net_processing.cpp

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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2016 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include "net_processing.h"

#include "alert.h"
#include "addrman.h"
#include "arith_uint256.h"
#include "chainparams.h"
#include "consensus/validation.h"
#include "hash.h"
#include "init.h"
#include "validation.h"
#include "merkleblock.h"
#include "net.h"
#include "netbase.h"
#include "policy/fees.h"
#include "policy/policy.h"
#include "primitives/block.h"
#include "primitives/transaction.h"
#include "random.h"
#include "tinyformat.h"
#include "txmempool.h"
#include "ui_interface.h"
#include "util.h"
#include "utilmoneystr.h"
#include "utilstrencodings.h"
#include "validationinterface.h"

#include "spork.h"
#include "governance.h"
#include "instantx.h"
#include "masternode-payments.h"
#include "masternode-sync.h"
#include "masternodeman.h"
#include "privatesend-client.h"
#include "privatesend-server.h"

#include <boost/thread.hpp>

using namespace std;

#if defined(NDEBUG)
# error "Dash Core cannot be compiled without assertions."
#endif

int64_t nTimeBestReceived = 0; // Used only to inform the wallet of when we last received a block

struct COrphanTx {
    CTransaction tx;
    NodeId fromPeer;
};
map<uint256, COrphanTx> mapOrphanTransactions GUARDED_BY(cs_main);
map<uint256, set<uint256> > mapOrphanTransactionsByPrev GUARDED_BY(cs_main);;
void EraseOrphansFor(NodeId peer) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

// Internal stuff
namespace {
    int nSyncStarted = 0;

    map<uint256, NodeId> mapBlockSource;

    boost::scoped_ptr<CRollingBloomFilter> recentRejects;
    uint256 hashRecentRejectsChainTip;

    struct QueuedBlock {
        uint256 hash;
        CBlockIndex* pindex;     
        bool fValidatedHeaders;  
    };
    map<uint256, pair<NodeId, list<QueuedBlock>::iterator> > mapBlocksInFlight;

    int nPreferredDownload = 0;


    int nPeersWithValidatedDownloads = 0;
} // anon namespace

//
// Registration of network node signals.
//

namespace {

struct CBlockReject {
    unsigned char chRejectCode;
    string strRejectReason;
    uint256 hashBlock;
};

struct CNodeState {
    const CService address;
    bool fCurrentlyConnected;
    int nMisbehavior;
    bool fShouldBan;
    const std::string name;
    std::vector<CBlockReject> rejects;
    CBlockIndex *pindexBestKnownBlock;
    uint256 hashLastUnknownBlock;
    CBlockIndex *pindexLastCommonBlock;
    CBlockIndex *pindexBestHeaderSent;
    bool fSyncStarted;
    int64_t nHeadersSyncTimeout;
    int64_t nStallingSince;
    list<QueuedBlock> vBlocksInFlight;
    int64_t nDownloadingSince;
    int nBlocksInFlight;
    int nBlocksInFlightValidHeaders;
    bool fPreferredDownload;
    bool fPreferHeaders;

    CNodeState(CAddress addrIn, std::string addrNameIn) : address(addrIn), name(addrNameIn) {
        fCurrentlyConnected = false;
        nMisbehavior = 0;
        fShouldBan = false;
        pindexBestKnownBlock = NULL;
        hashLastUnknownBlock.SetNull();
        pindexLastCommonBlock = NULL;
        pindexBestHeaderSent = NULL;
        fSyncStarted = false;
        nHeadersSyncTimeout = 0;
        nStallingSince = 0;
        nDownloadingSince = 0;
        nBlocksInFlight = 0;
        nBlocksInFlightValidHeaders = 0;
        fPreferredDownload = false;
        fPreferHeaders = false;
    }
};

map<NodeId, CNodeState> mapNodeState;

// Requires cs_main.
CNodeState *State(NodeId pnode) {
    map<NodeId, CNodeState>::iterator it = mapNodeState.find(pnode);
    if (it == mapNodeState.end())
        return NULL;
    return &it->second;
}

void UpdatePreferredDownload(CNode* node, CNodeState* state)
{
    nPreferredDownload -= state->fPreferredDownload;

    // Whether this node should be marked as a preferred download node.
    state->fPreferredDownload = (!node->fInbound || node->fWhitelisted) && !node->fOneShot && !node->fClient;

    nPreferredDownload += state->fPreferredDownload;
}

void PushNodeVersion(CNode *pnode, CConnman& connman, int64_t nTime)
{
    ServiceFlags nLocalNodeServices = pnode->GetLocalServices();
    uint64_t nonce = pnode->GetLocalNonce();
    int nNodeStartingHeight = pnode->GetMyStartingHeight();
    NodeId nodeid = pnode->GetId();
    CAddress addr = pnode->addr;

    CAddress addrYou = (addr.IsRoutable() && !IsProxy(addr) ? addr : CAddress(CService(), addr.nServices));
    CAddress addrMe = CAddress(CService(), nLocalNodeServices);

    connman.PushMessageWithVersion(pnode, INIT_PROTO_VERSION, NetMsgType::VERSION, PROTOCOL_VERSION, (uint64_t)nLocalNodeServices, nTime, addrYou, addrMe,
            nonce, strSubVersion, nNodeStartingHeight, ::fRelayTxes);

    if (fLogIPs)
        LogPrint("net", "send version message: version %d, blocks=%d, us=%s, them=%s, peer=%d\n", PROTOCOL_VERSION, nNodeStartingHeight, addrMe.ToString(), addrYou.ToString(), nodeid);
    else
        LogPrint("net", "send version message: version %d, blocks=%d, us=%s, peer=%d\n", PROTOCOL_VERSION, nNodeStartingHeight, addrMe.ToString(), nodeid);
}

void InitializeNode(CNode *pnode, CConnman& connman) {
    CAddress addr = pnode->addr;
    std::string addrName = pnode->addrName;
    NodeId nodeid = pnode->GetId();
    {
        LOCK(cs_main);
        mapNodeState.emplace_hint(mapNodeState.end(), std::piecewise_construct, std::forward_as_tuple(nodeid), std::forward_as_tuple(addr, std::move(addrName)));
    }
    if(!pnode->fInbound)
        PushNodeVersion(pnode, connman, GetTime());
}

void FinalizeNode(NodeId nodeid, bool& fUpdateConnectionTime) {
    fUpdateConnectionTime = false;
    LOCK(cs_main);
    CNodeState *state = State(nodeid);

    if (state->fSyncStarted)
        nSyncStarted--;

    if (state->nMisbehavior == 0 && state->fCurrentlyConnected) {
        fUpdateConnectionTime = true;
    }

    BOOST_FOREACH(const QueuedBlock& entry, state->vBlocksInFlight) {
        mapBlocksInFlight.erase(entry.hash);
    }
    EraseOrphansFor(nodeid);
    nPreferredDownload -= state->fPreferredDownload;
    nPeersWithValidatedDownloads -= (state->nBlocksInFlightValidHeaders != 0);
    assert(nPeersWithValidatedDownloads >= 0);

    mapNodeState.erase(nodeid);

    if (mapNodeState.empty()) {
        // Do a consistency check after the last peer is removed.
        assert(mapBlocksInFlight.empty());
        assert(nPreferredDownload == 0);
        assert(nPeersWithValidatedDownloads == 0);
    }
}

// Requires cs_main.
// Returns a bool indicating whether we requested this block.
bool MarkBlockAsReceived(const uint256& hash) {
    map<uint256, pair<NodeId, list<QueuedBlock>::iterator> >::iterator itInFlight = mapBlocksInFlight.find(hash);
    if (itInFlight != mapBlocksInFlight.end()) {
        CNodeState *state = State(itInFlight->second.first);
        state->nBlocksInFlightValidHeaders -= itInFlight->second.second->fValidatedHeaders;
        if (state->nBlocksInFlightValidHeaders == 0 && itInFlight->second.second->fValidatedHeaders) {
            // Last validated block on the queue was received.
            nPeersWithValidatedDownloads--;
        }
        if (state->vBlocksInFlight.begin() == itInFlight->second.second) {
            // First block on the queue was received, update the start download time for the next one
            state->nDownloadingSince = std::max(state->nDownloadingSince, GetTimeMicros());
        }
        state->vBlocksInFlight.erase(itInFlight->second.second);
        state->nBlocksInFlight--;
        state->nStallingSince = 0;
        mapBlocksInFlight.erase(itInFlight);
        return true;
    }
    return false;
}

// Requires cs_main.
void MarkBlockAsInFlight(NodeId nodeid, const uint256& hash, const Consensus::Params& consensusParams, CBlockIndex *pindex = NULL) {
    CNodeState *state = State(nodeid);
    assert(state != NULL);

    // Make sure it's not listed somewhere already.
    MarkBlockAsReceived(hash);

    QueuedBlock newentry = {hash, pindex, pindex != NULL};
    list<QueuedBlock>::iterator it = state->vBlocksInFlight.insert(state->vBlocksInFlight.end(), newentry);
    state->nBlocksInFlight++;
    state->nBlocksInFlightValidHeaders += newentry.fValidatedHeaders;
    if (state->nBlocksInFlight == 1) {
        // We're starting a block download (batch) from this peer.
        state->nDownloadingSince = GetTimeMicros();
    }
    if (state->nBlocksInFlightValidHeaders == 1 && pindex != NULL) {
        nPeersWithValidatedDownloads++;
    }
    mapBlocksInFlight[hash] = std::make_pair(nodeid, it);
}

void ProcessBlockAvailability(NodeId nodeid) {
    CNodeState *state = State(nodeid);
    assert(state != NULL);

    if (!state->hashLastUnknownBlock.IsNull()) {
        BlockMap::iterator itOld = mapBlockIndex.find(state->hashLastUnknownBlock);
        if (itOld != mapBlockIndex.end() && itOld->second->nChainWork > 0) {
            if (state->pindexBestKnownBlock == NULL || itOld->second->nChainWork >= state->pindexBestKnownBlock->nChainWork)
                state->pindexBestKnownBlock = itOld->second;
            state->hashLastUnknownBlock.SetNull();
        }
    }
}

void UpdateBlockAvailability(NodeId nodeid, const uint256 &hash) {
    CNodeState *state = State(nodeid);
    assert(state != NULL);

    ProcessBlockAvailability(nodeid);

    BlockMap::iterator it = mapBlockIndex.find(hash);
    if (it != mapBlockIndex.end() && it->second->nChainWork > 0) {
        // An actually better block was announced.
        if (state->pindexBestKnownBlock == NULL || it->second->nChainWork >= state->pindexBestKnownBlock->nChainWork)
            state->pindexBestKnownBlock = it->second;
    } else {
        // An unknown block was announced; just assume that the latest one is the best one.
        state->hashLastUnknownBlock = hash;
    }
}

// Requires cs_main
bool CanDirectFetch(const Consensus::Params &consensusParams)
{
    return chainActive.Tip()->GetBlockTime() > GetAdjustedTime() - consensusParams.nPowTargetSpacing * 20;
}

// Requires cs_main
bool PeerHasHeader(CNodeState *state, CBlockIndex *pindex)
{
    if (state->pindexBestKnownBlock && pindex == state->pindexBestKnownBlock->GetAncestor(pindex->nHeight))
        return true;
    if (state->pindexBestHeaderSent && pindex == state->pindexBestHeaderSent->GetAncestor(pindex->nHeight))
        return true;
    return false;
}

CBlockIndex* LastCommonAncestor(CBlockIndex* pa, CBlockIndex* pb) {
    if (pa->nHeight > pb->nHeight) {
        pa = pa->GetAncestor(pb->nHeight);
    } else if (pb->nHeight > pa->nHeight) {
        pb = pb->GetAncestor(pa->nHeight);
    }

    while (pa != pb && pa && pb) {
        pa = pa->pprev;
        pb = pb->pprev;
    }

    // Eventually all chain branches meet at the genesis block.
    assert(pa == pb);
    return pa;
}

void FindNextBlocksToDownload(NodeId nodeid, unsigned int count, std::vector<CBlockIndex*>& vBlocks, NodeId& nodeStaller, const Consensus::Params& consensusParams) {
    if (count == 0)
        return;

    vBlocks.reserve(vBlocks.size() + count);
    CNodeState *state = State(nodeid);
    assert(state != NULL);

    // Make sure pindexBestKnownBlock is up to date, we'll need it.
    ProcessBlockAvailability(nodeid);

    if (state->pindexBestKnownBlock == NULL || state->pindexBestKnownBlock->nChainWork < chainActive.Tip()->nChainWork || state->pindexBestKnownBlock->nChainWork < UintToArith256(consensusParams.nMinimumChainWork)) {
        // This peer has nothing interesting.
        return;
    }

    if (state->pindexLastCommonBlock == NULL) {
        // Bootstrap quickly by guessing a parent of our best tip is the forking point.
        // Guessing wrong in either direction is not a problem.
        state->pindexLastCommonBlock = chainActive[std::min(state->pindexBestKnownBlock->nHeight, chainActive.Height())];
    }

