text: // Copyright (c) 2009-2010 Satoshi Nakamoto
  // Copyright (c) 2009-2014 The Bitcoin developers
  // Copyright (c) 2017 The Securypto 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/securypto-config.h"
  #endif
  
  #include "netbase.h"
  
  #include "hash.h"
  #include "sync.h"
  #include "uint256.h"
  #include "random.h"
  #include "util.h"
  #include "utilstrencodings.h"
  
  #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
  
  using namespace std;
  
  // Settings
  static proxyType proxyInfo[NET_MAX];
  static proxyType nameProxy;
  static CCriticalSection cs_proxyInfos;
  int nConnectTimeout = DEFAULT_CONNECT_TIMEOUT;
  bool fNameLookup = false;
  
  static const unsigned char pchIPv4[12] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xff, 0xff};
  
  // 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;
  #ifdef WIN32
      aiHint.ai_flags = fAllowLookup ? 0 : AI_NUMERICHOST;
  #else
      aiHint.ai_flags = fAllowLookup ? AI_ADDRCONFIG : AI_NUMERICHOST;
  #endif
  
      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 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;
  }
  
  bool LookupNumeric(const char* pszName, CService& addr, int portDefault)
  {
      return Lookup(pszName, addr, portDefault, false);
  }
  
  struct timeval MillisToTimeval(int64_t nTimeout)
  {
      struct timeval timeout;
      timeout.tv_sec = nTimeout / 1000;
      timeout.tv_usec = (nTimeout % 1000) * 1000;
      return timeout;
  }
  
  /**
   * 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 boost thread interrupt.
   *
   * @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.
   */
  bool static 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 false;
          } else { // Other error or blocking
              int nErr = WSAGetLastError();
              if (nErr == WSAEINPROGRESS || nErr == WSAEWOULDBLOCK || nErr == WSAEINVAL) {
                  if (!IsSelectableSocket(hSocket)) {
                      return false;
                  }
                  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 false;
                  }
              } else {
                  return false;
              }
          }
          boost::this_thread::interruption_point();
          curTime = GetTimeMillis();
      }
      return len == 0;
  }
  
  struct ProxyCredentials
  {
      std::string username;
      std::string password;
  };
  
  /** Connect using SOCKS5 (as described in RFC1928) */
  bool static Socks5(string strDest, int port, const ProxyCredentials *auth, SOCKET& hSocket)
  {
      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*)begin_ptr(vSocks5Init), vSocks5Init.size(), MSG_NOSIGNAL);
      if (ret != (ssize_t)vSocks5Init.size()) {
          CloseSocket(hSocket);
          return error("Error sending to proxy");
      }
      char pchRet1[2];
      if (!InterruptibleRecv(pchRet1, 2, SOCKS5_RECV_TIMEOUT, hSocket)) {
          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*)begin_ptr(vAuth), vAuth.size(), MSG_NOSIGNAL);
          if (ret != (ssize_t)vAuth.size()) {
              CloseSocket(hSocket);
              return error("Error sending authentication to proxy");
          }
          LogPrint("proxy", "SOCKS5 sending proxy authentication %s:%s\n", auth->username, auth->password);
          char pchRetA[2];
          if (!InterruptibleRecv(pchRetA, 2, SOCKS5_RECV_TIMEOUT, hSocket)) {
              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*)begin_ptr(vSocks5), vSocks5.size(), MSG_NOSIGNAL);
      if (ret != (ssize_t)vSocks5.size()) {
          CloseSocket(hSocket);
          return error("Error sending to proxy");
      }
      char pchRet2[4];
      if (!InterruptibleRecv(pchRet2, 4, SOCKS5_RECV_TIMEOUT, hSocket)) {
          CloseSocket(hSocket);
          return error("Error 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:
          ret = InterruptibleRecv(pchRet3, 4, SOCKS5_RECV_TIMEOUT, hSocket);
          break;
      case 0x04:
          ret = InterruptibleRecv(pchRet3, 16, SOCKS5_RECV_TIMEOUT, hSocket);
          break;
      case 0x03: {
          ret = InterruptibleRecv(pchRet3, 1, SOCKS5_RECV_TIMEOUT, hSocket);
          if (!ret) {
              CloseSocket(hSocket);
              return error("Error reading from proxy");
          }
          int nRecv = pchRet3[0];
          ret = InterruptibleRecv(pchRet3, nRecv, SOCKS5_RECV_TIMEOUT, hSocket);
          break;
      }
      default:
          CloseSocket(hSocket);
          return error("Error: malformed proxy response");
      }
      if (!ret) {
          CloseSocket(hSocket);
          return error("Error reading from proxy");
      }
      if (!InterruptibleRecv(pchRet3, 2, SOCKS5_RECV_TIMEOUT, hSocket)) {
          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("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;
          random_auth.username = strprintf("%i", insecure_rand());
          random_auth.password = strprintf("%i", insecure_rand());
          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)
  {
      string strDest;
      int port = portDefault;
  
