[PATCH] ifplugd: Allow ENODEV when upping interface for -M

[Jate Sujjavanich]

I was finally able to try out the commit in busybox master. The patch
worked.

On Fri, Aug 19, 2016 at 9:40 AM, Denys Vlasenko <vda.linux at googlemail.com>
wrote:

> Fixed in git, please try it.
>
> On Thu, Aug 18, 2016 at 10:00 PM, Jate Sujjavanich <jatedev at gmail.com>
> wrote:
> > I am able to reproduce the issue on my system consistently. I'm using
> > modprobe to remove the driver for g_ether on my ARM system. Using strace
> > reduces the frequency of the bug, but it still occurs.
> >
> > Here's the output from strace:
> >
> > 14:50:53.886676 ioctl(3, SIOCGIFFLAGS, {ifr_name="usb0",
> > ifr_flags=IFF_BROADCAS
> > T|IFF_MULTICAST}) = 0
> > 14:50:53.887140 write(2, "ifplugd(usb0): upping interface\n",
> > 32ifplugd(usb0):
> > upping interface
> > ) = 32
> > 14:50:53.887584 gettimeofday({1471546253, 887734}, NULL) = 0
> > 14:50:53.888011 send(5, "<27>Aug 18 14:50:53 ifplugd(usb0"..., 52,
> > MSG_NOSIGNAL
> > ) = 52
> > 14:50:53.888431 ioctl(3, SIOCSIFFLAGS, {ifr_name="usb0", ???}) = -1
> ENODEV
> > (No
> > such device)
> > 14:50:53.895989 write(2, "ifplugd(usb0): setting interface"...,
> > 62ifplugd(usb0)
> > : setting interface flags failed: No such device
> > ) = 62
> >
> >
> > On Tue, Aug 16, 2016 at 7:52 PM, Denys Vlasenko <
> vda.linux at googlemail.com>
> > wrote:
> >>
> >> On Thu, Aug 11, 2016 at 5:21 PM, Jate Sujjavanich <jatedev at gmail.com>
> >> wrote:
> >> > The following changes since commit
> >> > 150dc7a2b483b8338a3e185c478b4b23ee884e71:
> >> >
> >> >   ntpd: respond only to client and symmetric active packets
> (2016-08-01
> >> > 20:25:06 +0200)
> >> >
> >> > are available in the git repository at:
> >> >
> >> >   https://github.com/jatedev/busybox work-ifplugd-device-detect
> >> >
> >> > for you to fetch changes up to a5d29d0cc0ff79214465a66fc8cd49
> 757bf72064:
> >> >
> >> >   ifplugd: Allow ENODEV when upping interface for -M (2016-08-11
> >> > 11:09:21
> >> > -0400)
> >> >
> >> > ----------------------------------------------------------------
> >> > Jate Sujjavanich (1):
> >> >       ifplugd: Allow ENODEV when upping interface for -M
> >> >
> >> >  networking/ifplugd.c |    6 +++++-
> >> >  1 file changed, 5 insertions(+), 1 deletion(-)
> >> >
> >> > diff --git a/networking/ifplugd.c b/networking/ifplugd.c
> >> > index 28c49e2..67251ae 100644
> >> > --- a/networking/ifplugd.c
> >> > +++ b/networking/ifplugd.c
> >> > @@ -359,7 +359,11 @@ static void up_iface(void)
> >> >                 /* Let user know we mess up with interface */
> >> >                 bb_error_msg("upping interface");
> >> >                 if (network_ioctl(SIOCSIFFLAGS, &ifrequest, "setting
> >> > interface flags") < 0)
> >> > -                       xfunc_die();
> >> > +                       if (errno == ENODEV) {
> >> > +                               G.iface_exists = 0;
> >> > +                               return;
> >> > +                       } else
> >> > +                               xfunc_die();
> >> >         }
> >>
> >> This makes sense. But...
> >>
> >>         set_ifreq_to_ifname(&ifrequest);
> >>         if (network_ioctl(SIOCGIFFLAGS, &ifrequest, "getting interface
> >> flags") < 0) {
> >>                 G.iface_exists = 0;
> >>                 return;
> >>         }
> >>
> >>         if (!(ifrequest.ifr_flags & IFF_UP)) {
> >>                 ifrequest.ifr_flags |= IFF_UP;
> >>                 /* Let user know we mess up with interface */
> >>                 bb_error_msg("upping interface");
> >>                 if (network_ioctl(SIOCSIFFLAGS, &ifrequest, "setting
> >> interface flags") < 0) {
> >>
> >>
> >>
> >> I just wonder, how on Earth SIOCGIFFLAGS just above did _not_ fail?
> >> The iface deletion race? Very tight, almost impossible to hit...
> >
> >
>
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