public DnsDatagram Resolve(DnsDatagram request)
{
int bytesRecv;
byte[] responseBuffer = null;
int nextServerIndex = 0;
int retries = _retries;
byte[] requestBuffer;
IDnsCache dnsCache = null;
//serialize request
using (MemoryStream mS = new MemoryStream(32))
{
if (_tcp)
{
mS.Position = 2;
}
//write dns datagram
request.WriteTo(mS);
requestBuffer = mS.ToArray();
if (_tcp)
{
byte[] length = BitConverter.GetBytes(Convert.ToUInt16(requestBuffer.Length - 2));
requestBuffer[0] = length[1];
requestBuffer[1] = length[0];
}
}
//init server selection parameters
if (_servers.Length > 1)
{
retries = retries * _servers.Length; //retries on per server basis
byte[] select = new byte[1];
_rnd.GetBytes(select);
nextServerIndex = select[0] % _servers.Length;
}
int retry = 0;
while (retry < retries)
{
//select server
NameServerAddress server;
if (_servers.Length > 1)
{
server = _servers[nextServerIndex];
nextServerIndex = (nextServerIndex + 1) % _servers.Length;
}
else
{
server = _servers[0];
}
if (server.EndPoint == null)
{
if (dnsCache == null)
{
dnsCache = new SimpleDnsCache();
}
server.ResolveAddress(dnsCache, _proxy, _preferIPv6, _tcp, _retries);
if (server.EndPoint == null)
{
retry++;
continue;
}
}
//query server
Socket _socket = null;
SocksUdpAssociateRequestHandler proxyRequestHandler = null;
try
{
retry++;
DateTime sentAt = DateTime.UtcNow;
bool dnsTcp;
if (_proxy == null)
{
if (_tcp)
{
_socket = new Socket(server.EndPoint.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
_socket.NoDelay = true;
_socket.SendTimeout = _sendTimeout;
_socket.ReceiveTimeout = _recvTimeout;
IAsyncResult result = _socket.BeginConnect(server.EndPoint, null, null);
if (!result.AsyncWaitHandle.WaitOne(_connectionTimeout))
{
throw new SocketException((int)SocketError.TimedOut);
}
if (!_socket.Connected)
{
throw new SocketException((int)SocketError.ConnectionRefused);
}
}
else
{
_socket = new Socket(server.EndPoint.AddressFamily, SocketType.Dgram, ProtocolType.Udp);
_socket.SendTimeout = _sendTimeout;
_socket.ReceiveTimeout = _recvTimeout;
}
dnsTcp = _tcp;
}
else
{
switch (_proxy.Type)
{
case NetProxyType.Http:
_socket = _proxy.HttpProxy.Connect(server.EndPoint, _connectionTimeout);
_socket.NoDelay = true;
_socket.SendTimeout = _sendTimeout;
_socket.ReceiveTimeout = _recvTimeout;
dnsTcp = true;
break;
case NetProxyType.Socks5:
if (!_tcp)
{
try
{
proxyRequestHandler = _proxy.SocksProxy.UdpAssociate(_connectionTimeout);
proxyRequestHandler.ReceiveTimeout = _recvTimeout;
dnsTcp = false;
break;
}
catch (SocksClientException)
{ }
}
using (SocksConnectRequestHandler requestHandler = _proxy.SocksProxy.Connect(server.EndPoint, _connectionTimeout))
{
_socket = requestHandler.GetSocket();
_socket.NoDelay = true;
_socket.SendTimeout = _sendTimeout;
_socket.ReceiveTimeout = _recvTimeout;
dnsTcp = true;
}
break;
default:
throw new NotSupportedException("Proxy type not supported by DnsClient.");
}
}
if (dnsTcp)
{
_socket.Send(requestBuffer);
if ((responseBuffer == null) || (responseBuffer.Length == 512))
{
responseBuffer = new byte[64 * 1024];
}
bytesRecv = _socket.Receive(responseBuffer, 0, 2, SocketFlags.None);
if (bytesRecv < 1)
{
throw new SocketException((int)SocketError.ConnectionReset);
}
Array.Reverse(responseBuffer, 0, 2);
ushort length = BitConverter.ToUInt16(responseBuffer, 0);
int offset = 0;
while (offset < length)
{
bytesRecv = _socket.Receive(responseBuffer, offset, length, SocketFlags.None);
if (bytesRecv < 1)
{
throw new SocketException((int)SocketError.ConnectionReset);
}
offset += bytesRecv;
}
bytesRecv = length;
}
else
{
if (responseBuffer == null)
{
responseBuffer = new byte[512];
}
if (proxyRequestHandler == null)
{
_socket.SendTo(requestBuffer, server.EndPoint);
EndPoint remoteEP;
if (server.EndPoint.AddressFamily == AddressFamily.InterNetworkV6)
{
