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: 59cc1f61f ("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>

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index ff515d01951e0c2def7459c4e40e3407478e261f..d677b3484d81ec57006109e119f637890a42f436 100644 (file)
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -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: