netbase.cpp

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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2015 The Bitcoin developers
// Distributed under the MIT/X11 software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
#ifdef HAVE_CONFIG_H
#include "config/prcycoin-config.h"
#endif
 
#include "netbase.h"
 
#include "hash.h"
#include "sync.h"
#include "uint256.h"
#include "random.h"
#include "util.h"
#include "utilstrencodings.h"
 
#include <atomic>
 
#ifdef HAVE_GETADDRINFO_A
#include <netdb.h>
#endif
 
#ifndef WIN32
#if HAVE_INET_PTON
#include <arpa/inet.h>
#endif
#include <fcntl.h>
#endif
 
#include <boost/algorithm/string/case_conv.hpp> // for to_lower()
#include <boost/algorithm/string/predicate.hpp> // for startswith() and endswith()
#include <boost/thread.hpp>
 
#if !defined(HAVE_MSG_NOSIGNAL) && !defined(MSG_NOSIGNAL)
#define MSG_NOSIGNAL 0
#endif
 
 
// Settings
static proxyType proxyInfo[NET_MAX];
static proxyType nameProxy;
static RecursiveMutex cs_proxyInfos;
int nConnectTimeout = DEFAULT_CONNECT_TIMEOUT;
bool fNameLookup = false;
 
// Need ample time for negotiation for very slow proxies such as Tor (milliseconds)
static const int SOCKS5_RECV_TIMEOUT = 20 * 1000;
 
enum Network ParseNetwork(std::string net)
{
    boost::to_lower(net);
    if (net == "ipv4") return NET_IPV4;
    if (net == "ipv6") return NET_IPV6;
    if (net == "tor" || net == "onion") return NET_TOR;
    return NET_UNROUTABLE;
}
 
std::string GetNetworkName(enum Network net)
{
    switch (net) {
    case NET_IPV4:
        return "ipv4";
    case NET_IPV6:
        return "ipv6";
    case NET_TOR:
        return "onion";
    default:
        return "";
    }
}
 
void SplitHostPort(std::string in, int& portOut, std::string& hostOut)
{
    size_t colon = in.find_last_of(':');
    // if a : is found, and it either follows a [...], or no other : is in the string, treat it as port separator
    bool fHaveColon = colon != in.npos;
    bool fBracketed = fHaveColon && (in[0] == '[' && in[colon - 1] == ']'); // if there is a colon, and in[0]=='[', colon is not 0, so in[colon-1] is safe
    bool fMultiColon = fHaveColon && (in.find_last_of(':', colon - 1) != in.npos);
    if (fHaveColon && (colon == 0 || fBracketed || !fMultiColon)) {
        int32_t n;
        if (ParseInt32(in.substr(colon + 1), &n) && n > 0 && n < 0x10000) {
            in = in.substr(0, colon);
            portOut = n;
        }
    }
    if (in.size() > 0 && in[0] == '[' && in[in.size() - 1] == ']')
        hostOut = in.substr(1, in.size() - 2);
    else
        hostOut = in;
}
 
bool static LookupIntern(const char* pszName, std::vector<CNetAddr>& vIP, unsigned int nMaxSolutions, bool fAllowLookup)
{
    vIP.clear();
 
    {
        CNetAddr addr;
        if (addr.SetSpecial(std::string(pszName))) {
            vIP.push_back(addr);
            return true;
        }
    }
 
#ifdef HAVE_GETADDRINFO_A
    struct in_addr ipv4_addr;
#ifdef HAVE_INET_PTON
    if (inet_pton(AF_INET, pszName, &ipv4_addr) > 0) {
        vIP.push_back(CNetAddr(ipv4_addr));
        return true;
    }
 
    struct in6_addr ipv6_addr;
    if (inet_pton(AF_INET6, pszName, &ipv6_addr) > 0) {
        vIP.push_back(CNetAddr(ipv6_addr));
        return true;
    }
#else
    ipv4_addr.s_addr = inet_addr(pszName);
    if (ipv4_addr.s_addr != INADDR_NONE) {
        vIP.push_back(CNetAddr(ipv4_addr));
        return true;
    }
#endif
#endif
 
