[PATCH net] net/mlx5: Bridge, fix bogus MDB offload errors

[PATCH net] net/mlx5: Bridge, fix bogus MDB offload errors

[Tariq Toukan]

From: Gal Pressman <gal@nvidia.com>

MDB add operations are queued on the switchdev deferred queue
(SWITCHDEV_F_DEFER), while vlan object deletions are handled
synchronously.
A 'bridge vlan del' can overtake an MDB add that is still queued, and
the vlan is already gone by the time the driver is called.

The two operations are independent in practice: in my test, the MDB add
is triggered by assigning the VF an IPv6 address (hence joining a
solicited-node multicast group), while another process deletes the vlan
from its representor.

Racing 'bridge mdb add' against concurrent 'bridge vlan del' could
result in:

[ 5390.967651] mlx5_core 0000:08:00.0: E-Switch: Failed to lookup bridge port vlan metadata (vport=1)
[ 5390.969120] mlx5_core 0000:08:00.1: E-Switch: Failed to lookup bridge port vlan metadata to create MDB (MAC=33:33:ff:12:00:05,vid=2204,vport=1)
[ 5390.971676] mlx5_core 0000:08:00.1 eth4: Failed to add Port Multicast Database entry (object id=2) with error: -EINVAL (-22).
               Failure in updating the port's Multicast Database could lead to
               multicast forwarding issues.

The error cannot reach anyone that could do anything with it, switchdev
returned success to the bridge as soon as the MDB object was queued, and
the errno only flags the entry as offload failed.
The end result is correct either way, if the MDB has been offloaded
before the vlan was deleted, mlx5_esw_bridge_port_mdb_vlan_flush() would
have removed it.

The FDB path already treats this as a harmless race,
mlx5_esw_bridge_port_vlan_lookup() reports it on 'info' logging level
and skips the offload. mlxsw did the same in [1].

Skip the MDB offload and report on 'info' logging level instead.

[1] Commit 17b334a876fe ("mlxsw: spectrum_switchdev: Don't warn about valid situations")

Fixes: 70f0302b3f20 ("net/mlx5: Bridge, implement mdb offload")
Signed-off-by: Gal Pressman <gal@nvidia.com>
Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
---
 .../ethernet/mellanox/mlx5/core/esw/bridge.c  | 21 ++++++++++---------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/esw/bridge.c b/drivers/net/ethernet/mellanox/mlx5/core/esw/bridge.c
index b4cf3c5ac0dd..7c32dc9db098 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/esw/bridge.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/esw/bridge.c
@@ -1867,26 +1867,27 @@ int mlx5_esw_bridge_port_mdb_add(struct net_device *dev, u16 vport_num, u16 esw_
 
 	port = mlx5_esw_bridge_port_lookup(vport_num, esw_owner_vhca_id, br_offloads);
 	if (!port) {
-		esw_warn(br_offloads->esw->dev,
+		/* MDB is added asynchronously from the switchdev deferred
+		 * queue while port might have been deleted concurrently.
+		 */
+		esw_info(br_offloads->esw->dev,
 			 "Failed to lookup bridge port to add MDB (MAC=%pM,vport=%u)\n",
 			 addr, vport_num);
-		NL_SET_ERR_MSG_FMT_MOD(extack,
-				       "Failed to lookup bridge port to add MDB (MAC=%pM,vport=%u)",
-				       addr, vport_num);
-		return -EINVAL;
+		return 0;
 	}
 
 	bridge = port->bridge;
 	if (bridge->flags & MLX5_ESW_BRIDGE_VLAN_FILTERING_FLAG && vid) {
 		vlan = mlx5_esw_bridge_vlan_lookup(vid, port);
 		if (!vlan) {
-			esw_warn(br_offloads->esw->dev,
+			/* MDB is added asynchronously from the switchdev
+			 * deferred queue while vlan might have been deleted
+			 * concurrently.
+			 */
+			esw_info(br_offloads->esw->dev,
 				 "Failed to lookup bridge port vlan metadata to create MDB (MAC=%pM,vid=%u,vport=%u)\n",
 				 addr, vid, vport_num);
-			NL_SET_ERR_MSG_FMT_MOD(extack,
-					       "Failed to lookup vlan metadata for MDB (MAC=%pM,vid=%u,vport=%u)",
-					       addr, vid, vport_num);
-			return -EINVAL;
+			return 0;
 		}
 	}
 

base-commit: b6ef0d965fe8ce0ee4b4dcb58b3511f83003e42d
-- 
2.44.0

Re: [PATCH net] net/mlx5: Bridge, fix bogus MDB offload errors

[sashiko-bot]

> From: Gal Pressman <gal@nvidia.com>
> 
> MDB add operations are queued on the switchdev deferred queue
> (SWITCHDEV_F_DEFER), while vlan object deletions are handled
> synchronously.
> A 'bridge vlan del' can overtake an MDB add that is still queued, and
> the vlan is already gone by the time the driver is called.
> 
> The two operations are independent in practice: in my test, the MDB add
> is triggered by assigning the VF an IPv6 address (hence joining a
> solicited-node multicast group), while another process deletes the vlan
> from its representor.
> 
> Racing 'bridge mdb add' against concurrent 'bridge vlan del' could
> result in:
> [ ... ]
> 
> Fixes: 70f0302b3f20 ("net/mlx5: Bridge, implement mdb offload")
> Signed-off-by: Gal Pressman <gal@nvidia.com>
> Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>
> Signed-off-by: Tariq Toukan <tariqt@nvidia.com>

Sashiko has reviewed this patch and found no issues.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261021122115.3737284-1-tariqt@nvidia.com?part=1