Re: [lwip-devel] MSG_MORE flag for send

[Marc CHALAND]

2007/10/27, Simon Goldschmidt <address@hidden>:
>
> Interesting patch (this functionality is required by the TCP RFCs by
> the way),

lwip already implement set of PSH flag at the end of write. Just to
present the context of lwip port on L4. We decided to put IP stack in
a separate task to prevent memory overflows for example and such
things. So client task communicate to this task by using a flexpage
(4096 bytes). As a consequence, client task has to cut what has to be
written into chunks.

For example, if a client task needs to write 5000 bytes, 4096 bytes
will be sent to stack, and then 904 bytes. Without the patch, two PSH
flags will be set instead of only one if lwip and application are in
the same task.

> but I'd rather solve this without adding an extra parameter
> to a load of functions throughout the whole stack (I can already hear
> people saying' why add an extra parameter (which might be put on the
> stack when calling the funciton) for something I don't need?').

I didn't think about using pcb. However, how stack will know that last
data written is last data ?

> Anyway, as this is something to be discussed and in order it isn't
> just forgot, you should send in a patch on savannah.

OK, let's have a discussion :). I post the patch to savannah.

Marc