private static async Task ResolveNameServerAddressesAsync(DnsServer dnsServer, string nsDomain, int port, DnsTransportProtocol protocol, List <NameServerAddress> outNameServers)
{
try
{
DnsDatagram response = await dnsServer.DirectQueryAsync(new DnsQuestionRecord(nsDomain, DnsResourceRecordType.A, DnsClass.IN));
if (response.Answer.Count > 0)
{
IReadOnlyList <IPAddress> addresses = DnsClient.ParseResponseA(response);
foreach (IPAddress address in addresses)
{
outNameServers.Add(new NameServerAddress(nsDomain, new IPEndPoint(address, port), protocol));
}
}
}
catch
{ }
if (dnsServer.PreferIPv6)
{
try
{
DnsDatagram response = await dnsServer.DirectQueryAsync(new DnsQuestionRecord(nsDomain, DnsResourceRecordType.AAAA, DnsClass.IN));
if (response.Answer.Count > 0)
{
IReadOnlyList <IPAddress> addresses = DnsClient.ParseResponseAAAA(response);
foreach (IPAddress address in addresses)
{
outNameServers.Add(new NameServerAddress(nsDomain, new IPEndPoint(address, port), protocol));
}
}
}
catch
{ }
}
}
private static async Task <IReadOnlyList <NameServerAddress> > GetNameServerAddressesAsync(DnsServer dnsServer, DnsResourceRecord record)
{
string nsDomain;
switch (record.Type)
{
case DnsResourceRecordType.NS:
nsDomain = (record.RDATA as DnsNSRecord).NameServer;
break;
case DnsResourceRecordType.SOA:
nsDomain = (record.RDATA as DnsSOARecord).PrimaryNameServer;
break;
default:
throw new InvalidOperationException();
}
List <NameServerAddress> nameServers = new List <NameServerAddress>(2);
IReadOnlyList <DnsResourceRecord> glueRecords = record.GetGlueRecords();
if (glueRecords.Count > 0)
{
foreach (DnsResourceRecord glueRecord in glueRecords)
{
switch (glueRecord.Type)
{
case DnsResourceRecordType.A:
nameServers.Add(new NameServerAddress(nsDomain, (glueRecord.RDATA as DnsARecord).Address));
break;
case DnsResourceRecordType.AAAA:
if (dnsServer.PreferIPv6)
{
nameServers.Add(new NameServerAddress(nsDomain, (glueRecord.RDATA as DnsAAAARecord).Address));
}
break;
}
}
}
else
{
//resolve addresses
try
{
DnsDatagram response = await dnsServer.DirectQueryAsync(new DnsQuestionRecord(nsDomain, DnsResourceRecordType.A, DnsClass.IN));
if ((response != null) && (response.Answer.Count > 0))
{
IReadOnlyList <IPAddress> addresses = DnsClient.ParseResponseA(response);
foreach (IPAddress address in addresses)
{
nameServers.Add(new NameServerAddress(nsDomain, address));
}
}
}
catch
{ }
if (dnsServer.PreferIPv6)
{
try
{
DnsDatagram response = await dnsServer.DirectQueryAsync(new DnsQuestionRecord(nsDomain, DnsResourceRecordType.AAAA, DnsClass.IN));
if ((response != null) && (response.Answer.Count > 0))
{
IReadOnlyList <IPAddress> addresses = DnsClient.ParseResponseAAAA(response);
foreach (IPAddress address in addresses)
{
nameServers.Add(new NameServerAddress(nsDomain, address));
}
}
}
catch
{ }
}
}
return(nameServers);
}