text: // Copyright (c) 2011-2018 The Bitcoin Core developers
  // Copyright (c) 2017 The Raven Core developers
  // Copyright (c) 2018 The Rito Core developers
  // Copyright (c) 2019 The Liquidcash Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #ifdef HAVE_CONFIG_H
  #include "config/liquidcash-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>
  
  #ifndef WIN32
  #include <fcntl.h>
  #endif
  
  #include <boost/algorithm/string/case_conv.hpp> // for to_lower()
  #include <boost/algorithm/string/predicate.hpp> // for startswith() and endswith()
  
  #if !defined(HAVE_MSG_NOSIGNAL)
  #define MSG_NOSIGNAL 0
  #endif
  
  // Settings
  static proxyType proxyInfo[NET_MAX];
  static proxyType nameProxy;
  static CCriticalSection cs_proxyInfos;
  int nConnectTimeout = DEFAULT_CONNECT_TIMEOUT;
  bool fNameLookup = DEFAULT_NAME_LOOKUP;
  
  // Need ample time for negotiation for very slow proxies such as Tor (milliseconds)
  static const int SOCKS5_RECV_TIMEOUT = 20 * 1000;
  static std::atomic<bool> interruptSocks5Recv(false);
  
  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 "";
      }
  }
  
  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;
          }
      }
  
      struct addrinfo aiHint;
      memset(&aiHint, 0, sizeof(struct addrinfo));
  
      aiHint.ai_socktype = SOCK_STREAM;
      aiHint.ai_protocol = IPPROTO_TCP;
      aiHint.ai_family = AF_UNSPEC;
  #ifdef WIN32
      aiHint.ai_flags = fAllowLookup ? 0 : AI_NUMERICHOST;
  #else
      aiHint.ai_flags = fAllowLookup ? AI_ADDRCONFIG : AI_NUMERICHOST;
  #endif
      struct addrinfo *aiRes = nullptr;
      int nErr = getaddrinfo(pszName, nullptr, &aiHint, &aiRes);
      if (nErr)
          return false;
  
      struct addrinfo *aiTrav = aiRes;
      while (aiTrav != nullptr && (nMaxSolutions == 0 || vIP.size() < nMaxSolutions))
      {
          CNetAddr resolved;
          if (aiTrav->ai_family == AF_INET)
          {
              assert(aiTrav->ai_addrlen >= sizeof(sockaddr_in));
              resolved = CNetAddr(((struct sockaddr_in*)(aiTrav->ai_addr))->sin_addr);
          }
  
          if (aiTrav->ai_family == AF_INET6)
          {
              assert(aiTrav->ai_addrlen >= sizeof(sockaddr_in6));
              struct sockaddr_in6* s6 = (struct sockaddr_in6*) aiTrav->ai_addr;
              resolved = CNetAddr(s6->sin6_addr, s6->sin6_scope_id);
          }
          /* Never allow resolving to an internal address. Consider any such result invalid */
          if (!resolved.IsInternal()) {
              vIP.push_back(resolved);
          }
  
          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;
  }
  
  /** SOCKS version */
  enum SOCKSVersion: uint8_t {
      SOCKS4 = 0x04,
      SOCKS5 = 0x05
  };
  
  /** Values defined for METHOD in RFC1928 */
  enum SOCKS5Method: uint8_t {
      NOAUTH = 0x00,        //! No authentication required
      GSSAPI = 0x01,        //! GSSAPI
      USER_PASS = 0x02,     //! Username/password
      NO_ACCEPTABLE = 0xff, //! No acceptable methods
  };
  
  /** Values defined for CMD in RFC1928 */
  enum SOCKS5Command: uint8_t {
      CONNECT = 0x01,
      BIND = 0x02,
      UDP_ASSOCIATE = 0x03
  };
  
