Merge branch 'replace-direct-dequeue-call-with-qdisc_dequeue_peeked'

Jamal Hadi Salim says:

====================
Replace direct dequeue call with qdisc_dequeue_peeked

When sfb and red qdiscs have children (eg qfq qdisc) whose peek() callback is
qdisc_peek_dequeued(), we could get a kernel panic. When the parent of such
qdiscs (eg illustrated in patch #3 as tbf) wants to retrieve an skb from
its child (red/sfb in this case), it will do the following:
 1a. do a peek() - and when sensing there's an skb the child can offer, then
     - the child in this case(red/sfb) calls its child's (qfq) peek.
        qfq does the right thing and will return the gso_skb queue packet.
        Note: if there wasnt a gso_skb entry then qfq will store it there.
 1b. invoke a dequeue() on the child (red/sfb). And herein lies the problem.
     - red/sfb will call the child's dequeue() which will essentially just
       try to grab something of qfq's queue.

The right thing to do in #1b is to grab the skb off gso_skb queue.
This patchset fixes that issue by changing #1b to use qdisc_dequeue_peeked()
method instead.

Patch 1 fixes the issue for red qdisc. Patch 2 fixes it for sfb.
Patch 3 adds testcases for the two setups.
====================

Link: https://patch.msgid.link/20260430152957.194015-1-jhs@mojatatu.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 148 insertions, 0 deletions

