat.h>
	#include <uint256.h>
	#include <util/check.h>
	#include <util/time.h>

	#include <cmath>
	#include <optional>

	/** Over how many buckets entries with tried addresses from a single group (/16 for IPv4) are spread */
	static constexpr uint32_t ADDRMAN_TRIED_BUCKETS_PER_GROUP{8};
	/** Over how many buckets entries with new addresses originating from a single group are spread */
	static constexpr uint32_t ADDRMAN_NEW_BUCKETS_PER_SOURCE_GROUP{64};
	/** Maximum number of times an address can occur in the new table */
	static constexpr int32_t ADDRMAN_NEW_BUCKETS_PER_ADDRESS{8};
	/** How old addresses can maximally be */
	static constexpr auto ADDRMAN_HORIZON{30 * 24h};
	/** After how many failed attempts we give up on a new node */
	static constexpr int32_t ADDRMAN_RETRIES{3};
	/** How many successive failures are allowed ... */
	static constexpr int32_t ADDRMAN_MAX_FAILURES{10};
	/** ... in at least this duration */
	static constexpr auto ADDRMAN_MIN_FAIL{7 * 24h};
	/** How recent a successful connection should be before we allow an address to be evicted from tried */
	static constexpr auto ADDRMAN_REPLACEMENT{4h};
	/** The maximum number of tried addr collisions to store */
	static constexpr size_t ADDRMAN_SET_TRIED_COLLISION_SIZE{10};
	/** The maximum time we'll spend trying to resolve a tried table collision */
	static constexpr auto ADDRMAN_TEST_WINDOW{40min};

	int AddrInfo::GetTriedBucket(const uint256& nKey, const NetGroupManager& netgroupman) const
	{
	uint64_t hash1 = (HashWriter{} << nKey << GetKey()).GetCheapHash();
	uint64_t hash2 = (HashWriter{} << nKey << netgroupman.GetGroup(*this) << (hash1 % ADDRMAN_TRIED_BUCKETS_PER_GROUP)).GetCheapHash();
	return hash2 % ADDRMAN_TRIED_BUCKET_COUNT;
	}

	int AddrInfo::GetNewBucket(const uint256& nKey, const CNetAddr& src, const NetGroupManager& netgroupman) const
	{
	std::vector<unsigned char> vchSourceGroupKey = netgroupman.GetGroup(src);
	uint64_t hash1 = (HashWriter{} << nKey << netgroupman.GetGroup(*this) << vchSourceGroupKey).GetCheapHash();
	uint64_t hash2 = (HashWriter{} << nKey << vchSourceGroupKey << (hash1 % ADDRMAN_NEW_BUCKETS_PER_SOURCE_GROUP)).GetCheapHash();
	return hash2 % ADDRMAN_NEW_BUCKET_COUNT;
	}

	int AddrInfo::GetBucketPosition(const uint256& nKey, bool fNew, int bucket) const
	{
	uint64_t hash1 = (HashWriter{} << nKey << (fNew ? uint8_t{'N'} : uint8_t{'K'}) << bucket << GetKey()).GetCheapHash();
	return hash1 % ADDRMAN_BUCKET_SIZE;
	}

	bool AddrInfo::IsTerrible(NodeSeconds now) const
	{
	if (now - m_last_try <= 1min) { // never remove things tried in the last minute
	return false;
	}

	if (nTime > now + 10min) { // came in a flying DeLorean
	return true;
	}

	if (now - nTime > ADDRMAN_HORIZON) { // not seen in recent history
	return true;
	}

	if (TicksSinceEpoch<std::chrono::seconds>(m_last_success) == 0 && nAttempts >= ADDRMAN_RETRIES) { // tried N times and never a success
	return true;
	}

	if (now - m_last_success > ADDRMAN_MIN_FAIL && nAttempts >= ADDRMAN_MAX_FAILURES) { // N successive failures in the last week
	return true;
	}

	return false;
	}

	double AddrInfo::GetChance(NodeSeconds now) const
	{
	double fChance = 1.0;

	// deprioritize very recent attempts away
	if (now - m_last_try < 10min) {
	fChance *= 0.01;
	}

	// deprioritize 66% after each failed attempt, but at most 1/28th to avoid the search taking forever or overly penalizing outages.
	fChance *= pow(0.66, std::min(nAttempts, 8));

	return fChance;
	}

	AddrManImpl::AddrManImpl(const NetGroupManager& netgroupman, bool deterministic, int32_t consistency_check_ratio)
	: insecure_rand{deterministic}
	, nKey{deterministic ? uint256{1} : insecure_rand.rand256()}
	, m_consistency_check_ratio{consistency_check_ratio}
	, m_netgroupman{netgroupman}
	{
	for (auto& bucket : vvNew) {
	for (auto& entry : bucket) {
	entry = -1;
	}
	}
	for (auto& bucket : vvTried) {
	for (auto& entry : bucket) {
	entry = -1;
	}
	}
	}

	AddrManImpl::~AddrManImpl()
	{
	nKey.SetNull();
	}

	template <typename Stream>
	void AddrManImpl::Serialize(Stream& s_) const
	{
	LOCK(cs);

	/**
	* Serialized format.
	* * format version byte (@see `Format`)
	* * lowest compatible format version byte. This is used to help old software decide
	* whether to parse the file. For example:
	* * Bitcoin Core version N knows how to parse up to format=3. If a new format=4 is
	* introduced in version N+1 that is compatible with format=3 and it is known that
	* version N will be able to parse it, then version N+1 will write
	* (format=4, lowest_compatible=3) in the first two bytes of the file, and so
	* version N will still try to parse it.
	* * Bitcoin Core version N+2 introduces a new incompatible format=5. It will write
	* (format=5, lowest_compatible=5) and so any versions that do not know how to parse
	* format=5 will not try to read the file.
	* * nKey
	* * nNew
	* * nTried
	* * number of "new" buckets XOR 2**30
	* * all new addresses (total count: nNew)
	* * all tried addresses (total count: nTried)
	* * for each new bucket:
	* * number of elements
	* * for each element: index in the serialized "all new addresses"
	* * asmap checksum
	*
	* 2**30 is xorred with the number of buckets to make addrman deserializer v0 detect it
	* as incompatible. This is necessary because it did not check the version number on
	* deserialization.
	*
	* vvNew, vvTried, mapInfo, mapAddr and vRandom are never encoded explicitly;
	* they are instead reconstructed from the other information.
	*
	* This format is more complex, but significantly smaller (at most 1.5 MiB), and supports
	* changes to the ADDRMAN_ parameters without breaking the on-disk structure.
	*
	* We don't use SERIALIZE_METHODS since the serialization and deserialization code has
	* very little in common.
	*/

