public static Message Read(PacketReader reader)
{
Message result = new Message();
result.TransactionId = reader.ReadUShort();
result.Flags = new MessageFlags(reader.ReadUShort());
ushort questions = reader.ReadUShort();
ushort answers = reader.ReadUShort();
ushort authorityRecords = reader.ReadUShort();
ushort additionalRecords = reader.ReadUShort();
for (int i = 0; i < questions; ++i)
{
result.Questions.Add(Question.ReadFrom(reader));
}
for (int i = 0; i < answers; ++i)
{
result.Answers.Add(ResourceRecord.ReadFrom(reader));
}
for (int i = 0; i < authorityRecords; ++i)
{
result.AuthorityRecords.Add(ResourceRecord.ReadFrom(reader));
}
for (int i = 0; i < additionalRecords; ++i)
{
result.AdditionalRecords.Add(ResourceRecord.ReadFrom(reader));
}
return result;
}
private ResourceRecord[] QueryNetwork(string name, RecordType type)
{
ushort transactionId = _nextTransId++;
string normName = NormalizeDomainName(name);
Transaction transaction = new Transaction();
try
{
lock (_transactions)
{
_transactions.Add(transactionId, transaction);
}
PacketWriter writer = new PacketWriter(1800);
Message msg = new Message();
msg.TransactionId = transactionId;
msg.Flags = new MessageFlags(false, OpCode.Query, false, false, false, false, ResponseCode.Success);
msg.Questions.Add(new Question() { Name = normName, Type = type, Class = RecordClass.Internet });
msg.WriteTo(writer);
byte[] msgBytes = writer.GetBytes();
IPEndPoint mDnsAddress = new IPEndPoint(IPAddress.Parse("224.0.0.251"), 5353);
lock (_udpClient)
{
_udpClient.Send(msgBytes, msgBytes.Length, mDnsAddress);
}
transaction.CompleteEvent.WaitOne(2000);
}
finally
{
lock (_transactions)
{
_transactions.Remove(transactionId);
}
}
return transaction.Answers.ToArray();
}
/// <summary>
/// Looks up a record in DNS.
/// </summary>
/// <param name="name">The name to lookup</param>
/// <param name="type">The type of record requested</param>
/// <returns>The records returned by the DNS server, if any</returns>
public override ResourceRecord[] Lookup(string name, RecordType type)
{
ushort transactionId = _nextTransId++;
string normName = NormalizeDomainName(name);
using (UdpClient udpClient = new UdpClient(0))
{
IAsyncResult result = udpClient.BeginReceive(null, null);
PacketWriter writer = new PacketWriter(1800);
Message msg = new Message();
msg.TransactionId = transactionId;
msg.Flags = new MessageFlags(false, OpCode.Query, false, false, false, false, ResponseCode.Success);
msg.Questions.Add(new Question() { Name = normName, Type = type, Class = RecordClass.Internet });
msg.WriteTo(writer);
byte[] msgBytes = writer.GetBytes();
foreach (var server in _servers)
{
udpClient.Send(msgBytes, msgBytes.Length, server);
}
for (int i = 0; i < maxRetries; ++i)
{
DateTime now = DateTime.UtcNow;
while (result.AsyncWaitHandle.WaitOne(Math.Max(responseTimeout - (DateTime.UtcNow - now).Milliseconds, 0)))
{
try
{
IPEndPoint sourceEndPoint = null;
byte[] packetBytes = udpClient.EndReceive(result, ref sourceEndPoint);
PacketReader reader = new PacketReader(packetBytes);
Message response = Message.Read(reader);
if (response.TransactionId == transactionId)
{
return response.Answers.ToArray();
}
}
catch
{
// Do nothing - bad packet (probably...)
}
}
}
}
return null;
}
