net/mlx5e: Reject tc rules which redirect from a VF to itself

Since there are self loopback prevention mechanisms at the
VF level, offloading such rules which redirect from a VF
to itself in the eswitch will break the datapath since the
packets will be dropped once they go back to the vport they
came from.

Therefore, offloading such rules will be rejected and left to
be handled by SW.
Signed-off-by: Ariel Levkovich <lariel@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

drivers/net/ethernet/mellanox/mlx5/core/en_tc.c

@@ -3111,6 +3111,13 @@ static bool same_hw_devs(struct mlx5e_priv *priv, struct mlx5e_priv *peer_priv)
 	return (fsystem_guid == psystem_guid);
 }
 
+static bool same_vf_reps(struct mlx5e_priv *priv,
+			 struct net_device *out_dev)
+{
+	return mlx5e_eswitch_vf_rep(priv->netdev) &&
+	       priv->netdev == out_dev;
+}
+
 static int add_vlan_rewrite_action(struct mlx5e_priv *priv, int namespace,
 				   const struct flow_action_entry *act,
 				   struct mlx5e_tc_flow_parse_attr *parse_attr,
@@ -3796,6 +3803,12 @@ static int parse_tc_fdb_actions(struct mlx5e_priv *priv,
 					return -EOPNOTSUPP;
 				}
 
+				if (same_vf_reps(priv, out_dev)) {
+					NL_SET_ERR_MSG_MOD(extack,
+							   "can't forward from a VF to itself");
+					return -EOPNOTSUPP;
+				}
+
 				out_priv = netdev_priv(out_dev);
 				rpriv = out_priv->ppriv;
 				esw_attr->dests[esw_attr->out_count].rep = rpriv->rep;