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

[Dmitri Snejko]

> > 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>/
> />  /
> /> <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

I tried 1.3.1 and the last api_lib.c from SVC with a fix for netconn_recv. It is still loosing closed conditions. 
I think there is something  more then just racing conditions in on netconn->err. I found if i use 0 timeout  
closed remote side cached well but if i close the client side suddenly on the middle of transition LwIP won't recover and close  
the connection  with a timeout. It still keep it opened.
Socket API build on netconn as well is doing well in all situations.   

Dmitri.