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Date: Wed, 10 Jun 2015 23:28:28 -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 1/3 v3] net: track link-status of ipv4 nexthops
On Wed, Jun 10, 2015 at 07:53:59PM -0700, Scott Feldman wrote:
> On Wed, Jun 10, 2015 at 7:37 PM, Andy Gospodarek
> <gospo@...ulusnetworks.com> wrote:
>
> > @@ -1129,7 +1142,15 @@ int fib_sync_down_dev(struct net_device *dev, int force)
> > dead++;
> > else if (nexthop_nh->nh_dev == dev &&
> > nexthop_nh->nh_scope != scope) {
> > - nexthop_nh->nh_flags |= RTNH_F_DEAD;
> > + switch (event) {
> > + case NETDEV_DOWN:
> > + case NETDEV_UNREGISTER:
> > + nexthop_nh->nh_flags |= RTNH_F_DEAD;
> > + /* fall through */
> > + case NETDEV_CHANGE:
> > + nexthop_nh->nh_flags |= RTNH_F_LINKDOWN;
> > + break;
> > + }
> > #ifdef CONFIG_IP_ROUTE_MULTIPATH
> > spin_lock_bh(&fib_multipath_lock);
> > fi->fib_power -= nexthop_nh->nh_power;
> > @@ -1139,14 +1160,22 @@ int fib_sync_down_dev(struct net_device *dev, int force)
> > dead++;
> > }
> > #ifdef CONFIG_IP_ROUTE_MULTIPATH
> > - if (force > 1 && nexthop_nh->nh_dev == dev) {
> > + if (event == NETDEV_UNREGISTER && nexthop_nh->nh_dev == dev) {
> > dead = fi->fib_nhs;
> > break;
> > }
> > #endif
> > } endfor_nexthops(fi)
> > if (dead == fi->fib_nhs) {
> > - fi->fib_flags |= RTNH_F_DEAD;
> > + switch (event) {
> > + case NETDEV_DOWN:
> > + case NETDEV_UNREGISTER:
> > + fi->fib_flags |= RTNH_F_DEAD;
> > + /* fall through */
> > + case NETDEV_CHANGE:
> > + fi->fib_flags |= RTNH_F_LINKDOWN;
>
> RTNH_F_LINKDOWN is to mark linkdown nexthop devs....why is the route
> fi being marked RTNH_F_LINKDOWN?
>
> The RTNH_F_LINKDOWN comment says:
>
> #define RTNH_F_LINKDOWN 16 /* carrier-down on nexthop */
This is done with the dead flag already. I'm actually following the
precedent already set there.
> It's a per-nh flag, not per-route flag, correct?
>
> Can you show an ECMP example with only a subset of the nexthops dev
> linkdowned? Show the ip route output after going thru some link
> down/up events on some of the nexthops devs.
Sure! This is exactly what I've been using for testing.
# ip route show
70.0.0.0/24 dev p7p1 proto kernel scope link src 70.0.0.1
80.0.0.0/24 dev p8p1 proto kernel scope link src 80.0.0.1
90.0.0.0/24 via 70.0.0.2 dev p7p1
90.0.0.0/24 via 80.0.0.2 dev p8p1 metric 10
100.0.0.0/24
nexthop via 70.0.0.2 dev p7p1 weight 1
nexthop via 80.0.0.2 dev p8p1 weight 1
192.168.56.0/24 dev p2p1 proto kernel scope link src 192.168.56.2
# # take p8p1 link down
# ip route show
70.0.0.0/24 dev p7p1 proto kernel scope link src 70.0.0.1
80.0.0.0/24 dev p8p1 proto kernel scope link src 80.0.0.1 dead linkdown
90.0.0.0/24 via 70.0.0.2 dev p7p1
90.0.0.0/24 via 80.0.0.2 dev p8p1 metric 10 dead linkdown
100.0.0.0/24
nexthop via 70.0.0.2 dev p7p1 weight 1
nexthop via 80.0.0.2 dev p8p1 weight 1 dead linkdown
192.168.56.0/24 dev p2p1 proto kernel scope link src 192.168.56.2
# ip route get 100.0.0.2
100.0.0.2 via 70.0.0.2 dev p7p1 src 70.0.0.1
cache
# ip route get 100.0.0.2
100.0.0.2 via 70.0.0.2 dev p7p1 src 70.0.0.1
cache
# # take p8p1 link up
# ip route show
70.0.0.0/24 dev p7p1 proto kernel scope link src 70.0.0.1
80.0.0.0/24 dev p8p1 proto kernel scope link src 80.0.0.1
90.0.0.0/24 via 70.0.0.2 dev p7p1
90.0.0.0/24 via 80.0.0.2 dev p8p1 metric 10
100.0.0.0/24
nexthop via 70.0.0.2 dev p7p1 weight 1
nexthop via 80.0.0.2 dev p8p1 weight 1
192.168.56.0/24 dev p2p1 proto kernel scope link src 192.168.56.2
# ip route show
100.0.0.2 via 70.0.0.2 dev p7p1 src 70.0.0.1
cache
# ip route get 100.0.0.2
100.0.0.2 via 80.0.0.2 dev p8p1 src 80.0.0.1
cache
# ip route get 100.0.0.2
100.0.0.2 via 70.0.0.2 dev p7p1 src 70.0.0.1
cache
# ip route get 100.0.0.2
100.0.0.2 via 80.0.0.2 dev p8p1 src 80.0.0.1
cache
# # you can see the round robin happening
# # take all ports p8p1 and p7p1 down
# ip route show
70.0.0.0/24 dev p7p1 proto kernel scope link src 70.0.0.1 dead linkdown
80.0.0.0/24 dev p8p1 proto kernel scope link src 80.0.0.1 dead linkdown
90.0.0.0/24 via 70.0.0.2 dev p7p1 dead linkdown
90.0.0.0/24 via 80.0.0.2 dev p8p1 metric 10 dead linkdown
100.0.0.0/24
nexthop via 70.0.0.2 dev p7p1 weight 1 dead linkdown
nexthop via 80.0.0.2 dev p8p1 weight 1 dead linkdown
192.168.56.0/24 dev p2p1 proto kernel scope link src 192.168.56.2
# ip route get 100.0.0.2
RTNETLINK answers: Network is unreachable
# ip route get 80.0.0.2
RTNETLINK answers: Network is unreachable
# ip route get 80.0.0.1
local 80.0.0.1 dev lo src 80.0.0.1
cache <local>
# ip route get 70.0.0.1
local 70.0.0.1 dev lo src 70.0.0.1
cache <local>
# # local addrs are still reachable
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