Patch "ipv6: make ECMP route replacement less greedy" has been added to the 4.4-stable tree

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

ipv6: make ECMP route replacement less greedy

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ipv6-make-ecmp-route-replacement-less-greedy.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Sabrina Dubroca <[email protected]>
Date: Mon, 13 Mar 2017 13:28:09 +0100
Subject: ipv6: make ECMP route replacement less greedy

From: Sabrina Dubroca <[email protected]>

[ Upstream commit 67e194007be08d071294456274dd53e0a04fdf90 ]

Commit 27596472473a ("ipv6: fix ECMP route replacement") introduced a loop that removes all siblings of an ECMP route that is being replaced. However, this loop doesn't stop when it has replaced siblings, and keeps removing other routes with a higher metric. We also end up triggering the WARN_ON after the loop, because after this nsiblings < 0.

Instead, stop the loop when we have taken care of all routes with the same metric as the route being replaced.

Reproducer:
===========
#!/bin/sh

ip netns add ns1
ip netns add ns2
ip -net ns1 link set lo up

for x in 0 1 2 ; do
ip link add veth$x netns ns2 type veth peer name eth$x netns ns1 ip -net ns1 link set eth$x up
ip -net ns2 link set veth$x up
done

ip -net ns1 -6 r a 2000::/64 nexthop via fe80::0 dev eth0 \
nexthop via fe80::1 dev eth1 nexthop via fe80::2 dev eth2
ip -net ns1 -6 r a 2000::/64 via fe80::42 dev eth0 metric 256 ip -net ns1 -6 r a 2000::/64 via fe80::43 dev eth0 metric 2048

echo "before replace, 3 routes"
ip -net ns1 -6 r | grep -v '^fe80\|^ff00'
echo

ip -net ns1 -6 r c 2000::/64 nexthop via fe80::4 dev eth0 \
nexthop via fe80::5 dev eth1 nexthop via fe80::6 dev eth2

echo "after replace, only 2 routes, metric 2048 is gone" ip -net ns1 -6 r | grep -v '^fe80\|^ff00'

---
 net/ipv6/ip6_fib.c |    2 ++
 1 file changed, 2 insertions(+)

@@ -903,6 +903,8 @@ add:
 			ins = &rt->dst.rt6_next;
 			iter = *ins;
 			while (iter) {
+				if (iter->rt6i_metric > rt->rt6i_metric)
+					break;
 				if (rt6_qualify_for_ecmp(iter)) {
 					*ins = iter->dst.rt6_next;
 					fib6_purge_rt(iter, fn, info->nl_net);

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/ipv6-make-ecmp-route-replacement-less-greedy.patch