netdev - [PATCH net 2/2] selftests/tc-testing: Add tests for restrictions on netem duplication

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Message-ID: <20250622190344.446090-2-will@willsroot.io>
Date: Sun, 22 Jun 2025 19:05:31 +0000
From: William Liu <will@...lsroot.io>
To: netdev@...r.kernel.org
Cc: jhs@...atatu.com, xiyou.wangcong@...il.com, victor@...atatu.com, pctammela@...atatu.com, pabeni@...hat.com, kuba@...nel.org, stephen@...workplumber.org, dcaratti@...hat.com, savy@...t3mfailure.io, jiri@...nulli.us, davem@...emloft.net, edumazet@...gle.com, horms@...nel.org, William Liu <will@...lsroot.io>
Subject: [PATCH net 2/2] selftests/tc-testing: Add tests for restrictions on netem duplication

Ensure that a duplicating netem cannot exist in a tree with other netems
in both qdisc addition and change. This is meant to prevent the soft
lockup and OOM loop scenario discussed in [1].

[1] https://lore.kernel.org/netdev/8DuRWwfqjoRDLDmBMlIfbrsZg9Gx50DHJc1ilxsEBNe2D6NMoigR_eIRIG0LOjMc3r10nUUZtArXx4oZBIdUfZQrwjcQhdinnMis_0G7VEk=@willsroot.io/

Signed-off-by: William Liu <will@...lsroot.io>
Reviewed-by: Savino Dicanosa <savy@...t3mfailure.io>
---
 .../tc-testing/tc-tests/qdiscs/netem.json     | 41 +++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/tools/testing/selftests/tc-testing/tc-tests/qdiscs/netem.json b/tools/testing/selftests/tc-testing/tc-tests/qdiscs/netem.json
index 3c4444961488..e46a97e75f4b 100644
--- a/tools/testing/selftests/tc-testing/tc-tests/qdiscs/netem.json
+++ b/tools/testing/selftests/tc-testing/tc-tests/qdiscs/netem.json
@@ -336,5 +336,46 @@
         "teardown": [
             "$TC qdisc del dev $DUMMY handle 1: root"
         ]
+    },
+    {
+        "id": "d34d",
+        "name": "NETEM test qdisc duplication restriction in qdisc tree",
+        "category": ["qdisc", "netem"],
+        "plugins": {
+            "requires": "nsPlugin"
+        },
+        "setup": [
+            "$IP link set lo up || true",
+            "$TC qdisc add dev lo root handle 1: netem limit 1 duplicate 100%"
+        ],
+        "cmdUnderTest": "$TC qdisc add dev lo parent 1: handle 2: netem gap 1 limit 1 duplicate 100% delay 1us reorder 100%",
+        "expExitCode": "2",
+        "verifyCmd": "$TC -s qdisc show dev lo",
+        "matchPattern": "qdisc netem",
+        "matchCount": "1",
+        "teardown": [
+            "$TC qdisc del dev lo handle 1:0 root"
+        ]
+    },
+    {
+        "id": "b33f",
+        "name": "NETEM test qdisc duplication restriction in qdisc tree in netem_change",
+        "category": ["qdisc", "netem"],
+        "plugins": {
+            "requires": "nsPlugin"
+        },
+        "setup": [
+            "$IP link set lo up || true",
+            "$TC qdisc add dev lo root handle 1: netem limit 1",
+            "$TC qdisc add dev lo parent 1: handle 2: netem limit 1"
+        ],
+        "cmdUnderTest": "$TC qdisc change dev lo handle 1: netem duplicate 50% || $TC qdisc change dev lo handle 2: netem duplicate 50%",
+        "expExitCode": "2",
+        "verifyCmd": "$TC -s qdisc show dev lo",
+        "matchPattern": "qdisc netem",
+        "matchCount": "2",
+        "teardown": [
+            "$TC qdisc del dev lo handle 1:0 root"
+        ]
     }
 ]
-- 
2.43.0