Re: [lwip-users] sys_arch_mbox_fetch() implementation for FreeRTOS

[massimiliano cialdi]

hello,

the setsockopt(SO_RCVTIMEO) POSIX call contemplates the possibility of imposing 0 as the 'timeout' parameter, and in that case that socket becomes non-blocking (See, for example, https://stackoverflow.com/questions/49706883/disable-socket-timeout-via-setsockopt).

The socket API of lwip does not match this behavior. Or am I mistaken?
Would it be possible to impose the underlying netconn as nonblocking (using e.g. `netconn_set_nonblocking()`) when the timeout is 0? Am I oversimplifying?

best Regards

Max

Massimiliano Cialdi

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On 20/06/22 21:17, goldsimon@gmx.de wrote:

> Am
>       20.06.2022 um 11:22 schrieb massimiliano cialdi via lwip-users:
>       
> > hello,
> >         
> >         
> >         I am using lwip 2.1.3 and contrib 2.1.0.
> >         
> >         in the ports/freertos/sys_arch.c file there is the
> >         sys_arch_mbox_fetch()
> >         
> >         function, in which there is the timeout_ms parameter.
> >         
> >         Given the name I expect the sys_arch_mbox_fetch() function to be
> >         
> >         blocking for a maximum time corresponding to timeout_ms
> >         milliseconds.
> >         
> >         I see this piece of code, though:
> >         
> >         
> >            if (!timeout_ms) {
> >         
> >              /* wait infinite */
> >         
> >              ret = xQueueReceive(mbox->mbx, &(*msg),
> >         portMAX_DELAY);
> >         
> >              LWIP_ASSERT("mbox fetch failed", ret == pdTRUE);
> >         
> >            } else {
> >         
> >         
> >         I wonder why I should wait infinitely if I set the timeout to 0
> >         (so I
> >         
> >         want it non-blocking)? is this a bug?
> >         
> >       
>       
>       See the documentation of that parameter in sys.h:
>       
>       @param timeout maximum time (in milliseconds) to wait for a
>       message (0 =
>       
>       wait forever)
>       
>       
>       It's a bit unfortunate, but it has been like that since forever (0
>       =
>       
>       wait forever). The code uses sys_arch_mbox_tryfetch() when it does
>       not
>       
>       want to block at all.
>       
>       
> >         
> >         In fact, it happens to me occasionally (I have yet to figure out
> >         the
> >         
> >         conditions) that even though I have the timeout set to 0,
> >         re-read with
> >         
> >         lwip_getsockopt(SO_RCVTIMEO), the task blocks indefinitely while
> >         waiting
> >         
> >         for a message in the queue.
> >         
> >       
>       
>       That would be odd. Please report a fix if you find one.
>       
>       
>       Regards,
>       
>       Simon
>       
>       
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