addrman.cpp
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	// Copyright (c) 2012 Pieter Wuille
	// 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"
	#include "streams.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 = GetRandInt(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 && (GetRandInt(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 \|\| GetRandInt(2) == 0))) {
	// use a tried node
	double fChanceFactor = 1.0;
	while (1) {
	int nKBucket = GetRandInt(ADDRMAN_TRIED_BUCKET_COUNT);
	int nKBucketPos = GetRandInt(ADDRMAN_BUCKET_SIZE);
	while (vvTried[nKBucket][nKBucketPos] == -1) {
	nKBucket = (nKBucket + insecure_rand()) % ADDRMAN_TRIED_BUCKET_COUNT;
	nKBucketPos = (nKBucketPos + insecure_rand()) % ADDRMAN_BUCKET_SIZE;
	}
	int nId = vvTried[nKBucket][nKBucketPos];
	assert(mapInfo.count(nId) == 1);
	CAddrInfo& info = mapInfo[nId];
	if (GetRandInt(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 = GetRandInt(ADDRMAN_NEW_BUCKET_COUNT);
	int nUBucketPos = GetRandInt(ADDRMAN_BUCKET_SIZE);
	while (vvNew[nUBucket][nUBucketPos] == -1) {
	nUBucket = (nUBucket + insecure_rand()) % ADDRMAN_NEW_BUCKET_COUNT;
	nUBucketPos = (nUBucketPos + insecure_rand()) % ADDRMAN_BUCKET_SIZE;
	}
	int nId = vvNew[nUBucket][nUBucketPos];
	assert(mapInfo.count(nId) == 1);
	CAddrInfo& info = mapInfo[nId];
	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 < 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 = GetRandInt(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;
	}

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