I have been trying to implement a wrapper library for the Linux interface to SCTP sockets, and I am not sure how to integrate the asynchronous style of errors (where they are delivered via events). All example code I have seen, if it deals with the errors at all, simply prints out the information related to the error when it is received, but inserting error-handling code there seems like it would be ineffective, because by that point all of the context related to the original message which was sent has been lost and only a 32-bit integer sinfo_context remains. It also seems that there is no way to directly tell when a given message has been acknowledged successfully by the remote peer, which would make it impossible to implement an approach which listens for errors after sending a message, because the context information for successfully-delivered messages could never be freed.
Is there a way to handle the errors related to a given sending operation as part of the call to a send function, or is there a different way to approach error handling for SCTP which does not lose the context of the error?
One solution which I have considered is using the SCTP_SENDER_DRY notification to tell when packets have been sent, however this requires sending only one packet at a time. Another idea is to use the peer's receiver window size together with the sinfo_cumtsn field of sctp_sndrcvinfo to calculate how much data has been acknowledged as fully received using the cumulative TSN, however there are a couple of disadvantages to this: first, it requires bookkeeping overhead to calculate a number of bytes received by the peer based on the cumulative TSN (especially if the peer's window size may change); second, it requires waiting until all earlier packets were received before reporting success, which seems to defeat the purpose of SCTP's multistreaming; and third, it seems like it would not work for unordered packets.