	// Always serialize in the latest version (FILE_FORMAT).
	ParamsStream s{s_, CAddress::V2_DISK};

	s << static_cast<uint8_t>(FILE_FORMAT);

	// Increment `lowest_compatible` iff a newly introduced format is incompatible with
	// the previous one.
	static constexpr uint8_t lowest_compatible = Format::V4_MULTIPORT;
	s << static_cast<uint8_t>(INCOMPATIBILITY_BASE + lowest_compatible);

	s << nKey;
	s << nNew;
	s << nTried;

	int nUBuckets = ADDRMAN_NEW_BUCKET_COUNT ^ (1 << 30);
	s << nUBuckets;
	std::unordered_map<nid_type, int> mapUnkIds;
	int nIds = 0;
	for (const auto& entry : mapInfo) {
	mapUnkIds[entry.first] = nIds;
	const AddrInfo& info = entry.second;
	if (info.nRefCount) {
	assert(nIds != nNew); // this means nNew was wrong, oh ow
	s << info;
	nIds++;
	}
	}
	nIds = 0;
	for (const auto& entry : mapInfo) {
	const AddrInfo& info = entry.second;
	if (info.fInTried) {
	assert(nIds != nTried); // this means nTried was wrong, oh ow
	s << info;
	nIds++;
	}
	}
	for (int bucket = 0; bucket < ADDRMAN_NEW_BUCKET_COUNT; bucket++) {
	int nSize = 0;
	for (int i = 0; i < ADDRMAN_BUCKET_SIZE; i++) {
	if (vvNew[bucket][i] != -1)
	nSize++;
	}
	s << nSize;
	for (int i = 0; i < ADDRMAN_BUCKET_SIZE; i++) {
	if (vvNew[bucket][i] != -1) {
	int nIndex = mapUnkIds[vvNew[bucket][i]];
	s << nIndex;
	}
	}
	}
	// Store asmap checksum after bucket entries so that it
	// can be ignored by older clients for backward compatibility.
	s << m_netgroupman.GetAsmapChecksum();
	}

	template <typename Stream>
	void AddrManImpl::Unserialize(Stream& s_)
	{
	LOCK(cs);

	assert(vRandom.empty());

	Format format;
	s_ >> Using<CustomUintFormatter<1>>(format);

	const auto ser_params = (format >= Format::V3_BIP155 ? CAddress::V2_DISK : CAddress::V1_DISK);
	ParamsStream s{s_, ser_params};

	uint8_t compat;
	s >> compat;
	if (compat < INCOMPATIBILITY_BASE) {
	throw std::ios_base::failure(strprintf(
	"Corrupted addrman database: The compat value (%u) "
	"is lower than the expected minimum value %u.",
	compat, INCOMPATIBILITY_BASE));
	}
	const uint8_t lowest_compatible = compat - INCOMPATIBILITY_BASE;
	if (lowest_compatible > FILE_FORMAT) {
	throw InvalidAddrManVersionError(strprintf(
	"Unsupported format of addrman database: %u. It is compatible with formats >=%u, "
	"but the maximum supported by this version of %s is %u.",
	uint8_t{format}, lowest_compatible, CLIENT_NAME, uint8_t{FILE_FORMAT}));
	}

	s >> nKey;
	s >> nNew;
	s >> nTried;
	int nUBuckets = 0;
	s >> nUBuckets;
	if (format >= Format::V1_DETERMINISTIC) {
	nUBuckets ^= (1 << 30);
	}

	if (nNew > ADDRMAN_NEW_BUCKET_COUNT * ADDRMAN_BUCKET_SIZE \|\| nNew < 0) {
	throw std::ios_base::failure(
	strprintf("Corrupt AddrMan serialization: nNew=%d, should be in [0, %d]",
	nNew,
	ADDRMAN_NEW_BUCKET_COUNT * ADDRMAN_BUCKET_SIZE));
	}

	if (nTried > ADDRMAN_TRIED_BUCKET_COUNT * ADDRMAN_BUCKET_SIZE \|\| nTried < 0) {
	throw std::ios_base::failure(
	strprintf("Corrupt AddrMan serialization: nTried=%d, should be in [0, %d]",
	nTried,
	ADDRMAN_TRIED_BUCKET_COUNT * ADDRMAN_BUCKET_SIZE));
	}

	// Deserialize entries from the new table.
	for (int n = 0; n < nNew; n++) {
	AddrInfo& info = mapInfo[n];
	s >> info;
	mapAddr[info] = n;
	info.nRandomPos = vRandom.size();
	vRandom.push_back(n);
	m_network_counts[info.GetNetwork()].n_new++;
	}
	nIdCount = nNew;

	// Deserialize entries from the tried table.
	int nLost = 0;
	for (int n = 0; n < nTried; n++) {
	AddrInfo info;
	s >> info;
	int nKBucket = info.GetTriedBucket(nKey, m_netgroupman);
	int nKBucketPos = info.GetBucketPosition(nKey, false, nKBucket);
	if (info.IsValid()
	&& vvTried[nKBucket][nKBucketPos] == -1) {
	info.nRandomPos = vRandom.size();
	info.fInTried = true;
	vRandom.push_back(nIdCount);
	mapInfo[nIdCount] = info;
	mapAddr[info] = nIdCount;
	vvTried[nKBucket][nKBucketPos] = nIdCount;
	nIdCount++;
	m_network_counts[info.GetNetwork()].n_tried++;
	} else {
	nLost++;
	}
	}
	nTried -= nLost;

