// Copyright (c) 2012 Pieter Wuille
// Copyright (c) 2012-2016 The Bitcoin Core developers
// Copyright (c) 2017-2025 The Bitcoin developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#pragma once

#include <clientversion.h>
#include <fs.h>
#include <hash.h>
#include <netaddress.h>
#include <protocol.h>
#include <random.h>
#include <streams.h>
#include <sync.h>
#include <timedata.h>
#include <tinyformat.h>
#include <util/system.h>

#include <cstdint>
#include <iostream>
#include <map>
#include <set>
#include <utility>
#include <vector>

/**
 * User-defined type for the internally used nIds
 * This used to be int, making it feasible for attackers to cause an overflow,
 * see https://bitcoincore.org/en/2024/07/31/disclose-addrman-int-overflow/
 */
class NidType {
    int64_t value = -1;
public:
    /// Default constructed NidType is always invalid
    NidType() noexcept = default;

    /// Returns true iff the contained value is valid
    bool IsValid() const { return value >= 0; }

    bool operator<(const NidType &o) const noexcept { return value < o.value; }
    bool operator==(const NidType &o) const noexcept { return value == o.value; }
    bool operator!=(const NidType &o) const noexcept { return ! this->operator==(o); }

protected:
    // Below methods are used internally by CAddrMan
    friend class CAddrMan;

    explicit NidType(int64_t val) noexcept : value{val} {}

    int64_t Get() const { return value; }
    void Set(int64_t val) { value = val; }
    void SetInvalid() noexcept { value = -1; }

    NidType operator++(int) noexcept { return NidType(value++); } // postfix increment
    NidType &operator++() noexcept { ++value; return *this; } // prefix increment
};

/**
 * Extended statistics about a CAddress
 */
class CAddrInfo : public CAddress {
public:
    //! last try whatsoever by us (memory only)
    int64_t nLastTry{0};

    //! last counted attempt (memory only)
    int64_t nLastCountAttempt{0};

private:
    //! where knowledge about this address first came from
    CNetAddr source;

    //! last successful connection by us
    int64_t nLastSuccess{0};

    //! connection attempts since last successful attempt
    int nAttempts{0};

    //! reference count in new sets (memory only)
    int nRefCount{0};

    //! in tried set? (memory only)
    bool fInTried{false};

    //! position in vRandom
    int nRandomPos{-1};

    friend class CAddrMan;

public:
    SERIALIZE_METHODS(CAddrInfo, obj) {
        READWRITEAS(CAddress, obj);
        READWRITE(obj.source, obj.nLastSuccess, obj.nAttempts);
    }

    CAddrInfo(const CAddress &addrIn, const CNetAddr &addrSource)
        : CAddress(addrIn), source(addrSource) {}

    CAddrInfo() : CAddress(), source() {}

    //! Calculate in which "tried" bucket this entry belongs
    int GetTriedBucket(const uint256 &nKey, const std::vector<bool> &asmap) const;

    //! Calculate in which "new" bucket this entry belongs, given a certain
    //! source
    int GetNewBucket(const uint256 &nKey, const CNetAddr &src, const std::vector<bool> &asmap) const;

    //! Calculate in which "new" bucket this entry belongs, using its default
    //! source
    int GetNewBucket(const uint256 &nKey, const std::vector<bool> &asmap) const {
        return GetNewBucket(nKey, source, asmap);
    }

    //! Calculate in which position of a bucket to store this entry.
    int GetBucketPosition(const uint256 &nKey, bool fNew, int nBucket) const;

    //! Determine whether the statistics about this entry are bad enough so that
    //! it can just be deleted
    bool IsTerrible(int64_t nNow = GetAdjustedTime()) const;

    //! Calculate the relative chance this entry should be given when selecting
    //! nodes to connect to
    double GetChance(int64_t nNow = GetAdjustedTime()) const;
};

