netfilter: nfnetlink_hook: Dump flowtable info

Introduce NFNL_HOOK_TYPE_NFT_FLOWTABLE to distinguish flowtable hooks
from base chain ones. Nested attributes are shared with the old NFTABLES
hook info type since they fit apart from their misleading name.

Old nftables in user space will ignore this new hook type and thus
continue to print flowtable hooks just like before, e.g.:

| family netdev {
| hook ingress device test0 {
| 0000000000 nf_flow_offload_ip_hook [nf_flow_table]
| }
| }

With this patch in place and support for the new hook info type, output
becomes more useful:

| family netdev {
| hook ingress device test0 {
| 0000000000 flowtable ip mytable myft [nf_flow_table]
| }
| }

Suggested-by: Florian Westphal <[e-mail]>
Signed-off-by: Phil Sutter <[e-mail]>
Reviewed-by: Florian Westphal <[e-mail]>
Signed-off-by: Pablo Neira Ayuso <[e-mail]>

include/linux/netfilter.h

···
 	NF_HOOK_OP_UNDEFINED,
 	NF_HOOK_OP_NF_TABLES,
 	NF_HOOK_OP_BPF,
+	NF_HOOK_OP_NFT_FT,
 };
 
 struct nf_hook_ops {

include/uapi/linux/netfilter/nfnetlink_hook.h

···
  *
  * @NFNL_HOOK_TYPE_NFTABLES: nf_tables base chain
  * @NFNL_HOOK_TYPE_BPF: bpf program
+ * @NFNL_HOOK_TYPE_NFT_FLOWTABLE: nf_tables flowtable
  */
 enum nfnl_hook_chaintype {
 	NFNL_HOOK_TYPE_NFTABLES = 0x1,
 	NFNL_HOOK_TYPE_BPF,
+	NFNL_HOOK_TYPE_NFT_FLOWTABLE,
 };
 
 /**

net/netfilter/nf_tables_api.c

···
 
 	list_for_each_entry(hook, &flowtable_hook->list, list) {
 		list_for_each_entry(ops, &hook->ops_list, list) {
-			ops->pf		= NFPROTO_NETDEV;
-			ops->hooknum	= flowtable_hook->num;
-			ops->priority	= flowtable_hook->priority;
-			ops->priv	= &flowtable->data;
-			ops->hook	= flowtable->data.type->hook;
+			ops->pf			= NFPROTO_NETDEV;
+			ops->hooknum		= flowtable_hook->num;
+			ops->priority		= flowtable_hook->priority;
+			ops->priv		= &flowtable->data;
+			ops->hook		= flowtable->data.type->hook;
+			ops->hook_ops_type	= NF_HOOK_OP_NFT_FT;
 		}
 	}
 
···
 			if (!ops)
 				return 1;
 
-			ops->pf		= NFPROTO_NETDEV;
-			ops->hooknum	= flowtable->hooknum;
-			ops->priority	= flowtable->data.priority;
-			ops->priv	= &flowtable->data;
-			ops->hook	= flowtable->data.type->hook;
-			ops->dev	= dev;
+			ops->pf			= NFPROTO_NETDEV;
+			ops->hooknum		= flowtable->hooknum;
+			ops->priority		= flowtable->data.priority;
+			ops->priv		= &flowtable->data;
+			ops->hook		= flowtable->data.type->hook;
+			ops->hook_ops_type	= NF_HOOK_OP_NFT_FT;
+			ops->dev		= dev;
 			if (nft_register_flowtable_ops(dev_net(dev),
 						       flowtable, ops)) {
 				kfree(ops);

net/netfilter/nfnetlink_hook.c

···
 	return 0;
 }
 
+static int nfnl_hook_put_nft_ft_info(struct sk_buff *nlskb,
+				     const struct nfnl_dump_hook_data *ctx,
+				     unsigned int seq,
+				     struct nf_flowtable *nf_ft)
+{
+	struct nft_flowtable *ft =
+		container_of(nf_ft, struct nft_flowtable, data);
+	struct net *net = sock_net(nlskb->sk);
+	struct nlattr *nest;
+	int ret = 0;
+
+	if (WARN_ON_ONCE(!nf_ft))
+		return 0;
+
+	if (!nft_is_active(net, ft))
+		return 0;
+
+	nest = nfnl_start_info_type(nlskb, NFNL_HOOK_TYPE_NFT_FLOWTABLE);
+	if (!nest)
+		return -EMSGSIZE;
+
+	ret = nfnl_hook_put_nft_info_desc(nlskb, ft->table->name,
+					  ft->name, ft->table->family);
+	if (ret) {
+		nla_nest_cancel(nlskb, nest);
+		return ret;
+	}
+
+	nla_nest_end(nlskb, nest);
+	return 0;
+}
+
 static int nfnl_hook_dump_one(struct sk_buff *nlskb,
 			      const struct nfnl_dump_hook_data *ctx,
 			      const struct nf_hook_ops *ops,
···
 		break;
 	case NF_HOOK_OP_BPF:
 		ret = nfnl_hook_put_bpf_prog_info(nlskb, ctx, seq, ops->priv);
+		break;
+	case NF_HOOK_OP_NFT_FT:
+		ret = nfnl_hook_put_nft_ft_info(nlskb, ctx, seq, ops->priv);
 		break;
 	case NF_HOOK_OP_UNDEFINED:
 		break;