selftests/tc-testing: Add test for echo of big TC filters

Add a selftest that checks whether the kernel can successfully echo a
big tc filter, to test the fix introduced in commit:

369609f ("tc: Ensure we have enough buffer space when sending filter netlink notifications")

Signed-off-by: Toke Høiland-Jørgensen <[email protected]>
Tested-by: Victor Nogueira <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: tohojo

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

@@ -412,5 +412,27 @@
         "teardown": [
             "$TC qdisc del dev $DUMMY ingress"
         ]
+    },
+    {
+        "id": "33f4",
+        "name": "Check echo of big filter command",
+        "category": [
+            "infra",
+            "u32"
+        ],
+        "plugins": {
+            "requires": "nsPlugin"
+        },
+        "setup": [
+            "$TC qdisc add dev $DUMMY parent root handle 10: fq_codel"
+        ],
+        "cmdUnderTest": "bash -c '$TC -echo filter add dev $DUMMY parent 10: u32 match u32 0 0 $(for i in $(seq 32); do echo action pedit munge ip dport set 22; done) | grep \"added filter\"'",
+        "verifyCmd": "",
+        "expExitCode": "0",
+        "matchCount": "0",
+        "matchPattern": "",
+        "teardown": [
+            "$TC qdisc del dev $DUMMY parent root fq_codel"
+        ]
     }
 ]