public static byte[] CreatePacket(DnsPacket packet)
{
var result = new List <byte>();
var queryBytes = BitConverter.GetBytes(packet.QueryId);
Array.Reverse(queryBytes);
result.AddRange(queryBytes);
var flags = DnsFlags.CreateFlags(packet.Flags);
var flagsByte = BitConverter.GetBytes(flags);
Array.Reverse(flagsByte);
result.AddRange(flagsByte);
var questionsCount = BitConverter.GetBytes((short)packet.Queries.Count);
Array.Reverse(questionsCount);
result.AddRange(questionsCount);
var answersCount = BitConverter.GetBytes((short)packet.Answers.Count);
Array.Reverse(answersCount);
result.AddRange(answersCount);
var authoritativeCount = BitConverter.GetBytes((short)packet.AuthorityAnswers.Count);
Array.Reverse(authoritativeCount);
result.AddRange(authoritativeCount);
var additionalCount = BitConverter.GetBytes((short)packet.AdditionalAnswers.Count);
Array.Reverse(additionalCount);
result.AddRange(additionalCount);
var nameCache = new Dictionary <string, int>();
foreach (var query in packet.Queries)
{
result.AddRange(CreateQuery(query, result.Count, nameCache));
}
foreach (var answer in packet.Answers)
{
result.AddRange(CreateAnswer(answer, result.Count, nameCache));
}
foreach (var answer in packet.AuthorityAnswers)
{
result.AddRange(CreateAnswer(answer, result.Count, nameCache));
}
foreach (var answer in packet.AdditionalAnswers)
{
result.AddRange(CreateAnswer(answer, result.Count, nameCache));
}
return(result.ToArray());
}
public static DnsPacket ParsePacket(byte[] packet)
{
using (var stream = new MemoryStream(packet))
{
using (var reader = new BigEndianBinaryReader(stream, Encoding.BigEndianUnicode))
{
var id = reader.ReadUInt16();
var flagsByte = reader.ReadUInt16();
var flags = DnsFlags.ParseFlags(flagsByte);
var questionsCount = reader.ReadUInt16();
var answersCount = reader.ReadUInt16();
var authorityAnswersCount = reader.ReadUInt16();
var additionalAnswersCount = reader.ReadUInt16();
var nameCache = new Dictionary <int, byte[]>();
var questions = new List <DnsQuery>();
var answers = new List <DnsAnswer>();
var additionalAnswers = new List <DnsAnswer>();
var authoritativeAnswers = new List <DnsAnswer>();
for (var i = 0; i < questionsCount; i++)
{
questions.Add(ParseQuery(reader, packet, (int)reader.BaseStream.Position, nameCache));
}
for (var i = 0; i < answersCount; i++)
{
answers.Add(ParseAnswer(reader, packet, (int)reader.BaseStream.Position, nameCache));
}
for (var i = 0; i < authorityAnswersCount; i++)
{
authoritativeAnswers.Add(
ParseAnswer(reader, packet, (int)reader.BaseStream.Position, nameCache));
}
for (var i = 0; i < additionalAnswersCount; i++)
{
additionalAnswers.Add(ParseAnswer(reader, packet, (int)reader.BaseStream.Position, nameCache));
}
var result = new DnsPacket
{
QueryId = id,
Flags = flags,
Queries = questions,
Answers = answers,
AuthorityAnswers = authoritativeAnswers,
AdditionalAnswers = additionalAnswers
};
return(result);
}
}
}
public static DnsPacket CreateSimpleErrorPacket(DnsQuery query, ushort queryId, byte replyCode)
{
var flags = new DnsFlags
{
RecursionDesired = true,
RecursionAvailable = true,
ReplyCode = replyCode
};
var packet = new DnsPacket
{
QueryId = queryId,
Flags = flags,
Queries = new List <DnsQuery> {
query
},
Answers = new List <DnsAnswer>(),
AdditionalAnswers = new List <DnsAnswer>(),
AuthorityAnswers = new List <DnsAnswer>()
};
return(packet);
}