    struct addrinfo aiHint;
    memset(&aiHint, 0, sizeof(struct addrinfo));
    aiHint.ai_socktype = SOCK_STREAM;
    aiHint.ai_protocol = IPPROTO_TCP;
    aiHint.ai_family = AF_UNSPEC;
    aiHint.ai_flags = fAllowLookup ? AI_ADDRCONFIG : AI_NUMERICHOST;
 
    struct addrinfo* aiRes = NULL;
#ifdef HAVE_GETADDRINFO_A
    struct gaicb gcb, *query = &gcb;
    memset(query, 0, sizeof(struct gaicb));
    gcb.ar_name = pszName;
    gcb.ar_request = &aiHint;
    int nErr = getaddrinfo_a(GAI_NOWAIT, &query, 1, NULL);
    if (nErr)
        return false;
 
    do {
        // Should set the timeout limit to a resonable value to avoid
        // generating unnecessary checking call during the polling loop,
        // while it can still response to stop request quick enough.
        // 2 seconds looks fine in our situation.
        struct timespec ts = {2, 0};
        gai_suspend(&query, 1, &ts);
        boost::this_thread::interruption_point();
 
        nErr = gai_error(query);
        if (0 == nErr)
            aiRes = query->ar_result;
    } while (nErr == EAI_INPROGRESS);
#else
    int nErr = getaddrinfo(pszName, NULL, &aiHint, &aiRes);
#endif
    if (nErr)
        return false;
 
    struct addrinfo* aiTrav = aiRes;
    while (aiTrav != NULL && (nMaxSolutions == 0 || vIP.size() < nMaxSolutions)) {
        if (aiTrav->ai_family == AF_INET) {
            assert(aiTrav->ai_addrlen >= sizeof(sockaddr_in));
            vIP.push_back(CNetAddr(((struct sockaddr_in*)(aiTrav->ai_addr))->sin_addr));
        }
 
        if (aiTrav->ai_family == AF_INET6) {
            assert(aiTrav->ai_addrlen >= sizeof(sockaddr_in6));
            vIP.push_back(CNetAddr(((struct sockaddr_in6*)(aiTrav->ai_addr))->sin6_addr));
        }
 
        aiTrav = aiTrav->ai_next;
    }
 
    freeaddrinfo(aiRes);
 
    return (vIP.size() > 0);
}
 
bool LookupHost(const char* pszName, std::vector<CNetAddr>& vIP, unsigned int nMaxSolutions, bool fAllowLookup)
{
    std::string strHost(pszName);
    if (strHost.empty())
        return false;
    if (boost::algorithm::starts_with(strHost, "[") && boost::algorithm::ends_with(strHost, "]")) {
        strHost = strHost.substr(1, strHost.size() - 2);
    }
 
    return LookupIntern(strHost.c_str(), vIP, nMaxSolutions, fAllowLookup);
}
 
bool LookupHost(const char* pszName, CNetAddr& addr, bool fAllowLookup)
{
    std::vector<CNetAddr> vIP;
    LookupHost(pszName, vIP, 1, fAllowLookup);
    if(vIP.empty())
        return false;
    addr = vIP.front();
    return true;
}
 
bool Lookup(const char* pszName, std::vector<CService>& vAddr, int portDefault, bool fAllowLookup, unsigned int nMaxSolutions)
{
    if (pszName[0] == 0)
        return false;
    int port = portDefault;
    std::string hostname = "";
    SplitHostPort(std::string(pszName), port, hostname);
 
    std::vector<CNetAddr> vIP;
    bool fRet = LookupIntern(hostname.c_str(), vIP, nMaxSolutions, fAllowLookup);
    if (!fRet)
        return false;
    vAddr.resize(vIP.size());
    for (unsigned int i = 0; i < vIP.size(); i++)
        vAddr[i] = CService(vIP[i], port);
    return true;
}
 
bool Lookup(const char* pszName, CService& addr, int portDefault, bool fAllowLookup)
{
    std::vector<CService> vService;
    bool fRet = Lookup(pszName, vService, portDefault, fAllowLookup, 1);
    if (!fRet)
        return false;
    addr = vService[0];
    return true;
}
 
