net: sched: Fix for duplicate class dump

When dumping classes by parent, kernel would return classes twice:

| # tc qdisc add dev lo root prio
| # tc class show dev lo
| class prio 8001:1 parent 8001:
| class prio 8001:2 parent 8001:
| class prio 8001:3 parent 8001:
| # tc class show dev lo parent 8001:
| class prio 8001:1 parent 8001:
| class prio 8001:2 parent 8001:
| class prio 8001:3 parent 8001:
| class prio 8001:1 parent 8001:
| class prio 8001:2 parent 8001:
| class prio 8001:3 parent 8001:

This comes from qdisc_match_from_root() potentially returning the root
qdisc itself if its handle matched. Though in that case, root's classes
were already dumped a few lines above.

Fixes: cb395b2010879 ("net: sched: optimize class dumps")
Signed-off-by: Phil Sutter <phil@nwl.cc>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 6684641ea344826c57fdc586e7dfbf157476d186..3dc0acf542454e231de923a7c3287376841b6442 100644 (file)
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -2059,7 +2059,8 @@ static int tc_dump_tclass_root(struct Qdisc *root, struct sk_buff *skb,
 
        if (tcm->tcm_parent) {
                q = qdisc_match_from_root(root, TC_H_MAJ(tcm->tcm_parent));
-               if (q && tc_dump_tclass_qdisc(q, skb, tcm, cb, t_p, s_t) < 0)
+               if (q && q != root &&
+                   tc_dump_tclass_qdisc(q, skb, tcm, cb, t_p, s_t) < 0)
                        return -1;
                return 0;
        }