net.cpp

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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2019 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
#if defined(HAVE_CONFIG_H)
#include <config/bitcoin-config.h>
#endif
 
#include <net.h>
 
#include <addrdb.h>
#include <addrman.h>
#include <avalanche/avalanche.h>
#include <banman.h>
#include <clientversion.h>
#include <common/args.h>
#include <compat/compat.h>
#include <config.h>
#include <consensus/consensus.h>
#include <crypto/sha256.h>
#include <dnsseeds.h>
#include <i2p.h>
#include <logging.h>
#include <netaddress.h>
#include <netbase.h>
#include <node/eviction.h>
#include <node/ui_interface.h>
#include <protocol.h>
#include <random.h>
#include <scheduler.h>
#include <util/fs.h>
#include <util/sock.h>
#include <util/strencodings.h>
#include <util/thread.h>
#include <util/threadinterrupt.h>
#include <util/trace.h>
#include <util/translation.h>
 
#ifdef WIN32
#include <cstring>
#else
#include <fcntl.h>
#endif
 
#ifdef USE_POLL
#include <poll.h>
#endif
 
#include <algorithm>
#include <array>
#include <cmath>
#include <cstdint>
#include <functional>
#include <limits>
#include <optional>
#include <unordered_map>
 
static constexpr size_t MAX_BLOCK_RELAY_ONLY_ANCHORS = 2;
static_assert(MAX_BLOCK_RELAY_ONLY_ANCHORS <=
                  static_cast<size_t>(MAX_BLOCK_RELAY_ONLY_CONNECTIONS),
              "MAX_BLOCK_RELAY_ONLY_ANCHORS must not exceed "
              "MAX_BLOCK_RELAY_ONLY_CONNECTIONS.");
const char *const ANCHORS_DATABASE_FILENAME = "anchors.dat";
 
// How often to dump addresses to peers.dat
static constexpr std::chrono::minutes DUMP_PEERS_INTERVAL{15};
 
static constexpr int DNSSEEDS_TO_QUERY_AT_ONCE = 3;
 
static constexpr std::chrono::seconds DNSSEEDS_DELAY_FEW_PEERS{11};
static constexpr std::chrono::minutes DNSSEEDS_DELAY_MANY_PEERS{5};
// "many" vs "few" peers
static constexpr int DNSSEEDS_DELAY_PEER_THRESHOLD = 1000;
 
static constexpr std::chrono::seconds MAX_UPLOAD_TIMEFRAME{60 * 60 * 24};
 
// A random time period (0 to 1 seconds) is added to feeler connections to
// prevent synchronization.
static constexpr auto FEELER_SLEEP_WINDOW{1s};
 
enum BindFlags {
    BF_NONE = 0,
    BF_EXPLICIT = (1U << 0),
    BF_REPORT_ERROR = (1U << 1),
    BF_DONT_ADVERTISE = (1U << 2),
};
 
// The set of sockets cannot be modified while waiting
// The sleep time needs to be small to avoid new sockets stalling
static const uint64_t SELECT_TIMEOUT_MILLISECONDS = 50;
 
const std::string NET_MESSAGE_TYPE_OTHER = "*other*";
 
// SHA256("netgroup")[0:8]
static const uint64_t RANDOMIZER_ID_NETGROUP = 0x6c0edd8036ef4036ULL;
// SHA256("localhostnonce")[0:8]
static const uint64_t RANDOMIZER_ID_LOCALHOSTNONCE = 0xd93e69e2bbfa5735ULL;
// SHA256("localhostnonce")[8:16]
static const uint64_t RANDOMIZER_ID_EXTRAENTROPY = 0x94b05d41679a4ff7ULL;
// SHA256("addrcache")[0:8]
static const uint64_t RANDOMIZER_ID_ADDRCACHE = 0x1cf2e4ddd306dda9ULL;
//
// Global state variables
//
bool fDiscover = true;
bool fListen = true;
GlobalMutex g_maplocalhost_mutex;
std::map<CNetAddr, LocalServiceInfo>
    mapLocalHost GUARDED_BY(g_maplocalhost_mutex);
static bool vfLimited[NET_MAX] GUARDED_BY(g_maplocalhost_mutex) = {};
 
void CConnman::AddAddrFetch(const std::string &strDest) {
    LOCK(m_addr_fetches_mutex);
    m_addr_fetches.push_back(strDest);
}
 
uint16_t GetListenPort() {
    // If -bind= is provided with ":port" part, use that (first one if multiple
    // are provided).
    for (const std::string &bind_arg : gArgs.GetArgs("-bind")) {
        constexpr uint16_t dummy_port = 0;
 
        const std::optional<CService> bind_addr{
            Lookup(bind_arg, dummy_port, /*fAllowLookup=*/false)};
        if (bind_addr.has_value() && bind_addr->GetPort() != dummy_port) {
            return bind_addr->GetPort();
        }
    }
 
    // Otherwise, if -whitebind= without NetPermissionFlags::NoBan is provided,
    // use that
    // (-whitebind= is required to have ":port").
    for (const std::string &whitebind_arg : gArgs.GetArgs("-whitebind")) {
        NetWhitebindPermissions whitebind;
        bilingual_str error;
        if (NetWhitebindPermissions::TryParse(whitebind_arg, whitebind,
                                              error)) {
            if (!NetPermissions::HasFlag(whitebind.m_flags,
                                         NetPermissionFlags::NoBan)) {
                return whitebind.m_service.GetPort();
            }
        }
    }
 
    // Otherwise, if -port= is provided, use that. Otherwise use the default
    // port.
    return static_cast<uint16_t>(
        gArgs.GetIntArg("-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(g_maplocalhost_mutex);
        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;
}
 
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 auto one_week{7 * 24h};
    std::vector<CAddress> vSeedsOut;
    vSeedsOut.reserve(vSeedsIn.size());
    FastRandomContext rng;
    // TODO: apply core#25284 when backporting core#21560
    for (const auto &seed_in : vSeedsIn) {
        struct in6_addr ip;
        memcpy(&ip, seed_in.addr, sizeof(ip));
        CAddress addr(CService(ip, seed_in.port),
                      GetDesirableServiceFlags(NODE_NONE));
        addr.nTime =
            rng.rand_uniform_delay(Now<NodeSeconds>() - one_week, -one_week);
        vSeedsOut.push_back(addr);
    }
    return vSeedsOut;
}
 
// Get best local address for a particular peer as a CService. 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.
CService GetLocalAddress(const CNetAddr &addrPeer) {
    CService ret{CNetAddr(), GetListenPort()};
    CService addr;
    if (GetLocal(addr, &addrPeer)) {
        ret = CService{addr};
    }
    return ret;
}
 
static int GetnScore(const CService &addr) {
    LOCK(g_maplocalhost_mutex);
    const auto it = mapLocalHost.find(addr);
    return (it != mapLocalHost.end()) ? it->second.nScore : 0;
}
 
// 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() &&
           IsReachable(addrLocal.GetNetwork());
}
 
std::optional<CService> GetLocalAddrForPeer(CNode &node) {
    CService addrLocal{GetLocalAddress(node.addr)};
    if (gArgs.GetBoolArg("-addrmantest", false)) {
        // use IPv4 loopback during addrmantest
        addrLocal = CService(LookupNumeric("127.0.0.1", GetListenPort()));
    }
    // 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(&node) &&
        (!addrLocal.IsRoutable() ||
         rng.randbits((GetnScore(addrLocal) > LOCAL_MANUAL) ? 3 : 1) == 0)) {
        if (node.IsInboundConn()) {
            // For inbound connections, assume both the address and the port
            // as seen from the peer.
            addrLocal = CService{node.GetAddrLocal()};
        } else {
            // For outbound connections, assume just the address as seen from
            // the peer and leave the port in `addrLocal` as returned by
            // `GetLocalAddress()` above. The peer has no way to observe our
            // listening port when we have initiated the connection.
            addrLocal.SetIP(node.GetAddrLocal());
        }
    }
    if (addrLocal.IsRoutable() || gArgs.GetBoolArg("-addrmantest", false)) {
        LogPrint(BCLog::NET, "Advertising address %s to peer=%d\n",
                 addrLocal.ToStringAddrPort(), node.GetId());
        return addrLocal;
    }
    // Address is unroutable. Don't advertise.
    return std::nullopt;
}
 
// 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 (!IsReachable(addr)) {
        return false;
    }
 
    LogPrintf("AddLocal(%s,%i)\n", addr.ToStringAddrPort(), nScore);
 
    {
        LOCK(g_maplocalhost_mutex);
        const auto [it, is_newly_added] =
            mapLocalHost.emplace(addr, LocalServiceInfo());
        LocalServiceInfo &info = it->second;
        if (is_newly_added || nScore >= info.nScore) {
            info.nScore = nScore + !is_newly_added;
            info.nPort = addr.GetPort();
        }
    }
 
    return true;
}
 
bool AddLocal(const CNetAddr &addr, int nScore) {
    return AddLocal(CService(addr, GetListenPort()), nScore);
}
 
void RemoveLocal(const CService &addr) {
    LOCK(g_maplocalhost_mutex);
    LogPrintf("RemoveLocal(%s)\n", addr.ToStringAddrPort());
    mapLocalHost.erase(addr);
}
 
void SetReachable(enum Network net, bool reachable) {
    if (net == NET_UNROUTABLE || net == NET_INTERNAL) {
        return;
    }
    LOCK(g_maplocalhost_mutex);
    vfLimited[net] = !reachable;
}
 
bool IsReachable(enum Network net) {
    LOCK(g_maplocalhost_mutex);
    return !vfLimited[net];
}
 
bool IsReachable(const CNetAddr &addr) {
    return IsReachable(addr.GetNetwork());
}
 
bool SeenLocal(const CService &addr) {
    LOCK(g_maplocalhost_mutex);
    const auto it = mapLocalHost.find(addr);
    if (it == mapLocalHost.end()) {
        return false;
    }
    ++it->second.nScore;
    return true;
}
 
bool IsLocal(const CService &addr) {
    LOCK(g_maplocalhost_mutex);
    return mapLocalHost.count(addr) > 0;
}
 
CNode *CConnman::FindNode(const CNetAddr &ip) {
    LOCK(m_nodes_mutex);
    for (CNode *pnode : m_nodes) {
        if (static_cast<CNetAddr>(pnode->addr) == ip) {
            return pnode;
        }
    }
    return nullptr;
}
 
CNode *CConnman::FindNode(const CSubNet &subNet) {
    LOCK(m_nodes_mutex);
    for (CNode *pnode : m_nodes) {
        if (subNet.Match(static_cast<CNetAddr>(pnode->addr))) {
            return pnode;
        }
    }
    return nullptr;
}
 
CNode *CConnman::FindNode(const std::string &addrName) {
    LOCK(m_nodes_mutex);
    for (CNode *pnode : m_nodes) {
        if (pnode->m_addr_name == addrName) {
            return pnode;
        }
    }
    return nullptr;
}
 
CNode *CConnman::FindNode(const CService &addr) {
    LOCK(m_nodes_mutex);
    for (CNode *pnode : m_nodes) {
        if (static_cast<CService>(pnode->addr) == addr) {
            return pnode;
        }
    }
    return nullptr;
}
 
bool CConnman::AlreadyConnectedToAddress(const CAddress &addr) {
    return FindNode(static_cast<CNetAddr>(addr)) ||
           FindNode(addr.ToStringAddrPort());
}
 
bool CConnman::CheckIncomingNonce(uint64_t nonce) {
    LOCK(m_nodes_mutex);
    for (const CNode *pnode : m_nodes) {
        if (!pnode->fSuccessfullyConnected && !pnode->IsInboundConn() &&
            pnode->GetLocalNonce() == nonce) {
            return false;
        }
    }
    return true;
}
 
static CAddress GetBindAddress(SOCKET sock) {
    CAddress addr_bind;
    struct sockaddr_storage sockaddr_bind;
    socklen_t sockaddr_bind_len = sizeof(sockaddr_bind);
    if (sock != INVALID_SOCKET) {
        if (!getsockname(sock, (struct sockaddr *)&sockaddr_bind,
                         &sockaddr_bind_len)) {
            addr_bind.SetSockAddr((const struct sockaddr *)&sockaddr_bind);
        } else {
            LogPrintLevel(BCLog::NET, BCLog::Level::Warning,
                          "getsockname failed\n");
        }
    }
    return addr_bind;
}
 
CNode *CConnman::ConnectNode(CAddress addrConnect, const char *pszDest,
                             bool fCountFailure, ConnectionType conn_type) {
    assert(conn_type != ConnectionType::INBOUND);
 
    if (pszDest == nullptr) {
        if (IsLocal(addrConnect)) {
            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;
        }
    }
 
    LogPrintLevel(BCLog::NET, BCLog::Level::Debug,
                  "trying connection %s lastseen=%.1fhrs\n",
                  pszDest ? pszDest : addrConnect.ToStringAddrPort(),
                  Ticks<HoursDouble>(
                      pszDest ? 0h : Now<NodeSeconds>() - addrConnect.nTime));
 
