net: bridge: br_fdb_external_learn_add(): always set EXT_LEARN

When userspace wants to take over a fdb entry by setting it as
EXTERN_LEARNED, we set both flags BR_FDB_ADDED_BY_EXT_LEARN and
BR_FDB_ADDED_BY_USER in br_fdb_external_learn_add().

If the bridge updates the entry later because its port changed, we clear
the BR_FDB_ADDED_BY_EXT_LEARN flag, but leave the BR_FDB_ADDED_BY_USER
flag set.

If userspace then wants to take over the entry again,
br_fdb_external_learn_add() sees that BR_FDB_ADDED_BY_USER and skips
setting the BR_FDB_ADDED_BY_EXT_LEARN flags, thus silently ignores the
update.

Fix this by always allowing to set BR_FDB_ADDED_BY_EXT_LEARN regardless
if this was a user fdb entry or not.

Fixes: 710ae7287737 ("net: bridge: Mark FDB entries that were added by user as such")
Signed-off-by: Jonas Gorski <jonas.gorski@bisdn.de>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20240903081958.29951-1-jonas.gorski@bisdn.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
index c77591e638417aff9d4672ea80194f52d42b2270..ad7a42b505ef9b9f98a44fc50bc11e39a9f1646c 100644 (file)
--- a/net/bridge/br_fdb.c
+++ b/net/bridge/br_fdb.c
@@ -1469,12 +1469,10 @@ int br_fdb_external_learn_add(struct net_bridge *br, struct net_bridge_port *p,
                        modified = true;
                }
 
-               if (test_bit(BR_FDB_ADDED_BY_EXT_LEARN, &fdb->flags)) {
+               if (test_and_set_bit(BR_FDB_ADDED_BY_EXT_LEARN, &fdb->flags)) {
                        /* Refresh entry */
                        fdb->used = jiffies;
-               } else if (!test_bit(BR_FDB_ADDED_BY_USER, &fdb->flags)) {
-                       /* Take over SW learned entry */
-                       set_bit(BR_FDB_ADDED_BY_EXT_LEARN, &fdb->flags);
+               } else {
                        modified = true;
                }