selftests/tc-testing: Check backlog stats in gso_skb case

Add tests to ensure proper backlog accounting in hhf, codel, pie, fq,
fq_pie, and fq_codel qdiscs. We check for the bug pattern originally
found in fq, fq_pie, and fq_codel, which was an underflow in the tbf
parent backlog stats upon child qdisc removal.

Signed-off-by: William Liu <[e-mail]>
Reviewed-by: Savino Dicanosa <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

tools/testing/selftests/tc-testing/tc-tests/infra/qdiscs.json

···
         ]
     },
     {
+        "id": "34c0",
+        "name": "Test TBF with HHF Backlog Accounting in gso_skb case against underflow",
+        "category": [
+            "qdisc",
+            "tbf",
+            "hhf"
+        ],
+        "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 $DUMMY root handle 1: tbf rate 8bit burst 100b latency 100ms",
+            "$TC qdisc replace dev $DUMMY handle 2: parent 1:1 hhf limit 1000",
+            [
+                "ping -I $DUMMY -c2 10.10.11.11",
+                1
+            ],
+            "$TC qdisc change dev $DUMMY handle 2: parent 1:1 hhf limit 1"
+        ],
+        "cmdUnderTest": "$TC qdisc del dev $DUMMY handle 2: parent 1:1",
+        "expExitCode": "0",
+        "verifyCmd": "$TC -s qdisc show dev $DUMMY",
+        "matchPattern": "backlog 0b 0p",
+        "matchCount": "1",
+        "teardown": [
+            "$TC qdisc del dev $DUMMY handle 1: root"
+        ]
+    },
+    {
+        "id": "fd68",
+        "name": "Test TBF with CODEL Backlog Accounting in gso_skb case against underflow",
+        "category": [
+            "qdisc",
+            "tbf",
+            "codel"
+        ],
+        "plugins": {
+            "requires": [
+                "nsPlugin"
+            ]
+        },
+        "setup": [
+            "$IP link set dev $DUMMY up || true",
+            "$IP addr add 10.10.11.10/24 dev $DUMMY || true",
+            "$TC qdisc add dev $DUMMY root handle 1: tbf rate 8bit burst 100b latency 100ms",
+            "$TC qdisc replace dev $DUMMY handle 2: parent 1:1 codel limit 1000",
+            [
+                "ping -I $DUMMY -c2 10.10.11.11",
+                1
+            ],
+            "$TC qdisc change dev $DUMMY handle 2: parent 1:1 codel limit 1"
+        ],
+        "cmdUnderTest": "$TC qdisc del dev $DUMMY handle 2: parent 1:1",
+        "expExitCode": "0",
+        "verifyCmd": "$TC -s qdisc show dev $DUMMY",
+        "matchPattern": "backlog 0b 0p",
+        "matchCount": "1",
+        "teardown": [
+            "$TC qdisc del dev $DUMMY handle 1: root"
+        ]
+    },
+    {
+        "id": "514e",
+        "name": "Test TBF with PIE Backlog Accounting in gso_skb case against underflow",
+        "category": [
+            "qdisc",
+            "tbf",
+            "pie"
+        ],
+        "plugins": {
+            "requires": [
+                "nsPlugin"
+            ]
+        },
+        "setup": [
+            "$IP link set dev $DUMMY up || true",
+            "$IP addr add 10.10.11.10/24 dev $DUMMY || true",
+            "$TC qdisc add dev $DUMMY root handle 1: tbf rate 8bit burst 100b latency 100ms",
+            "$TC qdisc replace dev $DUMMY handle 2: parent 1:1 pie limit 1000",
+            [
+                "ping -I $DUMMY -c2 10.10.11.11",
+                1
+            ],
+            "$TC qdisc change dev $DUMMY handle 2: parent 1:1 pie limit 1"
+        ],
+        "cmdUnderTest": "$TC qdisc del dev $DUMMY handle 2: parent 1:1",
+        "expExitCode": "0",
+        "verifyCmd": "$TC -s qdisc show dev $DUMMY",
+        "matchPattern": "backlog 0b 0p",
+        "matchCount": "1",
+        "teardown": [
