Re: [lwip-users] Delay fixes dropped packets

[address@hidden]

From your description, it seems like memory beloging to a packet is 
being changed after being delivered to your netif->linkoutput function. 
Does your MAC support DMA? If so, make sure the pbufs are freed after 
receiving a transmit interrupt for the packet. (pbuf_free(p) then must 
*not* be called directly in the linkoutput function! Doing so leads to 
memory being freed before it is actually transmitted. Thus the next call 
to pbuf_alloc will get the same pbuf and may alter the data while the 
MAC sends it using its DMA engine.

Simon


JM wrote:
> I'm using lwIP on a Stellaris micro, and saw lots of dropped packets.  
> Upon further investigation, it turns out these packets were failing 
> TCP checksum.  I noticed that if I enabled debugging in the correct 
> areas, and enough of it, the issue went away.  Long story short, after 
> lots of trial and error I discovered that if I disable debugging and 
> add a delay of 300us at the very end, before the return, in 
> ip_output_if(), it fixes the problem.  If I decrease the delay, the 
> problem starts appearing and becomes worse as I continue to decrease 
> the delay. 
>
> The driver for the onboard ethernet controller is from the Luminary 
> driver library.  I don't imagine that a very high percentage of users 
> here use the same chip I'm using, but generally speaking, any idea 
> what I can look for; what would cause this?  I'm mainly recieving 
> data.  It's streaming audio data so once I initiate it, the stack only 
> has to ACK. 
>
>
>
>
> ------------------------------------------------------------------------
>
> _______________________________________________
> lwip-users mailing list
> address@hidden
> http://lists.nongnu.org/mailman/listinfo/lwip-users