[PATCH 5.19 094/101] net: mscc: ocelot: fix tagged VLAN refusal while under a VLAN-unaware bridge

From: Greg Kroah-Hartman
Date: Mon Oct 03 2022 - 03:25:38 EST

From: Vladimir Oltean <vladimir.oltean@xxxxxxx>

[ Upstream commit 276d37eb449133bc22872b8f0a6f878e120deeff ]

Currently the following set of commands fails:

$ ip link add br0 type bridge # vlan_filtering 0
$ ip link set swp0 master br0
$ bridge vlan
port vlan-id
swp0 1 PVID Egress Untagged
$ bridge vlan add dev swp0 vid 10
Error: mscc_ocelot_switch_lib: Port with more than one egress-untagged VLAN cannot have egress-tagged VLANs.

Dumping ocelot->vlans, one can see that the 2 egress-untagged VLANs on swp0 are
vid 1 (the bridge PVID) and vid 4094, a PVID used privately by the driver for
VLAN-unaware bridging. So this is why bridge vid 10 is refused, despite
'bridge vlan' showing a single egress untagged VLAN.

As mentioned in the comment added, having this private VLAN does not impose
restrictions to the hardware configuration, yet it is a bookkeeping problem.

There are 2 possible solutions.

One is to make the functions that operate on VLAN-unaware pvids:
- ocelot_add_vlan_unaware_pvid()
- ocelot_del_vlan_unaware_pvid()
- ocelot_port_setup_dsa_8021q_cpu()
- ocelot_port_teardown_dsa_8021q_cpu()
call something different than ocelot_vlan_member_(add|del)(), the latter being
the real problem, because it allocates a struct ocelot_bridge_vlan *vlan which
it adds to ocelot->vlans. We don't really *need* the private VLANs in
ocelot->vlans, it's just that we have the extra convenience of having the
vlan->portmask cached in software (whereas without these structures, we'd have
to create a raw ocelot_vlant_rmw_mask() procedure which reads back the current
port mask from hardware).

The other solution is to filter out the private VLANs from
ocelot_port_num_untagged_vlans(), since they aren't what callers care about.
We only need to do this to the mentioned function and not to
ocelot_port_num_tagged_vlans(), because private VLANs are never egress-tagged.

Nothing else seems to be broken in either solution, but the first one requires
more rework which will conflict with the net-next change 36a0bf443585 ("net:
mscc: ocelot: set up tag_8021q CPU ports independent of user port affinity"),
and I'd like to avoid that. So go with the other one.

Fixes: 54c319846086 ("net: mscc: ocelot: enforce FDB isolation when VLAN-unaware")
Signed-off-by: Vladimir Oltean <vladimir.oltean@xxxxxxx>
Link: https://lore.kernel.org/r/20220927122042.1100231-1-vladimir.oltean@xxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
drivers/net/ethernet/mscc/ocelot.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/drivers/net/ethernet/mscc/ocelot.c b/drivers/net/ethernet/mscc/ocelot.c
index 68991b021c56..c250ad6dc956 100644
--- a/drivers/net/ethernet/mscc/ocelot.c
+++ b/drivers/net/ethernet/mscc/ocelot.c
@@ -290,6 +290,13 @@ static int ocelot_port_num_untagged_vlans(struct ocelot *ocelot, int port)
if (!(vlan->portmask & BIT(port)))

+ /* Ignore the VLAN added by ocelot_add_vlan_unaware_pvid(),
+ * because this is never active in hardware at the same time as
+ * the bridge VLANs, which only matter in VLAN-aware mode.
+ */
+ if (vlan->vid >= OCELOT_RSV_VLAN_RANGE_START)
+ continue;
if (vlan->untagged & BIT(port))