/// <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(); }
/// <summary> /// This method is called when A/AAAA lookup has completed. /// </summary> /// <param name="op">Asynchronous operation.</param> /// <param name="name_to_index">Dns name to index lookup table.</param> /// <exception cref="ArgumentNullException">Is raised when <b>op</b> or <b>name_to_index</b> is null reference value.</exception> private void LookupCompleted(GetHostsAddressesAsyncOP op,Dictionary<string,int> name_to_index) { if(op == null){ throw new ArgumentNullException("op"); } if(op.Error != null){ // If we have any resolved DNS, we don't return error if any. bool anyResolved = false; foreach(HostEntry host in m_pHosts){ if(host != null){ anyResolved = true; break; } } if(!anyResolved){ m_pException = op.Error; } } else{ foreach(HostEntry host in op.HostEntries){ m_pHosts[name_to_index[host.HostName]] = host; } } op.Dispose(); // Remove unresolved DNS entries from response. List<HostEntry> retVal = new List<HostEntry>(); foreach(HostEntry host in m_pHosts){ if(host != null){ retVal.Add(host); } } m_pHosts = retVal.ToArray(); SetState(AsyncOP_State.Completed); }
/// <summary> /// Starts resolving multiple host IPv4 and IPv6 addresses. /// </summary> /// <param name="op">Asynchronous operation.</param> /// <returns>Returns true if aynchronous operation is pending (The <see cref="GetHostsAddressesAsyncOP.CompletedAsync"/> event is raised upon completion of the operation). /// Returns false if operation completed synchronously.</returns> /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and and this method is accessed.</exception> /// <exception cref="ArgumentNullException">Is raised when <b>op</b> is null reference.</exception> public bool GetHostsAddressesAsync(GetHostsAddressesAsyncOP op) { if(m_IsDisposed){ throw new ObjectDisposedException(this.GetType().Name); } if(op == null){ throw new ArgumentNullException("op"); } if(op.State != AsyncOP_State.WaitingForStart){ throw new ArgumentException("Invalid argument 'op' state, 'op' must be in 'AsyncOP_State.WaitingForStart' state.","op"); } return op.Start(this); }