void OnReceive (IAsyncResult ares)
{
if (disposed)
return;
int nread = 0;
EndPoint remote_ep = client.RemoteEndPoint;
try {
nread = client.EndReceive (ares);
} catch (Exception e) {
Console.Error.WriteLine (e);
}
BeginReceive ();
byte [] buffer = (byte []) ares.AsyncState;
if (nread > 12) {
DnsResponse response = new DnsResponse (buffer, nread);
int id = response.Header.ID;
SimpleResolverEventArgs args = null;
lock (queries) {
if (queries.TryGetValue (id, out args)) {
queries.Remove (id);
}
}
if (args != null) {
Timer t = args.Timer;
if (t != null)
t.Change (Timeout.Infinite, Timeout.Infinite);
try {
ProcessResponse (args, response, remote_ep);
} catch (Exception e) {
args.ResolverError = (ResolverError) (-1);
args.ErrorMessage = e.Message;
}
IPHostEntry entry = args.HostEntry;
if (args.ResolverError != 0 && args.PTRAddress != null && entry != null && entry.HostName != null) {
args.PTRAddress = null;
SendAQuery (args, entry.HostName, true);
args.Timer.Change (5000, Timeout.Infinite);
} else {
args.OnCompleted (this);
}
}
}
FreeBuffer (buffer);
}
void ProcessResponse (SimpleResolverEventArgs args, DnsResponse response, EndPoint server_ep)
{
DnsRCode status = response.Header.RCode;
if (status != 0) {
if (args.PTRAddress != null) {
// PTR query failed -> no error, we have the IP
return;
}
args.ResolverError = (ResolverError) status;
return;
}
// TODO: verify IP of the server is in our list and the same one that got the query
IPEndPoint ep = (IPEndPoint) server_ep;
if (ep.Port != 53) {
args.ResolverError = ResolverError.ResponseHeaderError;
args.ErrorMessage = "Port";
return;
}
DnsHeader header = response.Header;
if (!header.IsQuery) {
args.ResolverError = ResolverError.ResponseHeaderError;
args.ErrorMessage = "IsQuery";
return;
}
// TODO: handle Truncation. Retry with bigger buffer?
if (header.QuestionCount > 1) {
args.ResolverError = ResolverError.ResponseHeaderError;
args.ErrorMessage = "QuestionCount";
return;
}
ReadOnlyCollection<DnsQuestion> q = response.GetQuestions ();
if (q.Count != 1) {
args.ResolverError = ResolverError.ResponseHeaderError;
args.ErrorMessage = "QuestionCount 2";
return;
}
DnsQuestion question = q [0];
/* The answer might have dot at the end, etc...
if (String.Compare (question.Name, args.HostName) != 0) {
args.ResolverError = ResolverError.ResponseHeaderError;
args.ErrorMessage = "HostName - " + question.Name + " != " + args.HostName;
return;
}
*/
DnsQType t = question.Type;
if (t != DnsQType.A && t != DnsQType.AAAA && t != DnsQType.PTR) {
args.ResolverError = ResolverError.ResponseHeaderError;
args.ErrorMessage = "QType " + question.Type;
return;
}
if (question.Class != DnsQClass.IN) {
args.ResolverError = ResolverError.ResponseHeaderError;
args.ErrorMessage = "QClass " + question.Class;
return;
}
ReadOnlyCollection<DnsResourceRecord> records = response.GetAnswers ();
if (records.Count == 0) {
if (args.PTRAddress != null) {
// PTR query failed -> no error
return;
}
args.ResolverError = ResolverError.NameError; // is this ok?
args.ErrorMessage = "NoAnswers";
return;
}
List<string> aliases = null;
List<IPAddress> addresses = null;
foreach (DnsResourceRecord r in records) {
if (r.Class != DnsClass.IN)
continue;
if (r.Type == DnsType.A || r.Type == DnsType.AAAA) {
if (addresses == null)
addresses = new List<IPAddress> ();
addresses.Add (((DnsResourceRecordIPAddress) r).Address);
} else if (r.Type == DnsType.CNAME) {
if (aliases == null)
aliases = new List<string> ();
aliases.Add (((DnsResourceRecordCName) r).CName);
} else if (r.Type == DnsType.PTR) {
args.HostEntry.HostName = ((DnsResourceRecordPTR) r).DName;
args.HostEntry.Aliases = aliases == null ? EmptyStrings : aliases.ToArray ();
args.HostEntry.AddressList = EmptyAddresses;
return;
}
}
IPHostEntry entry = args.HostEntry ?? new IPHostEntry ();
if (entry.HostName == null && aliases != null && aliases.Count > 0) {
entry.HostName = aliases [0];
aliases.RemoveAt (0);
}
entry.Aliases = aliases == null ? EmptyStrings : aliases.ToArray ();
entry.AddressList = addresses == null ? EmptyAddresses : addresses.ToArray ();
args.HostEntry = entry;
if ((question.Type == DnsQType.A || question.Type == DnsQType.AAAA) && entry.AddressList == EmptyAddresses) {
args.ResolverError = ResolverError.NameError;
args.ErrorMessage = "No addresses in response";
} else if (question.Type == DnsQType.PTR && entry.HostName == null) {
args.ResolverError = ResolverError.NameError;
args.ErrorMessage = "No PTR in response";
}
}
byte [] GetFreshBuffer ()
{
#if !REUSE_RESPONSES
return new byte [512];
#else
DnsResponse response = null;
lock (responses_avail) {
if (responses_avail.Count > 0) {
response = responses_avail.Pop ();
}
}
if (response == null) {
response = new DnsResponse ();
} else {
response.Reset ();
}
return response;
#endif
}
