On Sun, 26 Aug 2018, Stephen Hemminger wrote:
> On Sun, 26 Aug 2018 11:14:33 -0400 (EDT)
> "Robert P. J. Day" <[email protected]> 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
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