netfilter: nf_tables: Add new attributes into nft_set to store user data.

User data is stored at after 'nft_set_ops' private data into 'data[]'
flexible array. The field 'udata' points to user data and 'udlen' stores
its length.

Add new flag NFTA_SET_USERDATA.
Signed-off-by: Carlos Falgueras García <carlosfg@riseup.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/netfilter/nf_tables.h

@@ -291,6 +291,8 @@ void nft_unregister_set(struct nft_set_ops *ops);
  * 	@timeout: default timeout value in msecs
  * 	@gc_int: garbage collection interval in msecs
  *	@policy: set parameterization (see enum nft_set_policies)
+ *	@udlen: user data length
+ *	@udata: user data
  * 	@ops: set ops
  * 	@pnet: network namespace
  * 	@flags: set flags
@@ -310,6 +312,8 @@ struct nft_set {
 	u64				timeout;
 	u32				gc_int;
 	u16				policy;
+	u16				udlen;
+	unsigned char			*udata;
 	/* runtime data below here */
 	const struct nft_set_ops	*ops ____cacheline_aligned;
 	possible_net_t			pnet;

include/uapi/linux/netfilter/nf_tables.h

@@ -291,6 +291,7 @@ enum nft_set_desc_attributes {
  * @NFTA_SET_ID: uniquely identifies a set in a transaction (NLA_U32)
  * @NFTA_SET_TIMEOUT: default timeout value (NLA_U64)
  * @NFTA_SET_GC_INTERVAL: garbage collection interval (NLA_U32)
+ * @NFTA_SET_USERDATA: user data (NLA_BINARY)
  */
 enum nft_set_attributes {
 	NFTA_SET_UNSPEC,
@@ -306,6 +307,7 @@ enum nft_set_attributes {
 	NFTA_SET_ID,
 	NFTA_SET_TIMEOUT,
 	NFTA_SET_GC_INTERVAL,
+	NFTA_SET_USERDATA,
 	__NFTA_SET_MAX
 };
 #define NFTA_SET_MAX		(__NFTA_SET_MAX - 1)

net/netfilter/nf_tables_api.c

@@ -2323,6 +2323,8 @@ static const struct nla_policy nft_set_policy[NFTA_SET_MAX + 1] = {
 	[NFTA_SET_ID]			= { .type = NLA_U32 },
 	[NFTA_SET_TIMEOUT]		= { .type = NLA_U64 },
 	[NFTA_SET_GC_INTERVAL]		= { .type = NLA_U32 },
+	[NFTA_SET_USERDATA]		= { .type = NLA_BINARY,
+					    .len  = NFT_USERDATA_MAXLEN },
 };
 
 static const struct nla_policy nft_set_desc_policy[NFTA_SET_DESC_MAX + 1] = {
@@ -2482,6 +2484,9 @@ static int nf_tables_fill_set(struct sk_buff *skb, const struct nft_ctx *ctx,
 			goto nla_put_failure;
 	}
 
+	if (nla_put(skb, NFTA_SET_USERDATA, set->udlen, set->udata))
+		goto nla_put_failure;
+
 	desc = nla_nest_start(skb, NFTA_SET_DESC);
 	if (desc == NULL)
 		goto nla_put_failure;
@@ -2691,6 +2696,8 @@ static int nf_tables_newset(struct net *net, struct sock *nlsk,
 	u64 timeout;
 	u32 ktype, dtype, flags, policy, gc_int;
 	struct nft_set_desc desc;
+	unsigned char *udata;
+	u16 udlen;
 	int err;
 
 	if (nla[NFTA_SET_TABLE] == NULL ||
@@ -2803,12 +2810,16 @@ static int nf_tables_newset(struct net *net, struct sock *nlsk,
 	if (IS_ERR(ops))
 		return PTR_ERR(ops);
 
+	udlen = 0;
+	if (nla[NFTA_SET_USERDATA])
+		udlen = nla_len(nla[NFTA_SET_USERDATA]);
+
 	size = 0;
 	if (ops->privsize != NULL)
 		size = ops->privsize(nla);
 
 	err = -ENOMEM;
-	set = kzalloc(sizeof(*set) + size, GFP_KERNEL);
+	set = kzalloc(sizeof(*set) + size + udlen, GFP_KERNEL);
 	if (set == NULL)
 		goto err1;
 
@@ -2817,6 +2828,12 @@ static int nf_tables_newset(struct net *net, struct sock *nlsk,
 	if (err < 0)
 		goto err2;
 
+	udata = NULL;
+	if (udlen) {
+		udata = set->data + size;
+		nla_memcpy(udata, nla[NFTA_SET_USERDATA], udlen);
+	}
+
 	INIT_LIST_HEAD(&set->bindings);
 	write_pnet(&set->pnet, net);
 	set->ops   = ops;
@@ -2827,6 +2844,8 @@ static int nf_tables_newset(struct net *net, struct sock *nlsk,
 	set->flags = flags;
 	set->size  = desc.size;
 	set->policy = policy;
+	set->udlen  = udlen;
+	set->udata  = udata;
 	set->timeout = timeout;
 	set->gc_int = gc_int;