net: mpls: Fix nexthop alive tracking on down events (61733c91) · Commits · 戴 / test

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 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: ("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>

net/mpls/af_mpls.c

+10 −3

Original line number	Diff line number	Diff line
		@@ -1269,6 +1269,8 @@ static void mpls_ifdown(struct net_device *dev, int event)
		{
		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);
		@@ -1278,9 +1280,11 @@ static void mpls_ifdown(struct net_device *dev, int event)
		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:
		@@ -1288,13 +1292,16 @@ static void mpls_ifdown(struct net_device *dev, int event)
		/* 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);
		}
		}

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