From: Stephen Hemminger <shemminger@vyatta•com>
To: Arvid Brodin <Arvid.Brodin@xdin•com>
Cc: "netdev@vger•kernel.org" <netdev@vger•kernel.org>
Subject: Re: Netlink for kernel<->user space communication?
Date: Mon, 7 May 2012 15:33:07 -0700 [thread overview]
Message-ID: <20120507153307.551b29ed@nehalam.linuxnetplumber.net> (raw)
In-Reply-To: <4FA817C8.9040204@xdin.com>
On Mon, 7 May 2012 18:43:23 +0000
Arvid Brodin <Arvid.Brodin@xdin•com> wrote:
> On Tue, 24 Apr 2012 16:57:55 -0700
> Stephen Hemminger <shemminger@xxxxxxxxxx> wrote:
> > On Tue, 24 Apr 2012 23:52:34 +0000
> > Arvid Brodin <Arvid.Brodin@xxxxxxxx> wrote:
> >
> >> Hi.
> >>
> >> I'm writing a kernel driver for the HSR protocol, a standard for high availability
> >> networks. I want to send messages from the kernel to user space about broken network
> >> links. I also want user space to be able to ask the kernel about its view of the status of
> >> nodes on the network.
> >>
> >> Netlink seems like a good tool for this. (Is it?)
> >
> > Yes.
> >
> >> But do I use raw netlink? (Described here: http://www.linuxjournal.com/article/7356 - but
> >> this seems a bit out of date, the kernel API description differs from today's kernel
> >> implementation.)
> >
> > No. Your driver probably looks like a device so you should be
> > using rtnetlink messages.
>
> I'm already using rtnetlink messages to add and remove my device, which works fine (see
> e.g. http://www.spinics.net/lists/netdev/msg192817.html - although I didn't think it
> meaningful to include the iproute2 patch here, until the kernel part is ready).
>
> The protocol specifies transmission of "supervision frames" every 2 seconds, e.g. to check
> link integrity. Every such frame should be received from two directions in the ring - if
> only one is received, then there is a link problem.
Why not just manipulate the carrier or operational state (see Documentation/networking/operstate)
and use the existing notification on link changes. If you don't get heartbeat then change
the state of the device to indicate lower device is down with set_operstate(), the necessary
link everts propgate back as netlink events.
> I'd like to notify user space about every such occurence. Is there a rtnetlink message
> type that fits this? The stuff in rtnetlink.h seems to be mostly concerned with specific
> user space commands (there is something called RTNLGRP_NOTIFY but I couldn't find any
> instances of it being used in the kernel, nor any documentation).
>
I am trying to steer you to use existing API's because then existing programs and
infrastructure can deal with the new device type.
next prev parent reply other threads:[~2012-05-07 22:33 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-07 18:43 Netlink for kernel<->user space communication? Arvid Brodin
2012-05-07 22:33 ` Stephen Hemminger [this message]
2012-05-09 23:32 ` Arvid Brodin
2012-05-10 16:36 ` Stephen Hemminger
-- strict thread matches above, loose matches on Subject: below --
2012-04-24 23:52 Arvid Brodin
2012-04-24 23:57 ` Stephen Hemminger
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