/// <summary>
/// This method is called when GetHostAddresses operation has completed.
/// </summary>
/// <param name="op">Asynchronous operation.</param>
/// <param name="index">Index in 'm_pHostEntries' where to store lookup result.</param>
private void GetHostAddressesCompleted(GetHostAddressesAsyncOP op,int index)
{
lock(m_pLock){
try{
if(op.Error != null){
// We wanted any of the host names to resolve:
// *) We have already one resolved host name.
// *) We have more names to resolve, so next may succeed.
if(m_ResolveAny && (m_ResolvedCount > 0 || m_pIpLookupQueue.Count > 1)){
}
else{
m_pException = op.Error;
}
}
else{
m_pHostEntries[index] = new HostEntry(op.HostNameOrIP,op.Addresses,null);
m_ResolvedCount++;
}
m_pIpLookupQueue.Remove(index);
if(m_pIpLookupQueue.Count == 0){
// We wanted resolve any, so some host names may not be resolved and are null, remove them from response.
if(m_ResolveAny){
List<HostEntry> retVal = new List<HostEntry>();
foreach(HostEntry host in m_pHostEntries){
if(host != null){
retVal.Add(host);
}
}
m_pHostEntries = retVal.ToArray();
}
SetState(AsyncOP_State.Completed);
}
}
catch(Exception x){
m_pException = x;
SetState(AsyncOP_State.Completed);
}
}
op.Dispose();
}
/// <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();
}