mlxsw: spectrum_span: Do not overwrite policer configuration

The purpose of the delayed work in the SPAN module is to potentially
update the destination port and various encapsulation parameters of SPAN
agents that point to a VLAN device or a GRE tap. The destination port
can change following the insertion of a new route, for example.

SPAN agents that point to a physical port or the CPU port are static and
never change throughout the lifetime of the SPAN agent. Therefore, skip
over them in the delayed work.

This fixes an issue where the delayed work overwrites the policer
that was set on a SPAN agent pointing to the CPU. Modifying the delayed
work to inherit the original policer configuration is error-prone, as
the same will be needed for any new parameter.

Fixes: 4039504 ("mlxsw: spectrum_span: Allow setting policer on a SPAN agent")
Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/mellanox/mlxsw/spectrum_span.c

@@ -157,6 +157,7 @@ mlxsw_sp1_span_entry_cpu_deconfigure(struct mlxsw_sp_span_entry *span_entry)
 
 static const
 struct mlxsw_sp_span_entry_ops mlxsw_sp1_span_entry_ops_cpu = {
+	.is_static = true,
 	.can_handle = mlxsw_sp1_span_cpu_can_handle,
 	.parms_set = mlxsw_sp1_span_entry_cpu_parms,
 	.configure = mlxsw_sp1_span_entry_cpu_configure,
@@ -214,6 +215,7 @@ mlxsw_sp_span_entry_phys_deconfigure(struct mlxsw_sp_span_entry *span_entry)
 
 static const
 struct mlxsw_sp_span_entry_ops mlxsw_sp_span_entry_ops_phys = {
+	.is_static = true,
 	.can_handle = mlxsw_sp_port_dev_check,
 	.parms_set = mlxsw_sp_span_entry_phys_parms,
 	.configure = mlxsw_sp_span_entry_phys_configure,
@@ -721,6 +723,7 @@ mlxsw_sp2_span_entry_cpu_deconfigure(struct mlxsw_sp_span_entry *span_entry)
 
 static const
 struct mlxsw_sp_span_entry_ops mlxsw_sp2_span_entry_ops_cpu = {
+	.is_static = true,
 	.can_handle = mlxsw_sp2_span_cpu_can_handle,
 	.parms_set = mlxsw_sp2_span_entry_cpu_parms,
 	.configure = mlxsw_sp2_span_entry_cpu_configure,
@@ -1036,6 +1039,9 @@ static void mlxsw_sp_span_respin_work(struct work_struct *work)
 		if (!refcount_read(&curr->ref_count))
 			continue;
 
+		if (curr->ops->is_static)
+			continue;
+
 		err = curr->ops->parms_set(mlxsw_sp, curr->to_dev, &sparms);
 		if (err)
 			continue;

drivers/net/ethernet/mellanox/mlxsw/spectrum_span.h

@@ -60,6 +60,7 @@ struct mlxsw_sp_span_entry {
 };
 
 struct mlxsw_sp_span_entry_ops {
+	bool is_static;
 	bool (*can_handle)(const struct net_device *to_dev);
 	int (*parms_set)(struct mlxsw_sp *mlxsw_sp,
 			 const struct net_device *to_dev,