[lwip-users] AW: [lwip] 100 bytes packet problem

[Holger Fried]

> am using lwip in my application that is designed to measure network
> performance using this stack. A peculiar behavior exhibits in the case when
> my application send a packet size  of 100 bytes. The problem is very fatal
> as
> in this case amout of data send by application is always greater than the
> actual data
> transmission . I tried to debug and i am getting data spilling over  in this
> if block
> 
>     if(queuelen >= TCP_SND_QUEUELEN)
>     {
>         DEBUGF(TCP_OUTPUT_DEBUG, ("tcp_enqueue: too long queue %d (max
>         goto memerr;
>     }
> 
> The bad thing is that my application does not get informed of this status.
> Thus
> the value of application sent bytes is not exhibiting the actual bytes that
> are sent in reality. The value of actual byte sent is quite less than the
> value of byte sent as exhibited by the application.
> 
> Any help in this regard?????
> 
> Mumtaz Ahmad
> 
> 


I had this problem too. In my case, the defines TCP_MSS, TCP_SND_BUF and 
TCP_SND_QUEUELEN in lwipopts.h caused the problem. 
TCP_SND_BUF %(modulo) TCP_MSS wasn't 0, but TCP_SND_QUEUELEN is defined like 
this TCP_SND_QUEUELEN = 2 * TCP_SND_BUF/TCP_MSS.
This is an integer value and the rest of the division is cut, so your queue ist 
to small to take all the data.

I hope this can help you

Holger
[This message was sent through the lwip discussion list.]