4.9-stable review patch. If anyone has any objections, please let me know.
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From: Xin Long lucien.xin@gmail.com
[ 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 jishi@redhat.com Signed-off-by: Xin Long lucien.xin@gmail.com Acked-by: David Ahern dsa@cumulusnetworks.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv4/fib_semantics.c | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-)
--- a/net/ipv4/fib_semantics.c +++ b/net/ipv4/fib_semantics.c @@ -1611,18 +1611,20 @@ void fib_select_multipath(struct fib_res 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