    // If the peer reorganized, our previous pindexLastCommonBlock may not be an ancestor
    // of its current tip anymore. Go back enough to fix that.
    state->pindexLastCommonBlock = LastCommonAncestor(state->pindexLastCommonBlock, state->pindexBestKnownBlock);
    if (state->pindexLastCommonBlock == state->pindexBestKnownBlock)
        return;

    std::vector<CBlockIndex*> vToFetch;
    CBlockIndex *pindexWalk = state->pindexLastCommonBlock;
    // Never fetch further than the best block we know the peer has, or more than BLOCK_DOWNLOAD_WINDOW + 1 beyond the last
    // linked block we have in common with this peer. The +1 is so we can detect stalling, namely if we would be able to
    // download that next block if the window were 1 larger.
    int nWindowEnd = state->pindexLastCommonBlock->nHeight + BLOCK_DOWNLOAD_WINDOW;
    int nMaxHeight = std::min<int>(state->pindexBestKnownBlock->nHeight, nWindowEnd + 1);
    NodeId waitingfor = -1;
    while (pindexWalk->nHeight < nMaxHeight) {
        // Read up to 128 (or more, if more blocks than that are needed) successors of pindexWalk (towards
        // pindexBestKnownBlock) into vToFetch. We fetch 128, because CBlockIndex::GetAncestor may be as expensive
        // as iterating over ~100 CBlockIndex* entries anyway.
        int nToFetch = std::min(nMaxHeight - pindexWalk->nHeight, std::max<int>(count - vBlocks.size(), 128));
        vToFetch.resize(nToFetch);
        pindexWalk = state->pindexBestKnownBlock->GetAncestor(pindexWalk->nHeight + nToFetch);
        vToFetch[nToFetch - 1] = pindexWalk;
        for (unsigned int i = nToFetch - 1; i > 0; i--) {
            vToFetch[i - 1] = vToFetch[i]->pprev;
        }

        // Iterate over those blocks in vToFetch (in forward direction), adding the ones that
        // are not yet downloaded and not in flight to vBlocks. In the mean time, update
        // pindexLastCommonBlock as long as all ancestors are already downloaded, or if it's
        // already part of our chain (and therefore don't need it even if pruned).
        BOOST_FOREACH(CBlockIndex* pindex, vToFetch) {
            if (!pindex->IsValid(BLOCK_VALID_TREE)) {
                // We consider the chain that this peer is on invalid.
                return;
            }
            if (pindex->nStatus & BLOCK_HAVE_DATA || chainActive.Contains(pindex)) {
                if (pindex->nChainTx)
                    state->pindexLastCommonBlock = pindex;
            } else if (mapBlocksInFlight.count(pindex->GetBlockHash()) == 0) {
                // The block is not already downloaded, and not yet in flight.
                if (pindex->nHeight > nWindowEnd) {
                    // We reached the end of the window.
                    if (vBlocks.size() == 0 && waitingfor != nodeid) {
                        // We aren't able to fetch anything, but we would be if the download window was one larger.
                        nodeStaller = waitingfor;
                    }
                    return;
                }
                vBlocks.push_back(pindex);
                if (vBlocks.size() == count) {
                    return;
                }
            } else if (waitingfor == -1) {
                // This is the first already-in-flight block.
                waitingfor = mapBlocksInFlight[pindex->GetBlockHash()].first;
            }
        }
    }
}

} // anon namespace

bool GetNodeStateStats(NodeId nodeid, CNodeStateStats &stats) {
    LOCK(cs_main);
    CNodeState *state = State(nodeid);
    if (state == NULL)
        return false;
    stats.nMisbehavior = state->nMisbehavior;
    stats.nSyncHeight = state->pindexBestKnownBlock ? state->pindexBestKnownBlock->nHeight : -1;
    stats.nCommonHeight = state->pindexLastCommonBlock ? state->pindexLastCommonBlock->nHeight : -1;
    BOOST_FOREACH(const QueuedBlock& queue, state->vBlocksInFlight) {
        if (queue.pindex)
            stats.vHeightInFlight.push_back(queue.pindex->nHeight);
    }
    return true;
}

void RegisterNodeSignals(CNodeSignals& nodeSignals)
{
    nodeSignals.ProcessMessages.connect(&ProcessMessages);
    nodeSignals.SendMessages.connect(&SendMessages);
    nodeSignals.InitializeNode.connect(&InitializeNode);
    nodeSignals.FinalizeNode.connect(&FinalizeNode);
}

void UnregisterNodeSignals(CNodeSignals& nodeSignals)
{
    nodeSignals.ProcessMessages.disconnect(&ProcessMessages);
    nodeSignals.SendMessages.disconnect(&SendMessages);
    nodeSignals.InitializeNode.disconnect(&InitializeNode);
    nodeSignals.FinalizeNode.disconnect(&FinalizeNode);
}

//
// mapOrphanTransactions
//

bool AddOrphanTx(const CTransaction& tx, NodeId peer) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
{
    uint256 hash = tx.GetHash();
    if (mapOrphanTransactions.count(hash))
        return false;

    // Ignore big transactions, to avoid a
    // send-big-orphans memory exhaustion attack. If a peer has a legitimate
    // large transaction with a missing parent then we assume
    // it will rebroadcast it later, after the parent transaction(s)
    // have been mined or received.
    // 10,000 orphans, each of which is at most 5,000 bytes big is
    // at most 500 megabytes of orphans:
    unsigned int sz = tx.GetSerializeSize(SER_NETWORK, CTransaction::CURRENT_VERSION);
    if (sz > 5000)
    {
        LogPrint("mempool", "ignoring large orphan tx (size: %u, hash: %s)\n", sz, hash.ToString());
        return false;
    }

    mapOrphanTransactions[hash].tx = tx;
    mapOrphanTransactions[hash].fromPeer = peer;
    BOOST_FOREACH(const CTxIn& txin, tx.vin)
        mapOrphanTransactionsByPrev[txin.prevout.hash].insert(hash);

    LogPrint("mempool", "stored orphan tx %s (mapsz %u prevsz %u)\n", hash.ToString(),
             mapOrphanTransactions.size(), mapOrphanTransactionsByPrev.size());
    return true;
}

void static EraseOrphanTx(uint256 hash) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
{
    map<uint256, COrphanTx>::iterator it = mapOrphanTransactions.find(hash);
    if (it == mapOrphanTransactions.end())
        return;
    BOOST_FOREACH(const CTxIn& txin, it->second.tx.vin)
    {
        map<uint256, set<uint256> >::iterator itPrev = mapOrphanTransactionsByPrev.find(txin.prevout.hash);
        if (itPrev == mapOrphanTransactionsByPrev.end())
            continue;
        itPrev->second.erase(hash);
        if (itPrev->second.empty())
            mapOrphanTransactionsByPrev.erase(itPrev);
    }
    mapOrphanTransactions.erase(it);
}

void EraseOrphansFor(NodeId peer)
{
    int nErased = 0;
    map<uint256, COrphanTx>::iterator iter = mapOrphanTransactions.begin();
    while (iter != mapOrphanTransactions.end())
    {
        map<uint256, COrphanTx>::iterator maybeErase = iter++; // increment to avoid iterator becoming invalid
        if (maybeErase->second.fromPeer == peer)
        {
            EraseOrphanTx(maybeErase->second.tx.GetHash());
            ++nErased;
        }
    }
    if (nErased > 0) LogPrint("mempool", "Erased %d orphan tx from peer %d\n", nErased, peer);
}


unsigned int LimitOrphanTxSize(unsigned int nMaxOrphans) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
{
    unsigned int nEvicted = 0;
    while (mapOrphanTransactions.size() > nMaxOrphans)
    {
        // Evict a random orphan:
        uint256 randomhash = GetRandHash();
        map<uint256, COrphanTx>::iterator it = mapOrphanTransactions.lower_bound(randomhash);
        if (it == mapOrphanTransactions.end())
            it = mapOrphanTransactions.begin();
        EraseOrphanTx(it->first);
        ++nEvicted;
    }
    return nEvicted;
}

// Requires cs_main.
void Misbehaving(NodeId pnode, int howmuch)
{
    if (howmuch == 0)
        return;

    CNodeState *state = State(pnode);
    if (state == NULL)
        return;

    state->nMisbehavior += howmuch;
    int banscore = GetArg("-banscore", DEFAULT_BANSCORE_THRESHOLD);
    if (state->nMisbehavior >= banscore && state->nMisbehavior - howmuch < banscore)
    {
        LogPrintf("%s: %s (%d -> %d) BAN THRESHOLD EXCEEDED\n", __func__, state->name, state->nMisbehavior-howmuch, state->nMisbehavior);
        state->fShouldBan = true;
    } else
        LogPrintf("%s: %s (%d -> %d)\n", __func__, state->name, state->nMisbehavior-howmuch, state->nMisbehavior);
}








//
// blockchain -> download logic notification
//

PeerLogicValidation::PeerLogicValidation(CConnman* connmanIn) : connman(connmanIn) {
    // Initialize global variables that cannot be constructed at startup.
    recentRejects.reset(new CRollingBloomFilter(120000, 0.000001));
}

void PeerLogicValidation::UpdatedBlockTip(const CBlockIndex *pindexNew, const CBlockIndex *pindexFork, bool fInitialDownload) {
    const int nNewHeight = pindexNew->nHeight;
    connman->SetBestHeight(nNewHeight);

    if (!fInitialDownload) {
        // Find the hashes of all blocks that weren't previously in the best chain.
        std::vector<uint256> vHashes;
        const CBlockIndex *pindexToAnnounce = pindexNew;
        while (pindexToAnnounce != pindexFork) {
            vHashes.push_back(pindexToAnnounce->GetBlockHash());
            pindexToAnnounce = pindexToAnnounce->pprev;
            if (vHashes.size() == MAX_BLOCKS_TO_ANNOUNCE) {
                // Limit announcements in case of a huge reorganization.
                // Rely on the peer's synchronization mechanism in that case.
                break;
            }
        }
        // Relay inventory, but don't relay old inventory during initial block download.
        connman->ForEachNode([nNewHeight, &vHashes](CNode* pnode) {
            if (nNewHeight > (pnode->nStartingHeight != -1 ? pnode->nStartingHeight - 2000 : 0)) {
                BOOST_REVERSE_FOREACH(const uint256& hash, vHashes) {
                    pnode->PushBlockHash(hash);
                }
            }
        });
    }

    nTimeBestReceived = GetTime();
}

void PeerLogicValidation::BlockChecked(const CBlock& block, const CValidationState& state) {
    LOCK(cs_main);

    const uint256 hash(block.GetHash());
    std::map<uint256, NodeId>::iterator it = mapBlockSource.find(hash);

    int nDoS = 0;
    if (state.IsInvalid(nDoS)) {
        if (it != mapBlockSource.end() && State(it->second)) {
            assert (state.GetRejectCode() < REJECT_INTERNAL); // Blocks are never rejected with internal reject codes
            CBlockReject reject = {(unsigned char)state.GetRejectCode(), state.GetRejectReason().substr(0, MAX_REJECT_MESSAGE_LENGTH), hash};
            State(it->second)->rejects.push_back(reject);
            if (nDoS > 0)
                Misbehaving(it->second, nDoS);
        }
    }
    if (it != mapBlockSource.end())
        mapBlockSource.erase(it);
}

//
// Messages
//


bool static AlreadyHave(const CInv& inv) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
{
    switch (inv.type)
    {
    case MSG_TX:
        {
            assert(recentRejects);
            if (chainActive.Tip()->GetBlockHash() != hashRecentRejectsChainTip)
            {
                // If the chain tip has changed previously rejected transactions
                // might be now valid, e.g. due to a nLockTime'd tx becoming valid,
                // or a double-spend. Reset the rejects filter and give those
                // txs a second chance.
                hashRecentRejectsChainTip = chainActive.Tip()->GetBlockHash();
                recentRejects->reset();
            }

            return recentRejects->contains(inv.hash) ||
                   mempool.exists(inv.hash) ||
                   mapOrphanTransactions.count(inv.hash) ||
                   pcoinsTip->HaveCoins(inv.hash);
        }

    case MSG_BLOCK:
        return mapBlockIndex.count(inv.hash);

    /* 
        Dash Related Inventory Messages

        --

        We shouldn't update the sync times for each of the messages when we already have it. 
        We're going to be asking many nodes upfront for the full inventory list, so we'll get duplicates of these.
        We want to only update the time on new hits, so that we can time out appropriately if needed.
    */
    case MSG_TXLOCK_REQUEST:
        return instantsend.AlreadyHave(inv.hash);

    case MSG_TXLOCK_VOTE:
        return instantsend.AlreadyHave(inv.hash);

    case MSG_SPORK:
        return mapSporks.count(inv.hash);

    case MSG_MASTERNODE_PAYMENT_VOTE:
        return mnpayments.mapMasternodePaymentVotes.count(inv.hash);

    case MSG_MASTERNODE_PAYMENT_BLOCK:
        {
            BlockMap::iterator mi = mapBlockIndex.find(inv.hash);
            return mi != mapBlockIndex.end() && mnpayments.mapMasternodeBlocks.find(mi->second->nHeight) != mnpayments.mapMasternodeBlocks.end();
        }

    case MSG_MASTERNODE_ANNOUNCE:
        return mnodeman.mapSeenMasternodeBroadcast.count(inv.hash) && !mnodeman.IsMnbRecoveryRequested(inv.hash);

    case MSG_MASTERNODE_PING:
        return mnodeman.mapSeenMasternodePing.count(inv.hash);

    case MSG_DSTX: {
        return static_cast<bool>(CPrivateSend::GetDSTX(inv.hash));
    }

    case MSG_GOVERNANCE_OBJECT:
    case MSG_GOVERNANCE_OBJECT_VOTE:
        return ! governance.ConfirmInventoryRequest(inv);

    case MSG_MASTERNODE_VERIFY:
        return mnodeman.mapSeenMasternodeVerification.count(inv.hash);
    }

    // Don't know what it is, just say we already got one
    return true;
}

static void RelayAddress(const CAddress& addr, bool fReachable, CConnman& connman)
{
    int nRelayNodes = fReachable ? 2 : 1; // limited relaying of addresses outside our network(s)

