text: // Copyright (c) 2012 Pieter Wuille
  // Copyright (c) 2012-2015 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 "addrman.h"
  
  #include "hash.h"
  #include "serialize.h"
  
  int CAddrInfo::GetTriedBucket(const uint256& nKey) const
  {
      uint64_t hash1 = (CHashWriter(SER_GETHASH, 0) << nKey << GetKey()).GetHash().GetCheapHash();
      uint64_t hash2 = (CHashWriter(SER_GETHASH, 0) << nKey << GetGroup() << (hash1 % ADDRMAN_TRIED_BUCKETS_PER_GROUP)).GetHash().GetCheapHash();
      return hash2 % ADDRMAN_TRIED_BUCKET_COUNT;
  }
  
  int CAddrInfo::GetNewBucket(const uint256& nKey, const CNetAddr& src) const
  {
      std::vector<unsigned char> vchSourceGroupKey = src.GetGroup();
      uint64_t hash1 = (CHashWriter(SER_GETHASH, 0) << nKey << GetGroup() << vchSourceGroupKey).GetHash().GetCheapHash();
      uint64_t hash2 = (CHashWriter(SER_GETHASH, 0) << nKey << vchSourceGroupKey << (hash1 % ADDRMAN_NEW_BUCKETS_PER_SOURCE_GROUP)).GetHash().GetCheapHash();
      return hash2 % ADDRMAN_NEW_BUCKET_COUNT;
  }
  
  int CAddrInfo::GetBucketPosition(const uint256 &nKey, bool fNew, int nBucket) const
  {
      uint64_t hash1 = (CHashWriter(SER_GETHASH, 0) << nKey << (fNew ? 'N' : 'K') << nBucket << GetKey()).GetHash().GetCheapHash();
      return hash1 % ADDRMAN_BUCKET_SIZE;
  }
  
  bool CAddrInfo::IsTerrible(int64_t nNow) const
  {
      if (nLastTry && nLastTry >= nNow - 60) // never remove things tried in the last minute
          return false;
  
      if (nTime > nNow + 10 * 60) // came in a flying DeLorean
          return true;
  
      if (nTime == 0 || nNow - nTime > ADDRMAN_HORIZON_DAYS * 24 * 60 * 60) // not seen in recent history
          return true;
  
      if (nLastSuccess == 0 && nAttempts >= ADDRMAN_RETRIES) // tried N times and never a success
          return true;
  
      if (nNow - nLastSuccess > ADDRMAN_MIN_FAIL_DAYS * 24 * 60 * 60 && nAttempts >= ADDRMAN_MAX_FAILURES) // N successive failures in the last week
          return true;
  
      return false;
  }
  
  double CAddrInfo::GetChance(int64_t nNow) const
  {
      double fChance = 1.0;
  
      int64_t nSinceLastSeen = nNow - nTime;
      int64_t nSinceLastTry = nNow - nLastTry;
  
      if (nSinceLastSeen < 0)
          nSinceLastSeen = 0;
      if (nSinceLastTry < 0)
          nSinceLastTry = 0;
  
      // deprioritize very recent attempts away
      if (nSinceLastTry < 60 * 10)
          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;
  }
  
  CAddrInfo* CAddrMan::Find(const CNetAddr& addr, int* pnId)
  {
      std::map<CNetAddr, int>::iterator it = mapAddr.find(addr);
      if (it == mapAddr.end())
          return NULL;
      if (pnId)
          *pnId = (*it).second;
      std::map<int, CAddrInfo>::iterator it2 = mapInfo.find((*it).second);
      if (it2 != mapInfo.end())
          return &(*it2).second;
      return NULL;
  }
  
