From 8b8e0dd357165e0258d9f9cdab5366720ed2f619 Mon Sep 17 00:00:00 2001 From: Ido Schimmel Date: Wed, 2 Apr 2025 14:42:24 +0300 Subject: [PATCH] ipv6: Do not consider link down nexthops in path selection Nexthops whose link is down are not supposed to be considered during path selection when the "ignore_routes_with_linkdown" sysctl is set. This is done by assigning them a negative region boundary. However, when comparing the computed hash (unsigned) with the region boundary (signed), the negative region boundary is treated as unsigned, resulting in incorrect nexthop selection. Fix by treating the computed hash as signed. Note that the computed hash is always in range of [0, 2^31 - 1]. Fixes: 3d709f69a3e7 ("ipv6: Use hash-threshold instead of modulo-N") Signed-off-by: Ido Schimmel Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/20250402114224.293392-3-idosch@nvidia.com Signed-off-by: Jakub Kicinski --- net/ipv6/route.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 864f0002034b..ab12b816ab94 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -442,6 +442,7 @@ void fib6_select_path(const struct net *net, struct fib6_result *res, { struct fib6_info *first, *match = res->f6i; struct fib6_info *sibling; + int hash; if (!match->nh && (!match->fib6_nsiblings || have_oif_match)) goto out; @@ -468,7 +469,8 @@ void fib6_select_path(const struct net *net, struct fib6_result *res, if (!first) goto out; - if (fl6->mp_hash <= atomic_read(&first->fib6_nh->fib_nh_upper_bound) && + hash = fl6->mp_hash; + if (hash <= atomic_read(&first->fib6_nh->fib_nh_upper_bound) && rt6_score_route(first->fib6_nh, first->fib6_flags, oif, strict) >= 0) { match = first; @@ -481,7 +483,7 @@ void fib6_select_path(const struct net *net, struct fib6_result *res, int nh_upper_bound; nh_upper_bound = atomic_read(&nh->fib_nh_upper_bound); - if (fl6->mp_hash > nh_upper_bound) + if (hash > nh_upper_bound) continue; if (rt6_score_route(nh, sibling->fib6_flags, oif, strict) < 0) break;