/** 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.
 *    * Addresses that have not yet been tried go into 1024 "new" buckets.
 *      * Based on the address range (/16 for IPv4) of the source of
 * information, 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.
 *      * 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 a full bucket, a randomly chosen entry
 * (with a bias favoring less recently seen
 *        ones) is removed from it first.
 *    * 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 a full bucket, a randomly chosen
 * entry (with a bias favoring less recently
 *        tried ones) is evicted from it, back to the "new" buckets.
 *    * 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. Defining DEBUG_ADDRMAN
 * will introduce frequent (and expensive)
 *      consistency checks for the entire data structure.
 */

//! total number of buckets for tried addresses
#define ADDRMAN_TRIED_BUCKET_COUNT_LOG2 8

//! total number of buckets for new addresses
#define ADDRMAN_NEW_BUCKET_COUNT_LOG2 10

//! maximum allowed number of entries in buckets for new and tried addresses
#define ADDRMAN_BUCKET_SIZE_LOG2 6

//! over how many buckets entries with tried addresses from a single group (/16
//! for IPv4) are spread
#define ADDRMAN_TRIED_BUCKETS_PER_GROUP 8

//! over how many buckets entries with new addresses originating from a single
//! group are spread
#define ADDRMAN_NEW_BUCKETS_PER_SOURCE_GROUP 64

//! in how many buckets for entries with new addresses a single address may
//! occur
#define ADDRMAN_NEW_BUCKETS_PER_ADDRESS 8

//! how old addresses can maximally be
#define ADDRMAN_HORIZON_DAYS 30

//! after how many failed attempts we give up on a new node
#define ADDRMAN_RETRIES 3

//! how many successive failures are allowed ...
#define ADDRMAN_MAX_FAILURES 10

//! ... in at least this many days
#define ADDRMAN_MIN_FAIL_DAYS 7

//! how recent a successful connection should be before we allow an address to
//! be evicted from tried
#define ADDRMAN_REPLACEMENT_SECONDS (4 * 60 * 60)

//! Convenience
#define ADDRMAN_TRIED_BUCKET_COUNT (1 << ADDRMAN_TRIED_BUCKET_COUNT_LOG2)
#define ADDRMAN_NEW_BUCKET_COUNT (1 << ADDRMAN_NEW_BUCKET_COUNT_LOG2)
#define ADDRMAN_BUCKET_SIZE (1 << ADDRMAN_BUCKET_SIZE_LOG2)

//! the maximum number of tried addr collisions to store
#define ADDRMAN_SET_TRIED_COLLISION_SIZE 10

//! the maximum time we'll spend trying to resolve a tried table collision, in
//! seconds (40 minutes)
static const int64_t ADDRMAN_TEST_WINDOW = 40 * 60;

/**
 * Stochastical (IP) address manager
 */
class CAddrMan {
    friend class CAddrManTest;

protected:
    //! critical section to protect the inner data structures
    mutable RecursiveMutex cs;

private:
    //! first unused nId
    NidType nIdCount GUARDED_BY(cs) {0};

    //! table with information about all nIds
    std::map<NidType, CAddrInfo> mapInfo GUARDED_BY(cs);

    //! find an nId based on its network address
    std::map<CNetAddr, NidType> mapAddr GUARDED_BY(cs);

    //! randomly-ordered vector of all nIds
    std::vector<NidType> vRandom GUARDED_BY(cs);

    // number of "tried" entries
    int nTried GUARDED_BY(cs);

    //! list of "tried" buckets
    NidType vvTried[ADDRMAN_TRIED_BUCKET_COUNT][ADDRMAN_BUCKET_SIZE] GUARDED_BY(cs);

    //! number of (unique) "new" entries
    int nNew GUARDED_BY(cs);

    //! list of "new" buckets
    NidType vvNew[ADDRMAN_NEW_BUCKET_COUNT][ADDRMAN_BUCKET_SIZE] GUARDED_BY(cs);

    //! last time Good was called (memory only)
    int64_t nLastGood GUARDED_BY(cs);

    //! Holds addrs inserted into tried table that collide with existing
    //! entries. Test-before-evict discipline used to resolve these collisions.
    std::set<NidType> m_tried_collisions;

protected:
    //! secret key to randomize bucket select with
    uint256 nKey;

