[PATCH net v2 2/2] selftests: tc-testing: add a lateral-drift hfsc classify-walk test

[Jamal Hadi Salim <jhs@mojatatu.com>]

The classify-loop fix bounds the number of consecutive lateral
hops, so the guard must not misfire on a legal
walk that reaches its leaf through a level-drift lateral chain. Add a
case that builds exactly that chain (root -> 1:1 -> 1:2 -> 1:3 ->
leaf 1:31, with 1:2/1:3 deepened to interior level 1 after the binds)
and asserts traffic still reaches the leaf. Passes on the patched
kernel; on a too-tight bound it would drop the packet instead.

Reviewed-by: Victor Nogueira <victor@mojatatu.com>
Tested-by: hybris <hybris@mojatatu.ai>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
---
 .../tc-testing/tc-tests/qdiscs/hfsc.json      | 34 +++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/tools/testing/selftests/tc-testing/tc-tests/qdiscs/hfsc.json b/tools/testing/selftests/tc-testing/tc-tests/qdiscs/hfsc.json
index c98c339424d4..82d2f8af1460 100644
--- a/tools/testing/selftests/tc-testing/tc-tests/qdiscs/hfsc.json
+++ b/tools/testing/selftests/tc-testing/tc-tests/qdiscs/hfsc.json
@@ -169,5 +169,39 @@
         "teardown": [
             "$TC qdisc del dev $DUMMY handle 1: root"
         ]
+    },
+    {
+        "id": "8c39",
+        "name": "HFSC classify walk still reaches leaf after lateral drift",
+        "category": [
+            "qdisc",
+            "hfsc"
+        ],
+        "plugins": {
+            "requires": "nsPlugin"
+        },
+        "setup": [
+            "ip link set lo up",
+            "$TC qdisc add dev lo handle 1: root hfsc default 31",
+            "$TC class add dev lo parent 1: classid 1:1 hfsc rt m2 100kbit",
+            "$TC class add dev lo parent 1: classid 1:2 hfsc rt m2 100kbit",
+            "$TC class add dev lo parent 1: classid 1:3 hfsc rt m2 100kbit",
+            "$TC class add dev lo parent 1:1 classid 1:10 hfsc rt m2 50kbit",
+            "$TC class add dev lo parent 1:2 classid 1:20 hfsc rt m2 10kbit",
+            "$TC class add dev lo parent 1:3 classid 1:30 hfsc rt m2 10kbit",
+            "$TC class add dev lo parent 1:3 classid 1:31 hfsc rt m2 100kbit",
+            "$TC filter add dev lo parent 1: protocol ip prio 1 u32 match u8 0 0 at 0 flowid 1:1",
+            "$TC filter add dev lo parent 1:1 protocol ip prio 1 u32 match u8 0 0 at 0 flowid 1:2",
+            "$TC filter add dev lo parent 1:2 protocol ip prio 1 u32 match u8 0 0 at 0 flowid 1:3",
+            "$TC filter add dev lo parent 1:3 protocol ip prio 1 u32 match u8 0 0 at 0 flowid 1:31"
+        ],
+        "cmdUnderTest": "ping -n -c 10 -W 1 127.0.0.1; sleep 1",
+        "expExitCode": "0",
+        "verifyCmd": "$TC -s class show dev lo",
+        "matchPattern": "class hfsc 1:31 parent 1:3 rt.*\\n.*Sent [0-9]+ bytes [1-9][0-9]* pkt",
+        "matchCount": "1",
+        "teardown": [
+            "$TC qdisc del dev lo handle 1: root"
+        ]
     }
 ]
-- 
2.43.0