net: sched: Fix for duplicate class dump

Phil Sutter · davem330 · commit 3c53ed8fef68 · 2018-10-18T16:00:02.000-07:00
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: cb395b2 ("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
@@ -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;
 	}

Original file line number	Diff line number	Diff line change
`@@ -2059,7 +2059,8 @@ static int tc_dump_tclass_root(struct Qdisc root, struct sk_buff skb,`
`2059`	`2059`
`2060`	`2060`	`if (tcm->tcm_parent) {`
`2061`	`2061`	`q = qdisc_match_from_root(root, TC_H_MAJ(tcm->tcm_parent));`
`2062`		`- if (q && tc_dump_tclass_qdisc(q, skb, tcm, cb, t_p, s_t) < 0)`
	`2062`	`+ if (q && q != root &&`
	`2063`	`+ tc_dump_tclass_qdisc(q, skb, tcm, cb, t_p, s_t) < 0)`
`2063`	`2064`	`return -1;`
`2064`	`2065`	`return 0;`
`2065`	`2066`	`}`