Merge branch 'net_sched-adapt-qdiscs-for-reentrant-enqueue-cases'

Victor Nogueira says:

====================
net_sched: Adapt qdiscs for reentrant enqueue cases

As described in Gerrard's report [1], there are cases where netem can
make the qdisc enqueue callback reentrant. Some qdiscs (drr, hfsc, ets,
qfq) break whenever the enqueue callback has reentrant behaviour.
This series addresses these issues by adding extra checks that cater for
these reentrant corner cases. This series has passed all relevant test
cases in the TDC suite.

[1] https://lore.kernel.org/netdev/CAHcdcOm+03OD2j6R0=YHKqmy=VgJ8xEOKuP6c7mSgnp-TEJJbw@mail.gmail.com/
====================

Link: https://patch.msgid.link/20250425220710.3964791-1-victor@mojatatu.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 186 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 e26bbc169783..0843f6d37e9c 100644
--- a/tools/testing/selftests/tc-testing/tc-tests/infra/qdiscs.json
+++ b/tools/testing/selftests/tc-testing/tc-tests/infra/qdiscs.json
@@ -352,5 +352,191 @@
             "$TC qdisc del dev $DUMMY handle 1:0 root",
             "$IP addr del 10.10.10.10/24 dev $DUMMY || true"
         ]
+    },
+    {
+        "id": "90ec",
+        "name": "Test DRR's enqueue reentrant behaviour with netem",
+        "category": [
+            "qdisc",
+            "drr"
+        ],
+        "plugins": {
+            "requires": "nsPlugin"
+        },
+        "setup": [
+            "$IP link set dev $DUMMY up || true",
+            "$IP addr add 10.10.10.10/24 dev $DUMMY || true",
+            "$TC qdisc add dev $DUMMY handle 1:0 root drr",
+            "$TC class replace dev $DUMMY parent 1:0 classid 1:1 drr",
+            "$TC qdisc add dev $DUMMY parent 1:1 handle 2:0 netem duplicate 100%",
+            "$TC filter add dev $DUMMY parent 1:0 protocol ip prio 1 u32 match ip protocol 1 0xff flowid 1:1"
+        ],
+        "cmdUnderTest": "ping -c 1 -I $DUMMY 10.10.10.1 > /dev/null || true",
+        "expExitCode": "0",
+        "verifyCmd": "$TC -j -s qdisc ls dev $DUMMY handle 1:0",
+        "matchJSON": [
+            {
+                "kind": "drr",
+                "handle": "1:",
+                "bytes": 196,
+                "packets": 2
+            }
+        ],
+        "matchCount": "1",
+        "teardown": [
+            "$TC qdisc del dev $DUMMY handle 1:0 root",
+            "$IP addr del 10.10.10.10/24 dev $DUMMY || true"
+        ]
+    },
+    {
+        "id": "1f1f",
+        "name": "Test ETS's enqueue reentrant behaviour with netem",
+        "category": [
+            "qdisc",
+            "ets"
+        ],
+        "plugins": {
+            "requires": "nsPlugin"
+        },
+        "setup": [
+            "$IP link set dev $DUMMY up || true",
+            "$IP addr add 10.10.10.10/24 dev $DUMMY || true",
+            "$TC qdisc add dev $DUMMY handle 1:0 root ets bands 2",
+            "$TC class replace dev $DUMMY parent 1:0 classid 1:1 ets quantum 1500",
+            "$TC qdisc add dev $DUMMY parent 1:1 handle 2:0 netem duplicate 100%",
+            "$TC filter add dev $DUMMY parent 1:0 protocol ip prio 1 u32 match ip protocol 1 0xff flowid 1:1"
+        ],
+        "cmdUnderTest": "ping -c 1 -I $DUMMY 10.10.10.1 > /dev/null || true",
+        "expExitCode": "0",
+        "verifyCmd": "$TC -j -s class show dev $DUMMY",
+        "matchJSON": [
+            {
+                "class": "ets",
+                "handle": "1:1",
+                "stats": {
+                    "bytes": 196,
+                    "packets": 2
+                }
+            }
+        ],
+        "matchCount": "1",
+        "teardown": [
+            "$TC qdisc del dev $DUMMY handle 1:0 root",
+            "$IP addr del 10.10.10.10/24 dev $DUMMY || true"
+        ]
+    },
+    {
+        "id": "5e6d",
+        "name": "Test QFQ's enqueue reentrant behaviour with netem",
+        "category": [
+            "qdisc",
+            "qfq"
+        ],
+        "plugins": {
+            "requires": "nsPlugin"
+        },
+        "setup": [
+            "$IP link set dev $DUMMY up || true",
+            "$IP addr add 10.10.10.10/24 dev $DUMMY || true",
