Re: [lwip-users] Telnet server/LWIP crash

[Andrew_Kunz]

Thank you.  Not thread-safe makes
life more interesting I guess.

Adding the sys_mbox_post() worked!  At
least with initial testing.

THANK YOU!

Andy

Frédéric BERNON <address@hidden>
Sent by: address@hidden

10/30/2007 04:30 PM

Please respond to
Frédéric BERNON <address@hidden>; Please respond to
Mailing list for lwIP users <address@hidden>

To	"Mailing list for lwIP users" <address@hidden>
cc
Subject	Re: [lwip-users] Telnet server/LWIP crash

First, I think you should upgrade to the
lastest CVS head (joke, of course).
 
Some informations you have to know about
lwIP:
 
- lwIP 1.2.0 - and even lastest cvs head
- are not safe-thread about using two application threads on a same socket
- lwIP 1.2.0 tcp close was bugged, and is
just fixed on CVS head
 
But, even if you don't upgrade to CVS head,
adding recv timeouts on your code is not very difficult, but in this case,
this is not a solution. A first patch should be to add a "sys_mbox_post(telnetNetCon->recvmbox,
NULL);" before the netconn_close (perhaps after that with a little
vTaskDelay). Like this, the thread blocked on netconn_recv will be directly
wake-up.
 
----- Original Message ----- 
From: address@hidden

To: address@hidden

Sent: Tuesday, October 30, 2007 6:37 PM
Subject: [lwip-users] Telnet server/LWIP crash


This is a lengthy explanation, but after 2-3 weeks of banging my head into
the wall I think it is necessary. 

I am working on a Telnet server using 1.2.0 release (as I am unable to
get latest CVS head to compile and run on the AT91SAM7X demo board under
FreeRTOS).  Because 1.2.0 does not support receive timeouts, the server
is implemented as two tasks.  One handles the "receive from network"
and the other "send to network" functions, using FreeRTOS queues
to send character data to/from the application task.

Before you say "upgrade to the latest CVS head" - I have already
tried unsuccessfully for much of this time to do just that, however the
update simply doesn't work, even when I roll back to just porting the new
LWIP to the original FreeRTOS demo that I got with the original.

A little more background... 

It is possible for the application task to request a session end (primarily
to log out idle users).  This is accomplished with the following code:

static void close_telnet (void) 
        { 
        if (net_connection_open)
                {
                // Network connection
is closed again 
                net_connection_open
= FALSE; 
                // Don't do this
again until new connection starts 
                idletimer = 0;
                netconn_close (telnetNetCon);
                tn_isonline[0]
= FALSE; 
                while (netconn_delete
(telnetNetCon) != ERR_OK) 
                    
   { 
                    
   vTaskDelay (TELNET_SHORT_DELAY); 
                    
   } 
                vTaskDelay (TELNET_LONG_DELAY);
                }
        } 


(Note: The variable "net_connection_open" is a flag which is
set TRUE when the receiver task gets a connection from a client and starts
communicating with them.) 

While this is going on, the "read from network" task is waiting
in a netconn_recv() call.  It does not return immediately when the
other task calls close_telnet() above (which I would expect due to the
netconn_close() and netconn_delete() calls). 

The client tells me immediately that it has lost its connection when close_telnet()
is executed. 

If I then attempt another connection from a client, the "read from
network" task returns from the netconn_recv() it has been in, but
the return value is pointing to the same location as when it was receiving
valid data.  At this point I just netbuf_delete() it, then go back
to a netconn_accept() waiting for the next telnet client to attach.

It accepts the connection, returning same pointer address as previous connection.
 Starts the connection process (which includes sending a DO and DONT
string to the client), but when the program starts attempting to wait for
more data to come from the new client, the micro resets with a data abort
(on the ARM7, this generally means that data was either mis-aligned or
not present). 

Another scenario - the client disconnects from the server.  When this
happens, I am able to start a new client and log in once successfully,
but logging out and attempting a third time results in a data abort also.

If you need the code, I would be happy to provide it.  If you have
ANY advice, I'd love to hear it. 

Thanks. 

Andy

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