/// <summary>
/// Gets specified host IP addresses(A and AAAA).
/// </summary>
/// <param name="host">Host name.</param>
/// <returns>Returns specified host IP addresses.</returns>
/// <exception cref="ArgumentNullException">Is raised when <b>host</b> is null reference.</exception>
public IPAddress[] GetHostAddresses(string host)
{
if (host == null)
{
throw new ArgumentNullException("host");
}
List <IPAddress> retVal = new List <IPAddress>();
// This is probably NetBios name
if (host.IndexOf(".") == -1)
{
return(Dns.GetHostEntry(host).AddressList);
}
else
{
DnsServerResponse response = Query(host, QTYPE.A);
if (response.ResponseCode != RCODE.NO_ERROR)
{
throw new DNS_ClientException(response.ResponseCode);
}
foreach (DNS_rr_A record in response.GetARecords())
{
retVal.Add(record.IP);
}
response = Query(host, QTYPE.AAAA);
if (response.ResponseCode != RCODE.NO_ERROR)
{
throw new DNS_ClientException(response.ResponseCode);
}
foreach (DNS_rr_A record in response.GetARecords())
{
retVal.Add(record.IP);
}
}
return(retVal.ToArray());
}
/// <summary>
/// Resolves host name to IP addresses.
/// </summary>
/// <param name="host">Host name or IP address.</param>
/// <returns>Return specified host IP addresses.</returns>
/// <exception cref="ArgumentNullException">Is raised when <b>host</b> is null.</exception>
public static IPAddress[] Resolve(string host)
{
if (host == null)
{
throw new ArgumentNullException("host");
}
// If hostName_IP is IP
try
{
return(new[] { IPAddress.Parse(host) });
}
catch {}
// This is probably NetBios name
if (host.IndexOf(".") == -1)
{
return(Dns.GetHostEntry(host).AddressList);
}
else
{
// hostName_IP must be host name, try to resolve it's IP
Dns_Client dns = new Dns_Client();
DnsServerResponse resp = dns.Query(host, QTYPE.A);
if (resp.ResponseCode == RCODE.NO_ERROR)
{
DNS_rr_A[] records = resp.GetARecords();
IPAddress[] retVal = new IPAddress[records.Length];
for (int i = 0; i < records.Length; i++)
{
retVal[i] = records[i].IP;
}
return(retVal);
}
else
{
throw new Exception(resp.ResponseCode.ToString());
}
}
}
/// <summary>
/// Adds dns records to cache. If old entry exists, it is replaced.
/// </summary>
/// <param name="qname"></param>
/// <param name="qtype"></param>
/// <param name="answers"></param>
public static void AddToCache(string qname, int qtype, DnsServerResponse answers)
{
if (answers == null)
{
return;
}
try
{
lock (m_pCache)
{
// Remove old cache entry, if any.
if (m_pCache.Contains(qname + qtype))
{
m_pCache.Remove(qname + qtype);
}
m_pCache.Add(qname + qtype, new DnsCacheEntry(answers, DateTime.Now));
}
}
catch {}
}
/// <summary>
/// Default constructor.
/// </summary>
/// <param name="answers">Dns answers.</param>
/// <param name="addTime">Entry add time.</param>
public DnsCacheEntry(DnsServerResponse answers, DateTime addTime)
{
m_pResponse = answers;
m_Time = addTime;
}
/// <summary>
/// Sends query to server.
/// </summary>
/// <param name="timeout">Query timeout in milli seconds.</param>
/// <param name="qname">Query text.</param>
/// <param name="qtype">Query type.</param>
/// <param name="qclass">Query class.</param>
/// <returns></returns>
private DnsServerResponse QueryServer(int timeout, string qname, QTYPE qtype, int qclass)
{
if (m_DnsServers == null || m_DnsServers.Length == 0)
{
throw new Exception("Dns server isn't specified !");
}
// See if query is in cache
if (m_UseDnsCache)
{
DnsServerResponse resopnse = DnsCache.GetFromCache(qname, (int)qtype);
if (resopnse != null)
{
return(resopnse);
}
}
int queryID = ID;
byte[] query = CreateQuery(queryID, qname, qtype, qclass);
// Create sending UDP socket.
Socket udpClient = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
udpClient.SendTimeout = 500;
// Send parallel query to all dns servers and get first answer.
DateTime startTime = DateTime.Now;
List <DnsServerResponse> responses = new List <DnsServerResponse>();
while (startTime.AddMilliseconds(timeout) > DateTime.Now)
{
foreach (IPAddress dnsServer in m_DnsServers)
{
try
{
udpClient.SendTo(query, new IPEndPoint(dnsServer, 53));
}
catch {}
}
// Wait 10 ms response to arrive, if no response, retransmit query.
if (udpClient.Poll(10, SelectMode.SelectRead))
{
try
{
byte[] retVal = new byte[1024];
int countRecieved = udpClient.Receive(retVal);
// If reply is ok, return it
DnsServerResponse serverResponse = ParseQuery(retVal, queryID);
// Cache query
if (m_UseDnsCache && serverResponse.ResponseCode == RCODE.NO_ERROR)
{
DnsCache.AddToCache(qname, (int)qtype, serverResponse);
}
responses.Add(serverResponse);
}
catch {}
}
}
udpClient.Close();
// If we reach so far, we probably won't get connection to dsn server
return(responses.Count > 0?responses[0]:new DnsServerResponse(false,
RCODE.SERVER_FAILURE,
new List <DNS_rr_base>(),
new List <DNS_rr_base>(),
new List <DNS_rr_base>()));
}
/// <summary>
/// Default constructor.
/// </summary>
/// <param name="answers">Dns answers.</param>
/// <param name="addTime">Entry add time.</param>
public DnsCacheEntry(DnsServerResponse answers, DateTime addTime)
{
m_pResponse = answers;
m_Time = addTime;
}
/// <summary>
/// Adds dns records to cache. If old entry exists, it is replaced.
/// </summary>
/// <param name="qname"></param>
/// <param name="qtype"></param>
/// <param name="answers"></param>
public static void AddToCache(string qname, int qtype, DnsServerResponse answers)
{
if (answers == null)
{
return;
}
try
{
lock (m_pCache)
{
// Remove old cache entry, if any.
if (m_pCache.Contains(qname + qtype))
{
m_pCache.Remove(qname + qtype);
}
m_pCache.Add(qname + qtype, new DnsCacheEntry(answers, DateTime.Now));
}
}
catch {}
}
