public static byte[] CreateAnswer(DnsAnswer answer, int position, Dictionary <string, int> cache)
{
var result = new List <byte>();
var encodedDomain = EncodeDomain(answer.Name, position, cache, false);
result.AddRange(encodedDomain);
var type = (short)answer.AnswerType;
var typeBytes = BitConverter.GetBytes(type);
Array.Reverse(typeBytes);
result.AddRange(typeBytes);
var classValue = (short)answer.Class;
var classBytes = BitConverter.GetBytes(classValue);
Array.Reverse(classBytes);
result.AddRange(classBytes);
var ttlBytes = BitConverter.GetBytes(answer.TTL);
Array.Reverse(ttlBytes);
result.AddRange(ttlBytes);
byte[] dataBytes;
if (answer.AnswerType == AnswerType.A)
{
dataBytes = IPAddress.Parse(answer.Data).GetAddressBytes();
}
else if (answer.AnswerType == AnswerType.NS)
{
dataBytes = EncodeDomain(answer.Data, position + result.Count, cache, true);
}
else
{
dataBytes = new byte[0];
}
var length = (ushort)dataBytes.Length;
var lengthBytes = BitConverter.GetBytes(length);
Array.Reverse(lengthBytes);
result.AddRange(lengthBytes);
result.AddRange(dataBytes);
return(result.ToArray());
}
private static DnsAnswer ParseAnswer(BinaryReader reader, byte[] packet, int position,
Dictionary <int, byte[]> nameCache)
{
var(domain, shift) = ParseDomain(packet, position, nameCache);
var _ = reader.BaseStream.Seek(shift, SeekOrigin.Begin);
var type = (AnswerType)reader.ReadUInt16();
var queryClass = (Class)reader.ReadUInt16();
var ttl = reader.ReadUInt32();
var dataLength = reader.ReadUInt16();
var data = "";
if (type == AnswerType.A)
{
var dataArray = new List <byte>();
for (var i = 0; i < dataLength; i++)
{
dataArray.Add(reader.ReadByte());
}
data = string.Join(".", dataArray.Select(item => item.ToString()));
}
else if (type == AnswerType.NS)
{
var(name, nsShift) = ParseDomain(packet, (int)reader.BaseStream.Position, nameCache);
var __ = reader.BaseStream.Seek(nsShift, SeekOrigin.Begin);
data = name;
}
else if (type == AnswerType.SOA)
{
data = "";
}
var answer = new DnsAnswer
{
Class = queryClass,
AnswerType = type,
Name = domain,
TTL = ttl,
Data = data
};
return(answer);
}