  /** Values defined for REP in RFC1928 */
  enum SOCKS5Reply: uint8_t {
      SUCCEEDED = 0x00,        //! Succeeded
      GENFAILURE = 0x01,       //! General failure
      NOTALLOWED = 0x02,       //! Connection not allowed by ruleset
      NETUNREACHABLE = 0x03,   //! Network unreachable
      HOSTUNREACHABLE = 0x04,  //! Network unreachable
      CONNREFUSED = 0x05,      //! Connection refused
      TTLEXPIRED = 0x06,       //! TTL expired
      CMDUNSUPPORTED = 0x07,   //! Command not supported
      ATYPEUNSUPPORTED = 0x08, //! Address type not supported
  };
  
  /** Values defined for ATYPE in RFC1928 */
  enum SOCKS5Atyp: uint8_t {
      IPV4 = 0x01,
      DOMAINNAME = 0x03,
      IPV6 = 0x04,
  };
  
  /** Status codes that can be returned by InterruptibleRecv */
  enum class IntrRecvError {
      OK,
      Timeout,
      Disconnected,
      NetworkError,
      Interrupted
  };
  
  /**
   * Read bytes from socket. This will either read the full number of bytes requested
   * or return False on error or timeout.
   * This function can be interrupted by calling InterruptSocks5()
   *
   * @param data Buffer to receive into
   * @param len  Length of data to receive
   * @param timeout  Timeout in milliseconds for receive operation
   *
   * @note This function requires that hSocket is in non-blocking mode.
   */
  static IntrRecvError InterruptibleRecv(uint8_t* data, size_t len, int timeout, const 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, (char*)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, nullptr, nullptr, &tval);
                  if (nRet == SOCKET_ERROR) {
                      return IntrRecvError::NetworkError;
                  }
              } else {
                  return IntrRecvError::NetworkError;
              }
          }
          if (interruptSocks5Recv)
              return IntrRecvError::Interrupted;
          curTime = GetTimeMillis();
      }
      return len == 0 ? IntrRecvError::OK : IntrRecvError::Timeout;
  }
  
  /** Credentials for proxy authentication */
  struct ProxyCredentials
  {
      std::string username;
      std::string password;
  };
  
  /** Convert SOCKS5 reply to an error message */
  std::string Socks5ErrorString(uint8_t err)
  {
      switch(err) {
          case SOCKS5Reply::GENFAILURE:
              return "general failure";
          case SOCKS5Reply::NOTALLOWED:
              return "connection not allowed";
          case SOCKS5Reply::NETUNREACHABLE:
              return "network unreachable";
          case SOCKS5Reply::HOSTUNREACHABLE:
              return "host unreachable";
          case SOCKS5Reply::CONNREFUSED:
              return "connection refused";
          case SOCKS5Reply::TTLEXPIRED:
              return "TTL expired";
          case SOCKS5Reply::CMDUNSUPPORTED:
              return "protocol error";
          case SOCKS5Reply::ATYPEUNSUPPORTED:
              return "address type not supported";
          default:
              return "unknown";
      }
  }
  
