netdev - [PATCH net] net: mscc: ocelot: fix tagged VLAN refusal while under a VLAN-unaware bridge

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Date:   Tue, 27 Sep 2022 15:20:42 +0300
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     netdev@...r.kernel.org
Cc:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        UNGLinuxDriver@...rochip.com,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Colin Foster <colin.foster@...advantage.com>,
        Maxim Kochetkov <fido_max@...ox.ru>
Subject: [PATCH net] net: mscc: ocelot: fix tagged VLAN refusal while under a VLAN-unaware bridge

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@....com>
---
 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 7a613b52787d..13b14110a060 100644
--- a/drivers/net/ethernet/mscc/ocelot.c
+++ b/drivers/net/ethernet/mscc/ocelot.c
@@ -289,6 +289,13 @@ static int ocelot_port_num_untagged_vlans(struct ocelot *ocelot, int port)
 		if (!(vlan->portmask & BIT(port)))
 			continue;

+		/* 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))
 			num_untagged++;
 	}
-- 
2.34.1