net.cpp

// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2015 The Bitcoin developers
// Copyright (c) 2014-2015 The Dash developers
// Copyright (c) 2015-2020 The PIVX developers
// Distributed under the MIT/X11 software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#if defined(HAVE_CONFIG_H)
#include "config/pivx-config.h"
#endif

#include "net.h"

#include "chainparams.h"
#include "clientversion.h"
#include "crypto/common.h"
#include "crypto/sha256.h"
#include "guiinterface.h"
#include "netbase.h"
#include "netmessagemaker.h"
#include "primitives/transaction.h"
#include "scheduler.h"
#include "validation.h"

#ifdef WIN32
#include <string.h>
#else
#include <fcntl.h>
#endif

#if HAVE_DECL_GETIFADDRS && HAVE_DECL_FREEIFADDRS
#include <ifaddrs.h>
#endif

#include <cstdint>

#include <math.h>

// Dump addresses to peers.dat and banlist.dat every 15 minutes (900s)
#define DUMP_ADDRESSES_INTERVAL 900

// We add a random period time (0 to 1 seconds) to feeler connections to prevent synchronization.
#define FEELER_SLEEP_WINDOW 1

#if !defined(HAVE_MSG_NOSIGNAL) && !defined(MSG_NOSIGNAL)
#define MSG_NOSIGNAL 0
#endif

// Fix for ancient MinGW versions, that don't have defined these in ws2tcpip.h.
// Todo: Can be removed when our pull-tester is upgraded to a modern MinGW version.
#ifdef WIN32
#ifndef PROTECTION_LEVEL_UNRESTRICTED
#define PROTECTION_LEVEL_UNRESTRICTED 10
#endif
#ifndef IPV6_PROTECTION_LEVEL
#define IPV6_PROTECTION_LEVEL 23
#endif
#endif

const static std::string NET_MESSAGE_COMMAND_OTHER = "*other*";

static const uint64_t RANDOMIZER_ID_NETGROUP = 0x6c0edd8036ef4036ULL; // SHA256("netgroup")[0:8]
static const uint64_t RANDOMIZER_ID_LOCALHOSTNONCE = 0xd93e69e2bbfa5735ULL; // SHA256("localhostnonce")[0:8]
//
// Global state variables
//
bool fDiscover = true;
bool fListen = true;
RecursiveMutex cs_mapLocalHost;
std::map<CNetAddr, LocalServiceInfo> mapLocalHost;
static bool vfLimited[NET_MAX] = {};
static CNode* pnodeLocalHost = NULL;
std::string strSubVersion;

limitedmap<CInv, int64_t> mapAlreadyAskedFor(MAX_INV_SZ);

void CConnman::AddOneShot(const std::string& strDest)
{
    LOCK(cs_vOneShots);
    vOneShots.push_back(strDest);
}

uint16_t GetListenPort()
{
    return (uint16_t)(gArgs.GetArg("-port", Params().GetDefaultPort()));
}

// find 'best' local address for a particular peer
bool GetLocal(CService& addr, const CNetAddr* paddrPeer)
{
    if (!fListen)
        return false;

    int nBestScore = -1;
    int nBestReachability = -1;
    {
        LOCK(cs_mapLocalHost);
        for (const auto& entry : mapLocalHost) {
            int nScore = entry.second.nScore;
            int nReachability = entry.first.GetReachabilityFrom(paddrPeer);
            if (nReachability > nBestReachability || (nReachability == nBestReachability && nScore > nBestScore)) {
                addr = CService(entry.first, entry.second.nPort);
                nBestReachability = nReachability;
                nBestScore = nScore;
            }
        }
    }
    return nBestScore >= 0;
}

//! Convert the pnSeeds6 array into usable address objects.
static std::vector<CAddress> convertSeed6(const std::vector<SeedSpec6>& vSeedsIn)
{
    // It'll only connect to one or two seed nodes because once it connects,
    // it'll get a pile of addresses with newer timestamps.
    // Seed nodes are given a random 'last seen time' of between one and two
    // weeks ago.
    const int64_t nOneWeek = 7 * 24 * 60 * 60;
    std::vector<CAddress> vSeedsOut;
    vSeedsOut.reserve(vSeedsIn.size());
    FastRandomContext rng;
    for (const auto& seed_in : vSeedsIn) {
        struct in6_addr ip;
        memcpy(&ip, seed_in.addr, sizeof(ip));
        CAddress addr(CService(ip, seed_in.port), NODE_NETWORK);
        addr.nTime = GetTime() - rng.randrange(nOneWeek) - nOneWeek;
        vSeedsOut.push_back(addr);
    }
    return vSeedsOut;
}

// get best local address for a particular peer as a CAddress
// Otherwise, return the unroutable 0.0.0.0 but filled in with
// the normal parameters, since the IP may be changed to a useful
// one by discovery.
CAddress GetLocalAddress(const CNetAddr* paddrPeer, ServiceFlags nLocalServices)
{
    CAddress ret(CService(CNetAddr(), GetListenPort()), nLocalServices);
    CService addr;
    if (GetLocal(addr, paddrPeer)) {
        ret = CAddress(addr, nLocalServices);
    }
    ret.nTime = GetAdjustedTime();
    return ret;
}

int GetnScore(const CService& addr)
{
    LOCK(cs_mapLocalHost);
    if (mapLocalHost.count(addr) == LOCAL_NONE)
        return 0;
    return mapLocalHost[addr].nScore;
}

// Is our peer's addrLocal potentially useful as an external IP source?
bool IsPeerAddrLocalGood(CNode* pnode)
{
    CService addrLocal = pnode->GetAddrLocal();
    return fDiscover && pnode->addr.IsRoutable() && addrLocal.IsRoutable() &&
           !IsLimited(addrLocal.GetNetwork());
}

// pushes our own address to a peer
void AdvertiseLocal(CNode* pnode)
{
    if (fListen && pnode->fSuccessfullyConnected) {
        CAddress addrLocal = GetLocalAddress(&pnode->addr, pnode->GetLocalServices());
        // If discovery is enabled, sometimes give our peer the address it
        // tells us that it sees us as in case it has a better idea of our
        // address than we do.
        FastRandomContext rng;
        if (IsPeerAddrLocalGood(pnode) && (!addrLocal.IsRoutable() ||
             rng.randbits((GetnScore(addrLocal) > LOCAL_MANUAL) ? 3 : 1) == 0)) {
            addrLocal.SetIP(pnode->GetAddrLocal());
        }
        if (addrLocal.IsRoutable()) {
            LogPrintf("%s: advertising address %s\n", __func__, addrLocal.ToString());
            pnode->PushAddress(addrLocal, rng);
        }
    }
}

// learn a new local address
bool AddLocal(const CService& addr, int nScore)
{
    if (!addr.IsRoutable())
        return false;

    if (!fDiscover && nScore < LOCAL_MANUAL)
        return false;

    if (IsLimited(addr))
        return false;

    LogPrintf("AddLocal(%s,%i)\n", addr.ToString(), nScore);

    {
        LOCK(cs_mapLocalHost);
        bool fAlready = mapLocalHost.count(addr) > 0;
        LocalServiceInfo& info = mapLocalHost[addr];
        if (!fAlready || nScore >= info.nScore) {
            info.nScore = nScore + (fAlready ? 1 : 0);
            info.nPort = addr.GetPort();
        }
    }

    return true;
}

bool AddLocal(const CNetAddr& addr, int nScore)
{
    return AddLocal(CService(addr, GetListenPort()), nScore);
}

bool RemoveLocal(const CService& addr)
{
    LOCK(cs_mapLocalHost);
    LogPrintf("RemoveLocal(%s)\n", addr.ToString());
    mapLocalHost.erase(addr);
    return true;
}

/** Make a particular network entirely off-limits (no automatic connects to it) */
void SetLimited(enum Network net, bool fLimited)
{
    if (net == NET_UNROUTABLE || net == NET_INTERNAL)
        return;
    LOCK(cs_mapLocalHost);
    vfLimited[net] = fLimited;
}

bool IsLimited(enum Network net)
{
    LOCK(cs_mapLocalHost);
    return vfLimited[net];
}

bool IsLimited(const CNetAddr& addr)
{
    return IsLimited(addr.GetNetwork());
}

/** vote for a local address */
bool SeenLocal(const CService& addr)
{
    {
        LOCK(cs_mapLocalHost);
        if (mapLocalHost.count(addr) == 0)
            return false;
        mapLocalHost[addr].nScore++;
    }
    return true;
}


/** check whether a given address is potentially local */
bool IsLocal(const CService& addr)
{
    LOCK(cs_mapLocalHost);
    return mapLocalHost.count(addr) > 0;
}

/** check whether a given network is one we can probably connect to */
bool IsReachable(enum Network net)
{
    LOCK(cs_mapLocalHost);
    return !vfLimited[net];
}

/** check whether a given address is in a network we can probably connect to */
bool IsReachable(const CNetAddr& addr)
{
    enum Network net = addr.GetNetwork();
    return IsReachable(net);
}


CNode* CConnman::FindNode(const CNetAddr& ip)
{
    LOCK(cs_vNodes);
    for (CNode* pnode : vNodes) {
        if (static_cast<CNetAddr>(pnode->addr) == ip) {
            return pnode;
        }
    }
    return nullptr;
}

CNode* CConnman::FindNode(const CSubNet& subNet)
{
    LOCK(cs_vNodes);
    for (CNode* pnode : vNodes) {
        if (subNet.Match(static_cast<CNetAddr>(pnode->addr))) {
            return pnode;
        }
    }
    return nullptr;
}

CNode* CConnman::FindNode(const std::string& addrName)
{
    LOCK(cs_vNodes);
    for (CNode* pnode : vNodes) {
        if (pnode->GetAddrName() == addrName) {
            return pnode;
        }
    }
    return NULL;
}

CNode* CConnman::FindNode(const CService& addr)
{
    LOCK(cs_vNodes);
    const bool isRegTestNet = Params().IsRegTestNet();
    for (CNode* pnode : vNodes) {
        if (isRegTestNet) {
            //if using regtest, just check the IP
            if (static_cast<CNetAddr>(pnode->addr) == static_cast<CNetAddr>(addr))
                return pnode;
        } else {
            if (pnode->addr == addr)
                return pnode;
        }
    }
    return nullptr;
}

bool CConnman::CheckIncomingNonce(uint64_t nonce)
{
    LOCK(cs_vNodes);
    for(CNode* pnode : vNodes) {
        if (!pnode->fSuccessfullyConnected && !pnode->fInbound && pnode->GetLocalNonce() == nonce)
            return false;
    }
    return true;
}

CNode* CConnman::ConnectNode(CAddress addrConnect, const char* pszDest, bool fCountFailure)
{
    if (pszDest == NULL) {
        if (IsLocal(addrConnect)) {
            LogPrintf("%s: cannot connect to local node\n", __func__);
            return nullptr;
        }