    //! Source of random numbers for randomization in inner loops
    FastRandomContext insecure_rand;

    //! Find an entry.
    CAddrInfo *Find(const CNetAddr &addr, NidType *pnId = nullptr) EXCLUSIVE_LOCKS_REQUIRED(cs);

    //! find an entry, creating it if necessary.
    //! nTime and nServices of the found node are updated, if necessary.
    CAddrInfo *Create(const CAddress &addr, const CNetAddr &addrSource, NidType *pnId = nullptr) EXCLUSIVE_LOCKS_REQUIRED(cs);

    //! Swap two elements in vRandom.
    void SwapRandom(unsigned int nRandomPos1, unsigned int nRandomPos2) EXCLUSIVE_LOCKS_REQUIRED(cs);

    //! Move an entry from the "new" table(s) to the "tried" table
    void MakeTried(CAddrInfo &info, NidType nId) EXCLUSIVE_LOCKS_REQUIRED(cs);

    //! Delete an entry. It must not be in tried, and have refcount 0.
    void Delete(NidType nId) EXCLUSIVE_LOCKS_REQUIRED(cs);

    //! Clear a position in a "new" table. This is the only place where entries
    //! are actually deleted.
    void ClearNew(int nUBucket, int nUBucketPos) EXCLUSIVE_LOCKS_REQUIRED(cs);

    //! Mark an entry "good", possibly moving it from "new" to "tried".
    void Good_(const CService &addr, bool test_before_evict, int64_t time) EXCLUSIVE_LOCKS_REQUIRED(cs);

    //! Add an entry to the "new" table.
    bool Add_(const CAddress &addr, const CNetAddr &source, int64_t nTimePenalty) EXCLUSIVE_LOCKS_REQUIRED(cs);

    //! Mark an entry as attempted to connect.
    void Attempt_(const CService &addr, bool fCountFailure, int64_t nTime) EXCLUSIVE_LOCKS_REQUIRED(cs);

    //! Select an address to connect to, if newOnly is set to true, only the new
    //! table is selected from.
    CAddrInfo Select_(bool newOnly) EXCLUSIVE_LOCKS_REQUIRED(cs);

    //! See if any to-be-evicted tried table entries have been tested and if so
    //! resolve the collisions.
    void ResolveCollisions_() EXCLUSIVE_LOCKS_REQUIRED(cs);

    //! Return a random to-be-evicted tried table address.
    CAddrInfo SelectTriedCollision_() EXCLUSIVE_LOCKS_REQUIRED(cs);

#ifdef DEBUG_ADDRMAN
    //! Perform consistency check. Returns an error code or zero.
    int Check_() EXCLUSIVE_LOCKS_REQUIRED(cs);
#endif

    //! Select several addresses at once.
    void GetAddr_(std::vector<CAddress> &vAddr, size_t max_addresses, size_t max_pct) EXCLUSIVE_LOCKS_REQUIRED(cs);

    //! Mark an entry as currently-connected-to.
    void Connected_(const CService &addr, int64_t nTime) EXCLUSIVE_LOCKS_REQUIRED(cs);

    //! Update an entry's service bits.
    void SetServices_(const CService &addr, ServiceFlags nServices) EXCLUSIVE_LOCKS_REQUIRED(cs);

public:
    //! Serialization versions.
    enum class Format : uint8_t {
        V0_HISTORICAL = 0,    //!< historic format, before commit e6b343d88
        V1_DETERMINISTIC = 1, //!< for pre-asmap files
        V2_ASMAP = 2,         //!< for files including asmap version
        V3_BIP155 = 3,        //!< same as V2_ASMAP plus addresses are in BIP155 format
    };

