APPLICATION_CLOSE event overrides PACKET_ARRIVAL

[btuan]

Handling of APPLICATION_CLOSE condvar flag broadcasts in tcp_thread.c would override PACKET_ARRIVAL events, necessitating clunky handling of packets in event of APPLICATION_CLOSE.

Scenario in which this would be a problem:

• Both clients start in ESTABLISHED state
• Client 1 calls APPLICATION_CLOSE, sends FIN packet, enters FIN_WAIT_1
• Client 2 generates PACKET_ARRIVAL event
• Client 2 calls APPLICATION_CLOSE event
• At this point socket_state->flags.app_close == socket_state->flags.net_recv == 1
• For Client 2, cascading if statements call handling of APPLICATION_CLOSE in state ESTABLISHED, then PACKET_ARRIVAL is later handled after Client 1 enters FIN_WAIT_1, violating TCP state rules

Proposed solutions:

• Transpose the if clauses, so that flags.net_recv is considered first.
• Add another conditional in the code, perhaps something like this:

if (socket_state->flags.app_close)
{
    int packet_arrival = 0;
    chilog(TRACE, "Event received: app_close");
    socket_state->flags.app_close = 0;
    if (socket_state->flags.net_recv)
    {
        packet_arrival = 1;
        chilog(TRACE, "Event received: net_recv");
        socket_state->flags.net_recv = 0;
    }
    pthread_mutex_unlock(&socket_state->lock_event);

    if (packet_arrival)
    {
        chitcpd_dispatch_tcp(si, entry, PACKET_ARRIVAL);
    }
    chitcpd_dispatch_tcp(si, entry, APPLICATION_CLOSE);
}

@borjasotomayor