text: // Copyright (c) 2012 Pieter Wuille
  // Distributed under the MIT/X11 software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #ifndef _CICCOIN_ADDRMAN
  #define _CICCOIN_ADDRMAN 1
  
  #include "netbase.h"
  #include "protocol.h"
  #include "sync.h"
  #include "util.h"
  
  #include <map>
  #include <set>
  #include <stdint.h>
  #include <vector>
  
  #include <openssl/rand.h>
  
  /** Extended statistics about a CAddress */
  class CAddrInfo : public CAddress
  {
  private:
      // where knowledge about this address first came from
      CNetAddr source;
  
      // last successful connection by us
      int64_t nLastSuccess;
  
      // last try whatsoever by us:
      // int64_t CAddress::nLastTry
  
      // 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:
  
      IMPLEMENT_SERIALIZE(
          CAddress* pthis = (CAddress*)(this);
          READWRITE(*pthis);
          READWRITE(source);
          READWRITE(nLastSuccess);
          READWRITE(nAttempts);
      )
  
      void Init()
      {
          nLastSuccess = 0;
          nLastTry = 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 std::vector<unsigned char> &nKey) const;
  
      // Calculate in which "new" bucket this entry belongs, given a certain source
      int GetNewBucket(const std::vector<unsigned char> &nKey, const CNetAddr& src) const;
  
      // Calculate in which "new" bucket this entry belongs, using its default source
      int GetNewBucket(const std::vector<unsigned char> &nKey) const
      {
          return GetNewBucket(nKey, source);
      }
  
      // 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:
  //  * Only keep a limited number of addresses around, so that addr.dat and memory requirements do not grow without bound.
  //  * Keep the address tables in-memory, and asynchronously dump the entire to able in addr.dat.
  //  * Make sure no (localized) attacker can fill the entire table with his nodes/addresses.
  //
  // To that end:
  //  * Addresses are organized into buckets.
  //    * Address that have not yet been tried go into 256 "new" buckets.
  //      * Based on the address range (/16 for IPv4) of source of the information, 32 buckets are selected at random
  //      * The actual bucket is chosen from one of these, based on the range the address itself is located.
  //      * One single address can occur in up to 4 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 64 "tried" buckets.
  //      * Each address range selects at random 4 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-CIC 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 64
  
  // maximum allowed number of entries in buckets for tried addresses
  #define ADDRMAN_TRIED_BUCKET_SIZE 64
  
  // total number of buckets for new addresses
  #define ADDRMAN_NEW_BUCKET_COUNT 256
  
  // maximum allowed number of entries in buckets for new addresses
  #define ADDRMAN_NEW_BUCKET_SIZE 64
  
  // over how many buckets entries with tried addresses from a single group (/16 for IPv4) are spread
  #define ADDRMAN_TRIED_BUCKETS_PER_GROUP 4
  
  // over how many buckets entries with new addresses originating from a single group are spread
  #define ADDRMAN_NEW_BUCKETS_PER_SOURCE_GROUP 32
  
  // in how many buckets for entries with new addresses a single address may occur
  #define ADDRMAN_NEW_BUCKETS_PER_ADDRESS 4
  
  // how many entries in a bucket with tried addresses are inspected, when selecting one to replace
  #define ADDRMAN_TRIED_ENTRIES_INSPECT_ON_EVICT 4
  
  // 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
  
  /** Stochastical (IP) address manager */
  class CAddrMan
  {
  private:
      // critical section to protect the inner data structures
      mutable CCriticalSection cs;
  
      // secret key to randomize bucket select with
      std::vector<unsigned char> nKey;
  
      // 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
      std::vector<std::vector<int> > vvTried;
  
      // number of (unique) "new" entries
      int nNew;
  
      // list of "new" buckets
      std::vector<std::set<int> > vvNew;
  
  protected:
  
      // Find an entry.
      CAddrInfo* Find(const CNetAddr& addr, int *pnId = NULL);
  
      // find an entry, creating it if necessary.
      // nTime and nServices of found node is updated, if necessary.
      CAddrInfo* Create(const CAddress &addr, const CNetAddr &addrSource, int *pnId = NULL);
  
      // Swap two elements in vRandom.
      void SwapRandom(unsigned int nRandomPos1, unsigned int nRandomPos2);
  
      // Return position in given bucket to replace.
      int SelectTried(int nKBucket);
  
      // Remove an element from a "new" bucket.
      // This is the only place where actual deletes occur.
      // They are never deleted while in the "tried" table, only possibly evicted back to the "new" table.
      int ShrinkNew(int nUBucket);
  
      // Move an entry from the "new" table(s) to the "tried" table
      // @pre vvUnkown[nOrigin].count(nId) != 0
      void MakeTried(CAddrInfo& info, int nId, int nOrigin);
  
      // 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, int64_t nTime);
  
      // Select an address to connect to.
      // nUnkBias determines how much to favor new addresses over tried ones (min=0, max=100)
      CAddress Select_(int nUnkBias);
  
  #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);
  
  public:
  
      IMPLEMENT_SERIALIZE
      (({
          // serialized format:
          // * version byte (currently 0)
          // * nKey
          // * nNew
          // * nTried
          // * number of "new" buckets
          // * all nNew addrinfos in vvNew
          // * all nTried addrinfos in vvTried
          // * for each bucket:
          //   * number of elements
          //   * for each element: index
          //
          // 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_UNKOWN_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.
          {
              LOCK(cs);
              unsigned char nVersion = 0;
              READWRITE(nVersion);
              READWRITE(nKey);
              READWRITE(nNew);
              READWRITE(nTried);
  