    // Resolve
    const uint16_t default_port{pszDest != nullptr
                                    ? Params().GetDefaultPort(pszDest)
                                    : Params().GetDefaultPort()};
    if (pszDest) {
        const std::vector<CService> resolved{Lookup(
            pszDest, default_port, fNameLookup && !HaveNameProxy(), 256)};
        if (!resolved.empty()) {
            addrConnect = CAddress(
                resolved[FastRandomContext().randrange(resolved.size())],
                NODE_NONE);
            if (!addrConnect.IsValid()) {
                LogPrint(BCLog::NET,
                         "Resolver returned invalid address %s for %s\n",
                         addrConnect.ToStringAddrPort(), pszDest);
                return nullptr;
            }
            // It is possible that we already have a connection to the IP/port
            // pszDest resolved to. In that case, drop the connection that was
            // just created.
            LOCK(m_nodes_mutex);
            CNode *pnode = FindNode(static_cast<CService>(addrConnect));
            if (pnode) {
                LogPrintf("Failed to open new connection, already connected\n");
                return nullptr;
            }
        }
    }
 
    // Connect
    bool connected = false;
    std::unique_ptr<Sock> sock;
    proxyType proxy;
    CAddress addr_bind;
    assert(!addr_bind.IsValid());
 
    if (addrConnect.IsValid()) {
        bool proxyConnectionFailed = false;
 
        if (addrConnect.GetNetwork() == NET_I2P &&
            m_i2p_sam_session.get() != nullptr) {
            i2p::Connection conn;
            if (m_i2p_sam_session->Connect(addrConnect, conn,
                                           proxyConnectionFailed)) {
                connected = true;
                sock = std::move(conn.sock);
                addr_bind = CAddress{conn.me, NODE_NONE};
            }
        } else if (GetProxy(addrConnect.GetNetwork(), proxy)) {
            sock = CreateSock(proxy.proxy);
            if (!sock) {
                return nullptr;
            }
            connected = ConnectThroughProxy(
                proxy, addrConnect.ToStringAddr(), addrConnect.GetPort(), *sock,
                nConnectTimeout, proxyConnectionFailed);
        } else {
            // no proxy needed (none set for target network)
            sock = CreateSock(addrConnect);
            if (!sock) {
                return nullptr;
            }
            connected =
                ConnectSocketDirectly(addrConnect, *sock, nConnectTimeout,
                                      conn_type == ConnectionType::MANUAL);
        }
        if (!proxyConnectionFailed) {
            // If a connection to the node was attempted, and failure (if any)
            // is not caused by a problem connecting to the proxy, mark this as
            // an attempt.
            addrman.Attempt(addrConnect, fCountFailure);
        }
    } else if (pszDest && GetNameProxy(proxy)) {
        sock = CreateSock(proxy.proxy);
        if (!sock) {
            return nullptr;
        }
        std::string host;
        uint16_t port{default_port};
        SplitHostPort(std::string(pszDest), port, host);
        bool proxyConnectionFailed;
        connected = ConnectThroughProxy(proxy, host, port, *sock,
                                        nConnectTimeout, proxyConnectionFailed);
    }
    if (!connected) {
        return nullptr;
    }
 
    NetPermissionFlags permission_flags = NetPermissionFlags::None;
    std::vector<NetWhitelistPermissions> whitelist_permissions =
        conn_type == ConnectionType::MANUAL
            ? vWhitelistedRangeOutgoing
            : std::vector<NetWhitelistPermissions>{};
    AddWhitelistPermissionFlags(permission_flags, addrConnect,
                                whitelist_permissions);
 
    // Add node
    NodeId id = GetNewNodeId();
    uint64_t nonce = GetDeterministicRandomizer(RANDOMIZER_ID_LOCALHOSTNONCE)
                         .Write(id)
                         .Finalize();
    uint64_t extra_entropy =
        GetDeterministicRandomizer(RANDOMIZER_ID_EXTRAENTROPY)
            .Write(id)
            .Finalize();
    if (!addr_bind.IsValid()) {
        addr_bind = GetBindAddress(sock->Get());
    }
    CNode *pnode = new CNode(
        id, std::move(sock), addrConnect, CalculateKeyedNetGroup(addrConnect),
        nonce, extra_entropy, addr_bind, pszDest ? pszDest : "", conn_type,
        /* inbound_onion */ false,
        CNodeOptions{
            .permission_flags = permission_flags,
            .recv_flood_size = nReceiveFloodSize,
        });
    pnode->AddRef();
 
    // We're making a new connection, harvest entropy from the time (and our
    // peer count)
    RandAddEvent(uint32_t(id));
 
    return pnode;
}
 
void CNode::CloseSocketDisconnect() {
    fDisconnect = true;
    LOCK(m_sock_mutex);
    if (m_sock) {
        LogPrint(BCLog::NET, "disconnecting peer=%d\n", id);
        m_sock.reset();
    }
}
 
void CConnman::AddWhitelistPermissionFlags(
    NetPermissionFlags &flags, const CNetAddr &addr,
    const std::vector<NetWhitelistPermissions> &ranges) const {
    for (const auto &subnet : ranges) {
        if (subnet.m_subnet.Match(addr)) {
            NetPermissions::AddFlag(flags, subnet.m_flags);
        }
    }
    if (NetPermissions::HasFlag(flags, NetPermissionFlags::Implicit)) {
        NetPermissions::ClearFlag(flags, NetPermissionFlags::Implicit);
        if (whitelist_forcerelay) {
            NetPermissions::AddFlag(flags, NetPermissionFlags::ForceRelay);
        }
        if (whitelist_relay) {
            NetPermissions::AddFlag(flags, NetPermissionFlags::Relay);
        }
        NetPermissions::AddFlag(flags, NetPermissionFlags::Mempool);
        NetPermissions::AddFlag(flags, NetPermissionFlags::NoBan);
    }
}
 
CService CNode::GetAddrLocal() const {
    AssertLockNotHeld(m_addr_local_mutex);
    LOCK(m_addr_local_mutex);
    return addrLocal;
}
 
void CNode::SetAddrLocal(const CService &addrLocalIn) {
    AssertLockNotHeld(m_addr_local_mutex);
    LOCK(m_addr_local_mutex);
    if (addrLocal.IsValid()) {
        LogError(
            "Addr local already set for node: %i. Refusing to change from %s "
            "to %s\n",
            id, addrLocal.ToStringAddrPort(), addrLocalIn.ToStringAddrPort());
    } else {
        addrLocal = addrLocalIn;
    }
}
 
Network CNode::ConnectedThroughNetwork() const {
    return m_inbound_onion ? NET_ONION : addr.GetNetClass();
}
 
void CNode::copyStats(CNodeStats &stats) {
    stats.nodeid = this->GetId();
    stats.addr = addr;
    stats.addrBind = addrBind;
    stats.m_network = ConnectedThroughNetwork();
    stats.m_last_send = m_last_send;
    stats.m_last_recv = m_last_recv;
    stats.m_last_tx_time = m_last_tx_time;
    stats.m_last_proof_time = m_last_proof_time;
    stats.m_last_block_time = m_last_block_time;
    stats.m_connected = m_connected;
    stats.nTimeOffset = nTimeOffset;
    stats.m_addr_name = m_addr_name;
    stats.nVersion = nVersion;
    {
        LOCK(m_subver_mutex);
        stats.cleanSubVer = cleanSubVer;
    }
    stats.fInbound = IsInboundConn();
    stats.m_bip152_highbandwidth_to = m_bip152_highbandwidth_to;
    stats.m_bip152_highbandwidth_from = m_bip152_highbandwidth_from;
    {
        LOCK(cs_vSend);
        stats.mapSendBytesPerMsgType = mapSendBytesPerMsgType;
        stats.nSendBytes = nSendBytes;
    }
    {
        LOCK(cs_vRecv);
        stats.mapRecvBytesPerMsgType = mapRecvBytesPerMsgType;
        stats.nRecvBytes = nRecvBytes;
    }
    stats.m_permission_flags = m_permission_flags;
 
    stats.m_last_ping_time = m_last_ping_time;
    stats.m_min_ping_time = m_min_ping_time;
 
    // Leave string empty if addrLocal invalid (not filled in yet)
    CService addrLocalUnlocked = GetAddrLocal();
    stats.addrLocal =
        addrLocalUnlocked.IsValid() ? addrLocalUnlocked.ToStringAddrPort() : "";
 
    stats.m_conn_type = m_conn_type;
 
    stats.m_availabilityScore = m_avalanche_enabled
                                    ? std::make_optional(getAvailabilityScore())
                                    : std::nullopt;
}
 
bool CNode::ReceiveMsgBytes(const Config &config, Span<const uint8_t> msg_bytes,
                            bool &complete) {
    complete = false;
    const auto time = GetTime<std::chrono::microseconds>();
    LOCK(cs_vRecv);
    m_last_recv = std::chrono::duration_cast<std::chrono::seconds>(time);
    nRecvBytes += msg_bytes.size();
    while (msg_bytes.size() > 0) {
        // Absorb network data.
        int handled = m_deserializer->Read(config, msg_bytes);
        if (handled < 0) {
            return false;
        }
 
        if (m_deserializer->Complete()) {
            // decompose a transport agnostic CNetMessage from the deserializer
            CNetMessage msg = m_deserializer->GetMessage(config, time);
 
            // Store received bytes per message type.
            // To prevent a memory DOS, only allow known message types.
            mapMsgTypeSize::iterator i =
                mapRecvBytesPerMsgType.find(msg.m_type);
            if (i == mapRecvBytesPerMsgType.end()) {
                i = mapRecvBytesPerMsgType.find(NET_MESSAGE_TYPE_OTHER);
            }
 
            assert(i != mapRecvBytesPerMsgType.end());
            i->second += msg.m_raw_message_size;
 
            // push the message to the process queue,
            vRecvMsg.push_back(std::move(msg));
 
            complete = true;
        }
    }
 
    return true;
}
 
int V1TransportDeserializer::readHeader(const Config &config,
                                        Span<const uint8_t> msg_bytes) {
    // copy data to temporary parsing buffer
    uint32_t nRemaining = CMessageHeader::HEADER_SIZE - nHdrPos;
    uint32_t nCopy = std::min<unsigned int>(nRemaining, msg_bytes.size());
 
    memcpy(&hdrbuf[nHdrPos], msg_bytes.data(), nCopy);
    nHdrPos += nCopy;
 
    // if header incomplete, exit
    if (nHdrPos < CMessageHeader::HEADER_SIZE) {
        return nCopy;
    }
 
    // deserialize to CMessageHeader
    try {
        hdrbuf >> hdr;
    } catch (const std::exception &) {
        return -1;
    }
 
    // Reject oversized messages
    if (hdr.IsOversized(config)) {
        LogPrint(BCLog::NET, "Oversized header detected\n");
        return -1;
    }
 
    // switch state to reading message data
    in_data = true;
 
    return nCopy;
}
 
int V1TransportDeserializer::readData(Span<const uint8_t> msg_bytes) {
    unsigned int nRemaining = hdr.nMessageSize - nDataPos;
    unsigned int nCopy = std::min<unsigned int>(nRemaining, msg_bytes.size());
 
    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(msg_bytes.first(nCopy));
    memcpy(&vRecv[nDataPos], msg_bytes.data(), nCopy);
    nDataPos += nCopy;
 
    return nCopy;
}
 
const uint256 &V1TransportDeserializer::GetMessageHash() const {
    assert(Complete());
    if (data_hash.IsNull()) {
        hasher.Finalize(data_hash);
    }
    return data_hash;
}
 
CNetMessage
V1TransportDeserializer::GetMessage(const Config &config,
                                    const std::chrono::microseconds time) {
    // decompose a single CNetMessage from the TransportDeserializer
    CNetMessage msg(std::move(vRecv));
 
    // store state about valid header, netmagic and checksum
    msg.m_valid_header = hdr.IsValid(config);
    // FIXME Split CheckHeaderMagicAndCommand() into CheckHeaderMagic() and
    // CheckCommand() to prevent the net magic check code duplication.
    msg.m_valid_netmagic =
        (memcmp(std::begin(hdr.pchMessageStart),
                std::begin(config.GetChainParams().NetMagic()),
                CMessageHeader::MESSAGE_START_SIZE) == 0);
    uint256 hash = GetMessageHash();
 
    // store message type string, payload size
    msg.m_type = hdr.GetMessageType();
    msg.m_message_size = hdr.nMessageSize;
    msg.m_raw_message_size = hdr.nMessageSize + CMessageHeader::HEADER_SIZE;
 
    // We just received a message off the wire, harvest entropy from the time
    // (and the message checksum)
    RandAddEvent(ReadLE32(hash.begin()));
 
    msg.m_valid_checksum = (memcmp(hash.begin(), hdr.pchChecksum,
                                   CMessageHeader::CHECKSUM_SIZE) == 0);
 
    if (!msg.m_valid_checksum) {
        LogPrint(BCLog::NET,
                 "CHECKSUM ERROR (%s, %u bytes), expected %s was %s\n",
                 SanitizeString(msg.m_type), msg.m_message_size,
                 HexStr(Span{hash}.first(CMessageHeader::CHECKSUM_SIZE)),
                 HexStr(hdr.pchChecksum));
    }
 
    // store receive time
    msg.m_time = time;
 
    // reset the network deserializer (prepare for the next message)
    Reset();
    return msg;
}
 
void V1TransportSerializer::prepareForTransport(
    const Config &config, CSerializedNetMsg &msg,
    std::vector<uint8_t> &header) const {
    // create dbl-sha256 checksum
    uint256 hash = Hash(msg.data);
 
