/// <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 = new MX_Record[0];
//--- 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 MX records from answer collection and ORDERS them by preference.
/// NOTE: Duplicate preference records are appended to end.
/// </summary>
/// <returns></returns>
internal MX_Record[] GetMxRecordsFromAnswers()
{
MX_Record[] _result = null;
try
{
SortedList mx = new SortedList();
ArrayList duplicateList = new ArrayList();
foreach (Dns_Answer answer in m_Answers)
{
if (answer.QTYPE == QTYPE.MX)
{
MX_Record mxRec = (MX_Record)answer.RecordObj;
if (mx.Contains(mxRec.Preference) == false)
{
mx.Add(mxRec.Preference, mxRec);
}
else
{
duplicateList.Add(mxRec);
}
}
}
MX_Record[] mxBuff = new MX_Record[mx.Count + duplicateList.Count];
mx.Values.CopyTo(mxBuff, 0);
duplicateList.CopyTo(mxBuff, mx.Count);
_result = mxBuff;
}
catch
{
}
return(_result);
}