net: ethernet: mtk_eth_soc: mtk_ppe: prefer newly added l2 flows

When a device is roaming between interfaces and a new flow entry is
created, we should assume that its output device is more up to date than
whatever entry existed already.
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mediatek/mtk_ppe.c

@@ -635,10 +635,20 @@ void mtk_foe_entry_clear(struct mtk_ppe *ppe, struct mtk_flow_entry *entry)
 static int
 mtk_foe_entry_commit_l2(struct mtk_ppe *ppe, struct mtk_flow_entry *entry)
 {
+	struct mtk_flow_entry *prev;
+
 	entry->type = MTK_FLOW_TYPE_L2;
 
-	return rhashtable_insert_fast(&ppe->l2_flows, &entry->l2_node,
-				      mtk_flow_l2_ht_params);
+	prev = rhashtable_lookup_get_insert_fast(&ppe->l2_flows, &entry->l2_node,
+						 mtk_flow_l2_ht_params);
+	if (likely(!prev))
+		return 0;
+
+	if (IS_ERR(prev))
+		return PTR_ERR(prev);
+
+	return rhashtable_replace_fast(&ppe->l2_flows, &prev->l2_node,
+				       &entry->l2_node, mtk_flow_l2_ht_params);
 }
 
 int mtk_foe_entry_commit(struct mtk_ppe *ppe, struct mtk_flow_entry *entry)