    // Relay to a limited number of other nodes
    // Use deterministic randomness to send to the same nodes for 24 hours
    // at a time so the addrKnowns of the chosen nodes prevent repeats
    static uint256 hashSalt;
    if (hashSalt.IsNull())
        hashSalt = GetRandHash();
    uint64_t hashAddr = addr.GetHash();
    uint256 hashRand = ArithToUint256(UintToArith256(hashSalt) ^ (hashAddr<<32) ^ ((GetTime()+hashAddr)/(24*60*60)));
    hashRand = Hash(BEGIN(hashRand), END(hashRand));
    std::multimap<uint256, CNode*> mapMix;

    auto sortfunc = [&mapMix, &hashRand](CNode* pnode) {
        if (pnode->nVersion >= CADDR_TIME_VERSION) {
            unsigned int nPointer;
            memcpy(&nPointer, &pnode, sizeof(nPointer));
            uint256 hashKey = ArithToUint256(UintToArith256(hashRand) ^ nPointer);
            hashKey = Hash(BEGIN(hashKey), END(hashKey));
            mapMix.emplace(hashKey, pnode);
        }
    };

    auto pushfunc = [&addr, &mapMix, &nRelayNodes] {
        for (auto mi = mapMix.begin(); mi != mapMix.end() && nRelayNodes-- > 0; ++mi)
            mi->second->PushAddress(addr);
    };

    connman.ForEachNodeThen(std::move(sortfunc), std::move(pushfunc));
}

void static ProcessGetData(CNode* pfrom, const Consensus::Params& consensusParams, CConnman& connman, std::atomic<bool>& interruptMsgProc)
{
    std::deque<CInv>::iterator it = pfrom->vRecvGetData.begin();
    vector<CInv> vNotFound;

    LOCK(cs_main);

    while (it != pfrom->vRecvGetData.end()) {
        // Don't bother if send buffer is too full to respond anyway
        if (pfrom->fPauseSend)
            break;

        const CInv &inv = *it;
        LogPrint("net", "ProcessGetData -- inv = %s\n", inv.ToString());
        {
            if (interruptMsgProc)
                return;

            it++;

            if (inv.type == MSG_BLOCK || inv.type == MSG_FILTERED_BLOCK)
            {
                bool send = false;
                BlockMap::iterator mi = mapBlockIndex.find(inv.hash);
                if (mi != mapBlockIndex.end())
                {
                    if (chainActive.Contains(mi->second)) {
                        send = true;
                    } else {
                        static const int nOneMonth = 30 * 24 * 60 * 60;
                        // To prevent fingerprinting attacks, only send blocks outside of the active
                        // chain if they are valid, and no more than a month older (both in time, and in
                        // best equivalent proof of work) than the best header chain we know about.
                        send = mi->second->IsValid(BLOCK_VALID_SCRIPTS) && (pindexBestHeader != NULL) &&
                            (pindexBestHeader->GetBlockTime() - mi->second->GetBlockTime() < nOneMonth) &&
                            (GetBlockProofEquivalentTime(*pindexBestHeader, *mi->second, *pindexBestHeader, consensusParams) < nOneMonth);
                        if (!send) {
                            LogPrintf("%s: ignoring request from peer=%i for old block that isn't in the main chain\n", __func__, pfrom->GetId());
                        }
                    }
                }
                // disconnect node in case we have reached the outbound limit for serving historical blocks
                // never disconnect whitelisted nodes
                static const int nOneWeek = 7 * 24 * 60 * 60; // assume > 1 week = historical
                if (send && connman.OutboundTargetReached(true) && ( ((pindexBestHeader != NULL) && (pindexBestHeader->GetBlockTime() - mi->second->GetBlockTime() > nOneWeek)) || inv.type == MSG_FILTERED_BLOCK) && !pfrom->fWhitelisted)
                {
                    LogPrint("net", "historical block serving limit reached, disconnect peer=%d\n", pfrom->GetId());

                    //disconnect node
                    pfrom->fDisconnect = true;
                    send = false;
                }
                // Pruned nodes may have deleted the block, so check whether
                // it's available before trying to send.
                if (send && (mi->second->nStatus & BLOCK_HAVE_DATA)) {
                    // Send block from disk
                    CBlock block;
                    if (!ReadBlockFromDisk(block, (*mi).second, consensusParams))
                        assert(!"cannot load block from disk");
                    if (inv.type == MSG_BLOCK)
                        connman.PushMessage(pfrom, NetMsgType::BLOCK, block);
                    else // MSG_FILTERED_BLOCK)
                    {
                        LOCK(pfrom->cs_filter);
                        if (pfrom->pfilter)
                        {
                            CMerkleBlock merkleBlock(block, *pfrom->pfilter);
                            connman.PushMessage(pfrom, NetMsgType::MERKLEBLOCK, merkleBlock);
                            // CMerkleBlock just contains hashes, so also push any transactions in the block the client did not see
                            // This avoids hurting performance by pointlessly requiring a round-trip
                            // Note that there is currently no way for a node to request any single transactions we didn't send here -
                            // they must either disconnect and retry or request the full block.
                            // Thus, the protocol spec specified allows for us to provide duplicate txn here,
                            // however we MUST always provide at least what the remote peer needs
                            typedef std::pair<unsigned int, uint256> PairType;
                            BOOST_FOREACH(PairType& pair, merkleBlock.vMatchedTxn)
                                connman.PushMessage(pfrom, NetMsgType::TX, block.vtx[pair.first]);
                        }
                        // else
                            // no response
                    }

                    // Trigger the peer node to send a getblocks request for the next batch of inventory
                    if (inv.hash == pfrom->hashContinue)
                    {
                        // Bypass PushInventory, this must send even if redundant,
                        // and we want it right after the last block so they don't
                        // wait for other stuff first.
                        vector<CInv> vInv;
                        vInv.push_back(CInv(MSG_BLOCK, chainActive.Tip()->GetBlockHash()));
                        connman.PushMessage(pfrom, NetMsgType::INV, vInv);
                        pfrom->hashContinue.SetNull();
                    }
                }
            }
            else if (inv.IsKnownType())
            {
                // Send stream from relay memory
                bool pushed = false;
                {
                    CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
                    {
                        LOCK(cs_mapRelay);
                        map<CInv, CDataStream>::iterator mi = mapRelay.find(inv);
                        if (mi != mapRelay.end()) {
                            ss += (*mi).second;
                            pushed = true;
                        }
                    }
                    if(pushed)
                        connman.PushMessage(pfrom, inv.GetCommand(), ss);
                }

                if (!pushed && inv.type == MSG_TX) {
                    CTransaction tx;
                    if (mempool.lookup(inv.hash, tx)) {
                        CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
                        ss.reserve(1000);
                        ss << tx;
                        connman.PushMessage(pfrom, NetMsgType::TX, ss);
                        pushed = true;
                    }
                }

                if (!pushed && inv.type == MSG_TXLOCK_REQUEST) {
                    CTxLockRequest txLockRequest;
                    if(instantsend.GetTxLockRequest(inv.hash, txLockRequest)) {
                        CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
                        ss.reserve(1000);
                        ss << txLockRequest;
                        connman.PushMessage(pfrom, NetMsgType::TXLOCKREQUEST, ss);
                        pushed = true;
                    }
                }

                if (!pushed && inv.type == MSG_TXLOCK_VOTE) {
                    CTxLockVote vote;
                    if(instantsend.GetTxLockVote(inv.hash, vote)) {
                        CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
                        ss.reserve(1000);
                        ss << vote;
                        connman.PushMessage(pfrom, NetMsgType::TXLOCKVOTE, ss);
                        pushed = true;
                    }
                }

                if (!pushed && inv.type == MSG_SPORK) {
                    if(mapSporks.count(inv.hash)) {
                        CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
                        ss.reserve(1000);
                        ss << mapSporks[inv.hash];
                        connman.PushMessage(pfrom, NetMsgType::SPORK, ss);
                        pushed = true;
                    }
                }

                if (!pushed && inv.type == MSG_MASTERNODE_PAYMENT_VOTE) {
                    if(mnpayments.HasVerifiedPaymentVote(inv.hash)) {
                        CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
                        ss.reserve(1000);
                        ss << mnpayments.mapMasternodePaymentVotes[inv.hash];
                        connman.PushMessage(pfrom, NetMsgType::MASTERNODEPAYMENTVOTE, ss);
                        pushed = true;
                    }
                }

                if (!pushed && inv.type == MSG_MASTERNODE_PAYMENT_BLOCK) {
                    BlockMap::iterator mi = mapBlockIndex.find(inv.hash);
                    LOCK(cs_mapMasternodeBlocks);
                    if (mi != mapBlockIndex.end() && mnpayments.mapMasternodeBlocks.count(mi->second->nHeight)) {
                        BOOST_FOREACH(CMasternodePayee& payee, mnpayments.mapMasternodeBlocks[mi->second->nHeight].vecPayees) {
                            std::vector<uint256> vecVoteHashes = payee.GetVoteHashes();
                            BOOST_FOREACH(uint256& hash, vecVoteHashes) {
                                if(mnpayments.HasVerifiedPaymentVote(hash)) {
                                    CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
                                    ss.reserve(1000);
                                    ss << mnpayments.mapMasternodePaymentVotes[hash];
                                    connman.PushMessage(pfrom, NetMsgType::MASTERNODEPAYMENTVOTE, ss);
                                }
                            }
                        }
                        pushed = true;
                    }
                }

                if (!pushed && inv.type == MSG_MASTERNODE_ANNOUNCE) {
                    if(mnodeman.mapSeenMasternodeBroadcast.count(inv.hash)){
                        CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
                        ss.reserve(1000);
                        ss << mnodeman.mapSeenMasternodeBroadcast[inv.hash].second;
                        connman.PushMessage(pfrom, NetMsgType::MNANNOUNCE, ss);
                        pushed = true;
                    }
                }

                if (!pushed && inv.type == MSG_MASTERNODE_PING) {
                    if(mnodeman.mapSeenMasternodePing.count(inv.hash)) {
                        CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
                        ss.reserve(1000);
                        ss << mnodeman.mapSeenMasternodePing[inv.hash];
                        connman.PushMessage(pfrom, NetMsgType::MNPING, ss);
                        pushed = true;
                    }
                }

                if (!pushed && inv.type == MSG_DSTX) {
                    CDarksendBroadcastTx dstx = CPrivateSend::GetDSTX(inv.hash);
                    if(dstx) {
                        CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
                        ss.reserve(1000);
                        ss << dstx;
                        connman.PushMessage(pfrom, NetMsgType::DSTX, ss);
                        pushed = true;
                    }
                }

                if (!pushed && inv.type == MSG_GOVERNANCE_OBJECT) {
                    LogPrint("net", "ProcessGetData -- MSG_GOVERNANCE_OBJECT: inv = %s\n", inv.ToString());
                    CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
                    bool topush = false;
                    {
                        if(governance.HaveObjectForHash(inv.hash)) {
                            ss.reserve(1000);
                            if(governance.SerializeObjectForHash(inv.hash, ss)) {
                                topush = true;
                            }
                        }
                    }
                    LogPrint("net", "ProcessGetData -- MSG_GOVERNANCE_OBJECT: topush = %d, inv = %s\n", topush, inv.ToString());
                    if(topush) {
                        connman.PushMessage(pfrom, NetMsgType::MNGOVERNANCEOBJECT, ss);
                        pushed = true;
                    }
                }

                if (!pushed && inv.type == MSG_GOVERNANCE_OBJECT_VOTE) {
                    CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
                    bool topush = false;
                    {
                        if(governance.HaveVoteForHash(inv.hash)) {
                            ss.reserve(1000);
                            if(governance.SerializeVoteForHash(inv.hash, ss)) {
                                topush = true;
                            }
                        }
                    }
                    if(topush) {
                        LogPrint("net", "ProcessGetData -- pushing: inv = %s\n", inv.ToString());
                        connman.PushMessage(pfrom, NetMsgType::MNGOVERNANCEOBJECTVOTE, ss);
                        pushed = true;
                    }
                }

                if (!pushed && inv.type == MSG_MASTERNODE_VERIFY) {
                    if(mnodeman.mapSeenMasternodeVerification.count(inv.hash)) {
                        CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
                        ss.reserve(1000);
                        ss << mnodeman.mapSeenMasternodeVerification[inv.hash];
                        connman.PushMessage(pfrom, NetMsgType::MNVERIFY, ss);
                        pushed = true;
                    }
                }

                if (!pushed)
                    vNotFound.push_back(inv);
            }

            // Track requests for our stuff.
            GetMainSignals().Inventory(inv.hash);

            if (inv.type == MSG_BLOCK || inv.type == MSG_FILTERED_BLOCK)
                break;
        }
    }

    pfrom->vRecvGetData.erase(pfrom->vRecvGetData.begin(), it);

    if (!vNotFound.empty()) {
        // Let the peer know that we didn't find what it asked for, so it doesn't
        // have to wait around forever. Currently only SPV clients actually care
        // about this message: it's needed when they are recursively walking the
        // dependencies of relevant unconfirmed transactions. SPV clients want to
        // do that because they want to know about (and store and rebroadcast and
        // risk analyze) the dependencies of transactions relevant to them, without
        // having to download the entire memory pool.
        connman.PushMessage(pfrom, NetMsgType::NOTFOUND, vNotFound);
    }
}

bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv, int64_t nTimeReceived, CConnman& connman, std::atomic<bool>& interruptMsgProc)
{
    const CChainParams& chainparams = Params();
    RandAddSeedPerfmon();

