[lwip-devel] [bug #37958] netconn API doesn't handle correctly connections half-closed by peer

[Valery Ushakov]

URL:
  <http://savannah.nongnu.org/bugs/?37958>

                 Summary: netconn API doesn't handle correctly connections
half-closed by peer
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: uwe
            Submitted on: Wed 19 Dec 2012 03:26:21 PM GMT
                Category: None
                Severity: 3 - Normal
              Item Group: Faulty Behaviour
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: 
            lwIP version: CVS Head

    _______________________________________________________

Details:

Half-open connections that were half-closed by peer are stuck with
netconn::last_err = ERR_CLSD, which prevents further writes over them.  Cf.
netconn_recv_data:


    if (buf == NULL) {
      API_EVENT(conn, NETCONN_EVT_RCVMINUS, 0);
      /* Avoid to lose any previous error code */
      NETCONN_SET_SAFE_ERR(conn, ERR_CLSD);
      return ERR_CLSD;
    }


As a quick kludge I changed that to


      sys_mbox_free(&conn->recvmbox);
      sys_mbox_set_invalid(&conn->recvmbox);


which, from a quick look, should be thread-safe, since recv_tcp() won't send
anything after sending NULL pbuf to indicate that peer has performed close.

And changed LWIP_ERROR checks for sys_mbox_valid(&conn->recvmbox) in
netconn_recv() and netconn_recv_data() with explicit


  if (!sys_mbox_valid(&conn->recvmbox)) {
    return sys_mbox_valid(&conn->acceptmbox) ? ERR_CONN : ERR_CLSD;
  }


which seems to work, but I haven't investigated/tested this thoroughly.





    _______________________________________________________

Reply to this item at:

  <http://savannah.nongnu.org/bugs/?37958>

_______________________________________________
  Message sent via/by Savannah
  http://savannah.nongnu.org/