selftests/tc-testing: sfq: check that a derived limit of 1 is rejected

Because the limit is updated indirectly when other parameters are
updated, there are cases where even though the user requests a limit
of 2 it can actually be set to 1.

Add the following test cases to check that the kernel rejects them:
- limit 2 depth 1 flows 1
- limit 2 depth 1 divisor 1

Signed-off-by: Octavian Purdila <tavip@google.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -228,5 +228,41 @@
         "matchCount": "0",
         "teardown": [
         ]
+    },
+    {
+        "id": "7f8f",
+        "name": "Check that a derived limit of 1 is rejected (limit 2 depth 1 flows 1)",
+        "category": [
+            "qdisc",
+            "sfq"
+        ],
+        "plugins": {
+            "requires": "nsPlugin"
+        },
+        "setup": [],
+        "cmdUnderTest": "$TC qdisc add dev $DUMMY handle 1: root sfq limit 2 depth 1 flows 1",
+        "expExitCode": "2",
+        "verifyCmd": "$TC qdisc show dev $DUMMY",
+        "matchPattern": "sfq",
+        "matchCount": "0",
+        "teardown": []
+    },
+    {
+        "id": "5168",
+        "name": "Check that a derived limit of 1 is rejected (limit 2 depth 1 divisor 1)",
+        "category": [
+            "qdisc",
+            "sfq"
+        ],
+        "plugins": {
+            "requires": "nsPlugin"
+        },
+        "setup": [],
+        "cmdUnderTest": "$TC qdisc add dev $DUMMY handle 1: root sfq limit 2 depth 1 divisor 1",
+        "expExitCode": "2",
+        "verifyCmd": "$TC qdisc show dev $DUMMY",
+        "matchPattern": "sfq",
+        "matchCount": "0",
+        "teardown": []
     }
 ]