              CAddrMan *am = const_cast<CAddrMan*>(this);
              if (fWrite)
              {
                  int nUBuckets = ADDRMAN_NEW_BUCKET_COUNT;
                  READWRITE(nUBuckets);
                  std::map<int, int> mapUnkIds;
                  int nIds = 0;
                  for (std::map<int, CAddrInfo>::iterator it = am->mapInfo.begin(); it != am->mapInfo.end(); it++)
                  {
                      if (nIds == nNew) break; // this means nNew was wrong, oh ow
                      mapUnkIds[(*it).first] = nIds;
                      CAddrInfo &info = (*it).second;
                      if (info.nRefCount)
                      {
                          READWRITE(info);
                          nIds++;
                      }
                  }
                  nIds = 0;
                  for (std::map<int, CAddrInfo>::iterator it = am->mapInfo.begin(); it != am->mapInfo.end(); it++)
                  {
                      if (nIds == nTried) break; // this means nTried was wrong, oh ow
                      CAddrInfo &info = (*it).second;
                      if (info.fInTried)
                      {
                          READWRITE(info);
                          nIds++;
                      }
                  }
                  for (std::vector<std::set<int> >::iterator it = am->vvNew.begin(); it != am->vvNew.end(); it++)
                  {
                      const std::set<int> &vNew = (*it);
                      int nSize = vNew.size();
                      READWRITE(nSize);
                      for (std::set<int>::iterator it2 = vNew.begin(); it2 != vNew.end(); it2++)
                      {
                          int nIndex = mapUnkIds[*it2];
                          READWRITE(nIndex);
                      }
                  }
              } else {
                  int nUBuckets = 0;
                  READWRITE(nUBuckets);
                  am->nIdCount = 0;
                  am->mapInfo.clear();
                  am->mapAddr.clear();
                  am->vRandom.clear();
                  am->vvTried = std::vector<std::vector<int> >(ADDRMAN_TRIED_BUCKET_COUNT, std::vector<int>(0));
                  am->vvNew = std::vector<std::set<int> >(ADDRMAN_NEW_BUCKET_COUNT, std::set<int>());
                  for (int n = 0; n < am->nNew; n++)
                  {
                      CAddrInfo &info = am->mapInfo[n];
                      READWRITE(info);
                      am->mapAddr[info] = n;
                      info.nRandomPos = vRandom.size();
                      am->vRandom.push_back(n);
                      if (nUBuckets != ADDRMAN_NEW_BUCKET_COUNT)
                      {
                          am->vvNew[info.GetNewBucket(am->nKey)].insert(n);
                          info.nRefCount++;
                      }
                  }
                  am->nIdCount = am->nNew;
                  int nLost = 0;
                  for (int n = 0; n < am->nTried; n++)
                  {
                      CAddrInfo info;
                      READWRITE(info);
                      std::vector<int> &vTried = am->vvTried[info.GetTriedBucket(am->nKey)];
                      if (vTried.size() < ADDRMAN_TRIED_BUCKET_SIZE)
                      {
                          info.nRandomPos = vRandom.size();
                          info.fInTried = true;
                          am->vRandom.push_back(am->nIdCount);
                          am->mapInfo[am->nIdCount] = info;
                          am->mapAddr[info] = am->nIdCount;
                          vTried.push_back(am->nIdCount);
                          am->nIdCount++;
                      } else {
                          nLost++;
                      }
                  }
                  am->nTried -= nLost;
                  for (int b = 0; b < nUBuckets; b++)
                  {
                      std::set<int> &vNew = am->vvNew[b];
                      int nSize = 0;
                      READWRITE(nSize);
                      for (int n = 0; n < nSize; n++)
                      {
                          int nIndex = 0;
                          READWRITE(nIndex);
                          CAddrInfo &info = am->mapInfo[nIndex];
                          if (nUBuckets == ADDRMAN_NEW_BUCKET_COUNT && info.nRefCount < ADDRMAN_NEW_BUCKETS_PER_ADDRESS)
                          {
                              info.nRefCount++;
                              vNew.insert(nIndex);
                          }
                      }
                  }
              }
          }
      });)
  
      CAddrMan() : vRandom(0), vvTried(ADDRMAN_TRIED_BUCKET_COUNT, std::vector<int>(0)), vvNew(ADDRMAN_NEW_BUCKET_COUNT, std::set<int>())
      {
           nKey.resize(32);
           RAND_bytes(&nKey[0], 32);
  
           nIdCount = 0;
           nTried = 0;
           nNew = 0;
      }
  
      // Return the number of (unique) addresses in all tables.
      int size()
      {
          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)
      {
          bool fRet = false;
          {
              LOCK(cs);
              Check();
              fRet |= Add_(addr, source, nTimePenalty);
              Check();
          }
          if (fRet)
              LogPrint("addrman", "Added %s from %s: %i tried, %i new\n", addr.ToStringIPPort().c_str(), source.ToString().c_str(), nTried, nNew);
          return fRet;
      }
  
      // Add multiple addresses.
      bool Add(const std::vector<CAddress> &vAddr, const CNetAddr& source, int64_t nTimePenalty = 0)
      {
          int nAdd = 0;
          {
              LOCK(cs);
              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("addrman", "Added %i addresses from %s: %i tried, %i new\n", nAdd, source.ToString().c_str(), 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, int64_t nTime = GetAdjustedTime())
      {
          {
              LOCK(cs);
              Check();
              Attempt_(addr, nTime);
              Check();
          }
      }
  
      // Choose an address to connect to.
      // nUnkBias determines how much "new" entries are favored over "tried" ones (0-100).
      CAddress Select(int nUnkBias = 50)
      {
          CAddress addrRet;
          {
              LOCK(cs);
              Check();
              addrRet = Select_(nUnkBias);
              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();
          }
      }
  };
  
  #endif
  