private void EndUdpReceive(IAsyncResult ar)
{
try
{
lock (_udpListener)
{
_hasActiveUdpListener = false;
}
StartUdpListen();
IPEndPoint endpoint;
byte[] buffer = _udpListener.EndReceive(ar, out endpoint);
DnsMessageBase query;
byte[] originalMac;
try
{
query = DnsMessageBase.CreateByFlag(buffer, TsigKeySelector, null);
originalMac = (query.TSigOptions == null) ? null : query.TSigOptions.Mac;
}
catch (Exception e)
{
throw new Exception("Error parsing dns query", e);
}
DnsMessageBase response;
try
{
response = ProcessMessage(query, endpoint.Address, ProtocolType.Udp);
}
catch (Exception ex)
{
OnExceptionThrown(ex);
response = null;
}
if (response == null)
{
response = query;
query.IsQuery = false;
query.ReturnCode = ReturnCode.ServerFailure;
}
int length = response.Encode(false, originalMac, out buffer);
#region Truncating
DnsMessage message = response as DnsMessage;
if (message != null)
{
int maxLength = 512;
if (query.IsEDnsEnabled && message.IsEDnsEnabled)
{
maxLength = Math.Max(512, (int)message.EDnsOptions.UdpPayloadSize);
}
while (length > maxLength)
{
// First step: remove data from additional records except the opt record
if ((message.IsEDnsEnabled && (message.AdditionalRecords.Count > 1)) || (!message.IsEDnsEnabled && (message.AdditionalRecords.Count > 0)))
{
for (int i = message.AdditionalRecords.Count - 1; i >= 0; i--)
{
if (message.AdditionalRecords[i].RecordType != RecordType.Opt)
{
message.AdditionalRecords.RemoveAt(i);
}
}
length = message.Encode(false, originalMac, out buffer);
continue;
}
int savedLength = 0;
if (message.AuthorityRecords.Count > 0)
{
for (int i = message.AuthorityRecords.Count - 1; i >= 0; i--)
{
savedLength += message.AuthorityRecords[i].MaximumLength;
message.AuthorityRecords.RemoveAt(i);
if ((length - savedLength) < maxLength)
{
break;
}
}
message.IsTruncated = true;
length = message.Encode(false, originalMac, out buffer);
continue;
}
if (message.AnswerRecords.Count > 0)
{
for (int i = message.AnswerRecords.Count - 1; i >= 0; i--)
{
savedLength += message.AnswerRecords[i].MaximumLength;
message.AnswerRecords.RemoveAt(i);
if ((length - savedLength) < maxLength)
{
break;
}
}
message.IsTruncated = true;
length = message.Encode(false, originalMac, out buffer);
continue;
}
if (message.Questions.Count > 0)
{
for (int i = message.Questions.Count - 1; i >= 0; i--)
{
savedLength += message.Questions[i].MaximumLength;
message.Questions.RemoveAt(i);
if ((length - savedLength) < maxLength)
{
break;
}
}
message.IsTruncated = true;
length = message.Encode(false, originalMac, out buffer);
}
}
}
#endregion
_udpListener.BeginSend(buffer, 0, length, endpoint, EndUdpSend, null);
}
catch (Exception e)
{
HandleUdpException(e);
}
}
private void UdpReceiveCompleted <TMessage>(IAsyncResult ar)
where TMessage : DnsMessageBase, new()
{
DnsClientAsyncState <TMessage> state = (DnsClientAsyncState <TMessage>)ar.AsyncState;
if (state.Timer != null)
{
state.Timer.Dispose();
}
if (state.TimedOut)
{
state.EndpointInfoIndex++;
UdpBeginSend(state);
}
else
{
try
{
int length = state.UdpClient.EndReceiveFrom(ar, ref state.UdpEndpoint);
byte[] responseData = new byte[length];
Buffer.BlockCopy(state.Buffer, 0, responseData, 0, length);
TMessage response = DnsMessageBase.Parse <TMessage>(responseData, state.TSigKeySelector, state.TSigOriginalMac);
