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>

1 files changed, 5 insertions, 0 deletions

diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index 09cdcdfe7e91..bcfbdb4758c9 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -181,6 +181,9 @@ replay:
         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)