netdev - [PATCH net 2/2] net: mscc: ocelot: don't add VID 0 to ocelot->vlans when leaving VLAN-aware bridge

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Message-Id: <20220421230105.3570690-3-vladimir.oltean@nxp.com>
Date:   Fri, 22 Apr 2022 02:01:05 +0300
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     netdev@...r.kernel.org
Cc:     Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Paolo Abeni <pabeni@...hat.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        UNGLinuxDriver@...rochip.com
Subject: [PATCH net 2/2] net: mscc: ocelot: don't add VID 0 to ocelot->vlans when leaving VLAN-aware bridge

DSA, through dsa_port_bridge_leave(), first notifies the port of the
fact that it left a bridge, then, if that bridge was VLAN-aware, it
notifies the port of the change in VLAN awareness state, towards
VLAN-unaware mode.

So ocelot_port_vlan_filtering() can be called when ocelot_port->bridge
is NULL, and this makes ocelot_add_vlan_unaware_pvid() create a struct
ocelot_bridge_vlan with a vid of 0 and an "untagged" setting of true on
that port.

In a way this structure correctly reflects the reality, but by design,
VID 0 (OCELOT_STANDALONE_PVID) was not meant to be kept in the bridge
VLAN list of the driver, but managed separately.

Having OCELOT_STANDALONE_PVID in ocelot->vlans makes us trip up on
several sanity checks that did not expect to have this VID there.
For example, after we leave a VLAN-aware bridge and we re-join it, we
can no longer program egress-tagged VLANs to hardware:

 # ip link add br0 type bridge vlan_filtering 1 && ip link set br0 up
 # ip link set swp0 master br0
 # ip link set swp0 nomaster
 # ip link set swp0 master br0
 # bridge vlan add dev swp0 vid 100
Error: mscc_ocelot_switch_lib: Port with more than one egress-untagged VLAN cannot have egress-tagged VLANs.

But this configuration is in fact supported by the hardware, since we
could use OCELOT_PORT_TAG_NATIVE. According to its comment:

/* all VLANs except the native VLAN and VID 0 are egress-tagged */

yet when assessing the eligibility for this mode, we do not check for
VID 0 in ocelot_port_uses_native_vlan(), instead we just ensure that
ocelot_port_num_untagged_vlans() == 1. This is simply because VID 0
doesn't have a bridge VLAN structure.

The way I identify the problem is that ocelot_port_vlan_filtering(false)
only means to call ocelot_add_vlan_unaware_pvid() when we dynamically
turn off VLAN awareness for a bridge we are under, and the PVID changes
from the bridge PVID to a reserved PVID based on the bridge number.

Since OCELOT_STANDALONE_PVID is statically added to the VLAN table
during ocelot_vlan_init() and never removed afterwards, calling
ocelot_add_vlan_unaware_pvid() for it is not intended and does not serve
any purpose.

Fix the issue by avoiding the call to ocelot_add_vlan_unaware_pvid(vid=0)
when we're resetting VLAN awareness after leaving the bridge, to become
a standalone port.

Fixes: 54c319846086 ("net: mscc: ocelot: enforce FDB isolation when VLAN-unaware")
Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
---
 drivers/net/ethernet/mscc/ocelot.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mscc/ocelot.c b/drivers/net/ethernet/mscc/ocelot.c
index 951c4529f6cd..ca71b62a44dc 100644
--- a/drivers/net/ethernet/mscc/ocelot.c
+++ b/drivers/net/ethernet/mscc/ocelot.c
@@ -551,7 +551,7 @@ int ocelot_port_vlan_filtering(struct ocelot *ocelot, int port,
 	struct ocelot_vcap_block *block = &ocelot->block[VCAP_IS1];
 	struct ocelot_port *ocelot_port = ocelot->ports[port];
 	struct ocelot_vcap_filter *filter;
-	int err;
+	int err = 0;
 	u32 val;

 	list_for_each_entry(filter, &block->rules, list) {
@@ -570,7 +570,7 @@ int ocelot_port_vlan_filtering(struct ocelot *ocelot, int port,
 	if (vlan_aware)
 		err = ocelot_del_vlan_unaware_pvid(ocelot, port,
 						   ocelot_port->bridge);
-	else
+	else if (ocelot_port->bridge)
 		err = ocelot_add_vlan_unaware_pvid(ocelot, port,
 						   ocelot_port->bridge);
 	if (err)
-- 
2.25.1