diff --git a/tools/testing/selftests/tc-testing/tc-tests/infra/qdiscs.json b/tools/testing/selftests/tc-testing/tc-tests/infra/qdiscs.json
index eefadd0546d3..b1f856cf62c1 100644
--- a/tools/testing/selftests/tc-testing/tc-tests/infra/qdiscs.json
+++ b/tools/testing/selftests/tc-testing/tc-tests/infra/qdiscs.json
@@ -1136,5 +1136,153 @@
         "teardown": [
             "$TC qdisc del dev $DUMMY handle 1: root"
         ]
+    },
+    {
+        "id": "7a5f",
+        "name": "Force red to dequeue from its child's gso_skb with qfq leaf",
+        "category": [
+            "qdisc",
+            "tbf",
+            "red",
+            "qfq"
+        ],
+        "plugins": {
+            "requires": "nsPlugin"
+        },
+        "setup": [
+            "$IP link set dev $DUMMY up || true",
+            "$IP addr add 10.10.11.10/24 dev $DUMMY || true",
+            "$TC qdisc add dev $DUMMY root handle 1: tbf rate 88bit burst 1661b peakrate 2257333 minburst 1024 limit 7b",
+            "$TC qdisc add dev $DUMMY parent 1: handle 2: red limit 757 min 16 max 24 avpkt 16",
+            "$TC qdisc add dev $DUMMY parent 2: handle 3: qfq",
+            "$TC class add dev $DUMMY classid 3:1 parent 3: qfq maxpkt 512 weight 1",
+            "$TC filter add dev $DUMMY parent 3: protocol ip prio 1 matchall classid 3:1 action ok"
+        ],
+        "cmdUnderTest": "ping -c 1 10.10.10.1 -W0.01 -I$DUMMY || true",
+        "expExitCode": "0",
+        "verifyCmd": "$TC -s -j qdisc ls dev $DUMMY parent 1:",
+        "matchJSON": [
+            {
+                "kind": "red",
+                "handle": "2:",
+                "bytes": 98,
+                "packets": 1,
+                "backlog": 0,
+                "qlen": 0
+            }
+        ],
+        "teardown": [
+            "$TC qdisc del dev $DUMMY handle 1: root"
+        ]
+    },
+    {
+        "id": "cdae",
+        "name": "Force sfb to dequeue from its child's gso_skb with qfq leaf",
+        "category": [
+            "qdisc",
+            "tbf",
+            "sfb",
+            "qfq"
+        ],
+        "plugins": {
+            "requires": "nsPlugin"
+        },
+        "setup": [
+            "$IP link set dev $DUMMY up || true",
+            "$IP addr add 10.10.11.10/24 dev $DUMMY || true",
+            "$TC qdisc add dev $DUMMY root handle 1: tbf rate 88bit burst 1661b peakrate 2257333 minburst 1024 limit 7b",
+            "$TC qdisc add dev $DUMMY parent 1: handle 2: sfb",
+            "$TC qdisc add dev $DUMMY parent 2: handle 3: qfq",
+            "$TC class add dev $DUMMY classid 3:1 parent 3: qfq maxpkt 512 weight 1",
+            "$TC filter add dev $DUMMY parent 3: protocol ip prio 1 matchall classid 3:1 action ok"
+        ],
+        "cmdUnderTest": "ping -c 1 10.10.10.1 -W0.01 -I$DUMMY || true",
+        "expExitCode": "0",
+        "verifyCmd": "$TC -s -j qdisc ls dev $DUMMY parent 1:",
+        "matchJSON": [
+            {
+                "kind": "sfb",
+                "handle": "2:",
+                "bytes": 98,
+                "packets": 1,
+                "backlog": 0,
+                "qlen": 0
+            }
+        ],
+        "teardown": [
+            "$TC qdisc del dev $DUMMY handle 1: root"
+        ]
+    },
+    {
+        "id": "291d",
+        "name": "Force red to dequeue from its child's gso_skb with dualpi2 leaf",
+        "category": [
+            "qdisc",
+            "tbf",
+            "red",
+            "dualpi2"
+        ],
+        "plugins": {
+            "requires": "nsPlugin"
+        },
+        "setup": [
+            "$IP link set dev $DUMMY up || true",
+            "$IP addr add 10.10.11.10/24 dev $DUMMY || true",
+            "$TC qdisc add dev $DUMMY root handle 1: tbf rate 88bit burst 1661b peakrate 2257333 minburst 1024 limit 7b",
+            "$TC qdisc add dev $DUMMY parent 1: handle 2: red limit 757 min 16 max 24 avpkt 16",
+            "$TC qdisc add dev $DUMMY parent 2: handle 3: dualpi2"
+        ],
+        "cmdUnderTest": "ping -c 1 10.10.10.1 -W0.01 -I$DUMMY || true",
+        "expExitCode": "0",
+        "verifyCmd": "$TC -s -j qdisc ls dev $DUMMY parent 1:",
+        "matchJSON": [
+            {
+                "kind": "red",
+                "handle": "2:",
+                "bytes": 98,
+                "packets": 1,
+                "backlog": 0,
+                "qlen": 0
+            }
+        ],
+        "teardown": [
+            "$TC qdisc del dev $DUMMY handle 1: root"
+        ]
+    },
+    {
+        "id": "9c6d",
+        "name": "Force sfb to dequeue from its child's gso_skb with dualpi2 leaf",
+        "category": [
+            "qdisc",
+            "tbf",
+            "sfb",
+            "dualpi2"
+        ],
+        "plugins": {
+            "requires": "nsPlugin"
+        },
+        "setup": [
+            "$IP link set dev $DUMMY up || true",
+            "$IP addr add 10.10.11.10/24 dev $DUMMY || true",
+            "$TC qdisc add dev $DUMMY root handle 1: tbf rate 88bit burst 1661b peakrate 2257333 minburst 1024 limit 7b",
+            "$TC qdisc add dev $DUMMY parent 1: handle 2: sfb",
+            "$TC qdisc add dev $DUMMY parent 2: handle 3: dualpi2"
+        ],
+        "cmdUnderTest": "ping -c 1 10.10.10.1 -W0.01 -I$DUMMY || true",
+        "expExitCode": "0",
+        "verifyCmd": "$TC -s -j qdisc ls dev $DUMMY parent 1:",
+        "matchJSON": [
+            {
+                "kind": "sfb",
+                "handle": "2:",
+                "bytes": 98,
+                "packets": 1,
+                "backlog": 0,
+                "qlen": 0
+            }
+        ],
+        "teardown": [
+            "$TC qdisc del dev $DUMMY handle 1: root"
+        ]
     }
 ]