netfilter: nft_fib: add reduce support

The fib expression stores to a register, so we can't add empty stub.
Check that the register that is being written is in fact redundant.

In most cases, this is expected to cancel tracking as re-use is
unlikely.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

5 files changed, 48 insertions, 0 deletions

diff --git a/net/ipv4/netfilter/nft_fib_ipv4.c b/net/ipv4/netfilter/nft_fib_ipv4.c
index 03df986217b7..4151eb1262dd 100644
--- a/net/ipv4/netfilter/nft_fib_ipv4.c
+++ b/net/ipv4/netfilter/nft_fib_ipv4.c
@@ -152,6 +152,7 @@ static const struct nft_expr_ops nft_fib4_type_ops = {
 	.init		= nft_fib_init,
 	.dump		= nft_fib_dump,
 	.validate	= nft_fib_validate,
+	.reduce		= nft_fib_reduce,
 };
 
 static const struct nft_expr_ops nft_fib4_ops = {
@@ -161,6 +162,7 @@ static const struct nft_expr_ops nft_fib4_ops = {
 	.init		= nft_fib_init,
 	.dump		= nft_fib_dump,
 	.validate	= nft_fib_validate,
+	.reduce		= nft_fib_reduce,
 };
 
 static const struct nft_expr_ops *
diff --git a/net/ipv6/netfilter/nft_fib_ipv6.c b/net/ipv6/netfilter/nft_fib_ipv6.c
index 92f3235fa287..b3f163b40c2b 100644
--- a/net/ipv6/netfilter/nft_fib_ipv6.c
+++ b/net/ipv6/netfilter/nft_fib_ipv6.c
@@ -211,6 +211,7 @@ static const struct nft_expr_ops nft_fib6_type_ops = {
 	.init		= nft_fib_init,
 	.dump		= nft_fib_dump,
 	.validate	= nft_fib_validate,
+	.reduce		= nft_fib_reduce,
 };
 
 static const struct nft_expr_ops nft_fib6_ops = {
@@ -220,6 +221,7 @@ static const struct nft_expr_ops nft_fib6_ops = {
 	.init		= nft_fib_init,
 	.dump		= nft_fib_dump,
 	.validate	= nft_fib_validate,
+	.reduce		= nft_fib_reduce,
 };
 
 static const struct nft_expr_ops *
diff --git a/net/netfilter/nft_fib.c b/net/netfilter/nft_fib.c
index b10ce732b337..f198f2d9ef90 100644
--- a/net/netfilter/nft_fib.c
+++ b/net/netfilter/nft_fib.c
@@ -156,5 +156,47 @@ void nft_fib_store_result(void *reg, const struct nft_fib *priv,
 }
 EXPORT_SYMBOL_GPL(nft_fib_store_result);
 
+bool nft_fib_reduce(struct nft_regs_track *track,
+		    const struct nft_expr *expr)
+{
+	const struct nft_fib *priv = nft_expr_priv(expr);
+	unsigned int len = NFT_REG32_SIZE;
+	const struct nft_fib *fib;
+
+	switch (priv->result) {
+	case NFT_FIB_RESULT_OIF:
+		break;
+	case NFT_FIB_RESULT_OIFNAME:
+		if (priv->flags & NFTA_FIB_F_PRESENT)
+			len = NFT_REG32_SIZE;
+		else
+			len = IFNAMSIZ;
+		break;
+	case NFT_FIB_RESULT_ADDRTYPE:
+	     break;
+	default:
+		WARN_ON_ONCE(1);
+		break;
+	}
+
+	if (!nft_reg_track_cmp(track, expr, priv->dreg)) {
+		nft_reg_track_update(track, expr, priv->dreg, len);
+		return false;
+	}
+
+	fib = nft_expr_priv(track->regs[priv->dreg].selector);
+	if (priv->result != fib->result ||
+	    priv->flags != fib->flags) {
+		nft_reg_track_update(track, expr, priv->dreg, len);
+		return false;
+	}
+
+	if (!track->regs[priv->dreg].bitwise)
+		return true;
+
+	return false;
+}
+EXPORT_SYMBOL_GPL(nft_fib_reduce);
+
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Florian Westphal <fw@strlen.de>");
diff --git a/net/netfilter/nft_fib_inet.c b/net/netfilter/nft_fib_inet.c
index a88d44e163d1..666a3741d20b 100644
--- a/net/netfilter/nft_fib_inet.c
+++ b/net/netfilter/nft_fib_inet.c
@@ -49,6 +49,7 @@ static const struct nft_expr_ops nft_fib_inet_ops = {
 	.init		= nft_fib_init,
 	.dump		= nft_fib_dump,
 	.validate	= nft_fib_validate,
+	.reduce		= nft_fib_reduce,
 };
 
 static struct nft_expr_type nft_fib_inet_type __read_mostly = {
diff --git a/net/netfilter/nft_fib_netdev.c b/net/netfilter/nft_fib_netdev.c
index 3f3478abd845..9121ec64e918 100644
--- a/net/netfilter/nft_fib_netdev.c
+++ b/net/netfilter/nft_fib_netdev.c
@@ -58,6 +58,7 @@ static const struct nft_expr_ops nft_fib_netdev_ops = {
 	.init		= nft_fib_init,
 	.dump		= nft_fib_dump,
 	.validate	= nft_fib_validate,
+	.reduce		= nft_fib_reduce,
 };
 
 static struct nft_expr_type nft_fib_netdev_type __read_mostly = {