        // Look for an existing connection
        CNode* pnode = FindNode(static_cast<CService>(addrConnect));
        if (pnode) {
            LogPrintf("Failed to open new connection, already connected\n");
            return nullptr;
        }
    }

    /// debug print
    LogPrint(BCLog::NET, "trying connection %s lastseen=%.1fhrs\n",
        pszDest ? pszDest : addrConnect.ToString(),
        pszDest ? 0.0 : (double)(GetAdjustedTime() - addrConnect.nTime) / 3600.0);

    // Connect
    SOCKET hSocket = INVALID_SOCKET;
    bool proxyConnectionFailed = false;
    if (pszDest ? ConnectSocketByName(addrConnect, hSocket, pszDest, Params().GetDefaultPort(), nConnectTimeout, &proxyConnectionFailed) :
                  ConnectSocket(addrConnect, hSocket, nConnectTimeout, &proxyConnectionFailed)) {
        if (!IsSelectableSocket(hSocket)) {
            LogPrintf("Cannot create connection: non-selectable socket created (fd >= FD_SETSIZE ?)\n");
            CloseSocket(hSocket);
            return NULL;
        }

        addrman.Attempt(addrConnect, fCountFailure);

        // Add node
        NodeId id = GetNewNodeId();
        uint64_t nonce = GetDeterministicRandomizer(RANDOMIZER_ID_LOCALHOSTNONCE).Write(id).Finalize();
        CNode* pnode = new CNode(id, nLocalServices, GetBestHeight(), hSocket, addrConnect, CalculateKeyedNetGroup(addrConnect), nonce, pszDest ? pszDest : "", false);
        pnode->nServicesExpected = ServiceFlags(addrConnect.nServices & nRelevantServices);
        pnode->fWhitelisted = IsWhitelistedRange(addrConnect);
        pnode->AddRef();

        // We're making a new connection, harvest entropy from the time (and our peer count)
        RandAddEvent((uint32_t)id);

        return pnode;
    } else if (!proxyConnectionFailed) {
        // If connecting to the node failed, and failure is not caused by a problem connecting to
        // the proxy, mark this as an attempt.
        addrman.Attempt(addrConnect, fCountFailure);
    }

    return NULL;
}

void CConnman::DumpBanlist()
{
    SweepBanned(); // clean unused entries (if bantime has expired)

    if (!BannedSetIsDirty())
        return;

    int64_t nStart = GetTimeMillis();

    CBanDB bandb;
    banmap_t banmap;
    SetBannedSetDirty(false);
    GetBanned(banmap);
    if (!bandb.Write(banmap))
        SetBannedSetDirty(true);

    LogPrint(BCLog::NET, "Flushed %d banned node ips/subnets to banlist.dat  %dms\n",
        banmap.size(), GetTimeMillis() - nStart);
}

void CNode::CloseSocketDisconnect()
{
    fDisconnect = true;
    LOCK(cs_hSocket);
    if (hSocket != INVALID_SOCKET) {
        LogPrint(BCLog::NET, "disconnecting peer=%d\n", id);
        CloseSocket(hSocket);
    }
}

bool CNode::DisconnectOldProtocol(int nVersionIn, int nVersionRequired)
{
    fDisconnect = false;
    if (nVersionIn < nVersionRequired) {
        LogPrintf("%s : peer=%d using obsolete version %i; disconnecting\n", __func__, id, nVersionIn);
        fDisconnect = true;
    }
    return fDisconnect;
}

void CConnman::ClearBanned()
{
    {
        LOCK(cs_setBanned);
        setBanned.clear();
        setBannedIsDirty = true;
    }
    DumpBanlist(); // store banlist to Disk
    if(clientInterface)
        clientInterface->BannedListChanged();
}

bool CConnman::IsBanned(CNetAddr ip)
{
    LOCK(cs_setBanned);
    for (const auto& it : setBanned) {
        CSubNet subNet = it.first;
        CBanEntry banEntry = it.second;

        if (subNet.Match(ip) && GetTime() < banEntry.nBanUntil) {
            return true;
        }
    }
    return false;
}

bool CConnman::IsBanned(CSubNet subnet)
{
    LOCK(cs_setBanned);
    banmap_t::iterator i = setBanned.find(subnet);
    if (i != setBanned.end()) {
        CBanEntry banEntry = (*i).second;
        if (GetTime() < banEntry.nBanUntil) {
            return true;
        }
    }
    return false;
}

void CConnman::Ban(const CNetAddr& addr, const BanReason &banReason, int64_t bantimeoffset, bool sinceUnixEpoch)
{
    CSubNet subNet(addr);
    Ban(subNet, banReason, bantimeoffset, sinceUnixEpoch);
}

void CConnman::Ban(const CSubNet& subNet, const BanReason &banReason, int64_t bantimeoffset, bool sinceUnixEpoch)
{
    CBanEntry banEntry(GetTime());
    banEntry.banReason = banReason;
    if (bantimeoffset <= 0)
    {
        bantimeoffset = gArgs.GetArg("-bantime", DEFAULT_MISBEHAVING_BANTIME); // Default 24-hour ban
        sinceUnixEpoch = false;
    }
    banEntry.nBanUntil = (sinceUnixEpoch ? 0 : GetTime() )+bantimeoffset;

    {
        LOCK(cs_setBanned);
        if (setBanned[subNet].nBanUntil < banEntry.nBanUntil) {
            setBanned[subNet] = banEntry;
            setBannedIsDirty = true;
        }
        else
            return;
    }
    if(clientInterface)
        clientInterface->BannedListChanged();
    {
        LOCK(cs_vNodes);
        for (CNode* pnode : vNodes) {
            if (subNet.Match(static_cast<CNetAddr>(pnode->addr)))
                pnode->fDisconnect = true;
        }
    }
    if(banReason == BanReasonManuallyAdded)
        DumpBanlist(); //store banlist to disk immediately if user requested ban
}

bool CConnman::Unban(const CNetAddr &addr)
{
    CSubNet subNet(addr);
    return Unban(subNet);
}

bool CConnman::Unban(const CSubNet &subNet)
{
    {
        LOCK(cs_setBanned);
        if (!setBanned.erase(subNet))
            return false;
        setBannedIsDirty = true;
    }
    if(clientInterface)
        clientInterface->BannedListChanged();
    DumpBanlist(); //store banlist to disk immediately
    return true;
}

void CConnman::GetBanned(banmap_t &banMap)
{
    LOCK(cs_setBanned);
    banMap = setBanned; //create a thread safe copy
}

void CConnman::SetBanned(const banmap_t &banMap)
{
    LOCK(cs_setBanned);
    setBanned = banMap;
    setBannedIsDirty = true;
}

void CConnman::SweepBanned()
{
    int64_t now = GetTime();

    bool notifyUI = false;
    {
        LOCK(cs_setBanned);
        banmap_t::iterator it = setBanned.begin();
        while(it != setBanned.end())
        {
            CSubNet subNet = (*it).first;
            CBanEntry banEntry = (*it).second;
            if(now > banEntry.nBanUntil)
            {
                setBanned.erase(it++);
                setBannedIsDirty = true;
                notifyUI = true;
                LogPrint(BCLog::NET, "%s: Removed banned node ip/subnet from banlist.dat: %s\n", __func__, subNet.ToString());
            }
            else
                ++it;
        }
    }
    // update UI
    if(notifyUI) {
        uiInterface.BannedListChanged();
    }
}

bool CConnman::BannedSetIsDirty()
{
    LOCK(cs_setBanned);
    return setBannedIsDirty;
}

void CConnman::SetBannedSetDirty(bool dirty)
{
    LOCK(cs_setBanned); //reuse setBanned lock for the isDirty flag
    setBannedIsDirty = dirty;
}


bool CConnman::IsWhitelistedRange(const CNetAddr& addr)
{
    LOCK(cs_vWhitelistedRange);
    for (const CSubNet& subnet : vWhitelistedRange) {
        if (subnet.Match(addr))
            return true;
    }
    return false;
}

void CConnman::AddWhitelistedRange(const CSubNet& subnet)
{
    LOCK(cs_vWhitelistedRange);
    vWhitelistedRange.push_back(subnet);
}


std::string CNode::GetAddrName() const {
    LOCK(cs_addrName);
    return addrName;
}

void CNode::MaybeSetAddrName(const std::string& addrNameIn) {
    LOCK(cs_addrName);
    if (addrName.empty()) {
        addrName = addrNameIn;
    }
}

CService CNode::GetAddrLocal() const {
    LOCK(cs_addrLocal);
    return addrLocal;
}

void CNode::SetAddrLocal(const CService& addrLocalIn) {
    LOCK(cs_addrLocal);
    if (addrLocal.IsValid()) {
        error("Addr local already set for node: %i. Refusing to change from %s to %s", id, addrLocal.ToString(), addrLocalIn.ToString());
    } else {
        addrLocal = addrLocalIn;
    }
}

#undef X
#define X(name) stats.name = name
void CNode::copyStats(CNodeStats& stats)
{
    stats.nodeid = this->GetId();
    X(nServices);
    X(nLastSend);
    X(nLastRecv);
    X(nTimeConnected);
    X(nTimeOffset);
    stats.addrName = GetAddrName();
    X(nVersion);
    {
        LOCK(cs_SubVer);
        X(cleanSubVer);
    }
    X(fInbound);
    X(nStartingHeight);
    {
        LOCK(cs_vSend);
        X(mapSendBytesPerMsgCmd);
        X(nSendBytes);
    }
    {
        LOCK(cs_vRecv);
        X(mapRecvBytesPerMsgCmd);
        X(nRecvBytes);
    }
    X(fWhitelisted);

    // It is common for nodes with good ping times to suddenly become lagged,
    // due to a new block arriving or other large transfer.
    // Merely reporting pingtime might fool the caller into thinking the node was still responsive,
    // since pingtime does not update until the ping is complete, which might take a while.
    // So, if a ping is taking an unusually long time in flight,
    // the caller can immediately detect that this is happening.
    int64_t nPingUsecWait = 0;
    if ((0 != nPingNonceSent) && (0 != nPingUsecStart)) {
        nPingUsecWait = GetTimeMicros() - nPingUsecStart;
    }

    // Raw ping time is in microseconds, but show it to user as whole seconds (PIVX users should be well used to small numbers with many decimal places by now :)
    stats.dPingTime = (((double)nPingUsecTime) / 1e6);
    stats.dPingWait = (((double)nPingUsecWait) / 1e6);