CService LookupNumeric(const char* pszName, int portDefault)
{
    CService addr;
    // "1.2:345" will fail to resolve the ip, but will still set the port.
    // If the ip fails to resolve, re-init the result.
    if(!Lookup(pszName, addr, portDefault, false))
        addr = CService();
    return addr;
}
 
struct timeval MillisToTimeval(int64_t nTimeout)
{
    struct timeval timeout;
    timeout.tv_sec = nTimeout / 1000;
    timeout.tv_usec = (nTimeout % 1000) * 1000;
    return timeout;
}
 
enum class IntrRecvError {
    OK,
    Timeout,
    Disconnected,
    NetworkError,
    Interrupted
};
 
static IntrRecvError InterruptibleRecv(char* data, size_t len, int timeout, SOCKET& hSocket)
{
    int64_t curTime = GetTimeMillis();
    int64_t endTime = curTime + timeout;
    // Maximum time to wait in one select call. It will take up until this time (in millis)
    // to break off in case of an interruption.
    const int64_t maxWait = 1000;
    while (len > 0 && curTime < endTime) {
        ssize_t ret = recv(hSocket, data, len, 0); // Optimistically try the recv first
        if (ret > 0) {
            len -= ret;
            data += ret;
        } else if (ret == 0) { // Unexpected disconnection
            return IntrRecvError::Disconnected;
        } else { // Other error or blocking
            int nErr = WSAGetLastError();
            if (nErr == WSAEINPROGRESS || nErr == WSAEWOULDBLOCK || nErr == WSAEINVAL) {
                if (!IsSelectableSocket(hSocket)) {
                    return IntrRecvError::NetworkError;
                }
                struct timeval tval = MillisToTimeval(std::min(endTime - curTime, maxWait));
                fd_set fdset;
                FD_ZERO(&fdset);
                FD_SET(hSocket, &fdset);
                int nRet = select(hSocket + 1, &fdset, NULL, NULL, &tval);
                if (nRet == SOCKET_ERROR) {
                    return IntrRecvError::NetworkError;
                }
            } else {
                return IntrRecvError::NetworkError;
            }
        }
        boost::this_thread::interruption_point();
        curTime = GetTimeMillis();
    }
    return len == 0 ? IntrRecvError::OK : IntrRecvError::Timeout;
}
 
struct ProxyCredentials
{
    std::string username;
    std::string password;
};
 
