netfilter: nf_tables: do not reduce read-only expressions

Skip register tracking for expressions that perform read-only operations
on the registers. Define and use a cookie pointer NFT_REDUCE_READONLY to
avoid defining stubs for these expressions.

This patch re-enables register tracking which was disabled in ed5f85d4
("netfilter: nf_tables: disable register tracking"). Follow up patches
add remaining register tracking for existing expressions.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/netfilter/nf_tables.h

@@ -1633,4 +1633,12 @@ static inline struct nftables_pernet *nft_pernet(const struct net *net)
 	return net_generic(net, nf_tables_net_id);
 }
 
+#define __NFT_REDUCE_READONLY	1UL
+#define NFT_REDUCE_READONLY	(void *)__NFT_REDUCE_READONLY
+
+static inline bool nft_reduce_is_readonly(const struct nft_expr *expr)
+{
+	return expr->ops->reduce == NFT_REDUCE_READONLY;
+}
+
 #endif /* _NET_NF_TABLES_H */

net/bridge/netfilter/nft_reject_bridge.c

@@ -185,6 +185,7 @@ static const struct nft_expr_ops nft_reject_bridge_ops = {
 	.init		= nft_reject_init,
 	.dump		= nft_reject_dump,
 	.validate	= nft_reject_bridge_validate,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static struct nft_expr_type nft_reject_bridge_type __read_mostly = {

net/ipv4/netfilter/nft_dup_ipv4.c

@@ -75,6 +75,7 @@ static const struct nft_expr_ops nft_dup_ipv4_ops = {
 	.eval		= nft_dup_ipv4_eval,
 	.init		= nft_dup_ipv4_init,
 	.dump		= nft_dup_ipv4_dump,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static const struct nla_policy nft_dup_ipv4_policy[NFTA_DUP_MAX + 1] = {

net/ipv4/netfilter/nft_reject_ipv4.c

@@ -45,6 +45,7 @@ static const struct nft_expr_ops nft_reject_ipv4_ops = {
 	.init		= nft_reject_init,
 	.dump		= nft_reject_dump,
 	.validate	= nft_reject_validate,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static struct nft_expr_type nft_reject_ipv4_type __read_mostly = {

net/ipv6/netfilter/nft_dup_ipv6.c

@@ -73,6 +73,7 @@ static const struct nft_expr_ops nft_dup_ipv6_ops = {
 	.eval		= nft_dup_ipv6_eval,
 	.init		= nft_dup_ipv6_init,
 	.dump		= nft_dup_ipv6_dump,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static const struct nla_policy nft_dup_ipv6_policy[NFTA_DUP_MAX + 1] = {

net/ipv6/netfilter/nft_reject_ipv6.c

@@ -46,6 +46,7 @@ static const struct nft_expr_ops nft_reject_ipv6_ops = {
 	.init		= nft_reject_init,
 	.dump		= nft_reject_dump,
 	.validate	= nft_reject_validate,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static struct nft_expr_type nft_reject_ipv6_type __read_mostly = {

net/netfilter/nf_tables_api.c

@@ -8290,7 +8290,16 @@ EXPORT_SYMBOL_GPL(nf_tables_trans_destroy_flush_work);
 static bool nft_expr_reduce(struct nft_regs_track *track,
 			    const struct nft_expr *expr)
 {
-	return false;
+	if (!expr->ops->reduce) {
+		pr_warn_once("missing reduce for expression %s ",
+			     expr->ops->type->name);
+		return false;
+	}
+
+	if (nft_reduce_is_readonly(expr))
+		return false;
+
+	return expr->ops->reduce(track, expr);
 }
 
 static int nf_tables_commit_chain_prepare(struct net *net, struct nft_chain *chain)

net/netfilter/nft_cmp.c

@@ -193,6 +193,7 @@ static const struct nft_expr_ops nft_cmp_ops = {
 	.eval		= nft_cmp_eval,
 	.init		= nft_cmp_init,
 	.dump		= nft_cmp_dump,
+	.reduce		= NFT_REDUCE_READONLY,
 	.offload	= nft_cmp_offload,
 };
 
