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

[Denys Vlasenko]

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 a5d29d0cc0ff79214465a66fc8cd49757bf72064:
>
>   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...