    // create header
    CMessageHeader hdr(config.GetChainParams().NetMagic(), msg.m_type.c_str(),
                       msg.data.size());
    memcpy(hdr.pchChecksum, hash.begin(), CMessageHeader::CHECKSUM_SIZE);
 
    // serialize header
    header.reserve(CMessageHeader::HEADER_SIZE);
    VectorWriter{header, 0, hdr};
}
 
std::pair<size_t, bool> CConnman::SocketSendData(CNode &node) const {
    size_t nSentSize = 0;
    size_t nMsgCount = 0;
 
    for (auto it = node.vSendMsg.begin(); it != node.vSendMsg.end(); ++it) {
        const auto &data = *it;
        assert(data.size() > node.nSendOffset);
        int nBytes = 0;
 
        {
            LOCK(node.m_sock_mutex);
            if (!node.m_sock) {
                break;
            }
            int flags = MSG_NOSIGNAL | MSG_DONTWAIT;
#ifdef MSG_MORE
            if (it + 1 != node.vSendMsg.end()) {
                flags |= MSG_MORE;
            }
#endif
            nBytes = node.m_sock->Send(
                reinterpret_cast<const char *>(data.data()) + node.nSendOffset,
                data.size() - node.nSendOffset, flags);
        }
 
        if (nBytes == 0) {
            // couldn't send anything at all
            break;
        }
 
        if (nBytes < 0) {
            // error
            int nErr = WSAGetLastError();
            if (nErr != WSAEWOULDBLOCK && nErr != WSAEMSGSIZE &&
                nErr != WSAEINTR && nErr != WSAEINPROGRESS) {
                LogPrint(BCLog::NET, "socket send error for peer=%d: %s\n",
                         node.GetId(), NetworkErrorString(nErr));
                node.CloseSocketDisconnect();
            }
 
            break;
        }
 
        assert(nBytes > 0);
        node.m_last_send = GetTime<std::chrono::seconds>();
        node.nSendBytes += nBytes;
        node.nSendOffset += nBytes;
        nSentSize += nBytes;
        if (node.nSendOffset != data.size()) {
            // could not send full message; stop sending more
            break;
        }
 
        node.nSendOffset = 0;
        node.nSendSize -= data.size();
        node.fPauseSend = node.nSendSize > nSendBufferMaxSize;
        nMsgCount++;
    }
 
    node.vSendMsg.erase(node.vSendMsg.begin(),
                        node.vSendMsg.begin() + nMsgCount);
 
    if (node.vSendMsg.empty()) {
        assert(node.nSendOffset == 0);
        assert(node.nSendSize == 0);
    }
 
    return {nSentSize, !node.vSendMsg.empty()};
}
bool CConnman::AttemptToEvictConnection() {
    std::vector<NodeEvictionCandidate> vEvictionCandidates;
    {
        LOCK(m_nodes_mutex);
        for (const CNode *node : m_nodes) {
            if (node->fDisconnect) {
                continue;
            }
 
            NodeEvictionCandidate candidate = {
                .id = node->GetId(),
                .m_connected = node->m_connected,
                .m_min_ping_time = node->m_min_ping_time,
                .m_last_block_time = node->m_last_block_time,
                .m_last_proof_time = node->m_last_proof_time,
                .m_last_tx_time = node->m_last_tx_time,
                .fRelevantServices = node->m_has_all_wanted_services,
                .m_relay_txs = node->m_relays_txs.load(),
                .fBloomFilter = node->m_bloom_filter_loaded.load(),
                .nKeyedNetGroup = node->nKeyedNetGroup,
                .prefer_evict = node->m_prefer_evict,
                .m_is_local = node->addr.IsLocal(),
                .m_network = node->ConnectedThroughNetwork(),
                .m_noban = node->HasPermission(NetPermissionFlags::NoBan),
                .m_conn_type = node->m_conn_type,
                .availabilityScore =
                    node->m_avalanche_enabled
                        ? node->getAvailabilityScore()
                        : -std::numeric_limits<double>::infinity()};
            vEvictionCandidates.push_back(candidate);
        }
    }
    const std::optional<NodeId> node_id_to_evict =
        SelectNodeToEvict(std::move(vEvictionCandidates));
    if (!node_id_to_evict) {
        return false;
    }
    LOCK(m_nodes_mutex);
    for (CNode *pnode : m_nodes) {
        if (pnode->GetId() == *node_id_to_evict) {
            LogPrint(
                BCLog::NET,
                "selected %s connection for eviction peer=%d; disconnecting\n",
                pnode->ConnectionTypeAsString(), pnode->GetId());
            pnode->fDisconnect = true;
            return true;
        }
    }
    return false;
}
 
void CConnman::AcceptConnection(const ListenSocket &hListenSocket) {
    struct sockaddr_storage sockaddr;
    socklen_t len = sizeof(sockaddr);
    auto sock = hListenSocket.sock->Accept((struct sockaddr *)&sockaddr, &len);
    CAddress addr;
 
    if (!sock) {
        const int nErr = WSAGetLastError();
        if (nErr != WSAEWOULDBLOCK) {
            LogPrintf("socket error accept failed: %s\n",
                      NetworkErrorString(nErr));
        }
        return;
    }
 
    if (!addr.SetSockAddr((const struct sockaddr *)&sockaddr)) {
        LogPrintLevel(BCLog::NET, BCLog::Level::Warning,
                      "Unknown socket family\n");
    }
 
    const CAddress addr_bind = GetBindAddress(sock->Get());
 
    NetPermissionFlags permission_flags = NetPermissionFlags::None;
    hListenSocket.AddSocketPermissionFlags(permission_flags);
 
    CreateNodeFromAcceptedSocket(std::move(sock), permission_flags, addr_bind,
                                 addr);
}
 
void CConnman::CreateNodeFromAcceptedSocket(std::unique_ptr<Sock> &&sock,
                                            NetPermissionFlags permission_flags,
                                            const CAddress &addr_bind,
                                            const CAddress &addr) {
    int nInbound = 0;
    int nMaxInbound = nMaxConnections - m_max_outbound;
 
    AddWhitelistPermissionFlags(permission_flags, addr,
                                vWhitelistedRangeIncoming);
 
    {
        LOCK(m_nodes_mutex);
        for (const CNode *pnode : m_nodes) {
            if (pnode->IsInboundConn()) {
                nInbound++;
            }
        }
    }
 
    if (!fNetworkActive) {
        LogPrint(BCLog::NET,
                 "connection from %s dropped: not accepting new connections\n",
                 addr.ToStringAddrPort());
        return;
    }
 
    if (!IsSelectableSocket(sock->Get())) {
        LogPrintf("connection from %s dropped: non-selectable socket\n",
                  addr.ToStringAddrPort());
        return;
    }
 
    // According to the internet TCP_NODELAY is not carried into accepted
    // sockets on all platforms.  Set it again here just to be sure.
    SetSocketNoDelay(sock->Get());
 
    // Don't accept connections from banned peers.
    bool banned = m_banman && m_banman->IsBanned(addr);
    if (!NetPermissions::HasFlag(permission_flags, NetPermissionFlags::NoBan) &&
        banned) {
        LogPrint(BCLog::NET, "connection from %s dropped (banned)\n",
                 addr.ToStringAddrPort());
        return;
    }
 
    // Only accept connections from discouraged peers if our inbound slots
    // aren't (almost) full.
    bool discouraged = m_banman && m_banman->IsDiscouraged(addr);
    if (!NetPermissions::HasFlag(permission_flags, NetPermissionFlags::NoBan) &&
        nInbound + 1 >= nMaxInbound && discouraged) {
        LogPrint(BCLog::NET, "connection from %s dropped (discouraged)\n",
                 addr.ToStringAddrPort());
        return;
    }
 
    if (nInbound >= nMaxInbound) {
        if (!AttemptToEvictConnection()) {
            // No connection to evict, disconnect the new connection
            LogPrint(BCLog::NET, "failed to find an eviction candidate - "
                                 "connection dropped (full)\n");
            return;
        }
    }
 
    NodeId id = GetNewNodeId();
    uint64_t nonce = GetDeterministicRandomizer(RANDOMIZER_ID_LOCALHOSTNONCE)
                         .Write(id)
                         .Finalize();
    uint64_t extra_entropy =
        GetDeterministicRandomizer(RANDOMIZER_ID_EXTRAENTROPY)
            .Write(id)
            .Finalize();
 
    const bool inbound_onion =
        std::find(m_onion_binds.begin(), m_onion_binds.end(), addr_bind) !=
        m_onion_binds.end();
    CNode *pnode = new CNode(
        id, std::move(sock), addr, CalculateKeyedNetGroup(addr), nonce,
        extra_entropy, addr_bind, "", ConnectionType::INBOUND, inbound_onion,
        CNodeOptions{
            .permission_flags = permission_flags,
            .prefer_evict = discouraged,
            .recv_flood_size = nReceiveFloodSize,
        });
    pnode->AddRef();
    for (auto interface : m_msgproc) {
        interface->InitializeNode(*config, *pnode, GetLocalServices());
    }
 
    LogPrint(BCLog::NET, "connection from %s accepted\n",
             addr.ToStringAddrPort());
 
    {
        LOCK(m_nodes_mutex);
        m_nodes.push_back(pnode);
    }
 
    // We received a new connection, harvest entropy from the time (and our peer
    // count)
    RandAddEvent(uint32_t(id));
}
 
bool CConnman::AddConnection(const std::string &address,
                             ConnectionType conn_type) {
    std::optional<int> max_connections;
    switch (conn_type) {
        case ConnectionType::INBOUND:
        case ConnectionType::MANUAL:
            return false;
        case ConnectionType::OUTBOUND_FULL_RELAY:
            max_connections = m_max_outbound_full_relay;
            break;
        case ConnectionType::BLOCK_RELAY:
            max_connections = m_max_outbound_block_relay;
            break;
        // no limit for ADDR_FETCH because -seednode has no limit either
        case ConnectionType::ADDR_FETCH:
            break;
        // no limit for FEELER connections since they're short-lived
        case ConnectionType::FEELER:
            break;
        case ConnectionType::AVALANCHE_OUTBOUND:
            max_connections = m_max_avalanche_outbound;
            break;
    } // no default case, so the compiler can warn about missing cases
 
    // Count existing connections
    int existing_connections =
        WITH_LOCK(m_nodes_mutex,
                  return std::count_if(
                      m_nodes.begin(), m_nodes.end(), [conn_type](CNode *node) {
                          return node->m_conn_type == conn_type;
                      }););
 
    // Max connections of specified type already exist
    if (max_connections != std::nullopt &&
        existing_connections >= max_connections) {
        return false;
    }
 
    // Max total outbound connections already exist
    CSemaphoreGrant grant(*semOutbound, true);
    if (!grant) {
        return false;
    }
 
    OpenNetworkConnection(CAddress(), false, &grant, address.c_str(),
                          conn_type);
    return true;
}
 
void CConnman::DisconnectNodes() {
    {
        LOCK(m_nodes_mutex);
 
        if (!fNetworkActive) {
            // Disconnect any connected nodes
            for (CNode *pnode : m_nodes) {
                if (!pnode->fDisconnect) {
                    LogPrint(BCLog::NET,
                             "Network not active, dropping peer=%d\n",
                             pnode->GetId());
                    pnode->fDisconnect = true;
                }
            }
        }
 
        // Disconnect unused nodes
        std::vector<CNode *> nodes_copy = m_nodes;
        for (CNode *pnode : nodes_copy) {
            if (pnode->fDisconnect) {
                // remove from m_nodes
                m_nodes.erase(remove(m_nodes.begin(), m_nodes.end(), pnode),
                              m_nodes.end());
 
                // release outbound grant (if any)
                pnode->grantOutbound.Release();
 
                // close socket and cleanup
                pnode->CloseSocketDisconnect();
 
