[Bridge] [PATCH net] net: bridge: fdb: don't flush ext_learn entries

Nikolay Aleksandrov razor at blackwall.org
Mon Sep 28 15:30:02 UTC 2020

From: Nikolay Aleksandrov <nikolay at nvidia.com>

When a user-space software manages fdb entries externally it should
set the ext_learn flag which marks the fdb entry as externally managed
and avoids expiring it (they're treated as static fdbs). Unfortunately
on events where fdb entries are flushed (STP down, netlink fdb flush
etc) these fdbs are also deleted automatically by the bridge. That in turn
causes trouble for the managing user-space software (e.g. in MLAG setups
we lose remote fdb entries on port flaps).
These entries are completely externally managed so we should avoid
automatically deleting them, the only exception are offloaded entries
(i.e. BR_FDB_ADDED_BY_EXT_LEARN + BR_FDB_OFFLOADED). They are flushed as

Fixes: eb100e0e24a2 ("net: bridge: allow to add externally learned entries from user-space")
Signed-off-by: Nikolay Aleksandrov <nikolay at nvidia.com>
 net/bridge/br_fdb.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
index 9db504baa094..32ac8343b0ba 100644
--- a/net/bridge/br_fdb.c
+++ b/net/bridge/br_fdb.c
@@ -413,6 +413,8 @@ void br_fdb_delete_by_port(struct net_bridge *br,
 		if (!do_all)
 			if (test_bit(BR_FDB_STATIC, &f->flags) ||
+			    (test_bit(BR_FDB_ADDED_BY_EXT_LEARN, &f->flags) &&
+			     !test_bit(BR_FDB_OFFLOADED, &f->flags)) ||
 			    (vid && f->key.vlan_id != vid))

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