/// <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)
{
//--- Try to get MX records from cache
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>
/// 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 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);
}