bool static Socks5(std::string strDest, int port, const ProxyCredentials *auth, SOCKET& hSocket)
{
    IntrRecvError recvr;
    LogPrintf("SOCKS5 connecting %s\n", strDest);
    if (strDest.size() > 255) {
        CloseSocket(hSocket);
        return error("Hostname too long");
    }
    // Accepted authentication methods
    std::vector<uint8_t> vSocks5Init;
    vSocks5Init.push_back(0x05);
    if (auth) {
        vSocks5Init.push_back(0x02); // # METHODS
        vSocks5Init.push_back(0x00); // X'00' NO AUTHENTICATION REQUIRED
        vSocks5Init.push_back(0x02); // X'02' USERNAME/PASSWORD (RFC1929)
    } else {
        vSocks5Init.push_back(0x01); // # METHODS
        vSocks5Init.push_back(0x00); // X'00' NO AUTHENTICATION REQUIRED
    }
    ssize_t ret = send(hSocket, (const char*)vSocks5Init.data(), vSocks5Init.size(), MSG_NOSIGNAL);
    if (ret != (ssize_t)vSocks5Init.size()) {
        CloseSocket(hSocket);
        return error("Error sending to proxy");
    }
    char pchRet1[2];
    if ((recvr = InterruptibleRecv(pchRet1, 2, SOCKS5_RECV_TIMEOUT, hSocket)) != IntrRecvError::OK) {
        CloseSocket(hSocket);
        return error("Error reading proxy response");
    }
    if (pchRet1[0] != 0x05) {
        CloseSocket(hSocket);
        return error("Proxy failed to initialize");
    }
    if (pchRet1[1] == 0x02 && auth) {
        // Perform username/password authentication (as described in RFC1929)
        std::vector<uint8_t> vAuth;
        vAuth.push_back(0x01);
        if (auth->username.size() > 255 || auth->password.size() > 255)
            return error("Proxy username or password too long");
        vAuth.push_back(auth->username.size());
        vAuth.insert(vAuth.end(), auth->username.begin(), auth->username.end());
        vAuth.push_back(auth->password.size());
        vAuth.insert(vAuth.end(), auth->password.begin(), auth->password.end());
        ret = send(hSocket, (const char*)vAuth.data(), vAuth.size(), MSG_NOSIGNAL);
        if (ret != (ssize_t)vAuth.size()) {
            CloseSocket(hSocket);
            return error("Error sending authentication to proxy");
        }
        LogPrint(BCLog::PROXY, "SOCKS5 sending proxy authentication %s:%s\n", auth->username, auth->password);
        char pchRetA[2];
        if ((recvr = InterruptibleRecv(pchRetA, 2, SOCKS5_RECV_TIMEOUT, hSocket)) != IntrRecvError::OK) {
            CloseSocket(hSocket);
            return error("Error reading proxy authentication response");
        }
        if (pchRetA[0] != 0x01 || pchRetA[1] != 0x00) {
            CloseSocket(hSocket);
            return error("Proxy authentication unsuccesful");
        }
    } else if (pchRet1[1] == 0x00) {
        // Perform no authentication
    } else {
        CloseSocket(hSocket);
        return error("Proxy requested wrong authentication method %02x", pchRet1[1]);
    }
    std::vector<uint8_t> vSocks5;
    vSocks5.push_back(0x05); // VER protocol version
    vSocks5.push_back(0x01); // CMD CONNECT
    vSocks5.push_back(0x00); // RSV Reserved
    vSocks5.push_back(0x03); // ATYP DOMAINNAME
    vSocks5.push_back(strDest.size()); // Length<=255 is checked at beginning of function
    vSocks5.insert(vSocks5.end(), strDest.begin(), strDest.end());
    vSocks5.push_back((port >> 8) & 0xFF);
    vSocks5.push_back((port >> 0) & 0xFF);
    ret = send(hSocket, (const char*)vSocks5.data(), vSocks5.size(), MSG_NOSIGNAL);
    if (ret != (ssize_t)vSocks5.size()) {
        CloseSocket(hSocket);
        return error("Error sending to proxy");
    }
    char pchRet2[4];
    if ((recvr = InterruptibleRecv(pchRet2, 4, SOCKS5_RECV_TIMEOUT, hSocket)) != IntrRecvError::OK) {
        CloseSocket(hSocket);
        if (recvr == IntrRecvError::Timeout) {
            /* If a timeout happens here, this effectively means we timed out while connecting
             * to the remote node. This is very common for Tor, so do not print an
             * error message. */
            return false;
        } else {
            return error("Error while reading proxy response");
        }
    }
    if (pchRet2[0] != 0x05) {
        CloseSocket(hSocket);
        return error("Proxy failed to accept request");
    }
    if (pchRet2[1] != 0x00) {
        CloseSocket(hSocket);
        switch (pchRet2[1]) {
        case 0x01:
            return error("Proxy error: general failure");
        case 0x02:
            return error("Proxy error: connection not allowed");
        case 0x03:
            return error("Proxy error: network unreachable");
        case 0x04:
            return error("Proxy error: host unreachable");
        case 0x05:
            return error("Proxy error: connection refused");
        case 0x06:
            return error("Proxy error: TTL expired");
        case 0x07:
            return error("Proxy error: protocol error");
        case 0x08:
            return error("Proxy error: address type not supported");
        default:
            return error("Proxy error: unknown");
        }
    }
    if (pchRet2[2] != 0x00) {
        CloseSocket(hSocket);
        return error("Error: malformed proxy response");
    }
    char pchRet3[256];
    switch (pchRet2[3]) {
    case 0x01:
        recvr = InterruptibleRecv(pchRet3, 4, SOCKS5_RECV_TIMEOUT, hSocket);
        break;
    case 0x04:
        recvr = InterruptibleRecv(pchRet3, 16, SOCKS5_RECV_TIMEOUT, hSocket);
        break;
    case 0x03: {
        recvr = InterruptibleRecv(pchRet3, 1, SOCKS5_RECV_TIMEOUT, hSocket);
        if (recvr != IntrRecvError::OK) {
            CloseSocket(hSocket);
            return error("Error reading from proxy");
        }
        int nRecv = pchRet3[0];
        recvr = InterruptibleRecv(pchRet3, nRecv, SOCKS5_RECV_TIMEOUT, hSocket);
        break;
    }
    default:
        CloseSocket(hSocket);
        return error("Error: malformed proxy response");
    }
    if (recvr != IntrRecvError::OK) {
        CloseSocket(hSocket);
        return error("Error reading from proxy");
    }
    if ((recvr = InterruptibleRecv(pchRet3, 2, SOCKS5_RECV_TIMEOUT, hSocket)) != IntrRecvError::OK) {
        CloseSocket(hSocket);
        return error("Error reading from proxy");
    }
    LogPrintf("SOCKS5 connected %s\n", strDest);
    return true;
}
 