    // Compressed IP->ASN mapping, loaded from a file when a node starts.
    // Should be always empty if no file was provided.
    // This mapping is then used for bucketing nodes in Addrman.
    //
    // If asmap is provided, nodes will be bucketed by
    // AS they belong to, in order to make impossible for a node
    // to connect to several nodes hosted in a single AS.
    // This is done in response to Erebus attack, but also to generally
    // diversify the connections every node creates,
    // especially useful when a large fraction of nodes
    // operate under a couple of cloud providers.
    //
    // If a new asmap was provided, the existing records
    // would be re-bucketed accordingly.
    std::vector<bool> m_asmap;

    // Read asmap from provided binary file
    static std::vector<bool> DecodeAsmap(fs::path path);

    /**
     * Serialized format.
     * * version byte (@see `Format`)
     * * 0x20 + nKey (serialized as if it were a vector, for backward compatibility)
     * * nNew
     * * nTried
     * * number of "new" buckets XOR 2**30
     * * all nNew addrinfos in vvNew
     * * all nTried addrinfos in vvTried
     * * for each bucket:
     *   * number of elements
     *   * for each element: index
     *
     * 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.
     *
     * Notice that vvTried, mapAddr and vVector are never encoded explicitly;
     * they are instead reconstructed from the other information.
     *
     * vvNew is serialized, but only used if ADDRMAN_UNKNOWN_BUCKET_COUNT didn't
     * change, otherwise it is reconstructed as well.
     *
     * 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.
     */
    template <typename Stream>
    void Serialize(Stream &s_) const {
        LOCK(cs);

        // Always serialize in the latest version (currently Format::V3_BIP155).

        OverrideStream<Stream> s(&s_, s_.GetType(), s_.GetVersion() | ADDRV2_FORMAT);

        s << static_cast<uint8_t>(Format::V3_BIP155);
        s << uint8_t(32);
        s << nKey;
        s << nNew;
        s << nTried;

        int nUBuckets = ADDRMAN_NEW_BUCKET_COUNT ^ (1 << 30);
        s << nUBuckets;
        std::map<NidType, int> mapUnkIds;
        int nIds = 0;
        for (const auto & [nId, info] : mapInfo) {
            mapUnkIds[nId] = nIds;
            if (info.nRefCount) {
                // this means nNew was wrong, oh ow
                assert(nIds != nNew);
                s << info;
                ++nIds;
            }
        }
        nIds = 0;
        for (const auto & [_, info] : mapInfo) {
            if (info.fInTried) {
                // this means nTried was wrong, oh ow
                assert(nIds != nTried);
                s << info;
                ++nIds;
            }
        }
        std::vector<NidType> bucketValidNids;
        bucketValidNids.reserve(ADDRMAN_BUCKET_SIZE);
        for (size_t bucket = 0; bucket < ADDRMAN_NEW_BUCKET_COUNT; ++bucket, bucketValidNids.clear()) {
            int nSize = 0;
            for (size_t i = 0; i < ADDRMAN_BUCKET_SIZE; ++i) {
                if (const NidType & nId = vvNew[bucket][i]; nId.IsValid()) {
                    ++nSize;
                    bucketValidNids.push_back(nId);
                }
            }
            s << nSize;
            for (const auto & nId : bucketValidNids) {
                const int nIndex = mapUnkIds[nId];
                s << nIndex;
            }
        }
        // Store asmap version after bucket entries so that it
        // can be ignored by older clients for backward compatibility.
        uint256 asmap_version;
        if (m_asmap.size() != 0) {
            asmap_version = SerializeHash(m_asmap);
        }
        s << asmap_version;
    }

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

        Clear();

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

        static constexpr Format maximum_supported_format = Format::V3_BIP155;
        if (format > maximum_supported_format) {
            throw std::ios_base::failure(
                strprintf("Unsupported format of addrman database: %u. Maximum supported is %u. "
                          "Continuing operation without using the saved list of peers.",
                          static_cast<uint8_t>(format), static_cast<uint8_t>(maximum_supported_format)));
        }

        int stream_version = s_.GetVersion();
        if (format >= Format::V3_BIP155) {
            // Add ADDRV2_FORMAT to the version so that the CNetAddr and CAddress
            // unserialize methods know that an address in addrv2 format is coming.
            stream_version |= ADDRV2_FORMAT;
        }

