net_sched: make cls_ops->tcf_chain() optional

Some qdiscs don't support attaching filters. Handle this centrally in
cls_api and return a proper errno code (EOPNOTSUPP) instead of EINVAL.
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/cls_api.c

@@ -181,6 +181,9 @@ static int tc_ctl_tfilter(struct sk_buff *skb, struct nlmsghdr *n, void *arg)
 	if ((cops = q->ops->cl_ops) == NULL)
 		return -EINVAL;
 
+	if (cops->tcf_chain == NULL)
+		return -EOPNOTSUPP;
+
 	/* Do we search for filter, attached to class? */
 	if (TC_H_MIN(parent)) {
 		cl = cops->get(q, parent);
@@ -433,6 +436,8 @@ static int tc_dump_tfilter(struct sk_buff *skb, struct netlink_callback *cb)
 		goto out;
 	if ((cops = q->ops->cl_ops) == NULL)
 		goto errout;
+	if (cops->tcf_chain == NULL)
+		goto errout;
 	if (TC_H_MIN(tcm->tcm_parent)) {
 		cl = cops->get(q, tcm->tcm_parent);
 		if (cl == 0)

net/sched/sch_red.c

@@ -331,11 +331,6 @@ static void red_walk(struct Qdisc *sch, struct qdisc_walker *walker)
 	}
 }
 
-static struct tcf_proto **red_find_tcf(struct Qdisc *sch, unsigned long cl)
-{
-	return NULL;
-}
-
 static const struct Qdisc_class_ops red_class_ops = {
 	.graft		=	red_graft,
 	.leaf		=	red_leaf,
@@ -344,7 +339,6 @@ static const struct Qdisc_class_ops red_class_ops = {
 	.change		=	red_change_class,
 	.delete		=	red_delete,
 	.walk		=	red_walk,
-	.tcf_chain	=	red_find_tcf,
 	.dump		=	red_dump_class,
 };
 

net/sched/sch_tbf.c

@@ -433,11 +433,6 @@ static void tbf_walk(struct Qdisc *sch, struct qdisc_walker *walker)
 	}
 }
 
-static struct tcf_proto **tbf_find_tcf(struct Qdisc *sch, unsigned long cl)
-{
-	return NULL;
-}
-
 static const struct Qdisc_class_ops tbf_class_ops =
 {
 	.graft		=	tbf_graft,
@@ -447,7 +442,6 @@ static const struct Qdisc_class_ops tbf_class_ops =
 	.change		=	tbf_change_class,
 	.delete		=	tbf_delete,
 	.walk		=	tbf_walk,
-	.tcf_chain	=	tbf_find_tcf,
 	.dump		=	tbf_dump_class,
 };