  CAddrInfo* CAddrMan::Create(const CAddress& addr, const CNetAddr& addrSource, int* pnId)
  {
      int nId = nIdCount++;
      mapInfo[nId] = CAddrInfo(addr, addrSource);
      mapAddr[addr] = nId;
      mapInfo[nId].nRandomPos = vRandom.size();
      vRandom.push_back(nId);
      if (pnId)
          *pnId = nId;
      return &mapInfo[nId];
  }
  
  void CAddrMan::SwapRandom(unsigned int nRndPos1, unsigned int nRndPos2)
  {
      if (nRndPos1 == nRndPos2)
          return;
  
      assert(nRndPos1 < vRandom.size() && nRndPos2 < vRandom.size());
  
      int nId1 = vRandom[nRndPos1];
      int nId2 = vRandom[nRndPos2];
  
      assert(mapInfo.count(nId1) == 1);
      assert(mapInfo.count(nId2) == 1);
  
      mapInfo[nId1].nRandomPos = nRndPos2;
      mapInfo[nId2].nRandomPos = nRndPos1;
  
      vRandom[nRndPos1] = nId2;
      vRandom[nRndPos2] = nId1;
  }
  
  void CAddrMan::Delete(int nId)
  {
      assert(mapInfo.count(nId) != 0);
      CAddrInfo& info = mapInfo[nId];
      assert(!info.fInTried);
      assert(info.nRefCount == 0);
  
      SwapRandom(info.nRandomPos, vRandom.size() - 1);
      vRandom.pop_back();
      mapAddr.erase(info);
      mapInfo.erase(nId);
      nNew--;
  }
  
  void CAddrMan::ClearNew(int nUBucket, int nUBucketPos)
  {
      // if there is an entry in the specified bucket, delete it.
      if (vvNew[nUBucket][nUBucketPos] != -1) {
          int nIdDelete = vvNew[nUBucket][nUBucketPos];
          CAddrInfo& infoDelete = mapInfo[nIdDelete];
          assert(infoDelete.nRefCount > 0);
          infoDelete.nRefCount--;
          vvNew[nUBucket][nUBucketPos] = -1;
          if (infoDelete.nRefCount == 0) {
              Delete(nIdDelete);
          }
      }
  }
  
  void CAddrMan::MakeTried(CAddrInfo& info, int nId)
  {
      // remove the entry from all new buckets
      for (int bucket = 0; bucket < ADDRMAN_NEW_BUCKET_COUNT; bucket++) {
          int pos = info.GetBucketPosition(nKey, true, bucket);
          if (vvNew[bucket][pos] == nId) {
              vvNew[bucket][pos] = -1;
              info.nRefCount--;
          }
      }
      nNew--;
  
      assert(info.nRefCount == 0);
  
      // which tried bucket to move the entry to
      int nKBucket = info.GetTriedBucket(nKey);
      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
          int nIdEvict = vvTried[nKBucket][nKBucketPos];
          assert(mapInfo.count(nIdEvict) == 1);
          CAddrInfo& infoOld = mapInfo[nIdEvict];
  
          // Remove the to-be-evicted item from the tried set.
          infoOld.fInTried = false;
          vvTried[nKBucket][nKBucketPos] = -1;
          nTried--;
  
          // find which new bucket it belongs to
          int nUBucket = infoOld.GetNewBucket(nKey);
          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++;
      }
      assert(vvTried[nKBucket][nKBucketPos] == -1);
  
      vvTried[nKBucket][nKBucketPos] = nId;
      nTried++;
      info.fInTried = true;
  }
  
  void CAddrMan::Good_(const CService& addr, int64_t nTime)
  {
      int nId;
      CAddrInfo* pinfo = Find(addr, &nId);
  
      // if not found, bail out
      if (!pinfo)
          return;
  
      CAddrInfo& info = *pinfo;
  
      // check whether we are talking about the exact same CService (including same port)
      if (info != addr)
          return;
  
      // update info
      info.nLastSuccess = nTime;
      info.nLastTry = nTime;
      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;
  
      // find a bucket it is in now
      int nRnd = RandomInt(ADDRMAN_NEW_BUCKET_COUNT);
      int nUBucket = -1;
      for (unsigned int n = 0; n < ADDRMAN_NEW_BUCKET_COUNT; n++) {
          int nB = (n + nRnd) % ADDRMAN_NEW_BUCKET_COUNT;
          int nBpos = info.GetBucketPosition(nKey, true, nB);
          if (vvNew[nB][nBpos] == nId) {
              nUBucket = nB;
              break;
          }
      }
  
