netfilter: nf_tables: add userdata attributes to nft_chain

Enables storing userdata for nft_chain. Field udata points to user data
and udlen stores its length.

Adds new attribute flag NFTA_CHAIN_USERDATA.
Signed-off-by: Jose M. Guisado Gomez <guigom@riseup.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/netfilter/nf_tables.h

@@ -945,6 +945,8 @@ struct nft_chain {
 					bound:1,
 					genmask:2;
 	char				*name;
+	u16				udlen;
+	u8				*udata;
 
 	/* Only used during control plane commit phase: */
 	struct nft_rule			**rules_next;

include/uapi/linux/netfilter/nf_tables.h

@@ -208,6 +208,7 @@ enum nft_chain_flags {
  * @NFTA_CHAIN_COUNTERS: counter specification of the chain (NLA_NESTED: nft_counter_attributes)
  * @NFTA_CHAIN_FLAGS: chain flags
  * @NFTA_CHAIN_ID: uniquely identifies a chain in a transaction (NLA_U32)
+ * @NFTA_CHAIN_USERDATA: user data (NLA_BINARY)
  */
 enum nft_chain_attributes {
 	NFTA_CHAIN_UNSPEC,
@@ -222,6 +223,7 @@ enum nft_chain_attributes {
 	NFTA_CHAIN_PAD,
 	NFTA_CHAIN_FLAGS,
 	NFTA_CHAIN_ID,
+	NFTA_CHAIN_USERDATA,
 	__NFTA_CHAIN_MAX
 };
 #define NFTA_CHAIN_MAX		(__NFTA_CHAIN_MAX - 1)

net/netfilter/nf_tables_api.c

@@ -1304,6 +1304,8 @@ static const struct nla_policy nft_chain_policy[NFTA_CHAIN_MAX + 1] = {
 	[NFTA_CHAIN_COUNTERS]	= { .type = NLA_NESTED },
 	[NFTA_CHAIN_FLAGS]	= { .type = NLA_U32 },
 	[NFTA_CHAIN_ID]		= { .type = NLA_U32 },
+	[NFTA_CHAIN_USERDATA]	= { .type = NLA_BINARY,
+				    .len = NFT_USERDATA_MAXLEN },
 };
 
 static const struct nla_policy nft_hook_policy[NFTA_HOOK_MAX + 1] = {
@@ -1445,6 +1447,10 @@ static int nf_tables_fill_chain_info(struct sk_buff *skb, struct net *net,
 	if (nla_put_be32(skb, NFTA_CHAIN_USE, htonl(chain->use)))
 		goto nla_put_failure;
 
+	if (chain->udata &&
+	    nla_put(skb, NFTA_CHAIN_USERDATA, chain->udlen, chain->udata))
+		goto nla_put_failure;
+
 	nlmsg_end(skb, nlh);
 	return 0;
 
@@ -1682,9 +1688,11 @@ void nf_tables_chain_destroy(struct nft_ctx *ctx)
 			free_percpu(rcu_dereference_raw(basechain->stats));
 		}
 		kfree(chain->name);
+		kfree(chain->udata);
 		kfree(basechain);
 	} else {
 		kfree(chain->name);
+		kfree(chain->udata);
 		kfree(chain);
 	}
 }
@@ -2038,7 +2046,7 @@ static int nf_tables_addchain(struct nft_ctx *ctx, u8 family, u8 genmask,
 	} else {
 		if (!(flags & NFT_CHAIN_BINDING)) {
 			err = -EINVAL;
-			goto err1;
+			goto err_destroy_chain;
 		}
 
 		snprintf(name, sizeof(name), "__chain%llu", ++chain_id);
@@ -2047,13 +2055,22 @@ static int nf_tables_addchain(struct nft_ctx *ctx, u8 family, u8 genmask,
 
 	if (!chain->name) {
 		err = -ENOMEM;
-		goto err1;
+		goto err_destroy_chain;
+	}
+
+	if (nla[NFTA_CHAIN_USERDATA]) {
+		chain->udata = nla_memdup(nla[NFTA_CHAIN_USERDATA], GFP_KERNEL);
+		if (chain->udata == NULL) {
+			err = -ENOMEM;
+			goto err_destroy_chain;
+		}
+		chain->udlen = nla_len(nla[NFTA_CHAIN_USERDATA]);
 	}
 
 	rules = nf_tables_chain_alloc_rules(chain, 0);
 	if (!rules) {
 		err = -ENOMEM;
-		goto err1;
+		goto err_destroy_chain;
 	}
 
 	*rules = NULL;
@@ -2062,12 +2079,12 @@ static int nf_tables_addchain(struct nft_ctx *ctx, u8 family, u8 genmask,
 
 	err = nf_tables_register_hook(net, table, chain);
 	if (err < 0)
-		goto err1;
+		goto err_destroy_chain;
 
 	trans = nft_trans_chain_add(ctx, NFT_MSG_NEWCHAIN);
 	if (IS_ERR(trans)) {
 		err = PTR_ERR(trans);
-		goto err2;
+		goto err_unregister_hook;
 	}
 
 	nft_trans_chain_policy(trans) = NFT_CHAIN_POLICY_UNSET;
@@ -2077,15 +2094,15 @@ static int nf_tables_addchain(struct nft_ctx *ctx, u8 family, u8 genmask,
 	err = nft_chain_add(table, chain);
 	if (err < 0) {
 		nft_trans_destroy(trans);
-		goto err2;
+		goto err_unregister_hook;
 	}
 
 	table->use++;
 
 	return 0;
-err2:
+err_unregister_hook:
 	nf_tables_unregister_hook(net, table, chain);
-err1:
+err_destroy_chain:
 	nf_tables_chain_destroy(ctx);
 
 	return err;