	// Store positions in the new table buckets to apply later (if possible).
	// An entry may appear in up to ADDRMAN_NEW_BUCKETS_PER_ADDRESS buckets,
	// so we store all bucket-entry_index pairs to iterate through later.
	std::vector<std::pair<int, int>> bucket_entries;

	for (int bucket = 0; bucket < nUBuckets; ++bucket) {
	int num_entries{0};
	s >> num_entries;
	for (int n = 0; n < num_entries; ++n) {
	int entry_index{0};
	s >> entry_index;
	if (entry_index >= 0 && entry_index < nNew) {
	bucket_entries.emplace_back(bucket, entry_index);
	}
	}
	}

	// If the bucket count and asmap checksum haven't changed, then attempt
	// to restore the entries to the buckets/positions they were in before
	// serialization.
	uint256 supplied_asmap_checksum{m_netgroupman.GetAsmapChecksum()};
	uint256 serialized_asmap_checksum;
	if (format >= Format::V2_ASMAP) {
	s >> serialized_asmap_checksum;
	}
	const bool restore_bucketing{nUBuckets == ADDRMAN_NEW_BUCKET_COUNT &&
	serialized_asmap_checksum == supplied_asmap_checksum};

	if (!restore_bucketing) {
	LogDebug(BCLog::ADDRMAN, "Bucketing method was updated, re-bucketing addrman entries from disk\n");
	}

	for (auto bucket_entry : bucket_entries) {
	int bucket{bucket_entry.first};
	const int entry_index{bucket_entry.second};
	AddrInfo& info = mapInfo[entry_index];

	// Don't store the entry in the new bucket if it's not a valid address for our addrman
	if (!info.IsValid()) continue;

	// The entry shouldn't appear in more than
	// ADDRMAN_NEW_BUCKETS_PER_ADDRESS. If it has already, just skip
	// this bucket_entry.
	if (info.nRefCount >= ADDRMAN_NEW_BUCKETS_PER_ADDRESS) continue;

	int bucket_position = info.GetBucketPosition(nKey, true, bucket);
	if (restore_bucketing && vvNew[bucket][bucket_position] == -1) {
	// Bucketing has not changed, using existing bucket positions for the new table
	vvNew[bucket][bucket_position] = entry_index;
	++info.nRefCount;
	} else {
	// In case the new table data cannot be used (bucket count wrong or new asmap),
	// try to give them a reference based on their primary source address.
	bucket = info.GetNewBucket(nKey, m_netgroupman);
	bucket_position = info.GetBucketPosition(nKey, true, bucket);
	if (vvNew[bucket][bucket_position] == -1) {
	vvNew[bucket][bucket_position] = entry_index;
	++info.nRefCount;
	}
	}
	}

	// Prune new entries with refcount 0 (as a result of collisions or invalid address).
	int nLostUnk = 0;
	for (auto it = mapInfo.cbegin(); it != mapInfo.cend(); ) {
	if (it->second.fInTried == false && it->second.nRefCount == 0) {
	const auto itCopy = it++;
	Delete(itCopy->first);
	++nLostUnk;
	} else {
	++it;
	}
	}
	if (nLost + nLostUnk > 0) {
	LogDebug(BCLog::ADDRMAN, "addrman lost %i new and %i tried addresses due to collisions or invalid addresses\n", nLostUnk, nLost);
	}

	const int check_code{CheckAddrman()};
	if (check_code != 0) {
	throw std::ios_base::failure(strprintf(
	"Corrupt data. Consistency check failed with code %s",
	check_code));
	}
	}

	AddrInfo* AddrManImpl::Find(const CService& addr, nid_type* pnId)
	{
	AssertLockHeld(cs);

	const auto it = mapAddr.find(addr);
	if (it == mapAddr.end())
	return nullptr;
	if (pnId)
	pnId = (it).second;
	const auto it2 = mapInfo.find((*it).second);
	if (it2 != mapInfo.end())
	return &(*it2).second;
	return nullptr;
	}

	AddrInfo* AddrManImpl::Create(const CAddress& addr, const CNetAddr& addrSource, nid_type* pnId)
	{
	AssertLockHeld(cs);

	nid_type nId = nIdCount++;
	mapInfo[nId] = AddrInfo(addr, addrSource);
	mapAddr[addr] = nId;
	mapInfo[nId].nRandomPos = vRandom.size();
	vRandom.push_back(nId);
	nNew++;
	m_network_counts[addr.GetNetwork()].n_new++;
	if (pnId)
	*pnId = nId;
	return &mapInfo[nId];
	}

	void AddrManImpl::SwapRandom(unsigned int nRndPos1, unsigned int nRndPos2) const
	{
	AssertLockHeld(cs);

	if (nRndPos1 == nRndPos2)
	return;

	assert(nRndPos1 < vRandom.size() && nRndPos2 < vRandom.size());

	nid_type nId1 = vRandom[nRndPos1];
	nid_type nId2 = vRandom[nRndPos2];

	const auto it_1{mapInfo.find(nId1)};
	const auto it_2{mapInfo.find(nId2)};
	assert(it_1 != mapInfo.end());
	assert(it_2 != mapInfo.end());

	it_1->second.nRandomPos = nRndPos2;
	it_2->second.nRandomPos = nRndPos1;

	vRandom[nRndPos1] = nId2;
	vRandom[nRndPos2] = nId1;
	}

	void AddrManImpl::Delete(nid_type nId)
	{
	AssertLockHeld(cs);

	assert(mapInfo.contains(nId));
	AddrInfo& info = mapInfo[nId];
	assert(!info.fInTried);
	assert(info.nRefCount == 0);

	SwapRandom(info.nRandomPos, vRandom.size() - 1);
	m_network_counts[info.GetNetwork()].n_new--;
	vRandom.pop_back();
	mapAddr.erase(info);
	mapInfo.erase(nId);
	nNew--;
	}

	void AddrManImpl::ClearNew(int nUBucket, int nUBucketPos)
	{
	AssertLockHeld(cs);

	// if there is an entry in the specified bucket, delete it.
	if (vvNew[nUBucket][nUBucketPos] != -1) {
	nid_type nIdDelete = vvNew[nUBucket][nUBucketPos];
	AddrInfo& infoDelete = mapInfo[nIdDelete];
	assert(infoDelete.nRefCount > 0);
	infoDelete.nRefCount--;
	vvNew[nUBucket][nUBucketPos] = -1;
	LogDebug(BCLog::ADDRMAN, "Removed %s from new[%i][%i]\n", infoDelete.ToStringAddrPort(), nUBucket, nUBucketPos);
	if (infoDelete.nRefCount == 0) {
	Delete(nIdDelete);
	}
	}
	}

	void AddrManImpl::MakeTried(AddrInfo& info, nid_type nId)
	{
	AssertLockHeld(cs);

