Merge branch 'addrman' of https://github.com/sipa/bitcoin

17 files changed, 1181 insertions, 250 deletions

diff --git a/bitcoin-qt.pro b/bitcoin-qt.pro
index 18d30c8dcb..e040dadf6f 100644
--- a/bitcoin-qt.pro
+++ b/bitcoin-qt.pro
@@ -101,6 +101,7 @@ HEADERS += src/qt/bitcoingui.h \
     src/qt/aboutdialog.h \
     src/qt/editaddressdialog.h \
     src/qt/bitcoinaddressvalidator.h \
+    src/addrman.h \
     src/base58.h \
     src/bignum.h \
     src/checkpoints.h \
@@ -175,6 +176,7 @@ SOURCES += src/qt/bitcoin.cpp src/qt/bitcoingui.cpp \
     src/net.cpp \
     src/irc.cpp \
     src/checkpoints.cpp \
+    src/addrman.cpp \
     src/db.cpp \
     src/json/json_spirit_writer.cpp \
     src/json/json_spirit_value.cpp \
diff --git a/src/addrman.cpp b/src/addrman.cpp
new file mode 100644
index 0000000000..2ef666cf2c
--- /dev/null
+++ b/src/addrman.cpp
@@ -0,0 +1,506 @@
+// Copyright (c) 2012 Pieter Wuille
+// Distributed under the MIT/X11 software license, see the accompanying
+// file license.txt or http://www.opensource.org/licenses/mit-license.php.
+
+#include "addrman.h"
+
+using namespace std;
+
+int CAddrInfo::GetTriedBucket(const std::vector<unsigned char> &nKey) const
+{
+    CDataStream ss1(SER_GETHASH);
+    std::vector<unsigned char> vchKey = GetKey();
+    ss1 << nKey << vchKey;
+    uint64 hash1 = Hash(ss1.begin(), ss1.end()).Get64();
+
+    CDataStream ss2(SER_GETHASH);
+    std::vector<unsigned char> vchGroupKey = GetGroup();
+    ss2 << nKey << vchGroupKey << (hash1 % ADDRMAN_TRIED_BUCKETS_PER_GROUP);
+    uint64 hash2 = Hash(ss2.begin(), ss2.end()).Get64();
+    return hash2 % ADDRMAN_TRIED_BUCKET_COUNT;
+}
+
+int CAddrInfo::GetNewBucket(const std::vector<unsigned char> &nKey, const CNetAddr& src) const
+{
+    CDataStream ss1(SER_GETHASH);
+    std::vector<unsigned char> vchGroupKey = GetGroup();
+    std::vector<unsigned char> vchSourceGroupKey = src.GetGroup();
+    ss1 << nKey << vchGroupKey << vchSourceGroupKey;
+    uint64 hash1 = Hash(ss1.begin(), ss1.end()).Get64();
+
+    CDataStream ss2(SER_GETHASH);
+    ss2 << nKey << vchSourceGroupKey << (hash1 % ADDRMAN_NEW_BUCKETS_PER_SOURCE_GROUP);
+    uint64 hash2 = Hash(ss2.begin(), ss2.end()).Get64();
+    return hash2 % ADDRMAN_NEW_BUCKET_COUNT;
+}
+
+bool CAddrInfo::IsTerrible(int64 nNow) const
+{
+    if (nLastTry && nLastTry >= nNow-60) // never remove things tried 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*86400) // not seen in over a month
+        return true;
+
+    if (nLastSuccess==0 && nAttempts>=ADDRMAN_RETRIES) // tried three times and never a success
+        return true;
+
+    if (nNow-nLastSuccess > ADDRMAN_MIN_FAIL_DAYS*86400 && nAttempts>=ADDRMAN_MAX_FAILURES) // 10 successive failures in the last week
+        return true;
+
+    return false;
+}
+
+double CAddrInfo::GetChance(int64 nNow) const
+{
+    double fChance = 1.0;
+
+    int64 nSinceLastSeen = nNow - nTime;
+    int64 nSinceLastTry = nNow - nLastTry;
+
+    if (nSinceLastSeen < 0) nSinceLastSeen = 0;
+    if (nSinceLastTry < 0) nSinceLastTry = 0;
+
+    fChance *= 600.0 / (600.0 + nSinceLastSeen);
+
+    // deprioritize very recent attempts away
+    if (nSinceLastTry < 60*10)
+        fChance *= 0.01;
+
+    // deprioritize 50% after each failed attempt
+    for (int n=0; n<nAttempts; n++)
+        fChance /= 1.5;
+
+    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(int nRndPos1, int nRndPos2)
+{
+    if (nRndPos1 == nRndPos2)
+        return;
+
+    int nId1 = vRandom[nRndPos1];
+    int nId2 = vRandom[nRndPos2];
+
+    mapInfo[nId1].nRandomPos = nRndPos2;
+    mapInfo[nId2].nRandomPos = nRndPos1;
+
+    vRandom[nRndPos1] = nId2;
+    vRandom[nRndPos2] = nId1;
+}
+
+int CAddrMan::SelectTried(int nKBucket)
+{
+    std::vector<int> &vTried = vvTried[nKBucket];
+
+    // random shuffle the first few elements (using the entire list)
+    // find the least recently tried among them
+    int64 nOldest = -1;
+    for (int i=0; i<ADDRMAN_TRIED_ENTRIES_INSPECT_ON_EVICT && i<vTried.size(); i++)
+    {
+        int nPos = GetRandInt(vTried.size() - i) + i;
+        int nTemp = vTried[nPos];
+        vTried[nPos] = vTried[i];
+        vTried[i] = nTemp;
+        if (nOldest == -1 || mapInfo[nTemp].nLastSuccess < mapInfo[nOldest].nLastSuccess)
+           nOldest = nTemp;
+    }
+
+    return nOldest;
+}
+
+int CAddrMan::ShrinkNew(int nUBucket)
+{
+    std::set<int> &vNew = vvNew[nUBucket];
+
+    // first look for deletable items
+    for (std::set<int>::iterator it = vNew.begin(); it != vNew.end(); it++)
+    {
+        CAddrInfo &info = mapInfo[*it];
+        if (info.IsTerrible())
+        {
+            if (--info.nRefCount == 0)
+            {
+                SwapRandom(info.nRandomPos, vRandom.size()-1);
+                vRandom.pop_back();
+                mapAddr.erase(info);
+                mapInfo.erase(*it);
+                nNew--;
+            }
+            vNew.erase(it);
+            return 0;
+        }
+    }
+
+    // otherwise, select four randomly, and pick the oldest of those to replace
+    int n[4] = {GetRandInt(vNew.size()), GetRandInt(vNew.size()), GetRandInt(vNew.size()), GetRandInt(vNew.size())};
+    int nI = 0;
+    int nOldest = -1;
+    for (std::set<int>::iterator it = vNew.begin(); it != vNew.end(); it++)
+    {
+        if (nI == n[0] || nI == n[1] || nI == n[2] || nI == n[3])
+        {
+            if (nOldest == -1 || mapInfo[*it].nTime < mapInfo[nOldest].nTime)