    // Leave string empty if addrLocal invalid (not filled in yet)
    CService addrLocalUnlocked = GetAddrLocal();
    stats.addrLocal = addrLocalUnlocked.IsValid() ? addrLocalUnlocked.ToString() : "";
}
#undef X

bool CNode::ReceiveMsgBytes(const char* pch, unsigned int nBytes, bool& complete)
{
    complete = false;
    int64_t nTimeMicros = GetTimeMicros();
    LOCK(cs_vRecv);
    nLastRecv = nTimeMicros / 1000000;
    nRecvBytes += nBytes;
    while (nBytes > 0) {
        // get current incomplete message, or create a new one
        if (vRecvMsg.empty() ||
            vRecvMsg.back().complete())
            vRecvMsg.emplace_back(Params().MessageStart(), SER_NETWORK, INIT_PROTO_VERSION);

        CNetMessage& msg = vRecvMsg.back();

        // absorb network data
        int handled;
        if (!msg.in_data)
            handled = msg.readHeader(pch, nBytes);
        else
            handled = msg.readData(pch, nBytes);

        if (handled < 0)
            return false;

        if (msg.in_data && msg.hdr.nMessageSize > MAX_PROTOCOL_MESSAGE_LENGTH) {
            LogPrint(BCLog::NET, "Oversized message from peer=%i, disconnecting\n", GetId());
            return false;
        }

        pch += handled;
        nBytes -= handled;

        if (msg.complete()) {

            // Store received bytes per message command
            // to prevent a memory DOS, only allow valid commands
            mapMsgCmdSize::iterator i = mapRecvBytesPerMsgCmd.find(msg.hdr.pchCommand);
            if (i == mapRecvBytesPerMsgCmd.end())
                i = mapRecvBytesPerMsgCmd.find(NET_MESSAGE_COMMAND_OTHER);
            assert(i != mapRecvBytesPerMsgCmd.end());
            i->second += msg.hdr.nMessageSize + CMessageHeader::HEADER_SIZE;

            msg.nTime = nTimeMicros;
            complete = true;
        }
    }

    return true;
}

void CNode::SetSendVersion(int nVersionIn)
{
    // Send version may only be changed in the version message, and
    // only one version message is allowed per session. We can therefore
    // treat this value as const and even atomic as long as it's only used
    // once a version message has been successfully processed. Any attempt to
    // set this twice is an error.
    if (nSendVersion != 0) {
        error("Send version already set for node: %i. Refusing to change from %i to %i", id, nSendVersion, nVersionIn);
    } else {
        nSendVersion = nVersionIn;
    }
}

int CNode::GetSendVersion() const
{
    // The send version should always be explicitly set to
    // INIT_PROTO_VERSION rather than using this value until SetSendVersion
    // has been called.
    if (nSendVersion == 0) {
        error("Requesting unset send version for node: %i. Using %i", id, INIT_PROTO_VERSION);
        return INIT_PROTO_VERSION;
    }
    return nSendVersion;
}

int CNetMessage::readHeader(const char* pch, unsigned int nBytes)
{
    // copy data to temporary parsing buffer
    unsigned int nRemaining = 24 - nHdrPos;
    unsigned int nCopy = std::min(nRemaining, nBytes);

    memcpy(&hdrbuf[nHdrPos], pch, nCopy);
    nHdrPos += nCopy;

    // if header incomplete, exit
    if (nHdrPos < 24)
        return nCopy;

    // deserialize to CMessageHeader
    try {
        hdrbuf >> hdr;
    } catch (const std::exception&) {
        return -1;
    }

    // reject messages larger than MAX_SIZE
    if (hdr.nMessageSize > MAX_SIZE)
        return -1;

    // switch state to reading message data
    in_data = true;

    return nCopy;
}

int CNetMessage::readData(const char* pch, unsigned int nBytes)
{
    unsigned int nRemaining = hdr.nMessageSize - nDataPos;
    unsigned int nCopy = std::min(nRemaining, nBytes);

    if (vRecv.size() < nDataPos + nCopy) {
        // Allocate up to 256 KiB ahead, but never more than the total message size.
        vRecv.resize(std::min(hdr.nMessageSize, nDataPos + nCopy + 256 * 1024));
    }

    hasher.Write((const unsigned char*)pch, nCopy);
    memcpy(&vRecv[nDataPos], pch, nCopy);
    nDataPos += nCopy;

    return nCopy;
}

const uint256& CNetMessage::GetMessageHash() const
{
    assert(complete());
    if (data_hash.IsNull())
        hasher.Finalize(data_hash.begin());
    return data_hash;
}

// requires LOCK(cs_vSend)
size_t CConnman::SocketSendData(CNode* pnode)
{
    auto it = pnode->vSendMsg.begin();
    size_t nSentSize = 0;

    while (it != pnode->vSendMsg.end()) {
        const auto& data = *it;
        assert(data.size() > pnode->nSendOffset);
        int nBytes = 0;
        {
            LOCK(pnode->cs_hSocket);
            if (pnode->hSocket == INVALID_SOCKET)
                break;
            nBytes = send(pnode->hSocket, reinterpret_cast<const char*>(data.data()) + pnode->nSendOffset, data.size() - pnode->nSendOffset, MSG_NOSIGNAL | MSG_DONTWAIT);
        }
        if (nBytes > 0) {
            pnode->nLastSend = GetSystemTimeInSeconds();
            pnode->nSendBytes += nBytes;
            pnode->nSendOffset += nBytes;
            nSentSize += nBytes;
            if (pnode->nSendOffset == data.size()) {
                pnode->nSendOffset = 0;
                pnode->nSendSize -= data.size();
                pnode->fPauseSend = pnode->nSendSize > nSendBufferMaxSize;
                it++;
            } else {
                // could not send full message; stop sending more
                break;
            }
        } else {
            if (nBytes < 0) {
                // error
                int nErr = WSAGetLastError();
                if (nErr != WSAEWOULDBLOCK && nErr != WSAEMSGSIZE && nErr != WSAEINTR && nErr != WSAEINPROGRESS) {
                    LogPrintf("socket send error %s\n", NetworkErrorString(nErr));
                    pnode->CloseSocketDisconnect();
                }
            }
            // couldn't send anything at all
            break;
        }
    }

    if (it == pnode->vSendMsg.end()) {
        assert(pnode->nSendOffset == 0);
        assert(pnode->nSendSize == 0);
    }
    pnode->vSendMsg.erase(pnode->vSendMsg.begin(), it);
    return nSentSize;
}

void CheckOffsetDisconnectedPeers(const CNetAddr& ip)
{
    int nConnections = 0;
    if (g_connman) {
        g_connman->ForEachNode([&nConnections](CNode* pnode) {
            if (pnode->fSuccessfullyConnected)
                nConnections++;
            if (nConnections == ENOUGH_CONNECTIONS)
                return;
        });
    }

    // Not enough connections. Insert peer.
    static std::set<CNetAddr> setOffsetDisconnectedPeers;
    setOffsetDisconnectedPeers.insert(ip);
    if (setOffsetDisconnectedPeers.size() >= MAX_TIMEOFFSET_DISCONNECTIONS) {
        // clear the set
        setOffsetDisconnectedPeers.clear();
        // Trigger the warning
        std::string strWarn1 = _("Peers are being disconnected due time differences.");
        std::string strWarn2 = _("Please check that your computer's date and time are correct! If your clock is wrong PIVX Core will not work properly.");

        LogPrintf("*** Warning: %s %s\n", strWarn1, strWarn2);

        static int64_t nLastGUINotif = 0;
        int64_t now = GetTime();
        if (nLastGUINotif + 40 < now) { // Notify the GUI if needed.
            nLastGUINotif = now;
            uiInterface.ThreadSafeMessageBox(strprintf("%s\n\n%s", strWarn1, strWarn2), _("Warning"), CClientUIInterface::MSG_ERROR);
        }
    }
}

struct NodeEvictionCandidate
{
    NodeId id;
    int64_t nTimeConnected;
    int64_t nMinPingUsecTime;
    CAddress addr;
    uint64_t nKeyedNetGroup;
};

static bool ReverseCompareNodeMinPingTime(const NodeEvictionCandidate &a, const NodeEvictionCandidate &b)
{
    return a.nMinPingUsecTime > b.nMinPingUsecTime;
}

static bool ReverseCompareNodeTimeConnected(const NodeEvictionCandidate &a, const NodeEvictionCandidate &b)
{
    return a.nTimeConnected > b.nTimeConnected;
}

static bool CompareNetGroupKeyed(const NodeEvictionCandidate &a, const NodeEvictionCandidate &b) {
    return a.nKeyedNetGroup < b.nKeyedNetGroup;
};

/** Try to find a connection to evict when the node is full.
 *  Extreme care must be taken to avoid opening the node to attacker
 *   triggered network partitioning.
 *  The strategy used here is to protect a small number of peers
 *   for each of several distinct characteristics which are difficult
 *   to forge.  In order to partition a node the attacker must be
 *   simultaneously better at all of them than honest peers.
 */
bool CConnman::AttemptToEvictConnection(bool fPreferNewConnection)
{
    std::vector<NodeEvictionCandidate> vEvictionCandidates;
    {
        LOCK(cs_vNodes);

        for (const CNode* node : vNodes) {
            if (node->fWhitelisted)
                continue;
            if (!node->fInbound)
                continue;
            if (node->fDisconnect)
                continue;
            NodeEvictionCandidate candidate = {node->id, node->nTimeConnected, node->nMinPingUsecTime, node->addr, node->nKeyedNetGroup};
            vEvictionCandidates.push_back(candidate);
        }
    }

    if (vEvictionCandidates.empty()) return false;

    // Protect connections with certain characteristics

    // Deterministically select 4 peers to protect by netgroup.
    // An attacker cannot predict which netgroups will be protected
    std::sort(vEvictionCandidates.begin(), vEvictionCandidates.end(), CompareNetGroupKeyed);
    vEvictionCandidates.erase(vEvictionCandidates.end() - std::min(4, static_cast<int>(vEvictionCandidates.size())), vEvictionCandidates.end());

    if (vEvictionCandidates.empty()) return false;

    // Protect the 8 nodes with the lowest minimum ping time.
    // An attacker cannot manipulate this metric without physically moving nodes closer to the target.
    std::sort(vEvictionCandidates.begin(), vEvictionCandidates.end(), ReverseCompareNodeMinPingTime);
    vEvictionCandidates.erase(vEvictionCandidates.end() - std::min(8, static_cast<int>(vEvictionCandidates.size())), vEvictionCandidates.end());

    if (vEvictionCandidates.empty()) return false;

    // Protect the half of the remaining nodes which have been connected the longest.
    // This replicates the non-eviction implicit behavior, and precludes attacks that start later.
    std::sort(vEvictionCandidates.begin(), vEvictionCandidates.end(), ReverseCompareNodeTimeConnected);
    vEvictionCandidates.erase(vEvictionCandidates.end() - static_cast<int>(vEvictionCandidates.size() / 2), vEvictionCandidates.end());

    if (vEvictionCandidates.empty()) return false;

