addrman.h
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	// Copyright (c) 2012 Pieter Wuille
	// Distributed under the MIT/X11 software license, see the accompanying
	// file COPYING or http://www.opensource.org/licenses/mit-license.php.
	#ifndef _BITCOIN_ADDRMAN
	#define _BITCOIN_ADDRMAN 1

	#include "netbase.h"
	#include "protocol.h"
	#include "util.h"
	#include "sync.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 successful connection by us
	int64 nLastSuccess;

	// last try whatsoever by us:
	// int64 CAddress::nLastTry

	// connection attempts since last successful attempt
	int nAttempts;

	// reference count in new sets (memory only)
	int nRefCount;

	// in tried set? (memory only)
	bool fInTried;

	// position in vRandom
	int nRandomPos;

	friend class CAddrMan;

	public:

	IMPLEMENT_SERIALIZE(
	CAddress* pthis = (CAddress*)(this);
	READWRITE(*pthis);
	READWRITE(source);
	READWRITE(nLastSuccess);
	READWRITE(nAttempts);
	)

	void Init()
	{
	nLastSuccess = 0;
	nLastTry = 0;
	nAttempts = 0;
	nRefCount = 0;
	fInTried = false;
	nRandomPos = -1;
	}

	CAddrInfo(const CAddress &addrIn, const CNetAddr &addrSource) : CAddress(addrIn), source(addrSource)
	{
	Init();
	}

	CAddrInfo() : CAddress(), source()
	{
	Init();
	}

	// Calculate in which "tried" bucket this entry belongs
	int GetTriedBucket(const std::vector<unsigned char> &nKey) const;

	// Calculate in which "new" bucket this entry belongs, given a certain source
	int GetNewBucket(const std::vector<unsigned char> &nKey, const CNetAddr& src) const;

	// Calculate in which "new" bucket this entry belongs, using its default source
	int GetNewBucket(const std::vector<unsigned char> &nKey) const
	{
	return GetNewBucket(nKey, source);
	}

	// Determine whether the statistics about this entry are bad enough so that it can just be deleted
	bool IsTerrible(int64 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 data structure.

	// total number of buckets for tried addresses
	#define ADDRMAN_TRIED_BUCKET_COUNT 64

	// maximum allowed number of entries in buckets for tried addresses
	#define ADDRMAN_TRIED_BUCKET_SIZE 64

	// total number of buckets for new addresses
	#define ADDRMAN_NEW_BUCKET_COUNT 256

	// maximum allowed number of entries in buckets for new addresses
	#define ADDRMAN_NEW_BUCKET_SIZE 64

	// over how many buckets entries with tried addresses from a single group (/16 for IPv4) are spread
	#define ADDRMAN_TRIED_BUCKETS_PER_GROUP 4

	// over how many buckets entries with new addresses originating from a single group are spread
	#define ADDRMAN_NEW_BUCKETS_PER_SOURCE_GROUP 32

	// in how many buckets for entries with new addresses a single address may occur
	#define ADDRMAN_NEW_BUCKETS_PER_ADDRESS 4

	// how many entries in a bucket with tried addresses are inspected, when selecting one to replace
	#define ADDRMAN_TRIED_ENTRIES_INSPECT_ON_EVICT 4

	// how old addresses can maximally be
	#define ADDRMAN_HORIZON_DAYS 30

	// after how many failed attempts we give up on a new node
	#define ADDRMAN_RETRIES 3

	// how many successive failures are allowed ...
	#define ADDRMAN_MAX_FAILURES 10

	// ... in at least this many days
	#define ADDRMAN_MIN_FAIL_DAYS 7

	// the maximum percentage of nodes to return in a getaddr call
	#define ADDRMAN_GETADDR_MAX_PCT 23

	// the maximum number of nodes to return in a getaddr call
	#define ADDRMAN_GETADDR_MAX 2500

	/** Stochastical (IP) address manager */
	class CAddrMan
	{
	private:
	// critical section to protect the inner data structures
	mutable CCriticalSection cs;

	// secret key to randomize bucket select with
	std::vector<unsigned char> nKey;

	// last used nId
	int nIdCount;

	// table with information about all nIds
	std::map<int, CAddrInfo> mapInfo;

	// find an nId based on its network address
	std::map<CNetAddr, int> mapAddr;

	// randomly-ordered vector of all nIds
	std::vector<int> vRandom;