	// remove the entry from all new buckets
	const int start_bucket{info.GetNewBucket(nKey, m_netgroupman)};
	for (int n = 0; n < ADDRMAN_NEW_BUCKET_COUNT; ++n) {
	const int bucket{(start_bucket + n) % ADDRMAN_NEW_BUCKET_COUNT};
	const int pos{info.GetBucketPosition(nKey, true, bucket)};
	if (vvNew[bucket][pos] == nId) {
	vvNew[bucket][pos] = -1;
	info.nRefCount--;
	if (info.nRefCount == 0) break;
	}
	}
	nNew--;
	m_network_counts[info.GetNetwork()].n_new--;

	assert(info.nRefCount == 0);

	// which tried bucket to move the entry to
	int nKBucket = info.GetTriedBucket(nKey, m_netgroupman);
	int nKBucketPos = info.GetBucketPosition(nKey, false, nKBucket);

	// first make space to add it (the existing tried entry there is moved to new, deleting whatever is there).
	if (vvTried[nKBucket][nKBucketPos] != -1) {
	// find an item to evict
	nid_type nIdEvict = vvTried[nKBucket][nKBucketPos];
	assert(mapInfo.contains(nIdEvict));
	AddrInfo& infoOld = mapInfo[nIdEvict];

	// Remove the to-be-evicted item from the tried set.
	infoOld.fInTried = false;
	vvTried[nKBucket][nKBucketPos] = -1;
	nTried--;
	m_network_counts[infoOld.GetNetwork()].n_tried--;

	// find which new bucket it belongs to
	int nUBucket = infoOld.GetNewBucket(nKey, m_netgroupman);
	int nUBucketPos = infoOld.GetBucketPosition(nKey, true, nUBucket);
	ClearNew(nUBucket, nUBucketPos);
	assert(vvNew[nUBucket][nUBucketPos] == -1);

	// Enter it into the new set again.
	infoOld.nRefCount = 1;
	vvNew[nUBucket][nUBucketPos] = nIdEvict;
	nNew++;
	m_network_counts[infoOld.GetNetwork()].n_new++;
	LogDebug(BCLog::ADDRMAN, "Moved %s from tried[%i][%i] to new[%i][%i] to make space\n",
	infoOld.ToStringAddrPort(), nKBucket, nKBucketPos, nUBucket, nUBucketPos);
	}
	assert(vvTried[nKBucket][nKBucketPos] == -1);

	vvTried[nKBucket][nKBucketPos] = nId;
	nTried++;
	info.fInTried = true;
	m_network_counts[info.GetNetwork()].n_tried++;
	}

	bool AddrManImpl::AddSingle(const CAddress& addr, const CNetAddr& source, std::chrono::seconds time_penalty)
	{
	AssertLockHeld(cs);

	if (!addr.IsRoutable())
	return false;

	nid_type nId;
	AddrInfo* pinfo = Find(addr, &nId);

	// Do not set a penalty for a source's self-announcement
	if (addr == source) {
	time_penalty = 0s;
	}

	if (pinfo) {
	// periodically update nTime
	const bool currently_online{NodeClock::now() - addr.nTime < 24h};
	const auto update_interval{currently_online ? 1h : 24h};
	if (pinfo->nTime < addr.nTime - update_interval - time_penalty) {
	pinfo->nTime = std::max(NodeSeconds{0s}, addr.nTime - time_penalty);
	}

	// add services
	pinfo->nServices = ServiceFlags(pinfo->nServices \| addr.nServices);

	// do not update if no new information is present
	if (addr.nTime <= pinfo->nTime) {
	return false;
	}

	// do not update if the entry was already in the "tried" table
	if (pinfo->fInTried)
	return false;

	// do not update if the max reference count is reached
	if (pinfo->nRefCount == ADDRMAN_NEW_BUCKETS_PER_ADDRESS)
	return false;

	// stochastic test: previous nRefCount == N: 2^N times harder to increase it
	if (pinfo->nRefCount > 0) {
	const int nFactor{1 << pinfo->nRefCount};
	if (insecure_rand.randrange(nFactor) != 0) return false;
	}
	} else {
	pinfo = Create(addr, source, &nId);
	pinfo->nTime = std::max(NodeSeconds{0s}, pinfo->nTime - time_penalty);
	}

	int nUBucket = pinfo->GetNewBucket(nKey, source, m_netgroupman);
	int nUBucketPos = pinfo->GetBucketPosition(nKey, true, nUBucket);
	bool fInsert = vvNew[nUBucket][nUBucketPos] == -1;
	if (vvNew[nUBucket][nUBucketPos] != nId) {
	if (!fInsert) {
	AddrInfo& infoExisting = mapInfo[vvNew[nUBucket][nUBucketPos]];
	if (infoExisting.IsTerrible() \|\| (infoExisting.nRefCount > 1 && pinfo->nRefCount == 0)) {
	// Overwrite the existing new table entry.
	fInsert = true;
	}
	}
	if (fInsert) {
	ClearNew(nUBucket, nUBucketPos);
	pinfo->nRefCount++;
	vvNew[nUBucket][nUBucketPos] = nId;
	const auto mapped_as{m_netgroupman.GetMappedAS(addr)};
	LogDebug(BCLog::ADDRMAN, "Added %s%s to new[%i][%i]\n",
	addr.ToStringAddrPort(), (mapped_as ? strprintf(" mapped to AS%i", mapped_as) : ""), nUBucket, nUBucketPos);
	} else {
	if (pinfo->nRefCount == 0) {
	Delete(nId);
	}
	}
	}
	return fInsert;
	}

	bool AddrManImpl::Good_(const CService& addr, bool test_before_evict, NodeSeconds time)
	{
	AssertLockHeld(cs);

	nid_type nId;

	m_last_good = time;

	AddrInfo* pinfo = Find(addr, &nId);

	// if not found, bail out
	if (!pinfo) return false;

	AddrInfo& info = *pinfo;

	// update info
	info.m_last_success = time;
	info.m_last_try = time;
	info.nAttempts = 0;
	// nTime is not updated here, to avoid leaking information about
	// currently-connected peers.