      if (outProxyConnectionFailed)
          *outProxyConnectionFailed = false;
  
      SplitHostPort(string(pszDest), port, strDest);
  
      proxyType nameProxy;
      GetNameProxy(nameProxy);
  
      CService addrResolved(CNetAddr(strDest, fNameLookup && !HaveNameProxy()), port);
      if (addrResolved.IsValid()) {
          addr = addrResolved;
          return ConnectSocket(addr, hSocketRet, nTimeout);
      }
  
      addr = CService("0.0.0.0:0");
  
      if (!HaveNameProxy())
          return false;
      return ConnectThroughProxy(nameProxy, strDest, port, hSocketRet, nTimeout, outProxyConnectionFailed);
  }
  
  void CNetAddr::Init()
  {
      memset(ip, 0, sizeof(ip));
  }
  
  void CNetAddr::SetIP(const CNetAddr& ipIn)
  {
      memcpy(ip, ipIn.ip, sizeof(ip));
  }
  
  void CNetAddr::SetRaw(Network network, const uint8_t* ip_in)
  {
      switch (network) {
      case NET_IPV4:
          memcpy(ip, pchIPv4, 12);
          memcpy(ip + 12, ip_in, 4);
          break;
      case NET_IPV6:
          memcpy(ip, ip_in, 16);
          break;
      default:
          assert(!"invalid network");
      }
  }
  
  static const unsigned char pchOnionCat[] = {0xFD, 0x87, 0xD8, 0x7E, 0xEB, 0x43};
  
  bool CNetAddr::SetSpecial(const std::string& strName)
  {
      if (strName.size() > 6 && strName.substr(strName.size() - 6, 6) == ".onion") {
          std::vector<unsigned char> vchAddr = DecodeBase32(strName.substr(0, strName.size() - 6).c_str());
          if (vchAddr.size() != 16 - sizeof(pchOnionCat))
              return false;
          memcpy(ip, pchOnionCat, sizeof(pchOnionCat));
          for (unsigned int i = 0; i < 16 - sizeof(pchOnionCat); i++)
              ip[i + sizeof(pchOnionCat)] = vchAddr[i];
          return true;
      }
      return false;
  }
  
  CNetAddr::CNetAddr()
  {
      Init();
  }
  
  CNetAddr::CNetAddr(const struct in_addr& ipv4Addr)
  {
      SetRaw(NET_IPV4, (const uint8_t*)&ipv4Addr);
  }
  
  CNetAddr::CNetAddr(const struct in6_addr& ipv6Addr)
  {
      SetRaw(NET_IPV6, (const uint8_t*)&ipv6Addr);
  }
  
  CNetAddr::CNetAddr(const char* pszIp, bool fAllowLookup)
  {
      Init();
      std::vector<CNetAddr> vIP;
      if (LookupHost(pszIp, vIP, 1, fAllowLookup))
          *this = vIP[0];
  }
  