      // if no bucket is found, something bad happened;
      // TODO: maybe re-add the node, but for now, just bail out
      if (nUBucket == -1)
          return;
  
      LogPrint("addrman", "Moving %s to tried\n", addr.ToString());
  
      // move nId to the tried tables
      MakeTried(info, nId);
  }
  
  bool CAddrMan::Add_(const CAddress& addr, const CNetAddr& source, int64_t nTimePenalty)
  {
      if (!addr.IsRoutable())
          return false;
  
      bool fNew = false;
      int nId;
      CAddrInfo* pinfo = Find(addr, &nId);
  
      if (pinfo) {
          // periodically update nTime
          bool fCurrentlyOnline = (GetAdjustedTime() - addr.nTime < 24 * 60 * 60);
          int64_t nUpdateInterval = (fCurrentlyOnline ? 60 * 60 : 24 * 60 * 60);
          if (addr.nTime && (!pinfo->nTime || pinfo->nTime < addr.nTime - nUpdateInterval - nTimePenalty))
              pinfo->nTime = std::max((int64_t)0, addr.nTime - nTimePenalty);
  
          // add services
          pinfo->nServices |= addr.nServices;
  
          // do not update if no new information is present
          if (!addr.nTime || (pinfo->nTime && 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
          int nFactor = 1;
          for (int n = 0; n < pinfo->nRefCount; n++)
              nFactor *= 2;
          if (nFactor > 1 && (RandomInt(nFactor) != 0))
              return false;
      } else {
          pinfo = Create(addr, source, &nId);
          pinfo->nTime = std::max((int64_t)0, (int64_t)pinfo->nTime - nTimePenalty);
          nNew++;
          fNew = true;
      }
  
      int nUBucket = pinfo->GetNewBucket(nKey, source);
      int nUBucketPos = pinfo->GetBucketPosition(nKey, true, nUBucket);
      if (vvNew[nUBucket][nUBucketPos] != nId) {
          bool fInsert = vvNew[nUBucket][nUBucketPos] == -1;
          if (!fInsert) {
              CAddrInfo& 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;
          } else {
              if (pinfo->nRefCount == 0) {
                  Delete(nId);
              }
          }
      }
      return fNew;
  }
  
  void CAddrMan::Attempt_(const CService& addr, int64_t nTime)
  {
      CAddrInfo* pinfo = Find(addr);
  
      // if not found, bail out
      if (!pinfo)
          return;
  
      CAddrInfo& info = *pinfo;
  
      // check whether we are talking about the exact same CService (including same port)
      if (info != addr)
          return;
  
      // update info
      info.nLastTry = nTime;
      info.nAttempts++;
  }
  
  CAddrInfo CAddrMan::Select_(bool newOnly)
  {
      if (size() == 0)
          return CAddrInfo();
  
      if (newOnly && nNew == 0)
          return CAddrInfo();
  
      // Use a 50% chance for choosing between tried and new table entries.
      if (!newOnly &&
         (nTried > 0 && (nNew == 0 || RandomInt(2) == 0))) { 
          // use a tried node
          double fChanceFactor = 1.0;
          while (1) {
              int nKBucket = RandomInt(ADDRMAN_TRIED_BUCKET_COUNT);
              int nKBucketPos = RandomInt(ADDRMAN_BUCKET_SIZE);
              while (vvTried[nKBucket][nKBucketPos] == -1) {
                  nKBucket = (nKBucket + insecure_rand.rand32()) % ADDRMAN_TRIED_BUCKET_COUNT;
                  nKBucketPos = (nKBucketPos + insecure_rand.rand32()) % ADDRMAN_BUCKET_SIZE;
              }
              int nId = vvTried[nKBucket][nKBucketPos];
              assert(mapInfo.count(nId) == 1);
              CAddrInfo& info = mapInfo[nId];
              if (RandomInt(1 << 30) < fChanceFactor * info.GetChance() * (1 << 30))
                  return info;
              fChanceFactor *= 1.2;
          }
      } else {
          // use a new node
          double fChanceFactor = 1.0;
          while (1) {
              int nUBucket = RandomInt(ADDRMAN_NEW_BUCKET_COUNT);
              int nUBucketPos = RandomInt(ADDRMAN_BUCKET_SIZE);
              while (vvNew[nUBucket][nUBucketPos] == -1) {
                  nUBucket = (nUBucket + insecure_rand.rand32()) % ADDRMAN_NEW_BUCKET_COUNT;
                  nUBucketPos = (nUBucketPos + insecure_rand.rand32()) % ADDRMAN_BUCKET_SIZE;
              }
              int nId = vvNew[nUBucket][nUBucketPos];
              assert(mapInfo.count(nId) == 1);
              CAddrInfo& info = mapInfo[nId];
              if (RandomInt(1 << 30) < fChanceFactor * info.GetChance() * (1 << 30))
                  return info;
              fChanceFactor *= 1.2;
          }
      }
  }
  
