netdev - [PATCH net-next 2/2] net: dsa: sja1105: Clear VLAN filtering offload netdev feature

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Date:   Sun, 25 Aug 2019 22:46:30 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     f.fainelli@...il.com, vivien.didelot@...il.com, andrew@...n.ch,
        davem@...emloft.net
Cc:     netdev@...r.kernel.org, Vladimir Oltean <olteanv@...il.com>
Subject: [PATCH net-next 2/2] net: dsa: sja1105: Clear VLAN filtering offload netdev feature

The switch barely supports traffic I/O, and it does that by repurposing
VLANs when there is no bridge that is taking control of them.

Letting DSA declare this netdev feature as supported (see
dsa_slave_create) would mean that VLAN sub-interfaces created on sja1105
switch ports will be hardware offloaded. That means that
net/8021q/vlan_core.c would install the VLAN into the filter tables of
the switch, potentially interfering with the tag_8021q VLANs.

We need to prevent that from happening and not let the 8021q core
offload VLANs to the switch hardware tables. In vlan_filtering=0 modes
of operation, the switch ports can pass through VLAN-tagged frames with
no problem.

Suggested-by: Florian Fainelli <f.fainelli@...il.com>
Signed-off-by: Vladimir Oltean <olteanv@...il.com>
---
 drivers/net/dsa/sja1105/sja1105_main.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/net/dsa/sja1105/sja1105_main.c b/drivers/net/dsa/sja1105/sja1105_main.c
index df976b259e43..d8cff0107ec4 100644
--- a/drivers/net/dsa/sja1105/sja1105_main.c
+++ b/drivers/net/dsa/sja1105/sja1105_main.c
@@ -1728,6 +1728,21 @@ static void sja1105_teardown(struct dsa_switch *ds)
 	sja1105_static_config_free(&priv->static_config);
 }
 
+static int sja1105_port_enable(struct dsa_switch *ds, int port,
+			       struct phy_device *phy)
+{
+	struct net_device *slave;
+
+	if (!dsa_is_user_port(ds, port))
+		return 0;
+
+	slave = ds->ports[port].slave;
+
+	slave->features &= ~NETIF_F_HW_VLAN_CTAG_FILTER;
+
+	return 0;
+}
+
 static int sja1105_mgmt_xmit(struct dsa_switch *ds, int port, int slot,
 			     struct sk_buff *skb, bool takets)
 {
@@ -2049,6 +2064,7 @@ static const struct dsa_switch_ops sja1105_switch_ops = {
 	.get_ethtool_stats	= sja1105_get_ethtool_stats,
 	.get_sset_count		= sja1105_get_sset_count,
 	.get_ts_info		= sja1105_get_ts_info,
+	.port_enable		= sja1105_port_enable,
 	.port_fdb_dump		= sja1105_fdb_dump,
 	.port_fdb_add		= sja1105_fdb_add,
 	.port_fdb_del		= sja1105_fdb_del,
-- 
2.17.1