remoteEP = new IPEndPoint(IPAddress.IPv6Any, 0);
}
else
{
remoteEP = new IPEndPoint(IPAddress.Any, 0);
}
bytesRecv = _socket.ReceiveFrom(responseBuffer, ref remoteEP);
}
else
{
proxyRequestHandler.SendTo(requestBuffer, 0, requestBuffer.Length, new SocksEndPoint(server.EndPoint));
bytesRecv = proxyRequestHandler.ReceiveFrom(responseBuffer, 0, responseBuffer.Length, out SocksEndPoint socksRemoteEP);
}
}
//parse response
using (MemoryStream mS = new MemoryStream(responseBuffer, 0, bytesRecv, false))
{
double rtt = (DateTime.UtcNow - sentAt).TotalMilliseconds;
DnsDatagram response = new DnsDatagram(mS, server, (_tcp ? ProtocolType.Tcp : ProtocolType.Udp), rtt);
if (response.Header.Identifier == request.Header.Identifier)
{
return(response);
}
}
}
catch (SocketException)
{ }
finally
{
if (_socket != null)
{
_socket.Dispose();
}
if (proxyRequestHandler != null)
{
proxyRequestHandler.Dispose();
}
}
}
throw new DnsClientException("DnsClient failed to resolve the request: no response from name servers.");
}
protected override void UpdateTracker(TrackerClientEvent @event, IPEndPoint clientEP)
{
SocksUdpAssociateRequestHandler proxyRequestHandler = null;
UdpClient udpClient = null;
if (_proxy == null)
{
udpClient = new UdpClient(_trackerURI.Host, _trackerURI.Port);
udpClient.Client.ReceiveTimeout = 10000;
}
else
{
switch (_proxy.Type)
{
case NetProxyType.Socks5:
proxyRequestHandler = _proxy.SocksProxy.UdpAssociate();
proxyRequestHandler.ReceiveTimeout = 10000;
break;
case NetProxyType.Http:
throw new NotSupportedException("Http proxy not supported by Udp tracker.");
default:
throw new NotSupportedException("Proxy type not supported by Udp tracker.");
}
}
try
{
for (int n = 0; n < 2; n++)
{
if ((_connectionID == null) || (_connectionIDExpires <= DateTime.UtcNow))
{
//GET CONNECTION ID
_rnd.GetBytes(_transactionID);
_connectionID = GetConnectionID(udpClient, proxyRequestHandler, _transactionID);
_connectionIDExpires = DateTime.UtcNow.AddMinutes(1);
}
try
{
_rnd.GetBytes(_transactionID);
byte[] announceResponse;
int announceResponseLength = GetAnnounceResponse(udpClient, proxyRequestHandler, _transactionID, _connectionID, @event, clientEP, out announceResponse);
byte[] buffer = new byte[4];
Buffer.BlockCopy(announceResponse, 8, buffer, 0, 4);
Array.Reverse(buffer);
_interval = BitConverter.ToInt32(buffer, 0);
Buffer.BlockCopy(announceResponse, 12, buffer, 0, 4);
Array.Reverse(buffer);
_leachers = BitConverter.ToInt32(buffer, 0);
Buffer.BlockCopy(announceResponse, 16, buffer, 0, 4);
Array.Reverse(buffer);
_seeders = BitConverter.ToInt32(buffer, 0);
_peers.Clear();
if (_proxy == null)
{
if (udpClient.Client.AddressFamily == AddressFamily.InterNetworkV6)
{
ParsePeersIPv6(announceResponse, announceResponseLength, _peers);
}
else
{
ParsePeersIPv4(announceResponse, announceResponseLength, _peers);
}
}
else
{
int x = (announceResponseLength - 26) % 6;
if (x == 0)
{
ParsePeersIPv4(announceResponse, announceResponseLength, _peers);
}
else
{
ParsePeersIPv6(announceResponse, announceResponseLength, _peers);
}
}
return;
}
catch (SocketException ex)
{
if (ex.ErrorCode != (int)SocketError.TimedOut)
{
throw new TrackerClientException(ex.Message, ex);
}
}
}
throw new TrackerClientException("No response from tracker.");
}
finally
{
if (proxyRequestHandler != null)
{
proxyRequestHandler.Dispose();
}
if (udpClient != null)
{
udpClient.Close();
}
}
}
private byte[] GetConnectionID(UdpClient udpClient, SocksUdpAssociateRequestHandler proxyRequestHandler, byte[] transactionID)
{
//Connection_id 64bit 0x41727101980 + action 32bit + transaction_id 32bit (random)
byte[] requestPacket = new byte[] { 0x0, 0x0, 0x4, 0x17, 0x27, 0x10, 0x19, 0x80, 0x0, 0x0, 0x0, 0x0, transactionID[0], transactionID[1], transactionID[2], transactionID[3] };
for (int n = 0; n < 2; n++)
{
if (_proxy == null)
