/// <summary>
/// Parses answer.
/// </summary>
/// <param name="reply"></param>
/// <param name="queryID"></param>
/// <returns>Returns true if answer parsed successfully.</returns>
internal bool ParseAnswers(byte[] reply,int queryID)
{
try
{
/*
1 1 1 1 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| |
/ /
/ NAME /
| |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| TYPE |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| CLASS |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| TTL |
| |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| RDLENGTH |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
/ RDATA /
/ /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
*/
//------- Parse result -----------------------------------//
Dns_Header replyHeader = new Dns_Header();
if(!replyHeader.ParseHeader(reply)){
return false;
}
// Check that it's query what we want
if(queryID != replyHeader.ID){
return false;
}
int pos = 12;
//----- Parse question part ------------//
for(int q=0;q<replyHeader.QDCOUNT;q++){
string dummy = "";
GetQName(reply,ref pos,ref dummy);
//qtype + qclass
pos += 4;
}
//--------------------------------------//
ArrayList answers = new ArrayList();
//---- Start parsing aswers ------------------------------------------------------------------//
for(int i=0;i<replyHeader.ANCOUNT;i++){
string name = "";
if(!GetQName(reply,ref pos,ref name)){
return false;
}
int type = reply[pos++] << 8 | reply[pos++];
int rdClass = reply[pos++] << 8 | reply[pos++];
int ttl = reply[pos++] << 24 | reply[pos++] << 16 | reply[pos++] << 8 | reply[pos++];
int rdLength = reply[pos++] << 8 | reply[pos++];
object answerObj = null;
switch((QTYPE)type)
{
case QTYPE.MX:
answerObj = ParseMxRecord(reply,ref pos);
break;
default:
answerObj = "sgas"; // Dummy place holder for now
pos += rdLength;
break;
}
// Add answer to answer list
if(answerObj != null){
answers.Add(new Dns_Answer(name,(QTYPE)type,rdClass,ttl,rdLength,answerObj));
}
else{
return false; // Parse failed
}
}
//-------------------------------------------------------------------------------------------//
if(answers.Count > 0){
m_Answers = new Dns_Answer[answers.Count];
answers.CopyTo(m_Answers);
}
return true;
}
catch{
return false;
}
}
/// <summary>
/// Gets MX records.(MX records are sorted by preference, lower array element is prefered)
/// </summary>
/// <param name="domain"></param>
/// <param name="mxRecords"></param>
/// <returns></returns>
public DnsReplyCode GetMXRecords(string domain,out MX_Record[] mxRecords)
{
mxRecords = null;
//--- Try to get MX records from cache
if(m_UseDnsCache){
mxRecords = DnsCache.GetMXFromCache(domain);
if(mxRecords != null){
// Console.WriteLine("domain:" + domain + " from cahce.");
return DnsReplyCode.Ok;
}
}
//------------------------------------//
Dns_Header header = new Dns_Header(DnsEx.ID,OPCODE.IQUERY);
Dns_Query query = new Dns_Query(domain,QTYPE.MX,1);
byte[] bQuery = query.GetQuery(header);
byte[] reply = GetQuery(bQuery,header.ID);
if(reply != null){
Dns_Answers answers = new Dns_Answers();
if(answers.ParseAnswers(reply,header.ID)){
mxRecords = answers.GetMxRecordsFromAnswers();
if(mxRecords != null){
// Add to cache
DnsCache.AddMXToCache(domain,mxRecords);
return DnsReplyCode.Ok;
}
else{
return DnsReplyCode.NoEntries;
}
}
}
return DnsReplyCode.TempError;
}
/// <summary>
/// Gets query.
/// </summary>
/// <param name="header"></param>
/// <returns></returns>
public byte[] GetQuery(Dns_Header header)
{
byte[] query = null;
try
{
/* 4.1.2. Question section format
1 1 1 1 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| |
/ QNAME /
/ /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| QTYPE |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| QCLASS |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
QNAME
a domain name represented as a sequence of labels, where
each label consists of a length octet followed by that
number of octets. The domain name terminates with the
zero length octet for the null label of the root. Note
that this field may be an odd number of octets; no
padding is used.
*/
query = new byte[521];
// Copy dns header to query
byte[] head = header.GetHeader();
head.CopyTo(query,0);
//--------- Query part ------------------------------------//
string[] labels = m_QNAME.Split(new char[] {'.'});
int position = 12;
// Copy all domain parts(labels) to query
// eg. lumisoft.ee = 2 labels, lumisoft and ee.
// format = label.length + label(bytes)
foreach(string label in labels){
// add label lenght to query
query[position++] = (byte)(label.Length);
// convert label string to byte array
byte[] b = Encoding.ASCII.GetBytes(label.ToCharArray());
b.CopyTo(query,position);
// Move position by label length
position += b.Length;
}
// Terminate domain (see note above)
query[position++] = (byte) 0;
// Set QTYPE
query[position++] = (byte) 0;
query[position++] = (byte)m_QTYPE;
// Set QCLASS
query[position++] = (byte) 0;
query[position++] = (byte)m_QCALSS;
//-------------------------------------------------------//
}
catch
{
query = null;
}
return query;
}