bool static ConnectSocketDirectly(const CService& addrConnect, SOCKET& hSocketRet, int nTimeout)
{
    hSocketRet = INVALID_SOCKET;
 
    struct sockaddr_storage sockaddr;
    socklen_t len = sizeof(sockaddr);
    if (!addrConnect.GetSockAddr((struct sockaddr*)&sockaddr, &len)) {
        LogPrintf("Cannot connect to %s: unsupported network\n", addrConnect.ToString());
        return false;
    }
 
    SOCKET hSocket = socket(((struct sockaddr*)&sockaddr)->sa_family, SOCK_STREAM, IPPROTO_TCP);
    if (hSocket == INVALID_SOCKET)
        return false;
 
#ifdef SO_NOSIGPIPE
    int set = 1;
    // Different way of disabling SIGPIPE on BSD
    setsockopt(hSocket, SOL_SOCKET, SO_NOSIGPIPE, (void*)&set, sizeof(int));
#endif
 
    // Set to non-blocking
    if (!SetSocketNonBlocking(hSocket, true))
        return error("ConnectSocketDirectly: Setting socket to non-blocking failed, error %s\n", NetworkErrorString(WSAGetLastError()));
 
    if (connect(hSocket, (struct sockaddr*)&sockaddr, len) == SOCKET_ERROR) {
        int nErr = WSAGetLastError();
        // WSAEINVAL is here because some legacy version of winsock uses it
        if (nErr == WSAEINPROGRESS || nErr == WSAEWOULDBLOCK || nErr == WSAEINVAL) {
            struct timeval timeout = MillisToTimeval(nTimeout);
            fd_set fdset;
            FD_ZERO(&fdset);
            FD_SET(hSocket, &fdset);
            int nRet = select(hSocket + 1, NULL, &fdset, NULL, &timeout);
            if (nRet == 0) {
                LogPrint(BCLog::NET, "connection to %s timeout\n", addrConnect.ToString());
                CloseSocket(hSocket);
                return false;
            }
            if (nRet == SOCKET_ERROR) {
                LogPrintf("select() for %s failed: %s\n", addrConnect.ToString(), NetworkErrorString(WSAGetLastError()));
                CloseSocket(hSocket);
                return false;
            }
            socklen_t nRetSize = sizeof(nRet);
#ifdef WIN32
            if (getsockopt(hSocket, SOL_SOCKET, SO_ERROR, (char*)(&nRet), &nRetSize) == SOCKET_ERROR)
#else
            if (getsockopt(hSocket, SOL_SOCKET, SO_ERROR, &nRet, &nRetSize) == SOCKET_ERROR)
#endif
            {
                LogPrintf("getsockopt() for %s failed: %s\n", addrConnect.ToString(), NetworkErrorString(WSAGetLastError()));
                CloseSocket(hSocket);
                return false;
            }
            if (nRet != 0) {
                LogPrintf("connect() to %s failed after select(): %s\n", addrConnect.ToString(), NetworkErrorString(nRet));
                CloseSocket(hSocket);
                return false;
            }
        }
#ifdef WIN32
        else if (WSAGetLastError() != WSAEISCONN)
#else
        else
#endif
        {
            LogPrintf("connect() to %s failed: %s\n", addrConnect.ToString(), NetworkErrorString(WSAGetLastError()));
            CloseSocket(hSocket);
            return false;
        }
    }
 
