netdev - Re: followup: what's responsible for setting netdev->operstate to IF_OPER

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Message-ID: <alpine.LFD.2.21.1808270221470.11581@localhost.localdomain>
Date:   Mon, 27 Aug 2018 02:22:22 -0400 (EDT)
From:   "Robert P. J. Day" <rpjday@...shcourse.ca>
To:     Stephen Hemminger <stephen@...workplumber.org>
cc:     Linux kernel netdev mailing list <netdev@...r.kernel.org>
Subject: Re: followup: what's responsible for setting netdev->operstate to
 IF_OPER_DOWN?

On Sun, 26 Aug 2018, Stephen Hemminger wrote:

> On Sun, 26 Aug 2018 11:14:33 -0400 (EDT)
> "Robert P. J. Day" <rpjday@...shcourse.ca> wrote:
>
> >   apologies for the constant pleas for assistance, but i think i'm
> > zeroing in on the problem that started all this. recap: custom
> > FPGA-based linux box with multiple ports, where the current symptom is
> > that there is no userspace notification when someone simply unplugs
> > one of the ports ("ifconfig" shows that interface still RUNNING).
> >
> >   as i read it, an active ethernet interface should be both UP (the
> > administrative state) and RUNNING (the RFC 2863-defined operational
> > state). if i unplug, i've verified on a standard net port on my laptop
> > that the interface is still UP, but no longer RUNNING, which makes
> > perfect sense. i plug back in, interface starts RUNNING again. so
> > where's the problem?
> >
> >   i can see that whether ifconfig shows an interface RUNNING is
> > defined in net/core/dev.c:
> >
> >   unsigned int dev_get_flags(const struct net_device *dev)
> >   {
> >         unsigned int flags;
> >
> >         flags = (dev->flags & ~(IFF_PROMISC |
> >                                 IFF_ALLMULTI |
> >                                 IFF_RUNNING |
> >                                 IFF_LOWER_UP |
> >                                 IFF_DORMANT)) |
> >                 (dev->gflags & (IFF_PROMISC |
> >                                 IFF_ALLMULTI));
> >
> >         if (netif_running(dev)) {
> >                 if (netif_oper_up(dev))
> >                         flags |= IFF_RUNNING;  <---- THERE
> >                 if (netif_carrier_ok(dev))
> >                         flags |= IFF_LOWER_UP;
> >                 if (netif_dormant(dev))
> >                         flags |= IFF_DORMANT;
> >         }
> >
> >         return flags;
> >   }
> >
> > where netif_oper_up() is defined as:
> >
> >   static inline bool netif_oper_up(const struct net_device *dev)
> >   {
> >         return (dev->operstate == IF_OPER_UP ||
> >                 dev->operstate == IF_OPER_UNKNOWN /* backward compat */);
> >   }
> >
> > so i am simply assuming that the underlying problem is that,
> > somewhere down below, the unplugging of a port is somehow not setting
> > dev->operstate to its proper value of IF_OPER_DOWN.
> >
> >   that would clearly explain everything, and i'm about to dig even
> > further to see where the event of unplugging a port *should* be
> > recognized, but does this sound like a reasonable diagnosis? there
> > have been other problems with the programming of the FPGA, so it would
> > surprise absolutely no one to learn that this aspect was
> > misprogrammed.
> >
> > rday
> >
>
> There is no reason drivers should ever muck with flags directly.
> You probably are looking for netif_detach

  i assume you mean netif_device_detach; i'll check into that.

rday

-- 

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Robert P. J. Day                                 Ottawa, Ontario, CANADA
                  http://crashcourse.ca/dokuwiki

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