netdev - Re: [PATCH net-next 0/3 v3] changes to make ipv4 routing table aware of next-hop link status

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Date:	Thu, 11 Jun 2015 14:17:24 -0400
From:	Andy Gospodarek <gospo@...ulusnetworks.com>
To:	Scott Feldman <sfeldma@...il.com>
Cc:	Netdev <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>, ddutt@...ulusnetworks.com,
	Alexander Duyck <alexander.duyck@...il.com>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	"stephen@...workplumber.org" <stephen@...workplumber.org>
Subject: Re: [PATCH net-next 0/3 v3] changes to make ipv4 routing table aware
 of next-hop link status

On Thu, Jun 11, 2015 at 08:44:55AM -0700, Scott Feldman wrote:
> On Wed, Jun 10, 2015 at 8:19 PM, Andy Gospodarek
> <gospo@...ulusnetworks.com> wrote:
> > On Wed, Jun 10, 2015 at 08:07:10PM -0700, Scott Feldman wrote:
> >> On Wed, Jun 10, 2015 at 7:37 PM, Andy Gospodarek
> >> <gospo@...ulusnetworks.com> wrote:
> >>
> >> > There was also a request for switchdev support for this, but that will be
> >> > posted as a followup as switchdev does not currently handle dead
> >> > next-hops in a multi-path case and I felt that infra needed to be added
> >> > first.
> >>
> >> That's not true.  switchdev_fib_ipv4_add() passes *fi and all of the
> >> nexthops for the route are hanging off of that, including the
> >> nh->flags where you're setting LINKDOWN.  Multipath is not different
> >> than singlepath in that regard.  Same API for both.
> >
> > The API is the same, but I did not see a path that would take a
> > multipath route and update the dead nexthops when an interface is taken
> > down with switchdev or rocker today.
> >
> > I could be wrong (and I will test again), but create a multipath route
> > with nexthops on swp1 and swp2 and then call 'ip link set swp1 down' and
> > let me know if you see rocker's ECMP routes get updated so only the
> > nexthop on swp2 will be used.
> 
> I don't have ecmp support in rocker yet, but switchdev should be ready
> for ecmp.  I tried the test you suggest and switchdev is calling into
> the driver with updates to the routes with nhs marked DEAD.  So maybe
> your patchset is switchdev-ready?  I'd have to apply your patch to
> test. I'll wait for your v4 to address sysctl naming.

That isn't exactly what I expected by inspection, so I'm pleasantly
surprised.  I'll hold off on the excitement until I get v4 out (which
should be shortly as the request should not be too bad to resolve).

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