/// <summary>
/// Initializes a new instance of the <b>DnsClientWithCacheFacts</b> class.
/// </summary>
public DnsClientWithCacheFacts()
: base(DumpIsEnabled)
{
m_cache = new DnsResponseCache(Guid.NewGuid().ToString("D"));
m_client = new DnsClientWithCache(PublicDns)
{
Timeout = TimeSpan.FromSeconds(5), Cache = m_cache
};
m_client.MaxRetries = 1;
m_clientNoCache = new DnsClient(PublicDns)
{
Timeout = TimeSpan.FromSeconds(5)
};
m_clientNoCache.MaxRetries = 1;
}
private IEnumerable <IPAddress> GetNameServers(string domain)
{
IEnumerable <IPAddress> nameServers = null;
foreach (IPEndPoint endpoint in m_primaryDnsServers)
{
DnsClient client = null;
try
{
if (m_doCache)
{
client = new DnsClientWithCache(endpoint);
}
else
{
client = new DnsClient(endpoint);
}
client.Timeout = Timeout;
nameServers = client.GetNameServers(domain);
if (nameServers == null)
{
continue;
}
foreach (IPAddress nameServer in nameServers)
{
if (nameServer != IPAddress.None)
{
return(nameServers);
}
}
}
finally
{
if (client != null)
{
client.Dispose();
}
}
}
return(null);
}
DnsResponse ProcessRequest(DnsRequest request)
{
IEnumerable <IPAddress> nameServers = GetNameServers(request.Question.Domain);
if (nameServers == null)
{
throw new DnsServerException(DnsStandard.ResponseCode.NameError);
}
bool useUdp = request.Question.Type == DnsStandard.RecordType.CERT ? false : true;
int count = 0;
DnsResponse response = null;
foreach (IPAddress nameserver in nameServers)
{
DnsClient client = null;
try
{
if (m_doCache)
{
client = new DnsClientWithCache(new IPEndPoint(nameserver, m_dnsResolutionPort));
}
else
{
client = new DnsClient(new IPEndPoint(nameserver, m_dnsResolutionPort));
}
client.Timeout = Timeout;
client.UseUDPFirst = useUdp;
DnsRequest newRequest = new DnsRequest(new DnsQuestion(request.Question));
response = client.Resolve(newRequest);
if (response != null)
{
// Clone the response before returning it since the response may be cached
// and we don't want the cached response to be modified.
response = response.Clone();
// updates the TTL of records to reflect the elapsed time since the
// record was cached.
response.UpdateRecordsTTL();
break;
}
}
catch (DnsException)
{
continue;
}
finally
{
if (client != null)
{
client.Dispose();
}
}
count++;
if (count > m_maxNameServersToAttempt)
{
break;
}
}
if (response == null)
{
throw new DnsServerException(DnsStandard.ResponseCode.ServerFailure);
}
response.RequestID = request.RequestID;
return(response);
}