  CNetAddr::CNetAddr(const std::string& strIp, bool fAllowLookup)
  {
      Init();
      std::vector<CNetAddr> vIP;
      if (LookupHost(strIp.c_str(), vIP, 1, fAllowLookup))
          *this = vIP[0];
  }
  
  unsigned int CNetAddr::GetByte(int n) const
  {
      return ip[15 - n];
  }
  
  bool CNetAddr::IsIPv4() const
  {
      return (memcmp(ip, pchIPv4, sizeof(pchIPv4)) == 0);
  }
  
  bool CNetAddr::IsIPv6() const
  {
      return (!IsIPv4() && !IsTor());
  }
  
  bool CNetAddr::IsRFC1918() const
  {
      return IsIPv4() && (GetByte(3) == 10 ||
                             (GetByte(3) == 192 && GetByte(2) == 168) ||
                             (GetByte(3) == 172 && (GetByte(2) >= 16 && GetByte(2) <= 31)));
  }
  
  bool CNetAddr::IsRFC2544() const
  {
      return IsIPv4() && GetByte(3) == 198 && (GetByte(2) == 18 || GetByte(2) == 19);
  }
  
  bool CNetAddr::IsRFC3927() const
  {
      return IsIPv4() && (GetByte(3) == 169 && GetByte(2) == 254);
  }
  
  bool CNetAddr::IsRFC6598() const
  {
      return IsIPv4() && GetByte(3) == 100 && GetByte(2) >= 64 && GetByte(2) <= 127;
  }
  
  bool CNetAddr::IsRFC5737() const
  {
      return IsIPv4() && ((GetByte(3) == 192 && GetByte(2) == 0 && GetByte(1) == 2) ||
                             (GetByte(3) == 198 && GetByte(2) == 51 && GetByte(1) == 100) ||
                             (GetByte(3) == 203 && GetByte(2) == 0 && GetByte(1) == 113));
  }
  
  bool CNetAddr::IsRFC3849() const
  {
      return GetByte(15) == 0x20 && GetByte(14) == 0x01 && GetByte(13) == 0x0D && GetByte(12) == 0xB8;
  }
  
  bool CNetAddr::IsRFC3964() const
  {
      return (GetByte(15) == 0x20 && GetByte(14) == 0x02);
  }
  
  bool CNetAddr::IsRFC6052() const
  {
      static const unsigned char pchRFC6052[] = {0, 0x64, 0xFF, 0x9B, 0, 0, 0, 0, 0, 0, 0, 0};
      return (memcmp(ip, pchRFC6052, sizeof(pchRFC6052)) == 0);
  }
  
  bool CNetAddr::IsRFC4380() const
  {
      return (GetByte(15) == 0x20 && GetByte(14) == 0x01 && GetByte(13) == 0 && GetByte(12) == 0);
  }
  
  bool CNetAddr::IsRFC4862() const
  {
      static const unsigned char pchRFC4862[] = {0xFE, 0x80, 0, 0, 0, 0, 0, 0};
      return (memcmp(ip, pchRFC4862, sizeof(pchRFC4862)) == 0);
  }
  
  bool CNetAddr::IsRFC4193() const
  {
      return ((GetByte(15) & 0xFE) == 0xFC);
  }
  
  bool CNetAddr::IsRFC6145() const
  {
      static const unsigned char pchRFC6145[] = {0, 0, 0, 0, 0, 0, 0, 0, 0xFF, 0xFF, 0, 0};
      return (memcmp(ip, pchRFC6145, sizeof(pchRFC6145)) == 0);
  }
  
  bool CNetAddr::IsRFC4843() const
  {
      return (GetByte(15) == 0x20 && GetByte(14) == 0x01 && GetByte(13) == 0x00 && (GetByte(12) & 0xF0) == 0x10);
  }
  
  bool CNetAddr::IsTor() const
  {
      return (memcmp(ip, pchOnionCat, sizeof(pchOnionCat)) == 0);
  }
  
  bool CNetAddr::IsLocal() const
  {
      // IPv4 loopback
      if (IsIPv4() && (GetByte(3) == 127 || GetByte(3) == 0))
          return true;
  
