[PATCH net-next 6/6] net: dsa: clear VLAN flags for CPU port

[Vivien Didelot <vivien.didelot@gmail.com>]

When the bridge offloads a VLAN on a slave port, we also need to
program its dedicated CPU port as a member of the VLAN.

Drivers may handle the CPU port's membership as they want. For example,
Marvell as a special "Unmodified" mode to pass frames as is through
such ports.

Even though DSA expects the drivers to handle the CPU port membership,
they are unlikely to program such VLANs untagged, and certainly not as
PVID. This patch clears the VLAN flags before programming the CPU port.

Signed-off-by: Vivien Didelot <vivien.didelot@gmail.com>
Suggested-by: Vladimir Oltean <olteanv@gmail.com>
---
 net/dsa/slave.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index 8267c156a51a..48df48f76c67 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -332,6 +332,12 @@ static int dsa_slave_vlan_add(struct net_device *dev,
 	if (err)
 		return err;
 
+	/* We need the dedicated CPU port to be a member of the VLAN as well.
+	 * Even though drivers often handle CPU membership in special ways,
+	 * CPU ports are likely to be tagged, so clear the VLAN flags.
+	 */
+	vlan.flags = 0;
+
 	err = dsa_port_vlan_add(dp->cpu_dp, &vlan, trans);
 	if (err)
 		return err;
-- 
2.23.0