  /** Connect using SOCKS5 (as described in RFC1928) */
  static bool Socks5(const std::string& strDest, int port, const ProxyCredentials *auth, SOCKET& hSocket)
  {
      IntrRecvError recvr;
      LogPrint(BCLog::NET, "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(SOCKSVersion::SOCKS5);
      if (auth) {
          vSocks5Init.push_back(0x02); // Number of methods
          vSocks5Init.push_back(SOCKS5Method::NOAUTH);
          vSocks5Init.push_back(SOCKS5Method::USER_PASS);
      } else {
          vSocks5Init.push_back(0x01); // Number of methods
          vSocks5Init.push_back(SOCKS5Method::NOAUTH);
      }
      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");
      }
      uint8_t pchRet1[2];
      if ((recvr = InterruptibleRecv(pchRet1, 2, SOCKS5_RECV_TIMEOUT, hSocket)) != IntrRecvError::OK) {
          CloseSocket(hSocket);
          LogPrintf("Socks5() connect to %s:%d failed: InterruptibleRecv() timeout or other failure\n", strDest, port);
          return false;
      }
      if (pchRet1[0] != SOCKSVersion::SOCKS5) {
          CloseSocket(hSocket);
          return error("Proxy failed to initialize");
      }
      if (pchRet1[1] == SOCKS5Method::USER_PASS && auth) {
          // Perform username/password authentication (as described in RFC1929)
          std::vector<uint8_t> vAuth;
          vAuth.push_back(0x01); // Current (and only) version of user/pass subnegotiation
          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);
          uint8_t 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 unsuccessful");
          }
      } else if (pchRet1[1] == SOCKS5Method::NOAUTH) {
          // Perform no authentication
      } else {
          CloseSocket(hSocket);
          return error("Proxy requested wrong authentication method %02x", pchRet1[1]);
      }
      std::vector<uint8_t> vSocks5;
      vSocks5.push_back(SOCKSVersion::SOCKS5); // VER protocol version
      vSocks5.push_back(SOCKS5Command::CONNECT); // CMD CONNECT
      vSocks5.push_back(0x00); // RSV Reserved must be 0
      vSocks5.push_back(SOCKS5Atyp::DOMAINNAME); // 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");
      }
      uint8_t 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] != SOCKSVersion::SOCKS5) {
          CloseSocket(hSocket);
          return error("Proxy failed to accept request");
      }
      if (pchRet2[1] != SOCKS5Reply::SUCCEEDED) {
          // Failures to connect to a peer that are not proxy errors
          CloseSocket(hSocket);
          LogPrintf("Socks5() connect to %s:%d failed: %s\n", strDest, port, Socks5ErrorString(pchRet2[1]));
          return false;
      }
      if (pchRet2[2] != 0x00) { // Reserved field must be 0
          CloseSocket(hSocket);
          return error("Error: malformed proxy response");
      }
      uint8_t pchRet3[256];
      switch (pchRet2[3])
      {
          case SOCKS5Atyp::IPV4: recvr = InterruptibleRecv(pchRet3, 4, SOCKS5_RECV_TIMEOUT, hSocket); break;
          case SOCKS5Atyp::IPV6: recvr = InterruptibleRecv(pchRet3, 16, SOCKS5_RECV_TIMEOUT, hSocket); break;
          case SOCKS5Atyp::DOMAINNAME:
          {
              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");
      }
      LogPrint(BCLog::NET, "SOCKS5 connected %s\n", strDest);
      return true;
  }
  
  bool 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
  
      //Disable Nagle's algorithm
      SetSocketNoDelay(hSocket);
  
      // Set to non-blocking
      if (!SetSocketNonBlocking(hSocket, true)) {
          CloseSocket(hSocket);
          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, nullptr, &fdset, nullptr, &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;
  }
  
  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(0);
          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 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,
              nullptr, err, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
              buf, sizeof(buf), nullptr))
      {
          return strprintf("%s (%d)", buf, err);
      }
      else
      {
          return strprintf("Unknown error (%d)", err);
      }
  }
  #else
  std::string NetworkErrorString(int err)
  {
      char buf[256];
      buf[0] = 0;
      /* Too bad there are two incompatible implementations of the
       * thread-safe strerror. */
      const char *s;
  #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 */
      s = buf;
      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
      hSocket = INVALID_SOCKET;
      return ret != SOCKET_ERROR;
  }
  
  bool SetSocketNonBlocking(const 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
              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
              return false;
          }
      }
  
      return true;
  }
  
  bool SetSocketNoDelay(const SOCKET& hSocket)
  {
      int set = 1;
      int rc = setsockopt(hSocket, IPPROTO_TCP, TCP_NODELAY, (const char*)&set, sizeof(int));
      return rc == 0;
  }
  
  void InterruptSocks5(bool interrupt)
  {
      interruptSocks5Recv = interrupt;
  }
  