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Date:      Tue, 19 Apr 2005 11:49:36 +0200
From:      Andre Oppermann <andre@freebsd.org>
To:        Gleb Smirnoff <glebius@FreeBSD.org>
Cc:        net@FreeBSD.org
Subject:   Re: if_link_state_change() patch for review
Message-ID:  <4264D430.D39B81D0@freebsd.org>
References:  <20050419064747.GC734@cell.sick.ru>

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Gleb Smirnoff wrote:
> 
>   Dear networkers,
> 
> we are working on fixing LORs in if_link_state_change() path, and
> adding possibility to call if_link_state_change() pseudorecursively,
> when link of interface depends on link of the other.
> 
> I'm posting this patch for wider review. An important point about it
> is that, if several link events occur VERY quickly, only the last one
> will be processed. I don't know of any software that will be broken by
> such behavoir. If you know some, please tell me.

I assume this is per interface and not for all interfaces together.

You have to be careful here indeed.  If the link is rapidly flapping
then you only want to report changes in status.  For example when
it going down, up, down and all these events got queued it doesn't
make sense to report down->down.  This could indeed confuse some
tools and isn't very useful.  Either you check the first event vs.
the last one if there is a change in state or you just take the events
as trigger to have a look at the interface status when the ithread
runs.  There however you'd have to track the previous state to detect
changes.

-- 
Andre



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