	// if it is already in the tried set, don't do anything else
	if (info.fInTried) return false;

	// if it is not in new, something bad happened
	if (!Assume(info.nRefCount > 0)) return false;


	// which tried bucket to move the entry to
	int tried_bucket = info.GetTriedBucket(nKey, m_netgroupman);
	int tried_bucket_pos = info.GetBucketPosition(nKey, false, tried_bucket);

	// Will moving this address into tried evict another entry?
	if (test_before_evict && (vvTried[tried_bucket][tried_bucket_pos] != -1)) {
	if (m_tried_collisions.size() < ADDRMAN_SET_TRIED_COLLISION_SIZE) {
	m_tried_collisions.insert(nId);
	}
	// Output the entry we'd be colliding with, for debugging purposes
	auto colliding_entry = mapInfo.find(vvTried[tried_bucket][tried_bucket_pos]);
	LogDebug(BCLog::ADDRMAN, "Collision with %s while attempting to move %s to tried table. Collisions=%d\n",
	colliding_entry != mapInfo.end() ? colliding_entry->second.ToStringAddrPort() : "",
	addr.ToStringAddrPort(),
	m_tried_collisions.size());
	return false;
	} else {
	// move nId to the tried tables
	MakeTried(info, nId);
	const auto mapped_as{m_netgroupman.GetMappedAS(addr)};
	LogDebug(BCLog::ADDRMAN, "Moved %s%s to tried[%i][%i]\n",
	addr.ToStringAddrPort(), (mapped_as ? strprintf(" mapped to AS%i", mapped_as) : ""), tried_bucket, tried_bucket_pos);
	return true;
	}
	}

	bool AddrManImpl::Add_(const std::vector<CAddress>& vAddr, const CNetAddr& source, std::chrono::seconds time_penalty)
	{
	int added{0};
	for (std::vector<CAddress>::const_iterator it = vAddr.begin(); it != vAddr.end(); it++) {
	added += AddSingle(*it, source, time_penalty) ? 1 : 0;
	}
	if (added > 0) {
	LogDebug(BCLog::ADDRMAN, "Added %i addresses (of %i) from %s: %i tried, %i new\n", added, vAddr.size(), source.ToStringAddr(), nTried, nNew);
	}
	return added > 0;
	}

	void AddrManImpl::Attempt_(const CService& addr, bool fCountFailure, NodeSeconds time)
	{
	AssertLockHeld(cs);

	AddrInfo* pinfo = Find(addr);

	// if not found, bail out
	if (!pinfo)
	return;

	AddrInfo& info = *pinfo;

	// update info
	info.m_last_try = time;
	if (fCountFailure && info.m_last_count_attempt < m_last_good) {
	info.m_last_count_attempt = time;
	info.nAttempts++;
	}
	}

	std::pair<CAddress, NodeSeconds> AddrManImpl::Select_(bool new_only, const std::unordered_set<Network>& networks) const
	{
	AssertLockHeld(cs);

	if (vRandom.empty()) return {};

	size_t new_count = nNew;
	size_t tried_count = nTried;

	if (!networks.empty()) {
	new_count = 0;
	tried_count = 0;
	for (auto& network : networks) {
	auto it = m_network_counts.find(network);
	if (it == m_network_counts.end()) {
	continue;
	}
	auto counts = it->second;
	new_count += counts.n_new;
	tried_count += counts.n_tried;
	}
	}

	if (new_only && new_count == 0) return {};
	if (new_count + tried_count == 0) return {};

	// Decide if we are going to search the new or tried table
	// If either option is viable, use a 50% chance to choose
	bool search_tried;
	if (new_only \|\| tried_count == 0) {
	search_tried = false;
	} else if (new_count == 0) {
	search_tried = true;
	} else {
	search_tried = insecure_rand.randbool();
	}

	const int bucket_count{search_tried ? ADDRMAN_TRIED_BUCKET_COUNT : ADDRMAN_NEW_BUCKET_COUNT};

	// Loop through the addrman table until we find an appropriate entry
	double chance_factor = 1.0;
	while (1) {
	// Pick a bucket, and an initial position in that bucket.
	int bucket = insecure_rand.randrange(bucket_count);
	int initial_position = insecure_rand.randrange(ADDRMAN_BUCKET_SIZE);

	// Iterate over the positions of that bucket, starting at the initial one,
	// and looping around.
	int i, position;
	nid_type node_id;
	for (i = 0; i < ADDRMAN_BUCKET_SIZE; ++i) {
	position = (initial_position + i) % ADDRMAN_BUCKET_SIZE;
	node_id = GetEntry(search_tried, bucket, position);
	if (node_id != -1) {
	if (!networks.empty()) {
	const auto it{mapInfo.find(node_id)};
	if (Assume(it != mapInfo.end()) && networks.contains(it->second.GetNetwork())) break;
	} else {
	break;
	}
	}
	}

	// If the bucket is entirely empty, start over with a (likely) different one.
	if (i == ADDRMAN_BUCKET_SIZE) continue;

	// Find the entry to return.
	const auto it_found{mapInfo.find(node_id)};
	assert(it_found != mapInfo.end());
	const AddrInfo& info{it_found->second};

	// With probability GetChance() * chance_factor, return the entry.
	if (insecure_rand.randbits<30>() < chance_factor * info.GetChance() * (1 << 30)) {
	LogDebug(BCLog::ADDRMAN, "Selected %s from %s\n", info.ToStringAddrPort(), search_tried ? "tried" : "new");
	return {info, info.m_last_try};
	}

