Re: [lwip-users] netconn/netbuf api with receiving timeout missing closed connection

[Kieran Mansley]

On Sat, 2009-10-24 at 00:29 -0400, Dmitri Snejko wrote:
> Hello,
> 
> I am trying  to  use netconn api with receiving timeout other  then 0. I 
> am using Lwip 1.3.0 with FreeRtos 5.4.2/ColdFire  and applied the patch 
> for 1.3.1
> 
> http://cvs.savannah.gnu.org/viewvc/lwip/src/include/lwip/err.h?root=lwip&r1=1.13&r2=1.14
>  
> <http://cvs.savannah.gnu.org/viewvc/lwip/src/include/lwip/err.h?root=lwip&r1=1.13&r2=1.14>
> 
> My application is a server listening for incoming connections, opening a 
> new netconn for any client (telnet like) and allocates a static buffer 
> from a pool to receive a stream. The receiving connection is not blocked 
> any more and I found I have a problem  when the connection is closed on 
> the remote side. My first impression was I could read netconn err field 
> when netconn_recv returns NULL and based on the error code decide if the 
> remote side closed the connection or a fatal error happened. That would 
> be a reason to close the connection on the sever side. It works fine for 
> some time but after a few hundred open/close cycles the server stops 
> seeing the other side closed its end.  I assume  netconn_recv returns 
> ERR_TIMEOUT which is not fatal. As result the buffer stays allocated and 
> I am running out resources.

There was a bug reported recently about the way that netconn_recv deals
with the netconn->err field:

http://savannah.nongnu.org/bugs/?27709

I hope that we will change the API for netconn_recv to return an error
like all the other netconn functions, rather than rely on the conn->err
field, but in the mean time you might like to try the partial fix
mentioned in that bug report.

Kieran