Re: [lwip-users] how to free udp pcb

[Noam weissman]

Hi Kieran,

I have a new/old problem.

I am running a simple TCP terminal server that works like a telnet server but 
with no
Protocol. Actually a s simple TCP server. I use raw TCP terminal. 

It works ok but as far as I was able to spot I have memory leaks inside the 
LWIP stack.

My server accepts a pBuf and process it.

The transferred data in that pBuf is simple text lines. My server reads char by 
char and when it finds CR it 
copies this string to a command processor (text parser). This text parser reads 
the text and if necessary 
sends some data back to the client terminal.

If I pass a large file larger than the command processor queue I need to stall 
the pBuf processing until some space
Is freed in the command processor. If all is OK I do not free the accepted pBuf 
until It is processed.

That means the original pBuf is not immediately freed and at the same time the 
command processor sends  data to
The client TCP terminal. The pBuf is eventually freed after all the data is 
processed or if there is an error etc…

All is well so far.

If I disconnect the terminal (connected to my server) either in the middle of 
the file transfer or even if I wait to the file
End I can do that about more than 15-20 times. I have added error handling, 
polling, abort code etc… 

Nothing helped and after 20 or something iteration the TCP stoped working.

Although the Stack should free all pBuf’s I added code to free the received 
pBuf in case of abort. I also added
Freeing the recived pBuf in all the cases (abort, close or error).

Adding that extra freeing stopped the server from being completely un 
responsive but it is not able to send large amount 
Of data.

All the above suggests that memory handling is not working properly inside LwIP 
and therefore it is leaking.

Normally we work with an older stable version of LWIP (1.32 + FreeRTOS) 

I have tried using the latest version 1.41, I even added a few patches and 
installed the latest FreeRTOS but it behaves the same.

I feel that something basic is not working properly inside LwIP.

The code is running on STR91 with 96K RAM 

I have attached my TCP server source code + lwipopts.h

Any input will help.

Thanks,
Noam.


-----Original Message-----
From: address@hidden [mailto:address@hidden On Behalf Of Kieran Mansley
Sent: ש 07 ינואר 2012 18:04
To: Mailing list for lwIP users
Subject: Re: [lwip-users] how to free udp pcb


On 6 Jan 2012, at 14:12, Rahul Gundecha wrote:

> In my code,  the sockets are closed by calling lwip_close(). 

lwip_close() should be sufficient if you're using the sockets API.  Can you 
give more details of what shows that the PCBs are not being freed?

Kieran
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