                // hold in disconnected pool until all refs are released
                pnode->Release();
                m_nodes_disconnected.push_back(pnode);
            }
        }
    }
    {
        // Delete disconnected nodes
        std::list<CNode *> nodes_disconnected_copy = m_nodes_disconnected;
        for (CNode *pnode : nodes_disconnected_copy) {
            // Destroy the object only after other threads have stopped using
            // it.
            if (pnode->GetRefCount() <= 0) {
                m_nodes_disconnected.remove(pnode);
                DeleteNode(pnode);
            }
        }
    }
}
 
void CConnman::NotifyNumConnectionsChanged() {
    size_t nodes_size;
    {
        LOCK(m_nodes_mutex);
        nodes_size = m_nodes.size();
    }
    if (nodes_size != nPrevNodeCount) {
        nPrevNodeCount = nodes_size;
        if (m_client_interface) {
            m_client_interface->NotifyNumConnectionsChanged(nodes_size);
        }
    }
}
 
bool CConnman::ShouldRunInactivityChecks(const CNode &node,
                                         std::chrono::seconds now) const {
    return node.m_connected + m_peer_connect_timeout < now;
}
 
bool CConnman::InactivityCheck(const CNode &node) const {
    // Tests that see disconnects after using mocktime can start nodes with a
    // large timeout. For example, -peertimeout=999999999.
    const auto now{GetTime<std::chrono::seconds>()};
    const auto last_send{node.m_last_send.load()};
    const auto last_recv{node.m_last_recv.load()};
 
    if (!ShouldRunInactivityChecks(node, now)) {
        return false;
    }
 
    if (last_recv.count() == 0 || last_send.count() == 0) {
        LogPrint(BCLog::NET,
                 "socket no message in first %i seconds, %d %d peer=%d\n",
                 count_seconds(m_peer_connect_timeout), last_recv.count() != 0,
                 last_send.count() != 0, node.GetId());
        return true;
    }
 
    if (now > last_send + TIMEOUT_INTERVAL) {
        LogPrint(BCLog::NET, "socket sending timeout: %is peer=%d\n",
                 count_seconds(now - last_send), node.GetId());
        return true;
    }
 
    if (now > last_recv + TIMEOUT_INTERVAL) {
        LogPrint(BCLog::NET, "socket receive timeout: %is peer=%d\n",
                 count_seconds(now - last_recv), node.GetId());
        return true;
    }
 
    if (!node.fSuccessfullyConnected) {
        LogPrint(BCLog::NET, "version handshake timeout peer=%d\n",
                 node.GetId());
        return true;
    }
 
    return false;
}
 
Sock::EventsPerSock CConnman::GenerateWaitSockets(Span<CNode *const> nodes) {
    Sock::EventsPerSock events_per_sock;
 
    for (const ListenSocket &hListenSocket : vhListenSocket) {
        events_per_sock.emplace(hListenSocket.sock, Sock::Events{Sock::RECV});
    }
 
    for (CNode *pnode : nodes) {
        bool select_recv = !pnode->fPauseRecv;
        bool select_send =
            WITH_LOCK(pnode->cs_vSend, return !pnode->vSendMsg.empty());
        if (!select_recv && !select_send) {
            continue;
        }
 
        LOCK(pnode->m_sock_mutex);
        if (pnode->m_sock) {
            Sock::Event event =
                (select_send ? Sock::SEND : 0) | (select_recv ? Sock::RECV : 0);
            events_per_sock.emplace(pnode->m_sock, Sock::Events{event});
        }
    }
 
    return events_per_sock;
}
 
void CConnman::SocketHandler() {
    Sock::EventsPerSock events_per_sock;
 
    {
        const NodesSnapshot snap{*this, /*shuffle=*/false};
 
        const auto timeout =
            std::chrono::milliseconds(SELECT_TIMEOUT_MILLISECONDS);
 
        // Check for the readiness of the already connected sockets and the
        // listening sockets in one call ("readiness" as in poll(2) or
        // select(2)). If none are ready, wait for a short while and return
        // empty sets.
        events_per_sock = GenerateWaitSockets(snap.Nodes());
        if (events_per_sock.empty() ||
            !events_per_sock.begin()->first->WaitMany(timeout,
                                                      events_per_sock)) {
            interruptNet.sleep_for(timeout);
        }
 
        // Service (send/receive) each of the already connected nodes.
        SocketHandlerConnected(snap.Nodes(), events_per_sock);
    }
 
    // Accept new connections from listening sockets.
    SocketHandlerListening(events_per_sock);
}
 
void CConnman::SocketHandlerConnected(
    const std::vector<CNode *> &nodes,
    const Sock::EventsPerSock &events_per_sock) {
    for (CNode *pnode : nodes) {
        if (interruptNet) {
            return;
        }
 
        //
        // Receive
        //
        bool recvSet = false;
        bool sendSet = false;
        bool errorSet = false;
        {
            LOCK(pnode->m_sock_mutex);
            if (!pnode->m_sock) {
                continue;
            }
            const auto it = events_per_sock.find(pnode->m_sock);
            if (it != events_per_sock.end()) {
                recvSet = it->second.occurred & Sock::RECV;
                sendSet = it->second.occurred & Sock::SEND;
                errorSet = it->second.occurred & Sock::ERR;
            }
        }
 
        if (sendSet) {
            // Send data
            auto [bytes_sent, data_left] =
                WITH_LOCK(pnode->cs_vSend, return SocketSendData(*pnode));
            if (bytes_sent) {
                RecordBytesSent(bytes_sent);
 
                // If both receiving and (non-optimistic) sending were possible,
                // we first attempt sending. If that succeeds, but does not
                // fully drain the send queue, do not attempt to receive. This
                // avoids needlessly queueing data if the remote peer is slow at
                // receiving data, by means of TCP flow control. We only do this
                // when sending actually succeeded to make sure progress is
                // always made; otherwise a deadlock would be possible when both
                // sides have data to send, but neither is receiving.
                if (data_left) {
                    recvSet = false;
                }
            }
        }
 
        if (recvSet || errorSet) {
            // typical socket buffer is 8K-64K
            uint8_t pchBuf[0x10000];
            int32_t nBytes = 0;
            {
                LOCK(pnode->m_sock_mutex);
                if (!pnode->m_sock) {
                    continue;
                }
                nBytes =
                    pnode->m_sock->Recv(pchBuf, sizeof(pchBuf), MSG_DONTWAIT);
            }
            if (nBytes > 0) {
                bool notify = false;
                if (!pnode->ReceiveMsgBytes(*config, {pchBuf, (size_t)nBytes},
                                            notify)) {
                    pnode->CloseSocketDisconnect();
                }
                RecordBytesRecv(nBytes);
                if (notify) {
                    pnode->MarkReceivedMsgsForProcessing();
                    WakeMessageHandler();
                }
            } else if (nBytes == 0) {
                // socket closed gracefully
                if (!pnode->fDisconnect) {
                    LogPrint(BCLog::NET, "socket closed for peer=%d\n",
                             pnode->GetId());
                }
                pnode->CloseSocketDisconnect();
            } else if (nBytes < 0) {
                // error
                int nErr = WSAGetLastError();
                if (nErr != WSAEWOULDBLOCK && nErr != WSAEMSGSIZE &&
                    nErr != WSAEINTR && nErr != WSAEINPROGRESS) {
                    if (!pnode->fDisconnect) {
                        LogPrint(BCLog::NET,
                                 "socket recv error for peer=%d: %s\n",
                                 pnode->GetId(), NetworkErrorString(nErr));
                    }
                    pnode->CloseSocketDisconnect();
                }
            }
        }
 
        if (InactivityCheck(*pnode)) {
            pnode->fDisconnect = true;
        }
    }
}
 
void CConnman::SocketHandlerListening(
    const Sock::EventsPerSock &events_per_sock) {
    for (const ListenSocket &listen_socket : vhListenSocket) {
        if (interruptNet) {
            return;
        }
        const auto it = events_per_sock.find(listen_socket.sock);
        if (it != events_per_sock.end() && it->second.occurred & Sock::RECV) {
            AcceptConnection(listen_socket);
        }
    }
}
 
void CConnman::ThreadSocketHandler() {
    while (!interruptNet) {
        DisconnectNodes();
        NotifyNumConnectionsChanged();
        SocketHandler();
    }
}
 
void CConnman::WakeMessageHandler() {
    {
        LOCK(mutexMsgProc);
        fMsgProcWake = true;
    }
    condMsgProc.notify_one();
}
 
void CConnman::ThreadDNSAddressSeed() {
    FastRandomContext rng;
    std::vector<std::string> seeds =
        GetRandomizedDNSSeeds(config->GetChainParams());
    // Number of seeds left before testing if we have enough connections
    int seeds_right_now = 0;
    int found = 0;
 
    if (gArgs.GetBoolArg("-forcednsseed", DEFAULT_FORCEDNSSEED)) {
        // When -forcednsseed is provided, query all.
        seeds_right_now = seeds.size();
    } else if (addrman.size() == 0) {
        // If we have no known peers, query all.
        // This will occur on the first run, or if peers.dat has been
        // deleted.
        seeds_right_now = seeds.size();
    }
 
    // goal: only query DNS seed if address need is acute
    // * If we have a reasonable number of peers in addrman, spend
    //   some time trying them first. This improves user privacy by
    //   creating fewer identifying DNS requests, reduces trust by
    //   giving seeds less influence on the network topology, and
    //   reduces traffic to the seeds.
    // * When querying DNS seeds query a few at once, this ensures
    //   that we don't give DNS seeds the ability to eclipse nodes
    //   that query them.
    // * If we continue having problems, eventually query all the
    //   DNS seeds, and if that fails too, also try the fixed seeds.
    //   (done in ThreadOpenConnections)
    const std::chrono::seconds seeds_wait_time =
        (addrman.size() >= DNSSEEDS_DELAY_PEER_THRESHOLD
             ? DNSSEEDS_DELAY_MANY_PEERS
             : DNSSEEDS_DELAY_FEW_PEERS);
 
    for (const std::string &seed : seeds) {
        if (seeds_right_now == 0) {
            seeds_right_now += DNSSEEDS_TO_QUERY_AT_ONCE;
 
            if (addrman.size() > 0) {
                LogPrintf("Waiting %d seconds before querying DNS seeds.\n",
                          seeds_wait_time.count());
                std::chrono::seconds to_wait = seeds_wait_time;
                while (to_wait.count() > 0) {
                    // if sleeping for the MANY_PEERS interval, wake up
                    // early to see if we have enough peers and can stop
                    // this thread entirely freeing up its resources
                    std::chrono::seconds w =
                        std::min(DNSSEEDS_DELAY_FEW_PEERS, to_wait);
                    if (!interruptNet.sleep_for(w)) {
                        return;
                    }
                    to_wait -= w;
 
                    int nRelevant = 0;
                    {
                        LOCK(m_nodes_mutex);
                        for (const CNode *pnode : m_nodes) {
                            if (pnode->fSuccessfullyConnected &&
                                pnode->IsFullOutboundConn()) {
                                ++nRelevant;
                            }
                        }
                    }
                    if (nRelevant >= 2) {
                        if (found > 0) {
                            LogPrintf("%d addresses found from DNS seeds\n",
                                      found);
                            LogPrintf(
                                "P2P peers available. Finished DNS seeding.\n");
                        } else {
                            LogPrintf(
                                "P2P peers available. Skipped DNS seeding.\n");
                        }
                        return;
                    }
                }
            }
        }
 
        if (interruptNet) {
            return;
        }
 
        // hold off on querying seeds if P2P network deactivated
        if (!fNetworkActive) {
            LogPrintf("Waiting for network to be reactivated before querying "
                      "DNS seeds.\n");
            do {
                if (!interruptNet.sleep_for(std::chrono::seconds{1})) {
                    return;
                }
            } while (!fNetworkActive);
        }
 
        LogPrintf("Loading addresses from DNS seed %s\n", seed);
        if (HaveNameProxy()) {
            AddAddrFetch(seed);
        } else {
            std::vector<CAddress> vAdd;
            ServiceFlags requiredServiceBits =
                GetDesirableServiceFlags(NODE_NONE);
            std::string host = strprintf("x%x.%s", requiredServiceBits, seed);
            CNetAddr resolveSource;
            if (!resolveSource.SetInternal(host)) {
                continue;
            }
 
            // Limits number of IPs learned from a DNS seed
            unsigned int nMaxIPs = 256;
            const auto addresses{LookupHost(host, nMaxIPs, true)};
            if (!addresses.empty()) {
                for (const CNetAddr &ip : addresses) {
                    CAddress addr = CAddress(
                        CService(ip, config->GetChainParams().GetDefaultPort()),
                        requiredServiceBits);
                    // Use a random age between 3 and 7 days old.
                    addr.nTime = rng.rand_uniform_delay(
                        Now<NodeSeconds>() - 3 * 24h, -4 * 24h);
                    vAdd.push_back(addr);
                    found++;
                }
                addrman.Add(vAdd, resolveSource);
            } else {
                // We now avoid directly using results from DNS Seeds which do
                // not support service bit filtering, instead using them as a
                // addrfetch to get nodes with our desired service bits.
                AddAddrFetch(seed);
            }
        }
        --seeds_right_now;
    }
    LogPrintf("%d addresses found from DNS seeds\n", found);
}
 
void CConnman::DumpAddresses() {
    int64_t nStart = GetTimeMillis();
 
    DumpPeerAddresses(config->GetChainParams(), ::gArgs, addrman);
 
    LogPrint(BCLog::NET, "Flushed %d addresses to peers.dat  %dms\n",
             addrman.size(), GetTimeMillis() - nStart);
}
 
void CConnman::ProcessAddrFetch() {
    std::string strDest;
    {
        LOCK(m_addr_fetches_mutex);
        if (m_addr_fetches.empty()) {
            return;
        }
        strDest = m_addr_fetches.front();
        m_addr_fetches.pop_front();
    }
    CAddress addr;
    CSemaphoreGrant grant(*semOutbound, true);
    if (grant) {
        OpenNetworkConnection(addr, false, &grant, strDest.c_str(),
                              ConnectionType::ADDR_FETCH);
    }
}
 
bool CConnman::GetTryNewOutboundPeer() const {
    return m_try_another_outbound_peer;
}
 
void CConnman::SetTryNewOutboundPeer(bool flag) {
    m_try_another_outbound_peer = flag;
    LogPrint(BCLog::NET, "net: setting try another outbound peer=%s\n",
             flag ? "true" : "false");
}
 
