netfilter: nf_tables: Eliminate duplicated code in nf_tables_table_enable()

If something fails in nf_tables_table_enable(), it unregisters the
chains. But the rollback code is the same as nf_tables_table_disable()
almostly, except there is one counter check.  Now create one wrapper
function to eliminate the duplicated codes.
Signed-off-by: NFeng <fgao@ikuai8.com>
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_api.c

@@ -576,6 +576,28 @@ static int nf_tables_gettable(struct net *net, struct sock *nlsk,
 	return err;
 }
 
+static void _nf_tables_table_disable(struct net *net,
+				     const struct nft_af_info *afi,
+				     struct nft_table *table,
+				     u32 cnt)
+{
+	struct nft_chain *chain;
+	u32 i = 0;
+
+	list_for_each_entry(chain, &table->chains, list) {
+		if (!nft_is_active_next(net, chain))
+			continue;
+		if (!(chain->flags & NFT_BASE_CHAIN))
+			continue;
+
+		if (cnt && i++ == cnt)
+			break;
+
+		nf_unregister_net_hooks(net, nft_base_chain(chain)->ops,
+					afi->nops);
+	}
+}
+
 static int nf_tables_table_enable(struct net *net,
 				  const struct nft_af_info *afi,
 				  struct nft_table *table)
@@ -598,18 +620,8 @@ static int nf_tables_table_enable(struct net *net,
 	}
 	return 0;
 err:
-	list_for_each_entry(chain, &table->chains, list) {
-		if (!nft_is_active_next(net, chain))
-			continue;
-		if (!(chain->flags & NFT_BASE_CHAIN))
-			continue;
-
-		if (i-- <= 0)
-			break;
-
-		nf_unregister_net_hooks(net, nft_base_chain(chain)->ops,
-					afi->nops);
-	}
+	if (i)
+		_nf_tables_table_disable(net, afi, table, i);
 	return err;
 }
 
@@ -617,17 +629,7 @@ static void nf_tables_table_disable(struct net *net,
 				    const struct nft_af_info *afi,
 				    struct nft_table *table)
 {
-	struct nft_chain *chain;
-
-	list_for_each_entry(chain, &table->chains, list) {
-		if (!nft_is_active_next(net, chain))
-			continue;
-		if (!(chain->flags & NFT_BASE_CHAIN))
-			continue;
-
-		nf_unregister_net_hooks(net, nft_base_chain(chain)->ops,
-					afi->nops);
-	}
+	_nf_tables_table_disable(net, afi, table, 0);
 }
 
 static int nf_tables_updtable(struct nft_ctx *ctx)