netfilter: nft_ct: track register operations

Check if the destination register already contains the data that this ct
expression performs. This allows to skip this redundant operation. If
the destination contains a different selector, update the register
tracking information.

Export nft_expr_reduce_bitwise as a symbol since nft_ct might be
compiled as a module.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nft_bitwise.c

@@ -529,3 +529,4 @@ bool nft_expr_reduce_bitwise(struct nft_regs_track *track,
 
 	return false;
 }
+EXPORT_SYMBOL_GPL(nft_expr_reduce_bitwise);

net/netfilter/nft_ct.c

@@ -26,6 +26,7 @@
 struct nft_ct {
 	enum nft_ct_keys	key:8;
 	enum ip_conntrack_dir	dir:8;
+	u8			len;
 	union {
 		u8		dreg;
 		u8		sreg;
@@ -500,6 +501,7 @@ static int nft_ct_get_init(const struct nft_ctx *ctx,
 		}
 	}
 
+	priv->len = len;
 	err = nft_parse_register_store(ctx, tb[NFTA_CT_DREG], &priv->dreg, NULL,
 				       NFT_DATA_VALUE, len);
 	if (err < 0)
@@ -608,6 +610,7 @@ static int nft_ct_set_init(const struct nft_ctx *ctx,
 		}
 	}
 
+	priv->len = len;
 	err = nft_parse_register_load(tb[NFTA_CT_SREG], &priv->sreg, len);
 	if (err < 0)
 		goto err1;
@@ -677,6 +680,29 @@ static int nft_ct_get_dump(struct sk_buff *skb, const struct nft_expr *expr)
 	return -1;
 }
 
+static bool nft_ct_get_reduce(struct nft_regs_track *track,
+			      const struct nft_expr *expr)
+{
+	const struct nft_ct *priv = nft_expr_priv(expr);
+	const struct nft_ct *ct;
+
+	if (!nft_reg_track_cmp(track, expr, priv->dreg)) {
+		nft_reg_track_update(track, expr, priv->dreg, priv->len);
+		return false;
+	}
+
+	ct = nft_expr_priv(track->regs[priv->dreg].selector);
+	if (priv->key != ct->key) {
+		nft_reg_track_update(track, expr, priv->dreg, priv->len);
+		return false;
+	}
+
+	if (!track->regs[priv->dreg].bitwise)
+		return true;
+
+	return nft_expr_reduce_bitwise(track, expr);
+}
+
 static int nft_ct_set_dump(struct sk_buff *skb, const struct nft_expr *expr)
 {
 	const struct nft_ct *priv = nft_expr_priv(expr);
@@ -710,8 +736,27 @@ static const struct nft_expr_ops nft_ct_get_ops = {
 	.init		= nft_ct_get_init,
 	.destroy	= nft_ct_get_destroy,
 	.dump		= nft_ct_get_dump,
+	.reduce		= nft_ct_get_reduce,
 };
 
+static bool nft_ct_set_reduce(struct nft_regs_track *track,
+			      const struct nft_expr *expr)
+{
+	int i;
+
+	for (i = 0; i < NFT_REG32_NUM; i++) {
+		if (!track->regs[i].selector)
+			continue;
+
+		if (track->regs[i].selector->ops != &nft_ct_get_ops)
+			continue;
+
+		__nft_reg_track_cancel(track, i);
+	}
+
+	return false;
+}
+
 static const struct nft_expr_ops nft_ct_set_ops = {
 	.type		= &nft_ct_type,
 	.size		= NFT_EXPR_SIZE(sizeof(struct nft_ct)),
@@ -719,6 +764,7 @@ static const struct nft_expr_ops nft_ct_set_ops = {
 	.init		= nft_ct_set_init,
 	.destroy	= nft_ct_set_destroy,
 	.dump		= nft_ct_set_dump,
+	.reduce		= nft_ct_set_reduce,
 };
 
 #ifdef CONFIG_NF_CONNTRACK_ZONES
@@ -729,6 +775,7 @@ static const struct nft_expr_ops nft_ct_set_zone_ops = {
 	.init		= nft_ct_set_init,
 	.destroy	= nft_ct_set_destroy,
 	.dump		= nft_ct_set_dump,
+	.reduce		= nft_ct_set_reduce,
 };
 #endif