+                nOldest = *it;
+        }
+        nI++;
+    }
+    CAddrInfo &info = mapInfo[nOldest];
+    if (--info.nRefCount == 0) 
+    {
+        SwapRandom(info.nRandomPos, vRandom.size()-1);
+        vRandom.pop_back();
+        mapAddr.erase(info);
+        mapInfo.erase(nOldest);
+        nNew--;
+    }
+    vNew.erase(nOldest);
+
+    return 1;
+}
+
+void CAddrMan::MakeTried(CAddrInfo& info, int nId, int nOrigin)
+{
+    // remove the entry from all new buckets
+    for (std::vector<std::set<int> >::iterator it = vvNew.begin(); it != vvNew.end(); it++)
+    {
+        if ((*it).erase(nId))
+            info.nRefCount--;
+    }
+    nNew--;
+
+    // what tried bucket to move the entry to
+    int nKBucket = info.GetTriedBucket(nKey);
+    std::vector<int> &vTried = vvTried[nKBucket];
+
+    // first check whether there is place to just add it
+    if (vTried.size() < ADDRMAN_TRIED_BUCKET_SIZE)
+    {
+        vTried.push_back(nId);
+        nTried++;
+        info.fInTried = true;
+        return;
+    }
+
+    // otherwise, find an item to evict
+    int nPos = SelectTried(nKBucket);
+
+    // find which new bucket it belongs to
+    int nUBucket = mapInfo[vTried[nPos]].GetNewBucket(nKey);
+    std::set<int> &vNew = vvNew[nUBucket];
+
+    // remove the to-be-replaced tried entry from the tried set
+    CAddrInfo& infoOld = mapInfo[vTried[nPos]];
+    infoOld.fInTried = false;
+    infoOld.nRefCount = 1;
+    // do not update nTried, as we are going to move something else there immediately
+
+    // check whether there is place in that one, 
+    if (vNew.size() < ADDRMAN_NEW_BUCKET_SIZE)
+    {
+        // if so, move it back there
+        vNew.insert(vTried[nPos]);
+    } else {
+        // otherwise, move it to the new bucket nId came from (there is certainly place there)
+        vvNew[nOrigin].insert(vTried[nPos]);
+    }
+    nNew++;
+
+    vTried[nPos] = nId;
+    // we just overwrote an entry in vTried; no need to update nTried
+    info.fInTried = true;
+    return;
+}
+
+void CAddrMan::Good_(const CService &addr, int64 nTime)
+{
+//    printf("Good: addr=%s\n", addr.ToString().c_str());
+
+    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.nTime = nTime;
+    info.nAttempts = 0;
+
+    // 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 = GetRandInt(vvNew.size());
+    int nUBucket = -1;
+    for (int n = 0; n < vvNew.size(); n++)
+    {
+        int nB = (n+nRnd) % vvNew.size();
+        std::set<int> &vNew = vvNew[nB];
+        if (vNew.count(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;
+
+    printf("Moving %s to tried\n", addr.ToString().c_str());
+
+    // move nId to the tried tables
+    MakeTried(info, nId, nUBucket);
+}
+
+bool CAddrMan::Add_(const CAddress &addr, const CNetAddr& source, int64 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 nUpdateInterval = (fCurrentlyOnline ? 60 * 60 : 24 * 60 * 60);
+        if (addr.nTime && (!pinfo->nTime || pinfo->nTime < addr.nTime - nUpdateInterval - nTimePenalty))
+            pinfo->nTime = max((int64)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 && (GetRandInt(nFactor) != 0))
+            return false;
+    } else {
+        pinfo = Create(addr, source, &nId);
+        pinfo->nTime = max((int64)0, (int64)pinfo->nTime - nTimePenalty);
+//        printf("Added %s [nTime=%fhr]\n", pinfo->ToString().c_str(), (GetAdjustedTime() - pinfo->nTime) / 3600.0);
+        nNew++;
+        fNew = true;
+    }
+
+    int nUBucket = pinfo->GetNewBucket(nKey, source);
+    std::set<int> &vNew = vvNew[nUBucket];
+    if (!vNew.count(nId))
+    {
+        pinfo->nRefCount++;
+        if (vNew.size() == ADDRMAN_NEW_BUCKET_SIZE)
+            ShrinkNew(nUBucket);
+        vvNew[nUBucket].insert(nId);
+    }
+    return fNew;
+}
+
+void CAddrMan::Attempt_(const CService &addr, int64 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++;
+}
+
+CAddress CAddrMan::Select_(int nUnkBias)
+{
+    if (size() == 0)
+        return CAddress();
+
+    double nCorTried = sqrt(nTried) * (100.0 - nUnkBias);
+    double nCorNew = sqrt(nNew) * nUnkBias;
+    if ((nCorTried + nCorNew)*GetRandInt(1<<30)/(1<<30) < nCorTried)
+    {
+        // use a tried node
+        double fChanceFactor = 1.0;
+        while(1)
+        {
+            int nKBucket = GetRandInt(vvTried.size());
+            std::vector<int> &vTried = vvTried[nKBucket];
+            if (vTried.size() == 0) continue;
+            int nPos = GetRandInt(vTried.size());
+            CAddrInfo &info = mapInfo[vTried[nPos]];
+            if (GetRandInt(1<<30) < fChanceFactor*info.GetChance()*(1<<30))
+                return info;
+            fChanceFactor *= 1.2;
+        }
+    } else {
+        // use an new node
+        double fChanceFactor = 1.0;
+        while(1)
+        {
+            int nUBucket = GetRandInt(vvNew.size());
+            std::set<int> &vNew = vvNew[nUBucket];
+            if (vNew.size() == 0) continue;
+            int nPos = GetRandInt(vNew.size());
+            std::set<int>::iterator it = vNew.begin();
+            while (nPos--)
+                it++;
+            CAddrInfo &info = mapInfo[*it];
+            if (GetRandInt(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<vvTried.size(); n++)
+    {
+        std::vector<int> &vTried = vvTried[n];
+        for (std::vector<int>::iterator it = vTried.begin(); it != vTried.end(); it++)
