From 233ba28e186284638b7946d886b18ad084710c31 Mon Sep 17 00:00:00 2001 From: Xin Long Date: Sun, 1 Apr 2018 22:40:35 +0800 Subject: [PATCH] route: check sysctl_fib_multipath_use_neigh earlier than hash [ Upstream commit 6174a30df1b902e1fedbd728f5343937e83e64e6 ] Prior to this patch, when one packet is hashed into path [1] (hash <= nh_upper_bound) and it's neigh is dead, it will try path [2]. However, if path [2]'s neigh is alive but it's hash > nh_upper_bound, it will not return this alive path. This packet will never be sent even if path [2] is alive. 3.3.3.1/24: nexthop via 1.1.1.254 dev eth1 weight 1 <--[1] (dead neigh) nexthop via 2.2.2.254 dev eth2 weight 1 <--[2] With sysctl_fib_multipath_use_neigh set is supposed to find an available path respecting to the l3/l4 hash. But if there is no available route with this hash, it should at least return an alive route even with other hash. This patch is to fix it by processing fib_multipath_use_neigh earlier than the hash check, so that it will at least return an alive route if there is when fib_multipath_use_neigh is enabled. It's also compatible with before when there are alive routes with the l3/l4 hash. Fixes: a6db4494d218 ("net: ipv4: Consider failed nexthops in multipath routes") Reported-by: Jianlin Shi Signed-off-by: Xin Long Acked-by: David Ahern Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv4/fib_semantics.c | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-) diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c index 1ee6c0d8dde4..f39955913d3f 100644 --- a/net/ipv4/fib_semantics.c +++ b/net/ipv4/fib_semantics.c @@ -1755,18 +1755,20 @@ void fib_select_multipath(struct fib_result *res, int hash) bool first = false; for_nexthops(fi) { + if (net->ipv4.sysctl_fib_multipath_use_neigh) { + if (!fib_good_nh(nh)) + continue; + if (!first) { + res->nh_sel = nhsel; + first = true; + } + } + if (hash > atomic_read(&nh->nh_upper_bound)) continue; - if (!net->ipv4.sysctl_fib_multipath_use_neigh || - fib_good_nh(nh)) { - res->nh_sel = nhsel; - return; - } - if (!first) { - res->nh_sel = nhsel; - first = true; - } + res->nh_sel = nhsel; + return; } endfor_nexthops(fi); } #endif -- 2.20.1