if (AreMultipleResponsesAllowedInParallelMode)
{
if (ValidateResponse(state.Query, response))
{
if (response.IsTcpResendingRequested)
{
TcpBeginConnect <TMessage>(state.CreateTcpCloneWithoutCallback(), ((IPEndPoint)state.UdpEndpoint).Address);
}
else
{
state.Responses.Add(response);
}
}
state.Buffer = new byte[65535];
if (state.EndpointInfos[state.EndpointInfoIndex].IsMulticast)
{
state.UdpEndpoint = new IPEndPoint(state.UdpClient.AddressFamily == AddressFamily.InterNetwork ? IPAddress.Any : IPAddress.IPv6Any, _port);
}
IAsyncResult asyncResult = state.UdpClient.BeginReceiveFrom(state.Buffer, 0, state.Buffer.Length, SocketFlags.None, ref state.UdpEndpoint, UdpReceiveCompleted <TMessage>, state);
state.Timer = new Timer(UdpTimedOut <TMessage>, asyncResult, state.TimeRemaining, Timeout.Infinite);
}
else
{
state.UdpClient.Close();
state.UdpClient = null;
state.UdpEndpoint = null;
if (!ValidateResponse(state.Query, response) || (response.ReturnCode == ReturnCode.ServerFailure))
{
state.EndpointInfoIndex++;
UdpBeginSend(state);
}
else
{
if (response.IsTcpResendingRequested)
{
TcpBeginConnect <TMessage>(state, ((IPEndPoint)state.UdpEndpoint).Address);
}
else
{
state.Responses.Add(response);
state.SetCompleted();
}
}
}
}
catch (Exception e)
{
Trace.TraceError("Error on dns query: " + e);
try
{
state.UdpClient.Close();
state.Timer.Dispose();
}
catch { }
state.EndpointInfoIndex++;
UdpBeginSend(state);
}
}
}
private void TcpReceiveCompleted <TMessage>(IAsyncResult ar)
where TMessage : DnsMessageBase, new()
{
DnsClientAsyncState <TMessage> state = (DnsClientAsyncState <TMessage>)ar.AsyncState;
if (state.Timer != null)
{
state.Timer.Dispose();
}
if (state.TimedOut)
{
state.EndpointInfoIndex++;
TcpBeginConnect(state);
}
else
{
try
{
state.TcpBytesToReceive -= state.TcpStream.EndRead(ar);
if (state.TcpBytesToReceive > 0)
{
IAsyncResult asyncResult = state.TcpStream.BeginRead(state.Buffer, state.Buffer.Length - state.TcpBytesToReceive, state.TcpBytesToReceive, TcpReceiveCompleted <TMessage>, state);
state.Timer = new Timer(TcpTimedOut <TMessage>, asyncResult, state.TimeRemaining, Timeout.Infinite);
}
else
{
byte[] buffer = state.Buffer;
state.Buffer = null;
TMessage response = DnsMessageBase.Parse <TMessage>(buffer, state.TSigKeySelector, state.TSigOriginalMac);
if (!ValidateResponse(state.Query, response) || (response.ReturnCode == ReturnCode.ServerFailure))
{
state.EndpointInfoIndex++;
state.PartialMessage = null;
state.TcpStream.Close();
state.TcpClient.Close();
state.TcpStream = null;
state.TcpClient = null;
TcpBeginConnect(state);
}
else
{
bool isSubsequentResponseMessage = (state.PartialMessage != null);
if (isSubsequentResponseMessage)
{
state.PartialMessage.AnswerRecords.AddRange(response.AnswerRecords);
}
else
{
state.PartialMessage = response;
}
if (response.IsTcpNextMessageWaiting(isSubsequentResponseMessage))
{
state.TcpBytesToReceive = 2;
state.Buffer = new byte[2];
IAsyncResult asyncResult = state.TcpStream.BeginRead(state.Buffer, 0, 2, TcpReceiveLengthCompleted <TMessage>, state);
state.Timer = new Timer(TcpTimedOut <TMessage>, asyncResult, state.TimeRemaining, Timeout.Infinite);
}
else
{
state.TcpStream.Close();
state.TcpClient.Close();
state.TcpStream = null;
state.TcpClient = null;
state.Responses.Add(state.PartialMessage);
state.SetCompleted();
}