+        {
+            if (!setTried.count(*it)) return -11;
+            setTried.erase(*it);
+        }
+    }
+
+    for (int n=0; n<vvNew.size(); n++)
+    {
+        std::set<int> &vNew = vvNew[n];
+        for (std::set<int>::iterator it = vNew.begin(); it != vNew.end(); it++)
+        {
+            if (!mapNew.count(*it)) return -12;
+            if (--mapNew[*it] == 0)
+                mapNew.erase(*it);
+        }
+    }
+
+    if (setTried.size()) return -13;
+    if (mapNew.size()) return -15;
+
+    return 0;
+}
+#endif
+
+void CAddrMan::GetAddr_(std::vector<CAddress> &vAddr)
+{
+    int nNodes = ADDRMAN_GETADDR_MAX_PCT*vRandom.size()/100;
+    if (nNodes > ADDRMAN_GETADDR_MAX)
+        nNodes = ADDRMAN_GETADDR_MAX;
+
+    // perform a random shuffle over the first nNodes elements of vRandom (selecting from all)
+    for (int n = 0; n<nNodes; n++)
+    {
+        int nRndPos = GetRandInt(vRandom.size() - n) + n;
+        SwapRandom(n, nRndPos);
+        vAddr.push_back(mapInfo[vRandom[n]]);
+    }
+}
+
+void CAddrMan::Connected_(const CService &addr, int64 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 nUpdateInterval = 20 * 60;
+    if (nTime - info.nTime > nUpdateInterval)
+        info.nTime = nTime;
+}
diff --git a/src/addrman.h b/src/addrman.h
new file mode 100644
index 0000000000..350ecb2709
--- /dev/null
+++ b/src/addrman.h
@@ -0,0 +1,499 @@
+// Copyright (c) 2012 Pieter Wuille
+// Distributed under the MIT/X11 software license, see the accompanying
+// file license.txt or http://www.opensource.org/licenses/mit-license.php.
+#ifndef _BITCOIN_ADDRMAN
+#define _BITCOIN_ADDRMAN 1
+
+#include "netbase.h"
+#include "protocol.h"
+#include "util.h"
+
+
+#include <map>
+#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 succesfull connection by us
+    int64 nLastSuccess;
+
+    // last try whatsoever by us:
+    // int64 CAddress::nLastTry
+
+    // connection attempts since last succesful 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)
+    {
+        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 nNow = GetAdjustedTime()) const;
+
+    // Calculate the relative chance this entry should be given when selecting nodes to connect to
+    double GetChance(int64 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-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 datastructure.
+
+// 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
+
+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 nId's
+    std::map<int, CAddrInfo> mapInfo;
+
+    // find an nId based on its network address
+    std::map<CNetAddr, int> mapAddr;
+
+    // randomly-ordered vector of all nId's
+    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(int nRandomPos1, 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 nTime);
+
+    // Add an entry to the "new" table.
+    bool Add_(const CAddress &addr, const CNetAddr& source, int64 nTimePenalty);
+
+    // Mark an entry as attempted to connect.
+    void Attempt_(const CService &addr, int64 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 nTime);
+
+public:
+
+    IMPLEMENT_SERIALIZE
+    (({
+        // serialized format:
+        // * version byte (currently 0)
+        // * nKey
+        // * nNew
+        // * nTried
+        // * number of "new" buckets
+        // * all nNew addrinfo's in vvNew
+        // * all nTried addrinfo's 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.
+        CRITICAL_BLOCK(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
+        CRITICAL_BLOCK(cs)
+        {
+            int err;
+            if ((err=Check_()))
+                printf("ADDRMAN CONSISTENCY CHECK FAILED!!! err=%i\n", err);
+        }
+#endif
+    }
+
+    // Add a single address.
+    bool Add(const CAddress &addr, const CNetAddr& source, int64 nTimePenalty = 0)
+    {
+        bool fRet = false;
+        CRITICAL_BLOCK(cs)
+        {
+            Check();
+            fRet |= Add_(addr, source, nTimePenalty);
+            Check();
+        }
+        if (fRet)
+            printf("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 nTimePenalty = 0)
+    {
+        int nAdd = 0;
+        CRITICAL_BLOCK(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)
+            printf("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 nTime = GetAdjustedTime())
+    {
+        CRITICAL_BLOCK(cs)
+        {
+            Check();
+            Good_(addr, nTime);
+            Check();
+        }
+    }
+
+    // Mark an entry as connection attempted to.
+    void Attempt(const CService &addr, int64 nTime = GetAdjustedTime())
+    {
+        CRITICAL_BLOCK(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;
+        CRITICAL_BLOCK(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;
+        CRITICAL_BLOCK(cs)
+            GetAddr_(vAddr);
+        Check();
+        return vAddr;
+    }
+
+    // Mark an entry as currently-connected-to.
+    void Connected(const CService &addr, int64 nTime = GetAdjustedTime())
+    {
+        CRITICAL_BLOCK(cs)
+        {
+            Check();
+            Connected_(addr, nTime);
+            Check();
+        }
+    }
+};
+
+#endif
diff --git a/src/db.cpp b/src/db.cpp
index 7c3937a49f..3bdfd64556 100644
--- a/src/db.cpp
+++ b/src/db.cpp
@@ -624,44 +624,65 @@ bool CAddrDB::WriteAddress(const CAddress& addr)
     return Write(make_pair(string("addr"), addr.GetKey()), addr);
 }
 