@@ -269,6 +270,7 @@ const struct nft_expr_ops nft_cmp_fast_ops = {
 	.eval		= NULL,	/* inlined */
 	.init		= nft_cmp_fast_init,
 	.dump		= nft_cmp_fast_dump,
+	.reduce		= NFT_REDUCE_READONLY,
 	.offload	= nft_cmp_fast_offload,
 };
 
@@ -359,6 +361,7 @@ const struct nft_expr_ops nft_cmp16_fast_ops = {
 	.eval		= NULL,	/* inlined */
 	.init		= nft_cmp16_fast_init,
 	.dump		= nft_cmp16_fast_dump,
+	.reduce		= NFT_REDUCE_READONLY,
 	.offload	= nft_cmp16_fast_offload,
 };
 

net/netfilter/nft_compat.c

@@ -871,6 +871,7 @@ nft_target_select_ops(const struct nft_ctx *ctx,
 	ops->dump = nft_target_dump;
 	ops->validate = nft_target_validate;
 	ops->data = target;
+	ops->reduce = NFT_REDUCE_READONLY;
 
 	if (family == NFPROTO_BRIDGE)
 		ops->eval = nft_target_eval_bridge;

net/netfilter/nft_connlimit.c

@@ -257,6 +257,7 @@ static const struct nft_expr_ops nft_connlimit_ops = {
 	.destroy_clone	= nft_connlimit_destroy_clone,
 	.dump		= nft_connlimit_dump,
 	.gc		= nft_connlimit_gc,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static struct nft_expr_type nft_connlimit_type __read_mostly = {

net/netfilter/nft_counter.c

@@ -293,6 +293,7 @@ static const struct nft_expr_ops nft_counter_ops = {
 	.destroy_clone	= nft_counter_destroy,
 	.dump		= nft_counter_dump,
 	.clone		= nft_counter_clone,
+	.reduce		= NFT_REDUCE_READONLY,
 	.offload	= nft_counter_offload,
 	.offload_stats	= nft_counter_offload_stats,
 };

net/netfilter/nft_ct.c

@@ -785,6 +785,7 @@ static const struct nft_expr_ops nft_notrack_ops = {
 	.type		= &nft_notrack_type,
 	.size		= NFT_EXPR_SIZE(0),
 	.eval		= nft_notrack_eval,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static struct nft_expr_type nft_notrack_type __read_mostly = {

net/netfilter/nft_dup_netdev.c

@@ -79,6 +79,7 @@ static const struct nft_expr_ops nft_dup_netdev_ops = {
 	.eval		= nft_dup_netdev_eval,
 	.init		= nft_dup_netdev_init,
 	.dump		= nft_dup_netdev_dump,
+	.reduce		= NFT_REDUCE_READONLY,
 	.offload	= nft_dup_netdev_offload,
 	.offload_action	= nft_dup_netdev_offload_action,
 };

net/netfilter/nft_dynset.c

@@ -413,6 +413,7 @@ static const struct nft_expr_ops nft_dynset_ops = {
 	.activate	= nft_dynset_activate,
 	.deactivate	= nft_dynset_deactivate,
 	.dump		= nft_dynset_dump,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 struct nft_expr_type nft_dynset_type __read_mostly = {

net/netfilter/nft_flow_offload.c

@@ -441,6 +441,7 @@ static const struct nft_expr_ops nft_flow_offload_ops = {
 	.destroy	= nft_flow_offload_destroy,
 	.validate	= nft_flow_offload_validate,
 	.dump		= nft_flow_offload_dump,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static struct nft_expr_type nft_flow_offload_type __read_mostly = {

net/netfilter/nft_fwd_netdev.c

@@ -217,6 +217,7 @@ static const struct nft_expr_ops nft_fwd_neigh_netdev_ops = {
 	.init		= nft_fwd_neigh_init,
 	.dump		= nft_fwd_neigh_dump,
 	.validate	= nft_fwd_validate,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static const struct nft_expr_ops nft_fwd_netdev_ops = {
@@ -226,6 +227,7 @@ static const struct nft_expr_ops nft_fwd_netdev_ops = {
 	.init		= nft_fwd_netdev_init,
 	.dump		= nft_fwd_netdev_dump,
 	.validate	= nft_fwd_validate,
+	.reduce		= NFT_REDUCE_READONLY,
 	.offload	= nft_fwd_netdev_offload,
 	.offload_action	= nft_fwd_netdev_offload_action,
 };