    LogPrint("net", "received: %s (%u bytes) peer=%d\n", SanitizeString(strCommand), vRecv.size(), pfrom->id);

    if (mapArgs.count("-dropmessagestest") && GetRand(atoi(mapArgs["-dropmessagestest"])) == 0)
    {
        LogPrintf("dropmessagestest DROPPING RECV MESSAGE\n");
        return true;
    }

    if (!(pfrom->GetLocalServices() & NODE_BLOOM) &&
              (strCommand == NetMsgType::FILTERLOAD ||
               strCommand == NetMsgType::FILTERADD ||
               strCommand == NetMsgType::FILTERCLEAR))
    {
        if (pfrom->nVersion >= NO_BLOOM_VERSION) {
            LOCK(cs_main);
            Misbehaving(pfrom->GetId(), 100);
            return false;
        } else if (GetBoolArg("-enforcenodebloom", false)) {
            pfrom->fDisconnect = true;
            return false;
        }
    }


    if (strCommand == NetMsgType::VERSION)
    {
        // Feeler connections exist only to verify if address is online.
        if (pfrom->fFeeler) {
            assert(pfrom->fInbound == false);
            pfrom->fDisconnect = true;
        }

        // Each connection can only send one version message
        if (pfrom->nVersion != 0)
        {
            connman.PushMessageWithVersion(pfrom, INIT_PROTO_VERSION, NetMsgType::REJECT, strCommand, REJECT_DUPLICATE, string("Duplicate version message"));
            LOCK(cs_main);
            Misbehaving(pfrom->GetId(), 1);
            return false;
        }

        int64_t nTime;
        CAddress addrMe;
        CAddress addrFrom;
        uint64_t nNonce = 1;
        uint64_t nServiceInt;
        ServiceFlags nServices;
        int nVersion;
        int nSendVersion;
        std::string strSubVer;
        int nStartingHeight = -1;
        bool fRelay = true;

        vRecv >> nVersion >> nServiceInt >> nTime >> addrMe;
        nSendVersion = std::min(nVersion, PROTOCOL_VERSION);
        nServices = ServiceFlags(nServiceInt);
        if (!pfrom->fInbound)
        {
            connman.SetServices(pfrom->addr, nServices);
        }
        if (pfrom->nServicesExpected & ~nServices)
        {
            LogPrint("net", "peer=%d does not offer the expected services (%08x offered, %08x expected); disconnecting\n", pfrom->id, nServices, pfrom->nServicesExpected);
            connman.PushMessageWithVersion(pfrom, INIT_PROTO_VERSION, NetMsgType::REJECT, strCommand, REJECT_NONSTANDARD,
                               strprintf("Expected to offer services %08x", pfrom->nServicesExpected));
            pfrom->fDisconnect = true;
            return false;
        }

        if (nVersion < MIN_PEER_PROTO_VERSION)
        {
            // disconnect from peers older than this proto version
            LogPrintf("peer=%d using obsolete version %i; disconnecting\n", pfrom->id, nVersion);
            connman.PushMessageWithVersion(pfrom, INIT_PROTO_VERSION, NetMsgType::REJECT, strCommand, REJECT_OBSOLETE,
                               strprintf("Version must be %d or greater", MIN_PEER_PROTO_VERSION));
            pfrom->fDisconnect = true;
            return false;
        }

        if (nVersion == 10300)
            nVersion = 300;
        if (!vRecv.empty())
            vRecv >> addrFrom >> nNonce;
        if (!vRecv.empty()) {
            vRecv >> LIMITED_STRING(strSubVer, MAX_SUBVERSION_LENGTH);
        }
        if (!vRecv.empty()) {
            vRecv >> nStartingHeight;
        }
        if (!vRecv.empty())
            vRecv >> fRelay;
        // Disconnect if we connected to ourself
        if (pfrom->fInbound && !connman.CheckIncomingNonce(nNonce))
        {
            LogPrintf("connected to self at %s, disconnecting\n", pfrom->addr.ToString());
            pfrom->fDisconnect = true;
            return true;
        }

        if (pfrom->fInbound && addrMe.IsRoutable())
        {
            SeenLocal(addrMe);
        }

        // Be shy and don't send version until we hear
        if (pfrom->fInbound)
            PushNodeVersion(pfrom, connman, GetAdjustedTime());

        connman.PushMessageWithVersion(pfrom, INIT_PROTO_VERSION, NetMsgType::VERACK);

        pfrom->nServices = nServices;
        pfrom->addrLocal = addrMe;
        pfrom->strSubVer = strSubVer;
        pfrom->cleanSubVer = SanitizeString(strSubVer);
        pfrom->nStartingHeight = nStartingHeight;
        pfrom->fClient = !(nServices & NODE_NETWORK);
        {
            LOCK(pfrom->cs_filter);
            pfrom->fRelayTxes = fRelay; // set to true after we get the first filter* message
        }

        // Change version
        pfrom->SetSendVersion(nSendVersion);
        pfrom->nVersion = nVersion;

        // Potentially mark this peer as a preferred download peer.
        {
        LOCK(cs_main);
        UpdatePreferredDownload(pfrom, State(pfrom->GetId()));
        }

        if (!pfrom->fInbound)
        {
            // Advertise our address
            if (fListen && !IsInitialBlockDownload())
            {
                CAddress addr = GetLocalAddress(&pfrom->addr, pfrom->GetLocalServices());
                if (addr.IsRoutable())
                {
                    LogPrintf("ProcessMessages: advertising address %s\n", addr.ToString());
                    pfrom->PushAddress(addr);
                } else if (IsPeerAddrLocalGood(pfrom)) {
                    addr.SetIP(pfrom->addrLocal);
                    LogPrintf("ProcessMessages: advertising address %s\n", addr.ToString());
                    pfrom->PushAddress(addr);
                }
            }

            // Get recent addresses
            if (pfrom->fOneShot || pfrom->nVersion >= CADDR_TIME_VERSION || connman.GetAddressCount() < 1000)
            {
                connman.PushMessage(pfrom, NetMsgType::GETADDR);
                pfrom->fGetAddr = true;
            }
            connman.MarkAddressGood(pfrom->addr);
        }

        // Relay alerts
        {
            LOCK(cs_mapAlerts);
            BOOST_FOREACH(PAIRTYPE(const uint256, CAlert)& item, mapAlerts)
                item.second.RelayTo(pfrom, connman);
        }

        string remoteAddr;
        if (fLogIPs)
            remoteAddr = ", peeraddr=" + pfrom->addr.ToString();

        LogPrintf("receive version message: %s: version %d, blocks=%d, us=%s, peer=%d%s\n",
                  pfrom->cleanSubVer, pfrom->nVersion,
                  pfrom->nStartingHeight, addrMe.ToString(), pfrom->id,
                  remoteAddr);

        int64_t nTimeOffset = nTime - GetTime();
        pfrom->nTimeOffset = nTimeOffset;
        AddTimeData(pfrom->addr, nTimeOffset);
    }


    else if (pfrom->nVersion == 0)
    {
        // Must have a version message before anything else
        LOCK(cs_main);
        Misbehaving(pfrom->GetId(), 1);
        return false;
    }


    else if (strCommand == NetMsgType::VERACK)
    {
        pfrom->SetRecvVersion(std::min(pfrom->nVersion.load(), PROTOCOL_VERSION));

        // Mark this node as currently connected, so we update its timestamp later.
        if (pfrom->fNetworkNode) {
            LOCK(cs_main);
            State(pfrom->GetId())->fCurrentlyConnected = true;
        }

        if (pfrom->nVersion >= SENDHEADERS_VERSION) {
            // Tell our peer we prefer to receive headers rather than inv's
            // We send this to non-NODE NETWORK peers as well, because even
            // non-NODE NETWORK peers can announce blocks (such as pruning
            // nodes)
            connman.PushMessage(pfrom, NetMsgType::SENDHEADERS);
        }
        pfrom->fSuccessfullyConnected = true;
    }


    else if (strCommand == NetMsgType::ADDR)
    {
        vector<CAddress> vAddr;
        vRecv >> vAddr;

        // Don't want addr from older versions unless seeding
        if (pfrom->nVersion < CADDR_TIME_VERSION && connman.GetAddressCount() > 1000)
            return true;
        if (vAddr.size() > 1000)
        {
            LOCK(cs_main);
            Misbehaving(pfrom->GetId(), 20);
            return error("message addr size() = %u", vAddr.size());
        }

        // Store the new addresses
        vector<CAddress> vAddrOk;
        int64_t nNow = GetAdjustedTime();
        int64_t nSince = nNow - 10 * 60;
        BOOST_FOREACH(CAddress& addr, vAddr)
        {
            if (interruptMsgProc)
                return true;

            if ((addr.nServices & REQUIRED_SERVICES) != REQUIRED_SERVICES)
                continue;

            if (addr.nTime <= 100000000 || addr.nTime > nNow + 10 * 60)
                addr.nTime = nNow - 5 * 24 * 60 * 60;
            pfrom->AddAddressKnown(addr);
            bool fReachable = IsReachable(addr);
            if (addr.nTime > nSince && !pfrom->fGetAddr && vAddr.size() <= 10 && addr.IsRoutable())
            {
                RelayAddress(addr, fReachable, connman);
            }
            // Do not store addresses outside our network
            if (fReachable)
                vAddrOk.push_back(addr);
        }
        connman.AddNewAddresses(vAddrOk, pfrom->addr, 2 * 60 * 60);
        if (vAddr.size() < 1000)
            pfrom->fGetAddr = false;
        if (pfrom->fOneShot)
            pfrom->fDisconnect = true;
    }

    else if (strCommand == NetMsgType::SENDHEADERS)
    {
        LOCK(cs_main);
        State(pfrom->GetId())->fPreferHeaders = true;
    }


    else if (strCommand == NetMsgType::INV)
    {
        vector<CInv> vInv;
        vRecv >> vInv;
        if (vInv.size() > MAX_INV_SZ)
        {
            LOCK(cs_main);
            Misbehaving(pfrom->GetId(), 20);
            return error("message inv size() = %u", vInv.size());
        }

        bool fBlocksOnly = !fRelayTxes;

        // Allow whitelisted peers to send data other than blocks in blocks only mode if whitelistrelay is true
        if (pfrom->fWhitelisted && GetBoolArg("-whitelistrelay", DEFAULT_WHITELISTRELAY))
            fBlocksOnly = false;

        LOCK(cs_main);

        std::vector<CInv> vToFetch;


        for (unsigned int nInv = 0; nInv < vInv.size(); nInv++)
        {
            const CInv &inv = vInv[nInv];

            if(!inv.IsKnownType()) {
                LogPrint("net", "got inv of unknown type %d: %s peer=%d\n", inv.type, inv.hash.ToString(), pfrom->id);
                continue;
            }

            if (interruptMsgProc)
                return true;

            pfrom->AddInventoryKnown(inv);

            bool fAlreadyHave = AlreadyHave(inv);
            LogPrint("net", "got inv: %s  %s peer=%d\n", inv.ToString(), fAlreadyHave ? "have" : "new", pfrom->id);

            if (inv.type == MSG_BLOCK) {
                UpdateBlockAvailability(pfrom->GetId(), inv.hash);
                if (!fAlreadyHave && !fImporting && !fReindex && !mapBlocksInFlight.count(inv.hash)) {
                    if (chainparams.DelayGetHeadersTime() != 0 && pindexBestHeader->GetBlockTime() < GetAdjustedTime() - chainparams.DelayGetHeadersTime()) {
                        // We are pretty far from being completely synced at the moment. If we would initiate a new
                        // chain of GETHEADERS/HEADERS now, we may end up downnloading the full chain from multiple
                        // peers at the same time, slowing down the initial sync. At the same time, we don't know
                        // if the peer we got this INV from may have a chain we don't know about yet, so we HAVE TO
                        // send a GETHEADERS message at some point in time. This is delayed to later in SendMessages
                        // when the headers chain has catched up enough.
                        LogPrint("net", "delaying getheaders (%d) %s to peer=%d\n", pindexBestHeader->nHeight, inv.hash.ToString(), pfrom->id);
                        pfrom->PushBlockHashFromINV(inv.hash);
                    } else {
                        // First request the headers preceding the announced block. In the normal fully-synced
                        // case where a new block is announced that succeeds the current tip (no reorganization),
                        // there are no such headers.
                        // Secondly, and only when we are close to being synced, we request the announced block directly,
                        // to avoid an extra round-trip. Note that we must *first* ask for the headers, so by the
                        // time the block arrives, the header chain leading up to it is already validated. Not
                        // doing this will result in the received block being rejected as an orphan in case it is
                        // not a direct successor.
                        connman.PushMessage(pfrom, NetMsgType::GETHEADERS, chainActive.GetLocator(pindexBestHeader), inv.hash);
                        CNodeState *nodestate = State(pfrom->GetId());
                        if (CanDirectFetch(chainparams.GetConsensus()) &&
                            nodestate->nBlocksInFlight < MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
                            vToFetch.push_back(inv);
                            // Mark block as in flight already, even though the actual "getdata" message only goes out
                            // later (within the same cs_main lock, though).
                            MarkBlockAsInFlight(pfrom->GetId(), inv.hash, chainparams.GetConsensus());
                        }
                        LogPrint("net", "getheaders (%d) %s to peer=%d\n", pindexBestHeader->nHeight, inv.hash.ToString(), pfrom->id);
                    }
                }
            }
            else
            {
                if (fBlocksOnly)
                    LogPrint("net", "transaction (%s) inv sent in violation of protocol peer=%d\n", inv.hash.ToString(), pfrom->id);
                else if (!fAlreadyHave && !fImporting && !fReindex && !IsInitialBlockDownload())
                    pfrom->AskFor(inv);
            }

