Commit eda0b7f2 authored by Jamal Hadi Salim's avatar Jamal Hadi Salim Committed by Paolo Abeni
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net/sched: Revert "net/sched: Restrict conditions for adding duplicating netems to qdisc tree" 



This reverts commit ec8e0e3d.

The original patch rejects any tree containing two netems when
either has duplication set, even when they sit on unrelated classes
of the same classful parent. That broke configurations that have
worked since netem was introduced.

The re-entrancy problem the original commit was trying to solve is
handled by later patch using tc_depth flag.

Doing this revert will (re)expose the original bug with multiple
netem duplication. When this patch is backported make sure
and get the full series.

Fixes: ec8e0e3d ("net/sched: Restrict conditions for adding duplicating netems to qdisc tree")
Reported-by: default avatarJi-Soo Chung <jschung2@proton.me>
Reported-by: default avatarGerlinde <lrGerlinde@mailfence.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220774


Reported-by: default avatarzyc zyc <zyc199902@zohomail.cn>
Closes: https://lore.kernel.org/all/19adda5a1e2.12410b78222774.9191120410578703463@zohomail.cn/


Reported-by: default avatarManas Ghandat <ghandatmanas@gmail.com>
Closes: https://lore.kernel.org/netdev/f69b2c8f-8325-4c2e-a011-6dbc089f30e4@gmail.com/


Reviewed-by: default avatarStephen Hemminger <stephen@networkplumber.org>
Signed-off-by: default avatarJamal Hadi Salim <jhs@mojatatu.com>
Link: https://patch.msgid.link/20260525122556.973584-3-jhs@mojatatu.com


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent 98b34f3e

net/sched/sch_netem.c

+0 −40
Original line number Diff line number Diff line
@@ -1007,41 +1007,6 @@ 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)
@@ -1118,11 +1083,6 @@ 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.