[FR] Listen Callback: Ignore Connection Request

[maxsharabayko]

Need a way for an application to tell SRT to ignore a connection request via the listen callback.
Ignoring means neither accepting, nor rejecting. Just ignore and don't respond.
This would be useful in case a server needs some time to request user's passphrase from its database. The server will extract the required information from the Stream ID, ignore this exact connection request and initiate a database query. A repeated connection request will happen in about 150 ms (AFAIR), this would give some decent time to prepare for it and either accept or reject a connection.

Note other related FRs:

• [FR] A callback for rejected connection attempts on a listener.  #2621
• [FR] Listener callback: provide group ID #2728
• Listen Callback Provides a Stream ID without Length. Can't Properly Handle NULL Characters. #3073

[ethouris]

This isn't possible in the current implementation. First thing needed to implement this is to ship the connection processing into a separate thread; currently it's happening in the receiver worker thread that cannot be paused for a longer time because the same thread is processing the reading for all other SRT sockets sitting on the same multiplexer.

Another thing is that "ignoring" is not exactly predicted to happen in this protocol. If you don't respond for a request from the caller, the caller will repeateadly send the requests until the timeout is reached. The only sensible approach within the current rules of the protocol is to establish the security interchange connection first, exchange the required data and get the - encrypted of course - token that will be valid for a short time and will be used to authorize the transmission connection.