            // Track requests for our stuff
            GetMainSignals().Inventory(inv.hash);
        }

        if (!vToFetch.empty())
            connman.PushMessage(pfrom, NetMsgType::GETDATA, vToFetch);
    }


    else if (strCommand == NetMsgType::GETDATA)
    {
        vector<CInv> vInv;
        vRecv >> vInv;
        if (vInv.size() > MAX_INV_SZ)
        {
            LOCK(cs_main);
            Misbehaving(pfrom->GetId(), 20);
            return error("message getdata size() = %u", vInv.size());
        }

        if (fDebug || (vInv.size() != 1))
            LogPrint("net", "received getdata (%u invsz) peer=%d\n", vInv.size(), pfrom->id);

        if ((fDebug && vInv.size() > 0) || (vInv.size() == 1))
            LogPrint("net", "received getdata for: %s peer=%d\n", vInv[0].ToString(), pfrom->id);

        pfrom->vRecvGetData.insert(pfrom->vRecvGetData.end(), vInv.begin(), vInv.end());
        ProcessGetData(pfrom, chainparams.GetConsensus(), connman, interruptMsgProc);
    }


    else if (strCommand == NetMsgType::GETBLOCKS)
    {
        CBlockLocator locator;
        uint256 hashStop;
        vRecv >> locator >> hashStop;

        LOCK(cs_main);

        // Find the last block the caller has in the main chain
        CBlockIndex* pindex = FindForkInGlobalIndex(chainActive, locator);

        // Send the rest of the chain
        if (pindex)
            pindex = chainActive.Next(pindex);
        int nLimit = 500;
        LogPrint("net", "getblocks %d to %s limit %d from peer=%d\n", (pindex ? pindex->nHeight : -1), hashStop.IsNull() ? "end" : hashStop.ToString(), nLimit, pfrom->id);
        for (; pindex; pindex = chainActive.Next(pindex))
        {
            if (pindex->GetBlockHash() == hashStop)
            {
                LogPrint("net", "  getblocks stopping at %d %s\n", pindex->nHeight, pindex->GetBlockHash().ToString());
                break;
            }
            // If pruning, don't inv blocks unless we have on disk and are likely to still have
            // for some reasonable time window (1 hour) that block relay might require.
            const int nPrunedBlocksLikelyToHave = MIN_BLOCKS_TO_KEEP - 3600 / chainparams.GetConsensus().nPowTargetSpacing;
            if (fPruneMode && (!(pindex->nStatus & BLOCK_HAVE_DATA) || pindex->nHeight <= chainActive.Tip()->nHeight - nPrunedBlocksLikelyToHave))
            {
                LogPrint("net", " getblocks stopping, pruned or too old block at %d %s\n", pindex->nHeight, pindex->GetBlockHash().ToString());
                break;
            }
            pfrom->PushInventory(CInv(MSG_BLOCK, pindex->GetBlockHash()));
            if (--nLimit <= 0)
            {
                // When this block is requested, we'll send an inv that'll
                // trigger the peer to getblocks the next batch of inventory.
                LogPrint("net", "  getblocks stopping at limit %d %s\n", pindex->nHeight, pindex->GetBlockHash().ToString());
                pfrom->hashContinue = pindex->GetBlockHash();
                break;
            }
        }
    }


    else if (strCommand == NetMsgType::GETHEADERS)
    {
        CBlockLocator locator;
        uint256 hashStop;
        vRecv >> locator >> hashStop;

        LOCK(cs_main);
        if (IsInitialBlockDownload() && !pfrom->fWhitelisted) {
            LogPrint("net", "Ignoring getheaders from peer=%d because node is in initial block download\n", pfrom->id);
            return true;
        }

        CNodeState *nodestate = State(pfrom->GetId());
        CBlockIndex* pindex = NULL;
        if (locator.IsNull())
        {
            // If locator is null, return the hashStop block
            BlockMap::iterator mi = mapBlockIndex.find(hashStop);
            if (mi == mapBlockIndex.end())
                return true;
            pindex = (*mi).second;
        }
        else
        {
            // Find the last block the caller has in the main chain
            pindex = FindForkInGlobalIndex(chainActive, locator);
            if (pindex)
                pindex = chainActive.Next(pindex);
        }

        // we must use CBlocks, as CBlockHeaders won't include the 0x00 nTx count at the end
        vector<CBlock> vHeaders;
        int nLimit = MAX_HEADERS_RESULTS;
        LogPrint("net", "getheaders %d to %s from peer=%d\n", (pindex ? pindex->nHeight : -1), hashStop.ToString(), pfrom->id);
        for (; pindex; pindex = chainActive.Next(pindex))
        {
            vHeaders.push_back(pindex->GetBlockHeader());
            if (--nLimit <= 0 || pindex->GetBlockHash() == hashStop)
                break;
        }
        // pindex can be NULL either if we sent chainActive.Tip() OR
        // if our peer has chainActive.Tip() (and thus we are sending an empty
        // headers message). In both cases it's safe to update
        // pindexBestHeaderSent to be our tip.
        nodestate->pindexBestHeaderSent = pindex ? pindex : chainActive.Tip();
        connman.PushMessage(pfrom, NetMsgType::HEADERS, vHeaders);
    }


    else if (strCommand == NetMsgType::TX || strCommand == NetMsgType::DSTX || strCommand == NetMsgType::TXLOCKREQUEST)
    {
        // Stop processing the transaction early if
        // We are in blocks only mode and peer is either not whitelisted or whitelistrelay is off
        if (!fRelayTxes && (!pfrom->fWhitelisted || !GetBoolArg("-whitelistrelay", DEFAULT_WHITELISTRELAY)))
        {
            LogPrint("net", "transaction sent in violation of protocol peer=%d\n", pfrom->id);
            return true;
        }

        vector<uint256> vWorkQueue;
        vector<uint256> vEraseQueue;
        CTransaction tx;
        CTxLockRequest txLockRequest;
        CDarksendBroadcastTx dstx;
        int nInvType = MSG_TX;

        // Read data and assign inv type
        if(strCommand == NetMsgType::TX) {
            vRecv >> tx;
        } else if(strCommand == NetMsgType::TXLOCKREQUEST) {
            vRecv >> txLockRequest;
            tx = txLockRequest;
            nInvType = MSG_TXLOCK_REQUEST;
        } else if (strCommand == NetMsgType::DSTX) {
            vRecv >> dstx;
            tx = dstx.tx;
            nInvType = MSG_DSTX;
        }

        CInv inv(nInvType, tx.GetHash());
        pfrom->AddInventoryKnown(inv);
        pfrom->setAskFor.erase(inv.hash);

        // Process custom logic, no matter if tx will be accepted to mempool later or not
        if (strCommand == NetMsgType::TXLOCKREQUEST) {
            if(!instantsend.ProcessTxLockRequest(txLockRequest, connman)) {
                LogPrint("instantsend", "TXLOCKREQUEST -- failed %s\n", txLockRequest.GetHash().ToString());
                return false;
            }
        } else if (strCommand == NetMsgType::DSTX) {
            uint256 hashTx = tx.GetHash();
            if(CPrivateSend::GetDSTX(hashTx)) {
                LogPrint("privatesend", "DSTX -- Already have %s, skipping...\n", hashTx.ToString());
                return true; // not an error
            }

            CMasternode mn;

            if(!mnodeman.Get(dstx.vin.prevout, mn)) {
                LogPrint("privatesend", "DSTX -- Can't find masternode %s to verify %s\n", dstx.vin.prevout.ToStringShort(), hashTx.ToString());
                return false;
            }

            if(!mn.fAllowMixingTx) {
                LogPrint("privatesend", "DSTX -- Masternode %s is sending too many transactions %s\n", dstx.vin.prevout.ToStringShort(), hashTx.ToString());
                return true;
                // TODO: Not an error? Could it be that someone is relaying old DSTXes
                // we have no idea about (e.g we were offline)? How to handle them?
            }

            if(!dstx.CheckSignature(mn.pubKeyMasternode)) {
                LogPrint("privatesend", "DSTX -- CheckSignature() failed for %s\n", hashTx.ToString());
                return false;
            }

            LogPrintf("DSTX -- Got Masternode transaction %s\n", hashTx.ToString());
            mempool.PrioritiseTransaction(hashTx, hashTx.ToString(), 1000, 0.1*COIN);
            mnodeman.DisallowMixing(dstx.vin.prevout);
        }

        LOCK(cs_main);

        bool fMissingInputs = false;
        CValidationState state;

        mapAlreadyAskedFor.erase(inv.hash);

        if (!AlreadyHave(inv) && AcceptToMemoryPool(mempool, state, tx, true, &fMissingInputs))
        {
            // Process custom txes, this changes AlreadyHave to "true"
            if (strCommand == NetMsgType::DSTX) {
                LogPrintf("DSTX -- Masternode transaction accepted, txid=%s, peer=%d\n",
                        tx.GetHash().ToString(), pfrom->id);
                CPrivateSend::AddDSTX(dstx);
            } else if (strCommand == NetMsgType::TXLOCKREQUEST) {
                LogPrintf("TXLOCKREQUEST -- Transaction Lock Request accepted, txid=%s, peer=%d\n",
                        tx.GetHash().ToString(), pfrom->id);
                instantsend.AcceptLockRequest(txLockRequest);
            }

            mempool.check(pcoinsTip);
            connman.RelayTransaction(tx);
            vWorkQueue.push_back(inv.hash);

            pfrom->nLastTXTime = GetTime();

            LogPrint("mempool", "AcceptToMemoryPool: peer=%d: accepted %s (poolsz %u txn, %u kB)\n",
                pfrom->id,
                tx.GetHash().ToString(),
                mempool.size(), mempool.DynamicMemoryUsage() / 1000);

            // Recursively process any orphan transactions that depended on this one
            set<NodeId> setMisbehaving;
            for (unsigned int i = 0; i < vWorkQueue.size(); i++)
            {
                map<uint256, set<uint256> >::iterator itByPrev = mapOrphanTransactionsByPrev.find(vWorkQueue[i]);
                if (itByPrev == mapOrphanTransactionsByPrev.end())
                    continue;
                for (set<uint256>::iterator mi = itByPrev->second.begin();
                     mi != itByPrev->second.end();
                     ++mi)
                {
                    const uint256& orphanHash = *mi;
                    const CTransaction& orphanTx = mapOrphanTransactions[orphanHash].tx;
                    NodeId fromPeer = mapOrphanTransactions[orphanHash].fromPeer;
                    bool fMissingInputs2 = false;
                    // Use a dummy CValidationState so someone can't setup nodes to counter-DoS based on orphan
                    // resolution (that is, feeding people an invalid transaction based on LegitTxX in order to get
                    // anyone relaying LegitTxX banned)
                    CValidationState stateDummy;


                    if (setMisbehaving.count(fromPeer))
                        continue;
                    if (AcceptToMemoryPool(mempool, stateDummy, orphanTx, true, &fMissingInputs2))
                    {
                        LogPrint("mempool", "   accepted orphan tx %s\n", orphanHash.ToString());
                        connman.RelayTransaction(orphanTx);
                        vWorkQueue.push_back(orphanHash);
                        vEraseQueue.push_back(orphanHash);
                    }
                    else if (!fMissingInputs2)
                    {
                        int nDos = 0;
                        if (stateDummy.IsInvalid(nDos) && nDos > 0)
                        {
                            // Punish peer that gave us an invalid orphan tx
                            Misbehaving(fromPeer, nDos);
                            setMisbehaving.insert(fromPeer);
                            LogPrint("mempool", "   invalid orphan tx %s\n", orphanHash.ToString());
                        }
                        // Has inputs but not accepted to mempool
                        // Probably non-standard or insufficient fee/priority
                        LogPrint("mempool", "   removed orphan tx %s\n", orphanHash.ToString());
                        vEraseQueue.push_back(orphanHash);
                        assert(recentRejects);
                        recentRejects->insert(orphanHash);
                    }
                    mempool.check(pcoinsTip);
                }
            }

            BOOST_FOREACH(uint256 hash, vEraseQueue)
                EraseOrphanTx(hash);
        }
        else if (fMissingInputs)
        {
            AddOrphanTx(tx, pfrom->GetId());

            // DoS prevention: do not allow mapOrphanTransactions to grow unbounded
            unsigned int nMaxOrphanTx = (unsigned int)std::max((int64_t)0, GetArg("-maxorphantx", DEFAULT_MAX_ORPHAN_TRANSACTIONS));
            unsigned int nEvicted = LimitOrphanTxSize(nMaxOrphanTx);
            if (nEvicted > 0)
                LogPrint("mempool", "mapOrphan overflow, removed %u tx\n", nEvicted);
        } else {
            assert(recentRejects);
            recentRejects->insert(tx.GetHash());

            if (strCommand == NetMsgType::TXLOCKREQUEST && !AlreadyHave(inv)) {
                // i.e. AcceptToMemoryPool failed, probably because it's conflicting
                // with existing normal tx or tx lock for another tx. For the same tx lock
                // AlreadyHave would have return "true" already.

