Commit ea327469 authored Aug 16, 2016 by Jiri Kosina Committed by David S. Miller Aug 18, 2016

net: sched: avoid duplicates in qdisc dump

tc_dump_qdisc() performs dumping of the per-device qdiscs in two phases;
first, the "standard" dev->qdisc is being dumped. Second, if there is/are
ingress queue(s), they are being dumped as well.

After conversion of netdevice's qdisc linked-list into hashtable, these
two sets are not in two disjunctive sets/lists any more, but are both
"reachable" directly from netdevice's hashtable. As a consequence, the
"full-depth" dump of the ingress qdiscs results in immediately hitting the
netdevice hashtable again, and duplicating the dump that has already been
performed for dev->qdisc.
What in fact needs to be dumped in case of ingress queue is "just" the
top-level ingress qdisc, as everything else has been dumped already.

Fix this by extending tc_dump_qdisc_root() in a way that it can be instructed
whether it should (while performing the "full" per-netdev qdisc dump) perform
the whole recursion, or just dump "additional" top-level (ingress) qdiscs
without performing any kind of recursion.

This fixes duplicate dumps such as

qdisc mq 0: root
qdisc pfifo_fast 0: parent :4 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
qdisc pfifo_fast 0: parent :3 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
qdisc pfifo_fast 0: parent :2 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
qdisc pfifo_fast 0: parent :1 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
qdisc clsact ffff: parent ffff:fff1
qdisc pfifo_fast 0: parent :4 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
qdisc pfifo_fast 0: parent :3 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
qdisc pfifo_fast 0: parent :2 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
qdisc pfifo_fast 0: parent :1 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1

Fixes: 59cc1f61 ("net: sched: convert qdisc linked list to hashtable")
Reported-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 69012ae4

net/sched/sch_api.c

+10 −4

Original line number	Diff line number	Diff line
		@@ -1435,7 +1435,7 @@ err_out:

		static int tc_dump_qdisc_root(struct Qdisc root, struct sk_buff skb,
		struct netlink_callback *cb,
		int *q_idx_p, int s_q_idx)
		int *q_idx_p, int s_q_idx, bool recur)
		{
		int ret = 0, q_idx = *q_idx_p;
		struct Qdisc *q;
		@@ -1455,7 +1455,13 @@ static int tc_dump_qdisc_root(struct Qdisc root, struct sk_buff skb,
		q_idx++;
		}

		if (!qdisc_dev(root))
		/* If dumping singletons, there is no qdisc_dev(root) and the singleton
		* itself has already been dumped.
		*
		* If we've already dumped the top-level (ingress) qdisc above and the global
		* qdisc hashtable, we don't want to hit it again
		*/
		if (!qdisc_dev(root) \|\| !recur)
		goto out;

		hash_for_each(qdisc_dev(root)->qdisc_hash, b, q, hash) {
		@@ -1499,13 +1505,13 @@ static int tc_dump_qdisc(struct sk_buff skb, struct netlink_callback cb)
		s_q_idx = 0;
		q_idx = 0;

		if (tc_dump_qdisc_root(dev->qdisc, skb, cb, &q_idx, s_q_idx) < 0)
		if (tc_dump_qdisc_root(dev->qdisc, skb, cb, &q_idx, s_q_idx, true) < 0)
		goto done;

		dev_queue = dev_ingress_queue(dev);
		if (dev_queue &&
		tc_dump_qdisc_root(dev_queue->qdisc_sleeping, skb, cb,
		&q_idx, s_q_idx) < 0)
		&q_idx, s_q_idx, false) < 0)
		goto done;

		cont:

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