[QUESTION] SCTP session free always timeout

[LiangFang001]

Hi,

We ran this sample on the Raspberry Pi platform.
Each time the stream was closed, there was always 2s timeout in freeSctpSession to wait SCTP_SESSION_SHUTDOWN_COMPLETED.

    usrsctp_deregister_address(pSctpSession);
    /* handle issue mentioned here: https://github.com/sctplab/usrsctp/issues/147
     * the change in shutdownStatus will trigger onSctpOutboundPacket to return -1 */
    ATOMIC_STORE(&pSctpSession->shutdownStatus, SCTP_SESSION_SHUTDOWN_INITIATED);

    if (pSctpSession->socket != NULL) {
        usrsctp_set_ulpinfo(pSctpSession->socket, NULL);
        usrsctp_shutdown(pSctpSession->socket, SHUT_RDWR);
        usrsctp_close(pSctpSession->socket);
    }
    shutdownTimeout = GETTIME() + DEFAULT_SCTP_SHUTDOWN_TIMEOUT;
    while (ATOMIC_LOAD(&pSctpSession->shutdownStatus) != SCTP_SESSION_SHUTDOWN_COMPLETED && GETTIME() < shutdownTimeout) {
        THREAD_SLEEP(DEFAULT_USRSCTP_TEARDOWN_POLLING_INTERVAL);
    }

It seems that onSctpOutboundPacket isn't be called after usrsctp_shutdown/usrsctp_close.
SCTP session needs to wait three way handshake completed, and onSctpOutboundPacket should be called before sctp session fully destroyed.
Why does the above issue happen?