        OverrideStream<Stream> s(&s_, s_.GetType(), stream_version);

        uint8_t nKeySize;
        s >> nKeySize;
        if (nKeySize != 32) {
            throw std::ios_base::failure("Incorrect keysize in addrman deserialization");
        }

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

        if (nNew < 0 || nNew > ADDRMAN_NEW_BUCKET_COUNT * ADDRMAN_BUCKET_SIZE) {
            throw std::ios_base::failure("Corrupt CAddrMan serialization, nNew exceeds limit.");
        }

        if (nTried < 0 || nTried > ADDRMAN_TRIED_BUCKET_COUNT * ADDRMAN_BUCKET_SIZE) {
            throw std::ios_base::failure("Corrupt CAddrMan serialization, nTried exceeds limit.");
        }

        // Deserialize entries from the new table.
        for (NidType n{0}; n.Get() < static_cast<int64_t>(nNew); ++n) {
            CAddrInfo &info = mapInfo[n];
            s >> info;
            mapAddr[info] = n;
            info.nRandomPos = vRandom.size();
            vRandom.push_back(n);
        }
        nIdCount.Set(nNew);

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

        // Store positions in the new table buckets to apply later (if possible).
        std::map<NidType, int> entryToBucket; // Represents which entry belonged to which bucket when serializing

        for (int bucket = 0; bucket < nUBuckets; ++bucket) {
            int nSize = 0;
            s >> nSize;
            for (int n = 0; n < nSize; ++n) {
                int nIndex = 0;
                s >> nIndex;
                if (nIndex >= 0 && nIndex < nNew) {
                    entryToBucket[NidType{static_cast<int64_t>(nIndex)}] = bucket;
                }
            }
        }

        uint256 supplied_asmap_version;
        if (m_asmap.size() != 0) {
            supplied_asmap_version = SerializeHash(m_asmap);
        }
        uint256 serialized_asmap_version;
        if (format >= Format::V2_ASMAP) {
            s >> serialized_asmap_version;
        }
        const bool asmap_versions_equal = supplied_asmap_version == serialized_asmap_version;

        for (NidType n{0}; n.Get() < static_cast<int64_t>(nNew); ++n) {
            CAddrInfo &info = mapInfo[n];
            int bucket = entryToBucket[n];
            int nUBucketPos = info.GetBucketPosition(nKey, true, bucket);
            if (format >= Format::V2_ASMAP && nUBuckets == ADDRMAN_NEW_BUCKET_COUNT && ! vvNew[bucket][nUBucketPos].IsValid()
                && info.nRefCount < ADDRMAN_NEW_BUCKETS_PER_ADDRESS && asmap_versions_equal) {
                // Bucketing has not changed, using existing bucket positions for the new table
                vvNew[bucket][nUBucketPos] = n;
                info.nRefCount++;
            } else {
                // In case the new table data cannot be used (format unknown, bucket count wrong or new asmap),
                // try to give them a reference based on their primary source address.
                LogPrint(BCLog::ADDRMAN, "Bucketing method was updated, re-bucketing addrman entries from disk\n");
                bucket = info.GetNewBucket(nKey, m_asmap);
                nUBucketPos = info.GetBucketPosition(nKey, true, bucket);
                if (! vvNew[bucket][nUBucketPos].IsValid()) {
                    vvNew[bucket][nUBucketPos] = n;
                    info.nRefCount++;
                }
            }
        }

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

        Check();
    }

    void Clear() {
        LOCK(cs);
        std::vector<NidType>().swap(vRandom); // done this way to ensure release of vRandom's allocated capacity
        insecure_rand.rand256(nKey);
        for (size_t bucket = 0; bucket < ADDRMAN_NEW_BUCKET_COUNT; ++bucket) {
            for (size_t entry = 0; entry < ADDRMAN_BUCKET_SIZE; ++entry) {
                vvNew[bucket][entry].SetInvalid();
            }
        }
        for (size_t bucket = 0; bucket < ADDRMAN_TRIED_BUCKET_COUNT; ++bucket) {
            for (size_t entry = 0; entry < ADDRMAN_BUCKET_SIZE; ++entry) {
                vvTried[bucket][entry].SetInvalid();
            }
        }

        nIdCount.Set(0);
        nTried = 0;
        nNew = 0;
        // Initially at 1 so that "never" is strictly worse.
        nLastGood = 1;
        mapInfo.clear();
        mapAddr.clear();
    }

