[PATCH net-next 1/2] net: sched: report ndo_setup_tc failures via extack

[Jesper Dangaard Brouer <brouer@redhat.com>]

Help end-users of the 'tc' command to see if the drivers ndo_setup_tc
function call fails. Troubleshooting when this happens is non-trivial
(see full process here[1]), and results in net_device getting assigned
the 'qdisc noop', which will drop all TX packets on the interface.

[1]: https://github.com/xdp-project/xdp-project/blob/master/areas/arm64/board_nxp_ls1088/nxp-board04-troubleshoot-qdisc.org

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
 net/sched/cls_api.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index 55bd1429678f..11b683c45c28 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -735,8 +735,11 @@ static int tcf_block_offload_cmd(struct tcf_block *block,
 	INIT_LIST_HEAD(&bo.cb_list);
 
 	err = dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_BLOCK, &bo);
-	if (err < 0)
+	if (err < 0) {
+		if (err != -EOPNOTSUPP)
+			NL_SET_ERR_MSG(extack, "Driver ndo_setup_tc failed");
 		return err;
+	}
 
 	return tcf_block_setup(block, &bo);
 }