netdev - Re: [PATCH] net: mpls: Fix nexthop alive tracking on down events

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Date:   Tue, 14 Mar 2017 10:29:16 +0000
From:   Robert Shearman <rshearma@...cade.com>
To:     David Ahern <dsa@...ulusnetworks.com>, <netdev@...r.kernel.org>
CC:     <roopa@...ulusnetworks.com>
Subject: Re: [PATCH] net: mpls: Fix nexthop alive tracking on down events

On 13/03/17 23:49, David Ahern wrote:
> Alive tracking of nexthops can account for a link twice if the carrier
> goes down followed by an admin down of the same link rendering multipath
> routes useless. This is similar to 79099aab38c8 for UNREGISTER events and
> DOWN events.
>
> Fix by tracking number of alive nexthops in mpls_ifdown similar to the
> logic in mpls_ifup. Checking the flags per nexthop once after all events
> have been processed is simpler than trying to maintian a running count
> through all event combinations.
>
> Also, WRITE_ONCE is used instead of ACCESS_ONCE to set rt_nhn_alive
> per a comment from checkpatch:
>     WARNING: Prefer WRITE_ONCE(<FOO>, <BAR>) over ACCESS_ONCE(<FOO>) = <BAR>
>
> Fixes: c89359a42e2a4 ("mpls: support for dead routes")
> Signed-off-by: David Ahern <dsa@...ulusnetworks.com>

Acked-by: Robert Shearman <rshearma@...cade.com>