if_link_state_change() patch for review

[Andre Oppermann]

Gleb Smirnoff wrote:
> A> You have to be careful here indeed.  If the link is rapidly flapping
> A> then you only want to report changes in status.  For example when
> A> it going down, up, down and all these events got queued it doesn't
> A> make sense to report down->down.  This could indeed confuse some
> A> tools and isn't very useful.  Either you check the first event vs.
> A> the last one if there is a change in state or you just take the events
> A> as trigger to have a look at the interface status when the ithread
> A> runs.  There however you'd have to track the previous state to detect
> A> changes.
> 
> I do not know any applications which would be confused, yet. Also, while
> event coalescing is possible theoretically, I failed to reproduce it. I've
> added a debugging printf, so we will see if anyone experiences these
> coalescing events at all.

It doesn't really make sense, so we better don't do it and document
that fact.

-- 
Andre