This is a note to let you know that I've just added the patch titled

net: mpls: Fix nexthop alive tracking on down events

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: net-mpls-fix-nexthop-alive-tracking-on-down-events.patch and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Mon Dec 18 14:12:34 CET 2017

From: David Ahern dsa@cumulusnetworks.com Date: Mon, 13 Mar 2017 16:49:10 -0700 Subject: net: mpls: Fix nexthop alive tracking on down events

From: David Ahern dsa@cumulusnetworks.com

[ Upstream commit 61733c91c454a61be0ffc93fe46a5d5f2f048c1c ]

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@cumulusnetworks.com Acked-by: Robert Shearman rshearma@brocade.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin alexander.levin@verizon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/mpls/af_mpls.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-)

--- a/net/mpls/af_mpls.c +++ b/net/mpls/af_mpls.c @@ -937,6 +937,8 @@ static void mpls_ifdown(struct net_devic { struct mpls_route __rcu **platform_label; struct net *net = dev_net(dev); + unsigned int nh_flags = RTNH_F_DEAD | RTNH_F_LINKDOWN; + unsigned int alive; unsigned index;

platform_label = rtnl_dereference(net->mpls.platform_label); @@ -946,9 +948,11 @@ static void mpls_ifdown(struct net_devic if (!rt) continue;

+ alive = 0; change_nexthops(rt) { if (rtnl_dereference(nh->nh_dev) != dev) - continue; + goto next; + switch (event) { case NETDEV_DOWN: case NETDEV_UNREGISTER: @@ -956,13 +960,16 @@ static void mpls_ifdown(struct net_devic /* fall through */ case NETDEV_CHANGE: nh->nh_flags |= RTNH_F_LINKDOWN; - if (event != NETDEV_UNREGISTER) - ACCESS_ONCE(rt->rt_nhn_alive) = rt->rt_nhn_alive - 1; break; } if (event == NETDEV_UNREGISTER) RCU_INIT_POINTER(nh->nh_dev, NULL); +next: + if (!(nh->nh_flags & nh_flags)) + alive++; } endfor_nexthops(rt); + + WRITE_ONCE(rt->rt_nhn_alive, alive); } }

Patches currently in stable-queue which might be from dsa@cumulusnetworks.com are

queue-4.9/net-mpls-fix-nexthop-alive-tracking-on-down-events.patch