text: // Copyright (c) 2012 Pieter Wuille
  // Copyright (c) 2012-2017 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 HUNTCOIN_ADDRMAN_H
  #define HUNTCOIN_ADDRMAN_H
  
  #include <netaddress.h>
  #include <protocol.h>
  #include <random.h>
  #include <sync.h>
  #include <timedata.h>
  #include <util.h>
  
  #include <map>
  #include <set>
  #include <stdint.h>
  #include <vector>
  
  /**
   * Extended statistics about a CAddress
   */
  class CAddrInfo : public CAddress
  {
  
  
  public:
      //! last try whatsoever by us (memory only)
      int64_t nLastTry;
  
      //! last counted attempt (memory only)
      int64_t nLastCountAttempt;
  
  private:
      //! where knowledge about this address first came from
      CNetAddr source;
  
      //! last successful connection by us
      int64_t nLastSuccess;
  
      //! connection attempts since last successful attempt
      int nAttempts;
  
      //! reference count in new sets (memory only)
      int nRefCount;
  
      //! in tried set? (memory only)
      bool fInTried;
  
      //! position in vRandom
      int nRandomPos;
  
      friend class CAddrMan;
  
  public:
  
      ADD_SERIALIZE_METHODS;
  
      template <typename Stream, typename Operation>
      inline void SerializationOp(Stream& s, Operation ser_action) {
          READWRITE(*static_cast<CAddress*>(this));
          READWRITE(source);
          READWRITE(nLastSuccess);
          READWRITE(nAttempts);
      }
  
      void Init()
      {
          nLastSuccess = 0;
          nLastTry = 0;
          nLastCountAttempt = 0;
          nAttempts = 0;
          nRefCount = 0;
          fInTried = false;
          nRandomPos = -1;
      }
  
      CAddrInfo(const CAddress &addrIn, const CNetAddr &addrSource) : CAddress(addrIn), source(addrSource)
      {
          Init();
      }
  
      CAddrInfo() : CAddress(), source()
      {
          Init();
      }
  
      //! Calculate in which "tried" bucket this entry belongs
      int GetTriedBucket(const uint256 &nKey) const;
  
      //! Calculate in which "new" bucket this entry belongs, given a certain source
      int GetNewBucket(const uint256 &nKey, const CNetAddr& src) const;
  
      //! Calculate in which "new" bucket this entry belongs, using its default source
      int GetNewBucket(const uint256 &nKey) const
      {
          return GetNewBucket(nKey, source);
      }
  
      //! 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
  
  //! the maximum percentage of nodes to return in a getaddr call
  #define ADDRMAN_GETADDR_MAX_PCT 23
  
  //! the maximum number of nodes to return in a getaddr call
  #define ADDRMAN_GETADDR_MAX 2500
  
  //! 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)
  
  /** 
   * Stochastical (IP) address manager 
   */
  class CAddrMan
  {
  private:
      //! critical section to protect the inner data structures
      mutable CCriticalSection cs;
  
      //! last used nId
      int nIdCount;
  
      //! table with information about all nIds
      std::map<int, CAddrInfo> mapInfo;
  
      //! find an nId based on its network address
      std::map<CNetAddr, int> mapAddr;
  
      //! randomly-ordered vector of all nIds
      std::vector<int> vRandom;
  
      // number of "tried" entries
      int nTried;
  
      //! list of "tried" buckets
      int vvTried[ADDRMAN_TRIED_BUCKET_COUNT][ADDRMAN_BUCKET_SIZE];
  
      //! number of (unique) "new" entries
      int nNew;
  
      //! list of "new" buckets
      int vvNew[ADDRMAN_NEW_BUCKET_COUNT][ADDRMAN_BUCKET_SIZE];
  
      //! last time Good was called (memory only)
      int64_t nLastGood;
      
      // discriminate entries based on port. Should be false on mainnet/testnet and can be true on devnet/regtest
      bool discriminatePorts;
  
  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, int *pnId = nullptr);
  
      //! 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, int *pnId = nullptr);
  
      //! Swap two elements in vRandom.
      void SwapRandom(unsigned int nRandomPos1, unsigned int nRandomPos2);
  
      //! Move an entry from the "new" table(s) to the "tried" table
      void MakeTried(CAddrInfo& info, int nId);
  
      //! Delete an entry. It must not be in tried, and have refcount 0.
      void Delete(int nId);
  
      //! Clear a position in a "new" table. This is the only place where entries are actually deleted.
      void ClearNew(int nUBucket, int nUBucketPos);
  
      //! Mark an entry "good", possibly moving it from "new" to "tried".
      void Good_(const CService &addr, int64_t nTime);
  
      //! Add an entry to the "new" table.
      bool Add_(const CAddress &addr, const CNetAddr& source, int64_t nTimePenalty);
  
      //! Mark an entry as attempted to connect.
      void Attempt_(const CService &addr, bool fCountFailure, int64_t nTime);
  
      //! Select an address to connect to, if newOnly is set to true, only the new table is selected from.
      CAddrInfo Select_(bool newOnly);
  
      //! Wraps GetRandInt to allow tests to override RandomInt and make it determinismistic.
      virtual int RandomInt(int nMax);
  
  #ifdef DEBUG_ADDRMAN
      //! Perform consistency check. Returns an error code or zero.
      int Check_();
  #endif
  
      //! Select several addresses at once.
      void GetAddr_(std::vector<CAddress> &vAddr);
  
