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Re: [lwip-users] LwIP RAW - Simultaneous (full-duplex) communication

From: Simon Goldschmidt
Subject: Re: [lwip-users] LwIP RAW - Simultaneous (full-duplex) communication
Date: Thu, 5 Jul 2018 16:04:38 +0200

Nenad Pekez wrote:
> I took a look at this. This has been provided by Xilinx drivers already. 
> In their MAC receive handler they allocate memory for pbuf (call to 
> pbuf_realloc() actually) and enqueue it. In the main loop, I call Xilinx 
> function xemacif_input() which check if there is anything in the queue 
> and if there is netif->input() is called as described in the example.

And from which context are timers processed? If you don't have an OS, you
still have to ensure *not* to call into lwIP from an ISR.

> What I also noticed, when Zynq->PC side becomes active, in the TCP recv 
> callback I get p->tot_len much larger than 1446, and from time to time 
> there is also a print "Receive over run" from MAC error handler.

With OOSEQ queueing enabled, you can get pbuf chains after some segments
were lost and retransmissions have been received. This is normal, but if
you encounter this unexpectedly, you could either just have buffer overruns
(i.e. processor is not fast enough, or not enough memory available) or
driver bugs.


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