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Subject[PATCH 5.10 100/167] net: dsa: sja1105: make VID 4095 a bridge VLAN too
From: Vladimir Oltean <>

[ Upstream commit e40cba9490bab1414d45c2d62defc0ad4f6e4136 ]

This simple series of commands:

ip link add br0 type bridge vlan_filtering 1
ip link set swp0 master br0

fails on sja1105 with the following error:
[ 33.439103] sja1105 spi0.1: vlan-lookup-table needs to have at least the default untagged VLAN
[ 33.447710] sja1105 spi0.1: Invalid config, cannot upload
Warning: sja1105: Failed to change VLAN Ethertype.

For context, sja1105 has 3 operating modes:
- SJA1105_VLAN_UNAWARE: the dsa_8021q_vlans are committed to hardware
- SJA1105_VLAN_FILTERING_FULL: the bridge_vlans are committed to hardware
- SJA1105_VLAN_FILTERING_BEST_EFFORT: both the dsa_8021q_vlans and the
bridge_vlans are committed to hardware

Swapping out a VLAN list and another in happens in
sja1105_build_vlan_table(), which performs a delta update procedure.
That function is called from a few places, notably from
sja1105_vlan_filtering() which is called from the

The above set of 2 commands fails when run on a kernel pre-commit
8841f6e63f2c ("net: dsa: sja1105: make devlink property
best_effort_vlan_filtering true by default"). So the priv->vlan_state
transition that takes place is between VLAN-unaware and full VLAN
filtering. So the dsa_8021q_vlans are swapped out and the bridge_vlans
are swapped in.

So why does it fail?

Well, the bridge driver, through nbp_vlan_init(), first sets up the
proceeds to call nbp_vlan_add for the default_pvid.

So when we swap out the dsa_8021q_vlans and swap in the bridge_vlans in
the SWITCHDEV_ATTR_ID_BRIDGE_VLAN_FILTERING handler, there are no bridge
VLANs (yet). So we have wiped the VLAN table clean, and the low-level
static config checker complains of an invalid configuration. We _will_
add the bridge VLANs using the dynamic config interface, albeit later,
when nbp_vlan_add() calls us. So it is natural that it fails.

So why did it ever work?

Surprisingly, it looks like I only tested this configuration with 2
things set up in a particular way:
- a network manager that brings all ports up
- a kernel with CONFIG_VLAN_8021Q=y

It is widely known that commit ad1afb003939 ("vlan_dev: VLAN 0 should be
treated as "no vlan tag" (802.1p packet)") installs VID 0 to every net
device that comes up. DSA treats these VLANs as bridge VLANs, and
therefore, in my testing, the list of bridge_vlans was never empty.

However, if CONFIG_VLAN_8021Q is not enabled, or the port is not up when
it joins a VLAN-aware bridge, the bridge_vlans list will be temporarily
empty, and the sja1105_static_config_reload() call from
sja1105_vlan_filtering() will fail.

To fix this, the simplest thing is to keep VID 4095, the one used for
CPU-injected control packets since commit ed040abca4c1 ("net: dsa:
sja1105: use 4095 as the private VLAN for untagged traffic"), in the
list of bridge VLANs too, not just the list of tag_8021q VLANs. This
ensures that the list of bridge VLANs will never be empty.

Fixes: ec5ae61076d0 ("net: dsa: sja1105: save/restore VLANs using a delta commit method")
Reported-by: Radu Pirea (NXP OSS) <>
Signed-off-by: Vladimir Oltean <>
Signed-off-by: David S. Miller <>
Signed-off-by: Sasha Levin <>
drivers/net/dsa/sja1105/sja1105_main.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/drivers/net/dsa/sja1105/sja1105_main.c b/drivers/net/dsa/sja1105/sja1105_main.c
index 82852c57cc0e..82b918d36117 100644
--- a/drivers/net/dsa/sja1105/sja1105_main.c
+++ b/drivers/net/dsa/sja1105/sja1105_main.c
@@ -350,6 +350,12 @@ static int sja1105_init_static_vlan(struct sja1105_private *priv)
if (dsa_is_cpu_port(ds, port))
v->pvid = true;
list_add(&v->list, &priv->dsa_8021q_vlans);
+ v = kmemdup(v, sizeof(*v), GFP_KERNEL);
+ if (!v)
+ return -ENOMEM;
+ list_add(&v->list, &priv->bridge_vlans);

((struct sja1105_vlan_lookup_entry *)table->entries)[0] = pvid;

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