{
udpClient.Client.ReceiveTimeout = 15 * (2 ^ n) * 1000;
}
else
{
proxyRequestHandler.ReceiveTimeout = 15 * (2 ^ n) * 1000;
}
try
{
//SEND CONNECT REQUEST
if (_proxy == null)
{
udpClient.Send(requestPacket, requestPacket.Length);
}
else
{
proxyRequestHandler.SendTo(requestPacket, 0, requestPacket.Length, new SocksEndPoint(_trackerURI.Host, _trackerURI.Port));
}
//RECV CONNECT RESPONSE
byte[] response;
int responseLength;
if (_proxy == null)
{
IPEndPoint remoteEP = null;
response = udpClient.Receive(ref remoteEP);
responseLength = response.Length;
}
else
{
response = new byte[128];
SocksEndPoint remoteEP;
responseLength = proxyRequestHandler.ReceiveFrom(response, 0, response.Length, out remoteEP);
}
//check response length
if (responseLength < 16)
{
throw new TrackerClientException("Invalid response received for connection request.");
}
//check transaction id
for (int j = 0; j < 4; j++)
{
if (response[4 + j] != transactionID[j])
{
throw new TrackerClientException("Invalid transaction id received for connection request.");
}
}
//check action
for (int j = 0; j < 4; j++)
{
if (response[j] != 0)
{
throw new TrackerClientException("Invalid action received for connection request.");
}
}
byte[] connectionID = new byte[8];
Buffer.BlockCopy(response, 8, connectionID, 0, 8);
return(connectionID);
}
catch (SocketException ex)
{
if (ex.ErrorCode != (int)SocketError.TimedOut)
{
throw new TrackerClientException(ex.Message, ex);
}
}
}
throw new TrackerClientException("No response from tracker.");
}
private int GetAnnounceResponse(UdpClient udpClient, SocksUdpAssociateRequestHandler proxyRequestHandler, byte[] transactionID, byte[] connectionID, TrackerClientEvent @event, IPEndPoint clientEP, out byte[] response)
{
byte[] request = new byte[98];
//connection_id 64bit
Buffer.BlockCopy(connectionID, 0, request, 0, 8);
//action 32bit
request[11] = 1;
//transaction_id 32bit
Buffer.BlockCopy(transactionID, 0, request, 12, 4);
//info_hash 20 bytes
Buffer.BlockCopy(_infoHash, 0, request, 16, 20);
//peer_id 20 bytes
Buffer.BlockCopy(_clientID.PeerID, 0, request, 36, 20);
//downloaded 64bit
//left 64bit
//uploaded 64bit
//event 32bit
request[83] = Convert.ToByte(@event);
//ip address 32bit
if (clientEP.Address.AddressFamily == AddressFamily.InterNetwork)
{
switch (clientEP.Address.ToString())
{
case "0.0.0.0":
case "127.0.0.1":
break;
default:
Buffer.BlockCopy(clientEP.Address.GetAddressBytes(), 0, request, 84, 4);
break;
}
}
//key 32bit
Buffer.BlockCopy(_clientID.ClientKey, 0, request, 88, 4);
//num_want
Buffer.BlockCopy(BitConverter.GetBytes(_clientID.NumWant), 0, request, 92, 4);
//port 16bit
byte[] portBuffer = BitConverter.GetBytes(clientEP.Port);
Array.Reverse(portBuffer);
Buffer.BlockCopy(portBuffer, 2, request, 96, 2);
int responseLength;
if (_proxy == null)
{
//SEND ANNOUNCE REQUEST
udpClient.Send(request, request.Length);
//RECV ANNOUNCE RESPONSE
IPEndPoint remoteEP = null;
response = udpClient.Receive(ref remoteEP);
responseLength = response.Length;
}
else
{
//SEND ANNOUNCE REQUEST
proxyRequestHandler.SendTo(request, 0, request.Length, new SocksEndPoint(_trackerURI.Host, _trackerURI.Port));
//RECV ANNOUNCE RESPONSE
response = new byte[1024];
SocksEndPoint remoteEP;
responseLength = proxyRequestHandler.ReceiveFrom(response, 0, response.Length, out remoteEP);
}
//check response length
if (responseLength < 20)
{
throw new TrackerClientException("Invalid response received for announce request.");
}
//check response transaction id
for (int j = 0; j < 4; j++)
{
if (response[4 + j] != transactionID[j])
{
throw new TrackerClientException("Invalid transaction id received for announce request.");
}
}
//check response action
if (response[3] != 1)
{
throw new TrackerClientException("Invalid action received for announce request.");
}
return(responseLength);
}