                // It's the first time we failed for this tx lock request,
                // this should switch AlreadyHave to "true".
                instantsend.RejectLockRequest(txLockRequest);
                // this lets other nodes to create lock request candidate i.e.
                // this allows multiple conflicting lock requests to compete for votes
                connman.RelayTransaction(tx);
            }

            if (pfrom->fWhitelisted && GetBoolArg("-whitelistforcerelay", DEFAULT_WHITELISTFORCERELAY)) {
                // Always relay transactions received from whitelisted peers, even
                // if they were already in the mempool or rejected from it due
                // to policy, allowing the node to function as a gateway for
                // nodes hidden behind it.
                //
                // Never relay transactions that we would assign a non-zero DoS
                // score for, as we expect peers to do the same with us in that
                // case.
                int nDoS = 0;
                if (!state.IsInvalid(nDoS) || nDoS == 0) {
                    LogPrintf("Force relaying tx %s from whitelisted peer=%d\n", tx.GetHash().ToString(), pfrom->id);
                    connman.RelayTransaction(tx);
                } else {
                    LogPrintf("Not relaying invalid transaction %s from whitelisted peer=%d (%s)\n", tx.GetHash().ToString(), pfrom->id, FormatStateMessage(state));
                }
            }
        }

        int nDoS = 0;
        if (state.IsInvalid(nDoS))
        {
            LogPrint("mempoolrej", "%s from peer=%d was not accepted: %s\n", tx.GetHash().ToString(),
                pfrom->id,
                FormatStateMessage(state));
            if (state.GetRejectCode() < REJECT_INTERNAL) // Never send AcceptToMemoryPool's internal codes over P2P
                connman.PushMessage(pfrom, NetMsgType::REJECT, strCommand, (unsigned char)state.GetRejectCode(),
                                   state.GetRejectReason().substr(0, MAX_REJECT_MESSAGE_LENGTH), inv.hash);
            if (nDoS > 0)
                Misbehaving(pfrom->GetId(), nDoS);
        }
    }


    else if (strCommand == NetMsgType::HEADERS && !fImporting && !fReindex) // Ignore headers received while importing
    {
        std::vector<CBlockHeader> headers;

        // Bypass the normal CBlock deserialization, as we don't want to risk deserializing 2000 full blocks.
        unsigned int nCount = ReadCompactSize(vRecv);
        if (nCount > MAX_HEADERS_RESULTS) {
            LOCK(cs_main);
            Misbehaving(pfrom->GetId(), 20);
            return error("headers message size = %u", nCount);
        }
        headers.resize(nCount);
        for (unsigned int n = 0; n < nCount; n++) {
            vRecv >> headers[n];
            ReadCompactSize(vRecv); // ignore tx count; assume it is 0.
        }

        CBlockIndex *pindexLast = NULL;
        {
        LOCK(cs_main);
        uint256 hashLastBlock;
        for (const CBlockHeader& header : headers) {
            if (!hashLastBlock.IsNull() && header.hashPrevBlock != hashLastBlock) {
                Misbehaving(pfrom->GetId(), 20);
                return error("non-continuous headers sequence");
            }
            hashLastBlock = header.GetHash();
        }
        }

        CValidationState state;
        if (!ProcessNewBlockHeaders(headers, state, chainparams, &pindexLast)) {
            int nDoS;
            if (state.IsInvalid(nDoS)) {
                if (nDoS > 0) {
                    LOCK(cs_main);
                    Misbehaving(pfrom->GetId(), nDoS);
                }
                return error("invalid header received");
            }
        }

        {
        LOCK(cs_main);
        if (pindexLast)
            UpdateBlockAvailability(pfrom->GetId(), pindexLast->GetBlockHash());

        if (nCount == MAX_HEADERS_RESULTS && pindexLast) {
            // Headers message had its maximum size; the peer may have more headers.
            // TODO: optimize: if pindexLast is an ancestor of chainActive.Tip or pindexBestHeader, continue
            // from there instead.
            LogPrint("net", "more getheaders (%d) to end to peer=%d (startheight:%d)\n", pindexLast->nHeight, pfrom->id, pfrom->nStartingHeight);
            connman.PushMessage(pfrom, NetMsgType::GETHEADERS, chainActive.GetLocator(pindexLast), uint256());
        } else {
            if (chainparams.DelayGetHeadersTime() != 0 && pindexBestHeader->GetBlockTime() < GetAdjustedTime() - chainparams.DelayGetHeadersTime()) {
                // peer has sent us a HEADERS message below maximum size and we are still quite far from being fully
                // synced, this means we probably got a bad peer for initial sync and need to continue with another one.
                // By disconnecting we force to start a new iteration of initial headers sync in SendMessages
                // TODO should we handle whitelisted peers here as we do in headers sync timeout handling?
                pfrom->fDisconnect = true;
                return error("detected bad peer for initial headers sync, disconnecting %d", pfrom->id);
            }

            if (nCount == 0) {
                // Nothing interesting. Stop asking this peers for more headers.
                return true;
            }
        }

        bool fCanDirectFetch = CanDirectFetch(chainparams.GetConsensus());
        CNodeState *nodestate = State(pfrom->GetId());
        // If this set of headers is valid and ends in a block with at least as
        // much work as our tip, download as much as possible.
        if (fCanDirectFetch && pindexLast->IsValid(BLOCK_VALID_TREE) && chainActive.Tip()->nChainWork <= pindexLast->nChainWork) {
            vector<CBlockIndex *> vToFetch;
            CBlockIndex *pindexWalk = pindexLast;
            // Calculate all the blocks we'd need to switch to pindexLast, up to a limit.
            while (pindexWalk && !chainActive.Contains(pindexWalk) && vToFetch.size() <= MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
                if (!(pindexWalk->nStatus & BLOCK_HAVE_DATA) &&
                        !mapBlocksInFlight.count(pindexWalk->GetBlockHash())) {
                    // We don't have this block, and it's not yet in flight.
                    vToFetch.push_back(pindexWalk);
                }
                pindexWalk = pindexWalk->pprev;
            }
            // If pindexWalk still isn't on our main chain, we're looking at a
            // very large reorg at a time we think we're close to caught up to
            // the main chain -- this shouldn't really happen.  Bail out on the
            // direct fetch and rely on parallel download instead.
            if (!chainActive.Contains(pindexWalk)) {
                LogPrint("net", "Large reorg, won't direct fetch to %s (%d)\n",
                        pindexLast->GetBlockHash().ToString(),
                        pindexLast->nHeight);
            } else {
                vector<CInv> vGetData;
                // Download as much as possible, from earliest to latest.
                BOOST_REVERSE_FOREACH(CBlockIndex *pindex, vToFetch) {
                    if (nodestate->nBlocksInFlight >= MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
                        // Can't download any more from this peer
                        break;
                    }
                    vGetData.push_back(CInv(MSG_BLOCK, pindex->GetBlockHash()));
                    MarkBlockAsInFlight(pfrom->GetId(), pindex->GetBlockHash(), chainparams.GetConsensus(), pindex);
                    LogPrint("net", "Requesting block %s from  peer=%d\n",
                            pindex->GetBlockHash().ToString(), pfrom->id);
                }
                if (vGetData.size() > 1) {
                    LogPrint("net", "Downloading blocks toward %s (%d) via headers direct fetch\n",
                            pindexLast->GetBlockHash().ToString(), pindexLast->nHeight);
                }
                if (vGetData.size() > 0) {
                    connman.PushMessage(pfrom, NetMsgType::GETDATA, vGetData);
                }
            }
        }
        }
    }

    else if (strCommand == NetMsgType::BLOCK && !fImporting && !fReindex) // Ignore blocks received while importing
    {
        CBlock block;
        vRecv >> block;

        CInv inv(MSG_BLOCK, block.GetHash());
        LogPrint("net", "received block %s peer=%d\n", inv.hash.ToString(), pfrom->id);

        pfrom->AddInventoryKnown(inv);

        // Process all blocks from whitelisted peers, even if not requested,
        // unless we're still syncing with the network.
        // Such an unrequested block may still be processed, subject to the
        // conditions in AcceptBlock().
        bool forceProcessing = pfrom->fWhitelisted && !IsInitialBlockDownload();
        const uint256 hash(block.GetHash());
        {
            LOCK(cs_main);
            // Also always process if we requested the block explicitly, as we may
            // need it even though it is not a candidate for a new best tip.
            forceProcessing |= MarkBlockAsReceived(hash);
            // mapBlockSource is only used for sending reject messages and DoS scores,
            // so the race between here and cs_main in ProcessNewBlock is fine.
            mapBlockSource.emplace(hash, pfrom->GetId());
        }
        bool fNewBlock = false;
        ProcessNewBlock(chainparams, &block, forceProcessing, NULL, &fNewBlock);
        if (fNewBlock)
            pfrom->nLastBlockTime = GetTime();
    }


    else if (strCommand == NetMsgType::GETADDR)
    {
        // This asymmetric behavior for inbound and outbound connections was introduced
        // to prevent a fingerprinting attack: an attacker can send specific fake addresses
        // to users' AddrMan and later request them by sending getaddr messages.
        // Making nodes which are behind NAT and can only make outgoing connections ignore
        // the getaddr message mitigates the attack.
        if (!pfrom->fInbound) {
            LogPrint("net", "Ignoring \"getaddr\" from outbound connection. peer=%d\n", pfrom->id);
            return true;
        }

        pfrom->vAddrToSend.clear();
        vector<CAddress> vAddr = connman.GetAddresses();
        BOOST_FOREACH(const CAddress &addr, vAddr)
            pfrom->PushAddress(addr);
    }


    else if (strCommand == NetMsgType::MEMPOOL)
    {
        if (connman.OutboundTargetReached(false) && !pfrom->fWhitelisted)
        {
            LogPrint("net", "mempool request with bandwidth limit reached, disconnect peer=%d\n", pfrom->GetId());
            pfrom->fDisconnect = true;
            return true;
        }
        LOCK2(cs_main, pfrom->cs_filter);

        std::vector<uint256> vtxid;
        mempool.queryHashes(vtxid);
        vector<CInv> vInv;
        BOOST_FOREACH(uint256& hash, vtxid) {
            CInv inv(MSG_TX, hash);
            if (pfrom->pfilter) {
                CTransaction tx;
                bool fInMemPool = mempool.lookup(hash, tx);
                if (!fInMemPool) continue; // another thread removed since queryHashes, maybe...
                if (!pfrom->pfilter->IsRelevantAndUpdate(tx)) continue;
            }
            vInv.push_back(inv);
            if (vInv.size() == MAX_INV_SZ) {
                connman.PushMessage(pfrom, NetMsgType::INV, vInv);
                vInv.clear();
            }
        }
        if (vInv.size() > 0)
            connman.PushMessage(pfrom, NetMsgType::INV, vInv);
    }


    else if (strCommand == NetMsgType::PING)
    {
        if (pfrom->nVersion > BIP0031_VERSION)
        {
            uint64_t nonce = 0;
            vRecv >> nonce;
            // Echo the message back with the nonce. This allows for two useful features:
            //
            // 1) A remote node can quickly check if the connection is operational
            // 2) Remote nodes can measure the latency of the network thread. If this node
            //    is overloaded it won't respond to pings quickly and the remote node can
            //    avoid sending us more work, like chain download requests.
            //
            // The nonce stops the remote getting confused between different pings: without
            // it, if the remote node sends a ping once per second and this node takes 5
            // seconds to respond to each, the 5th ping the remote sends would appear to
            // return very quickly.
            connman.PushMessage(pfrom, NetMsgType::PONG, nonce);
        }
    }


    else if (strCommand == NetMsgType::PONG)
    {
        int64_t pingUsecEnd = nTimeReceived;
        uint64_t nonce = 0;
        size_t nAvail = vRecv.in_avail();
        bool bPingFinished = false;
        std::string sProblem;

        if (nAvail >= sizeof(nonce)) {
            vRecv >> nonce;

            // Only process pong message if there is an outstanding ping (old ping without nonce should never pong)
            if (pfrom->nPingNonceSent != 0) {
                if (nonce == pfrom->nPingNonceSent) {
                    // Matching pong received, this ping is no longer outstanding
                    bPingFinished = true;
                    int64_t pingUsecTime = pingUsecEnd - pfrom->nPingUsecStart;
                    if (pingUsecTime > 0) {
                        // Successful ping time measurement, replace previous
                        pfrom->nPingUsecTime = pingUsecTime;
                        pfrom->nMinPingUsecTime = std::min(pfrom->nMinPingUsecTime, pingUsecTime);
                    } else {
                        // This should never happen
                        sProblem = "Timing mishap";
                    }
                } else {
                    // Nonce mismatches are normal when pings are overlapping
                    sProblem = "Nonce mismatch";
                    if (nonce == 0) {
                        // This is most likely a bug in another implementation somewhere; cancel this ping
                        bPingFinished = true;
                        sProblem = "Nonce zero";
                    }
                }
            } else {
                sProblem = "Unsolicited pong without ping";
            }
        } else {
            // This is most likely a bug in another implementation somewhere; cancel this ping
            bPingFinished = true;
            sProblem = "Short payload";
        }

        if (!(sProblem.empty())) {
            LogPrint("net", "pong peer=%d: %s, %x expected, %x received, %u bytes\n",
                pfrom->id,
                sProblem,
                pfrom->nPingNonceSent,
                nonce,
                nAvail);
        }
        if (bPingFinished) {
            pfrom->nPingNonceSent = 0;
        }
    }


    else if (fAlerts && strCommand == NetMsgType::ALERT)
    {
        CAlert alert;
        vRecv >> alert;

        uint256 alertHash = alert.GetHash();
        if (pfrom->setKnown.count(alertHash) == 0)
        {
            if (alert.ProcessAlert(chainparams.AlertKey()))
            {
                // Relay
                pfrom->setKnown.insert(alertHash);
                {
                    connman.ForEachNode([&alert, &connman](CNode* pnode) {
                        alert.RelayTo(pnode, connman);
                    });
                }
            }
            else {
                // Small DoS penalty so peers that send us lots of
                // duplicate/expired/invalid-signature/whatever alerts
                // eventually get banned.
                // This isn't a Misbehaving(100) (immediate ban) because the
                // peer might be an older or different implementation with
                // a different signature key, etc.
                Misbehaving(pfrom->GetId(), 10);
            }
        }
    }


    else if (strCommand == NetMsgType::FILTERLOAD)
    {
        CBloomFilter filter;
        vRecv >> filter;

        if (!filter.IsWithinSizeConstraints())
        {
            // There is no excuse for sending a too-large filter
            LOCK(cs_main);
            Misbehaving(pfrom->GetId(), 100);
        }
        else
        {
            LOCK(pfrom->cs_filter);
            delete pfrom->pfilter;
            pfrom->pfilter = new CBloomFilter(filter);
            pfrom->pfilter->UpdateEmptyFull();
        }
        pfrom->fRelayTxes = true;
    }


    else if (strCommand == NetMsgType::FILTERADD)
    {
        vector<unsigned char> vData;
        vRecv >> vData;