+bool CAddrDB::WriteAddrman(const CAddrMan& addrman)
+{
+    return Write(string("addrman"), addrman);
+}
+
 bool CAddrDB::EraseAddress(const CAddress& addr)
 {
     return Erase(make_pair(string("addr"), addr.GetKey()));
 }
 
-bool CAddrDB::LoadAddresses()
+bool CAddrDB::LoadAddresses(bool &fUpdate)
 {
-    CRITICAL_BLOCK(cs_mapAddresses)
+    bool fAddrMan = false;
+    if (Read(string("addrman"), addrman))
     {
-        // Get cursor
-        Dbc* pcursor = GetCursor();
-        if (!pcursor)
+        printf("Loaded %i addresses\n", addrman.size());
+        fAddrMan = true;
+    }
+
+    vector<CAddress> vAddr;
+
+    // Get cursor
+    Dbc* pcursor = GetCursor();
+    if (!pcursor)
+        return false;
+
+    loop
+    {
+        // Read next record
+        CDataStream ssKey;
+        CDataStream ssValue;
+        int ret = ReadAtCursor(pcursor, ssKey, ssValue);
+        if (ret == DB_NOTFOUND)
+            break;
+        else if (ret != 0)
             return false;
 
-        loop
+        // Unserialize
+        string strType;
+        ssKey >> strType;
+        if (strType == "addr")
         {
-            // Read next record
-            CDataStream ssKey;
-            CDataStream ssValue;
-            int ret = ReadAtCursor(pcursor, ssKey, ssValue);
-            if (ret == DB_NOTFOUND)
-                break;
-            else if (ret != 0)
-                return false;
-
-            // Unserialize
-            string strType;
-            ssKey >> strType;
-            if (strType == "addr")
+            if (fAddrMan)
+                fUpdate = true;
+            else
             {
                 CAddress addr;
                 ssValue >> addr;
-                mapAddresses.insert(make_pair(addr.GetKey(), addr));
+                vAddr.push_back(addr);
             }
+
         }
-        pcursor->close();
+    }
+    pcursor->close();
 
-        printf("Loaded %d addresses\n", mapAddresses.size());
+    if (!fAddrMan)
+    {
+        addrman.Add(vAddr, CNetAddr("0.0.0.0"));
+        printf("Loaded %i addresses\n", addrman.size());
     }
 
     return true;
@@ -669,7 +690,11 @@ bool CAddrDB::LoadAddresses()
 
 bool LoadAddresses()
 {
-    return CAddrDB("cr+").LoadAddresses();
+    bool fUpdate = false;
+    bool fRet = CAddrDB("cr+").LoadAddresses(fUpdate);
+    if (fUpdate)
+        CDB::Rewrite("addr.dat", "\004addr");
+    return fRet;
 }
 
 
diff --git a/src/db.h b/src/db.h
index 74cb5d8d5f..2a869d511b 100644
--- a/src/db.h
+++ b/src/db.h
@@ -16,6 +16,7 @@
 class CAccount;
 class CAccountingEntry;
 class CAddress;
+class CAddrMan;
 class CBlockLocator;
 class CDiskBlockIndex;
 class CDiskTxPos;
@@ -307,7 +308,8 @@ private:
 public:
     bool WriteAddress(const CAddress& addr);
     bool EraseAddress(const CAddress& addr);
-    bool LoadAddresses();
+    bool WriteAddrman(const CAddrMan& addr);
+    bool LoadAddresses(bool &fUpdate);
 };
 
 bool LoadAddresses();
diff --git a/src/init.cpp b/src/init.cpp
index 6fa56b939f..b00a6be81d 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -513,7 +513,7 @@ bool AppInit2(int argc, char* argv[])
             CAddress addr(CService(strAddr, GetDefaultPort(), fAllowDNS));
             addr.nTime = 0; // so it won't relay unless successfully connected
             if (addr.IsValid())
-                AddAddress(addr);
+                addrman.Add(addr, CNetAddr("127.0.0.1"));
         }
     }
 
diff --git a/src/irc.cpp b/src/irc.cpp
index 7a6f40cfad..09bacc1658 100644
--- a/src/irc.cpp
+++ b/src/irc.cpp
@@ -341,7 +341,7 @@ void ThreadIRCSeed2(void* parg)
                 if (DecodeAddress(pszName, addr))
                 {
                     addr.nTime = GetAdjustedTime();
-                    if (AddAddress(addr, 51 * 60))
+                    if (addrman.Add(addr, addrConnect, 51 * 60))
                         printf("IRC got new address: %s\n", addr.ToString().c_str());
                     nGotIRCAddresses++;
                 }
diff --git a/src/main.cpp b/src/main.cpp
index efbaea1879..d795ca1df9 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -2235,11 +2235,18 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
             }
 
             // Get recent addresses
-            if (pfrom->nVersion >= 31402 || mapAddresses.size() < 1000)
+            if (pfrom->nVersion >= 31402 || addrman.size() < 1000)
             {
                 pfrom->PushMessage("getaddr");
                 pfrom->fGetAddr = true;
             }
+            addrman.Good(pfrom->addr);
+        } else {
+            if (((CNetAddr)pfrom->addr) == (CNetAddr)addrFrom)
+            {
+                addrman.Add(addrFrom, addrFrom);
+                addrman.Good(addrFrom);
+            }
         }
 
         // Ask the first connected node for block updates
@@ -2285,7 +2292,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
         vRecv >> vAddr;
 
         // Don't want addr from older versions unless seeding
-        if (pfrom->nVersion < 31402 && mapAddresses.size() > 1000)
+        if (pfrom->nVersion < 31402 && addrman.size() > 1000)
             return true;
         if (vAddr.size() > 1000)
         {
@@ -2294,8 +2301,6 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
         }
 