+            "$TC qdisc del dev $DUMMY handle 1: root"
+        ]
+    },
+    {
+        "id": "6c97",
+        "name": "Test TBF with FQ Backlog Accounting in gso_skb case against underflow",
+        "category": [
+            "qdisc",
+            "tbf",
+            "fq"
+        ],
+        "plugins": {
+            "requires": [
+                "nsPlugin"
+            ]
+        },
+        "setup": [
+            "$IP link set dev $DUMMY up || true",
+            "$IP addr add 10.10.11.10/24 dev $DUMMY || true",
+            "$TC qdisc add dev $DUMMY root handle 1: tbf rate 8bit burst 100b latency 100ms",
+            "$TC qdisc replace dev $DUMMY handle 2: parent 1:1 fq limit 1000",
+            [
+                "ping -I $DUMMY -c2 10.10.11.11",
+                1
+            ],
+            "$TC qdisc change dev $DUMMY handle 2: parent 1:1 fq limit 1"
+        ],
+        "cmdUnderTest": "$TC qdisc del dev $DUMMY handle 2: parent 1:1",
+        "expExitCode": "0",
+        "verifyCmd": "$TC -s qdisc show dev $DUMMY",
+        "matchPattern": "backlog 0b 0p",
+        "matchCount": "1",
+        "teardown": [
+            "$TC qdisc del dev $DUMMY handle 1: root"
+        ]
+    },
+    {
+        "id": "5d0b",
+        "name": "Test TBF with FQ_CODEL Backlog Accounting in gso_skb case against underflow",
+        "category": [
+            "qdisc",
+            "tbf",
+            "fq_codel"
+        ],
+        "plugins": {
+            "requires": [
+                "nsPlugin"
+            ]
+        },
+        "setup": [
+            "$IP link set dev $DUMMY up || true",
+            "$IP addr add 10.10.11.10/24 dev $DUMMY || true",
+            "$TC qdisc add dev $DUMMY root handle 1: tbf rate 8bit burst 100b latency 100ms",
+            "$TC qdisc replace dev $DUMMY handle 2: parent 1:1 fq_codel limit 1000",
+            [
+                "ping -I $DUMMY -c2 10.10.11.11",
+                1
+            ],
+            "$TC qdisc change dev $DUMMY handle 2: parent 1:1 fq_codel limit 1"
+        ],
+        "cmdUnderTest": "$TC qdisc del dev $DUMMY handle 2: parent 1:1",
+        "expExitCode": "0",
+        "verifyCmd": "$TC -s qdisc show dev $DUMMY",
+        "matchPattern": "backlog 0b 0p",
+        "matchCount": "1",
+        "teardown": [
+            "$TC qdisc del dev $DUMMY handle 1: root"
+        ]
+    },
+    {
+        "id": "21c3",
+        "name": "Test TBF with FQ_PIE Backlog Accounting in gso_skb case against underflow",
+        "category": [
+            "qdisc",
+            "tbf",
+            "fq_pie"
+        ],
+        "plugins": {
+            "requires": [
+                "nsPlugin"
+            ]
+        },
+        "setup": [
+            "$IP link set dev $DUMMY up || true",
+            "$IP addr add 10.10.11.10/24 dev $DUMMY || true",
+            "$TC qdisc add dev $DUMMY root handle 1: tbf rate 8bit burst 100b latency 100ms",
+            "$TC qdisc replace dev $DUMMY handle 2: parent 1:1 fq_pie limit 1000",
+            [
+                "ping -I $DUMMY -c2 10.10.11.11",
+                1
+            ],
+            "$TC qdisc change dev $DUMMY handle 2: parent 1:1 fq_pie limit 1"
+        ],
+        "cmdUnderTest": "$TC qdisc del dev $DUMMY handle 2: parent 1:1",
+        "expExitCode": "0",
+        "verifyCmd": "$TC -s qdisc show dev $DUMMY",
+        "matchPattern": "backlog 0b 0p",
+        "matchCount": "1",
+        "teardown": [
+            "$TC qdisc del dev $DUMMY handle 1: root"
+        ]
+    },
+    {
         "id": "a4bb",
         "name": "Test FQ_CODEL with HTB parent - force packet drop with empty queue",
         "category": [