net/netfilter/nft_last.c

@@ -120,6 +120,7 @@ static const struct nft_expr_ops nft_last_ops = {
 	.destroy	= nft_last_destroy,
 	.clone		= nft_last_clone,
 	.dump		= nft_last_dump,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 struct nft_expr_type nft_last_type __read_mostly = {

net/netfilter/nft_limit.c

@@ -225,6 +225,7 @@ static const struct nft_expr_ops nft_limit_pkts_ops = {
 	.destroy	= nft_limit_pkts_destroy,
 	.clone		= nft_limit_pkts_clone,
 	.dump		= nft_limit_pkts_dump,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static void nft_limit_bytes_eval(const struct nft_expr *expr,
@@ -279,6 +280,7 @@ static const struct nft_expr_ops nft_limit_bytes_ops = {
 	.dump		= nft_limit_bytes_dump,
 	.clone		= nft_limit_bytes_clone,
 	.destroy	= nft_limit_bytes_destroy,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static const struct nft_expr_ops *

net/netfilter/nft_log.c

@@ -290,6 +290,7 @@ static const struct nft_expr_ops nft_log_ops = {
 	.init		= nft_log_init,
 	.destroy	= nft_log_destroy,
 	.dump		= nft_log_dump,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static struct nft_expr_type nft_log_type __read_mostly = {

net/netfilter/nft_masq.c

@@ -129,6 +129,7 @@ static const struct nft_expr_ops nft_masq_ipv4_ops = {
 	.destroy	= nft_masq_ipv4_destroy,
 	.dump		= nft_masq_dump,
 	.validate	= nft_masq_validate,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static struct nft_expr_type nft_masq_ipv4_type __read_mostly = {
@@ -175,6 +176,7 @@ static const struct nft_expr_ops nft_masq_ipv6_ops = {
 	.destroy	= nft_masq_ipv6_destroy,
 	.dump		= nft_masq_dump,
 	.validate	= nft_masq_validate,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static struct nft_expr_type nft_masq_ipv6_type __read_mostly = {
@@ -230,6 +232,7 @@ static const struct nft_expr_ops nft_masq_inet_ops = {
 	.destroy	= nft_masq_inet_destroy,
 	.dump		= nft_masq_dump,
 	.validate	= nft_masq_validate,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static struct nft_expr_type nft_masq_inet_type __read_mostly = {

net/netfilter/nft_nat.c

@@ -317,6 +317,7 @@ static const struct nft_expr_ops nft_nat_ops = {
 	.destroy        = nft_nat_destroy,
 	.dump           = nft_nat_dump,
 	.validate	= nft_nat_validate,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static struct nft_expr_type nft_nat_type __read_mostly = {
@@ -346,6 +347,7 @@ static const struct nft_expr_ops nft_nat_inet_ops = {
 	.destroy        = nft_nat_destroy,
 	.dump           = nft_nat_dump,
 	.validate	= nft_nat_validate,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static struct nft_expr_type nft_inet_nat_type __read_mostly = {

net/netfilter/nft_objref.c

@@ -91,6 +91,7 @@ static const struct nft_expr_ops nft_objref_ops = {
 	.activate	= nft_objref_activate,
 	.deactivate	= nft_objref_deactivate,
 	.dump		= nft_objref_dump,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 struct nft_objref_map {
@@ -204,6 +205,7 @@ static const struct nft_expr_ops nft_objref_map_ops = {
 	.deactivate	= nft_objref_map_deactivate,
 	.destroy	= nft_objref_map_destroy,
 	.dump		= nft_objref_map_dump,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static const struct nft_expr_ops *