         // Store the new addresses
-        CAddrDB addrDB;
-        addrDB.TxnBegin();
         int64 nNow = GetAdjustedTime();
         int64 nSince = nNow - 10 * 60;
         BOOST_FOREACH(CAddress& addr, vAddr)
@@ -2307,7 +2312,6 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
                 continue;
             if (addr.nTime <= 100000000 || addr.nTime > nNow + 10 * 60)
                 addr.nTime = nNow - 5 * 24 * 60 * 60;
-            AddAddress(addr, 2 * 60 * 60, &addrDB);
             pfrom->AddAddressKnown(addr);
             if (addr.nTime > nSince && !pfrom->fGetAddr && vAddr.size() <= 10 && addr.IsRoutable())
             {
@@ -2339,7 +2343,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
                 }
             }
         }
-        addrDB.TxnCommit();  // Save addresses (it's ok if this fails)
+        addrman.Add(vAddr, pfrom->addr, 2 * 60 * 60);
         if (vAddr.size() < 1000)
             pfrom->fGetAddr = false;
     }
@@ -2590,25 +2594,10 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
 
     else if (strCommand == "getaddr")
     {
-        // Nodes rebroadcast an addr every 24 hours
         pfrom->vAddrToSend.clear();
-        int64 nSince = GetAdjustedTime() - 3 * 60 * 60; // in the last 3 hours
-        CRITICAL_BLOCK(cs_mapAddresses)
-        {
-            unsigned int nCount = 0;
-            BOOST_FOREACH(const PAIRTYPE(vector<unsigned char>, CAddress)& item, mapAddresses)
-            {
-                const CAddress& addr = item.second;
-                if (addr.nTime > nSince)
-                    nCount++;
-            }
-            BOOST_FOREACH(const PAIRTYPE(vector<unsigned char>, CAddress)& item, mapAddresses)
-            {
-                const CAddress& addr = item.second;
-                if (addr.nTime > nSince && GetRand(nCount) < 2500)
-                    pfrom->PushAddress(addr);
-            }
-        }
+        vector<CAddress> vAddr = addrman.GetAddr();
+        BOOST_FOREACH(const CAddress &addr, vAddr)
+            pfrom->PushAddress(addr);
     }
 
 
@@ -2850,35 +2839,6 @@ bool SendMessages(CNode* pto, bool fSendTrickle)
             nLastRebroadcast = GetTime();
         }
 
-        // Clear out old addresses periodically so it's not too much work at once
-        static int64 nLastClear;
-        if (nLastClear == 0)
-            nLastClear = GetTime();
-        if (GetTime() - nLastClear > 10 * 60 && vNodes.size() >= 3)
-        {
-            nLastClear = GetTime();
-            CRITICAL_BLOCK(cs_mapAddresses)
-            {
-                CAddrDB addrdb;
-                int64 nSince = GetAdjustedTime() - 14 * 24 * 60 * 60;
-                for (map<vector<unsigned char>, CAddress>::iterator mi = mapAddresses.begin();
-                     mi != mapAddresses.end();)
-                {
-                    const CAddress& addr = (*mi).second;
-                    if (addr.nTime < nSince)
-                    {
-                        if (mapAddresses.size() < 1000 || GetTime() > nLastClear + 20)
-                            break;
-                        addrdb.EraseAddress(addr);
-                        mapAddresses.erase(mi++);
-                    }
-                    else
-                        mi++;
-                }
-            }
-        }
-
-
         //
         // Message: addr
         //
diff --git a/src/makefile.linux-mingw b/src/makefile.linux-mingw
index 9212698018..40ce1dcdca 100644
--- a/src/makefile.linux-mingw
+++ b/src/makefile.linux-mingw
@@ -45,6 +45,7 @@ HEADERS = $(wildcard *.h)
 OBJS= \
     obj/checkpoints.o \
     obj/netbase.o \
+    obj/addrman.o \
     obj/crypter.o \
     obj/key.o \
     obj/db.o \
diff --git a/src/makefile.mingw b/src/makefile.mingw
index c55e17a36e..f7dfcc74c1 100644
--- a/src/makefile.mingw
+++ b/src/makefile.mingw
@@ -43,6 +43,7 @@ HEADERS = $(wildcard *.h)
 OBJS= \
     obj/checkpoints.o \
     obj/netbase.o \
+    obj/addrman.o \
     obj/crypter.o \
     obj/key.o \
     obj/db.o \
diff --git a/src/makefile.osx b/src/makefile.osx
index 9943271a29..8790d92ce4 100644
--- a/src/makefile.osx
+++ b/src/makefile.osx
@@ -60,6 +60,7 @@ CFLAGS=-mmacosx-version-min=10.5 -arch i386 -O3 \
 OBJS= \
     obj/checkpoints.o \
     obj/netbase.o \
+    obj/addrman.o \
     obj/crypter.o \
     obj/key.o \
     obj/db.o \
diff --git a/src/makefile.unix b/src/makefile.unix
index 23c6f723a3..92c1b97e1f 100644
--- a/src/makefile.unix
+++ b/src/makefile.unix
@@ -91,6 +91,7 @@ xCXXFLAGS=-pthread -Wextra -Wno-sign-compare -Wno-char-subscripts -Wno-invalid-o
 OBJS= \
     obj/checkpoints.o \
     obj/netbase.o \
+    obj/addrman.o \
     obj/crypter.o \
     obj/key.o \
     obj/db.o \
diff --git a/src/net.cpp b/src/net.cpp
index 94ef7e7b3a..e9ec233a13 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -9,6 +9,7 @@
 #include "net.h"
 #include "init.h"
 #include "strlcpy.h"
+#include "addrman.h"
 
 #ifdef WIN32
 #include <string.h>
@@ -50,11 +51,10 @@ static CNode* pnodeLocalHost = NULL;
 uint64 nLocalHostNonce = 0;
 array<int, THREAD_MAX> vnThreadsRunning;
 static SOCKET hListenSocket = INVALID_SOCKET;
+CAddrMan addrman;
 
 vector<CNode*> vNodes;
 CCriticalSection cs_vNodes;
-map<vector<unsigned char>, CAddress> mapAddresses;
-CCriticalSection cs_mapAddresses;
 map<CInv, CDataStream> mapRelay;
 deque<pair<int64, CInv> > vRelayExpiration;
 CCriticalSection cs_mapRelay;
@@ -280,86 +280,9 @@ void ThreadGetMyExternalIP(void* parg)
 
