public DnsResponseMessage GetResponseMessage(ArraySegment <byte> responseData)
{
var reader = new DnsDatagramReader(responseData);
var id = reader.ReadUInt16NetworkOrder();
var flags = reader.ReadUInt16NetworkOrder();
var questionCount = reader.ReadUInt16NetworkOrder();
var answerCount = reader.ReadUInt16NetworkOrder();
var nameServerCount = reader.ReadUInt16NetworkOrder();
var additionalCount = reader.ReadUInt16NetworkOrder();
var header = new DnsResponseHeader(id, flags, questionCount, answerCount, additionalCount, nameServerCount);
var response = new DnsResponseMessage(header, responseData.Count);
for (var questionIndex = 0; questionIndex < questionCount; questionIndex++)
{
var questionQueryString = reader.ReadQuestionQueryString();
var queryTypeValue = reader.ReadUInt16NetworkOrder();
var queryClass = reader.ReadUInt16NetworkOrder();
if (!_queryTypes.TryGetValue(queryTypeValue, out var queryType))
{
queryType = new PseudoResourceRecordType(
abbreviation: "Unknown",
value: queryTypeValue
);
}
var question = new DnsQuestion(questionQueryString, queryType, (QueryClass)queryClass);
response.AddQuestion(question);
}
for (var answerIndex = 0; answerIndex < answerCount; answerIndex++)
{
var info = ReadRecordInfo(reader);
var record = _dnsRecordFactory.GetRecord(info, reader);
response.AddAnswer(record);
}
for (var serverIndex = 0; serverIndex < nameServerCount; serverIndex++)
{
var info = ReadRecordInfo(reader);
var record = _dnsRecordFactory.GetRecord(info, reader);
response.AddAuthority(record);
}
for (var additionalIndex = 0; additionalIndex < additionalCount; additionalIndex++)
{
var info = ReadRecordInfo(reader);
var record = _dnsRecordFactory.GetRecord(info, reader);
response.AddAdditional(record);
}
return(response);
}
public ICollection <ArraySegment <byte> > ReadLabels()
{
var result = new List <ArraySegment <byte> >(10);
// read the length byte for the label, then get the content from offset+1 to length
// proceed till we reach zero length byte.
byte length;
while ((length = ReadByte()) != 0)
{
// respect the reference bit and lookup the name at the given position
// the reader will advance only for the 2 bytes read.
if ((length & ReferenceByte) != 0)
{
int subIndex = (length & 0x3f) << 8 | ReadByte();
if (subIndex >= _data.Array.Length - 1)
{
// invalid length pointer, seems to be actual length of a label which exceeds 63 chars...
// get back one and continue other labels
_index--;
result.Add(_data.SubArray(_index, length));
Advance(length);
continue;
}
var subReader = new DnsDatagramReader(_data.SubArrayFromOriginal(subIndex));
var newLabels = subReader.ReadLabels();
result.AddRange(newLabels); // add range actually much faster than concat and equal to or faster than for-each.. (array copy would work maybe)
return(result);
}
if (_index + length >= _count)
{
throw new DnsResponseParseException(
"Found invalid label position.", _data.ToArray(), _index, length);
}
var label = _data.SubArray(_index, length);
// maybe store original bytes in this instance too?
