Re: [lwip-users] Dropped UDP packages

[Andrew Foster]

To be fair, I haven't looked at the latest SDK from TI for the Tempest 
class (9xxx). TI may have corrected the issues that I experienced. The 
E2E forum would probably be a better place to get updates on TI's 
lwip/FreeRTOS example. You may also try searching the lwip-users archive 
for others who have came across similar issues.

When I did my development it was based on the 6965 eth SDK. This 
implementation called into lwIP from the interrupt level. Generally, 
that is a bad idea because it can lead to issues resulting from 
concurrent access on the pbuf chain. Without an entire redesign of the 
Stellaris model, you are pretty much left with accepting the 
vulnerability or disabling interrupts while calling into lwIP.

That being said, I would still work to prove/disprove the vulnerability. 
When I was working through my issue, the application failed pretty 
spectacularly. When you dork up the pbuf chain the tcp_ip_thread 
typically freezes or writes to an erroneous memory location.  Your issue 
could still be caused by a number of other things.

Andrew

On 08/18/2011 10:26 AM, Emil Ohlsson wrote:
> Actually I'm using a TI Stellaris Cortex M3 (LM3S9B96). What kind of flaws 
> where you thinking of?
>
> Thanks
> Emil Ohlsson
>
> -----Original Message-----
> From: address@hidden [mailto:address@hidden On Behalf Of Andrew Foster
> Sent: den 18 augusti 2011 15:11
> To: Mailing list for lwIP users
> Subject: Re: [lwip-users] Dropped UDP packages
>
> Emil,
>
> I've had to debug a similar event on my target and found it helpful to get 
> familiar with stats.c. The various compiler switches can be found in 
> lwipopts.h(sounds like you are already aware of UDP_STATS.) More specifically, 
> look in to MEM, MEMP, PBUF and SYS stats. Verify you don't have any errors in 
> these paths before getting down and dirty with your ISR. I know the Luminary/TI 
> ISR has some flaws but hopefully your target platform's ISR has been 
> implemented correctly.
>
> Hope this helps,
>
> Andrew
>
>
>
> On 08/18/2011 08:59 AM, Emil Ohlsson wrote:
> > Hi!
> >
> > I'm writing and application that listens for RTP-packages via UDP multicast. 
> > But for some reason there is a small package drop, say 1 per 1000 packets.
> >
> > I've activated UDP stats and it seems like lwIP doesn't think there are any 
> > dropped packets, but from my application I can see that there are missing 
> > sequence numbers. And I can see that those packages are being sent using 
> > wireshark.
> >
> > Does lwIP discard packages if the application isn't fast enough to
> > fetch them? Could there be any other thing I've missed? Could there be
> > some memory issue? Any comments or ideas are very welcome
> >
> > Best regards
> > Emil Ohlsson
> >
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