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Message-ID: <5554F073.4080501@6wind.com>
Date: Thu, 14 May 2015 20:58:59 +0200
From: Nicolas Dichtel <nicolas.dichtel@...nd.com>
To: Michal Kubecek <mkubecek@...e.cz>,
"David S. Miller" <davem@...emloft.net>
CC: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
Alexey Kuznetsov <kuznet@....inr.ac.ru>,
James Morris <jmorris@...ei.org>,
Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
Patrick McHardy <kaber@...sh.net>,
roopa <roopa@...ulusnetworks.com>
Subject: Re: [PATCH net v2 2/2] ipv6: fix ECMP route replacement
Le 13/05/2015 21:59, Michal Kubecek a écrit :
> When replacing an IPv6 multipath route with "ip route replace", i.e.
> NLM_F_CREATE | NLM_F_REPLACE, fib6_add_rt2node() replaces only first
> matching route without fixing its siblings, resulting in corrupted
> siblings linked list; removing one of the siblings can then end in an
> infinite loop.
>
> Replacing the whole set of nexthops does IMHO make more sense than
> replacing a random one. We also need to remove the NLM_F_REPLACE flag
> after replacing old nexthops by first new so that each subsequent
> nexthop does not replace previous one.
>
> Fixes: 51ebd3181572 ("ipv6: add support of equal cost multipath (ECMP)")
> Signed-off-by: Michal Kubecek <mkubecek@...e.cz>
> ---
> net/ipv6/ip6_fib.c | 17 ++++++++++++++---
> net/ipv6/route.c | 8 +++++---
> 2 files changed, 19 insertions(+), 6 deletions(-)
>
> diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
> index 96dbffff5a24..abf4e4e5bdab 100644
> --- a/net/ipv6/ip6_fib.c
> +++ b/net/ipv6/ip6_fib.c
> @@ -815,6 +815,8 @@ add:
> }
>
> } else {
> + struct rt6_info *next;
> +
> if (!found) {
> if (add)
> goto add;
> @@ -828,15 +830,24 @@ add:
>
> *ins = rt;
> rt->rt6i_node = fn;
> - rt->dst.rt6_next = iter->dst.rt6_next;
> +
> + /* skip potential siblings */
> + next = iter->dst.rt6_next;
> + while (next && next->rt6i_metric == rt->rt6i_metric)
> + next = next->dst.rt6_next;
I wonder if we should not loop over the siblings list here (rt->rt6i_siblings).
Only routes that match 'rt6_qualify_for_ecmp()' are siblings.
> + rt->dst.rt6_next = next;
> +
> atomic_inc(&rt->rt6i_ref);
> inet6_rt_notify(RTM_NEWROUTE, rt, info);
> if (!(fn->fn_flags & RTN_RTINFO)) {
> info->nl_net->ipv6.rt6_stats->fib_route_nodes++;
> fn->fn_flags |= RTN_RTINFO;
> }
> - fib6_purge_rt(iter, fn, info->nl_net);
> - rt6_release(iter);
> + while (iter != next) {
> + fib6_purge_rt(iter, fn, info->nl_net);
> + rt6_release(iter);
> + iter = iter->dst.rt6_next;
> + }
Same here.
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