	// Otherwise start over with a (likely) different bucket, and increased chance factor.
	chance_factor *= 1.2;
	}
	}

	nid_type AddrManImpl::GetEntry(bool use_tried, size_t bucket, size_t position) const
	{
	AssertLockHeld(cs);

	if (use_tried) {
	if (Assume(position < ADDRMAN_BUCKET_SIZE) && Assume(bucket < ADDRMAN_TRIED_BUCKET_COUNT)) {
	return vvTried[bucket][position];
	}
	} else {
	if (Assume(position < ADDRMAN_BUCKET_SIZE) && Assume(bucket < ADDRMAN_NEW_BUCKET_COUNT)) {
	return vvNew[bucket][position];
	}
	}

	return -1;
	}

	std::vector<CAddress> AddrManImpl::GetAddr_(size_t max_addresses, size_t max_pct, std::optional<Network> network, const bool filtered) const
	{
	AssertLockHeld(cs);
	Assume(max_pct <= 100);

	size_t nNodes = vRandom.size();
	if (max_pct != 0) {
	max_pct = std::min(max_pct, size_t{100});
	nNodes = max_pct * nNodes / 100;
	}
	if (max_addresses != 0) {
	nNodes = std::min(nNodes, max_addresses);
	}

	// gather a list of random nodes, skipping those of low quality
	const auto now{Now<NodeSeconds>()};
	std::vector<CAddress> addresses;
	addresses.reserve(nNodes);
	for (unsigned int n = 0; n < vRandom.size(); n++) {
	if (addresses.size() >= nNodes)
	break;

	int nRndPos = insecure_rand.randrange(vRandom.size() - n) + n;
	SwapRandom(n, nRndPos);
	const auto it{mapInfo.find(vRandom[n])};
	assert(it != mapInfo.end());

	const AddrInfo& ai{it->second};

	// Filter by network (optional)
	if (network != std::nullopt && ai.GetNetClass() != network) continue;

	// Filter for quality
	if (ai.IsTerrible(now) && filtered) continue;

	addresses.push_back(ai);
	}
	LogDebug(BCLog::ADDRMAN, "GetAddr returned %d random addresses\n", addresses.size());
	return addresses;
	}

	std::vector<std::pair<AddrInfo, AddressPosition>> AddrManImpl::GetEntries_(bool from_tried) const
	{
	AssertLockHeld(cs);

	const int bucket_count = from_tried ? ADDRMAN_TRIED_BUCKET_COUNT : ADDRMAN_NEW_BUCKET_COUNT;
	std::vector<std::pair<AddrInfo, AddressPosition>> infos;
	for (int bucket = 0; bucket < bucket_count; ++bucket) {
	for (int position = 0; position < ADDRMAN_BUCKET_SIZE; ++position) {
	nid_type id = GetEntry(from_tried, bucket, position);
	if (id >= 0) {
	AddrInfo info = mapInfo.at(id);
	AddressPosition location = AddressPosition(
	from_tried,
	/multiplicity_in=/from_tried ? 1 : info.nRefCount,
	bucket,
	position);
	infos.emplace_back(info, location);
	}
	}
	}

	return infos;
	}

	void AddrManImpl::Connected_(const CService& addr, NodeSeconds time)
	{
	AssertLockHeld(cs);

	AddrInfo* pinfo = Find(addr);

	// if not found, bail out
	if (!pinfo)
	return;

	AddrInfo& info = *pinfo;

	// update info
	const auto update_interval{20min};
	if (time - info.nTime > update_interval) {
	info.nTime = time;
	}
	}

	void AddrManImpl::SetServices_(const CService& addr, ServiceFlags nServices)
	{
	AssertLockHeld(cs);

	AddrInfo* pinfo = Find(addr);

	// if not found, bail out
	if (!pinfo)
	return;

	AddrInfo& info = *pinfo;

	// update info
	info.nServices = nServices;
	}

	void AddrManImpl::ResolveCollisions_()
	{
	AssertLockHeld(cs);

	for (std::set<nid_type>::iterator it = m_tried_collisions.begin(); it != m_tried_collisions.end();) {
	nid_type id_new = *it;

	bool erase_collision = false;

	// If id_new not found in mapInfo remove it from m_tried_collisions
	if (!mapInfo.contains(id_new)) {
	erase_collision = true;
	} else {
	AddrInfo& info_new = mapInfo[id_new];

	// Which tried bucket to move the entry to.
	int tried_bucket = info_new.GetTriedBucket(nKey, m_netgroupman);
	int tried_bucket_pos = info_new.GetBucketPosition(nKey, false, tried_bucket);
	if (!info_new.IsValid()) { // id_new may no longer map to a valid address
	erase_collision = true;
	} else if (vvTried[tried_bucket][tried_bucket_pos] != -1) { // The position in the tried bucket is not empty

	// Get the to-be-evicted address that is being tested
	nid_type id_old = vvTried[tried_bucket][tried_bucket_pos];
	AddrInfo& info_old = mapInfo[id_old];

	const auto current_time{Now<NodeSeconds>()};

	// Has successfully connected in last X hours
	if (current_time - info_old.m_last_success < ADDRMAN_REPLACEMENT) {
	erase_collision = true;
	} else if (current_time - info_old.m_last_try < ADDRMAN_REPLACEMENT) { // attempted to connect and failed in last X hours

	// Give address at least 60 seconds to successfully connect
	if (current_time - info_old.m_last_try > 60s) {
	LogDebug(BCLog::ADDRMAN, "Replacing %s with %s in tried table\n", info_old.ToStringAddrPort(), info_new.ToStringAddrPort());

	// Replaces an existing address already in the tried table with the new address
	Good_(info_new, false, current_time);
	erase_collision = true;
	}
	} else if (current_time - info_new.m_last_success > ADDRMAN_TEST_WINDOW) {
	// If the collision hasn't resolved in some reasonable amount of time,
	// just evict the old entry -- we must not be able to
	// connect to it for some reason.
	LogDebug(BCLog::ADDRMAN, "Unable to test; replacing %s with %s in tried table anyway\n", info_old.ToStringAddrPort(), info_new.ToStringAddrPort());
	Good_(info_new, false, current_time);
	erase_collision = true;
	}
	} else { // Collision is not actually a collision anymore
	Good_(info_new, false, Now<NodeSeconds>());
	erase_collision = true;
	}
	}

	if (erase_collision) {
	m_tried_collisions.erase(it++);
	} else {
	it++;
	}
	}
	}

	std::pair<CAddress, NodeSeconds> AddrManImpl::SelectTriedCollision_()
	{
	AssertLockHeld(cs);

	if (m_tried_collisions.size() == 0) return {};

	std::set<nid_type>::iterator it = m_tried_collisions.begin();