}
}
}
catch (Exception e)
{
Trace.TraceError("Error on dns query: " + e);
try
{
state.TcpClient.Close();
state.Timer.Dispose();
}
catch { }
state.EndpointInfoIndex++;
TcpBeginConnect(state);
}
}
}
protected TMessage SendMessage <TMessage>(TMessage message)
where TMessage : DnsMessageBase, new()
{
int messageLength;
byte[] messageData;
DnsServer.SelectTsigKey tsigKeySelector;
byte[] tsigOriginalMac;
PrepareMessage(message, out messageLength, out messageData, out tsigKeySelector, out tsigOriginalMac);
bool sendByTcp = ((messageLength > MaximumQueryMessageSize) || message.IsTcpUsingRequested);
var endpointInfos = GetEndpointInfos <TMessage>();
for (int i = 0; i < endpointInfos.Count; i++)
{
TcpClient tcpClient = null;
NetworkStream tcpStream = null;
try
{
var endpointInfo = endpointInfos[i];
IPAddress responderAddress;
byte[] resultData = sendByTcp ? QueryByTcp(endpointInfo.ServerAddress, messageData, messageLength, ref tcpClient, ref tcpStream, out responderAddress) : QueryByUdp(endpointInfo, messageData, messageLength, out responderAddress);
if (resultData != null)
{
TMessage result;
try
{
result = DnsMessageBase.Parse <TMessage>(resultData, tsigKeySelector, tsigOriginalMac);
}
catch (Exception e)
{
Trace.TraceError("Error on dns query: " + e);
continue;
}
if (!ValidateResponse(message, result))
{
continue;
}
if ((result.ReturnCode == ReturnCode.ServerFailure) && (i != endpointInfos.Count - 1))
{
continue;
}
if (result.IsTcpResendingRequested)
{
resultData = QueryByTcp(responderAddress, messageData, messageLength, ref tcpClient, ref tcpStream, out responderAddress);
if (resultData != null)
{
TMessage tcpResult;
try
{
tcpResult = DnsMessageBase.Parse <TMessage>(resultData, tsigKeySelector, tsigOriginalMac);
}
catch (Exception e)
{
Trace.TraceError("Error on dns query: " + e);
continue;
}
if (tcpResult.ReturnCode == ReturnCode.ServerFailure)
{
if (i != endpointInfos.Count - 1)
{
continue;
}
}
else
{
result = tcpResult;
}
}
}
bool isTcpNextMessageWaiting = result.IsTcpNextMessageWaiting(false);
bool isSucessfullFinished = true;
while (isTcpNextMessageWaiting)
{
resultData = QueryByTcp(responderAddress, null, 0, ref tcpClient, ref tcpStream, out responderAddress);
if (resultData != null)
{
TMessage tcpResult;
try
{
tcpResult = DnsMessageBase.Parse <TMessage>(resultData, tsigKeySelector, tsigOriginalMac);
}
catch (Exception e)
{
Trace.TraceError("Error on dns query: " + e);
isSucessfullFinished = false;
break;
}
if (tcpResult.ReturnCode == ReturnCode.ServerFailure)
{
isSucessfullFinished = false;
break;
}
else
{
result.AnswerRecords.AddRange(tcpResult.AnswerRecords);
isTcpNextMessageWaiting = tcpResult.IsTcpNextMessageWaiting(true);
}
}
else
{
isSucessfullFinished = false;
break;
}
}
if (isSucessfullFinished)
{
return(result);
}
}
}
finally
{
try
{
if (tcpStream != null)
{
tcpStream.Dispose();
}
if (tcpClient != null)
{
tcpClient.Close();
}
}
catch { }
}
}
return(null);
}
internal void Encode(byte[] messageData, int offset, ref int currentPosition, Dictionary <string, ushort> domainNames)
{
DnsMessageBase.EncodeDomainName(messageData, offset, ref currentPosition, Name, true, domainNames);
DnsMessageBase.EncodeUShort(messageData, ref currentPosition, (ushort)RecordType);
DnsMessageBase.EncodeUShort(messageData, ref currentPosition, (ushort)RecordClass);
}