      // IPv6 loopback (::1/128)
      static const unsigned char pchLocal[16] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1};
      if (memcmp(ip, pchLocal, 16) == 0)
          return true;
  
      return false;
  }
  
  bool CNetAddr::IsMulticast() const
  {
      return (IsIPv4() && (GetByte(3) & 0xF0) == 0xE0) || (GetByte(15) == 0xFF);
  }
  
  bool CNetAddr::IsValid() const
  {
      // Cleanup 3-byte shifted addresses caused by garbage in size field
      // of addr messages from versions before 0.2.9 checksum.
      // Two consecutive addr messages look like this:
      // header20 vectorlen3 addr26 addr26 addr26 header20 vectorlen3 addr26 addr26 addr26...
      // so if the first length field is garbled, it reads the second batch
      // of addr misaligned by 3 bytes.
      if (memcmp(ip, pchIPv4 + 3, sizeof(pchIPv4) - 3) == 0)
          return false;
  
      // unspecified IPv6 address (::/128)
      unsigned char ipNone[16] = {};
      if (memcmp(ip, ipNone, 16) == 0)
          return false;
  
      // documentation IPv6 address
      if (IsRFC3849())
          return false;
  
      if (IsIPv4()) {
          // INADDR_NONE
          uint32_t ipNone = INADDR_NONE;
          if (memcmp(ip + 12, &ipNone, 4) == 0)
              return false;
  
          // 0
          ipNone = 0;
          if (memcmp(ip + 12, &ipNone, 4) == 0)
              return false;
      }
  
      return true;
  }
  
  bool CNetAddr::IsRoutable() const
  {
      return IsValid() && !(IsRFC1918() || IsRFC2544() || IsRFC3927() || IsRFC4862() || IsRFC6598() || IsRFC5737() || (IsRFC4193() && !IsTor()) || IsRFC4843() || IsLocal());
  }
  
  enum Network CNetAddr::GetNetwork() const
  {
      if (!IsRoutable())
          return NET_UNROUTABLE;
  
      if (IsIPv4())
          return NET_IPV4;
  
      if (IsTor())
          return NET_TOR;
  
      return NET_IPV6;
  }
  
  std::string CNetAddr::ToStringIP() const
  {
      if (IsTor())
          return EncodeBase32(&ip[6], 10) + ".onion";
      CService serv(*this, 0);
      struct sockaddr_storage sockaddr;
      socklen_t socklen = sizeof(sockaddr);
      if (serv.GetSockAddr((struct sockaddr*)&sockaddr, &socklen)) {
          char name[1025] = "";
          if (!getnameinfo((const struct sockaddr*)&sockaddr, socklen, name, sizeof(name), NULL, 0, NI_NUMERICHOST))
              return std::string(name);
      }
      if (IsIPv4())
          return strprintf("%u.%u.%u.%u", GetByte(3), GetByte(2), GetByte(1), GetByte(0));
      else
          return strprintf("%x:%x:%x:%x:%x:%x:%x:%x",
              GetByte(15) << 8 | GetByte(14), GetByte(13) << 8 | GetByte(12),
              GetByte(11) << 8 | GetByte(10), GetByte(9) << 8 | GetByte(8),
              GetByte(7) << 8 | GetByte(6), GetByte(5) << 8 | GetByte(4),
              GetByte(3) << 8 | GetByte(2), GetByte(1) << 8 | GetByte(0));
  }
  
  std::string CNetAddr::ToString() const
  {
      return ToStringIP();
  }
  
  bool operator==(const CNetAddr& a, const CNetAddr& b)
  {
      return (memcmp(a.ip, b.ip, 16) == 0);
  }
  