    // Identify the network group with the most connections and youngest member.
    // (vEvictionCandidates is already sorted by reverse connect time)
    uint64_t naMostConnections;
    unsigned int nMostConnections = 0;
    int64_t nMostConnectionsTime = 0;
    std::map<uint64_t, std::vector<NodeEvictionCandidate> > mapAddrCounts;
    for (const NodeEvictionCandidate& node : vEvictionCandidates) {
        mapAddrCounts[node.nKeyedNetGroup].push_back(node);
        int64_t grouptime = mapAddrCounts[node.nKeyedNetGroup][0].nTimeConnected;
        size_t groupsize = mapAddrCounts[node.nKeyedNetGroup].size();
        if (groupsize > nMostConnections || (groupsize == nMostConnections && grouptime > nMostConnectionsTime)) {
            nMostConnections = groupsize;
            nMostConnectionsTime = grouptime;
            naMostConnections = node.nKeyedNetGroup;
        }
    }

    // Reduce to the network group with the most connections
    vEvictionCandidates = std::move(mapAddrCounts[naMostConnections]);

    // Do not disconnect peers if there is only 1 connection from their network group
    if (vEvictionCandidates.size() <= 1)
        // unless we prefer the new connection (for whitelisted peers)
        if (!fPreferNewConnection)
            return false;

    // Disconnect from the network group with the most connections
    NodeId evicted = vEvictionCandidates.front().id;
    LOCK(cs_vNodes);
    for (CNode* pnode : vNodes) {
        if (pnode->GetId() == evicted) {
            pnode->fDisconnect = true;
            return true;
        }
    }
    return false;
}

void CConnman::AcceptConnection(const ListenSocket& hListenSocket) {
    struct sockaddr_storage sockaddr;
    socklen_t len = sizeof(sockaddr);
    SOCKET hSocket = accept(hListenSocket.socket, (struct sockaddr*)&sockaddr, &len);
    CAddress addr;
    int nInbound = 0;
    int nMaxInbound = nMaxConnections - (nMaxOutbound + nMaxFeeler);
    assert(nMaxInbound > 0);

    if (hSocket != INVALID_SOCKET)
        if (!addr.SetSockAddr((const struct sockaddr*)&sockaddr))
            LogPrintf("Warning: Unknown socket family\n");

    bool whitelisted = hListenSocket.whitelisted || IsWhitelistedRange(addr);
    {
        LOCK(cs_vNodes);
        for (const CNode* pnode : vNodes) {
            if (pnode->fInbound) nInbound++;
        }
    }

    if (hSocket == INVALID_SOCKET) {
        int nErr = WSAGetLastError();
        if (nErr != WSAEWOULDBLOCK)
            LogPrintf("socket error accept failed: %s\n", NetworkErrorString(nErr));
        return;
    }

    if (!IsSelectableSocket(hSocket)) {
        LogPrintf("connection from %s dropped: non-selectable socket\n", addr.ToString());
        CloseSocket(hSocket);
        return;
    }

    if (IsBanned(addr) && !whitelisted) {
        LogPrint(BCLog::NET, "connection from %s dropped (banned)\n", addr.ToString());
        CloseSocket(hSocket);
        return;
    }

    if (nInbound >= nMaxConnections - MAX_OUTBOUND_CONNECTIONS) {
        if (!AttemptToEvictConnection(whitelisted)) {
            // No connection to evict, disconnect the new connection
            LogPrint(BCLog::NET, "failed to find an eviction candidate - connection dropped (full)\n");
            CloseSocket(hSocket);
            return;
        }
    }

    NodeId id = GetNewNodeId();
    uint64_t nonce = GetDeterministicRandomizer(RANDOMIZER_ID_LOCALHOSTNONCE).Write(id).Finalize();

    CNode* pnode = new CNode(id, nLocalServices, GetBestHeight(), hSocket, addr, CalculateKeyedNetGroup(addr), nonce, "", true);
    pnode->AddRef();
    pnode->fWhitelisted = whitelisted;
    m_msgproc->InitializeNode(pnode);

    LogPrint(BCLog::NET, "connection from %s accepted\n", addr.ToString());

    {
        LOCK(cs_vNodes);
        vNodes.push_back(pnode);
    }

    // We received a new connection, harvest entropy from the time (and our peer count)
    RandAddEvent((uint32_t)id);
}

void CConnman::ThreadSocketHandler()
{
    unsigned int nPrevNodeCount = 0;
    while (!interruptNet) {
        //
        // Disconnect nodes
        //
        {
            LOCK(cs_vNodes);
            // Disconnect unused nodes
            std::vector<CNode*> vNodesCopy = vNodes;
            for (CNode* pnode : vNodesCopy) {
                if (pnode->fDisconnect) {
                    // remove from vNodes
                    vNodes.erase(remove(vNodes.begin(), vNodes.end(), pnode), vNodes.end());

                    // release outbound grant (if any)
                    pnode->grantOutbound.Release();

                    // close socket and cleanup
                    pnode->CloseSocketDisconnect();

                    // hold in disconnected pool until all refs are released
                    if (pnode->fNetworkNode || pnode->fInbound)
                        pnode->Release();
                    vNodesDisconnected.push_back(pnode);
                }
            }
        }
        {
            // Delete disconnected nodes
            std::list<CNode*> vNodesDisconnectedCopy = vNodesDisconnected;
            for (CNode* pnode : vNodesDisconnectedCopy) {
                // wait until threads are done using it
                if (pnode->GetRefCount() <= 0) {
                    bool fDelete = false;
                    {
                        TRY_LOCK(pnode->cs_inventory, lockInv);
                        if (lockInv) {
                            TRY_LOCK(pnode->cs_vSend, lockSend);
                            if (lockSend) {
                                fDelete = true;
                            }
                        }
                    }
                    if (fDelete) {
                        vNodesDisconnected.remove(pnode);
                        DeleteNode(pnode);
                    }
                }
            }
        }
        size_t vNodesSize;
        {
            LOCK(cs_vNodes);
            vNodesSize = vNodes.size();
        }
        if(vNodesSize != nPrevNodeCount) {
            nPrevNodeCount = vNodesSize;
            if(clientInterface)
                clientInterface->NotifyNumConnectionsChanged(nPrevNodeCount);
        }

        //
        // Find which sockets have data to receive
        //
        struct timeval timeout;
        timeout.tv_sec = 0;
        timeout.tv_usec = 50000; // frequency to poll pnode->vSend

        fd_set fdsetRecv;
        fd_set fdsetSend;
        fd_set fdsetError;
        FD_ZERO(&fdsetRecv);
        FD_ZERO(&fdsetSend);
        FD_ZERO(&fdsetError);
        SOCKET hSocketMax = 0;
        bool have_fds = false;

        for (const ListenSocket& hListenSocket : vhListenSocket) {
            FD_SET(hListenSocket.socket, &fdsetRecv);
            hSocketMax = std::max(hSocketMax, hListenSocket.socket);
            have_fds = true;
        }

        {
            LOCK(cs_vNodes);
            for (CNode* pnode : vNodes) {
                // Implement the following logic:
                // * If there is data to send, select() for sending data. As this only
                //   happens when optimistic write failed, we choose to first drain the
                //   write buffer in this case before receiving more. This avoids
                //   needlessly queueing received data, if the remote peer is not themselves
                //   receiving data. This means properly utilizing TCP flow control signalling.
                // * Otherwise, if there is space left in the receive buffer, select() for
                //   receiving data.
                // * Hand off all complete messages to the processor, to be handled without
                //   blocking here.

                bool select_recv = !pnode->fPauseRecv;
                bool select_send;
                {
                    LOCK(pnode->cs_vSend);
                    select_send = !pnode->vSendMsg.empty();
                }

                LOCK(pnode->cs_hSocket);
                if (pnode->hSocket == INVALID_SOCKET)
                    continue;

                FD_SET(pnode->hSocket, &fdsetError);
                hSocketMax = std::max(hSocketMax, pnode->hSocket);
                have_fds = true;

                if (select_send) {
                    FD_SET(pnode->hSocket, &fdsetSend);
                    continue;
                }
                if (select_recv) {
                    FD_SET(pnode->hSocket, &fdsetRecv);
                }
            }
        }

        int nSelect = select(have_fds ? hSocketMax + 1 : 0,
                             &fdsetRecv, &fdsetSend, &fdsetError, &timeout);
        if (interruptNet)
            return;

        if (nSelect == SOCKET_ERROR) {
            if (have_fds) {
                int nErr = WSAGetLastError();
                LogPrintf("socket select error %s\n", NetworkErrorString(nErr));
                for (unsigned int i = 0; i <= hSocketMax; i++)
                    FD_SET(i, &fdsetRecv);
            }
            FD_ZERO(&fdsetSend);
            FD_ZERO(&fdsetError);
            if (!interruptNet.sleep_for(std::chrono::milliseconds(timeout.tv_usec/1000)))
                return;
        }

        //
        // Accept new connections
        //
        for (const ListenSocket& hListenSocket : vhListenSocket) {
            if (hListenSocket.socket != INVALID_SOCKET && FD_ISSET(hListenSocket.socket, &fdsetRecv)) {
                AcceptConnection(hListenSocket);
            }
        }

        //
        // Service each socket
        //
        std::vector<CNode*> vNodesCopy;
        {
            LOCK(cs_vNodes);
            vNodesCopy = vNodes;
            for (CNode* pnode : vNodesCopy)
                pnode->AddRef();
        }
        for (CNode* pnode : vNodesCopy) {
            if (interruptNet)
                return;

