Re: [lwip-users] [Issue] TCP fragmentation over PPP - fragments are lost in LwIP if data is queued for sending

[Marco Jakobs]

Hi Simon,

> Try disabling TCP nagle to see if that's a problem

I'm not sure what's the right way to do that as there is no option in opt.h, 
I've commented that out for a test (in tcp_out.c):

/*
    if((tcp_do_output_nagle(pcb) == 0) &&
      ((pcb->flags & (TF_NAGLEMEMERR | TF_FIN)) == 0)){
      break;
    }
*/

Here, the packets over the air are:

1) 1024 bytes
2) 376 bytes
3) 648 bytes

That's 2048 bytes in total, they are aligned and the same trailing 752 bytes 
are missing. The difference is that it's now 3 segments instead of two.


> debug the pcb to see how many segments are in unsent/unacked of the pcb 
> sending to PPP

Where would be the best place to do that? 

>One problem is that we don't really have support for 1.4.1 PPP, as Sylvain 
>really rewrote PPP for 2.0.0 and wasn't there before to know the "old" PPP.
>Keeping that aside, to me this still looks like some kind of race condition 
>induced by threading issues...

Not sure where and why ... that's not modified and PPP runs in it's own thread 
...