  #ifdef DEBUG_ADDRMAN
  int CAddrMan::Check_()
  {
      std::set<int> setTried;
      std::map<int, int> mapNew;
  
      if (vRandom.size() != nTried + nNew)
          return -7;
  
      for (std::map<int, CAddrInfo>::iterator it = mapInfo.begin(); it != mapInfo.end(); it++) {
          int n = (*it).first;
          CAddrInfo& info = (*it).second;
          if (info.fInTried) {
              if (!info.nLastSuccess)
                  return -1;
              if (info.nRefCount)
                  return -2;
              setTried.insert(n);
          } else {
              if (info.nRefCount < 0 || info.nRefCount > ADDRMAN_NEW_BUCKETS_PER_ADDRESS)
                  return -3;
              if (!info.nRefCount)
                  return -4;
              mapNew[n] = info.nRefCount;
          }
          if (mapAddr[info] != n)
              return -5;
          if (info.nRandomPos < 0 || info.nRandomPos >= vRandom.size() || vRandom[info.nRandomPos] != n)
              return -14;
          if (info.nLastTry < 0)
              return -6;
          if (info.nLastSuccess < 0)
              return -8;
      }
  
      if (setTried.size() != nTried)
          return -9;
      if (mapNew.size() != 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.count(vvTried[n][i]))
                       return -11;
                   if (mapInfo[vvTried[n][i]].GetTriedBucket(nKey) != n)
                       return -17;
                   if (mapInfo[vvTried[n][i]].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.count(vvNew[n][i]))
                      return -12;
                  if (mapInfo[vvNew[n][i]].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;
  
      return 0;
  }
  #endif
  
  void CAddrMan::GetAddr_(std::vector<CAddress>& vAddr)
  {
      unsigned int nNodes = ADDRMAN_GETADDR_MAX_PCT * vRandom.size() / 100;
      if (nNodes > ADDRMAN_GETADDR_MAX)
          nNodes = ADDRMAN_GETADDR_MAX;
  
      // gather a list of random nodes, skipping those of low quality
      for (unsigned int n = 0; n < vRandom.size(); n++) {
          if (vAddr.size() >= nNodes)
              break;
  
          int nRndPos = RandomInt(vRandom.size() - n) + n;
          SwapRandom(n, nRndPos);
          assert(mapInfo.count(vRandom[n]) == 1);
  
          const CAddrInfo& ai = mapInfo[vRandom[n]];
          if (!ai.IsTerrible())
              vAddr.push_back(ai);
      }
  }
  
  void CAddrMan::Connected_(const CService& addr, int64_t nTime)
  {
      CAddrInfo* pinfo = Find(addr);
  
      // if not found, bail out
      if (!pinfo)
          return;
  
      CAddrInfo& info = *pinfo;
  
      // check whether we are talking about the exact same CService (including same port)
      if (info != addr)
          return;
  
      // update info
      int64_t nUpdateInterval = 20 * 60;
      if (nTime - info.nTime > nUpdateInterval)
          info.nTime = nTime;
  }
  
  int CAddrMan::RandomInt(int nMax){
      return GetRandInt(nMax);
  }
  