/// <summary>
/// Starts operation processing.
/// </summary>
/// <param name="dnsClient">DNS client.</param>
/// <returns>Returns true if asynchronous operation in progress or false if operation completed synchronously.</returns>
/// <exception cref="ArgumentNullException">Is raised when <b>dnsClient</b> is null reference.</exception>
internal bool Start(Dns_Client dnsClient)
{
if(dnsClient == null){
throw new ArgumentNullException("dnsClient");
}
SetState(AsyncOP_State.Active);
// Argument 'hostNameOrIP' is IP address.
if(Net_Utils.IsIPAddress(m_HostNameOrIP)){
m_pIPv4Addresses.Add(IPAddress.Parse(m_HostNameOrIP));
SetState(AsyncOP_State.Completed);
}
// This is probably NetBios name.
if(m_HostNameOrIP.IndexOf(".") == -1){
try{
// This callback is called when BeginGetHostAddresses method has completed.
AsyncCallback callback = delegate(IAsyncResult ar){
try{
foreach(IPAddress ip in System.Net.Dns.EndGetHostAddresses(ar)){
if(ip.AddressFamily == AddressFamily.InterNetwork){
m_pIPv4Addresses.Add(ip);
}
else{
m_pIPv6Addresses.Add(ip);
}
}
}
catch(Exception x){
m_pException = x;
}
SetState(AsyncOP_State.Completed);
};
// Start resolving host ip addresses.
System.Net.Dns.BeginGetHostAddresses(m_HostNameOrIP,callback,null);
}
catch(Exception x){
m_pException = x;
}
}
// Query A/AAAA records.
else{
#region A records transaction
DNS_ClientTransaction transaction_A = dnsClient.CreateTransaction(DNS_QType.A,m_HostNameOrIP,2000);
transaction_A.StateChanged += delegate(object s1,EventArgs<DNS_ClientTransaction> e1){
if(e1.Value.State == DNS_ClientTransactionState.Completed){
lock(m_pLock){
if(e1.Value.Response.ResponseCode != DNS_RCode.NO_ERROR){
m_pException = new DNS_ClientException(e1.Value.Response.ResponseCode);
}
else{
foreach(DNS_rr_A record in e1.Value.Response.GetARecords()){
m_pIPv4Addresses.Add(record.IP);
}
}
m_Counter++;
// Both A and AAAA transactions are completed, we are done.
if(m_Counter == 2){
SetState(AsyncOP_State.Completed);
}
}
}
};
transaction_A.Timeout += delegate(object s1,EventArgs e1){
lock(m_pLock){
m_pException = new IOException("DNS transaction timeout, no response from DNS server.");
m_Counter++;
// Both A and AAAA transactions are completed, we are done.
if(m_Counter == 2){
SetState(AsyncOP_State.Completed);
}
}
};
transaction_A.Start();
#endregion
#region AAAA records transaction
DNS_ClientTransaction transaction_AAAA = dnsClient.CreateTransaction(DNS_QType.AAAA,m_HostNameOrIP,2000);
transaction_AAAA.StateChanged += delegate(object s1,EventArgs<DNS_ClientTransaction> e1){
if(e1.Value.State == DNS_ClientTransactionState.Completed){
lock(m_pLock){
if(e1.Value.Response.ResponseCode != DNS_RCode.NO_ERROR){
m_pException = new DNS_ClientException(e1.Value.Response.ResponseCode);
}
else{
foreach(DNS_rr_AAAA record in e1.Value.Response.GetAAAARecords()){
m_pIPv6Addresses.Add(record.IP);
}
}
m_Counter++;
// Both A and AAAA transactions are completed, we are done.
if(m_Counter == 2){
SetState(AsyncOP_State.Completed);
}
}
}
};
transaction_AAAA.Timeout += delegate(object s1,EventArgs e1){
lock(m_pLock){
m_pException = new IOException("DNS transaction timeout, no response from DNS server.");
m_Counter++;
// Both A and AAAA transactions are completed, we are done.
if(m_Counter == 2){
SetState(AsyncOP_State.Completed);
}
}
};
transaction_AAAA.Start();
#endregion
}
// Set flag rise CompletedAsync event flag. The event is raised when async op completes.
// If already completed sync, that flag has no effect.
lock(m_pLock){
m_RiseCompleted = true;
return m_State == AsyncOP_State.Active;
}
}
/// <summary>
/// Starts looking up MX records for specified domain.
