CAddrMan: stochastic address manager

Design goals:
 * Only keep a limited number of addresses around, so that addr.dat does not grow without bound.
 * Keep the address tables in-memory, and occasionally write the table to addr.dat.
 * Make sure no (localized) attacker can fill the entire table with his nodes/addresses.

See comments in addrman.h for more detailed information.

1 files changed, 499 insertions, 0 deletions

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