netfilter: nftables: allow to update flowtable flags

Honor flowtable flags from the control update path. Disallow disabling
to toggle hardware offload support though.

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

include/net/netfilter/nf_tables.h

@@ -1536,6 +1536,7 @@ struct nft_trans_flowtable {
 	struct nft_flowtable		*flowtable;
 	bool				update;
 	struct list_head		hook_list;
+	u32				flags;
 };
 
 #define nft_trans_flowtable(trans)	\
@@ -1544,6 +1545,8 @@ struct nft_trans_flowtable {
 	(((struct nft_trans_flowtable *)trans->data)->update)
 #define nft_trans_flowtable_hooks(trans)	\
 	(((struct nft_trans_flowtable *)trans->data)->hook_list)
+#define nft_trans_flowtable_flags(trans)	\
+	(((struct nft_trans_flowtable *)trans->data)->flags)
 
 int __init nft_chain_filter_init(void);
 void nft_chain_filter_fini(void);

net/netfilter/nf_tables_api.c

@@ -6842,6 +6842,7 @@ static int nft_flowtable_update(struct nft_ctx *ctx, const struct nlmsghdr *nlh,
 	struct nft_hook *hook, *next;
 	struct nft_trans *trans;
 	bool unregister = false;
+	u32 flags;
 	int err;
 
 	err = nft_flowtable_parse_hook(ctx, nla[NFTA_FLOWTABLE_HOOK],
@@ -6856,6 +6857,17 @@ static int nft_flowtable_update(struct nft_ctx *ctx, const struct nlmsghdr *nlh,
 		}
 	}
 
+	if (nla[NFTA_FLOWTABLE_FLAGS]) {
+		flags = ntohl(nla_get_be32(nla[NFTA_FLOWTABLE_FLAGS]));
+		if (flags & ~NFT_FLOWTABLE_MASK)
+			return -EOPNOTSUPP;
+		if ((flowtable->data.flags & NFT_FLOWTABLE_HW_OFFLOAD) ^
+		    (flags & NFT_FLOWTABLE_HW_OFFLOAD))
+			return -EOPNOTSUPP;
+	} else {
+		flags = flowtable->data.flags;
+	}
+
 	err = nft_register_flowtable_net_hooks(ctx->net, ctx->table,
 					       &flowtable_hook.list, flowtable);
 	if (err < 0)
@@ -6869,6 +6881,7 @@ static int nft_flowtable_update(struct nft_ctx *ctx, const struct nlmsghdr *nlh,
 		goto err_flowtable_update_hook;
 	}
 
+	nft_trans_flowtable_flags(trans) = flags;
 	nft_trans_flowtable(trans) = flowtable;
 	nft_trans_flowtable_update(trans) = true;
 	INIT_LIST_HEAD(&nft_trans_flowtable_hooks(trans));
@@ -8178,6 +8191,8 @@ static int nf_tables_commit(struct net *net, struct sk_buff *skb)
 			break;
 		case NFT_MSG_NEWFLOWTABLE:
 			if (nft_trans_flowtable_update(trans)) {
+				nft_trans_flowtable(trans)->data.flags =
+					nft_trans_flowtable_flags(trans);
 				nf_tables_flowtable_notify(&trans->ctx,
 							   nft_trans_flowtable(trans),
 							   &nft_trans_flowtable_hooks(trans),