From 87c0286a07f93edc874c861a9159e586fc51ee6b Mon Sep 17 00:00:00 2001 From: David Ahern Date: Fri, 10 Mar 2017 14:11:39 -0800 Subject: [PATCH] mpls: Do not decrement alive counter for unregister events [ Upstream commit 79099aab38c8f5c746748b066ae74ba984fe2cc8 ] Multipath routes can be rendered usesless when a device in one of the paths is deleted. For example: $ ip -f mpls ro ls 100 nexthop as to 200 via inet 172.16.2.2 dev virt12 nexthop as to 300 via inet 172.16.3.2 dev br0 101 nexthop as to 201 via inet6 2000:2::2 dev virt12 nexthop as to 301 via inet6 2000:3::2 dev br0 $ ip li del br0 When br0 is deleted the other hop is not considered in mpls_select_multipath because of the alive check -- rt_nhn_alive is 0. rt_nhn_alive is decremented once in mpls_ifdown when the device is taken down (NETDEV_DOWN) and again when it is deleted (NETDEV_UNREGISTER). For a 2 hop route, deleting one device drops the alive count to 0. Since devices are taken down before unregistering, the decrement on NETDEV_UNREGISTER is redundant. Fixes: c89359a42e2a4 ("mpls: support for dead routes") Signed-off-by: David Ahern Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/mpls/af_mpls.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c index 2a21ff14c07d..1309e2c34764 100644 --- a/net/mpls/af_mpls.c +++ b/net/mpls/af_mpls.c @@ -956,7 +956,8 @@ static void mpls_ifdown(struct net_device *dev, int event) /* fall through */ case NETDEV_CHANGE: nh->nh_flags |= RTNH_F_LINKDOWN; - ACCESS_ONCE(rt->rt_nhn_alive) = rt->rt_nhn_alive - 1; + if (event != NETDEV_UNREGISTER) + ACCESS_ONCE(rt->rt_nhn_alive) = rt->rt_nhn_alive - 1; break; } if (event == NETDEV_UNREGISTER) -- 2.20.1