net/netfilter/nft_queue.c

@@ -164,6 +164,7 @@ static const struct nft_expr_ops nft_queue_ops = {
 	.eval		= nft_queue_eval,
 	.init		= nft_queue_init,
 	.dump		= nft_queue_dump,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static const struct nft_expr_ops nft_queue_sreg_ops = {
@@ -172,6 +173,7 @@ static const struct nft_expr_ops nft_queue_sreg_ops = {
 	.eval		= nft_queue_sreg_eval,
 	.init		= nft_queue_sreg_init,
 	.dump		= nft_queue_sreg_dump,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static const struct nft_expr_ops *

net/netfilter/nft_quota.c

@@ -254,6 +254,7 @@ static const struct nft_expr_ops nft_quota_ops = {
 	.destroy	= nft_quota_destroy,
 	.clone		= nft_quota_clone,
 	.dump		= nft_quota_dump,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static struct nft_expr_type nft_quota_type __read_mostly = {

net/netfilter/nft_range.c

@@ -140,6 +140,7 @@ static const struct nft_expr_ops nft_range_ops = {
 	.eval		= nft_range_eval,
 	.init		= nft_range_init,
 	.dump		= nft_range_dump,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 struct nft_expr_type nft_range_type __read_mostly = {

net/netfilter/nft_redir.c

@@ -134,6 +134,7 @@ static const struct nft_expr_ops nft_redir_ipv4_ops = {
 	.destroy	= nft_redir_ipv4_destroy,
 	.dump		= nft_redir_dump,
 	.validate	= nft_redir_validate,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static struct nft_expr_type nft_redir_ipv4_type __read_mostly = {
@@ -183,6 +184,7 @@ static const struct nft_expr_ops nft_redir_ipv6_ops = {
 	.destroy	= nft_redir_ipv6_destroy,
 	.dump		= nft_redir_dump,
 	.validate	= nft_redir_validate,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static struct nft_expr_type nft_redir_ipv6_type __read_mostly = {
@@ -225,6 +227,7 @@ static const struct nft_expr_ops nft_redir_inet_ops = {
 	.destroy	= nft_redir_inet_destroy,
 	.dump		= nft_redir_dump,
 	.validate	= nft_redir_validate,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static struct nft_expr_type nft_redir_inet_type __read_mostly = {

net/netfilter/nft_reject_inet.c

@@ -80,6 +80,7 @@ static const struct nft_expr_ops nft_reject_inet_ops = {
 	.init		= nft_reject_init,
 	.dump		= nft_reject_dump,
 	.validate	= nft_reject_inet_validate,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static struct nft_expr_type nft_reject_inet_type __read_mostly = {

net/netfilter/nft_reject_netdev.c

@@ -159,6 +159,7 @@ static const struct nft_expr_ops nft_reject_netdev_ops = {
 	.init		= nft_reject_init,
 	.dump		= nft_reject_dump,
 	.validate	= nft_reject_netdev_validate,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static struct nft_expr_type nft_reject_netdev_type __read_mostly = {

net/netfilter/nft_rt.c

@@ -191,6 +191,7 @@ static const struct nft_expr_ops nft_rt_get_ops = {
 	.init		= nft_rt_get_init,
 	.dump		= nft_rt_get_dump,
 	.validate	= nft_rt_validate,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 struct nft_expr_type nft_rt_type __read_mostly = {

net/netfilter/nft_synproxy.c

@@ -288,6 +288,7 @@ static const struct nft_expr_ops nft_synproxy_ops = {
 	.dump		= nft_synproxy_dump,
 	.type		= &nft_synproxy_type,
 	.validate	= nft_synproxy_validate,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static struct nft_expr_type nft_synproxy_type __read_mostly = {

net/netfilter/nft_tproxy.c

@@ -320,6 +320,7 @@ static const struct nft_expr_ops nft_tproxy_ops = {
 	.init		= nft_tproxy_init,
 	.destroy	= nft_tproxy_destroy,
 	.dump		= nft_tproxy_dump,
+	.reduce		= NFT_REDUCE_READONLY,
 };
 
 static struct nft_expr_type nft_tproxy_type __read_mostly = {