[lwip-devel] Comments about "low_level_output"

[Frédéric BERNON]

Before one of last commits (for bug #3168), "sendto" on udp or raw didn't return any error if the netif's low_level_output return something different than ERR_OK. It wasn't so good, but now, it's fixed. But during one of my unit tests to measure performance (a "hot" subject), I have note that the test failed (and of course, always succes before): in fact, because I had fill all my device MAC "descriptors", my low_level_output return a ERR_IF error (/* Low-level netif error */). And because this error is now return until conn->err, API stop to send, and even application got the error. All these errors checkings are good, but functionally, it's not correct. So, my questions:

 

1/ What do you think that a "low_level_output" function should return when all "buffers" are full?

 

2/ Is it something you do in your ports to "block" inside low_level_output to wait some space to send? (I don't think, but...)

 

3/ Isn't it something to document anywhere? I think, but where? I thought to rawpi.txt...

 

4/ Should we have to "filter" such "temporary errors" inside do_xxx functions? (It will add some code, and increase footprint, so, I don't like that)

 

My current workaround is to return ERR_OK in the place of ERR_IF in this case (it's just affect my port, and, after all, a packet could always be lost in the network...)

 

Thank you for your comments...

 

 

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Frédéric BERNON
HYMATOM SA
Chef de projet informatique
Microsoft Certified Professional
Tél. : +33 (0)4-67-87-61-10
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