            //
            // Receive
            //
            bool recvSet = false;
            bool sendSet = false;
            bool errorSet = false;
            {
                LOCK(pnode->cs_hSocket);
                if (pnode->hSocket == INVALID_SOCKET)
                    continue;
                recvSet = FD_ISSET(pnode->hSocket, &fdsetRecv);
                sendSet = FD_ISSET(pnode->hSocket, &fdsetSend);
                errorSet = FD_ISSET(pnode->hSocket, &fdsetError);
            }
            if (recvSet || errorSet) {
                {
                    {
                        // typical socket buffer is 8K-64K
                        char pchBuf[0x10000];
                        int nBytes = 0;
                        {
                            LOCK(pnode->cs_hSocket);
                            if (pnode->hSocket == INVALID_SOCKET)
                                continue;
                            nBytes = recv(pnode->hSocket, pchBuf, sizeof(pchBuf), MSG_DONTWAIT);
                        }
                        if (nBytes > 0) {
                            bool notify = false;
                            if (!pnode->ReceiveMsgBytes(pchBuf, nBytes, notify))
                                pnode->CloseSocketDisconnect();
                            RecordBytesRecv(nBytes);
                            if (notify) {
                                size_t nSizeAdded = 0;
                                auto it(pnode->vRecvMsg.begin());
                                for (; it != pnode->vRecvMsg.end(); ++it) {
                                    if (!it->complete())
                                        break;
                                    nSizeAdded += it->vRecv.size() + CMessageHeader::HEADER_SIZE;
                                }
                                {
                                    LOCK(pnode->cs_vProcessMsg);
                                    pnode->vProcessMsg.splice(pnode->vProcessMsg.end(), pnode->vRecvMsg, pnode->vRecvMsg.begin(), it);
                                    pnode->nProcessQueueSize += nSizeAdded;
                                    pnode->fPauseRecv = pnode->nProcessQueueSize > nReceiveFloodSize;
                                }
                                WakeMessageHandler();
                            }
                        } else if (nBytes == 0) {
                            // socket closed gracefully
                            if (!pnode->fDisconnect)
                                LogPrint(BCLog::NET, "socket closed\n");
                            pnode->CloseSocketDisconnect();
                        } else if (nBytes < 0) {
                            // error
                            int nErr = WSAGetLastError();
                            if (nErr != WSAEWOULDBLOCK && nErr != WSAEMSGSIZE && nErr != WSAEINTR && nErr != WSAEINPROGRESS) {
                                if (!pnode->fDisconnect)
                                    LogPrintf("socket recv error %s\n", NetworkErrorString(nErr));
                                pnode->CloseSocketDisconnect();
                            }
                        }
                    }
                }
            }

            //
            // Send
            //
            if (sendSet) {
                LOCK(pnode->cs_vSend);
                size_t nBytes = SocketSendData(pnode);
                if (nBytes)
                    RecordBytesSent(nBytes);
            }

            //
            // Inactivity checking
            //
            int64_t nTime = GetSystemTimeInSeconds();
            if (nTime - pnode->nTimeConnected > 60) {
                if (pnode->nLastRecv == 0 || pnode->nLastSend == 0) {
                    LogPrint(BCLog::NET, "socket no message in first 60 seconds, %d %d from %d\n", pnode->nLastRecv != 0, pnode->nLastSend != 0, pnode->id);
                    pnode->fDisconnect = true;
                } else if (nTime - pnode->nLastSend > TIMEOUT_INTERVAL) {
                    LogPrintf("socket sending timeout: %is\n", nTime - pnode->nLastSend);
                    pnode->fDisconnect = true;
                } else if (nTime - pnode->nLastRecv > (pnode->nVersion > BIP0031_VERSION ? TIMEOUT_INTERVAL : 90 * 60)) {
                    LogPrintf("socket receive timeout: %is\n", nTime - pnode->nLastRecv);
                    pnode->fDisconnect = true;
                } else if (pnode->nPingNonceSent && pnode->nPingUsecStart + TIMEOUT_INTERVAL * 1000000 < GetTimeMicros()) {
                    LogPrintf("ping timeout: %fs\n", 0.000001 * (GetTimeMicros() - pnode->nPingUsecStart));
                    pnode->fDisconnect = true;
                }
            }
        }
        {
            LOCK(cs_vNodes);
            for (CNode* pnode : vNodesCopy)
                pnode->Release();
        }
    }
}

void CConnman::WakeMessageHandler()
{
    {
        std::lock_guard<std::mutex> lock(mutexMsgProc);
        fMsgProcWake = true;
    }
    condMsgProc.notify_one();
}


static std::string GetDNSHost(const CDNSSeedData& data, ServiceFlags* requiredServiceBits)
{
    //use default host for non-filter-capable seeds or if we use the default service bits (NODE_NETWORK)
    if (!data.supportsServiceBitsFiltering || *requiredServiceBits == NODE_NETWORK) {
        *requiredServiceBits = NODE_NETWORK;
        return data.host;
    }

    return strprintf("x%x.%s", *requiredServiceBits, data.host);
}


void CConnman::ThreadDNSAddressSeed()
{
    // goal: only query DNS seeds if address need is acute
    if ((addrman.size() > 0) &&
        (!gArgs.GetBoolArg("-forcednsseed", DEFAULT_FORCEDNSSEED))) {
        if (!interruptNet.sleep_for(std::chrono::seconds(11)))
            return;

        LOCK(cs_vNodes);
        if (vNodes.size() >= 2) {
            LogPrintf("P2P peers available. Skipped DNS seeding.\n");
            return;
        }
    }

    const std::vector<CDNSSeedData>& vSeeds = Params().DNSSeeds();
    int found = 0;

    LogPrintf("Loading addresses from DNS seeds (could take a while)\n");

    for (const CDNSSeedData& seed : vSeeds) {
        if (interruptNet) {
            return;
        }
        if (HaveNameProxy()) {
            AddOneShot(seed.host);
        } else {
            std::vector<CNetAddr> vIPs;
            std::vector<CAddress> vAdd;
            ServiceFlags requiredServiceBits = nRelevantServices;
            std::string host = GetDNSHost(seed, &requiredServiceBits);
            CNetAddr resolveSource;
            if (!resolveSource.SetInternal(host)) {
                continue;
            }
            if (LookupHost(host.c_str(), vIPs, 0, true)) {
                for (CNetAddr& ip : vIPs) {
                    int nOneDay = 24*3600;
                    CAddress addr = CAddress(CService(ip, Params().GetDefaultPort()), requiredServiceBits);
                    addr.nTime = GetTime() - 3 * nOneDay - GetRand(4 * nOneDay); // use a random age between 3 and 7 days old
                    vAdd.push_back(addr);
                    found++;
                }
                addrman.Add(vAdd, resolveSource);
            }
        }
    }

    LogPrintf("%d addresses found from DNS seeds\n", found);
}












void CConnman::DumpAddresses()
{
    int64_t nStart = GetTimeMillis();

    CAddrDB adb;
    adb.Write(addrman);

    LogPrint(BCLog::NET, "Flushed %d addresses to peers.dat  %dms\n",
        addrman.size(), GetTimeMillis() - nStart);
}

void CConnman::DumpData()
{
    DumpAddresses();
    DumpBanlist();
}

void CConnman::ProcessOneShot()
{
    std::string strDest;
    {
        LOCK(cs_vOneShots);
        if (vOneShots.empty())
            return;
        strDest = vOneShots.front();
        vOneShots.pop_front();
    }
    CAddress addr;
    CSemaphoreGrant grant(*semOutbound, true);
    if (grant) {
        if (!OpenNetworkConnection(addr, false, &grant, strDest.c_str(), true))
            AddOneShot(strDest);
    }
}

void CConnman::ThreadOpenConnections()
{
    // Connect to specific addresses
    if (gArgs.IsArgSet("-connect")) {
        for (int64_t nLoop = 0;; nLoop++) {
            ProcessOneShot();
            for (const std::string& strAddr : gArgs.GetArgs("-connect")) {
                CAddress addr(CService(), NODE_NONE);
                OpenNetworkConnection(addr, false, nullptr, strAddr.c_str());
                for (int i = 0; i < 10 && i < nLoop; i++) {
                    if (!interruptNet.sleep_for(std::chrono::milliseconds(500)))
                        return;
                }
            }
            if (!interruptNet.sleep_for(std::chrono::milliseconds(500)))
                return;
        }
    }

    // Initiate network connections
    int64_t nStart = GetTime();

    // Minimum time before next feeler connection (in microseconds).
    int64_t nNextFeeler = PoissonNextSend(nStart * 1000 * 1000, FEELER_INTERVAL);
    while (!interruptNet) {
        ProcessOneShot();

        if (!interruptNet.sleep_for(std::chrono::milliseconds(500)))
            return;

        CSemaphoreGrant grant(*semOutbound);
        if (interruptNet)
            return;

        // Add seed nodes if DNS seeds are all down (an infrastructure attack?).
        if (addrman.size() == 0 && (GetTime() - nStart > 60)) {
            static bool done = false;
            if (!done) {
                LogPrintf("Adding fixed seed nodes as DNS doesn't seem to be available.\n");
                CNetAddr local;
                local.SetInternal("fixedseeds");
                addrman.Add(convertSeed6(Params().FixedSeeds()), local);
                done = true;
            }
        }

        //
        // Choose an address to connect to based on most recently seen
        //
        CAddress addrConnect;

        // Only connect out to one peer per network group (/16 for IPv4).
        // Do this here so we don't have to critsect vNodes inside mapAddresses critsect.
        int nOutbound = 0;
        std::set<std::vector<unsigned char> > setConnected;
        {
            LOCK(cs_vNodes);
            for (CNode* pnode : vNodes) {
                if (!pnode->fInbound) {
                    setConnected.insert(pnode->addr.GetGroup());
                    nOutbound++;
                }
            }
        }

        // Feeler Connections
        //
        // Design goals:
        //  * Increase the number of connectable addresses in the tried table.
        //
        // Method:
        //  * Choose a random address from new and attempt to connect to it if we can connect
        //    successfully it is added to tried.
        //  * Start attempting feeler connections only after node finishes making outbound
        //    connections.
        //  * Only make a feeler connection once every few minutes.
        //
        bool fFeeler = false;
        if (nOutbound >= nMaxOutbound) {
            int64_t nTime = GetTimeMicros(); // The current time right now (in microseconds).
            if (nTime > nNextFeeler) {
                nNextFeeler = PoissonNextSend(nTime, FEELER_INTERVAL);
                fFeeler = true;
            } else {
                continue;
            }
        }

        addrman.ResolveCollisions();

        int64_t nANow = GetAdjustedTime();
        int nTries = 0;
        while (!interruptNet) {
            CAddrInfo addr = addrman.SelectTriedCollision();

            // SelectTriedCollision returns an invalid address if it is empty.
            if (!fFeeler || !addr.IsValid()) {
                addr = addrman.Select(fFeeler);
            }

            // Require outbound connections, other than feelers, to be to distinct network groups
            if (!fFeeler && setConnected.count(addr.GetGroup())) {
                break;
            }

            // if we selected an invalid or local address, restart
            if (!addr.IsValid() || IsLocal(addr)) {
                break;
            }

            // If we didn't find an appropriate destination after trying 100 addresses fetched from addrman,
            // stop this loop, and let the outer loop run again (which sleeps, adds seed nodes, recalculates
            // already-connected network ranges, ...) before trying new addrman addresses.
            nTries++;
            if (nTries > 100)
                break;

            if (IsLimited(addr))
                continue;

            // only connect to full nodes
            if ((addr.nServices & REQUIRED_SERVICES) != REQUIRED_SERVICES)
                continue;

            // only consider very recently tried nodes after 30 failed attempts
            if (nANow - addr.nLastTry < 600 && nTries < 30)
                continue;

