public static NameServerAddress[] GetNameServersFromResponse(DnsDatagram response, bool preferIPv6)
{
List <NameServerAddress> nameServers = new List <NameServerAddress>(response.Authority.Length);
DnsResourceRecord[] authorityRecords;
if ((response.Question.Length > 0) && (response.Question[0].Type == DnsResourceRecordType.NS) && (response.Answer.Length > 0))
{
authorityRecords = response.Answer;
}
else
{
authorityRecords = response.Authority;
}
foreach (DnsResourceRecord authorityRecord in authorityRecords)
{
if (authorityRecord.Type == DnsResourceRecordType.NS)
{
DnsNSRecord nsRecord = (DnsNSRecord)authorityRecord.RDATA;
IPEndPoint endPoint = null;
//find ip address of authoritative name server from additional records
foreach (DnsResourceRecord rr in response.Additional)
{
if (nsRecord.NSDomainName.Equals(rr.Name, StringComparison.OrdinalIgnoreCase))
{
switch (rr.Type)
{
case DnsResourceRecordType.A:
endPoint = new IPEndPoint(((DnsARecord)rr.RDATA).Address, 53);
nameServers.Add(new NameServerAddress(nsRecord.NSDomainName, endPoint));
break;
case DnsResourceRecordType.AAAA:
endPoint = new IPEndPoint(((DnsAAAARecord)rr.RDATA).Address, 53);
if (preferIPv6)
{
nameServers.Add(new NameServerAddress(nsRecord.NSDomainName, endPoint));
}
break;
}
}
}
if (endPoint == null)
{
nameServers.Add(new NameServerAddress(new DomainEndPoint(nsRecord.NSDomainName, 53)));
}
}
}
NameServerAddress[] nsArray = nameServers.ToArray();
DnsClient.ShuffleArray(nsArray);
if (preferIPv6)
{
Array.Sort(nsArray);
}
return(nsArray);
}