[PATCH net-next] net: dsa: unsync host addresses when destroying user port

When a user port is destroyed while addresses are still synced to it,
e.g. multicast addresses synced by a bridge the port is a member of,
the host FDB/MDB entries these addresses installed on the CPU port are
never removed: the only removal path is dsa_user_unsync_uc()/_mc() via
ndo_set_rx_mode, and __dev_set_rx_mode() does not call the ndo on a
device which is down. By the time the bridge unsyncs its addresses in
del_nbp() during unregistration, the netdev has already been closed,
so the unsync never reaches DSA and the entries linger until
dsa_switch_release_ports() reports them:

  Cleaning up multicast address 33:33:00:00:00:01 vid 0 from port 9

This happens on every unbind of a DSA driver supporting host address
filtering while its ports are up.

Unsync the host addresses in dsa_user_destroy() before unregistering
the netdev, at a point where the driver can still process the
deletion, just like dsa_user_change_conduit() already does when
migrating host addresses to a new conduit.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
---
 net/dsa/user.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/dsa/user.c b/net/dsa/user.c
index 03c7af6abe18..a7dabb645036 100644
--- a/net/dsa/user.c
+++ b/net/dsa/user.c

@@ -2885,6 +2885,7 @@ void dsa_user_destroy(struct net_device *user_dev)
 
 	netif_carrier_off(user_dev);
 	rtnl_lock();
+	dsa_user_unsync_ha(user_dev);
 	netdev_upper_dev_unlink(conduit, user_dev);
 	unregister_netdevice(user_dev);
 	phylink_disconnect_phy(dp->pl);

-- 
2.55.0