UDP Connected: Unhandled message SocketReceived

[jjmSE]

Version Information
Version of Akka.NET? 1.4.25
Which Akka.NET Modules? Akka.IO

Describe the bug
When communication with the device is complete, we send a UdpConnected.Disconnect message to close the socket.
After that, we receive UdpConnected.Disconnected but we see an unhandled message in UdpConnection actor:

Message [SocketReceived] to [akka://dlmshe/system/IO-UDP-CONN/$a#267206278] was not delivered. [1] dead letters
encountered. If this is not an expected behavior then [akka://dlmshe/system/IO-UDP-CONN/$a#267206278] may have
terminated unexpectedly. This logging can be turned off or adjusted with configuration settings 'akka.log-dead-letters' and
'akka.log-dead-letters-during-shutdown'.

Expected behavior
UDP socket is closed successfully.

Actual behavior
UDP socket is closed successfully but we see an unhandled message.

Environment
Windows
.NET Framework 4.8

akka_seq_logs.csv

[Arkatufus]

This is (almost) normal, the socket is read asynchronously, and a received message can be sent after the actor died, and since the actor already died, it will be sent to deadletter.
I said almost because this is actually undesireable behaviour because this is an absolute source of memory leak if DirectBufferPool is being used.
We'll be looking into this, its probable that the UDP actor need to be redesigned from the ground up to bulletproof it.

@jjmSE thank you for the report.

[Arkatufus]

This is now trivial to fix after #5404 is merged in. We just need to add IDeadLetterSuppresion to SocketReceived.