[Patch net v6 2/8] Revert "net/sched: Restrict conditions for adding duplicating netems to qdisc tree"

Cong Wang
2025-12-27T19:41:48Z

From: Cong Wang <cwang@multikernel.io>

This reverts commit ec8e0e3d7adef940cdf9475e2352c0680189d14e since it
breaks mq+netem.

Reported-by: Ji-Soo Chung <jschung2@proton.me>
Reported-by: Gerlinde <lrGerlinde@mailfence.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220774
Signed-off-by: Cong Wang <cwang@multikernel.io>
---
net/sched/sch_netem.c | 40 ----------------------------------------
1 file changed, 40 deletions(-)

diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index 32a5f3304046..a9ea40c13527 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -974,41 +974,6 @@ static int parse_attr(struct nlattr *tb[], int maxtype, struct nlattr *nla,
return 0;
}

-static const struct Qdisc_class_ops netem_class_ops;
-
-static int check_netem_in_tree(struct Qdisc *sch, bool duplicates,
- struct netlink_ext_ack *extack)
-{
- struct Qdisc *root, *q;
- unsigned int i;
-
- root = qdisc_root_sleeping(sch);
-
- if (sch != root && root->ops->cl_ops == &netem_class_ops) {
- if (duplicates ||
- ((struct netem_sched_data *)qdisc_priv(root))->duplicate)
- goto err;
- }
-
- if (!qdisc_dev(root))
- return 0;
-
- hash_for_each(qdisc_dev(root)->qdisc_hash, i, q, hash) {
- if (sch != q && q->ops->cl_ops == &netem_class_ops) {
- if (duplicates ||
- ((struct netem_sched_data *)qdisc_priv(q))->duplicate)
- goto err;
- }
- }
-
- return 0;
-
-err:
- NL_SET_ERR_MSG(extack,
- "netem: cannot mix duplicating netems with other netems in tree");
- return -EINVAL;
-}
-
/* Parse netlink message to set options */
static int netem_change(struct Qdisc *sch, struct nlattr *opt,
struct netlink_ext_ack *extack)
@@ -1067,11 +1032,6 @@ static int netem_change(struct Qdisc *sch, struct nlattr *opt,
q->gap = qopt->gap;
q->counter = 0;
q->loss = qopt->loss;
-
- ret = check_netem_in_tree(sch, qopt->duplicate, extack);
- if (ret)
- goto unlock;
-
q->duplicate = qopt->duplicate;

/* for compatibility with earlier versions.
--
2.34.1