	// number of "tried" entries
	int nTried;

	// list of "tried" buckets
	std::vector<std::vector<int> > vvTried;

	// number of (unique) "new" entries
	int nNew;

	// list of "new" buckets
	std::vector<std::set<int> > vvNew;

	protected:

	// Find an entry.
	CAddrInfo* Find(const CNetAddr& addr, int *pnId = NULL);

	// find an entry, creating it if necessary.
	// nTime and nServices of found node is updated, if necessary.
	CAddrInfo* Create(const CAddress &addr, const CNetAddr &addrSource, int *pnId = NULL);

	// Swap two elements in vRandom.
	void SwapRandom(unsigned int nRandomPos1, unsigned int nRandomPos2);

	// Return position in given bucket to replace.
	int SelectTried(int nKBucket);

	// Remove an element from a "new" bucket.
	// This is the only place where actual deletes occur.
	// They are never deleted while in the "tried" table, only possibly evicted back to the "new" table.
	int ShrinkNew(int nUBucket);

	// Move an entry from the "new" table(s) to the "tried" table
	// @pre vvUnkown[nOrigin].count(nId) != 0
	void MakeTried(CAddrInfo& info, int nId, int nOrigin);

	// Mark an entry "good", possibly moving it from "new" to "tried".
	void Good_(const CService &addr, int64 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 addrinfos in vvNew
	// * all nTried addrinfos in vvTried
	// * for each bucket:
	// * number of elements
	// * for each element: index
	//
	// Notice that vvTried, mapAddr and vVector are never encoded explicitly;
	// they are instead reconstructed from the other information.
	//
	// vvNew is serialized, but only used if ADDRMAN_UNKOWN_BUCKET_COUNT didn't change,
	// otherwise it is reconstructed as well.
	//
	// This format is more complex, but significantly smaller (at most 1.5 MiB), and supports
	// changes to the ADDRMAN_ parameters without breaking the on-disk structure.
	{
	LOCK(cs);
	unsigned char nVersion = 0;
	READWRITE(nVersion);
	READWRITE(nKey);
	READWRITE(nNew);
	READWRITE(nTried);

	CAddrMan am = const_cast<CAddrMan>(this);
	if (fWrite)
	{
	int nUBuckets = ADDRMAN_NEW_BUCKET_COUNT;
	READWRITE(nUBuckets);
	std::map<int, int> mapUnkIds;
	int nIds = 0;
	for (std::map<int, CAddrInfo>::iterator it = am->mapInfo.begin(); it != am->mapInfo.end(); it++)
	{
	if (nIds == nNew) break; // this means nNew was wrong, oh ow
	mapUnkIds[(*it).first] = nIds;
	CAddrInfo &info = (*it).second;
	if (info.nRefCount)
	{
	READWRITE(info);
	nIds++;
	}
	}
	nIds = 0;
	for (std::map<int, CAddrInfo>::iterator it = am->mapInfo.begin(); it != am->mapInfo.end(); it++)
	{
	if (nIds == nTried) break; // this means nTried was wrong, oh ow
	CAddrInfo &info = (*it).second;
	if (info.fInTried)
	{
	READWRITE(info);
	nIds++;
	}
	}
	for (std::vector<std::set<int> >::iterator it = am->vvNew.begin(); it != am->vvNew.end(); it++)
	{
	const std::set<int> &vNew = (*it);
	int nSize = vNew.size();
	READWRITE(nSize);
	for (std::set<int>::iterator it2 = vNew.begin(); it2 != vNew.end(); it2++)
	{
	int nIndex = mapUnkIds[*it2];
	READWRITE(nIndex);
	}
	}
	} else {
	int nUBuckets = 0;
	READWRITE(nUBuckets);
	am->nIdCount = 0;
	am->mapInfo.clear();
	am->mapAddr.clear();
	am->vRandom.clear();
	am->vvTried = std::vector<std::vector<int> >(ADDRMAN_TRIED_BUCKET_COUNT, std::vector<int>(0));
	am->vvNew = std::vector<std::set<int> >(ADDRMAN_NEW_BUCKET_COUNT, std::set<int>());
	for (int n = 0; n < am->nNew; n++)
	{
	CAddrInfo &info = am->mapInfo[n];
	READWRITE(info);
	am->mapAddr[info] = n;
	info.nRandomPos = vRandom.size();
	am->vRandom.push_back(n);
	if (nUBuckets != ADDRMAN_NEW_BUCKET_COUNT)
	{
	am->vvNew[info.GetNewBucket(am->nKey)].insert(n);
	info.nRefCount++;
	}
	}
	am->nIdCount = am->nNew;
	int nLost = 0;
	for (int n = 0; n < am->nTried; n++)
	{
	CAddrInfo info;
	READWRITE(info);
	std::vector<int> &vTried = am->vvTried[info.GetTriedBucket(am->nKey)];
	if (vTried.size() < ADDRMAN_TRIED_BUCKET_SIZE)
	{
	info.nRandomPos = vRandom.size();
	info.fInTried = true;
	am->vRandom.push_back(am->nIdCount);
	am->mapInfo[am->nIdCount] = info;
	am->mapAddr[info] = am->nIdCount;
	vTried.push_back(am->nIdCount);
	am->nIdCount++;
	} else {
	nLost++;
	}
	}
	am->nTried -= nLost;
	for (int b = 0; b < nUBuckets; b++)
	{
	std::set<int> &vNew = am->vvNew[b];
	int nSize = 0;
	READWRITE(nSize);
	for (int n = 0; n < nSize; n++)
	{
	int nIndex = 0;
	READWRITE(nIndex);
	CAddrInfo &info = am->mapInfo[nIndex];
	if (nUBuckets == ADDRMAN_NEW_BUCKET_COUNT && info.nRefCount < ADDRMAN_NEW_BUCKETS_PER_ADDRESS)
	{
	info.nRefCount++;
	vNew.insert(nIndex);
	}
	}
	}
	}
	}
	});)