  bool operator!=(const CNetAddr& a, const CNetAddr& b)
  {
      return (memcmp(a.ip, b.ip, 16) != 0);
  }
  
  bool operator<(const CNetAddr& a, const CNetAddr& b)
  {
      return (memcmp(a.ip, b.ip, 16) < 0);
  }
  
  bool CNetAddr::GetInAddr(struct in_addr* pipv4Addr) const
  {
      if (!IsIPv4())
          return false;
      memcpy(pipv4Addr, ip + 12, 4);
      return true;
  }
  
  bool CNetAddr::GetIn6Addr(struct in6_addr* pipv6Addr) const
  {
      memcpy(pipv6Addr, ip, 16);
      return true;
  }
  
  // get canonical identifier of an address' group
  // no two connections will be attempted to addresses with the same group
  std::vector<unsigned char> CNetAddr::GetGroup() const
  {
      std::vector<unsigned char> vchRet;
      int nClass = NET_IPV6;
      int nStartByte = 0;
      int nBits = 16;
  
      // all local addresses belong to the same group
      if (IsLocal()) {
          nClass = 255;
          nBits = 0;
      }
  
      // all unroutable addresses belong to the same group
      if (!IsRoutable()) {
          nClass = NET_UNROUTABLE;
          nBits = 0;
      }
      // for IPv4 addresses, '1' + the 16 higher-order bits of the IP
      // includes mapped IPv4, SIIT translated IPv4, and the well-known prefix
      else if (IsIPv4() || IsRFC6145() || IsRFC6052()) {
          nClass = NET_IPV4;
          nStartByte = 12;
      }
      // for 6to4 tunnelled addresses, use the encapsulated IPv4 address
      else if (IsRFC3964()) {
          nClass = NET_IPV4;
          nStartByte = 2;
      }
      // for Teredo-tunnelled IPv6 addresses, use the encapsulated IPv4 address
      else if (IsRFC4380()) {
          vchRet.push_back(NET_IPV4);
          vchRet.push_back(GetByte(3) ^ 0xFF);
          vchRet.push_back(GetByte(2) ^ 0xFF);
          return vchRet;
      } else if (IsTor()) {
          nClass = NET_TOR;
          nStartByte = 6;
          nBits = 4;
      }
      // for he.net, use /36 groups
      else if (GetByte(15) == 0x20 && GetByte(14) == 0x01 && GetByte(13) == 0x04 && GetByte(12) == 0x70)
          nBits = 36;
      // for the rest of the IPv6 network, use /32 groups
      else
          nBits = 32;
  
      vchRet.push_back(nClass);
      while (nBits >= 8) {
          vchRet.push_back(GetByte(15 - nStartByte));
          nStartByte++;
          nBits -= 8;
      }
      if (nBits > 0)
          vchRet.push_back(GetByte(15 - nStartByte) | ((1 << nBits) - 1));
  
      return vchRet;
  }
  
  uint64_t CNetAddr::GetHash() const
  {
      uint256 hash = Hash(&ip[0], &ip[16]);
      uint64_t nRet;
      memcpy(&nRet, &hash, sizeof(nRet));
      return nRet;
  }
  
  // private extensions to enum Network, only returned by GetExtNetwork,
  // and only used in GetReachabilityFrom
  static const int NET_UNKNOWN = NET_MAX + 0;
  static const int NET_TEREDO = NET_MAX + 1;
  int static GetExtNetwork(const CNetAddr* addr)
  {
      if (addr == NULL)
          return NET_UNKNOWN;
      if (addr->IsRFC4380())
          return NET_TEREDO;
      return addr->GetNetwork();
  }
  