        // Nodes must NEVER send a data item > 520 bytes (the max size for a script data object,
        // and thus, the maximum size any matched object can have) in a filteradd message
        if (vData.size() > MAX_SCRIPT_ELEMENT_SIZE)
        {
            LOCK(cs_main);
            Misbehaving(pfrom->GetId(), 100);
        } else {
            LOCK(pfrom->cs_filter);
            if (pfrom->pfilter)
                pfrom->pfilter->insert(vData);
            else
            {
                LOCK(cs_main);
                Misbehaving(pfrom->GetId(), 100);
            }
        }
    }


    else if (strCommand == NetMsgType::FILTERCLEAR)
    {
        LOCK(pfrom->cs_filter);
        delete pfrom->pfilter;
        pfrom->pfilter = new CBloomFilter();
        pfrom->fRelayTxes = true;
    }


    else if (strCommand == NetMsgType::REJECT)
    {
        if (fDebug) {
            try {
                string strMsg; unsigned char ccode; string strReason;
                vRecv >> LIMITED_STRING(strMsg, CMessageHeader::COMMAND_SIZE) >> ccode >> LIMITED_STRING(strReason, MAX_REJECT_MESSAGE_LENGTH);

                ostringstream ss;
                ss << strMsg << " code " << itostr(ccode) << ": " << strReason;

                if (strMsg == NetMsgType::BLOCK || strMsg == NetMsgType::TX)
                {
                    uint256 hash;
                    vRecv >> hash;
                    ss << ": hash " << hash.ToString();
                }
                LogPrint("net", "Reject %s\n", SanitizeString(ss.str()));
            } catch (const std::ios_base::failure&) {
                // Avoid feedback loops by preventing reject messages from triggering a new reject message.
                LogPrint("net", "Unparseable reject message received\n");
            }
        }
    }
    else
    {
        bool found = false;
        const std::vector<std::string> &allMessages = getAllNetMessageTypes();
        BOOST_FOREACH(const std::string msg, allMessages) {
            if(msg == strCommand) {
                found = true;
                break;
            }
        }

        if (found)
        {
            //probably one the extensions
            privateSendClient.ProcessMessage(pfrom, strCommand, vRecv, connman);
            privateSendServer.ProcessMessage(pfrom, strCommand, vRecv, connman);
            mnodeman.ProcessMessage(pfrom, strCommand, vRecv, connman);
            mnpayments.ProcessMessage(pfrom, strCommand, vRecv, connman);
            instantsend.ProcessMessage(pfrom, strCommand, vRecv, connman);
            sporkManager.ProcessSpork(pfrom, strCommand, vRecv, connman);
            masternodeSync.ProcessMessage(pfrom, strCommand, vRecv);
            governance.ProcessMessage(pfrom, strCommand, vRecv, connman);
        }
        else
        {
            // Ignore unknown commands for extensibility
            LogPrint("net", "Unknown command \"%s\" from peer=%d\n", SanitizeString(strCommand), pfrom->id);
        }
    }

    return true;
}

bool ProcessMessages(CNode* pfrom, CConnman& connman, std::atomic<bool>& interruptMsgProc)
{
    const CChainParams& chainparams = Params();
    //
    // Message format
    //  (4) message start
    //  (12) command
    //  (4) size
    //  (4) checksum
    //  (x) data
    //
    bool fMoreWork = false;

    if (!pfrom->vRecvGetData.empty())
        ProcessGetData(pfrom, chainparams.GetConsensus(), connman, interruptMsgProc);

    if (pfrom->fDisconnect)
        return false;

    // this maintains the order of responses
    if (!pfrom->vRecvGetData.empty()) return true;

        // Don't bother if send buffer is too full to respond anyway
        if (pfrom->fPauseSend)
            return false;

        std::list<CNetMessage> msgs;
        {
            LOCK(pfrom->cs_vProcessMsg);
            if (pfrom->vProcessMsg.empty())
                return false;
            // Just take one message
            msgs.splice(msgs.begin(), pfrom->vProcessMsg, pfrom->vProcessMsg.begin());
            pfrom->nProcessQueueSize -= msgs.front().vRecv.size() + CMessageHeader::HEADER_SIZE;
            pfrom->fPauseRecv = pfrom->nProcessQueueSize > connman.GetReceiveFloodSize();
            fMoreWork = !pfrom->vProcessMsg.empty();
        }
        CNetMessage& msg(msgs.front());

        msg.SetVersion(pfrom->GetRecvVersion());
        // Scan for message start
        if (memcmp(msg.hdr.pchMessageStart, chainparams.MessageStart(), MESSAGE_START_SIZE) != 0) {
            LogPrintf("PROCESSMESSAGE: INVALID MESSAGESTART %s peer=%d\n", SanitizeString(msg.hdr.GetCommand()), pfrom->id);
            pfrom->fDisconnect = true;
            return false;
        }

        // Read header
        CMessageHeader& hdr = msg.hdr;
        if (!hdr.IsValid(chainparams.MessageStart()))
        {
            LogPrintf("PROCESSMESSAGE: ERRORS IN HEADER %s peer=%d\n", SanitizeString(hdr.GetCommand()), pfrom->id);
            return fMoreWork;
        }
        string strCommand = hdr.GetCommand();

        // Message size
        unsigned int nMessageSize = hdr.nMessageSize;

        // Checksum
        CDataStream& vRecv = msg.vRecv;
        uint256 hash = Hash(vRecv.begin(), vRecv.begin() + nMessageSize);
        if (memcmp(hash.begin(), hdr.pchChecksum, CMessageHeader::CHECKSUM_SIZE) != 0)
        {
            LogPrintf("%s(%s, %u bytes): CHECKSUM ERROR expected %s was %s\n", __func__,
               SanitizeString(strCommand), nMessageSize,
               HexStr(hash.begin(), hash.begin()+CMessageHeader::CHECKSUM_SIZE),
               HexStr(hdr.pchChecksum, hdr.pchChecksum+CMessageHeader::CHECKSUM_SIZE));
            return fMoreWork;
        }

        // Process message
        bool fRet = false;
        try
        {
            fRet = ProcessMessage(pfrom, strCommand, vRecv, msg.nTime, connman, interruptMsgProc);
            if (interruptMsgProc)
                return false;
            if (!pfrom->vRecvGetData.empty())
                fMoreWork = true;
        }
        catch (const std::ios_base::failure& e)
        {
            connman.PushMessageWithVersion(pfrom, INIT_PROTO_VERSION, NetMsgType::REJECT, strCommand, REJECT_MALFORMED, string("error parsing message"));
            if (strstr(e.what(), "end of data"))
            {
                // Allow exceptions from under-length message on vRecv
                LogPrintf("%s(%s, %u bytes): Exception '%s' caught, normally caused by a message being shorter than its stated length\n", __func__, SanitizeString(strCommand), nMessageSize, e.what());
            }
            else if (strstr(e.what(), "size too large"))
            {
                // Allow exceptions from over-long size
                LogPrintf("%s(%s, %u bytes): Exception '%s' caught\n", __func__, SanitizeString(strCommand), nMessageSize, e.what());
            }
            else
            {
                PrintExceptionContinue(&e, "ProcessMessages()");
            }
        }
        catch (const std::exception& e) {
            PrintExceptionContinue(&e, "ProcessMessages()");
        } catch (...) {
            PrintExceptionContinue(NULL, "ProcessMessages()");
        }

        if (!fRet)
            LogPrintf("%s(%s, %u bytes) FAILED peer=%d\n", __func__, SanitizeString(strCommand), nMessageSize, pfrom->id);

    return fMoreWork;
}


bool SendMessages(CNode* pto, CConnman& connman, std::atomic<bool>& interruptMsgProc)
{
    const CChainParams chainParams = Params();
    const Consensus::Params& consensusParams = chainParams.GetConsensus();
    {
        // Don't send anything until the version handshake is complete
        if (!pto->fSuccessfullyConnected || pto->fDisconnect)
            return true;

        //
        // Message: ping
        //
        bool pingSend = false;
        if (pto->fPingQueued) {
            // RPC ping request by user
            pingSend = true;
        }
        if (pto->nPingNonceSent == 0 && pto->nPingUsecStart + PING_INTERVAL * 1000000 < GetTimeMicros()) {
            // Ping automatically sent as a latency probe & keepalive.
            pingSend = true;
        }
        if (pingSend) {
            uint64_t nonce = 0;
            while (nonce == 0) {
                GetRandBytes((unsigned char*)&nonce, sizeof(nonce));
            }
            pto->fPingQueued = false;
            pto->nPingUsecStart = GetTimeMicros();
            if (pto->nVersion > BIP0031_VERSION) {
                pto->nPingNonceSent = nonce;
                connman.PushMessage(pto, NetMsgType::PING, nonce);
            } else {
                // Peer is too old to support ping command with nonce, pong will never arrive.
                pto->nPingNonceSent = 0;
                connman.PushMessage(pto, NetMsgType::PING);
            }
        }

        TRY_LOCK(cs_main, lockMain); // Acquire cs_main for IsInitialBlockDownload() and CNodeState()
        if (!lockMain)
            return true;

        // Address refresh broadcast
        int64_t nNow = GetTimeMicros();
        if (!IsInitialBlockDownload() && pto->nNextLocalAddrSend < nNow) {
            AdvertiseLocal(pto);
            pto->nNextLocalAddrSend = PoissonNextSend(nNow, AVG_LOCAL_ADDRESS_BROADCAST_INTERVAL);
        }

        //
        // Message: addr
        //
        if (pto->nNextAddrSend < nNow) {
            pto->nNextAddrSend = PoissonNextSend(nNow, AVG_ADDRESS_BROADCAST_INTERVAL);
            vector<CAddress> vAddr;
            vAddr.reserve(pto->vAddrToSend.size());
            BOOST_FOREACH(const CAddress& addr, pto->vAddrToSend)
            {
                if (!pto->addrKnown.contains(addr.GetKey()))
                {
                    pto->addrKnown.insert(addr.GetKey());
                    vAddr.push_back(addr);
                    // receiver rejects addr messages larger than 1000
                    if (vAddr.size() >= 1000)
                    {
                        connman.PushMessage(pto, NetMsgType::ADDR, vAddr);
                        vAddr.clear();
                    }
                }
            }
            pto->vAddrToSend.clear();
            if (!vAddr.empty())
                connman.PushMessage(pto, NetMsgType::ADDR, vAddr);
        }

        CNodeState &state = *State(pto->GetId());
        if (state.fShouldBan) {
            if (pto->fWhitelisted)
                LogPrintf("Warning: not punishing whitelisted peer %s!\n", pto->addr.ToString());
            else {
                pto->fDisconnect = true;
                if (pto->addr.IsLocal())
                    LogPrintf("Warning: not banning local peer %s!\n", pto->addr.ToString());
                else
                {
                    connman.Ban(pto->addr, BanReasonNodeMisbehaving);
                }
            }
            state.fShouldBan = false;
        }

        BOOST_FOREACH(const CBlockReject& reject, state.rejects)
            connman.PushMessage(pto, NetMsgType::REJECT, (string)NetMsgType::BLOCK, reject.chRejectCode, reject.strRejectReason, reject.hashBlock);
        state.rejects.clear();

        // Start block sync
        if (pindexBestHeader == NULL)
            pindexBestHeader = chainActive.Tip();
        bool fFetch = state.fPreferredDownload || (nPreferredDownload == 0 && !pto->fClient && !pto->fOneShot); // Download if this is a nice peer, or we have no nice peers and this one might do.
        if (!state.fSyncStarted && !pto->fClient && !fImporting && !fReindex) {
            // Only actively request headers from a single peer, unless we're close to end of initial download.
            if ((nSyncStarted == 0 && fFetch) || pindexBestHeader->GetBlockTime() > GetAdjustedTime() - 6 * 60 * 60) { // NOTE: was "close to today" and 24h in Bitcoin
                state.fSyncStarted = true;
                state.nHeadersSyncTimeout = GetTimeMicros() + HEADERS_DOWNLOAD_TIMEOUT_BASE + HEADERS_DOWNLOAD_TIMEOUT_PER_HEADER * (GetAdjustedTime() - pindexBestHeader->GetBlockTime())/(consensusParams.nPowTargetSpacing);
                nSyncStarted++;
                const CBlockIndex *pindexStart = pindexBestHeader;
                /* If possible, start at the block preceding the currently
                   best known header.  This ensures that we always get a
                   non-empty list of headers back as long as the peer
                   is up-to-date.  With a non-empty response, we can initialise
                   the peer's known best block.  This wouldn't be possible
                   if we requested starting at pindexBestHeader and
                   got back an empty response.  */
                if (pindexStart->pprev)
                    pindexStart = pindexStart->pprev;
                LogPrint("net", "initial getheaders (%d) to peer=%d (startheight:%d)\n", pindexStart->nHeight, pto->id, pto->nStartingHeight);
                connman.PushMessage(pto, NetMsgType::GETHEADERS, chainActive.GetLocator(pindexStart), uint256());
            }
        }

        if (chainParams.DelayGetHeadersTime() != 0 && pindexBestHeader->GetBlockTime() >= GetAdjustedTime() - chainParams.DelayGetHeadersTime()) {
            // Headers chain has catched up enough so we can send out GETHEADER messages which were initially meant to
            // be sent directly after INV was received
            LOCK(pto->cs_inventory);
            BOOST_FOREACH(const uint256 &hash, pto->vBlockHashesFromINV) {
                LogPrint("net", "process delayed getheaders (%d) to peer=%d\n", pindexBestHeader->nHeight, pto->id);
                connman.PushMessage(pto, NetMsgType::GETHEADERS, chainActive.GetLocator(pindexBestHeader), hash);
            }
            pto->vBlockHashesFromINV.clear();
        }

