[ovs-dev] [PATCH] dpif-netdev: Do not mix recirculation depth into RSS hash itself.

Ilya Maximets i.maximets at ovn.org
Thu Oct 24 12:32:11 UTC 2019

Mixing of RSS hash with recirculation depth is useful for flow lookup
because same packet after recirculation should match with different
datapath rule.  Setting of the mixed value back to the packet is
completely unnecessary because recirculation depth is different on
each recirculation, i.e. we will have different packet hash for
flow lookup anyway.

This should fix the issue that packets from the same flow could be
directed to different buckets based on a dp_hash or different ports of
a balanced bonding in case they were recirculated different number of
times (e.g. due to conntrack rules).
With this change, the original RSS hash will remain the same making
it possible to calculate equal dp_hash values for such packets.

Reported-at: https://mail.openvswitch.org/pipermail/ovs-dev/2019-September/363127.html
Fixes: 048963aa8507 ("dpif-netdev: Reset RSS hash when recirculating.")
Signed-off-by: Ilya Maximets <i.maximets at ovn.org>
 lib/dpif-netdev.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
index 4546b55e8..c09b8fd95 100644
--- a/lib/dpif-netdev.c
+++ b/lib/dpif-netdev.c
@@ -6288,7 +6288,6 @@ dpif_netdev_packet_get_rss_hash(struct dp_packet *packet,
     recirc_depth = *recirc_depth_get_unsafe();
     if (OVS_UNLIKELY(recirc_depth)) {
         hash = hash_finish(hash, recirc_depth);
-        dp_packet_set_rss_hash(packet, hash);
     return hash;

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