// Return the number of peers we have over our outbound connection limit.
// Exclude peers that are marked for disconnect, or are going to be disconnected
// soon (eg ADDR_FETCH and FEELER).
// Also exclude peers that haven't finished initial connection handshake yet (so
// that we don't decide we're over our desired connection limit, and then evict
// some peer that has finished the handshake).
int CConnman::GetExtraFullOutboundCount() const {
    int full_outbound_peers = 0;
    {
        LOCK(m_nodes_mutex);
        for (const CNode *pnode : m_nodes) {
            if (pnode->fSuccessfullyConnected && !pnode->fDisconnect &&
                pnode->IsFullOutboundConn()) {
                ++full_outbound_peers;
            }
        }
    }
    return std::max(full_outbound_peers - m_max_outbound_full_relay -
                        m_max_avalanche_outbound,
                    0);
}
 
int CConnman::GetExtraBlockRelayCount() const {
    int block_relay_peers = 0;
    {
        LOCK(m_nodes_mutex);
        for (const CNode *pnode : m_nodes) {
            if (pnode->fSuccessfullyConnected && !pnode->fDisconnect &&
                pnode->IsBlockOnlyConn()) {
                ++block_relay_peers;
            }
        }
    }
    return std::max(block_relay_peers - m_max_outbound_block_relay, 0);
}
 
void CConnman::ThreadOpenConnections(
    const std::vector<std::string> connect,
    std::function<void(const CAddress &, ConnectionType)> mockOpenConnection) {
    FastRandomContext rng;
    // Connect to specific addresses
    if (!connect.empty()) {
        for (int64_t nLoop = 0;; nLoop++) {
            ProcessAddrFetch();
            for (const std::string &strAddr : connect) {
                CAddress addr(CService(), NODE_NONE);
                OpenNetworkConnection(addr, false, nullptr, strAddr.c_str(),
                                      ConnectionType::MANUAL);
                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
    auto start = GetTime<std::chrono::microseconds>();
 
    // Minimum time before next feeler connection (in microseconds
    auto next_feeler = start + rng.rand_exp_duration(FEELER_INTERVAL);
    auto next_extra_block_relay =
        start + rng.rand_exp_duration(EXTRA_BLOCK_RELAY_ONLY_PEER_INTERVAL);
    const bool dnsseed = gArgs.GetBoolArg("-dnsseed", DEFAULT_DNSSEED);
    bool add_fixed_seeds = gArgs.GetBoolArg("-fixedseeds", DEFAULT_FIXEDSEEDS);
    const bool use_seednodes{gArgs.IsArgSet("-seednode")};
 
    if (!add_fixed_seeds) {
        LogPrintf("Fixed seeds are disabled\n");
    }
 
    while (!interruptNet) {
        ProcessAddrFetch();
 
        // No need to sleep the thread if we are mocking the network connection
        if (!mockOpenConnection &&
            !interruptNet.sleep_for(std::chrono::milliseconds(500))) {
            return;
        }
 
        CSemaphoreGrant grant(*semOutbound);
        if (interruptNet) {
            return;
        }
 
        if (add_fixed_seeds && addrman.size() == 0) {
            // When the node starts with an empty peers.dat, there are a few
            // other sources of peers before we fallback on to fixed seeds:
            // -dnsseed, -seednode, -addnode If none of those are available, we
            // fallback on to fixed seeds immediately, else we allow 60 seconds
            // for any of those sources to populate addrman.
            bool add_fixed_seeds_now = false;
            // It is cheapest to check if enough time has passed first.
            if (GetTime<std::chrono::seconds>() >
                start + std::chrono::minutes{1}) {
                add_fixed_seeds_now = true;
                LogPrintf("Adding fixed seeds as 60 seconds have passed and "
                          "addrman is empty\n");
            } else if (!dnsseed && !use_seednodes) {
                // Lock the mutex after performing the above cheap checks.
                LOCK(m_added_nodes_mutex);
                if (m_added_nodes.empty()) {
                    add_fixed_seeds_now = true;
                    LogPrintf("Adding fixed seeds as -dnsseed=0 and neither "
                              "-addnode nor -seednode are provided\n");
                }
            }
 
            if (add_fixed_seeds_now) {
                CNetAddr local;
                local.SetInternal("fixedseeds");
                addrman.Add(convertSeed6(config->GetChainParams().FixedSeeds()),
                            local);
                add_fixed_seeds = false;
            }
        }
 
        //
        // 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).
        int nOutboundFullRelay = 0;
        int nOutboundBlockRelay = 0;
        int nOutboundAvalanche = 0;
        std::set<std::vector<uint8_t>> setConnected;
 
        {
            LOCK(m_nodes_mutex);
            for (const CNode *pnode : m_nodes) {
                if (pnode->IsAvalancheOutboundConnection()) {
                    nOutboundAvalanche++;
                } else if (pnode->IsFullOutboundConn()) {
                    nOutboundFullRelay++;
                } else if (pnode->IsBlockOnlyConn()) {
                    nOutboundBlockRelay++;
                }
 
                // Netgroups for inbound and manual peers are not excluded
                // because our goal here is to not use multiple of our
                // limited outbound slots on a single netgroup but inbound
                // and manual peers do not use our outbound slots. Inbound
                // peers also have the added issue that they could be attacker
                // controlled and could be used to prevent us from connecting
                // to particular hosts if we used them here.
                switch (pnode->m_conn_type) {
                    case ConnectionType::INBOUND:
                    case ConnectionType::MANUAL:
                        break;
                    case ConnectionType::AVALANCHE_OUTBOUND:
                    case ConnectionType::OUTBOUND_FULL_RELAY:
                    case ConnectionType::BLOCK_RELAY:
                    case ConnectionType::ADDR_FETCH:
                    case ConnectionType::FEELER:
                        setConnected.insert(
                            pnode->addr.GetGroup(addrman.GetAsmap()));
                } // no default case, so the compiler can warn about missing
                  // cases
            }
        }
 
        ConnectionType conn_type = ConnectionType::OUTBOUND_FULL_RELAY;
        auto now = GetTime<std::chrono::microseconds>();
        bool anchor = false;
        bool fFeeler = false;
 
        // Determine what type of connection to open. Opening
        // BLOCK_RELAY connections to addresses from anchors.dat gets the
        // highest priority. Then we open AVALANCHE_OUTBOUND connection until we
        // hit our avalanche outbound peer limit, which is 0 if avalanche is not
        // enabled. We fallback after 50 retries to OUTBOUND_FULL_RELAY if the
        // peer is not avalanche capable until we meet our full-relay capacity.
        // Then we open BLOCK_RELAY connection until we hit our block-relay-only
        // peer limit.
        // GetTryNewOutboundPeer() gets set when a stale tip is detected, so we
        // try opening an additional OUTBOUND_FULL_RELAY connection. If none of
        // these conditions are met, check to see if it's time to try an extra
        // block-relay-only peer (to confirm our tip is current, see below) or
        // the next_feeler timer to decide if we should open a FEELER.
 
        if (!m_anchors.empty() &&
            (nOutboundBlockRelay < m_max_outbound_block_relay)) {
            conn_type = ConnectionType::BLOCK_RELAY;
            anchor = true;
        } else if (nOutboundAvalanche < m_max_avalanche_outbound) {
            conn_type = ConnectionType::AVALANCHE_OUTBOUND;
        } else if (nOutboundFullRelay < m_max_outbound_full_relay) {
            // OUTBOUND_FULL_RELAY
        } else if (nOutboundBlockRelay < m_max_outbound_block_relay) {
            conn_type = ConnectionType::BLOCK_RELAY;
        } else if (GetTryNewOutboundPeer()) {
            // OUTBOUND_FULL_RELAY
        } else if (now > next_extra_block_relay &&
                   m_start_extra_block_relay_peers) {
            // Periodically connect to a peer (using regular outbound selection
            // methodology from addrman) and stay connected long enough to sync
            // headers, but not much else.
            //
            // Then disconnect the peer, if we haven't learned anything new.
            //
            // The idea is to make eclipse attacks very difficult to pull off,
            // because every few minutes we're finding a new peer to learn
            // headers from.
            //
            // This is similar to the logic for trying extra outbound
            // (full-relay) peers, except:
            // - we do this all the time on an exponential timer, rather than
            //   just  when our tip is stale
            // - we potentially disconnect our next-youngest block-relay-only
            //   peer, if our newest block-relay-only peer delivers a block more
            //   recently.
            //   See the eviction logic in net_processing.cpp.
            //
            // Because we can promote these connections to block-relay-only
            // connections, they do not get their own ConnectionType enum
            // (similar to how we deal with extra outbound peers).
            next_extra_block_relay =
                now +
                rng.rand_exp_duration(EXTRA_BLOCK_RELAY_ONLY_PEER_INTERVAL);
            conn_type = ConnectionType::BLOCK_RELAY;
        } else if (now > next_feeler) {
            next_feeler = now + rng.rand_exp_duration(FEELER_INTERVAL);
            conn_type = ConnectionType::FEELER;
            fFeeler = true;
        } else {
            // skip to next iteration of while loop
            continue;
        }
 
        addrman.ResolveCollisions();
 
        const auto current_time{NodeClock::now()};
        int nTries = 0;
        while (!interruptNet) {
            if (anchor && !m_anchors.empty()) {
                const CAddress addr = m_anchors.back();
                m_anchors.pop_back();
                if (!addr.IsValid() || IsLocal(addr) || !IsReachable(addr) ||
                    !HasAllDesirableServiceFlags(addr.nServices) ||
                    setConnected.count(addr.GetGroup(addrman.GetAsmap()))) {
                    continue;
                }
                addrConnect = addr;
                LogPrint(BCLog::NET,
                         "Trying to make an anchor connection to %s\n",
                         addrConnect.ToStringAddrPort());
                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;
            }
 
            CAddress addr;
            NodeSeconds addr_last_try{0s};
 
            if (fFeeler) {
                // First, try to get a tried table collision address. This
                // returns an empty (invalid) address if there are no collisions
                // to try.
                std::tie(addr, addr_last_try) = addrman.SelectTriedCollision();
 
                if (!addr.IsValid()) {
                    // No tried table collisions. Select a new table address
                    // for our feeler.
                    std::tie(addr, addr_last_try) = addrman.Select(true);
                } else if (AlreadyConnectedToAddress(addr)) {
                    // If test-before-evict logic would have us connect to a
                    // peer that we're already connected to, just mark that
                    // address as Good(). We won't be able to initiate the
                    // connection anyway, so this avoids inadvertently evicting
                    // a currently-connected peer.
                    addrman.Good(addr);
                    // Select a new table address for our feeler instead.
                    std::tie(addr, addr_last_try) = addrman.Select(true);
                }
            } else {
                // Not a feeler
                std::tie(addr, addr_last_try) = addrman.Select();
            }
 
            // Require outbound connections, other than feelers and avalanche,
            // to be to distinct network groups
            if (!fFeeler && conn_type != ConnectionType::AVALANCHE_OUTBOUND &&
                setConnected.count(addr.GetGroup(addrman.GetAsmap()))) {
                break;
            }
 
            // if we selected an invalid or local address, restart
            if (!addr.IsValid() || IsLocal(addr)) {
                break;
            }
 
            if (!IsReachable(addr)) {
                continue;
            }
 
            // only consider very recently tried nodes after 30 failed attempts
            if (current_time - addr_last_try < 10min && nTries < 30) {
                continue;
            }
 
            // for non-feelers, require all the services we'll want,
            // for feelers, only require they be a full node (only because most
            // SPV clients don't have a good address DB available)
            if (!fFeeler && !HasAllDesirableServiceFlags(addr.nServices)) {
                continue;
            }
 
            if (fFeeler && !MayHaveUsefulAddressDB(addr.nServices)) {
                continue;
            }
 
            // Do not connect to bad ports, unless 50 invalid addresses have
            // been selected already.
            if (nTries < 50 && (addr.IsIPv4() || addr.IsIPv6()) &&
                IsBadPort(addr.GetPort())) {
                continue;
            }
 
            // For avalanche peers, check they have the avalanche service bit
            // set.
            if (conn_type == ConnectionType::AVALANCHE_OUTBOUND &&
                !(addr.nServices & NODE_AVALANCHE)) {
                // If this peer is not suitable as an avalanche one and we tried
                // over 20 addresses already, see if we can fallback to a non
                // avalanche full outbound.
                if (nTries < 20 ||
                    nOutboundFullRelay >= m_max_outbound_full_relay ||
                    setConnected.count(addr.GetGroup(addrman.GetAsmap()))) {
                    // Fallback is not desirable or possible, try another one
                    continue;
                }
 
                // Fallback is possible, update the connection type accordingly
                conn_type = ConnectionType::OUTBOUND_FULL_RELAY;
            }
 
            addrConnect = addr;
            break;
        }
 
        if (addrConnect.IsValid()) {
            if (fFeeler) {
                // Add small amount of random noise before connection to avoid
                // synchronization.
                if (!interruptNet.sleep_for(
                        rng.rand_uniform_duration<CThreadInterrupt::Clock>(
                            FEELER_SLEEP_WINDOW))) {
                    return;
                }
                LogPrint(BCLog::NET, "Making feeler connection to %s\n",
                         addrConnect.ToStringAddrPort());
            }
 
