mlxsw: spectrum_router: Prepare for nexthops with trap action

Nexthops that need to be programmed with a trap action might not have a
valid router interface (RIF) associated with them. Therefore, use the
loopback RIF created during initialization to program them to the
device.
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -3411,10 +3411,13 @@ static int __mlxsw_sp_nexthop_update(struct mlxsw_sp *mlxsw_sp, u32 adj_index,
 {
 	struct mlxsw_sp_neigh_entry *neigh_entry = nh->neigh_entry;
 	char ratr_pl[MLXSW_REG_RATR_LEN];
+	u16 rif_index;
 
+	rif_index = nh->rif ? nh->rif->rif_index :
+			      mlxsw_sp->router->lb_rif_index;
 	mlxsw_reg_ratr_pack(ratr_pl, MLXSW_REG_RATR_OP_WRITE_WRITE_ENTRY,
 			    true, MLXSW_REG_RATR_TYPE_ETHERNET,
-			    adj_index, nh->rif->rif_index);
+			    adj_index, rif_index);
 	if (nh->action == MLXSW_SP_NEXTHOP_ACTION_DISCARD)
 		mlxsw_reg_ratr_trap_action_set(ratr_pl,
 					       MLXSW_REG_RATR_TRAP_ACTION_DISCARD_ERRORS);