        // Resend wallet transactions that haven't gotten in a block yet
        // Except during reindex, importing and IBD, when old wallet
        // transactions become unconfirmed and spams other nodes.
        if (!fReindex && !fImporting && !IsInitialBlockDownload())
        {
            GetMainSignals().Broadcast(nTimeBestReceived, &connman);
        }

        //
        // Try sending block announcements via headers
        //
        {
            // If we have less than MAX_BLOCKS_TO_ANNOUNCE in our
            // list of block hashes we're relaying, and our peer wants
            // headers announcements, then find the first header
            // not yet known to our peer but would connect, and send.
            // If no header would connect, or if we have too many
            // blocks, or if the peer doesn't want headers, just
            // add all to the inv queue.
            LOCK(pto->cs_inventory);
            vector<CBlock> vHeaders;
            bool fRevertToInv = (!state.fPreferHeaders || pto->vBlockHashesToAnnounce.size() > MAX_BLOCKS_TO_ANNOUNCE);
            CBlockIndex *pBestIndex = NULL; // last header queued for delivery
            ProcessBlockAvailability(pto->id); // ensure pindexBestKnownBlock is up-to-date

            if (!fRevertToInv) {
                bool fFoundStartingHeader = false;
                // Try to find first header that our peer doesn't have, and
                // then send all headers past that one.  If we come across any
                // headers that aren't on chainActive, give up.
                BOOST_FOREACH(const uint256 &hash, pto->vBlockHashesToAnnounce) {
                    BlockMap::iterator mi = mapBlockIndex.find(hash);
                    assert(mi != mapBlockIndex.end());
                    CBlockIndex *pindex = mi->second;
                    if (chainActive[pindex->nHeight] != pindex) {
                        // Bail out if we reorged away from this block
                        fRevertToInv = true;
                        break;
                    }
                    if (pBestIndex != NULL && pindex->pprev != pBestIndex) {
                        // This means that the list of blocks to announce don't
                        // connect to each other.
                        // This shouldn't really be possible to hit during
                        // regular operation (because reorgs should take us to
                        // a chain that has some block not on the prior chain,
                        // which should be caught by the prior check), but one
                        // way this could happen is by using invalidateblock /
                        // reconsiderblock repeatedly on the tip, causing it to
                        // be added multiple times to vBlockHashesToAnnounce.
                        // Robustly deal with this rare situation by reverting
                        // to an inv.
                        fRevertToInv = true;
                        break;
                    }
                    pBestIndex = pindex;
                    if (fFoundStartingHeader) {
                        // add this to the headers message
                        vHeaders.push_back(pindex->GetBlockHeader());
                    } else if (PeerHasHeader(&state, pindex)) {
                        continue; // keep looking for the first new block
                    } else if (pindex->pprev == NULL || PeerHasHeader(&state, pindex->pprev)) {
                        // Peer doesn't have this header but they do have the prior one.
                        // Start sending headers.
                        fFoundStartingHeader = true;
                        vHeaders.push_back(pindex->GetBlockHeader());
                    } else {
                        // Peer doesn't have this header or the prior one -- nothing will
                        // connect, so bail out.
                        fRevertToInv = true;
                        break;
                    }
                }
            }
            if (fRevertToInv) {
                // If falling back to using an inv, just try to inv the tip.
                // The last entry in vBlockHashesToAnnounce was our tip at some point
                // in the past.
                if (!pto->vBlockHashesToAnnounce.empty()) {
                    const uint256 &hashToAnnounce = pto->vBlockHashesToAnnounce.back();
                    BlockMap::iterator mi = mapBlockIndex.find(hashToAnnounce);
                    assert(mi != mapBlockIndex.end());
                    CBlockIndex *pindex = mi->second;

                    // Warn if we're announcing a block that is not on the main chain.
                    // This should be very rare and could be optimized out.
                    // Just log for now.
                    if (chainActive[pindex->nHeight] != pindex) {
                        LogPrint("net", "Announcing block %s not on main chain (tip=%s)\n",
                            hashToAnnounce.ToString(), chainActive.Tip()->GetBlockHash().ToString());
                    }

                    // If the peer announced this block to us, don't inv it back.
                    // (Since block announcements may not be via inv's, we can't solely rely on
                    // setInventoryKnown to track this.)
                    if (!PeerHasHeader(&state, pindex)) {
                        pto->PushInventory(CInv(MSG_BLOCK, hashToAnnounce));
                        LogPrint("net", "%s: sending inv peer=%d hash=%s\n", __func__,
                            pto->id, hashToAnnounce.ToString());
                    }
                }
            } else if (!vHeaders.empty()) {
                if (vHeaders.size() > 1) {
                    LogPrint("net", "%s: %u headers, range (%s, %s), to peer=%d\n", __func__,
                            vHeaders.size(),
                            vHeaders.front().GetHash().ToString(),
                            vHeaders.back().GetHash().ToString(), pto->id);
                } else {
                    LogPrint("net", "%s: sending header %s to peer=%d\n", __func__,
                            vHeaders.front().GetHash().ToString(), pto->id);
                }
                connman.PushMessage(pto, NetMsgType::HEADERS, vHeaders);
                state.pindexBestHeaderSent = pBestIndex;
            }
            pto->vBlockHashesToAnnounce.clear();
        }

        //
        // Message: inventory
        //
        vector<CInv> vInv;
        vector<CInv> vInvWait;
        {
            bool fSendTrickle = pto->fWhitelisted;
            if (pto->nNextInvSend < nNow) {
                fSendTrickle = true;
                pto->nNextInvSend = PoissonNextSend(nNow, AVG_INVENTORY_BROADCAST_INTERVAL);
            }
            LOCK(pto->cs_inventory);
            vInv.reserve(std::min<size_t>(1000, pto->vInventoryToSend.size()));
            vInvWait.reserve(pto->vInventoryToSend.size());
            BOOST_FOREACH(const CInv& inv, pto->vInventoryToSend)
            {
                if (inv.type == MSG_TX && pto->filterInventoryKnown.contains(inv.hash))
                    continue;

                // trickle out tx inv to protect privacy
                if (inv.type == MSG_TX && !fSendTrickle)
                {
                    // 1/4 of tx invs blast to all immediately
                    static uint256 hashSalt;
                    if (hashSalt.IsNull())
                        hashSalt = GetRandHash();
                    uint256 hashRand = ArithToUint256(UintToArith256(inv.hash) ^ UintToArith256(hashSalt));
                    hashRand = Hash(BEGIN(hashRand), END(hashRand));
                    bool fTrickleWait = ((UintToArith256(hashRand) & 3) != 0);

                    if (fTrickleWait)
                    {
                        LogPrint("net", "SendMessages -- queued inv(vInvWait): %s  index=%d peer=%d\n", inv.ToString(), vInvWait.size(), pto->id);
                        vInvWait.push_back(inv);
                        continue;
                    }
                }

                pto->filterInventoryKnown.insert(inv.hash);

                LogPrint("net", "SendMessages -- queued inv: %s  index=%d peer=%d\n", inv.ToString(), vInv.size(), pto->id);
                vInv.push_back(inv);
                if (vInv.size() >= 1000)
                {
                    LogPrint("net", "SendMessages -- pushing inv's: count=%d peer=%d\n", vInv.size(), pto->id);
                    connman.PushMessage(pto, NetMsgType::INV, vInv);
                    vInv.clear();
                }
            }
            pto->vInventoryToSend = vInvWait;
        }
        if (!vInv.empty()) {
            LogPrint("net", "SendMessages -- pushing tailing inv's: count=%d peer=%d\n", vInv.size(), pto->id);
            connman.PushMessage(pto, NetMsgType::INV, vInv);
        }

        // Detect whether we're stalling
        nNow = GetTimeMicros();
        if (!pto->fDisconnect && state.nStallingSince && state.nStallingSince < nNow - 1000000 * BLOCK_STALLING_TIMEOUT) {
            // Stalling only triggers when the block download window cannot move. During normal steady state,
            // the download window should be much larger than the to-be-downloaded set of blocks, so disconnection
            // should only happen during initial block download.
            LogPrintf("Peer=%d is stalling block download, disconnecting\n", pto->id);
            pto->fDisconnect = true;
        }
        // In case there is a block that has been in flight from this peer for 2 + 0.5 * N times the block interval
        // (with N the number of peers from which we're downloading validated blocks), disconnect due to timeout.
        // We compensate for other peers to prevent killing off peers due to our own downstream link
        // being saturated. We only count validated in-flight blocks so peers can't advertise non-existing block hashes
        // to unreasonably increase our timeout.
        if (!pto->fDisconnect && state.vBlocksInFlight.size() > 0) {
            QueuedBlock &queuedBlock = state.vBlocksInFlight.front();
            int nOtherPeersWithValidatedDownloads = nPeersWithValidatedDownloads - (state.nBlocksInFlightValidHeaders > 0);
            if (nNow > state.nDownloadingSince + consensusParams.nPowTargetSpacing * (BLOCK_DOWNLOAD_TIMEOUT_BASE + BLOCK_DOWNLOAD_TIMEOUT_PER_PEER * nOtherPeersWithValidatedDownloads)) {
                LogPrintf("Timeout downloading block %s from peer=%d, disconnecting\n", queuedBlock.hash.ToString(), pto->id);
                pto->fDisconnect = true;
            }
        }
        // Check for headers sync timeouts
        if (state.fSyncStarted && state.nHeadersSyncTimeout < std::numeric_limits<int64_t>::max()) {
            // Detect whether this is a stalling initial-headers-sync peer
            if (pindexBestHeader->GetBlockTime() <= GetAdjustedTime() - 6*60*60) { // was 24*60*60 in bitcoin
                if (nNow > state.nHeadersSyncTimeout && nSyncStarted == 1 && (nPreferredDownload - state.fPreferredDownload >= 1)) {
                    // Disconnect a (non-whitelisted) peer if it is our only sync peer,
                    // and we have others we could be using instead.
                    // Note: If all our peers are inbound, then we won't
                    // disconnect our sync peer for stalling; we have bigger
                    // problems if we can't get any outbound peers.
                    if (!pto->fWhitelisted) {
                        LogPrintf("Timeout downloading headers from peer=%d, disconnecting\n", pto->GetId());
                        pto->fDisconnect = true;
                        return true;
                    } else {
                        LogPrintf("Timeout downloading headers from whitelisted peer=%d, not disconnecting\n", pto->GetId());
                        // Reset the headers sync state so that we have a
                        // chance to try downloading from a different peer.
                        // Note: this will also result in at least one more
                        // getheaders message to be sent to
                        // this peer (eventually).
                        state.fSyncStarted = false;
                        nSyncStarted--;
                        state.nHeadersSyncTimeout = 0;
                    }
                }
            } else {
                // After we've caught up once, reset the timeout so we can't trigger
                // disconnect later.
                state.nHeadersSyncTimeout = std::numeric_limits<int64_t>::max();
            }
        }


        //
        // Message: getdata (blocks)
        //
        vector<CInv> vGetData;
        if (!pto->fDisconnect && !pto->fClient && (fFetch || !IsInitialBlockDownload()) && state.nBlocksInFlight < MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
            vector<CBlockIndex*> vToDownload;
            NodeId staller = -1;
            FindNextBlocksToDownload(pto->GetId(), MAX_BLOCKS_IN_TRANSIT_PER_PEER - state.nBlocksInFlight, vToDownload, staller, consensusParams);
            BOOST_FOREACH(CBlockIndex *pindex, vToDownload) {
                vGetData.push_back(CInv(MSG_BLOCK, pindex->GetBlockHash()));
                MarkBlockAsInFlight(pto->GetId(), pindex->GetBlockHash(), consensusParams, pindex);
                LogPrint("net", "Requesting block %s (%d) peer=%d\n", pindex->GetBlockHash().ToString(),
                    pindex->nHeight, pto->id);
            }
            if (state.nBlocksInFlight == 0 && staller != -1) {
                if (State(staller)->nStallingSince == 0) {
                    State(staller)->nStallingSince = nNow;
                    LogPrint("net", "Stall started peer=%d\n", staller);
                }
            }
        }

        //
        // Message: getdata (non-blocks)
        //
        while (!pto->fDisconnect && !pto->mapAskFor.empty() && (*pto->mapAskFor.begin()).first <= nNow)
        {
            const CInv& inv = (*pto->mapAskFor.begin()).second;
            if (!AlreadyHave(inv))
            {
                LogPrint("net", "SendMessages -- GETDATA -- requesting inv = %s peer=%d\n", inv.ToString(), pto->id);
                vGetData.push_back(inv);
                if (vGetData.size() >= 1000)
                {
                    connman.PushMessage(pto, NetMsgType::GETDATA, vGetData);
                    LogPrint("net", "SendMessages -- GETDATA -- pushed size = %lu peer=%d\n", vGetData.size(), pto->id);
                    vGetData.clear();
                }
            } else {
                //If we're not going to ask, don't expect a response.
                LogPrint("net", "SendMessages -- GETDATA -- already have inv = %s peer=%d\n", inv.ToString(), pto->id);
                pto->setAskFor.erase(inv.hash);
            }
            pto->mapAskFor.erase(pto->mapAskFor.begin());
        }
        if (!vGetData.empty()) {
            connman.PushMessage(pto, NetMsgType::GETDATA, vGetData);
            LogPrint("net", "SendMessages -- GETDATA -- pushed size = %lu peer=%d\n", vGetData.size(), pto->id);
        }

    }
    return true;
}

class CNetProcessingCleanup
{
public:
    CNetProcessingCleanup() {}
    ~CNetProcessingCleanup() {
        // orphan transactions
        mapOrphanTransactions.clear();
        mapOrphanTransactionsByPrev.clear();
    }
} instance_of_cnetprocessingcleanup;