            // This mock is for testing purpose only. It prevents the thread
            // from attempting the connection which is useful for testing.
            if (mockOpenConnection) {
                mockOpenConnection(addrConnect, conn_type);
            } else {
                OpenNetworkConnection(addrConnect,
                                      int(setConnected.size()) >=
                                          std::min(nMaxConnections - 1, 2),
                                      &grant, nullptr, conn_type);
            }
        }
    }
}
 
std::vector<CAddress> CConnman::GetCurrentBlockRelayOnlyConns() const {
    std::vector<CAddress> ret;
    LOCK(m_nodes_mutex);
    for (const CNode *pnode : m_nodes) {
        if (pnode->IsBlockOnlyConn()) {
            ret.push_back(pnode->addr);
        }
    }
 
    return ret;
}
 
std::vector<AddedNodeInfo> CConnman::GetAddedNodeInfo() const {
    std::vector<AddedNodeInfo> ret;
 
    std::list<std::string> lAddresses(0);
    {
        LOCK(m_added_nodes_mutex);
        ret.reserve(m_added_nodes.size());
        std::copy(m_added_nodes.cbegin(), m_added_nodes.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(m_nodes_mutex);
        for (const CNode *pnode : m_nodes) {
            if (pnode->addr.IsValid()) {
                mapConnected[pnode->addr] = pnode->IsInboundConn();
            }
            std::string addrName{pnode->m_addr_name};
            if (!addrName.empty()) {
                mapConnectedByName[std::move(addrName)] =
                    std::make_pair(pnode->IsInboundConn(),
                                   static_cast<const CService &>(pnode->addr));
            }
        }
    }
 
    for (const std::string &strAddNode : lAddresses) {
        CService service(
            LookupNumeric(strAddNode, Params().GetDefaultPort(strAddNode)));
        AddedNodeInfo addedNode{strAddNode, CService(), false, false};
        if (service.IsValid()) {
            // strAddNode is an IP:port
            auto it = mapConnected.find(service);
            if (it != mapConnected.end()) {
                addedNode.resolvedAddress = service;
                addedNode.fConnected = true;
                addedNode.fInbound = it->second;
            }
        } else {
            // strAddNode is a name
            auto it = mapConnectedByName.find(strAddNode);
            if (it != mapConnectedByName.end()) {
                addedNode.resolvedAddress = it->second.second;
                addedNode.fConnected = true;
                addedNode.fInbound = it->second.first;
            }
        }
        ret.emplace_back(std::move(addedNode));
    }
 
    return ret;
}
 
void CConnman::ThreadOpenAddedConnections() {
    while (true) {
        CSemaphoreGrant grant(*semAddnode);
        std::vector<AddedNodeInfo> vInfo = GetAddedNodeInfo();
        bool tried = false;
        for (const AddedNodeInfo &info : vInfo) {
            if (!info.fConnected) {
                if (!grant.TryAcquire()) {
                    // If we've used up our semaphore and need a new one, let's
                    // not wait here since while we are waiting the
                    // addednodeinfo state might change.
                    break;
                }
                tried = true;
                CAddress addr(CService(), NODE_NONE);
                OpenNetworkConnection(addr, false, &grant,
                                      info.strAddedNode.c_str(),
                                      ConnectionType::MANUAL);
                if (!interruptNet.sleep_for(std::chrono::milliseconds(500))) {
                    return;
                }
            }
        }
        // Retry every 60 seconds if a connection was attempted, otherwise two
        // seconds.
        if (!interruptNet.sleep_for(std::chrono::seconds(tried ? 60 : 2))) {
            return;
        }
    }
}
 
// If successful, this moves the passed grant to the constructed node.
void CConnman::OpenNetworkConnection(const CAddress &addrConnect,
                                     bool fCountFailure,
                                     CSemaphoreGrant *grantOutbound,
                                     const char *pszDest,
                                     ConnectionType conn_type) {
    assert(conn_type != ConnectionType::INBOUND);
 
    //
    // Initiate outbound network connection
    //
    if (interruptNet) {
        return;
    }
    if (!fNetworkActive) {
        return;
    }
    if (!pszDest) {
        bool banned_or_discouraged =
            m_banman && (m_banman->IsDiscouraged(addrConnect) ||
                         m_banman->IsBanned(addrConnect));
        if (IsLocal(addrConnect) || banned_or_discouraged ||
            AlreadyConnectedToAddress(addrConnect)) {
            return;
        }
    } else if (FindNode(std::string(pszDest))) {
        return;
    }
 
    CNode *pnode = ConnectNode(addrConnect, pszDest, fCountFailure, conn_type);
 
    if (!pnode) {
        return;
    }
    if (grantOutbound) {
        grantOutbound->MoveTo(pnode->grantOutbound);
    }
 
    for (auto interface : m_msgproc) {
        interface->InitializeNode(*config, *pnode, nLocalServices);
    }
 
    {
        LOCK(m_nodes_mutex);
        m_nodes.push_back(pnode);
    }
}
 
Mutex NetEventsInterface::g_msgproc_mutex;
 
void CConnman::ThreadMessageHandler() {
    LOCK(NetEventsInterface::g_msgproc_mutex);
 
    while (!flagInterruptMsgProc) {
        bool fMoreWork = false;
 
        {
            // Randomize the order in which we process messages from/to our
            // peers. This prevents attacks in which an attacker exploits having
            // multiple consecutive connections in the vNodes list.
            const NodesSnapshot snap{*this, /*shuffle=*/true};
 
            for (CNode *pnode : snap.Nodes()) {
                if (pnode->fDisconnect) {
                    continue;
                }
 
                bool fMoreNodeWork = false;
                // Receive messages
                for (auto interface : m_msgproc) {
                    fMoreNodeWork |= interface->ProcessMessages(
                        *config, pnode, flagInterruptMsgProc);
                }
                fMoreWork |= (fMoreNodeWork && !pnode->fPauseSend);
                if (flagInterruptMsgProc) {
                    return;
                }
 
                // Send messages
                for (auto interface : m_msgproc) {
                    interface->SendMessages(*config, pnode);
                }
 
                if (flagInterruptMsgProc) {
                    return;
                }
            }
        }
 
        WAIT_LOCK(mutexMsgProc, lock);
        if (!fMoreWork) {
            condMsgProc.wait_until(lock,
                                   std::chrono::steady_clock::now() +
                                       std::chrono::milliseconds(100),
                                   [this]() EXCLUSIVE_LOCKS_REQUIRED(
                                       mutexMsgProc) { return fMsgProcWake; });
        }
        fMsgProcWake = false;
    }
}
 
void CConnman::ThreadI2PAcceptIncoming() {
    static constexpr auto err_wait_begin = 1s;
    static constexpr auto err_wait_cap = 5min;
    auto err_wait = err_wait_begin;
 
    bool advertising_listen_addr = false;
    i2p::Connection conn;
 
    while (!interruptNet) {
        if (!m_i2p_sam_session->Listen(conn)) {
            if (advertising_listen_addr && conn.me.IsValid()) {
                RemoveLocal(conn.me);
                advertising_listen_addr = false;
            }
 
            interruptNet.sleep_for(err_wait);
            if (err_wait < err_wait_cap) {
                err_wait *= 2;
            }
 
            continue;
        }
 
        if (!advertising_listen_addr) {
            AddLocal(conn.me, LOCAL_MANUAL);
            advertising_listen_addr = true;
        }
 
        if (!m_i2p_sam_session->Accept(conn)) {
            continue;
        }
 
        CreateNodeFromAcceptedSocket(
            std::move(conn.sock), NetPermissionFlags::None,
            CAddress{conn.me, NODE_NONE}, CAddress{conn.peer, NODE_NONE});
    }
}
 
bool CConnman::BindListenPort(const CService &addrBind, bilingual_str &strError,
                              NetPermissionFlags permissions) {
    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(Untranslated("Bind address family for %s not supported"),
                      addrBind.ToStringAddrPort());
        LogPrintLevel(BCLog::NET, BCLog::Level::Error, "%s\n",
                      strError.original);
        return false;
    }
 
    std::unique_ptr<Sock> sock = CreateSock(addrBind);
    if (!sock) {
        strError =
            strprintf(Untranslated("Couldn't open socket for incoming "
                                   "connections (socket returned error %s)"),
                      NetworkErrorString(WSAGetLastError()));
        LogPrintLevel(BCLog::NET, BCLog::Level::Error, "%s\n",
                      strError.original);
        return false;
    }
 
    // Allow binding if the port is still in TIME_WAIT state after
    // the program was closed and restarted.
    setsockopt(sock->Get(), SOL_SOCKET, SO_REUSEADDR, (sockopt_arg_type)&nOne,
               sizeof(int));
 
    // 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
        setsockopt(sock->Get(), IPPROTO_IPV6, IPV6_V6ONLY,
                   (sockopt_arg_type)&nOne, sizeof(int));
#endif
#ifdef WIN32
        int nProtLevel = PROTECTION_LEVEL_UNRESTRICTED;
        setsockopt(sock->Get(), IPPROTO_IPV6, IPV6_PROTECTION_LEVEL,
                   (sockopt_arg_type)&nProtLevel, sizeof(int));
#endif
    }
 
    if (::bind(sock->Get(), (struct sockaddr *)&sockaddr, len) ==
        SOCKET_ERROR) {
        int nErr = WSAGetLastError();
        if (nErr == WSAEADDRINUSE) {
            strError = strprintf(_("Unable to bind to %s on this computer. %s "
                                   "is probably already running."),
                                 addrBind.ToStringAddrPort(), PACKAGE_NAME);
        } else {
            strError = strprintf(_("Unable to bind to %s on this computer "
                                   "(bind returned error %s)"),
                                 addrBind.ToStringAddrPort(),
                                 NetworkErrorString(nErr));
        }
 
        LogPrintLevel(BCLog::NET, BCLog::Level::Error, "%s\n",
                      strError.original);
        return false;
    }
    LogPrintf("Bound to %s\n", addrBind.ToStringAddrPort());
 
    // Listen for incoming connections
    if (listen(sock->Get(), SOMAXCONN) == SOCKET_ERROR) {
        strError = strprintf(_("Listening for incoming connections "
                               "failed (listen returned error %s)"),
                             NetworkErrorString(WSAGetLastError()));
        LogPrintLevel(BCLog::NET, BCLog::Level::Error, "%s\n",
                      strError.original);
        return false;
    }
 
    vhListenSocket.emplace_back(std::move(sock), permissions);
    return true;
}
 
void Discover() {
    if (!fDiscover) {
        return;
    }
 
#ifdef WIN32
    // Get local host IP
    char pszHostName[256] = "";
    if (gethostname(pszHostName, sizeof(pszHostName)) != SOCKET_ERROR) {
        const std::vector<CNetAddr> addresses{LookupHost(pszHostName, 0, true)};
        for (const CNetAddr &addr : addresses) {
            if (AddLocal(addr, LOCAL_IF)) {
                LogPrintf("%s: %s - %s\n", __func__, pszHostName,
                          addr.ToStringAddr());
            }
        }
    }
#elif (HAVE_DECL_GETIFADDRS && HAVE_DECL_FREEIFADDRS)
    // Get local host ip
    struct ifaddrs *myaddrs;
    if (getifaddrs(&myaddrs) == 0) {
        for (struct ifaddrs *ifa = myaddrs; ifa != nullptr;
             ifa = ifa->ifa_next) {
            if (ifa->ifa_addr == nullptr || (ifa->ifa_flags & IFF_UP) == 0 ||
                strcmp(ifa->ifa_name, "lo") == 0 ||
                strcmp(ifa->ifa_name, "lo0") == 0) {
                continue;
            }
            if (ifa->ifa_addr->sa_family == AF_INET) {
                struct sockaddr_in *s4 =
                    reinterpret_cast<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.ToStringAddr());
                }
            } else if (ifa->ifa_addr->sa_family == AF_INET6) {
                struct sockaddr_in6 *s6 =
                    reinterpret_cast<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.ToStringAddr());
                }
            }
        }
        freeifaddrs(myaddrs);
    }
#endif
}
 
void CConnman::SetNetworkActive(bool active) {
    LogPrintf("%s: %s\n", __func__, active);
 
    if (fNetworkActive == active) {
        return;
    }
 
    fNetworkActive = active;
 
    if (m_client_interface) {
        m_client_interface->NotifyNetworkActiveChanged(fNetworkActive);
    }
}
 
CConnman::CConnman(const Config &configIn, uint64_t nSeed0In, uint64_t nSeed1In,
                   AddrMan &addrmanIn, bool network_active)
    : config(&configIn), addrman(addrmanIn), nSeed0(nSeed0In),
      nSeed1(nSeed1In) {
    SetTryNewOutboundPeer(false);
 
    Options connOptions;
    Init(connOptions);
    SetNetworkActive(network_active);
}
 