  /** Calculates a metric for how reachable (*this) is from a given partner */
  int CNetAddr::GetReachabilityFrom(const CNetAddr* paddrPartner) const
  {
      enum Reachability {
          REACH_UNREACHABLE,
          REACH_DEFAULT,
          REACH_TEREDO,
          REACH_IPV6_WEAK,
          REACH_IPV4,
          REACH_IPV6_STRONG,
          REACH_PRIVATE
      };
  
      if (!IsRoutable())
          return REACH_UNREACHABLE;
  
      int ourNet = GetExtNetwork(this);
      int theirNet = GetExtNetwork(paddrPartner);
      bool fTunnel = IsRFC3964() || IsRFC6052() || IsRFC6145();
  
      switch (theirNet) {
      case NET_IPV4:
          switch (ourNet) {
          default:
              return REACH_DEFAULT;
          case NET_IPV4:
              return REACH_IPV4;
          }
      case NET_IPV6:
          switch (ourNet) {
          default:
              return REACH_DEFAULT;
          case NET_TEREDO:
              return REACH_TEREDO;
          case NET_IPV4:
              return REACH_IPV4;
          case NET_IPV6:
              return fTunnel ? REACH_IPV6_WEAK : REACH_IPV6_STRONG; // only prefer giving our IPv6 address if it's not tunnelled
          }
      case NET_TOR:
          switch (ourNet) {
          default:
              return REACH_DEFAULT;
          case NET_IPV4:
              return REACH_IPV4; // Tor users can connect to IPv4 as well
          case NET_TOR:
              return REACH_PRIVATE;
          }
      case NET_TEREDO:
          switch (ourNet) {
          default:
              return REACH_DEFAULT;
          case NET_TEREDO:
              return REACH_TEREDO;
          case NET_IPV6:
              return REACH_IPV6_WEAK;
          case NET_IPV4:
              return REACH_IPV4;
          }
      case NET_UNKNOWN:
      case NET_UNROUTABLE:
      default:
          switch (ourNet) {
          default:
              return REACH_DEFAULT;
          case NET_TEREDO:
              return REACH_TEREDO;
          case NET_IPV6:
              return REACH_IPV6_WEAK;
          case NET_IPV4:
              return REACH_IPV4;
          case NET_TOR:
              return REACH_PRIVATE; // either from Tor, or don't care about our address
          }
      }
  }
  
  void CService::Init()
  {
      port = 0;
  }
  
  CService::CService()
  {
      Init();
  }
  
  CService::CService(const CNetAddr& cip, unsigned short portIn) : CNetAddr(cip), port(portIn)
  {
  }
  
  CService::CService(const struct in_addr& ipv4Addr, unsigned short portIn) : CNetAddr(ipv4Addr), port(portIn)
  {
  }
  
  CService::CService(const struct in6_addr& ipv6Addr, unsigned short portIn) : CNetAddr(ipv6Addr), port(portIn)
  {
  }
  
  CService::CService(const struct sockaddr_in& addr) : CNetAddr(addr.sin_addr), port(ntohs(addr.sin_port))
  {
      assert(addr.sin_family == AF_INET);
  }
  
  CService::CService(const struct sockaddr_in6& addr) : CNetAddr(addr.sin6_addr), port(ntohs(addr.sin6_port))
  {
      assert(addr.sin6_family == AF_INET6);
  }
  
  bool CService::SetSockAddr(const struct sockaddr* paddr)
  {
      switch (paddr->sa_family) {
      case AF_INET:
          *this = CService(*(const struct sockaddr_in*)paddr);
          return true;
      case AF_INET6:
          *this = CService(*(const struct sockaddr_in6*)paddr);
          return true;
      default:
          return false;
      }
  }
  
  CService::CService(const char* pszIpPort, bool fAllowLookup)
  {
      Init();
      CService ip;
      if (Lookup(pszIpPort, ip, 0, fAllowLookup))
          *this = ip;
  }
  
  CService::CService(const char* pszIpPort, int portDefault, bool fAllowLookup)
  {
      Init();
      CService ip;
      if (Lookup(pszIpPort, ip, portDefault, fAllowLookup))
          *this = ip;
  }
  