            // do not allow non-default ports, unless after 50 invalid addresses selected already
            if (addr.GetPort() != Params().GetDefaultPort() && nTries < 50)
                continue;

            addrConnect = addr;
            break;
        }

        if (addrConnect.IsValid()) {
            if (fFeeler) {
                // Add small amount of random noise before connection to avoid synchronization.
                int randsleep = GetRandInt(FEELER_SLEEP_WINDOW * 1000);
                if (!interruptNet.sleep_for(std::chrono::milliseconds(randsleep)))
                    return;
                LogPrint(BCLog::NET, "Making feeler connection to %s\n", addrConnect.ToString());
            }

            OpenNetworkConnection(addrConnect, (int)setConnected.size() >= std::min(nMaxConnections - 1, 2), &grant, nullptr, false, fFeeler);
        }
    }
}

std::vector<AddedNodeInfo> CConnman::GetAddedNodeInfo()
{
    std::vector<AddedNodeInfo> ret;

    std::list<std::string> lAddresses(0);
    {
        LOCK(cs_vAddedNodes);
        ret.reserve(vAddedNodes.size());
        std::copy(vAddedNodes.cbegin(), vAddedNodes.cend(), std::back_inserter(lAddresses));
    }


    // Build a map of all already connected addresses (by IP:port and by name) to inbound/outbound and resolved CService
    std::map<CService, bool> mapConnected;
    std::map<std::string, std::pair<bool, CService> > mapConnectedByName;
    {
        LOCK(cs_vNodes);
        for (const CNode* pnode : vNodes) {
            if (pnode->addr.IsValid()) {
                mapConnected[pnode->addr] = pnode->fInbound;
            }
            std::string addrName = pnode->GetAddrName();
            if (!addrName.empty()) {
                mapConnectedByName[std::move(addrName)] = std::make_pair(pnode->fInbound, static_cast<const CService&>(pnode->addr));
            }
        }
    }

    for (std::string& strAddNode : lAddresses) {
        CService service(LookupNumeric(strAddNode.c_str(), Params().GetDefaultPort()));
        if (service.IsValid()) {
            // strAddNode is an IP:port
            auto it = mapConnected.find(service);
            if (it != mapConnected.end()) {
                ret.emplace_back(strAddNode, service, true, it->second);
            } else {
                ret.emplace_back(strAddNode, CService(), false, false);
            }
        } else {
            // strAddNode is a name
            auto it = mapConnectedByName.find(strAddNode);
            if (it != mapConnectedByName.end()) {
                ret.emplace_back(strAddNode, it->second.second, true, it->second.first);
            } else {
                ret.emplace_back(strAddNode, CService(), false, false);
            }
        }
    }

    return ret;
}

void CConnman::ThreadOpenAddedConnections()
{
    {
        LOCK(cs_vAddedNodes);
        vAddedNodes = gArgs.GetArgs("-addnode");
    }

    for (unsigned int i = 0; true; i++) {
        std::vector<AddedNodeInfo> vInfo = GetAddedNodeInfo();
        for (const AddedNodeInfo& info : vInfo) {
            if (!info.fConnected) {
                CSemaphoreGrant grant(*semOutbound);
                // If strAddedNode is an IP/port, decode it immediately, so
                // OpenNetworkConnection can detect existing connections to that IP/port.
                CService service(LookupNumeric(info.strAddedNode.c_str(), Params().GetDefaultPort()));
                OpenNetworkConnection(CAddress(service, NODE_NONE), false, &grant, info.strAddedNode.c_str(), false);
                if (!interruptNet.sleep_for(std::chrono::milliseconds(500)))
                    return;
            }
        }
        if (!interruptNet.sleep_for(std::chrono::minutes(2)))
            return;
    }
}

// if successful, this moves the passed grant to the constructed node
bool CConnman::OpenNetworkConnection(const CAddress& addrConnect, bool fCountFailure, CSemaphoreGrant* grantOutbound, const char* pszDest, bool fOneShot, bool fFeeler)
{
    //
    // Initiate outbound network connection
    //
    if (interruptNet) {
        return false;
    }
    if (!pszDest) {
        if (IsLocal(addrConnect) ||
            FindNode(static_cast<CNetAddr>(addrConnect)) || IsBanned(addrConnect) ||
            FindNode(addrConnect.ToStringIPPort()))
            return false;
    } else if (FindNode(pszDest))
        return false;

    CNode* pnode = ConnectNode(addrConnect, pszDest, fCountFailure);

    if (!pnode)
        return false;
    if (grantOutbound)
        grantOutbound->MoveTo(pnode->grantOutbound);
    pnode->fNetworkNode = true;
    if (fOneShot)
        pnode->fOneShot = true;
    if (fFeeler)
        pnode->fFeeler = true;

    m_msgproc->InitializeNode(pnode);
    {
        LOCK(cs_vNodes);
        vNodes.push_back(pnode);
    }

    return true;
}

void CConnman::ThreadMessageHandler()
{
    while (!flagInterruptMsgProc) {
        std::vector<CNode*> vNodesCopy;
        {
            LOCK(cs_vNodes);
            vNodesCopy = vNodes;
            for (CNode* pnode : vNodesCopy) {
                pnode->AddRef();
            }
        }

        bool fMoreWork = false;

        for (CNode* pnode : vNodesCopy) {
            if (pnode->fDisconnect)
                continue;

            // Receive messages
            bool fMoreNodeWork = m_msgproc->ProcessMessages(pnode, flagInterruptMsgProc);
            fMoreWork |= (fMoreNodeWork && !pnode->fPauseSend);
            if (flagInterruptMsgProc)
                return;

            // Send messages
            {
                LOCK(pnode->cs_sendProcessing);
                m_msgproc->SendMessages(pnode, flagInterruptMsgProc);
            }

            if (flagInterruptMsgProc)
                return;
        }


        {
            LOCK(cs_vNodes);
            for (CNode* pnode : vNodesCopy)
                pnode->Release();
        }

        std::unique_lock<std::mutex> lock(mutexMsgProc);
        if (!fMoreWork) {
            condMsgProc.wait_until(lock, std::chrono::steady_clock::now() + std::chrono::milliseconds(100), [this] { return fMsgProcWake; });
        }
        fMsgProcWake = false;
    }
}

bool CConnman::BindListenPort(const CService& addrBind, std::string& strError, bool fWhitelisted)
{
    strError = "";
    int nOne = 1;

    // Create socket for listening for incoming connections
    struct sockaddr_storage sockaddr;
    socklen_t len = sizeof(sockaddr);
    if (!addrBind.GetSockAddr((struct sockaddr*)&sockaddr, &len)) {
        strError = strprintf("Error: Bind address family for %s not supported", addrBind.ToString());
        LogPrintf("%s\n", strError);
        return false;
    }

    SOCKET hListenSocket = socket(((struct sockaddr*)&sockaddr)->sa_family, SOCK_STREAM, IPPROTO_TCP);
    if (hListenSocket == INVALID_SOCKET) {
        strError = strprintf("Error: Couldn't open socket for incoming connections (socket returned error %s)", NetworkErrorString(WSAGetLastError()));
        LogPrintf("%s\n", strError);
        return false;
    }
    if (!IsSelectableSocket(hListenSocket)) {
        strError = "Error: Couldn't create a listenable socket for incoming connections";
        LogPrintf("%s\n", strError);
        return false;
    }


#ifndef WIN32
#ifdef SO_NOSIGPIPE
    // Different way of disabling SIGPIPE on BSD
    setsockopt(hListenSocket, SOL_SOCKET, SO_NOSIGPIPE, (void*)&nOne, sizeof(int));
#endif
    // Allow binding if the port is still in TIME_WAIT state after
    // the program was closed and restarted. Not an issue on windows!
    setsockopt(hListenSocket, SOL_SOCKET, SO_REUSEADDR, (void*)&nOne, sizeof(int));
#endif

    // Set to non-blocking, incoming connections will also inherit this
    if (!SetSocketNonBlocking(hListenSocket, true)) {
        strError = strprintf("BindListenPort: Setting listening socket to non-blocking failed, error %s\n", NetworkErrorString(WSAGetLastError()));
        LogPrintf("%s\n", strError);
        return false;
    }

    // some systems don't have IPV6_V6ONLY but are always v6only; others do have the option
    // and enable it by default or not. Try to enable it, if possible.
    if (addrBind.IsIPv6()) {
#ifdef IPV6_V6ONLY
#ifdef WIN32
        setsockopt(hListenSocket, IPPROTO_IPV6, IPV6_V6ONLY, (const char*)&nOne, sizeof(int));
#else
        setsockopt(hListenSocket, IPPROTO_IPV6, IPV6_V6ONLY, (void*)&nOne, sizeof(int));
#endif
#endif
#ifdef WIN32
        int nProtLevel = PROTECTION_LEVEL_UNRESTRICTED;
        setsockopt(hListenSocket, IPPROTO_IPV6, IPV6_PROTECTION_LEVEL, (const char*)&nProtLevel, sizeof(int));
#endif
    }

    if (::bind(hListenSocket, (struct sockaddr*)&sockaddr, len) == SOCKET_ERROR) {
        int nErr = WSAGetLastError();
        if (nErr == WSAEADDRINUSE)
            strError = strprintf(_("Unable to bind to %s on this computer. PIVX Core is probably already running."), addrBind.ToString());
        else
            strError = strprintf(_("Unable to bind to %s on this computer (bind returned error %s)"), addrBind.ToString(), NetworkErrorString(nErr));
        LogPrintf("%s\n", strError);
        CloseSocket(hListenSocket);
        return false;
    }
    LogPrintf("Bound to %s\n", addrBind.ToString());

    // Listen for incoming connections
    if (listen(hListenSocket, SOMAXCONN) == SOCKET_ERROR) {
        strError = strprintf(_("Error: Listening for incoming connections failed (listen returned error %s)"), NetworkErrorString(WSAGetLastError()));
        LogPrintf("%s\n", strError);
        CloseSocket(hListenSocket);
        return false;
    }

    vhListenSocket.emplace_back(hListenSocket, fWhitelisted);

    if (addrBind.IsRoutable() && fDiscover && !fWhitelisted)
        AddLocal(addrBind, LOCAL_BIND);

    return true;
}

void Discover()
{
    if (!fDiscover)
        return;

