[cf-dev] CoAP retransmission on DTLS Fatal Alert ?

[Simon Bernard <contact@xxxxxxxxxxxxxxx>]

Hi,
  Currently, when we use Californium and try to send a request through 
DTLSConnector, if the request failed because of DTLS Fatal Alert (e.g. 
bad certificate), this is not visible at californium level. I mean 
Californium will never know thats something goes wrong, so at CoAP level 
we don't get a response for the request and we try to retransmit it 
until CoAP timeout or manual cancellation.

  I suppose this not really, the expected behavior.

  With the ErrorHandler class added by Kai in scandium, we can 
workaround the problem with some gymnastic by cancelling the request 
when we receive an Alert from the peer we requested. But this could make 
sense if that was managed by Californium.
   I think we should not try to retransmit request after a DTLS fatal 
error and we should add something like onError(String) method on 
MessageObserver to inform sender that the request failed.

   I looked at the code the main issues was :
  1) add a way to get error from RawDataChannel.
  2) retrieve exchange(s?) from address/port only ( we don't have 
message ID because we don't have CoAP message :p)
  3) notify all MessageObserver that the request failed
  4) set the exchange(s?) as completed

  Does it make sense ?

Simon