  CService::CService(const std::string& strIpPort, bool fAllowLookup)
  {
      Init();
      CService ip;
      if (Lookup(strIpPort.c_str(), ip, 0, fAllowLookup))
          *this = ip;
  }
  
  CService::CService(const std::string& strIpPort, int portDefault, bool fAllowLookup)
  {
      Init();
      CService ip;
      if (Lookup(strIpPort.c_str(), ip, portDefault, fAllowLookup))
          *this = ip;
  }
  
  unsigned short CService::GetPort() const
  {
      return port;
  }
  
  bool operator==(const CService& a, const CService& b)
  {
      return (CNetAddr)a == (CNetAddr)b && a.port == b.port;
  }
  
  bool operator!=(const CService& a, const CService& b)
  {
      return (CNetAddr)a != (CNetAddr)b || a.port != b.port;
  }
  
  bool operator<(const CService& a, const CService& b)
  {
      return (CNetAddr)a < (CNetAddr)b || ((CNetAddr)a == (CNetAddr)b && a.port < b.port);
  }
  
  bool CService::GetSockAddr(struct sockaddr* paddr, socklen_t* addrlen) const
  {
      if (IsIPv4()) {
          if (*addrlen < (socklen_t)sizeof(struct sockaddr_in))
              return false;
          *addrlen = sizeof(struct sockaddr_in);
          struct sockaddr_in* paddrin = (struct sockaddr_in*)paddr;
          memset(paddrin, 0, *addrlen);
          if (!GetInAddr(&paddrin->sin_addr))
              return false;
          paddrin->sin_family = AF_INET;
          paddrin->sin_port = htons(port);
          return true;
      }
      if (IsIPv6()) {
          if (*addrlen < (socklen_t)sizeof(struct sockaddr_in6))
              return false;
          *addrlen = sizeof(struct sockaddr_in6);
          struct sockaddr_in6* paddrin6 = (struct sockaddr_in6*)paddr;
          memset(paddrin6, 0, *addrlen);
          if (!GetIn6Addr(&paddrin6->sin6_addr))
              return false;
          paddrin6->sin6_family = AF_INET6;
          paddrin6->sin6_port = htons(port);
          return true;
      }
      return false;
  }
  
  std::vector<unsigned char> CService::GetKey() const
  {
      std::vector<unsigned char> vKey;
      vKey.resize(18);
      memcpy(&vKey[0], ip, 16);
      vKey[16] = port / 0x100;
      vKey[17] = port & 0x0FF;
      return vKey;
  }
  
  std::string CService::ToStringPort() const
  {
      return strprintf("%u", port);
  }
  
  std::string CService::ToStringIPPort() const
  {
      if (IsIPv4() || IsTor()) {
          return ToStringIP() + ":" + ToStringPort();
      } else {
          return "[" + ToStringIP() + "]:" + ToStringPort();
      }
  }
  
  std::string CService::ToString() const
  {
      return ToStringIPPort();
  }
  
  void CService::SetPort(unsigned short portIn)
  {
      port = portIn;
  }
  
  CSubNet::CSubNet() : valid(false)
  {
      memset(netmask, 0, sizeof(netmask));
  }
  
  CSubNet::CSubNet(const std::string& strSubnet, bool fAllowLookup)
  {
      size_t slash = strSubnet.find_last_of('/');
      std::vector<CNetAddr> vIP;
  
      valid = true;
      // Default to /32 (IPv4) or /128 (IPv6), i.e. match single address
      memset(netmask, 255, sizeof(netmask));
  