#ifdef WIN32
    // Get local host IP
    char pszHostName[256] = "";
    if (gethostname(pszHostName, sizeof(pszHostName)) != SOCKET_ERROR) {
        std::vector<CNetAddr> vaddr;
        if (LookupHost(pszHostName, vaddr, 0, true)) {
            for (const CNetAddr& addr : vaddr) {
                if (AddLocal(addr, LOCAL_IF))
                    LogPrintf("%s: %s - %s\n", __func__, pszHostName, addr.ToString());
            }
        }
    }
#elif (HAVE_DECL_GETIFADDRS && HAVE_DECL_FREEIFADDRS)
    // Get local host ip
    struct ifaddrs* myaddrs;
    if (getifaddrs(&myaddrs) == 0) {
        for (struct ifaddrs* ifa = myaddrs; ifa != NULL; ifa = ifa->ifa_next) {
            if (ifa->ifa_addr == NULL) continue;
            if ((ifa->ifa_flags & IFF_UP) == 0) continue;
            if (strcmp(ifa->ifa_name, "lo") == 0) continue;
            if (strcmp(ifa->ifa_name, "lo0") == 0) continue;
            if (ifa->ifa_addr->sa_family == AF_INET) {
                struct sockaddr_in* s4 = (struct sockaddr_in*)(ifa->ifa_addr);
                CNetAddr addr(s4->sin_addr);
                if (AddLocal(addr, LOCAL_IF))
                    LogPrintf("%s: IPv4 %s: %s\n", __func__, ifa->ifa_name, addr.ToString());
            } else if (ifa->ifa_addr->sa_family == AF_INET6) {
                struct sockaddr_in6* s6 = (struct sockaddr_in6*)(ifa->ifa_addr);
                CNetAddr addr(s6->sin6_addr);
                if (AddLocal(addr, LOCAL_IF))
                    LogPrintf("%s: IPv6 %s: %s\n", __func__, ifa->ifa_name, addr.ToString());
            }
        }
        freeifaddrs(myaddrs);
    }
#endif
}

CConnman::CConnman(uint64_t nSeed0In, uint64_t nSeed1In) : nSeed0(nSeed0In), nSeed1(nSeed1In)
{
    setBannedIsDirty = false;
    fAddressesInitialized = false;
    nLastNodeId = 0;
    nSendBufferMaxSize = 0;
    nReceiveFloodSize = 0;
    nMaxConnections = 0;
    nMaxOutbound = 0;
    nBestHeight = 0;
    clientInterface = nullptr;
    flagInterruptMsgProc = false;
}

NodeId CConnman::GetNewNodeId()
{
    return nLastNodeId.fetch_add(1, std::memory_order_relaxed);
}

bool CConnman::Start(CScheduler& scheduler, std::string& strNodeError, Options connOptions)
{
    nTotalBytesRecv = 0;
    nTotalBytesSent = 0;

    nRelevantServices = connOptions.nRelevantServices;
    nLocalServices = connOptions.nLocalServices;
    nMaxConnections = connOptions.nMaxConnections;
    nMaxOutbound = std::min(connOptions.nMaxOutbound, nMaxConnections);
    nMaxFeeler = connOptions.nMaxFeeler;

    nSendBufferMaxSize = connOptions.nSendBufferMaxSize;
    nReceiveFloodSize = connOptions.nReceiveFloodSize;

    SetBestHeight(connOptions.nBestHeight);

    clientInterface = connOptions.uiInterface;
    if (clientInterface)
        clientInterface->InitMessage(_("Loading addresses..."));
    m_msgproc = connOptions.m_msgproc;
    // Load addresses from peers.dat
    int64_t nStart = GetTimeMillis();
    {
        CAddrDB adb;
        if (adb.Read(addrman))
            LogPrintf("Loaded %i addresses from peers.dat  %dms\n", addrman.size(), GetTimeMillis() - nStart);
        else {
            addrman.Clear(); // Addrman can be in an inconsistent state after failure, reset it
            LogPrintf("Invalid or missing peers.dat; recreating\n");
            DumpAddresses();
        }
    }
    if (clientInterface)
        clientInterface->InitMessage(_("Loading banlist..."));
    // Load addresses from banlist.dat
    nStart = GetTimeMillis();
    CBanDB bandb;
    banmap_t banmap;
    if (bandb.Read(banmap)) {
        SetBanned(banmap); // thread save setter
        SetBannedSetDirty(false); // no need to write down, just read data
        SweepBanned(); // sweep out unused entries

        LogPrint(BCLog::NET, "Loaded %d banned node ips/subnets from banlist.dat  %dms\n",
            banmap.size(), GetTimeMillis() - nStart);
    } else {
        LogPrintf("Invalid or missing banlist.dat; recreating\n");
        SetBannedSetDirty(true); // force write
        DumpBanlist();
    }

    // Initialize random numbers. Even when rand() is only usable for trivial use-cases most nodes should have a different
    // seed after all the file-IO done at this point. Should be good enough even when nodes are started via scripts.
    srand(time(NULL));

    fAddressesInitialized = true;

    if (semOutbound == nullptr) {
        // initialize semaphore
        semOutbound = std::make_unique<CSemaphore>(std::min((nMaxOutbound + nMaxFeeler), nMaxConnections));
    }

    if (pnodeLocalHost == nullptr) {
        CNetAddr local;
        LookupHost("127.0.0.1", local, false);

        NodeId id = GetNewNodeId();
        uint64_t nonce = GetDeterministicRandomizer(RANDOMIZER_ID_LOCALHOSTNONCE).Write(id).Finalize();

        pnodeLocalHost = new CNode(id, nLocalServices, GetBestHeight(), INVALID_SOCKET, CAddress(CService(local, 0), nLocalServices), 0, nonce);
        m_msgproc->InitializeNode(pnodeLocalHost);
    }

    //
    // Start threads
    //
    assert(m_msgproc);
    InterruptSocks5(false);
    interruptNet.reset();
    flagInterruptMsgProc = false;

    {
        std::unique_lock<std::mutex> lock(mutexMsgProc);
        fMsgProcWake = false;
    }

    // Send and receive from sockets, accept connections
    threadSocketHandler = std::thread(&TraceThread<std::function<void()> >, "net", std::function<void()>(std::bind(&CConnman::ThreadSocketHandler, this)));

    if (!gArgs.GetBoolArg("-dnsseed", true))
        LogPrintf("DNS seeding disabled\n");
    else
        threadDNSAddressSeed = std::thread(&TraceThread<std::function<void()> >, "dnsseed", std::function<void()>(std::bind(&CConnman::ThreadDNSAddressSeed, this)));

    // Initiate outbound connections from -addnode
    threadOpenAddedConnections = std::thread(&TraceThread<std::function<void()> >, "addcon", std::function<void()>(std::bind(&CConnman::ThreadOpenAddedConnections, this)));

    // Initiate outbound connections unless connect=0
    if (!gArgs.IsArgSet("-connect") || gArgs.GetArgs("-connect").size() != 1 || gArgs.GetArgs("-connect")[0] != "0")
        threadOpenConnections = std::thread(&TraceThread<std::function<void()> >, "opencon", std::function<void()>(std::bind(&CConnman::ThreadOpenConnections, this)));

    // Process messages
    threadMessageHandler = std::thread(&TraceThread<std::function<void()> >, "msghand", std::function<void()>(std::bind(&CConnman::ThreadMessageHandler, this)));

    // Dump network addresses
    scheduler.scheduleEvery(std::bind(&CConnman::DumpData, this), DUMP_ADDRESSES_INTERVAL * 1000);

    return true;
}

class CNetCleanup
{
public:
    CNetCleanup() {}

    ~CNetCleanup()
    {
#ifdef WIN32
        // Shutdown Windows Sockets
        WSACleanup();
#endif
    }
}
instance_of_cnetcleanup;

void CExplicitNetCleanup::callCleanup()
{
    // Explicit call to destructor of CNetCleanup because it's not implicitly called
    // when the wallet is restarted from within the wallet itself.
    CNetCleanup* tmp = new CNetCleanup();
    delete tmp; // Stroustrup's gonna kill me for that
}

void CConnman::Interrupt()
{
    {
        std::lock_guard<std::mutex> lock(mutexMsgProc);
        flagInterruptMsgProc = true;
    }
    condMsgProc.notify_all();

    interruptNet();
    InterruptSocks5(true);

    if (semOutbound)
        for (int i=0; i<(nMaxOutbound + nMaxFeeler); i++)
            semOutbound->post();
}

void CConnman::Stop()
{
    if (threadMessageHandler.joinable())
        threadMessageHandler.join();
    if (threadOpenConnections.joinable())
        threadOpenConnections.join();
    if (threadOpenAddedConnections.joinable())
        threadOpenAddedConnections.join();
    if (threadDNSAddressSeed.joinable())
        threadDNSAddressSeed.join();
    if (threadSocketHandler.joinable())
        threadSocketHandler.join();

    if (fAddressesInitialized)
    {
        DumpData();
        fAddressesInitialized = false;
    }

    // Close sockets
    for(CNode* pnode : vNodes)
        pnode->CloseSocketDisconnect();
    for(ListenSocket& hListenSocket : vhListenSocket)
        if (hListenSocket.socket != INVALID_SOCKET)
            if (!CloseSocket(hListenSocket.socket))
                LogPrintf("CloseSocket(hListenSocket) failed with error %s\n", NetworkErrorString(WSAGetLastError()));

    // clean up some globals (to help leak detection)
    for(CNode* pnode : vNodes) {
        DeleteNode(pnode);
    }
    for(CNode* pnode : vNodesDisconnected) {
        DeleteNode(pnode);
    }
    vNodes.clear();
    vNodesDisconnected.clear();
    vhListenSocket.clear();
    semOutbound.reset();
    if(pnodeLocalHost)
        DeleteNode(pnodeLocalHost);
    pnodeLocalHost = NULL;
}

void CConnman::DeleteNode(CNode* pnode)
{
    assert(pnode);
    bool fUpdateConnectionTime = false;
    m_msgproc->FinalizeNode(pnode->GetId(), fUpdateConnectionTime);
    if (fUpdateConnectionTime) {
        addrman.Connected(pnode->addr);
    }
    delete pnode;
}

