[Bridge] [PATCH net-next] net: bridge: optimize backup_port fdb convergence

Nikolay Aleksandrov nikolay at cumulusnetworks.com
Wed Apr 3 10:49:24 UTC 2019

We can optimize the fdb convergence when a backup_port is present by not
immediately flushing the entries of the stopped port since traffic for
those entries will flow towards the backup_port.

There are 2 cases specifically that benefit most:
- when the stopped port comes up before the entries expire by themselves
- when there's an external entry refresh and they're kept while the
  backup_port is operating (e.g. mlag)

Signed-off-by: Nikolay Aleksandrov <nikolay at cumulusnetworks.com>
We have been running with this change for over an year, it has been
extensively tested.

 net/bridge/br_stp_if.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c
index 808e2b914015..8d65ae5210e0 100644
--- a/net/bridge/br_stp_if.c
+++ b/net/bridge/br_stp_if.c
@@ -117,7 +117,8 @@ void br_stp_disable_port(struct net_bridge_port *p)
-	br_fdb_delete_by_port(br, p, 0, 0);
+	if (!rcu_access_pointer(p->backup_port))
+		br_fdb_delete_by_port(br, p, 0, 0);

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