[lwip-users] Returning ERR_MEM from low_level_output()?

[Ceresoli Luca]

Hi,

from the ethernetif.c skeleton file, the comment to low_level_output():
> * @note Returning ERR_MEM here if a DMA queue of your MAC is full can lead to
> *       strange results. You might consider waiting for space in the DMA queue
> *       to become availale since the stack doesn't retry to send a packet
> *       dropped because of memory failure (except for the TCP timers).

I didn't understand the effects of returning ERR_MEM. Trying to backtrack 
through the functions that call netif->linkoutput(), I got lost in the graph.

What would be the correct thing to return when there is no buffering space 
available in the driver and it is not possible (or not convenient) to wait?

And what would be the negative effect of returning ERR_MEM and dropping the 
packet?


Luca Ceresoli