net: sched: flower: use correct ht function to prevent duplicates

Implementation of function rhashtable_insert_fast() check if its internal
helper function __rhashtable_insert_fast() returns non-NULL pointer and
seemingly return -EEXIST in such case. However, since
__rhashtable_insert_fast() is called with NULL key pointer, it never
actually checks for duplicates, which means that -EEXIST is never returned
to the user. Use rhashtable_lookup_insert_fast() hash table API instead. In
order to verify that it works as expected and prevent the problem from
happening in future, extend tc-tests with new test that verifies that no
new filters with existing key can be inserted to flower classifier.

Fixes: 1f17f774 ("net: sched: flower: insert filter to ht before offloading it to hw")
Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/cls_flower.c

@@ -1466,7 +1466,7 @@ static int fl_ht_insert_unique(struct cls_fl_filter *fnew,
 	struct fl_flow_mask *mask = fnew->mask;
 	int err;
 
-	err = rhashtable_insert_fast(&mask->ht,
+	err = rhashtable_lookup_insert_fast(&mask->ht,
 					    &fnew->ht_node,
 					    mask->filter_ht_params);
 	if (err) {

tools/testing/selftests/tc-testing/tc-tests/filters/tests.json

@@ -58,5 +58,25 @@
             "$TC qdisc del dev $DEV2 ingress",
             "/bin/rm $BATCH_FILE"
         ]
+    },
+    {
+        "id": "4cbd",
+        "name": "Try to add filter with duplicate key",
+        "category": [
+            "filter",
+            "flower"
+        ],
+        "setup": [
+            "$TC qdisc add dev $DEV2 ingress",
+            "$TC filter add dev $DEV2 protocol ip prio 1 parent ffff: flower dst_mac e4:11:22:11:4a:51 src_mac e4:11:22:11:4a:50 ip_proto tcp src_ip 1.1.1.1 dst_ip 2.2.2.2 action drop"
+        ],
+        "cmdUnderTest": "$TC filter add dev $DEV2 protocol ip prio 1 parent ffff: flower dst_mac e4:11:22:11:4a:51 src_mac e4:11:22:11:4a:50 ip_proto tcp src_ip 1.1.1.1 dst_ip 2.2.2.2 action drop",
+        "expExitCode": "2",
+        "verifyCmd": "$TC -s filter show dev $DEV2 ingress",
+        "matchPattern": "filter protocol ip pref 1 flower chain 0 handle",
+        "matchCount": "1",
+        "teardown": [
+            "$TC qdisc del dev $DEV2 ingress"
+        ]
     }
 ]