	CAddrMan() : vRandom(0), vvTried(ADDRMAN_TRIED_BUCKET_COUNT, std::vector<int>(0)), vvNew(ADDRMAN_NEW_BUCKET_COUNT, std::set<int>())
	{
	nKey.resize(32);
	RAND_bytes(&nKey[0], 32);

	nIdCount = 0;
	nTried = 0;
	nNew = 0;
	}

	// Return the number of (unique) addresses in all tables.
	int size()
	{
	return vRandom.size();
	}

	// Consistency check
	void Check()
	{
	#ifdef DEBUG_ADDRMAN
	{
	LOCK(cs);
	int err;
	if ((err=Check_()))
	LogPrintf("ADDRMAN CONSISTENCY CHECK FAILED!!! err=%i\n", err);
	}
	#endif
	}

	// Add a single address.
	bool Add(const CAddress &addr, const CNetAddr& source, int64 nTimePenalty = 0)
	{
	bool fRet = false;
	{
	LOCK(cs);
	Check();
	fRet \|= Add_(addr, source, nTimePenalty);
	Check();
	}
	if (fRet)
	LogPrint("addr", "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;
	{
	LOCK(cs);
	Check();
	for (std::vector<CAddress>::const_iterator it = vAddr.begin(); it != vAddr.end(); it++)
	nAdd += Add_(*it, source, nTimePenalty) ? 1 : 0;
	Check();
	}
	if (nAdd)
	LogPrint("addr", "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())
	{
	{
	LOCK(cs);
	Check();
	Good_(addr, nTime);
	Check();
	}
	}

	// Mark an entry as connection attempted to.
	void Attempt(const CService &addr, int64 nTime = GetAdjustedTime())
	{
	{
	LOCK(cs);
	Check();
	Attempt_(addr, nTime);
	Check();
	}
	}

	// Choose an address to connect to.
	// nUnkBias determines how much "new" entries are favored over "tried" ones (0-100).
	CAddress Select(int nUnkBias = 50)
	{
	CAddress addrRet;
	{
	LOCK(cs);
	Check();
	addrRet = Select_(nUnkBias);
	Check();
	}
	return addrRet;
	}

	// Return a bunch of addresses, selected at random.
	std::vector<CAddress> GetAddr()
	{
	Check();
	std::vector<CAddress> vAddr;
	{
	LOCK(cs);
	GetAddr_(vAddr);
	}
	Check();
	return vAddr;
	}

	// Mark an entry as currently-connected-to.
	void Connected(const CService &addr, int64 nTime = GetAdjustedTime())
	{
	{
	LOCK(cs);
	Check();
	Connected_(addr, nTime);
	Check();
	}
	}
	};

	#endif

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