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Date: Mon, 20 Mar 2017 18:49:12 +0100 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Sabrina Dubroca <sd@...asysnail.net>, Nicolas Dichtel <nicolas.dichtel@...nd.com>, Xin Long <lucien.xin@...il.com>, Michal Kubecek <mkubecek@...e.cz>, "David S. Miller" <davem@...emloft.net> Subject: [PATCH 4.4 17/28] ipv6: make ECMP route replacement less greedy 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Sabrina Dubroca <sd@...asysnail.net> [ 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' Fixes: 27596472473a ("ipv6: fix ECMP route replacement") Signed-off-by: Sabrina Dubroca <sd@...asysnail.net> Acked-by: Nicolas Dichtel <nicolas.dichtel@...nd.com> Reviewed-by: Xin Long <lucien.xin@...il.com> Reviewed-by: Michal Kubecek <mkubecek@...e.cz> Signed-off-by: David S. Miller <davem@...emloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- net/ipv6/ip6_fib.c | 2 ++ 1 file changed, 2 insertions(+) --- a/net/ipv6/ip6_fib.c +++ b/net/ipv6/ip6_fib.c @@ -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);
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