RTNet and setsockopt

Per Oberg pero at wolfram.com
Thu Apr 16 20:04:38 CEST 2020


----- Den 16 apr 2020, på kl 19:00, xenomai xenomai at xenomai.org skrev:
> ----- Den 16 apr 2020, på kl 18:32, Lange Norbert norbert.lange at andritz.com
> skrev:

> > Hello Per,

> > setsockopt is supported by rtnet (and wrapped with the POSIX skin). That said,
> > it supports very little options you are used from Linux. Do a grep -r on
> > xenomais sources.
> > Xenomai mostly uses ioctls for bringing up Interfaces, etc.

> > There are subtile differences and limitations aswell. I am pretty sure now that
> > most operations
> > are behaving like you have an nonblocking filedescriptor / socket. The RT focus
> > means that there
> > typically is just a check if buffers are available, and no effort is made for
> > waiting.
> > So select will be your best friend.
> > (I am just using packet sockets, but I believe it’s the same for all of them).

> Thanks, I readded the list again. The reason I started looking into this is that
> I had issues with blocking sends. I wanted to see what happened if I pulled the
> plug on the ethernet and tried to recover afterwards.

> Digging around a bit is seems like I might actually have a compiler flag issue
> (again...). I tried compiling my network code as a shared library.

Progress, i guess. It was the read that was became non blocking.

Still: I believe that "setsockopt" is missing for PF_PACKET, SOCK_RAW. I can se that it is implemented for some of the packet types but there is no reference to it in af_packet.c.

That said, I don't see how setsockopt is mapped to the different variants. I can se how recv and recfrom is mapped using the structure with the ".recvfrom = xxx" syntax but setsockopt seems to be different.

Also, when looking in the code i see that "MSG_DONTWAIT" is supported for rt_packet_recvmsg and that it sets sock->timeout to -1. So it seems a small fix to make this work, if I only knew where how setsockopt was mapped..

> > Norbert Lange

> > > -----Original Message-----
> > > From: Xenomai <xenomai-bounces at xenomai.org> On Behalf Of Per Oberg via
> > > Xenomai
> > > Sent: Donnerstag, 16. April 2020 18:08
> > > To: xenomai <xenomai at xenomai.org>
> > > Subject: RTNet and setsockopt

> > > NON-ANDRITZ SOURCE: BE CAUTIOUS WITH CONTENT, LINKS OR
> > > ATTACHMENTS.

> > > Dear list

> > > I am "porting" a posix application using raw network packages to RTNet. The
> > > old code is trying to use setsockopt and ioctl. The calls I am trying to use are

> > > setsockopt:
> > > SO_RCVTIMEO
> > > SO_SNDTIMEO
> > > SO_DONTROUTE

> >> These return "No such device". I guess that this is because setsockopt is not
> > > rt-
> > > compatible, correct ? ( There seem to be no corresponding rt_setsockopt... )

> > > ioctl :
> > > IFF_PROMISC | IFF_BROADCAST

> > > These return "Operation not supported".

> > > My code works fairly well as it is, and I probably do not need SO_DONTROUTE,
> > > IFF_PROMISC, and IFF_BROADCAST with rtnet. I would, however, like to have
> > > SO_RCVTIMEO, SO_SNDTIMEO or nonblock. Do I need to use O_NONBLOCK
> > > together with send() instead or am I missing something ?

> > > Best Regards
> > > Per Öberg

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> Thanks
> Per Öberg

Thanks
Per Öberg 



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