onALPNClientSuggest

[kazu-yamamoto]

The no_application_protocol alert should be sent when a client "application_layer_protocol_negotiation" extension advertises only protocols that the server does not support. The current onALPNClientSuggest does not implement this.

How should we implement this?

• A) If "" is returned from onALPNClientSuggest, sent the alert.
• B) If an exception is thrown from onALPNClientSuggest, sent the alert.
• C) Both.

[ocheron]

Users should not have to use exceptions in callbacks.
A) seems best alternative if we don't want to change API just for this.

Uncaught exception in user code should trigger interal_error alert (like we have already).