Stackoverflow error after millions of lookups

[jjxtra]

I am seeing the following error after running between 30-50 million lookups:

Stack overflow.
Repeat 87305 times:
--------------------------------
   at DnsClient.DnsDatagramReader.ReadLabels()
--------------------------------
   at DnsClient.DnsDatagramReader.ReadDnsName()
   at DnsClient.DnsRecordFactory.GetRecord(DnsClient.Protocol.ResourceRecordInfo)
   at DnsClient.DnsMessageHandler.GetResponseMessage(System.ArraySegment`1<Byte>)
   at DnsClient.DnsUdpMessageHandler+<QueryAsync>d__6.MoveNext()
   at System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object)
   at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1+AsyncStateMachineBox`1[[System.__Canon, System.Private.CoreLib, Version=6.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[DnsClient.DnsUdpMessageHandler+<QueryAsync>d__6, DnsClient, Version=1.6.1.0, Culture=neutral, PublicKeyToken=4574bb5573c51424]].MoveNext(System.Threading.Thread)
   at System.Threading.Tasks.AwaitTaskContinuation.RunOrScheduleAction(System.Runtime.CompilerServices.IAsyncStateMachineBox, Boolean)
   at System.Threading.Tasks.Task.RunContinuations(System.Object)
   at System.Threading.Tasks.Task`1[[System.Int32, System.Private.CoreLib, Version=6.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].TrySetResult(Int32)
   at System.Threading.Tasks.ValueTask`1+ValueTaskSourceAsTask+<>c[[System.Int32, System.Private.CoreLib, Version=6.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].<.cctor>b__4_0(System.Object)
   at System.Net.Sockets.Socket+AwaitableSocketAsyncEventArgs.InvokeContinuation(System.Action`1<System.Object>, System.Object, Boolean, Boolean)
   at System.Net.Sockets.Socket+AwaitableSocketAsyncEventArgs.OnCompleted(System.Net.Sockets.SocketAsyncEventArgs)
   at System.Net.Sockets.SocketAsyncEngine.System.Threading.IThreadPoolWorkItem.Execute()
   at System.Threading.ThreadPoolWorkQueue.Dispatch()
   at System.Threading.PortableThreadPool+WorkerThread.WorkerThreadStart()

Not sure if this is a specific domain name or not. I can re-run the process right where it left off and it runs fine for another 30-50 million lookups.

[MichaCo]

you'd have to provide a working/simple example of how to reproduce this
Thanks

[MichaCo]

That being said, @jjxtra, there is a part in ReadLabels which is recursive. DNS name labels can be referenced to reduce the size of the overall packet, and, each reference can again reference another, already exiting label.
If that causes an endless loop, then the data received is probably wrong or incomplete or something.
I could probably stop this after a few iterations, to prevent the stackoverflow. But you'd still get an exception..

Would be really interesting to know the server and query which causes that for you!

[jjxtra]

Could we terminate after 100 or 1000 iterations? If an ILogger reference is included it could log a warning with the host or query? Or maybe throw a LabelRecursionException that could be caught further down stream?

Easiest option for me is a log or throw and then it can print out the query and/or host name server used...

[jjxtra]

I believe this will resolve with #167 @MichaCo

[MichaCo]

Nice 👍 , I'll take a look later

[jjxtra]

Any update here @MichaCo ? Happy to help if you need it.

[MichaCo]

@jjxtra well this is a pretty low priority thing and I have to take some time to review your PR, and, I don't really have a lot of time atm.

I just did review it though, see comments.

During the review I had to write a unit test which actually can reproduce the StackOverflow error, so, I'd rather close your PR if you don't mind and then use my version? Unless you want to play more with it for fun.