From: Stephen Hemminger <stephen@networkplumber.org>
To: Erik Kline <ek@loon.com>
Cc: "Cong Wang" <xiyou.wangcong@gmail.com>, 杜英杰 <leondyj@pku.edu.cn>,
"Linux Kernel Network Developers" <netdev@vger.kernel.org>
Subject: Re: some question about "/sys/class/net/<iface>/operstate"
Date: Wed, 11 Nov 2020 13:17:24 -0800 [thread overview]
Message-ID: <20201111131724.3ee61c26@hermes.local> (raw)
In-Reply-To: <CAAedzxoW76P7jk3k4auR+DY_829FKwVLBi6uDzn7C2Y6381=YQ@mail.gmail.com>
On Wed, 11 Nov 2020 12:34:51 -0800
Erik Kline <ek@loon.com> wrote:
> On Wed, Nov 11, 2020 at 11:55 AM Stephen Hemminger
> <stephen@networkplumber.org> wrote:
> >
> > On Wed, 11 Nov 2020 11:02:14 -0800
> > Cong Wang <xiyou.wangcong@gmail.com> wrote:
> >
> > > On Tue, Nov 10, 2020 at 8:32 PM 杜英杰 <leondyj@pku.edu.cn> wrote:
> > > >
> > > > I want to use inotify to monitor /sys/class/net//operstate to detect status of a iface in real time.
> > > > when I ifdown && ifup eth3, the content of operstate changed, but the file's Modify time didn't change.
> > > > I don't know the reason, is there any file which can be monitored by inotify to get iface status in real time?
> > > > Much appreciation for any advice!
> > >
> > > You need to listen to netdev netlink messages for changes like
> > > this. These messages are generated in real-time.
> >
> > The /sys and /proc are pseudo-filesystems. The file modify time and inotify do not work
> > as expected on these files. Cong is right you need to use netlink for this.
>
> Related question: could/should modify time and/or inotify be made to
> work? I genuinely don't know if that would even be possible (separate
> from "desirable").
The problem is lots of data changes in /proc and /sys all the time, like every counter
value. So having any kind of notification would be a major performance hit.
prev parent reply other threads:[~2020-11-11 21:17 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-11 4:31 some question about "/sys/class/net/<iface>/operstate" 杜英杰
2020-11-11 19:02 ` Cong Wang
2020-11-11 19:55 ` Stephen Hemminger
2020-11-11 20:34 ` Erik Kline
2020-11-11 21:17 ` Stephen Hemminger [this message]
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