result.Add(label);
Advance(length);
}
return(result);
}
public virtual DnsResponseMessage GetResponseMessage(ArraySegment <byte> responseData)
{
var reader = new DnsDatagramReader(responseData);
var factory = new DnsRecordFactory(reader);
var id = reader.ReadUInt16NetworkOrder();
var flags = reader.ReadUInt16NetworkOrder();
var questionCount = reader.ReadUInt16NetworkOrder();
var answerCount = reader.ReadUInt16NetworkOrder();
var nameServerCount = reader.ReadUInt16NetworkOrder();
var additionalCount = reader.ReadUInt16NetworkOrder();
var header = new DnsResponseHeader(id, flags, questionCount, answerCount, additionalCount, nameServerCount);
var response = new DnsResponseMessage(header, responseData.Count);
for (int questionIndex = 0; questionIndex < questionCount; questionIndex++)
{
var question = new DnsQuestion(reader.ReadQuestionQueryString(), (QueryType)reader.ReadUInt16NetworkOrder(), (QueryClass)reader.ReadUInt16NetworkOrder());
response.AddQuestion(question);
}
for (int answerIndex = 0; answerIndex < answerCount; answerIndex++)
{
var info = factory.ReadRecordInfo();
var record = factory.GetRecord(info);
response.AddAnswer(record);
}
for (int serverIndex = 0; serverIndex < nameServerCount; serverIndex++)
{
var info = factory.ReadRecordInfo();
var record = factory.GetRecord(info);
response.AddAuthority(record);
}
for (int additionalIndex = 0; additionalIndex < additionalCount; additionalIndex++)
{
var info = factory.ReadRecordInfo();
var record = factory.GetRecord(info);
response.AddAdditional(record);
}
return(response);
}
private DnsResourceRecord ResolveTXTRecord(ResourceRecordInfo info)
{
int pos = _reader.Index;
var values = new List <string>();
var utf8Values = new List <string>();
while ((_reader.Index - pos) < info.RawDataLength)
{
var length = _reader.ReadByte();
var bytes = _reader.ReadBytes(length);
var escaped = DnsDatagramReader.ParseString(bytes);
var utf = DnsDatagramReader.ReadUTF8String(bytes);
values.Add(escaped);
utf8Values.Add(utf);
}
return(new TxtRecord(info, values.ToArray(), utf8Values.ToArray()));
}
public static string ParseString(DnsDatagramReader reader, int length)
{
if (reader._count < reader._index + length)
{
throw new DnsResponseParseException("Cannot parse string.", reader._data.ToArray(), reader._index, length);
}
var builder = StringBuilderObjectPool.Default.Get();
for (var i = 0; i < length; i++)
{
byte b = reader.ReadByte();
char c = (char)b;
if (b < 32 || b > 126)
{
builder.Append("\\" + b.ToString("000"));
}
else if (c == ';')
{
builder.Append("\\;");
}
else if (c == '\\')
{
builder.Append("\\\\");
}
else if (c == '"')
{
builder.Append("\\\"");
}
else
{
builder.Append(c);
}
}
var value = builder.ToString();
StringBuilderObjectPool.Default.Return(builder);
return(value);
}
/// <summary>
/// Reads a <see cref="ResourceRecord"/> from this <see cref="DnsDatagramReader"/>.
/// </summary>
private ResourceRecord ReadRecordInfo(DnsDatagramReader reader)
{
var queryString = reader.ReadQuestionQueryString();
var type = reader.ReadUInt16NetworkOrder();
if (!_resourceRecordTypes.TryGetValue(type, out var resourceRecordType))
{
resourceRecordType = new PseudoResourceRecordType(
abbreviation: "Unknown - machine generated",
value: type
);
}
var queryClass = reader.ReadUInt16NetworkOrder();
var ttl = reader.ReadUInt32NetworkOrder();
var rdLength = reader.ReadUInt16NetworkOrder();
return(new ResourceRecord(
queryString, // name
resourceRecordType, // type
(QueryClass)queryClass, // class
(int)ttl, // ttl - 32bit!!
rdLength)); // RDLength
}
public static string ParseString(DnsDatagramReader reader, int length)
{
var builder = StringBuilderObjectPool.Default.Get();
for (var i = 0; i < length; i++)
{
byte b = reader.ReadByte();
char c = (char)b;
if (b < 32 || b > 126)
{
builder.Append("\\" + b.ToString("000"));
}
else if (c == ';')
{
builder.Append("\\;");
}
else if (c == '\\')
{
builder.Append("\\\\");
}
else if (c == '"')
{
builder.Append("\\\"");
}
else
{
builder.Append(c);
}
}
var value = builder.ToString();
StringBuilderObjectPool.Default.Return(builder);
return(value);
}
public DnsRecordFactory(DnsDatagramReader reader)
{
_reader = reader ?? throw new ArgumentNullException(nameof(reader));
}