	// Selects a random element from m_tried_collisions
	std::advance(it, insecure_rand.randrange(m_tried_collisions.size()));
	nid_type id_new = *it;

	// If id_new not found in mapInfo remove it from m_tried_collisions
	if (!mapInfo.contains(id_new)) {
	m_tried_collisions.erase(it);
	return {};
	}

	const AddrInfo& newInfo = mapInfo[id_new];

	// which tried bucket to move the entry to
	int tried_bucket = newInfo.GetTriedBucket(nKey, m_netgroupman);
	int tried_bucket_pos = newInfo.GetBucketPosition(nKey, false, tried_bucket);

	const AddrInfo& info_old = mapInfo[vvTried[tried_bucket][tried_bucket_pos]];
	return {info_old, info_old.m_last_try};
	}

	std::optional<AddressPosition> AddrManImpl::FindAddressEntry_(const CAddress& addr)
	{
	AssertLockHeld(cs);

	AddrInfo* addr_info = Find(addr);

	if (!addr_info) return std::nullopt;

	if(addr_info->fInTried) {
	int bucket{addr_info->GetTriedBucket(nKey, m_netgroupman)};
	return AddressPosition(/tried_in=/true,
	/multiplicity_in=/1,
	/bucket_in=/bucket,
	/position_in=/addr_info->GetBucketPosition(nKey, false, bucket));
	} else {
	int bucket{addr_info->GetNewBucket(nKey, m_netgroupman)};
	return AddressPosition(/tried_in=/false,
	/multiplicity_in=/addr_info->nRefCount,
	/bucket_in=/bucket,
	/position_in=/addr_info->GetBucketPosition(nKey, true, bucket));
	}
	}

	size_t AddrManImpl::Size_(std::optional<Network> net, std::optional<bool> in_new) const
	{
	AssertLockHeld(cs);

	if (!net.has_value()) {
	if (in_new.has_value()) {
	return *in_new ? nNew : nTried;
	} else {
	return vRandom.size();
	}
	}
	if (auto it = m_network_counts.find(*net); it != m_network_counts.end()) {
	auto net_count = it->second;
	if (in_new.has_value()) {
	return *in_new ? net_count.n_new : net_count.n_tried;
	} else {
	return net_count.n_new + net_count.n_tried;
	}
	}
	return 0;
	}

	void AddrManImpl::Check() const
	{
	AssertLockHeld(cs);

	// Run consistency checks 1 in m_consistency_check_ratio times if enabled
	if (m_consistency_check_ratio == 0) return;
	if (insecure_rand.randrange(m_consistency_check_ratio) >= 1) return;

	const int err{CheckAddrman()};
	if (err) {
	LogError("ADDRMAN CONSISTENCY CHECK FAILED!!! err=%i", err);
	assert(false);
	}
	}

	int AddrManImpl::CheckAddrman() const
	{
	AssertLockHeld(cs);

	LOG_TIME_MILLIS_WITH_CATEGORY_MSG_ONCE(
	strprintf("new %i, tried %i, total %u", nNew, nTried, vRandom.size()), BCLog::ADDRMAN);

	std::unordered_set<nid_type> setTried;
	std::unordered_map<nid_type, int> mapNew;
	std::unordered_map<Network, NewTriedCount> local_counts;

	if (vRandom.size() != (size_t)(nTried + nNew))
	return -7;

	for (const auto& entry : mapInfo) {
	nid_type n = entry.first;
	const AddrInfo& info = entry.second;
	if (info.fInTried) {
	if (!TicksSinceEpoch<std::chrono::seconds>(info.m_last_success)) {
	return -1;
	}
	if (info.nRefCount)
	return -2;
	setTried.insert(n);
	local_counts[info.GetNetwork()].n_tried++;
	} else {
	if (info.nRefCount < 0 \|\| info.nRefCount > ADDRMAN_NEW_BUCKETS_PER_ADDRESS)
	return -3;
	if (!info.nRefCount)
	return -4;
	mapNew[n] = info.nRefCount;
	local_counts[info.GetNetwork()].n_new++;
	}
	const auto it{mapAddr.find(info)};
	if (it == mapAddr.end() \|\| it->second != n) {
	return -5;
	}
	if (info.nRandomPos < 0 \|\| (size_t)info.nRandomPos >= vRandom.size() \|\| vRandom[info.nRandomPos] != n)
	return -14;
	if (info.m_last_try < NodeSeconds{0s}) {
	return -6;
	}
	if (info.m_last_success < NodeSeconds{0s}) {
	return -8;
	}
	}

	if (setTried.size() != (size_t)nTried)
	return -9;
	if (mapNew.size() != (size_t)nNew)
	return -10;

	for (int n = 0; n < ADDRMAN_TRIED_BUCKET_COUNT; n++) {
	for (int i = 0; i < ADDRMAN_BUCKET_SIZE; i++) {
	if (vvTried[n][i] != -1) {
	if (!setTried.contains(vvTried[n][i]))
	return -11;
	const auto it{mapInfo.find(vvTried[n][i])};
	if (it == mapInfo.end() \|\| it->second.GetTriedBucket(nKey, m_netgroupman) != n) {
	return -17;
	}
	if (it->second.GetBucketPosition(nKey, false, n) != i) {
	return -18;
	}
	setTried.erase(vvTried[n][i]);
	}
	}
	}

	for (int n = 0; n < ADDRMAN_NEW_BUCKET_COUNT; n++) {
	for (int i = 0; i < ADDRMAN_BUCKET_SIZE; i++) {
	if (vvNew[n][i] != -1) {
	if (!mapNew.contains(vvNew[n][i]))
	return -12;
	const auto it{mapInfo.find(vvNew[n][i])};
	if (it == mapInfo.end() \|\| it->second.GetBucketPosition(nKey, true, n) != i) {
	return -19;
	}
	if (--mapNew[vvNew[n][i]] == 0)
	mapNew.erase(vvNew[n][i]);
	}
	}
	}

	if (setTried.size())
	return -13;
	if (mapNew.size())
	return -15;
	if (nKey.IsNull())
	return -16;