NodeId CConnman::GetNewNodeId() {
    return nLastNodeId.fetch_add(1);
}
 
bool CConnman::Bind(const CService &addr, unsigned int flags,
                    NetPermissionFlags permissions) {
    if (!(flags & BF_EXPLICIT) && !IsReachable(addr)) {
        return false;
    }
    bilingual_str strError;
    if (!BindListenPort(addr, strError, permissions)) {
        if ((flags & BF_REPORT_ERROR) && m_client_interface) {
            m_client_interface->ThreadSafeMessageBox(
                strError, "", CClientUIInterface::MSG_ERROR);
        }
        return false;
    }
 
    if (addr.IsRoutable() && fDiscover && !(flags & BF_DONT_ADVERTISE) &&
        !NetPermissions::HasFlag(permissions, NetPermissionFlags::NoBan)) {
        AddLocal(addr, LOCAL_BIND);
    }
 
    return true;
}
 
bool CConnman::InitBinds(const Options &options) {
    for (const auto &addrBind : options.vBinds) {
        if (!Bind(addrBind, BF_EXPLICIT | BF_REPORT_ERROR,
                  NetPermissionFlags::None)) {
            return false;
        }
    }
    for (const auto &addrBind : options.vWhiteBinds) {
        if (!Bind(addrBind.m_service, BF_EXPLICIT | BF_REPORT_ERROR,
                  addrBind.m_flags)) {
            return false;
        }
    }
    for (const auto &addr_bind : options.onion_binds) {
        if (!Bind(addr_bind, BF_EXPLICIT | BF_REPORT_ERROR | BF_DONT_ADVERTISE,
                  NetPermissionFlags::None)) {
            return false;
        }
    }
    if (options.bind_on_any) {
        // Don't consider errors to bind on IPv6 "::" fatal because the host OS
        // may not have IPv6 support and the user did not explicitly ask us to
        // bind on that.
        const CService ipv6_any{in6_addr(IN6ADDR_ANY_INIT),
                                GetListenPort()}; // ::
        Bind(ipv6_any, BF_NONE, NetPermissionFlags::None);
 
        struct in_addr inaddr_any;
        inaddr_any.s_addr = htonl(INADDR_ANY);
        const CService ipv4_any{inaddr_any, GetListenPort()}; // 0.0.0.0
        if (!Bind(ipv4_any, BF_REPORT_ERROR, NetPermissionFlags::None)) {
            return false;
        }
    }
    return true;
}
 
bool CConnman::Start(CScheduler &scheduler, const Options &connOptions) {
    Init(connOptions);
 
    if (fListen && !InitBinds(connOptions)) {
        if (m_client_interface) {
            m_client_interface->ThreadSafeMessageBox(
                _("Failed to listen on any port. Use -listen=0 if you want "
                  "this."),
                "", CClientUIInterface::MSG_ERROR);
        }
        return false;
    }
 
    proxyType i2p_sam;
    if (GetProxy(NET_I2P, i2p_sam)) {
        m_i2p_sam_session = std::make_unique<i2p::sam::Session>(
            gArgs.GetDataDirNet() / "i2p_private_key", i2p_sam.proxy,
            &interruptNet);
    }
 
    for (const auto &strDest : connOptions.vSeedNodes) {
        AddAddrFetch(strDest);
    }
 
    if (m_use_addrman_outgoing) {
        // Load addresses from anchors.dat
        m_anchors =
            ReadAnchors(config->GetChainParams(),
                        gArgs.GetDataDirNet() / ANCHORS_DATABASE_FILENAME);
        if (m_anchors.size() > MAX_BLOCK_RELAY_ONLY_ANCHORS) {
            m_anchors.resize(MAX_BLOCK_RELAY_ONLY_ANCHORS);
        }
        LogPrintf(
            "%i block-relay-only anchors will be tried for connections.\n",
            m_anchors.size());
    }
 
    if (m_client_interface) {
        m_client_interface->InitMessage(
            _("Starting network threads...").translated);
    }
 
    fAddressesInitialized = true;
 
    if (semOutbound == nullptr) {
        // initialize semaphore
        semOutbound = std::make_unique<CSemaphore>(
            std::min(m_max_outbound, nMaxConnections));
    }
    if (semAddnode == nullptr) {
        // initialize semaphore
        semAddnode = std::make_unique<CSemaphore>(nMaxAddnode);
    }
 
    //
    // Start threads
    //
    assert(m_msgproc.size() > 0);
    InterruptSocks5(false);
    interruptNet.reset();
    flagInterruptMsgProc = false;
 
    {
        LOCK(mutexMsgProc);
        fMsgProcWake = false;
    }
 
    // Send and receive from sockets, accept connections
    threadSocketHandler = std::thread(&util::TraceThread, "net",
                                      [this] { ThreadSocketHandler(); });
 
    if (!gArgs.GetBoolArg("-dnsseed", DEFAULT_DNSSEED)) {
        LogPrintf("DNS seeding disabled\n");
    } else {
        threadDNSAddressSeed = std::thread(&util::TraceThread, "dnsseed",
                                           [this] { ThreadDNSAddressSeed(); });
    }
 
    // Initiate manual connections
    threadOpenAddedConnections = std::thread(
        &util::TraceThread, "addcon", [this] { ThreadOpenAddedConnections(); });
 
    if (connOptions.m_use_addrman_outgoing &&
        !connOptions.m_specified_outgoing.empty()) {
        if (m_client_interface) {
            m_client_interface->ThreadSafeMessageBox(
                _("Cannot provide specific connections and have addrman find "
                  "outgoing connections at the same."),
                "", CClientUIInterface::MSG_ERROR);
        }
        return false;
    }
    if (connOptions.m_use_addrman_outgoing ||
        !connOptions.m_specified_outgoing.empty()) {
        threadOpenConnections =
            std::thread(&util::TraceThread, "opencon",
                        [this, connect = connOptions.m_specified_outgoing] {
                            ThreadOpenConnections(connect, nullptr);
                        });
    }
 
    // Process messages
    threadMessageHandler = std::thread(&util::TraceThread, "msghand",
                                       [this] { ThreadMessageHandler(); });
 
    if (connOptions.m_i2p_accept_incoming &&
        m_i2p_sam_session.get() != nullptr) {
        threadI2PAcceptIncoming =
            std::thread(&util::TraceThread, "i2paccept",
                        [this] { ThreadI2PAcceptIncoming(); });
    }
 
    // Dump network addresses
    scheduler.scheduleEvery(
        [this]() {
            this->DumpAddresses();
            return true;
        },
        DUMP_PEERS_INTERVAL);
 
    return true;
}
 
class CNetCleanup {
public:
    CNetCleanup() = default;
 
    ~CNetCleanup() {
#ifdef WIN32
        // Shutdown Windows Sockets
        WSACleanup();
#endif
    }
};
static CNetCleanup instance_of_cnetcleanup;
 
void CConnman::Interrupt() {
    {
        LOCK(mutexMsgProc);
        flagInterruptMsgProc = true;
    }
    condMsgProc.notify_all();
 
    interruptNet();
    InterruptSocks5(true);
 
    if (semOutbound) {
        for (int i = 0; i < m_max_outbound; i++) {
            semOutbound->post();
        }
    }
 
    if (semAddnode) {
        for (int i = 0; i < nMaxAddnode; i++) {
            semAddnode->post();
        }
    }
}
 
void CConnman::StopThreads() {
    if (threadI2PAcceptIncoming.joinable()) {
        threadI2PAcceptIncoming.join();
    }
    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();
    }
}
 
void CConnman::StopNodes() {
    if (fAddressesInitialized) {
        DumpAddresses();
        fAddressesInitialized = false;
 
        if (m_use_addrman_outgoing) {
            // Anchor connections are only dumped during clean shutdown.
            std::vector<CAddress> anchors_to_dump =
                GetCurrentBlockRelayOnlyConns();
            if (anchors_to_dump.size() > MAX_BLOCK_RELAY_ONLY_ANCHORS) {
                anchors_to_dump.resize(MAX_BLOCK_RELAY_ONLY_ANCHORS);
            }
            DumpAnchors(config->GetChainParams(),
                        gArgs.GetDataDirNet() / ANCHORS_DATABASE_FILENAME,
                        anchors_to_dump);
        }
    }
 
    // Delete peer connections.
    std::vector<CNode *> nodes;
    WITH_LOCK(m_nodes_mutex, nodes.swap(m_nodes));
    for (CNode *pnode : nodes) {
        pnode->CloseSocketDisconnect();
        DeleteNode(pnode);
    }
 
    for (CNode *pnode : m_nodes_disconnected) {
        DeleteNode(pnode);
    }
    m_nodes_disconnected.clear();
    vhListenSocket.clear();
    semOutbound.reset();
    semAddnode.reset();
}
 
void CConnman::DeleteNode(CNode *pnode) {
    assert(pnode);
    for (auto interface : m_msgproc) {
        interface->FinalizeNode(*config, *pnode);
    }
    delete pnode;
}
 
CConnman::~CConnman() {
    Interrupt();
    Stop();
}
 
std::vector<CAddress>
CConnman::GetAddresses(size_t max_addresses, size_t max_pct,
                       std::optional<Network> network) const {
    std::vector<CAddress> addresses =
        addrman.GetAddr(max_addresses, max_pct, network);
    if (m_banman) {
        addresses.erase(std::remove_if(addresses.begin(), addresses.end(),
                                       [this](const CAddress &addr) {
                                           return m_banman->IsDiscouraged(
                                                      addr) ||
                                                  m_banman->IsBanned(addr);
                                       }),
                        addresses.end());
    }
    return addresses;
}
 
std::vector<CAddress>
CConnman::GetAddresses(CNode &requestor, size_t max_addresses, size_t max_pct) {
    auto local_socket_bytes = requestor.addrBind.GetAddrBytes();
    uint64_t cache_id = GetDeterministicRandomizer(RANDOMIZER_ID_ADDRCACHE)
                            .Write(requestor.addr.GetNetwork())
                            .Write(local_socket_bytes)
                            .Finalize();
    const auto current_time = GetTime<std::chrono::microseconds>();
    auto r = m_addr_response_caches.emplace(cache_id, CachedAddrResponse{});
    CachedAddrResponse &cache_entry = r.first->second;
    // New CachedAddrResponse have expiration 0.
    if (cache_entry.m_cache_entry_expiration < current_time) {
        cache_entry.m_addrs_response_cache =
            GetAddresses(max_addresses, max_pct, /* network */ std::nullopt);
        // Choosing a proper cache lifetime is a trade-off between the privacy
        // leak minimization and the usefulness of ADDR responses to honest
        // users.
        //
        // Longer cache lifetime makes it more difficult for an attacker to
        // scrape enough AddrMan data to maliciously infer something useful. By
        // the time an attacker scraped enough AddrMan records, most of the
        // records should be old enough to not leak topology info by e.g.
        // analyzing real-time changes in timestamps.
        //
        // It takes only several hundred requests to scrape everything from an
        // AddrMan containing 100,000 nodes, so ~24 hours of cache lifetime
        // indeed makes the data less inferable by the time most of it could be
        // scraped (considering that timestamps are updated via ADDR
        // self-announcements and when nodes communicate). We also should be
        // robust to those attacks which may not require scraping *full*
        // victim's AddrMan (because even several timestamps of the same handful
        // of nodes may leak privacy).
        //
        // On the other hand, longer cache lifetime makes ADDR responses
        // outdated and less useful for an honest requestor, e.g. if most nodes
        // in the ADDR response are no longer active.
        //
        // However, the churn in the network is known to be rather low. Since we
        // consider nodes to be "terrible" (see IsTerrible()) if the timestamps
        // are older than 30 days, max. 24 hours of "penalty" due to cache
        // shouldn't make any meaningful difference in terms of the freshness of
        // the response.
        cache_entry.m_cache_entry_expiration =
            current_time + 21h +
            FastRandomContext().randrange<std::chrono::microseconds>(6h);
    }
    return cache_entry.m_addrs_response_cache;
}
 
bool CConnman::AddNode(const std::string &strNode) {
    LOCK(m_added_nodes_mutex);
    for (const std::string &it : m_added_nodes) {
        if (strNode == it) {
            return false;
        }
    }
 
    m_added_nodes.push_back(strNode);
    return true;
}
 
bool CConnman::RemoveAddedNode(const std::string &strNode) {
    LOCK(m_added_nodes_mutex);
    for (std::vector<std::string>::iterator it = m_added_nodes.begin();
         it != m_added_nodes.end(); ++it) {
        if (strNode == *it) {
            m_added_nodes.erase(it);
            return true;
        }
    }
    return false;
}
 
size_t CConnman::GetNodeCount(ConnectionDirection flags) const {
    LOCK(m_nodes_mutex);
    // Shortcut if we want total
    if (flags == ConnectionDirection::Both) {
        return m_nodes.size();
    }
 
    int nNum = 0;
    for (const auto &pnode : m_nodes) {
        if (flags & (pnode->IsInboundConn() ? ConnectionDirection::In
                                            : ConnectionDirection::Out)) {
            nNum++;
        }
    }
 
    return nNum;
}
 
void CConnman::GetNodeStats(std::vector<CNodeStats> &vstats) const {
    vstats.clear();
    LOCK(m_nodes_mutex);
    vstats.reserve(m_nodes.size());
    for (CNode *pnode : m_nodes) {
        vstats.emplace_back();
        pnode->copyStats(vstats.back());
        vstats.back().m_mapped_as = pnode->addr.GetMappedAS(addrman.GetAsmap());
    }
}
 
bool CConnman::GetNodeStats(NodeId id, CNodeStats &stats) const {
    LOCK(m_nodes_mutex);
 
    for (auto &&pnode : m_nodes) {
        if (pnode->GetId() == id) {
            pnode->copyStats(stats);
            stats.m_mapped_as = pnode->addr.GetMappedAS(addrman.GetAsmap());
            return true;
        }
    }
 
    return false;
}
 
bool CConnman::DisconnectNode(const std::string &strNode) {
    LOCK(m_nodes_mutex);
    if (CNode *pnode = FindNode(strNode)) {
        LogPrint(BCLog::NET,
                 "disconnect by address%s matched peer=%d; disconnecting\n",
                 (fLogIPs ? strprintf("=%s", strNode) : ""), pnode->GetId());
        pnode->fDisconnect = true;
        return true;
    }
    return false;
}
 
bool CConnman::DisconnectNode(const CSubNet &subnet) {
    bool disconnected = false;
    LOCK(m_nodes_mutex);
    for (CNode *pnode : m_nodes) {
        if (subnet.Match(pnode->addr)) {
            LogPrint(BCLog::NET,
                     "disconnect by subnet%s matched peer=%d; disconnecting\n",
                     (fLogIPs ? strprintf("=%s", subnet.ToString()) : ""),
                     pnode->GetId());
            pnode->fDisconnect = true;
            disconnected = true;
        }
    }
    return disconnected;
}
 
bool CConnman::DisconnectNode(const CNetAddr &addr) {
    return DisconnectNode(CSubNet(addr));
}
 
bool CConnman::DisconnectNode(NodeId id) {
    LOCK(m_nodes_mutex);
    for (CNode *pnode : m_nodes) {
        if (id == pnode->GetId()) {
            LogPrint(BCLog::NET, "disconnect by id peer=%d; disconnecting\n",
                     pnode->GetId());
            pnode->fDisconnect = true;
            return true;
        }
    }
    return false;
}
 
void CConnman::RecordBytesRecv(uint64_t bytes) {
    nTotalBytesRecv += bytes;
}
 
void CConnman::RecordBytesSent(uint64_t bytes) {
    LOCK(cs_totalBytesSent);
    nTotalBytesSent += bytes;
 
    const auto now = GetTime<std::chrono::seconds>();
    if (nMaxOutboundCycleStartTime + MAX_UPLOAD_TIMEFRAME < now) {
        // timeframe expired, reset cycle
        nMaxOutboundCycleStartTime = now;
        nMaxOutboundTotalBytesSentInCycle = 0;
    }
 