      std::string strAddress = strSubnet.substr(0, slash);
      if (LookupHost(strAddress.c_str(), vIP, 1, fAllowLookup)) {
          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
              const int astartofs = network.IsIPv4() ? 12 : 0;
              if (ParseInt32(strNetmask, &n)) // If valid number, assume /24 symtex
              {
                  if (n >= 0 && n <= (128 - astartofs * 8)) // Only valid if in range of bits of address
                  {
                      n += astartofs * 8;
                      // Clear bits [n..127]
                      for (; n < 128; ++n)
                          netmask[n >> 3] &= ~(1 << (7 - (n & 7)));
                  } else {
                      valid = false;
                  }
              } else // If not a valid number, try full netmask syntax
              {
                  if (LookupHost(strNetmask.c_str(), vIP, 1, false)) // Never allow lookup for netmask
                  {
                      // Copy only the *last* four bytes in case of IPv4, the rest of the mask should stay 1's as
                      // we don't want pchIPv4 to be part of the mask.
                      for (int x = astartofs; x < 16; ++x)
                          netmask[x] = vIP[0].ip[x];
                  } else {
                      valid = false;
                  }
              }
          }
      } else {
          valid = false;
      }
  
      // Normalize network according to netmask
      for (int x = 0; x < 16; ++x)
          network.ip[x] &= netmask[x];
  }
  
  CSubNet::CSubNet(const CNetAddr &addr):
      valid(addr.IsValid())
  {
      memset(netmask, 255, sizeof(netmask));
      network = addr;
  }
  
  bool CSubNet::Match(const CNetAddr& addr) const
  {
      if (!valid || !addr.IsValid())
          return false;
      for (int x = 0; x < 16; ++x)
          if ((addr.ip[x] & netmask[x]) != network.ip[x])
              return false;
      return true;
  }
  
  static inline int NetmaskBits(uint8_t x)
  {
      switch(x) {
      case 0x00: return 0; break;
      case 0x80: return 1; break;
      case 0xc0: return 2; break;
      case 0xe0: return 3; break;
      case 0xf0: return 4; break;
      case 0xf8: return 5; break;
      case 0xfc: return 6; break;
      case 0xfe: return 7; break;
      case 0xff: return 8; break;
      default: return -1; break;
      }
  }
  
  std::string CSubNet::ToString() const
  {
      /* Parse binary 1{n}0{N-n} to see if mask can be represented as /n */
      int cidr = 0;
      bool valid_cidr = true;
      int n = network.IsIPv4() ? 12 : 0;
      for (; n < 16 && netmask[n] == 0xff; ++n)
          cidr += 8;
      if (n < 16) {
          int bits = NetmaskBits(netmask[n]);
          if (bits < 0)
              valid_cidr = false;
          else
              cidr += bits;
          ++n;
      }
      for (; n < 16 && valid_cidr; ++n)
          if (netmask[n] != 0x00)
              valid_cidr = false;
  
      /* Format output */
      std::string strNetmask;
      if (valid_cidr) {
          strNetmask = strprintf("%u", cidr);
      } else {
          if (network.IsIPv4())
              strNetmask = strprintf("%u.%u.%u.%u", netmask[12], netmask[13], netmask[14], netmask[15]);
          else
              strNetmask = strprintf("%x:%x:%x:%x:%x:%x:%x:%x",
                               netmask[0] << 8 | netmask[1], netmask[2] << 8 | netmask[3],
                               netmask[4] << 8 | netmask[5], netmask[6] << 8 | netmask[7],
                               netmask[8] << 8 | netmask[9], netmask[10] << 8 | netmask[11],
                               netmask[12] << 8 | netmask[13], netmask[14] << 8 | netmask[15]);
      }
  
      return network.ToString() + "/" + strNetmask;
  }
  
  bool CSubNet::IsValid() const
  {
      return valid;
  }
  
  bool operator==(const CSubNet& a, const CSubNet& b)
  {
      return a.valid == b.valid && a.network == b.network && !memcmp(a.netmask, b.netmask, 16);
  }
  
  bool operator!=(const CSubNet& a, const CSubNet& b)
  {
      return !(a == b);
  }
  
  bool operator<(const CSubNet& a, const CSubNet& b)
  {
      return (a.network < b.network || (a.network == b.network && memcmp(a.netmask, b.netmask, 16) < 0));
  }
  
  #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
      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;
  }
  