/// </summary>
/// <param name="dnsClient">DNS client.</param>
/// <param name="domain">Domain name.</param>
/// <param name="domainIsCName">If true domain name is CNAME(alias).</param>
/// <exception cref="ArgumentNullException">Is riased when <b>dnsClient</b> or <b>domain</b> is null reference.</exception>
private void LookupMX(Dns_Client dnsClient,string domain,bool domainIsCName)
{
if(dnsClient == null){
throw new ArgumentNullException("dnsClient");
}
if(domain == null){
throw new ArgumentNullException("domain");
}
// Try to get MX records.
DNS_ClientTransaction transaction_MX = dnsClient.CreateTransaction(DNS_QType.MX,domain,2000);
transaction_MX.StateChanged += delegate(object s1,EventArgs<DNS_ClientTransaction> e1){
try{
if(e1.Value.State == DNS_ClientTransactionState.Completed){
// No errors.
if(e1.Value.Response.ResponseCode == DNS_RCode.NO_ERROR){
List<DNS_rr_MX> mxRecords = new List<DNS_rr_MX>();
foreach(DNS_rr_MX mx in e1.Value.Response.GetMXRecords()){
// Skip invalid MX records.
if(string.IsNullOrEmpty(mx.Host)){
}
else{
mxRecords.Add(mx);
}
}
// Use MX records.
if(mxRecords.Count > 0){
m_pHosts = new HostEntry[mxRecords.Count];
// Create name to index map, so we can map asynchronous A/AAAA lookup results back to MX priority index.
Dictionary<string,int> name_to_index_map = new Dictionary<string,int>();
List<string> lookupQueue = new List<string>();
// Process MX records.
for(int i=0;i<m_pHosts.Length;i++){
DNS_rr_MX mx = mxRecords[i];
IPAddress[] ips = Get_A_or_AAAA_FromResponse(mx.Host,e1.Value.Response);
// No A or AAAA records in addtional answers section for MX, we need todo new query for that.
if(ips.Length == 0){
name_to_index_map[mx.Host] = i;
lookupQueue.Add(mx.Host);
}
else{
m_pHosts[i] = new HostEntry(mx.Host,ips,null);
}
}
// We have MX records which A or AAAA records not provided in DNS response, lookup them.
if(lookupQueue.Count > 0){
GetHostsAddressesAsyncOP op = new GetHostsAddressesAsyncOP(lookupQueue.ToArray(),true);
// This event is raised when lookup completes asynchronously.
op.CompletedAsync += delegate(object s2,EventArgs<GetHostsAddressesAsyncOP> e2){
LookupCompleted(op,name_to_index_map);
};
// Lookup completed synchronously.
if(!dnsClient.GetHostsAddressesAsync(op)){
LookupCompleted(op,name_to_index_map);
}
}
// All MX records resolved.
else{
SetState(AsyncOP_State.Completed);
}
}
// Use CNAME as initial domain name.
else if(e1.Value.Response.GetCNAMERecords().Length > 0){
if(domainIsCName){
m_pException = new Exception("CNAME to CNAME loop dedected.");
SetState(AsyncOP_State.Completed);
}
else{
LookupMX(dnsClient,e1.Value.Response.GetCNAMERecords()[0].Alias,true);
}
}
// Use domain name as MX.
else{
m_pHosts = new HostEntry[1];
// Create name to index map, so we can map asynchronous A/AAAA lookup results back to MX priority index.
Dictionary<string,int> name_to_index_map = new Dictionary<string,int>();
name_to_index_map.Add(domain,0);
GetHostsAddressesAsyncOP op = new GetHostsAddressesAsyncOP(new string[]{domain});
// This event is raised when lookup completes asynchronously.
op.CompletedAsync += delegate(object s2,EventArgs<GetHostsAddressesAsyncOP> e2){
LookupCompleted(op,name_to_index_map);
};
// Lookup completed synchronously.
if(!dnsClient.GetHostsAddressesAsync(op)){
LookupCompleted(op,name_to_index_map);
}
}
}
// DNS server returned error, just return error.
else{
m_pException = new DNS_ClientException(e1.Value.Response.ResponseCode);
SetState(AsyncOP_State.Completed);
}
}
transaction_MX.Timeout += delegate(object s2,EventArgs e2){
m_pException = new IOException("DNS transaction timeout, no response from DNS server.");
SetState(AsyncOP_State.Completed);
};
}
catch(Exception x){
m_pException = x;
SetState(AsyncOP_State.Completed);
}
};
transaction_MX.Start();
}