 
 
-bool AddAddress(CAddress addr, int64 nTimePenalty, CAddrDB *pAddrDB)
-{
-    if (!addr.IsRoutable())
-        return false;
-    if ((CService)addr == (CService)addrLocalHost)
-        return false;
-    addr.nTime = max((int64)0, (int64)addr.nTime - nTimePenalty);
-    bool fUpdated = false;
-    bool fNew = false;
-    CAddress addrFound = addr;
-
-    CRITICAL_BLOCK(cs_mapAddresses)
-    {
-        map<vector<unsigned char>, CAddress>::iterator it = mapAddresses.find(addr.GetKey());
-        if (it == mapAddresses.end())
-        {
-            // New address
-            printf("AddAddress(%s)\n", addr.ToString().c_str());
-            mapAddresses.insert(make_pair(addr.GetKey(), addr));
-            fUpdated = true;
-            fNew = true;
-        }
-        else
-        {
-            addrFound = (*it).second;
-            if ((addrFound.nServices | addr.nServices) != addrFound.nServices)
-            {
-                // Services have been added
-                addrFound.nServices |= addr.nServices;
-                fUpdated = true;
-            }
-            bool fCurrentlyOnline = (GetAdjustedTime() - addr.nTime < 24 * 60 * 60);
-            int64 nUpdateInterval = (fCurrentlyOnline ? 60 * 60 : 24 * 60 * 60);
-            if (addrFound.nTime < addr.nTime - nUpdateInterval)
-            {
-                // Periodically update most recently seen time
-                addrFound.nTime = addr.nTime;
-                fUpdated = true;
-            }
-        }
-    }
-    // There is a nasty deadlock bug if this is done inside the cs_mapAddresses
-    // CRITICAL_BLOCK:
-    // Thread 1:  begin db transaction (locks inside-db-mutex)
-    //            then AddAddress (locks cs_mapAddresses)
-    // Thread 2:  AddAddress (locks cs_mapAddresses)
-    //             ... then db operation hangs waiting for inside-db-mutex
-    if (fUpdated)
-    {
-        if (pAddrDB)
-            pAddrDB->WriteAddress(addrFound);
-        else
-            CAddrDB().WriteAddress(addrFound);
-    }
-    return fNew;
-}
-
 void AddressCurrentlyConnected(const CService& addr)
 {
-    CAddress *paddrFound = NULL;
-
-    CRITICAL_BLOCK(cs_mapAddresses)
-    {
-        // Only if it's been published already
-        map<vector<unsigned char>, CAddress>::iterator it = mapAddresses.find(addr.GetKey());
-        if (it != mapAddresses.end())
-            paddrFound = &(*it).second;
-    }
-
-    if (paddrFound)
-    {
-        int64 nUpdateInterval = 20 * 60;
-        if (paddrFound->nTime < GetAdjustedTime() - nUpdateInterval)
-        {
-            // Periodically update most recently seen time
-            paddrFound->nTime = GetAdjustedTime();
-            CAddrDB addrdb;
-            addrdb.WriteAddress(*paddrFound);
-        }
-    }
+    addrman.Connected(addr);
 }
 
 
@@ -506,13 +429,11 @@ CNode* ConnectNode(CAddress addrConnect, int64 nTimeout)
     }
 
     /// debug print
-    printf("trying connection %s lastseen=%.1fhrs lasttry=%.1fhrs\n",
+    printf("trying connection %s lastseen=%.1fhrs\n",
         addrConnect.ToString().c_str(),
-        (double)(addrConnect.nTime - GetAdjustedTime())/3600.0,
-        (double)(addrConnect.nLastTry - GetAdjustedTime())/3600.0);
+        (double)(addrConnect.nTime - GetAdjustedTime())/3600.0);
 
-    CRITICAL_BLOCK(cs_mapAddresses)
-        mapAddresses[addrConnect.GetKey()].nLastTry = GetAdjustedTime();
+    addrman.Attempt(addrConnect);
 
     // Connect
     SOCKET hSocket;
@@ -1126,12 +1047,15 @@ void MapPort(bool /* unused fMapPort */)
 
 
 
-
-static const char *strDNSSeed[] = {
-    "bitseed.xf2.org",
-    "dnsseed.bluematt.me",
-    "seed.bitcoin.sipa.be",
-    "dnsseed.bitcoin.dashjr.org",
+// DNS seeds
+// Each pair gives a source name and a seed name.
+// The first name is used as information source for addrman.
+// The second name should resolve to a list of seed addresses.
+static const char *strDNSSeed[][2] = {
+    {"xf2.org", "bitseed.xf2.org"},
+    {"bluematt.me", "dnsseed.bluematt.me"},
+    {"bitcoin.sipa.be", "seed.bitcoin.sipa.be"},
+    {"dashjr.org", "dnsseed.bitcoin.dashjr.org"},
 };
 
 void ThreadDNSAddressSeed(void* parg)
@@ -1164,22 +1088,18 @@ void ThreadDNSAddressSeed2(void* parg)
 
         for (int seed_idx = 0; seed_idx < ARRAYLEN(strDNSSeed); seed_idx++) {
             vector<CNetAddr> vaddr;
-            if (LookupHost(strDNSSeed[seed_idx], vaddr))
+            vector<CAddress> vAdd;
+            if (LookupHost(strDNSSeed[seed_idx][1], vaddr))
             {
-                CAddrDB addrDB;
-                addrDB.TxnBegin();
-                BOOST_FOREACH (CNetAddr& ip, vaddr)
+                BOOST_FOREACH(CNetAddr& ip, vaddr)
                 {
-                    if (ip.IsRoutable())
-                    {
-                        CAddress addr(CService(ip, GetDefaultPort()), NODE_NETWORK);
-                        addr.nTime = 0;
-                        AddAddress(addr, 0, &addrDB);
-                        found++;
-                    }
+                    CAddress addr = CAddress(CService(ip, GetDefaultPort()));
+                    addr.nTime = 0;
+                    vAdd.push_back(addr);
+                    found++;
                 }
-                addrDB.TxnCommit();  // Save addresses (it's ok if this fails)
             }
+            addrman.Add(vAdd, CNetAddr(strDNSSeed[seed_idx][0], true));
         }
     }
 