    hSocketRet = hSocket;
    return true;
}
 
bool SetProxy(enum Network net, const proxyType &addrProxy)
{
    assert(net >= 0 && net < NET_MAX);
    if (!addrProxy.IsValid())
        return false;
    LOCK(cs_proxyInfos);
    proxyInfo[net] = addrProxy;
    return true;
}
 
bool GetProxy(enum Network net, proxyType& proxyInfoOut)
{
    assert(net >= 0 && net < NET_MAX);
    LOCK(cs_proxyInfos);
    if (!proxyInfo[net].IsValid())
        return false;
    proxyInfoOut = proxyInfo[net];
    return true;
}
 
bool SetNameProxy(const proxyType &addrProxy)
{
    if (!addrProxy.IsValid())
        return false;
    LOCK(cs_proxyInfos);
    nameProxy = addrProxy;
    return true;
}
 
bool GetNameProxy(proxyType &nameProxyOut)
{
    LOCK(cs_proxyInfos);
    if (!nameProxy.IsValid())
        return false;
    nameProxyOut = nameProxy;
    return true;
}
 
bool HaveNameProxy()
{
    LOCK(cs_proxyInfos);
    return nameProxy.IsValid();
}
 
bool IsProxy(const CNetAddr& addr)
{
    LOCK(cs_proxyInfos);
    for (int i = 0; i < NET_MAX; i++) {
        if (addr == (CNetAddr)proxyInfo[i].proxy)
            return true;
    }
    return false;
}
 
static bool ConnectThroughProxy(const proxyType &proxy, const std::string strDest, int port, SOCKET& hSocketRet, int nTimeout, bool *outProxyConnectionFailed)
{
    SOCKET hSocket = INVALID_SOCKET;
    // first connect to proxy server
    if (!ConnectSocketDirectly(proxy.proxy, hSocket, nTimeout)) {
        if (outProxyConnectionFailed)
            *outProxyConnectionFailed = true;
        return false;
    }
    // do socks negotiation
    if (proxy.randomize_credentials) {
        ProxyCredentials random_auth;
        static std::atomic_int counter;
        random_auth.username = random_auth.password = strprintf("%i", counter++);
        if (!Socks5(strDest, (unsigned short)port, &random_auth, hSocket))
            return false;
    } else {
        if (!Socks5(strDest, (unsigned short)port, 0, hSocket))
            return false;
    }
 
    hSocketRet = hSocket;
    return true;
}
 
bool ConnectSocket(const CService &addrDest, SOCKET& hSocketRet, int nTimeout, bool *outProxyConnectionFailed)
{
    proxyType proxy;
    if (outProxyConnectionFailed)
        *outProxyConnectionFailed = false;
 
    if (GetProxy(addrDest.GetNetwork(), proxy))
        return ConnectThroughProxy(proxy, addrDest.ToStringIP(), addrDest.GetPort(), hSocketRet, nTimeout, outProxyConnectionFailed);
    else // no proxy needed (none set for target network)
        return ConnectSocketDirectly(addrDest, hSocketRet, nTimeout);
}
 
bool ConnectSocketByName(CService& addr, SOCKET& hSocketRet, const char* pszDest, int portDefault, int nTimeout, bool* outProxyConnectionFailed)
{
    std::string strDest;
    int port = portDefault;
 
    if (outProxyConnectionFailed)
        *outProxyConnectionFailed = false;
 
