On Sun, 26 Aug 2018 11:14:33 -0400 (EDT)
"Robert P. J. Day" <rpj...@crashcourse.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
