netfilter: nf_tables: store new sets in dedicated list

nft_set_lookup_byid() is very slow when transaction becomes large, due to
walk of the transaction list.

Add a dedicated list that contains only the new sets.

Before: nft -f ruleset 0.07s user 0.00s system 0% cpu 1:04.84 total
After: nft -f ruleset 0.07s user 0.00s system 0% cpu 30.115 total

.. where ruleset contains ~10 sets with ~100k elements.
The above number is for a combined flush+reload of the ruleset.

With previous flush, even the first NEWELEM has to walk through a few
hundred thousands of DELSET(ELEM) transactions before the first NEWSET
object. To cope with random-order-newset-newsetelem we'd need to replace
commit_set_list with a hashtable.

Expectation is that a NEWELEM operation refers to the most recently added
set, so last entry of the dedicated list should be the set we want.

NB: This is not a bug fix per se (functionality is fine), but with
larger transaction batches list search takes forever, so it would be
nice to speed this up for -stable too, hence adding a "fixes" tag.

Fixes: 958bee14 ("netfilter: nf_tables: use new transaction infrastructure to handle sets")
Reported-by: Nadia Pinaeva <n.m.pinaeva@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/netfilter/nf_tables.h

@@ -1674,6 +1674,7 @@ struct nft_trans_rule {
 
 struct nft_trans_set {
 	struct nft_trans_binding	nft_trans_binding;
+	struct list_head		list_trans_newset;
 	struct nft_set			*set;
 	u32				set_id;
 	u32				gc_int;
@@ -1875,6 +1876,7 @@ static inline int nft_request_module(struct net *net, const char *fmt, ...) { re
 struct nftables_pernet {
 	struct list_head	tables;
 	struct list_head	commit_list;
+	struct list_head	commit_set_list;
 	struct list_head	binding_list;
 	struct list_head	module_list;
 	struct list_head	notify_list;

net/netfilter/nf_tables_api.c

@@ -393,6 +393,7 @@ static void nft_trans_commit_list_add_tail(struct net *net, struct nft_trans *tr
 {
 	struct nftables_pernet *nft_net = nft_pernet(net);
 	struct nft_trans_binding *binding;
+	struct nft_trans_set *trans_set;
 
 	list_add_tail(&trans->list, &nft_net->commit_list);
 
@@ -402,9 +403,13 @@ static void nft_trans_commit_list_add_tail(struct net *net, struct nft_trans *tr
 
 	switch (trans->msg_type) {
 	case NFT_MSG_NEWSET:
+		trans_set = nft_trans_container_set(trans);
+
 		if (!nft_trans_set_update(trans) &&
 		    nft_set_is_anonymous(nft_trans_set(trans)))
 			list_add_tail(&binding->binding_list, &nft_net->binding_list);
+
+		list_add_tail(&trans_set->list_trans_newset, &nft_net->commit_set_list);
 		break;
 	case NFT_MSG_NEWCHAIN:
 		if (!nft_trans_chain_update(trans) &&
@@ -611,6 +616,7 @@ static int __nft_trans_set_add(const struct nft_ctx *ctx, int msg_type,
 
 	trans_set = nft_trans_container_set(trans);
 	INIT_LIST_HEAD(&trans_set->nft_trans_binding.binding_list);
+	INIT_LIST_HEAD(&trans_set->list_trans_newset);
 
 	if (msg_type == NFT_MSG_NEWSET && ctx->nla[NFTA_SET_ID] && !desc) {
 		nft_trans_set_id(trans) =
@@ -4485,17 +4491,16 @@ static struct nft_set *nft_set_lookup_byid(const struct net *net,
 {
 	struct nftables_pernet *nft_net = nft_pernet(net);
 	u32 id = ntohl(nla_get_be32(nla));
-	struct nft_trans *trans;
+	struct nft_trans_set *trans;
 
-	list_for_each_entry(trans, &nft_net->commit_list, list) {
-		if (trans->msg_type == NFT_MSG_NEWSET) {
-			struct nft_set *set = nft_trans_set(trans);
+	/* its likely the id we need is at the tail, not at start */
+	list_for_each_entry_reverse(trans, &nft_net->commit_set_list, list_trans_newset) {
+		struct nft_set *set = trans->set;
 
-			if (id == nft_trans_set_id(trans) &&
-			    set->table == table &&
-			    nft_active_genmask(set, genmask))
-				return set;
-		}
+		if (id == trans->set_id &&
+		    set->table == table &&
+		    nft_active_genmask(set, genmask))
+			return set;
 	}
 	return ERR_PTR(-ENOENT);
 }
@@ -10447,6 +10452,7 @@ static int nf_tables_commit(struct net *net, struct sk_buff *skb)
 				nft_flow_rule_destroy(nft_trans_flow_rule(trans));
 			break;
 		case NFT_MSG_NEWSET:
+			list_del(&nft_trans_container_set(trans)->list_trans_newset);
 			if (nft_trans_set_update(trans)) {
 				struct nft_set *set = nft_trans_set(trans);
 
@@ -10755,6 +10761,7 @@ static int __nf_tables_abort(struct net *net, enum nfnl_abort_action action)
 			nft_trans_destroy(trans);
 			break;
 		case NFT_MSG_NEWSET:
+			list_del(&nft_trans_container_set(trans)->list_trans_newset);
 			if (nft_trans_set_update(trans)) {
 				nft_trans_destroy(trans);
 				break;
@@ -10850,6 +10857,8 @@ static int __nf_tables_abort(struct net *net, enum nfnl_abort_action action)
 		}
 	}
 
+	WARN_ON_ONCE(!list_empty(&nft_net->commit_set_list));
+
 	nft_set_abort_update(&set_update_list);
 
 	synchronize_rcu();
@@ -11519,6 +11528,7 @@ static int __net_init nf_tables_init_net(struct net *net)
 
 	INIT_LIST_HEAD(&nft_net->tables);
 	INIT_LIST_HEAD(&nft_net->commit_list);
+	INIT_LIST_HEAD(&nft_net->commit_set_list);
 	INIT_LIST_HEAD(&nft_net->binding_list);
 	INIT_LIST_HEAD(&nft_net->module_list);
 	INIT_LIST_HEAD(&nft_net->notify_list);
@@ -11549,6 +11559,7 @@ static void __net_exit nf_tables_exit_net(struct net *net)
 	gc_seq = nft_gc_seq_begin(nft_net);
 
 	WARN_ON_ONCE(!list_empty(&nft_net->commit_list));
+	WARN_ON_ONCE(!list_empty(&nft_net->commit_set_list));
 
 	if (!list_empty(&nft_net->module_list))
 		nf_tables_module_autoload_cleanup(net);