+            "$TC qdisc add dev $DUMMY handle 1:0 root qfq",
+            "$TC class replace dev $DUMMY parent 1:0 classid 1:1 qfq weight 100 maxpkt 1500",
+            "$TC qdisc add dev $DUMMY parent 1:1 handle 2:0 netem duplicate 100%",
+            "$TC filter add dev $DUMMY parent 1:0 protocol ip prio 1 u32 match ip protocol 1 0xff flowid 1:1"
+        ],
+        "cmdUnderTest": "ping -c 1 -I $DUMMY 10.10.10.1 > /dev/null || true",
+        "expExitCode": "0",
+        "verifyCmd": "$TC -j -s qdisc ls dev $DUMMY handle 1:0",
+        "matchJSON": [
+            {
+                "kind": "qfq",
+                "handle": "1:",
+                "bytes": 196,
+                "packets": 2
+            }
+        ],
+        "matchCount": "1",
+        "teardown": [
+            "$TC qdisc del dev $DUMMY handle 1:0 root",
+            "$IP addr del 10.10.10.10/24 dev $DUMMY || true"
+        ]
+    },
+    {
+        "id": "bf1d",
+        "name": "Test HFSC's enqueue reentrant behaviour with netem",
+        "category": [
+            "qdisc",
+            "hfsc"
+        ],
+        "plugins": {
+            "requires": "nsPlugin"
+        },
+        "setup": [
+            "$IP link set dev $DUMMY up || true",
+            "$IP addr add 10.10.10.10/24 dev $DUMMY || true",
+            "$TC qdisc add dev $DUMMY handle 1:0 root hfsc",
+            "$TC class add dev $DUMMY parent 1:0 classid 1:1 hfsc ls m2 10Mbit",
+            "$TC qdisc add dev $DUMMY parent 1:1 handle 2:0 netem duplicate 100%",
+            "$TC filter add dev $DUMMY parent 1:0 protocol ip prio 1 u32 match ip dst 10.10.10.1/32 flowid 1:1",
+            "$TC class add dev $DUMMY parent 1:0 classid 1:2 hfsc ls m2 10Mbit",
+            "$TC qdisc add dev $DUMMY parent 1:2 handle 3:0 netem duplicate 100%",
+            "$TC filter add dev $DUMMY parent 1:0 protocol ip prio 2 u32 match ip dst 10.10.10.2/32 flowid 1:2",
+            "ping -c 1 10.10.10.1 -I$DUMMY > /dev/null || true",
+            "$TC filter del dev $DUMMY parent 1:0 protocol ip prio 1",
+            "$TC class del dev $DUMMY classid 1:1"
+        ],
+        "cmdUnderTest": "ping -c 1 10.10.10.2 -I$DUMMY > /dev/null || true",
+        "expExitCode": "0",
+        "verifyCmd": "$TC -j -s qdisc ls dev $DUMMY handle 1:0",
+        "matchJSON": [
+            {
+                "kind": "hfsc",
+                "handle": "1:",
+                "bytes": 392,
+                "packets": 4
+            }
+        ],
+        "matchCount": "1",
+        "teardown": [
+            "$TC qdisc del dev $DUMMY handle 1:0 root",
+            "$IP addr del 10.10.10.10/24 dev $DUMMY || true"
+        ]
+    },
+    {
+        "id": "7c3b",
+        "name": "Test nested DRR's enqueue reentrant behaviour with netem",
+        "category": [
+            "qdisc",
+            "drr"
+        ],
+        "plugins": {
+            "requires": "nsPlugin"
+        },
+        "setup": [
+            "$IP link set dev $DUMMY up || true",
+            "$IP addr add 10.10.10.10/24 dev $DUMMY || true",
+            "$TC qdisc add dev $DUMMY handle 1:0 root drr",
+            "$TC class add dev $DUMMY parent 1:0 classid 1:1 drr",
+            "$TC filter add dev $DUMMY parent 1:0 protocol ip prio 1 u32 match ip protocol 1 0xff flowid 1:1",
+            "$TC qdisc add dev $DUMMY handle 2:0 parent 1:1 drr",
+            "$TC class add dev $DUMMY classid 2:1 parent 2:0 drr",
+            "$TC filter add dev $DUMMY parent 2:0 protocol ip prio 1 u32 match ip protocol 1 0xff flowid 2:1",
+            "$TC qdisc add dev $DUMMY parent 2:1 handle 3:0 netem duplicate 100%"
+        ],
+        "cmdUnderTest": "ping -c 1 -I $DUMMY 10.10.10.1 > /dev/null || true",
+        "expExitCode": "0",
+        "verifyCmd": "$TC -j -s qdisc ls dev $DUMMY handle 1:0",
+        "matchJSON": [
+            {
+                "kind": "drr",
+                "handle": "1:",
+                "bytes": 196,
+                "packets": 2
+            }
+        ],
+        "matchCount": "1",
+        "teardown": [
+            "$TC qdisc del dev $DUMMY handle 1:0 root",
+            "$IP addr del 10.10.10.10/24 dev $DUMMY || true"
+        ]
     }
 ]