    SplitHostPort(std::string(pszDest), port, strDest);
 
    proxyType nameProxy;
    GetNameProxy(nameProxy);
 
    std::vector<CService> addrResolved;
    if (Lookup(strDest.c_str(), addrResolved, port, fNameLookup && !HaveNameProxy(), 256)) {
        if (addrResolved.size() > 0) {
            addr = addrResolved[GetRand(addrResolved.size())];
            return ConnectSocket(addr, hSocketRet, nTimeout);
        }
    }
 
    addr = CService();
 
    if (!HaveNameProxy())
        return false;
    return ConnectThroughProxy(nameProxy, strDest, port, hSocketRet, nTimeout, outProxyConnectionFailed);
}
 
bool LookupSubNet(const char* pszName, CSubNet& ret)
{
    std::string strSubnet(pszName);
    size_t slash = strSubnet.find_last_of('/');
    std::vector<CNetAddr> vIP;
 
    std::string strAddress = strSubnet.substr(0, slash);
    if (LookupHost(strAddress.c_str(), vIP, 1, false))
    {
        CNetAddr network = vIP[0];
        if (slash != strSubnet.npos)
        {
            std::string strNetmask = strSubnet.substr(slash + 1);
            int32_t n;
            // IPv4 addresses start at offset 12, and first 12 bytes must match, so just offset n
            if (ParseInt32(strNetmask, &n)) { // If valid number, assume /24 syntax
                ret = CSubNet(network, n);
                return ret.IsValid();
            }
            else // If not a valid number, try full netmask syntax
            {
                // Never allow lookup for netmask
                if (LookupHost(strNetmask.c_str(), vIP, 1, false)) {
                    ret = CSubNet(network, vIP[0]);
                    return ret.IsValid();
                }
            }
        }
        else
        {
            ret = CSubNet(network);
            return ret.IsValid();
        }
    }
    return false;
}
 
#ifdef WIN32
std::string NetworkErrorString(int err)
{
    char buf[256];
    buf[0] = 0;
    if (FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS | FORMAT_MESSAGE_MAX_WIDTH_MASK,
            NULL, err, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
            buf, sizeof(buf), NULL)) {
        return strprintf("%s (%d)", buf, err);
    } else {
        return strprintf("Unknown error (%d)", err);
    }
}
#else
std::string NetworkErrorString(int err)
{
    char buf[256];
    const char* s = buf;
    buf[0] = 0;
/* Too bad there are two incompatible implementations of the
     * thread-safe strerror. */
#ifdef STRERROR_R_CHAR_P /* GNU variant can return a pointer outside the passed buffer */
    s = strerror_r(err, buf, sizeof(buf));
#else                    /* POSIX variant always returns message in buffer */
    if (strerror_r(err, buf, sizeof(buf)))
        buf[0] = 0;
#endif
    return strprintf("%s (%d)", s, err);
}
#endif
 
bool CloseSocket(SOCKET& hSocket)
{
    if (hSocket == INVALID_SOCKET)
        return false;
#ifdef WIN32
    int ret = closesocket(hSocket);
#else
    int ret = close(hSocket);
#endif
    if (ret) {
        LogPrint(BCLog::NET, "Socket close failed: %d. Error: %s\n", hSocket, NetworkErrorString(WSAGetLastError()));
    }
    hSocket = INVALID_SOCKET;
    return ret != SOCKET_ERROR;
}
 
bool SetSocketNonBlocking(SOCKET& hSocket, bool fNonBlocking)
{
    if (fNonBlocking) {
#ifdef WIN32
        u_long nOne = 1;
        if (ioctlsocket(hSocket, FIONBIO, &nOne) == SOCKET_ERROR) {
#else
        int fFlags = fcntl(hSocket, F_GETFL, 0);
        if (fcntl(hSocket, F_SETFL, fFlags | O_NONBLOCK) == SOCKET_ERROR) {
#endif
            CloseSocket(hSocket);
            return false;
        }
    } else {
#ifdef WIN32
        u_long nZero = 0;
        if (ioctlsocket(hSocket, FIONBIO, &nZero) == SOCKET_ERROR) {
#else
        int fFlags = fcntl(hSocket, F_GETFL, 0);
        if (fcntl(hSocket, F_SETFL, fFlags & ~O_NONBLOCK) == SOCKET_ERROR) {
#endif
            CloseSocket(hSocket);
            return false;
        }
    }
 
    return true;
}