netdev - Re: [PATCH v2 net-next] ipv6: router reachability probing

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Date:	Thu, 12 Dec 2013 02:26:36 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	David Miller <davem@...emloft.net>
Cc:	mkubecek@...e.cz, jbenc@...hat.com, netdev@...r.kernel.org,
	yoshfuji@...ux-ipv6.org
Subject: Re: [PATCH v2 net-next] ipv6: router reachability probing

On Wed, Dec 11, 2013 at 07:56:51PM -0500, David Miller wrote:
> From: Michal Kubecek <mkubecek@...e.cz>
> Date: Thu, 12 Dec 2013 00:12:36 +0100
> 
> > Is it really the case in current mainline kernels? In my tests, this
> > behaviour in 3.0 kernel (SLES 11 SP3) was caused by the reference held
> > by struct dst_entry which caused that in neigh_periodic_work(),
> > n->refcnt was always bigger than one so that the neighbour entry was
> > never cleaned up.  But when I tested with 3.11.6 (OpenSuSE 13.1) where
> > neighbour is no longer cached in struct dst_entry, the neighbour was
> > cleaned up eventually and new lookup was performed.
> 
> The detachment of neighbours from route entires has had many consequences,
> both desirable and undesirable.  This happens to be one of the former,
> fortunately :-)

In the end it was worth it. It fixed some very annoying bugs.

But while I wrote the previouss answer I noticed that we should actually
move the state of the probes from neigh->update to the rt6_info structure
as we cannot guarantee it will survive the 60 seconds in failed state. :/

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