CConnman::~CConnman()
{
    Interrupt();
    Stop();
}

size_t CConnman::GetAddressCount() const
{
    return addrman.size();
}

void CConnman::SetServices(const CService &addr, ServiceFlags nServices)
{
    addrman.SetServices(addr, nServices);
}

void CConnman::MarkAddressGood(const CAddress& addr)
{
    addrman.Good(addr);
}

void CConnman::AddNewAddress(const CAddress& addr, const CAddress& addrFrom, int64_t nTimePenalty)
{
    addrman.Add(addr, addrFrom, nTimePenalty);
}

void CConnman::AddNewAddresses(const std::vector<CAddress>& vAddr, const CAddress& addrFrom, int64_t nTimePenalty)
{
    addrman.Add(vAddr, addrFrom, nTimePenalty);
}

std::vector<CAddress> CConnman::GetAddresses()
{
    return addrman.GetAddr();
}

bool CConnman::AddNode(const std::string& strNode)
{
    LOCK(cs_vAddedNodes);
    for (const std::string& it : vAddedNodes) {
        if (strNode == it) return false;
    }

    vAddedNodes.push_back(strNode);
    return true;
}

bool CConnman::RemoveAddedNode(const std::string& strNode)
{
    LOCK(cs_vAddedNodes);
    for(std::vector<std::string>::iterator it = vAddedNodes.begin(); it != vAddedNodes.end(); ++it) {
        if (strNode == *it) {
            vAddedNodes.erase(it);
            return true;
        }
    }
    return false;
}

size_t CConnman::GetNodeCount(NumConnections flags)
{
    LOCK(cs_vNodes);
    if (flags == CConnman::CONNECTIONS_ALL) // Shortcut if we want total
        return vNodes.size();

    int nNum = 0;
    for (const auto& pnode : vNodes) {
        if (flags & (pnode->fInbound ? CONNECTIONS_IN : CONNECTIONS_OUT)) {
            nNum++;
        }
    }

    return nNum;
}

void CConnman::GetNodeStats(std::vector<CNodeStats>& vstats)
{
    vstats.clear();
    LOCK(cs_vNodes);
    vstats.reserve(vNodes.size());
    for (CNode* pnode : vNodes) {
        vstats.emplace_back();
        pnode->copyStats(vstats.back());
    }
}

bool CConnman::DisconnectNode(const std::string& strNode)
{
    LOCK(cs_vNodes);
    if (CNode* pnode = FindNode(strNode)) {
        pnode->fDisconnect = true;
        return true;
    }
    return false;
}

bool CConnman::DisconnectNode(NodeId id)
{
    LOCK(cs_vNodes);
    for(CNode* pnode : vNodes) {
        if (id == pnode->id) {
            pnode->fDisconnect = true;
            return true;
        }
    }
    return false;
}

void CConnman::RelayInv(CInv& inv)
{
    LOCK(cs_vNodes);
    for (CNode* pnode : vNodes){
        if((pnode->nServices == NODE_BLOOM_WITHOUT_MN) && inv.IsMasterNodeType())continue;
        if (pnode->nVersion >= ActiveProtocol())
            pnode->PushInventory(inv);
    }
}

void CConnman::RecordBytesRecv(uint64_t bytes)
{
    LOCK(cs_totalBytesRecv);
    nTotalBytesRecv += bytes;
}

void CConnman::RecordBytesSent(uint64_t bytes)
{
    LOCK(cs_totalBytesSent);
    nTotalBytesSent += bytes;
}

uint64_t CConnman::GetTotalBytesRecv()
{
    LOCK(cs_totalBytesRecv);
    return nTotalBytesRecv;
}

uint64_t CConnman::GetTotalBytesSent()
{
    LOCK(cs_totalBytesSent);
    return nTotalBytesSent;
}

ServiceFlags CConnman::GetLocalServices() const
{
    return nLocalServices;
}

void CConnman::SetBestHeight(int height)
{
    nBestHeight.store(height, std::memory_order_release);
}

int CConnman::GetBestHeight() const
{
    return nBestHeight.load(std::memory_order_acquire);
}

unsigned int CConnman::GetReceiveFloodSize() const { return nReceiveFloodSize; }
unsigned int CConnman::GetSendBufferSize() const{ return nSendBufferMaxSize; }

CNode::CNode(NodeId idIn, ServiceFlags nLocalServicesIn, int nMyStartingHeightIn, SOCKET hSocketIn, const CAddress& addrIn, uint64_t nKeyedNetGroupIn, uint64_t nLocalHostNonceIn, const std::string& addrNameIn, bool fInboundIn) :
    nTimeConnected(GetSystemTimeInSeconds()),
    addr(addrIn),
    fInbound(fInboundIn),
    id(idIn),
    nKeyedNetGroup(nKeyedNetGroupIn),
    addrKnown(5000, 0.001),
    filterInventoryKnown(50000, 0.000001),
    nLocalHostNonce(nLocalHostNonceIn),
    nLocalServices(nLocalServicesIn),
    nMyStartingHeight(nMyStartingHeightIn),
    nSendVersion(0)
{
    nServices = NODE_NONE;
    nServicesExpected = NODE_NONE;
    hSocket = hSocketIn;
    nRecvVersion = INIT_PROTO_VERSION;
    nLastSend = 0;
    nLastRecv = 0;
    nSendBytes = 0;
    nRecvBytes = 0;
    nTimeOffset = 0;
    addrName = addrNameIn == "" ? addr.ToStringIPPort() : addrNameIn;
    nVersion = 0;
    strSubVer = "";
    fWhitelisted = false;
    fOneShot = false;
    fClient = false; // set by version message
    fFeeler = false;
    fNetworkNode = false;
    fSuccessfullyConnected = false;
    fDisconnect = false;
    nRefCount = 0;
    nSendSize = 0;
    nSendOffset = 0;
    hashContinue = UINT256_ZERO;
    nStartingHeight = -1;
    filterInventoryKnown.reset();
    fSendMempool = false;
    fGetAddr = false;
    nNextLocalAddrSend = 0;
    nNextAddrSend = 0;
    fRelayTxes = false;
    pfilter = std::make_unique<CBloomFilter>();
    timeLastMempoolReq = 0;
    nPingNonceSent = 0;
    nPingUsecStart = 0;
    nPingUsecTime = 0;
    fPingQueued = false;
    nMinPingUsecTime = std::numeric_limits<int64_t>::max();
    fPauseRecv = false;
    fPauseSend = false;
    nProcessQueueSize = 0;

    for (const std::string &msg : getAllNetMessageTypes())
        mapRecvBytesPerMsgCmd[msg] = 0;
    mapRecvBytesPerMsgCmd[NET_MESSAGE_COMMAND_OTHER] = 0;

    if (fLogIPs)
        LogPrint(BCLog::NET, "Added connection to %s peer=%d\n", addrName, id);
    else
        LogPrint(BCLog::NET, "Added connection peer=%d\n", id);
}

CNode::~CNode()
{
    CloseSocket(hSocket);
}

void CNode::AskFor(const CInv& inv)
{
    if (mapAskFor.size() > MAPASKFOR_MAX_SZ || setAskFor.size() > SETASKFOR_MAX_SZ)
        return;
    // a peer may not have multiple non-responded queue positions for a single inv item
    if (!setAskFor.insert(inv.hash).second)
        return;

    // We're using mapAskFor as a priority queue,
    // the key is the earliest time the request can be sent
    int64_t nRequestTime;
    limitedmap<CInv, int64_t>::const_iterator it = mapAlreadyAskedFor.find(inv);
    if (it != mapAlreadyAskedFor.end())
        nRequestTime = it->second;
    else
        nRequestTime = 0;
    LogPrint(BCLog::NET, "askfor %s  %d (%s) peer=%d\n", inv.ToString(), nRequestTime, FormatISO8601Time(nRequestTime / 1000000), id);

    // Make sure not to reuse time indexes to keep things in the same order
    int64_t nNow = GetTimeMicros() - 1000000;
    static int64_t nLastTime;
    ++nLastTime;
    nNow = std::max(nNow, nLastTime);
    nLastTime = nNow;

    // Each retry is 2 minutes after the last
    nRequestTime = std::max(nRequestTime + 2 * 60 * 1000000, nNow);
    if (it != mapAlreadyAskedFor.end())
        mapAlreadyAskedFor.update(it, nRequestTime);
    else
        mapAlreadyAskedFor.insert(std::make_pair(inv, nRequestTime));
    mapAskFor.insert(std::make_pair(nRequestTime, inv));
}

bool CConnman::NodeFullyConnected(const CNode* pnode)
{
    return pnode && pnode->fSuccessfullyConnected && !pnode->fDisconnect;
}

void CConnman::PushMessage(CNode* pnode, CSerializedNetMsg&& msg)
{
    size_t nMessageSize = msg.data.size();
    size_t nTotalSize = nMessageSize + CMessageHeader::HEADER_SIZE;
    LogPrint(BCLog::NET, "sending %s (%d bytes) peer=%d\n",  SanitizeString(msg.command.c_str()), nMessageSize, pnode->id);

    std::vector<unsigned char> serializedHeader;
    serializedHeader.reserve(CMessageHeader::HEADER_SIZE);
    uint256 hash = Hash(msg.data.data(), msg.data.data() + nMessageSize);
    CMessageHeader hdr(Params().MessageStart(), msg.command.c_str(), nMessageSize);
    memcpy(hdr.pchChecksum, hash.begin(), CMessageHeader::CHECKSUM_SIZE);

    CVectorWriter{SER_NETWORK, INIT_PROTO_VERSION, serializedHeader, 0, hdr};

    size_t nBytesSent = 0;
    {
        LOCK(pnode->cs_vSend);
        bool optimisticSend(pnode->vSendMsg.empty());

        //log total amount of bytes per command
        pnode->mapSendBytesPerMsgCmd[msg.command] += nTotalSize;
        pnode->nSendSize += nTotalSize;

        if (pnode->nSendSize > nSendBufferMaxSize)
            pnode->fPauseSend = true;
        pnode->vSendMsg.push_back(std::move(serializedHeader));
        if (nMessageSize)
            pnode->vSendMsg.push_back(std::move(msg.data));

        // If write queue empty, attempt "optimistic write"
        if (optimisticSend == true)
            nBytesSent = SocketSendData(pnode);
    }
    if (nBytesSent)
        RecordBytesSent(nBytesSent);
}

bool CConnman::ForNode(NodeId id, std::function<bool(CNode* pnode)> func)
{
    CNode* found = nullptr;
    LOCK(cs_vNodes);
    for (auto&& pnode : vNodes) {
        if(pnode->id == id) {
            found = pnode;
            break;
        }
    }
    return found != nullptr && NodeFullyConnected(found) && func(found);
}

bool CConnman::IsNodeConnected(const CAddress& addr)
{
    return FindNode(addr.ToStringIPPort());
}

CNode* CConnman::ConnectNode(CAddress addrConnect)
{
    return ConnectNode(addrConnect, nullptr, true);
}

// valid, reachable and routable address (except for RegTest)
bool validateMasternodeIP(const std::string& addrStr)
{
    CNetAddr resolved;
    if (LookupHost(addrStr.c_str(), resolved, false)) {
        return ((IsReachable(resolved) && resolved.IsRoutable()) ||
                (Params().IsRegTestNet() && resolved.IsValid()));
    }
    return false;
}

int64_t PoissonNextSend(int64_t nNow, int average_interval_seconds) {
    return nNow + (int64_t)(log1p(GetRand(1ULL << 48) * -0.0000000000000035527136788 /* -1/2^48 */) * average_interval_seconds * -1000000.0 + 0.5);
}

CSipHasher CConnman::GetDeterministicRandomizer(uint64_t id)
{
    return CSipHasher(nSeed0, nSeed1).Write(id);
}

uint64_t CConnman::CalculateKeyedNetGroup(const CAddress& ad)
{
    std::vector<unsigned char> vchNetGroup(ad.GetGroup());

    return GetDeterministicRandomizer(RANDOMIZER_ID_NETGROUP).Write(vchNetGroup.data(), vchNetGroup.size()).Finalize();
}