mlxsw: spectrum_router: Ignore routes using a deleted nexthop object

Routes are currently processed from a workqueue whereas nexthop objects
are processed in system call context. This can result in the driver not
finding a suitable nexthop group for a route and issuing a warning [1].

Fix this by ignoring such routes earlier in the process. The subsequent
deletion notification will be ignored as well.

[1]
 WARNING: CPU: 2 PID: 7754 at drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c:4853 mlxsw_sp_router_fib_event_work+0x1112/0x1e00 [mlxsw_spectrum]
 [...]
 CPU: 2 PID: 7754 Comm: kworker/u8:0 Not tainted 5.11.0-rc6-cq-20210207-1 #16
 Hardware name: Mellanox Technologies Ltd. MSN2100/SA001390, BIOS 5.6.5 05/24/2018
 Workqueue: mlxsw_core_ordered mlxsw_sp_router_fib_event_work [mlxsw_spectrum]
 RIP: 0010:mlxsw_sp_router_fib_event_work+0x1112/0x1e00 [mlxsw_spectrum]

Fixes: cdd6cfc5 ("mlxsw: spectrum_router: Allow programming routes with nexthop objects")
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reported-by: Alex Veber <alexve@nvidia.com>
Tested-by: Alex Veber <alexve@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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

@@ -5951,6 +5951,10 @@ mlxsw_sp_router_fib4_replace(struct mlxsw_sp *mlxsw_sp,
 	if (mlxsw_sp->router->aborted)
 		return 0;
 
+	if (fen_info->fi->nh &&
+	    !mlxsw_sp_nexthop_obj_group_lookup(mlxsw_sp, fen_info->fi->nh->id))
+		return 0;
+
 	fib_node = mlxsw_sp_fib_node_get(mlxsw_sp, fen_info->tb_id,
 					 &fen_info->dst, sizeof(fen_info->dst),
 					 fen_info->dst_len,
@@ -6601,6 +6605,9 @@ static int mlxsw_sp_router_fib6_replace(struct mlxsw_sp *mlxsw_sp,
 	if (mlxsw_sp_fib6_rt_should_ignore(rt))
 		return 0;
 
+	if (rt->nh && !mlxsw_sp_nexthop_obj_group_lookup(mlxsw_sp, rt->nh->id))
+		return 0;
+
 	fib_node = mlxsw_sp_fib_node_get(mlxsw_sp, rt->fib6_table->tb6_id,
 					 &rt->fib6_dst.addr,
 					 sizeof(rt->fib6_dst.addr),