From 27596472473a02cfef2908a6bcda7e55264ba6b7 Mon Sep 17 00:00:00 2001 From: Michal Kubeček Date: Mon, 18 May 2015 20:54:00 +0200 Subject: ipv6: fix ECMP route replacement 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. IPv6 ECMP implementation is a bit different from IPv4 so that route replacement cannot work in exactly the same way. This should be a reasonable approximation: 1. If the new route is ECMP-able and there is a matching ECMP-able one already, replace it and all its siblings (if any). 2. If the new route is ECMP-able and no matching ECMP-able route exists, replace first matching non-ECMP-able (if any) or just add the new one. 3. If the new route is not ECMP-able, replace first matching non-ECMP-able route (if any) or add the new route. We also need to remove the NLM_F_REPLACE flag after replacing old route(s) by first nexthop of an ECMP route 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 Acked-by: Nicolas Dichtel Signed-off-by: David S. Miller --- net/ipv6/route.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) (limited to 'net/ipv6/route.c') diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 3821a3517478..c73ae5039e46 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -2541,11 +2541,14 @@ beginning: } } /* Because each route is added like a single route we remove - * this flag after the first nexthop (if there is a collision, - * we have already fail to add the first nexthop: - * fib6_add_rt2node() has reject it). + * these flags after the first nexthop: if there is a collision, + * we have already failed to add the first nexthop: + * fib6_add_rt2node() has rejected it; when replacing, old + * nexthops have been replaced by first new, the rest should + * be added to it. */ - cfg->fc_nlinfo.nlh->nlmsg_flags &= ~NLM_F_EXCL; + cfg->fc_nlinfo.nlh->nlmsg_flags &= ~(NLM_F_EXCL | + NLM_F_REPLACE); rtnh = rtnh_next(rtnh, &remaining); } -- cgit v1.2.3-59-g8ed1b