      //! Mark an entry as currently-connected-to.
      void Connected_(const CService &addr, int64_t nTime);
  
      //! Update an entry's service bits.
      void SetServices_(const CService &addr, ServiceFlags nServices);
  
  public:
      /**
       * serialized format:
       * * version byte (currently 1)
       * * 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 ADD_SERIALIZE_METHODS since the serialization and deserialization code has
       * very little in common.
       */
      template<typename Stream>
      void Serialize(Stream &s) const
      {
          LOCK(cs);
  
          unsigned char nVersion = 1;
          s << nVersion;
          s << ((unsigned char)32);
          s << nKey;
          s << nNew;
          s << nTried;
  
          int nUBuckets = ADDRMAN_NEW_BUCKET_COUNT ^ (1 << 30);
          s << nUBuckets;
          std::map<int, int> mapUnkIds;
          int nIds = 0;
          for (const auto& entry : mapInfo) {
              mapUnkIds[entry.first] = nIds;
              const CAddrInfo &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 CAddrInfo &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;
                  }
              }
          }
      }
  
      template<typename Stream>
      void Unserialize(Stream& s)
      {
          LOCK(cs);
  
          Clear();
  
          unsigned char nVersion;
          s >> nVersion;
          unsigned char 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 (nVersion != 0) {
              nUBuckets ^= (1 << 30);
          }
  
          if (nNew > ADDRMAN_NEW_BUCKET_COUNT * ADDRMAN_BUCKET_SIZE) {
              throw std::ios_base::failure("Corrupt CAddrMan serialization, nNew exceeds limit.");
          }
  
          if (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 (int n = 0; n < nNew; n++) {
              CAddrInfo &info = mapInfo[n];
              s >> info;
              mapAddr[info] = n;
              info.nRandomPos = vRandom.size();
              vRandom.push_back(n);
              if (nVersion != 1 || nUBuckets != ADDRMAN_NEW_BUCKET_COUNT) {
                  // In case the new table data cannot be used (nVersion unknown, or bucket count wrong),
                  // immediately try to give them a reference based on their primary source address.
                  int nUBucket = info.GetNewBucket(nKey);
                  int nUBucketPos = info.GetBucketPosition(nKey, true, nUBucket);
                  if (vvNew[nUBucket][nUBucketPos] == -1) {
                      vvNew[nUBucket][nUBucketPos] = n;
                      info.nRefCount++;
                  }
              }
          }
          nIdCount = 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);
              int nKBucketPos = info.GetBucketPosition(nKey, false, nKBucket);
              if (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++;
              } else {
                  nLost++;
              }
          }
          nTried -= nLost;
  
          // Deserialize positions in the new table (if possible).
          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) {
                      CAddrInfo &info = mapInfo[nIndex];
                      int nUBucketPos = info.GetBucketPosition(nKey, true, bucket);
                      if (nVersion == 1 && nUBuckets == ADDRMAN_NEW_BUCKET_COUNT && vvNew[bucket][nUBucketPos] == -1 && info.nRefCount < ADDRMAN_NEW_BUCKETS_PER_ADDRESS) {
                          info.nRefCount++;
                          vvNew[bucket][nUBucketPos] = nIndex;
                      }
                  }
              }
          }
  
          // Prune new entries with refcount 0 (as a result of collisions).
          int nLostUnk = 0;
          for (std::map<int, CAddrInfo>::const_iterator it = mapInfo.begin(); it != mapInfo.end(); ) {
              if (it->second.fInTried == false && it->second.nRefCount == 0) {
                  std::map<int, CAddrInfo>::const_iterator itCopy = it++;
                  Delete(itCopy->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<int>().swap(vRandom);
          nKey = GetRandHash();
          for (size_t bucket = 0; bucket < ADDRMAN_NEW_BUCKET_COUNT; bucket++) {
              for (size_t entry = 0; entry < ADDRMAN_BUCKET_SIZE; entry++) {
                  vvNew[bucket][entry] = -1;
              }
          }
          for (size_t bucket = 0; bucket < ADDRMAN_TRIED_BUCKET_COUNT; bucket++) {
              for (size_t entry = 0; entry < ADDRMAN_BUCKET_SIZE; entry++) {
                  vvTried[bucket][entry] = -1;
              }
          }
  
          nIdCount = 0;
          nTried = 0;
          nNew = 0;
          nLastGood = 1; //Initially at 1 so that "never" is strictly worse.
          mapInfo.clear();
          mapAddr.clear();
      }
  
      CAddrMan(bool _discriminatePorts = false) :
          discriminatePorts(_discriminatePorts)
      {
          Clear();
      }
  
      ~CAddrMan()
      {
          nKey.SetNull();
      }
  
      //! Return the number of (unique) addresses in all tables.
      size_t size() const
      {
          LOCK(cs); // TODO: Cache this in an atomic to avoid this overhead
          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 (std::vector<CAddress>::const_iterator it = vAddr.begin(); it != vAddr.end(); it++)
              nAdd += Add_(*it, 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, int64_t nTime = GetAdjustedTime())
      {
          LOCK(cs);
          Check();
          Good_(addr, 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();
      }
  
      /**
       * 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()
      {
          Check();
          std::vector<CAddress> vAddr;
          {
              LOCK(cs);
              GetAddr_(vAddr);
          }
          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();
      }
  
  };
  
  #endif // HUNTCOIN_ADDRMAN_H
  