net_sched: fix class grafting errno codes

If the parent qdisc doesn't support classes, use EOPNOTSUPP.
If the parent class doesn't exist, use ENOENT. Currently EINVAL
is returned in both cases.

Additionally check whether grafting is supported and remove a now
unnecessary graft function from sch_ingress.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/sch_api.c

@@ -728,14 +728,14 @@ static int qdisc_graft(struct net_device *dev, struct Qdisc *parent,
 	} else {
 		const struct Qdisc_class_ops *cops = parent->ops->cl_ops;
 
-		err = -EINVAL;
-
-		if (cops) {
+		err = -EOPNOTSUPP;
+		if (cops && cops->graft) {
 			unsigned long cl = cops->get(parent, classid);
 			if (cl) {
 				err = cops->graft(parent, cl, new, &old);
 				cops->put(parent, cl);
-			}
+			} else
+				err = -ENOENT;
 		}
 		if (!err)
 			notify_and_destroy(skb, n, classid, old, new);

net/sched/sch_ingress.c

@@ -22,12 +22,6 @@ struct ingress_qdisc_data {
 
 /* ------------------------- Class/flow operations ------------------------- */
 
-static int ingress_graft(struct Qdisc *sch, unsigned long arg,
-			 struct Qdisc *new, struct Qdisc **old)
-{
-	return -EOPNOTSUPP;
-}
-
 static struct Qdisc *ingress_leaf(struct Qdisc *sch, unsigned long arg)
 {
 	return NULL;
@@ -123,7 +117,6 @@ nla_put_failure:
 }
 
 static const struct Qdisc_class_ops ingress_class_ops = {
-	.graft		=	ingress_graft,
 	.leaf		=	ingress_leaf,
 	.get		=	ingress_get,
 	.put		=	ingress_put,