	// It's possible that m_network_counts may have all-zero entries that local_counts
	// doesn't have if addrs from a network were being added and then removed again in the past.
	if (m_network_counts.size() < local_counts.size()) {
	return -20;
	}
	for (const auto& [net, count] : m_network_counts) {
	if (local_counts[net].n_new != count.n_new \|\| local_counts[net].n_tried != count.n_tried) {
	return -21;
	}
	}

	return 0;
	}

	size_t AddrManImpl::Size(std::optional<Network> net, std::optional<bool> in_new) const
	{
	LOCK(cs);
	Check();
	auto ret = Size_(net, in_new);
	Check();
	return ret;
	}

	bool AddrManImpl::Add(const std::vector<CAddress>& vAddr, const CNetAddr& source, std::chrono::seconds time_penalty)
	{
	LOCK(cs);
	Check();
	auto ret = Add_(vAddr, source, time_penalty);
	Check();
	return ret;
	}

	bool AddrManImpl::Good(const CService& addr, NodeSeconds time)
	{
	LOCK(cs);
	Check();
	auto ret = Good_(addr, /test_before_evict=/true, time);
	Check();
	return ret;
	}

	void AddrManImpl::Attempt(const CService& addr, bool fCountFailure, NodeSeconds time)
	{
	LOCK(cs);
	Check();
	Attempt_(addr, fCountFailure, time);
	Check();
	}

	void AddrManImpl::ResolveCollisions()
	{
	LOCK(cs);
	Check();
	ResolveCollisions_();
	Check();
	}

	std::pair<CAddress, NodeSeconds> AddrManImpl::SelectTriedCollision()
	{
	LOCK(cs);
	Check();
	auto ret = SelectTriedCollision_();
	Check();
	return ret;
	}

	std::pair<CAddress, NodeSeconds> AddrManImpl::Select(bool new_only, const std::unordered_set<Network>& networks) const
	{
	LOCK(cs);
	Check();
	auto addrRet = Select_(new_only, networks);
	Check();
	return addrRet;
	}

	std::vector<CAddress> AddrManImpl::GetAddr(size_t max_addresses, size_t max_pct, std::optional<Network> network, const bool filtered) const
	{
	LOCK(cs);
	Check();
	auto addresses = GetAddr_(max_addresses, max_pct, network, filtered);
	Check();
	return addresses;
	}

	std::vector<std::pair<AddrInfo, AddressPosition>> AddrManImpl::GetEntries(bool from_tried) const
	{
	LOCK(cs);
	Check();
	auto addrInfos = GetEntries_(from_tried);
	Check();
	return addrInfos;
	}

	void AddrManImpl::Connected(const CService& addr, NodeSeconds time)
	{
	LOCK(cs);
	Check();
	Connected_(addr, time);
	Check();
	}

	void AddrManImpl::SetServices(const CService& addr, ServiceFlags nServices)
	{
	LOCK(cs);
	Check();
	SetServices_(addr, nServices);
	Check();
	}

	std::optional<AddressPosition> AddrManImpl::FindAddressEntry(const CAddress& addr)
	{
	LOCK(cs);
	Check();
	auto entry = FindAddressEntry_(addr);
	Check();
	return entry;
	}

	AddrMan::AddrMan(const NetGroupManager& netgroupman, bool deterministic, int32_t consistency_check_ratio)
	: m_impl(std::make_unique<AddrManImpl>(netgroupman, deterministic, consistency_check_ratio)) {}

	AddrMan::~AddrMan() = default;

	template <typename Stream>
	void AddrMan::Serialize(Stream& s_) const
	{
	m_impl->Serialize<Stream>(s_);
	}

	template <typename Stream>
	void AddrMan::Unserialize(Stream& s_)
	{
	m_impl->Unserialize<Stream>(s_);
	}

	// explicit instantiation
	template void AddrMan::Serialize(HashedSourceWriter<AutoFile>&) const;
	template void AddrMan::Serialize(DataStream&) const;
	template void AddrMan::Unserialize(AutoFile&);
	template void AddrMan::Unserialize(HashVerifier<AutoFile>&);
	template void AddrMan::Unserialize(DataStream&);
	template void AddrMan::Unserialize(HashVerifier<DataStream>&);

	size_t AddrMan::Size(std::optional<Network> net, std::optional<bool> in_new) const
	{
	return m_impl->Size(net, in_new);
	}

	bool AddrMan::Add(const std::vector<CAddress>& vAddr, const CNetAddr& source, std::chrono::seconds time_penalty)
	{
	return m_impl->Add(vAddr, source, time_penalty);
	}

	bool AddrMan::Good(const CService& addr, NodeSeconds time)
	{
	return m_impl->Good(addr, time);
	}

	void AddrMan::Attempt(const CService& addr, bool fCountFailure, NodeSeconds time)
	{
	m_impl->Attempt(addr, fCountFailure, time);
	}

	void AddrMan::ResolveCollisions()
	{
	m_impl->ResolveCollisions();
	}

	std::pair<CAddress, NodeSeconds> AddrMan::SelectTriedCollision()
	{
	return m_impl->SelectTriedCollision();
	}

	std::pair<CAddress, NodeSeconds> AddrMan::Select(bool new_only, const std::unordered_set<Network>& networks) const
	{
	return m_impl->Select(new_only, networks);
	}

	std::vector<CAddress> AddrMan::GetAddr(size_t max_addresses, size_t max_pct, std::optional<Network> network, const bool filtered) const
	{
	return m_impl->GetAddr(max_addresses, max_pct, network, filtered);
	}

	std::vector<std::pair<AddrInfo, AddressPosition>> AddrMan::GetEntries(bool use_tried) const
	{
	return m_impl->GetEntries(use_tried);
	}

	void AddrMan::Connected(const CService& addr, NodeSeconds time)
	{
	m_impl->Connected(addr, time);
	}

	void AddrMan::SetServices(const CService& addr, ServiceFlags nServices)
	{
	m_impl->SetServices(addr, nServices);
	}

	std::optional<AddressPosition> AddrMan::FindAddressEntry(const CAddress& addr)
	{
	return m_impl->FindAddressEntry(addr);
	}

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