public static DnsQuery ReadDnsQuery(BinaryReader reader)
{
String domainName = ReadDomainName(reader);
QueryType qtype = (QueryType)ReadUInt16BE(reader);
QueryClass qclass = (QueryClass)ReadUInt16BE(reader);
DnsQuery query = new DnsQuery(domainName, qtype, qclass);
return(query);
}
/// <summary>
/// Get IPHostEntry for given domainName.
/// </summary>
/// <param name="domainName">domainName</param>
/// <param name="queryType">QueryType.Address or QueryType.MailExchange</param>
/// <param name="dnsServer">dnsServer</param>
/// <returns></returns>
public static IPHostEntry GetIPHostEntry(string domainName, QueryType queryType, IPAddress dnsServer)
{
DnsMessage message = DnsMessage.StandardQuery();
DnsQuery query = new DnsQuery(domainName, queryType);
message.Querys.Add(query);
byte[] msgData = DnsMessageCoder.EncodeDnsMessage(message);
try
{
byte[] reply = QueryServer(msgData, dnsServer);
if (reply != null)
{
DnsMessage answer = DnsMessageCoder.DecodeDnsMessage(reply);
if (answer.ID == message.ID)
{
if (answer.Answers.Count > 0)
{
IPHostEntry host = new IPHostEntry();
host.HostName = domainName;
if (queryType == QueryType.Address)
{
host.AddressList = GetAddressList(domainName, answer);
}
else if (queryType == QueryType.MailExchange)
{
host.Aliases = GetMailExchangeAliases(domainName, answer);
host.AddressList = GetAddressList(answer, new List <string>(host.Aliases));
}
return(host);
}
else if (answer.AuthorityRecords.Count > 0)
{
IPAddress[] serverAddresses = GetAuthorityServers(answer);
// depth first search
foreach (IPAddress serverIP in serverAddresses)
{
IPHostEntry host = GetIPHostEntry(domainName, queryType, serverIP);
if (host != null)
{
return(host);
}
}
}
}
}
}
catch { }
return(null);
}
/* 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.
*/
public static byte[] EncodeDnsQuery(DnsQuery query)
{
MemoryStream stream = new MemoryStream(256);
BinaryWriter writer = new BinaryWriter(stream);
//QNAME
string[] labels = query.DomainName.Split('.');
foreach (string label in labels)
{
writer.Write((byte)label.Length);
writer.Write(Encoding.ASCII.GetBytes(label));
}
writer.Write((byte)0);
//QTYPE
WriteUInt16BE(writer, (UInt16)query.QueryType);
//QCLASS
WriteUInt16BE(writer, (UInt16)query.QueryClass);
return(stream.ToArray());
}