@@ -1278,7 +1198,37 @@ unsigned int pnSeed[] =
     0xc461d84a, 0xb2dbe247,
 };
 
+void DumpAddresses()
+{
+    CAddrDB adb;
+    adb.WriteAddrman(addrman);
+}
 
+void ThreadDumpAddress2(void* parg)
+{
+    vnThreadsRunning[THREAD_DUMPADDRESS]++;
+    while (!fShutdown)
+    {
+        DumpAddresses();
+        vnThreadsRunning[THREAD_DUMPADDRESS]--;
+        Sleep(100000);
+        vnThreadsRunning[THREAD_DUMPADDRESS]++;
+    }
+    vnThreadsRunning[THREAD_DUMPADDRESS]--;
+}
+
+void ThreadDumpAddress(void* parg)
+{
+    IMPLEMENT_RANDOMIZE_STACK(ThreadDumpAddress(parg));
+    try
+    {
+        ThreadDumpAddress2(parg);
+    }
+    catch (std::exception& e) {
+        PrintException(&e, "ThreadDumpAddress()");
+    }
+    printf("ThreadDumpAddress exiting\n");
+}
 
 void ThreadOpenConnections(void* parg)
 {
@@ -1327,6 +1277,8 @@ void ThreadOpenConnections2(void* parg)
     int64 nStart = GetTime();
     loop
     {
+        int nOutbound = 0;
+
         vnThreadsRunning[THREAD_OPENCONNECTIONS]--;
         Sleep(500);
         vnThreadsRunning[THREAD_OPENCONNECTIONS]++;
@@ -1336,7 +1288,7 @@ void ThreadOpenConnections2(void* parg)
         // Limit outbound connections
         loop
         {
-            int nOutbound = 0;
+            nOutbound = 0;
             CRITICAL_BLOCK(cs_vNodes)
                 BOOST_FOREACH(CNode* pnode, vNodes)
                     if (!pnode->fInbound)
@@ -1354,16 +1306,11 @@ void ThreadOpenConnections2(void* parg)
 
         bool fAddSeeds = false;
 
-        CRITICAL_BLOCK(cs_mapAddresses)
-        {
-            // Add seed nodes if IRC isn't working
-            bool fTOR = (fUseProxy && addrProxy.GetPort() == 9050);
-            if (mapAddresses.empty() && (GetTime() - nStart > 60 || fTOR) && !fTestNet)
-                fAddSeeds = true;
-        }
-
-        if (fAddSeeds)
+        // Add seed nodes if IRC isn't working
+        bool fTOR = (fUseProxy && addrProxy.GetPort() == 9050);
+        if (addrman.size()==0 && (GetTime() - nStart > 60 || fTOR) && !fTestNet)
         {
+            std::vector<CAddress> vAdd;
             for (int i = 0; i < ARRAYLEN(pnSeed); i++)
             {
                 // It'll only connect to one or two seed nodes because once it connects,
@@ -1375,8 +1322,9 @@ void ThreadOpenConnections2(void* parg)
                 memcpy(&ip, &pnSeed[i], sizeof(ip));
                 CAddress addr(CService(ip, GetDefaultPort()));
                 addr.nTime = GetTime()-GetRand(nOneWeek)-nOneWeek;
-                AddAddress(addr);
+                vAdd.push_back(addr);
             }
+            addrman.Add(vAdd, CNetAddr("127.0.0.1"));
         }
 
         //
@@ -1394,59 +1342,28 @@ void ThreadOpenConnections2(void* parg)
 
         int64 nANow = GetAdjustedTime();
 
-        CRITICAL_BLOCK(cs_mapAddresses)
+        int nTries = 0;
+        loop
         {
-            BOOST_FOREACH(const PAIRTYPE(vector<unsigned char>, CAddress)& item, mapAddresses)
-            {
-                const CAddress& addr = item.second;
-                if (!addr.IsIPv4() || !addr.IsValid() || setConnected.count(addr.GetGroup()))
-                    continue;
-                int64 nSinceLastSeen = nANow - addr.nTime;
-                int64 nSinceLastTry = nANow - addr.nLastTry;
-
-                // Randomize the order in a deterministic way, putting the standard port first
-                int64 nRandomizer = (uint64)(nStart * 4951 + addr.nLastTry * 9567851 + addr.GetHash()) % (2 * 60 * 60);
-                if (addr.GetPort() != GetDefaultPort())
-                    nRandomizer += 2 * 60 * 60;
-
-                // Last seen  Base retry frequency
-                //   <1 hour   10 min
-                //    1 hour    1 hour
-                //    4 hours   2 hours
-                //   24 hours   5 hours
-                //   48 hours   7 hours
-                //    7 days   13 hours
-                //   30 days   27 hours
-                //   90 days   46 hours
-                //  365 days   93 hours
-                int64 nDelay = (int64)(3600.0 * sqrt(fabs((double)nSinceLastSeen) / 3600.0) + nRandomizer);
-
-                // Fast reconnect for one hour after last seen
-                if (nSinceLastSeen < 60 * 60)
-                    nDelay = 10 * 60;
-
-                // Limit retry frequency
-                if (nSinceLastTry < nDelay)
-                    continue;
+            // use an nUnkBias between 10 (no outgoing connections) and 90 (8 outgoing connections)
+            CAddress addr = addrman.Select(10 + min(nOutbound,8)*10);
 
-                // If we have IRC, we'll be notified when they first come online,
-                // and again every 24 hours by the refresh broadcast.
-                if (nGotIRCAddresses > 0 && vNodes.size() >= 2 && nSinceLastSeen > 24 * 60 * 60)
-                    continue;
+            // if we selected an invalid address, restart
+            if (!addr.IsIPv4() || !addr.IsValid() || setConnected.count(addr.GetGroup()) || addr == addrLocalHost)
+                break;
 
