netfilter: nf_tables: unbind callbacks from flowtable destroy path

Callback unbinding needs to be done after nf_flow_table_free(),
otherwise entries are not removed from the hardware.

Update nft_unregister_flowtable_net_hooks() to call
nf_unregister_net_hook() instead since the commit/abort paths do not
deal with the callback unbinding anymore.

Add a comment to nft_flowtable_event() to clarify that
flow_offload_netdev_event() already removes the entries before the
callback unbinding.

Fixes: 8bb69f3b ("netfilter: nf_tables: add flowtable offload control plane")
Fixes ff4bf2f4 ("netfilter: nf_tables: add nft_unregister_flowtable_hook()")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Acked-by: wenxu <wenxu@ucloud.cn>

net/netfilter/nf_tables_api.c

@@ -5984,6 +5984,7 @@ nft_flowtable_type_get(struct net *net, u8 family)
 	return ERR_PTR(-ENOENT);
 }
 
+/* Only called from error and netdev event paths. */
 static void nft_unregister_flowtable_hook(struct net *net,
 					  struct nft_flowtable *flowtable,
 					  struct nft_hook *hook)
@@ -5999,7 +6000,7 @@ static void nft_unregister_flowtable_net_hooks(struct net *net,
 	struct nft_hook *hook;
 
 	list_for_each_entry(hook, &flowtable->hook_list, list)
-		nft_unregister_flowtable_hook(net, flowtable, hook);
+		nf_unregister_net_hook(net, &hook->ops);
 }
 
 static int nft_register_flowtable_net_hooks(struct net *net,
@@ -6448,12 +6449,14 @@ static void nf_tables_flowtable_destroy(struct nft_flowtable *flowtable)
 {
 	struct nft_hook *hook, *next;
 
+	flowtable->data.type->free(&flowtable->data);
 	list_for_each_entry_safe(hook, next, &flowtable->hook_list, list) {
+		flowtable->data.type->setup(&flowtable->data, hook->ops.dev,
+					    FLOW_BLOCK_UNBIND);
 		list_del_rcu(&hook->list);
 		kfree(hook);
 	}
 	kfree(flowtable->name);
-	flowtable->data.type->free(&flowtable->data);
 	module_put(flowtable->data.type->owner);
 	kfree(flowtable);
 }
@@ -6497,6 +6500,7 @@ static void nft_flowtable_event(unsigned long event, struct net_device *dev,
 		if (hook->ops.dev != dev)
 			continue;
 
+		/* flow_offload_netdev_event() cleans up entries for us. */
 		nft_unregister_flowtable_hook(dev_net(dev), flowtable, hook);
 		list_del_rcu(&hook->list);
 		kfree_rcu(hook, rcu);