[lwip-devel] [bug #56161] TCP state stays FIN_WAIT_1/CLOSING

[yuanxin]

URL:
  <https://savannah.nongnu.org/bugs/?56161>

                 Summary: TCP state stays FIN_WAIT_1/CLOSING
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: yuanx
            Submitted on: Thu 18 Apr 2019 12:01:15 PM UTC
                Category: TCP
                Severity: 3 - Normal
              Item Group: Faulty Behaviour
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None
            lwIP version: 2.0.3

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Details:

A TCP connection always stays in  FIN_WAIT_1/CLOSING while network
faults happening like net cable plugging out, which makes tcp pcb cannot be
released. The following is my modification in function tcp_slowtmr:

The original code:

  if (pcb->state == LAST_ACK) {
      if ((u32_t)(tcp_ticks - pcb->tmr) > 2 * TCP_MSL / TCP_SLOW_INTERVAL) {
        ++pcb_remove;
        LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: removing pcb stuck in
LAST-ACK\n"));
      }
    }

My code:

if (pcb->state == LAST_ACK || pcb->state == FIN_WAIT_1 || pcb->state ==
CLOSING) {
      if ((u32_t)(tcp_ticks - pcb->tmr) > 2 * TCP_MSL / TCP_SLOW_INTERVAL) {
        ++pcb_remove;
        LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: removing pcb stuck in
LAST-ACK\n"));
      }
    }





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