-                // Only try the old stuff if we don't have enough connections
-                if (vNodes.size() >= 8 && nSinceLastSeen > 24 * 60 * 60)
-                    continue;
+            nTries++;
 
-                // If multiple addresses are ready, prioritize by time since
-                // last seen and time since last tried.
-                int64 nScore = min(nSinceLastTry, (int64)24 * 60 * 60) - nSinceLastSeen - nRandomizer;
-                if (nScore > nBest)
-                {
-                    nBest = nScore;
-                    addrConnect = addr;
-                }
-            }
+            // only consider very recently tried nodes after 30 failed attempts
+            if (nANow - addr.nLastTry < 600 && nTries < 30)
+                continue;
+
+            // do not allow non-default ports, unless after 50 invalid addresses selected already
+            if (addr.GetPort() != GetDefaultPort() && nTries < 50)
+                continue;
+
+            addrConnect = addr;
+            break;
         }
 
         if (addrConnect.IsValid())
@@ -1820,6 +1737,10 @@ void StartNode(void* parg)
     if (!CreateThread(ThreadMessageHandler, NULL))
         printf("Error: CreateThread(ThreadMessageHandler) failed\n");
 
+    // Dump network addresses
+    if (!CreateThread(ThreadDumpAddress, NULL))
+        printf("Error; CreateThread(ThreadDumpAddress) failed\n");
+
     // Generate coins in the background
     GenerateBitcoins(GetBoolArg("-gen", false), pwalletMain);
 }
@@ -1849,10 +1770,11 @@ bool StopNode()
     if (fHaveUPnP && vnThreadsRunning[THREAD_UPNP] > 0) printf("ThreadMapPort still running\n");
     if (vnThreadsRunning[THREAD_DNSSEED] > 0) printf("ThreadDNSAddressSeed still running\n");
     if (vnThreadsRunning[THREAD_ADDEDCONNECTIONS] > 0) printf("ThreadOpenAddedConnections still running\n");
+    if (vnThreadsRunning[THREAD_DUMPADDRESS] > 0) printf("ThreadDumpAddresses still running\n");
     while (vnThreadsRunning[THREAD_MESSAGEHANDLER] > 0 || vnThreadsRunning[THREAD_RPCSERVER] > 0)
         Sleep(20);
     Sleep(50);
-
+    DumpAddresses();
     return true;
 }
 
diff --git a/src/net.h b/src/net.h
index d3e10f5a89..b44cc5d9b5 100644
--- a/src/net.h
+++ b/src/net.h
@@ -17,6 +17,7 @@
 #include "mruset.h"
 #include "netbase.h"
 #include "protocol.h"
+#include "addrman.h"
 
 class CAddrDB;
 class CRequestTracker;
@@ -32,7 +33,6 @@ static const unsigned int PUBLISH_HOPS = 5;
 
 bool RecvLine(SOCKET hSocket, std::string& strLine);
 bool GetMyExternalIP(CNetAddr& ipRet);
-bool AddAddress(CAddress addr, int64 nTimePenalty=0, CAddrDB *pAddrDB=NULL);
 void AddressCurrentlyConnected(const CService& addr);
 CNode* FindNode(const CNetAddr& ip);
 CNode* FindNode(const CService& ip);
@@ -80,6 +80,7 @@ enum threadId
     THREAD_UPNP,
     THREAD_DNSSEED,
     THREAD_ADDEDCONNECTIONS,
+    THREAD_DUMPADDRESS,
 
     THREAD_MAX
 };
@@ -90,11 +91,10 @@ extern uint64 nLocalServices;
 extern CAddress addrLocalHost;
 extern uint64 nLocalHostNonce;
 extern boost::array<int, THREAD_MAX> vnThreadsRunning;
+extern CAddrMan addrman;
 
 extern std::vector<CNode*> vNodes;
 extern CCriticalSection cs_vNodes;
-extern std::map<std::vector<unsigned char>, CAddress> mapAddresses;
-extern CCriticalSection cs_mapAddresses;
 extern std::map<CInv, CDataStream> mapRelay;
 extern std::deque<std::pair<int64, CInv> > vRelayExpiration;
 extern CCriticalSection cs_mapRelay;
diff --git a/src/netbase.cpp b/src/netbase.cpp
index 7799a65972..baf7c412a0 100644
--- a/src/netbase.cpp
+++ b/src/netbase.cpp
@@ -519,15 +519,22 @@ bool CNetAddr::GetIn6Addr(struct in6_addr* pipv6Addr) const
 std::vector<unsigned char> CNetAddr::GetGroup() const
 {
     std::vector<unsigned char> vchRet;
-    int nClass = 0; // 0=IPv6, 1=IPv4, 255=unroutable
+    int nClass = 0; // 0=IPv6, 1=IPv4, 254=local, 255=unroutable
     int nStartByte = 0;
     int nBits = 16;
 
-    // for unroutable addresses, each address is considered different
+    // all local addresses belong to the same group
+    if (IsLocal())
+    {
+        nClass = 254;
+        nBits = 0;
+    }
+
+    // all unroutable addresses belong to the same group
     if (!IsRoutable())
     {
         nClass = 255;
-        nBits = 128;
+        nBits = 0;
     }
     // for IPv4 addresses, '1' + the 16 higher-order bits of the IP
     // includes mapped IPv4, SIIT translated IPv4, and the well-known prefix
diff --git a/src/protocol.h b/src/protocol.h
index b70dd71b82..613c47f042 100644
--- a/src/protocol.h
+++ b/src/protocol.h
@@ -94,7 +94,7 @@ class CAddress : public CService
         unsigned int nTime;
 
         // memory only
-        unsigned int nLastTry;
+        int64 nLastTry;
 };
 
 class CInv
diff --git a/src/uint256.h b/src/uint256.h
index caf6fa118b..783e7069e9 100644
--- a/src/uint256.h
+++ b/src/uint256.h
@@ -348,6 +348,10 @@ public:
         return sizeof(pn);
     }
 
+    uint64 Get64(int n=0) const
+    {
+        return pn[2*n] | (uint64)pn[2*n+1] << 32;
+    }
 
     unsigned int GetSerializeSize(int nType=0, int nVersion=PROTOCOL_VERSION) const
     {