netdev - [PATCH net V2] net: bridge: br_fdb_external_learn_add(): always set EXT

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Message-ID: <20240903081958.29951-1-jonas.gorski@bisdn.de>
Date: Tue,  3 Sep 2024 10:19:57 +0200
From: Jonas Gorski <jonas.gorski@...dn.de>
To: Roopa Prabhu <roopa@...dia.com>,
	Nikolay Aleksandrov <razor@...ckwall.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Ido Schimmel <idosch@...lanox.com>,
	Petr Machata <petrm@...lanox.com>
Cc: bridge@...ts.linux.dev,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH net V2] 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@...dn.de>
---
Changelog:
V2:
 * always allow setting EXT_LEARN regardless if user entry
 * reworded the commit message a bit to match the new behavior
 * dropped the redundant code excerpt from the commit message as it's
   already in the context

 net/bridge/br_fdb.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
index c77591e63841..ad7a42b505ef 100644
--- 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;
 		}
 
-- 
2.46.0


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