    // TODO, exclude peers with download permission
    nMaxOutboundTotalBytesSentInCycle += bytes;
}
 
uint64_t CConnman::GetMaxOutboundTarget() const {
    LOCK(cs_totalBytesSent);
    return nMaxOutboundLimit;
}
 
std::chrono::seconds CConnman::GetMaxOutboundTimeframe() const {
    return MAX_UPLOAD_TIMEFRAME;
}
 
std::chrono::seconds CConnman::GetMaxOutboundTimeLeftInCycle() const {
    LOCK(cs_totalBytesSent);
    if (nMaxOutboundLimit == 0) {
        return 0s;
    }
 
    if (nMaxOutboundCycleStartTime.count() == 0) {
        return MAX_UPLOAD_TIMEFRAME;
    }
 
    const std::chrono::seconds cycleEndTime =
        nMaxOutboundCycleStartTime + MAX_UPLOAD_TIMEFRAME;
    const auto now = GetTime<std::chrono::seconds>();
    return (cycleEndTime < now) ? 0s : cycleEndTime - now;
}
 
bool CConnman::OutboundTargetReached(bool historicalBlockServingLimit) const {
    LOCK(cs_totalBytesSent);
    if (nMaxOutboundLimit == 0) {
        return false;
    }
 
    if (historicalBlockServingLimit) {
        // keep a large enough buffer to at least relay each block once.
        const std::chrono::seconds timeLeftInCycle =
            GetMaxOutboundTimeLeftInCycle();
        const uint64_t buffer =
            timeLeftInCycle / std::chrono::minutes{10} * ONE_MEGABYTE;
        if (buffer >= nMaxOutboundLimit ||
            nMaxOutboundTotalBytesSentInCycle >= nMaxOutboundLimit - buffer) {
            return true;
        }
    } else if (nMaxOutboundTotalBytesSentInCycle >= nMaxOutboundLimit) {
        return true;
    }
 
    return false;
}
 
uint64_t CConnman::GetOutboundTargetBytesLeft() const {
    LOCK(cs_totalBytesSent);
    if (nMaxOutboundLimit == 0) {
        return 0;
    }
 
    return (nMaxOutboundTotalBytesSentInCycle >= nMaxOutboundLimit)
               ? 0
               : nMaxOutboundLimit - nMaxOutboundTotalBytesSentInCycle;
}
 
uint64_t CConnman::GetTotalBytesRecv() const {
    return nTotalBytesRecv;
}
 
uint64_t CConnman::GetTotalBytesSent() const {
    LOCK(cs_totalBytesSent);
    return nTotalBytesSent;
}
 
ServiceFlags CConnman::GetLocalServices() const {
    return nLocalServices;
}
 
void CNode::invsPolled(uint32_t count) {
    invCounters += count;
}
 
void CNode::invsVoted(uint32_t count) {
    invCounters += uint64_t(count) << 32;
}
 
void CNode::updateAvailabilityScore(double decayFactor) {
    if (!m_avalanche_enabled) {
        return;
    }
 
    uint64_t windowInvCounters = invCounters.exchange(0);
    double previousScore = availabilityScore;
 
    int64_t polls = windowInvCounters & std::numeric_limits<uint32_t>::max();
    int64_t votes = windowInvCounters >> 32;
 
    availabilityScore =
        decayFactor * (2 * votes - polls) + (1. - decayFactor) * previousScore;
}
 
double CNode::getAvailabilityScore() const {
    // The score is set atomically so there is no need to lock the statistics
    // when reading.
    return availabilityScore;
}
 
CNode::CNode(NodeId idIn, std::shared_ptr<Sock> sock, const CAddress &addrIn,
             uint64_t nKeyedNetGroupIn, uint64_t nLocalHostNonceIn,
             uint64_t nLocalExtraEntropyIn, const CAddress &addrBindIn,
             const std::string &addrNameIn, ConnectionType conn_type_in,
             bool inbound_onion, CNodeOptions &&node_opts)
    : m_deserializer{std::make_unique<V1TransportDeserializer>(
          V1TransportDeserializer(GetConfig().GetChainParams().NetMagic()))},
      m_serializer{
          std::make_unique<V1TransportSerializer>(V1TransportSerializer())},
      m_permission_flags{node_opts.permission_flags}, m_sock{sock},
      m_connected(GetTime<std::chrono::seconds>()), addr(addrIn),
      addrBind(addrBindIn),
      m_addr_name{addrNameIn.empty() ? addr.ToStringAddrPort() : addrNameIn},
      m_inbound_onion(inbound_onion), m_prefer_evict{node_opts.prefer_evict},
      nKeyedNetGroup(nKeyedNetGroupIn), m_conn_type(conn_type_in), id(idIn),
      nLocalHostNonce(nLocalHostNonceIn),
      nLocalExtraEntropy(nLocalExtraEntropyIn),
      m_recv_flood_size{node_opts.recv_flood_size} {
    if (inbound_onion) {
        assert(conn_type_in == ConnectionType::INBOUND);
    }
 
    for (const std::string &msg : getAllNetMessageTypes()) {
        mapRecvBytesPerMsgType[msg] = 0;
    }
    mapRecvBytesPerMsgType[NET_MESSAGE_TYPE_OTHER] = 0;
 
    if (fLogIPs) {
        LogPrint(BCLog::NET, "Added connection to %s peer=%d\n", m_addr_name,
                 id);
    } else {
        LogPrint(BCLog::NET, "Added connection peer=%d\n", id);
    }
}
 
void CNode::MarkReceivedMsgsForProcessing() {
    AssertLockNotHeld(m_msg_process_queue_mutex);
 
    size_t nSizeAdded = 0;
    for (const auto &msg : vRecvMsg) {
        // vRecvMsg contains only completed CNetMessage
        // the single possible partially deserialized message are held by
        // TransportDeserializer
        nSizeAdded += msg.m_raw_message_size;
    }
 
    LOCK(m_msg_process_queue_mutex);
    m_msg_process_queue.splice(m_msg_process_queue.end(), vRecvMsg);
    m_msg_process_queue_size += nSizeAdded;
    fPauseRecv = m_msg_process_queue_size > m_recv_flood_size;
}
 
std::optional<std::pair<CNetMessage, bool>> CNode::PollMessage() {
    LOCK(m_msg_process_queue_mutex);
    if (m_msg_process_queue.empty()) {
        return std::nullopt;
    }
 
    std::list<CNetMessage> msgs;
    // Just take one message
    msgs.splice(msgs.begin(), m_msg_process_queue, m_msg_process_queue.begin());
    m_msg_process_queue_size -= msgs.front().m_raw_message_size;
    fPauseRecv = m_msg_process_queue_size > m_recv_flood_size;
 
    return std::make_pair(std::move(msgs.front()),
                          !m_msg_process_queue.empty());
}
 
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();
    LogPrint(BCLog::NETDEBUG, "sending %s (%d bytes) peer=%d\n", msg.m_type,
             nMessageSize, pnode->GetId());
    if (gArgs.GetBoolArg("-capturemessages", false)) {
        CaptureMessage(pnode->addr, msg.m_type, msg.data,
                       /*is_incoming=*/false);
    }
 
    TRACE6(net, outbound_message, pnode->GetId(), pnode->m_addr_name.c_str(),
           pnode->ConnectionTypeAsString().c_str(), msg.m_type.c_str(),
           msg.data.size(), msg.data.data());
 
    // make sure we use the appropriate network transport format
    std::vector<uint8_t> serializedHeader;
    pnode->m_serializer->prepareForTransport(*config, msg, serializedHeader);
    size_t nTotalSize = nMessageSize + serializedHeader.size();
 
    size_t nBytesSent = 0;
    {
        LOCK(pnode->cs_vSend);
        bool optimisticSend(pnode->vSendMsg.empty());
 
        // log total amount of bytes per message type
        pnode->AccountForSentBytes(msg.m_type, 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"
        bool data_left;
        if (optimisticSend) {
            std::tie(nBytesSent, data_left) = SocketSendData(*pnode);
        }
    }
    if (nBytesSent) {
        RecordBytesSent(nBytesSent);
    }
}
 
bool CConnman::ForNode(NodeId id, std::function<bool(CNode *pnode)> func) {
    CNode *found = nullptr;
    LOCK(m_nodes_mutex);
    for (auto &&pnode : m_nodes) {
        if (pnode->GetId() == id) {
            found = pnode;
            break;
        }
    }
    return found != nullptr && NodeFullyConnected(found) && func(found);
}
 
CSipHasher CConnman::GetDeterministicRandomizer(uint64_t id) const {
    return CSipHasher(nSeed0, nSeed1).Write(id);
}
 
uint64_t CConnman::CalculateKeyedNetGroup(const CAddress &ad) const {
    std::vector<uint8_t> vchNetGroup(ad.GetGroup(addrman.GetAsmap()));
 
    return GetDeterministicRandomizer(RANDOMIZER_ID_NETGROUP)
        .Write(vchNetGroup)
        .Finalize();
}
 
std::string getSubVersionEB(uint64_t MaxBlockSize) {
    // Prepare EB string we are going to add to SubVer:
    // 1) translate from byte to MB and convert to string
    // 2) limit the EB string to the first decimal digit (floored)
    std::stringstream ebMBs;
    ebMBs << (MaxBlockSize / (ONE_MEGABYTE / 10));
    std::string eb = ebMBs.str();
    eb.insert(eb.size() - 1, ".", 1);
    if (eb.substr(0, 1) == ".") {
        eb = "0" + eb;
    }
    return eb;
}
 
std::string userAgent(const Config &config) {
    // format excessive blocksize value
    std::string eb = getSubVersionEB(config.GetMaxBlockSize());
    std::vector<std::string> uacomments;
    uacomments.push_back("EB" + eb);
 
    // Comments are checked for char compliance at startup, it is safe to add
    // them to the user agent string
    for (const std::string &cmt : gArgs.GetArgs("-uacomment")) {
        uacomments.push_back(cmt);
    }
 
    const std::string client_name = gArgs.GetArg("-uaclientname", CLIENT_NAME);
    const std::string client_version =
        gArgs.GetArg("-uaclientversion", FormatVersion(CLIENT_VERSION));
 
    // Size compliance is checked at startup, it is safe to not check it again
    return FormatUserAgent(client_name, client_version, uacomments);
}
 
void CaptureMessageToFile(const CAddress &addr, const std::string &msg_type,
                          Span<const uint8_t> data, bool is_incoming) {
    // Note: This function captures the message at the time of processing,
    // not at socket receive/send time.
    // This ensures that the messages are always in order from an application
    // layer (processing) perspective.
    auto now = GetTime<std::chrono::microseconds>();
 
    // Windows folder names can not include a colon
    std::string clean_addr = addr.ToStringAddrPort();
    std::replace(clean_addr.begin(), clean_addr.end(), ':', '_');
 
    fs::path base_path = gArgs.GetDataDirNet() / "message_capture" / clean_addr;
    fs::create_directories(base_path);
 
    fs::path path =
        base_path / (is_incoming ? "msgs_recv.dat" : "msgs_sent.dat");
    AutoFile f{fsbridge::fopen(path, "ab")};
 
    ser_writedata64(f, now.count());
    f << Span{msg_type};
    for (auto i = msg_type.length(); i < CMessageHeader::MESSAGE_TYPE_SIZE;
         ++i) {
        f << uint8_t{'\0'};
    }
    uint32_t size = data.size();
    ser_writedata32(f, size);
    f << data;
}
 
std::function<void(const CAddress &addr, const std::string &msg_type,
                   Span<const uint8_t> data, bool is_incoming)>
    CaptureMessage = CaptureMessageToFile;