[lwip-devel] [bug #59574] [LINGER] close function cannot return

[Song Pu]

URL:
  <https://savannah.nongnu.org/bugs/?59574>

                 Summary: [LINGER] close function cannot return
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: pusong666
            Submitted on: Mon 30 Nov 2020 06:39:46 AM UTC
                Category: sockets/netconn
                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: 2.1.1

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Details:

Initial condition:
1. Blocking socket
2. Enable LWIP_SO_LINGER, set linger (l_onoff=1, l_linger=2)
3. Enable LWIP_TCPIP_CORE_LOCKING

Step:
1. TCP Client iperf
2. Call close function

Result:
1. Close function cannot return after two seconds.

Analysis:
The close->lwip_netconn_do_close_internal will "sys_arch_sem_wait".
But the PCB may enter TIME_WAIT state, the TIME_WAIT pcbs won't be process by
slow_timer to trigger poll.
So the PCB will not handle "linger timer check" and "sys_sem_signal".

The task(call close function) will wait forever. 

Best regards




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