    CAddrMan() { Clear(); }

    ~CAddrMan() { nKey.SetNull(); }

    //! Return the number of (unique) addresses in all tables.
    size_t size() const {
        // TODO: Cache this in an atomic to avoid this overhead
        LOCK(cs);
        return vRandom.size();
    }

    //! Consistency check
    void Check() {
#ifdef DEBUG_ADDRMAN
        {
            LOCK(cs);
            int err;
            if ((err = Check_())) {
                LogPrintf("ADDRMAN CONSISTENCY CHECK FAILED!!! err=%i\n", err);
            }
        }
#endif
    }

    //! Add a single address.
    bool Add(const CAddress &addr, const CNetAddr &source,
             int64_t nTimePenalty = 0) {
        LOCK(cs);
        bool fRet = false;
        Check();
        fRet |= Add_(addr, source, nTimePenalty);
        Check();
        if (fRet) {
            LogPrint(BCLog::ADDRMAN, "Added %s from %s: %i tried, %i new\n",
                     addr.ToStringIPPort(), source.ToString(), nTried, nNew);
        }
        return fRet;
    }

    //! Add multiple addresses.
    bool Add(const std::vector<CAddress> &vAddr, const CNetAddr &source,
             int64_t nTimePenalty = 0) {
        LOCK(cs);
        int nAdd = 0;
        Check();
        for (const CAddress &a : vAddr) {
            nAdd += Add_(a, source, nTimePenalty) ? 1 : 0;
        }
        Check();
        if (nAdd) {
            LogPrint(BCLog::ADDRMAN,
                     "Added %i addresses from %s: %i tried, %i new\n", nAdd,
                     source.ToString(), nTried, nNew);
        }
        return nAdd > 0;
    }

    //! Mark an entry as accessible.
    void Good(const CService &addr, bool test_before_evict = true, int64_t nTime = GetAdjustedTime()) {
        LOCK(cs);
        Check();
        Good_(addr, test_before_evict, nTime);
        Check();
    }

    //! Mark an entry as connection attempted to.
    void Attempt(const CService &addr, bool fCountFailure, int64_t nTime = GetAdjustedTime()) {
        LOCK(cs);
        Check();
        Attempt_(addr, fCountFailure, nTime);
        Check();
    }

    //! See if any to-be-evicted tried table entries have been tested and if so
    //! resolve the collisions.
    void ResolveCollisions() {
        LOCK(cs);
        Check();
        ResolveCollisions_();
        Check();
    }

    //! Randomly select an address in tried that another address is attempting
    //! to evict.
    CAddrInfo SelectTriedCollision() {
        CAddrInfo ret;
        {
            LOCK(cs);
            Check();
            ret = SelectTriedCollision_();
            Check();
        }
        return ret;
    }

    /**
     * Choose an address to connect to.
     */
    CAddrInfo Select(bool newOnly = false) {
        CAddrInfo addrRet;
        {
            LOCK(cs);
            Check();
            addrRet = Select_(newOnly);
            Check();
        }
        return addrRet;
    }

    //! Return a bunch of addresses, selected at random.
    std::vector<CAddress> GetAddr(size_t max_addresses, size_t max_pct) {
        Check();
        std::vector<CAddress> vAddr;
        {
            LOCK(cs);
            GetAddr_(vAddr, max_addresses, max_pct);
        }
        Check();
        return vAddr;
    }

    //! Mark an entry as currently-connected-to.
    void Connected(const CService &addr, int64_t nTime = GetAdjustedTime()) {
        LOCK(cs);
        Check();
        Connected_(addr, nTime);
        Check();
    }

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