From 67e194007be08d071294456274dd53e0a04fdf90 Mon Sep 17 00:00:00 2001 From: Sabrina Dubroca Date: Mon, 13 Mar 2017 13:28:09 +0100 Subject: [PATCH] ipv6: make ECMP route replacement less greedy 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' Fixes: 27596472473a ("ipv6: fix ECMP route replacement") Signed-off-by: Sabrina Dubroca Acked-by: Nicolas Dichtel Reviewed-by: Xin Long Reviewed-by: Michal Kubecek Signed-off-by: David S. Miller --- net/ipv6/ip6_fib.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c index e4266746e4a2..d4bf2c68a545 100644 --- a/net/ipv6/ip6_fib.c +++ b/net/ipv6/ip6_fib.c @@ -923,6 +923,8 @@ 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); -- 2.30.2