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Re: RTM_NEWNEIGH



Manuel Bouyer <bouyer%antioche.eu.org@localhost> writes:

> On Thu, Dec 11, 2014 at 03:14:57AM +0000, Roy Marples wrote:
>> [...]
>> The only elephants left in the room are drivers that don't set IFF_UP before
>> LINK_STATE_UPi (hi sk(4))
>
> I don't understant this. IFF_UP should not be set by the driver; it's
> externally set to ask the driver to start operations.
> What's the problem with setting link state independantly from IFF_UP ?
> sk(4) is probably not the only driver doing this; if the link state can
> be polled independanly from packet reception (I guess all interfaces supporting
> wake on lan, or shared with an IPMI management card will, or should, do this)

But if the interface is not UP, then the driver should not be enabling
the PHY and there should be no way to get positive link status.

Still, it seems unnecessary for userland to get upset about link state
already being up when bringing an interface up.   I guess the point is
that

  assume link state is down because !IFF_UP

  ifconfig foo0 up

  assume that tracking up/down notifications leads to understanding the state

doesn't really work.   Obvious fixes would seem to be poll once after
bringing up, and having drivers send a notify of current state
immediately on being brought up.  Or sending a positive link indication
if already up when bring brought up, which seems easy and probably
broadly helpful.

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