netfilter: nf_tables: allow to create netdev chain without device

Relax netdev chain creation to allow for loading the ruleset, then
adding/deleting devices at a later stage. Hardware offload does not
support for this feature yet.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Author: ummakynes

net/netfilter/nf_tables_api.c

@@ -2023,10 +2023,9 @@ struct nft_chain_hook {
 	struct list_head		list;
 };
 
-static int nft_chain_parse_netdev(struct net *net,
-				  struct nlattr *tb[],
+static int nft_chain_parse_netdev(struct net *net, struct nlattr *tb[],
 				  struct list_head *hook_list,
-				  struct netlink_ext_ack *extack)
+				  struct netlink_ext_ack *extack, u32 flags)
 {
 	struct nft_hook *hook;
 	int err;
@@ -2045,20 +2044,20 @@ static int nft_chain_parse_netdev(struct net *net,
 		if (err < 0)
 			return err;
 
-		if (list_empty(hook_list))
-			return -EINVAL;
-	} else {
-		return -EINVAL;
 	}
 
+	if (flags & NFT_CHAIN_HW_OFFLOAD &&
+	    list_empty(hook_list))
+		return -EINVAL;
+
 	return 0;
 }
 
 static int nft_chain_parse_hook(struct net *net,
 				struct nft_base_chain *basechain,
 				const struct nlattr * const nla[],
 				struct nft_chain_hook *hook, u8 family,
-				struct netlink_ext_ack *extack)
+				u32 flags, struct netlink_ext_ack *extack)
 {
 	struct nftables_pernet *nft_net = nft_pernet(net);
 	struct nlattr *ha[NFTA_HOOK_MAX + 1];
@@ -2125,7 +2124,7 @@ static int nft_chain_parse_hook(struct net *net,
 
 	INIT_LIST_HEAD(&hook->list);
 	if (nft_base_chain_netdev(family, hook->num)) {
-		err = nft_chain_parse_netdev(net, ha, &hook->list, extack);
+		err = nft_chain_parse_netdev(net, ha, &hook->list, extack, flags);
 		if (err < 0) {
 			module_put(type->owner);
 			return err;
@@ -2263,7 +2262,7 @@ static int nf_tables_addchain(struct nft_ctx *ctx, u8 family, u8 genmask,
 		if (flags & NFT_CHAIN_BINDING)
 			return -EOPNOTSUPP;
 
-		err = nft_chain_parse_hook(net, NULL, nla, &hook, family,
+		err = nft_chain_parse_hook(net, NULL, nla, &hook, family, flags,
 					   extack);
 		if (err < 0)
 			return err;
@@ -2407,7 +2406,7 @@ static int nf_tables_updchain(struct nft_ctx *ctx, u8 genmask, u8 policy,
 
 		basechain = nft_base_chain(chain);
 		err = nft_chain_parse_hook(ctx->net, basechain, nla, &hook,
-					   ctx->family, extack);
+					   ctx->family, flags, extack);
 		if (err < 0)
 			return err;
 
@@ -2683,7 +2682,7 @@ static int nft_delchain_hook(struct nft_ctx *ctx, struct nft_chain *chain,
 
 	basechain = nft_base_chain(chain);
 	err = nft_chain_parse_hook(ctx->net, basechain, nla, &chain_hook,
-				   ctx->family, extack);
+				   ctx->family, chain->flags, extack);
 	if (err < 0)
 		return err;